Abstract: This research investigated on the tensile properties of Additive Manufacturing (AM) PolyEther Ether Ketone (PEEK) under different printing and post processing conditions, with a focus on providing insights for future fatigue tests. PEEK is a high-performance thermoplastic material with excellent mechanical properties that is widely used in many industries. In this study, the miniFactory Ultra 3D printer, based on Fused Filament Fabrication (FFF) technology, was used to fabricate PEEK specimens so as to assess the influence of printing parameters on the mechanical performances. Three key factors were considered: layer height, infill pattern and annealing as possible post-processing treatment. The variation of layer height and infill pattern aimed at evaluating their effects on the tensile properties, whereas annealing treatment was performed to assess the influence of residual stresses. The results indicated that infill pattern significantly affected the tensile properties, whereas annealing did not improve properties of specimens with triangular infill pattern. This research provides valuable insights for industries such as aerospace, automotive, and healthcare, where AM PEEK components are increasingly utilized.

Keywords: Design for AM | Experimental tests | Fused Filament Fabrication | PEEK

Abstract: Polyether Ether Ketone (PEEK) is a high-performance polymer widely used in several fields due to its excellent material and chemical strength properties also at high operating temperatures. The processing conditions used to fabricate PEEK parts can significantly influence the crystallinity and, hence, mechanical properties. Manufacturing difficulties are further amplified when PEEK is produced by Additive Manufacturing (AM), since it requires high processing temperatures, which only a few 3D printers available on the market can guarantee. In this paper, a Design of Experiment (DoE) was employed to investigate the mechanical properties of PEEK produced by Fused Filament Fabrication (FFF). Nozzle Temperature (390 ℃ and 420 ℃), Chamber Temperature (80 ℃ and 100 ℃) and Infill orientations (0° and 45°) were involved in the experiment through a 2-level full factorial DoE. Young’s modulus, Yield Stress, Ultimate Tensile Stress and elongation at fracture were investigated. Through ANOVA analysis it was found that the three parameters do not influence Young modulus (2.6 ÷ 3.2 GPa), while their combinations influence yield stress (36 ÷ 46 MPa), tensile strength (45 ÷ 74 MPa) and elongation at fracture (2.1 ÷ 16%). As expected, the optimal values for the best mechanical properties are the highest levels of nozzle and chamber temperatures and 0° infill orientation.

Keywords: Design for AM | Design of Experiment | Fused Filament Fabrication | PEEK | Tensile Test

Abstract: The current context is characterised by the speed of change in the technological sphere and in particular by the interconnection—to the point of overlaying—between physical and digital space. This stimulates consideration on the opportunities to explore the new frontiers of knowledge through advanced technologies and unprecedented cognitive-sensory perceptions, both from the user’s viewpoint and from that of the researcher. The chapter provides a critical-analytical reflection on accessibility and multisensory issues as fundamental tools for transferring multilevel knowledge between physical and digital. Based on this study, it proposes the configuration of immersive knowledge-sharing environments where cultural heritage and scientific research intersect, placing the user at the centre of experience. The augmented, multilevel fruition, the tracking within the multisensory environment of psycho-physiological and behavioural users’ data, together with the assessment of experience itself, have guided the design experimentations undertaken for the new layout of the Museum of Contemporary Mediterranean Ceramics in Cava de’ Tirreni. This was conceived as a multisensory and accessible phygital laboratory of inclusion and dialogue, a dynamic and adaptive space for sharing and experiencing knowledge.

Keywords: Accessibility | Immersive experience | Multilevel knowledge | Multisensory adaptive fruition | Phygital | Physical-digital relationship

Abstract: Variation Simulation (VS) allows early validation and certification of the assembly process before parts are built. State-of-the-art VS models of assembly systems with compliant sheet-metal parts are based on Finite Element Method (FEM) integrated with statistical approaches (i.e., Monte Carlo simulation). A critical technical barrier is the intense computational cost. This paper proposes a novel real-time physics-based VS model of assembly systems with compliant sheet-metal parts based on Reduced-Order Model (ROM). Compared to the literature on the topic, this study reports the first application of a ROM, developed for VS by using both intrusive and non-intrusive techniques. The capability of the proposed method is illustrated in a case study concerning the assembly process of the vertical stabiliser for commercial aircrafts. Results have shown that the accuracy of ROM (based on proper orthogonal decomposition) depends on the sampling strategy as well as on the number of reduced modes. Whilst a large CPU time reduction by several orders of magnitude is achievable by non-intrusive techniques (based on radial basis functions for interpolation), intrusive models provide more accurate results compared to the full-order models.

Keywords: Compliant assembly | Proper orthogonal decomposition | Radial basis functions | Real-time physics-based simulation | Reduced-Order Models | Sheet metals | Variation simulation analysis

Abstract: Over the years, high attention has been paid to Reverse Engineering (RE) as a methodological approach for reconstructing 3D models of existing objects to carry out analyses aimed to estimate accurate products performance and to conduct accurate inspections and quality controls. Although these techniques are widely used, RE has limitations related to both the user’s operations and the range of high-quality acquisition. Consequently, large objects exclude the possibility of preserving scanning accuracy, unless alternative solutions are found, and require high repeatability, making necessary well-trained personnel. For these purposes, Extended Reality (XR) could pave the way for the development of advanced training systems and the implementation of optimized interfaces for testing the adopted design solutions. This research deals with the development of an XR application for simulating the 3D scanning process of the vertical stabilizer torque box of an airplane and providing both an effective virtual training tool for the operators and a supporting tool for testing design solutions.

Keywords: 3D scanning | Extended Reality | Virtual training

Abstract: More than 60 years has passed since the installation of the first robot in an industrial context. Since then, industrial robotics has seen great advancements and, today, robots can collaborate with humans in executing a wide range of working activities. Nevertheless, the impact of robots on human operators has not been deeply investigated. To address this problem, we conducted an empirical study to measure the errors performed by two groups of people performing a working task through a virtual reality (VR) device. A sample of 78 engineering students participated in the experiments. The first group worked with a robot, sharing the same workplace, while the second group worked without the presence of a robot. The number of errors made by the participants was collected and analyzed. Although statistical results show that there are no significant differences between the two groups, qualitative analysis proves that the presence of the robot led to people paying more attention during the execution of the task, but to have a worse learning experience.

Keywords: empirical study | human error analysis | human–robot interaction | virtual reality

Abstract: Modern industries are experiencing radical changes due to the introduction of high technological innovations. In this context, even more highly complex and customized products are required, increasing the need of tending towards the concept of complexity for free. In addition, new products are conceived with the circular economy in mind, considering possible multi life-cycle at the early design stage to reduce time and costs while ensuring high quality standards. To evaluate the overall product complexity, this research combines geometrical, manufacturing, assembly, and disassembly complexity features, typically treated separately in the literature. The research is divided into two parts and proposes a novel methodological framework for assessing product complexity with an overall view, integrating many aspects of product life cycle. The framework aims to create a rank of product configurations, on the base of complexity. Making complexity assessment procedures objective is essential to effectively support decision-making processes, especially when introducing advanced manufacturing technologies such as Additive Manufacturing (AM). Additionally, it is necessary to know the complexity of the individual components before the overall assembly. This paper deals with the first part of the research, proposing the aforementioned novel methodological framework, with a great focus on geometrical complexity. A geometrical complexity index is defined through experimental and numerical surveys, involving CAD modeling experts and considering numerous metrics found in the technical literature. The proposed methodological framework and the geometrical complexity metric can provide useful tools for businesses looking to evaluate their product complexity and identify areas for improvement.

Keywords: CAD | Geometrical complexity | Methodological framework | Product complexity | Survey

Abstract: The recent improvement of additive manufacturing (AM) technologies has been attracting the industry and research community attention. This paper aims to investigate the influence of building position and printing scheme on the tensile mechanical properties of Tough polylactic acid (PLA) material, manufactured through a fused deposition modeling (FDM) 3D printing – the S5 ProBundle Ultimaker. FDM 3D printing, also known as fused filament fabrication (FFF), is an AM process within the realm of material extrusion. FDM builds parts Layer by Layer by selectively depositing melted material in a predetermined path, and uses thermoplastic polymers that come in the form of filaments. In this paper, AM Tough PLA specimens are manufactured according to ASTM-D638 requirement considering two different positions on the building plate and two printing schemes. Specimens are tested under static tensile test and the mechanical properties are extracted.

Keywords: additive manufacturing | fused filament fabrication | material characterization | PLA Tough

Abstract: 3D printing, including the widely used technique of Fused Filament Fabrication (FFF), offers several benefits, such as freedom in design, faster production times, customization, and lightweight. In fact, it has the potential to serve a variety of sectors, from the everyday products market to the industry. However, the properties of FFF parts, in terms of mechanical strength and geometrical accuracy, are strongly influenced by printing process parameters, necessitating thorough investigations. This preliminary study proposes a comparison between data-driven Machine Learning (ML) models, i.e. Quadratic Regression (QR), Regression Tree (RT), and Neural Network (NN), to predict the impact of printing process parameters on both mechanical (tensile properties) and aesthetical (bending angle, thickness, and flatness tolerance) behavior of additively manufactured tough-Polylactic Acid (PLA) specimens. The investigated models were trained by using experimental data obtained from Design of Experiment (DoE) where the building orientation on plate, the infill percentage and the pattern were varied. An additional dataset was used to test the accuracy of the prediction. The results suggest that ML models perform well in predicting the tensile properties, particularly the Ultimate Tensile Stress (UTS). At the same time, further investigation is necessary to improve the prediction for aesthetical features.

Keywords: 3D measurements | Additive Manufacturing | Design for AM | experimentation | Machine Learning | Mechanical behavior | predictive model

Abstract: The peak stress method (PSM) allows a rapid application of the notch stress intensity factor (NSIF) approach to the fatigue life assessment of welded structures, by employing the linear elastic peak stresses evaluated by FE analyses with coarse meshes. Because of the widespread adoption of 3D modeling of large and complex structures in the industry, the PSM has recently been boosted by including four-node and ten-node tetrahedral elements of Ansys FE software, which allows to discretize complex geometries. In this paper, a Round Robin among eleven Italian Universities has been performed to calibrate the PSM with seven different commercial FE software packages. Several 3D mode I, II and III problems have been considered to investigate the influence of (i) FE code, (ii) element type, (iii) mesh pattern, and (iv) procedure to extrapolate stresses at FE nodes. The majority of the adopted FE software packages present similar values of the PSM parameters, the main source of discrepancy being the stress extrapolation method at FE nodes.

Keywords: coarse mesh | FE analysis | notch stress intensity factor (NSIF) | peak stress method (PSM) | tetrahedral element

Abstract: Emerging production technologies, in particular Additive Manufacturing (AM), nowadays are extremely suitable for creating highly complex products, tending towards the concept of ‘complexity for free’, which is often associated with AM. However, there are no adequate guidelines to provide decision support for the correct selection of the most economically appropriate technology. Indeed, from literature it has been highlighted the need to develop a technology selection methodology based no longer on production volume but on product complexity. This paper investigates this need by presenting an approach to determine the geometrical (or shape) complexity index of a part, which, combined with the assembly complexity, represents the driver for helping to decide the best production technology (traditional or additive). The geometrical complexity index has been determined based on complexity judgments, provided by CAD modelling experts, for a sample of CAD models. In this way, it has been possible to define a preliminary complexity index model, strictly linked to the CAD model information. The results showed that the geometrical complexity metrics from the literature, if individually considered, are not comprehensive. However, a combination of them makes it possible to obtain an index that best reflects the subjective judgement of the experts. In addition, by combining the geometrical and assembly complexity with a cost analysis it is possible to obtain convenience zones for better selecting the production technology.

Keywords: CAD | Geometrical complexity | Survey | Technology selection

Abstract: This paper deals with the development of a Finite Element (FE) model for the simulation of a two-passes V-groove butt weld joint. Specifically, in order to reduce the computational costs and the efforts aimed to the numerical evaluation of residual stresses distribution in welded joints, a sensitivity analysis has been performed to quantify the level of accuracy provided by the model when the strict dependence of some material properties on the temperature is neglected. Before proceeding with the sensitivity analysis, the reliability of the proposed FE model was assessed against an experimental test; a good agreement between numerical and experiment results has been achieved. In detail, the material properties involved in this sensitivity analysis are: thermal conductivity, specific heat, Young's modulus and thermal expansion coefficient; the investigated outputs are: temperatures, residual stresses, displacements and angular distortion. Several test cases have been simulated by considering all of these material properties as constant, one at a time or all together. The results analysis showed that the levels of accuracy provided by the different simplifications depend on the selected output. Among the most relevant results, it has been found out that the predicted temperatures distributions are not significantly influenced by the considered material simplifications. The effects on the residual stresses in considering the thermal conductivity and the specific heat as constant are negligible. The hypothesis of a constant thermal expansion coefficient provides an acceptable level of accuracy only in proximity of the weld seam. Finally, concerning the displacements field and the angular distortion of the welded plates, by considering the thermal conductivity and Young's modulus as constant, the effectiveness of the model appears to be compromised.

Keywords: Finite element method | Material properties | Residual stresses | Structural steel | Welded joint

Abstract: The protection of artistic and cultural heritage is a major challenge due to its peculiarities and its exposure to significant natural hazards. Several methodologies exist to assess the condition of artistic heritage and to protect it from exceptional actions. Moreover, novel digital technologies offer many solutions able to deliver a digital replica of artifacts of interest, so that a reduction in the uncertainties in the analysis models can be achieved. A rational approach to the preservation and protection of artistic heritage is based on traditional approaches supported and integrated by novel technologies, so that qualitative and quantitative indicators of the current condition of artistic heritage can be defined and validated in an interdisciplinary framework. The present paper reports the results of an approach to the maintenance and preservation of art objects housed in a museum complex based on a comprehensive digital path towards a Historical Digital Twin (HDT). A workflow aimed at estimating the stress regime and the dynamic properties of two sculptures, based on the detailed three-dimensional model resulting from a laser scanner survey, is illustrated and dis-cussed. The results highlight the great advantages resulting from the integration of traditional and novel procedures in the field of conservation of artistic assets.

Keywords: 3D simulation | Conservation | Cultural heritage | Digital twin | Laser scanning | Maintenance

Abstract: Residual stresses induced by the welding processes may, in some cases, result in significant warping and distortions that can endanger the integrity of the welded structures. This document reports an investigation of the welding process to make a dissimilar T‐joint through an advanced Finite Element (FE) modelling and a dedicated laboratory test. The T‐joint consisted of two plates of dissimilar materials, AISI304 and S275JR steels, both having a thickness of 5 mm, welded through a Shielded Metal Arc Welding (SMAW). Thermocouples were used to acquire the temperature variations during welding. In parallel, an FE model was built and the welding process was simulated through the “element birth and death” technique. Numerical and experimental outcomes were compared in terms of temperature distributions during welding and in terms of distortion at the end of the final cooling, showing that the FE model was able to provide a high level of accuracy.

Keywords: Dissimilar materials | Distortions | Element birth and death | Finite element method (FEM) | Residual stresses | Shielded metal arc welding (SMAW) | Simulation | T‐joint

Abstract: Currently, there is a growing interest of industries in applying additive manufacturing (AM) technology for generating objects with high geometrical complexity and low weight, ensuring good performance, comparable to those ones of products realized by means of traditional techniques. Anyway, it is still usual to realize AM products without focusing on the morphology of the object, hence without exploiting all the advantages of the technique. Indeed, since the several suitable AM technologies, it should be useful to know the functional characteristics of the component for the best choice of the appropriate one and its constructive complexity. In this regard, the 3D modeling strategy is extremely crucial for a proper realization of AM products. The paper deals with a study of the geometrical complexity of dashboard components of a car, based on several techniques for evaluating the geometric complexity. The latter is a fundamental element for estimating the feasibility of AM in terms of production costs and the benefits with respect to traditional molding. In detail, the study focuses on comparing several geometrical complexity evaluation techniques in order to identify the one that simplifies the calculation and better approximates the most used in literature.

Keywords: additive manufacturing | CAD | geometrical complexity

Abstract: Background: In this study, we promote a global approach to occupational risk perception in order to improve occupational health and safety training programs. The study investigates the occupational risk perception of operating room healthcare workers using an Analytic Hierarchy Process approach. Methods: A pilot study was carried out through a cross-sectional survey in a university hospital in Southern Italy. An ad hoc questionnaire was administered to enrolled medical post-graduate students working in the operating room. Results: Fifty medical specialists from seven fields (anaesthetists, digestive system surgeons, general surgeons, maxillofacial surgeons, thoracic surgeons, urologists, and gynaecologists) were questioned about perceived occupational risk by themselves. Biological, ionizing radiation, and chemical risks were the most commonly perceived in order of priority (w = 0.300, 0.219, 0.210). Concerning the biological risk, gynaecologists unexpected perceived this risk as less critical (w = 0.2820) than anaesthesiologists (w = 0.3354), which have the lowest perception of the risk of ionizing radiation (w = 0.1657). Conclusions: Prioritization methods could improve risk perception in healthcare settings and help detect training needs and perform sustainable training programs.

Keywords: Analytic hierarchy process | Healthcare workers | Occupational risk perception | Prioritization risk methodology

Abstract: This paper presents a novel numerical model, based on the finite element (FE) method, for the simulation of a welding process aimed to make a two-pass V-groove butt joint, paying attention on the prediction of residual stresses and distortions. The ‘element birth and death’ technique for the simulation of the weld filler supply has been considered within this paper. The main advancements with respect to the state of the art herein proposed concern: (i) the development of a modelling technique able to simulate the plates interaction during the welding operation when an only plate is modelled. This phenomenon is usually neglected in literature; (ii) the heat amount is supplied to the FEs as volumetric generation of the internal energy, allowing overcoming the time-consuming calibration phase needed to use the Goldak's model, commonly adopted in literature. Predicted results showed a good agreement with experimental ones.

Keywords: butt weld joint | element ‘birth and death’ technique | FEM | residual stress | welding

Abstract: Within the era of smart factories, concerning the ergonomics related to production processes, the Digital Twin (DT) is the key to set up novel models for monitoring the performance of manual work activities, which are able to provide results in near real time and to support the decision-making process for improving the working conditions. This paper aims to propose a methodological framework that, by implementing a human DT, and supports the monitoring and the decision making regarding the ergonomics performances of manual production lines. A case study, carried out in a laboratory, is presented for demonstrating the applicability and the effectiveness of the proposed framework. The results show how it is possible to identify the operational issues of a manual workstation and how it is possible to propose and test improving solutions.

Keywords: Digital Twin | Ergonomics | Manufacturing | Production process

Abstract: In current industrial systems, automation is a very important aspect for assessing manufacturing production performance related to working times, accuracy of operations and quality. In particular, the introduction of a robotic system in the working area should guarantee some improvements, such as risks reduction for human operators, better quality results and a speed increase for production processes. In this context, human action remains still necessary to carry out part of the subtasks, as in the case of composites assembly processes. This study aims at presenting a case study regarding the reorganization of the working activity carried out in workstation in which a composite fuselage panel is assembled in order to demonstrate, by means of simulation tool, that some of the advantages previously listed can be achieved also in aerospace industry. In particular, an entire working process for composite fuselage panel assembling will be simulated and analyzed in order to demonstrate and verify the applicability and effectiveness of human-robot interaction (HRI), focusing on working times and ergonomics and respecting the constraints imposed by standards ISO 10218 and ISO TS 15066. Results show the effectiveness of HRI both in terms of assembly performance, by reducing working times and ergonomics-for which the simulation provides a very low risk index.

Keywords: Aerospace production | Ergonomics | Human-robot interaction | Simulation

Abstract: This research deals with the fatigue behavior of 200 small single lap multiple-riveted joint specimens, widely used for aeronautic structures. The tests were performed with three different levels of stress with stress ratio R = 0.05; three levels were set: 90 MPa, 120 MPa and 160 MPa. The fatigue life and critical crack size for all tested specimens were analyzed. According to the results' analysis, two types of fracture, through-hole and in proximity of the hole, were observed, depending on the level of stress: the higher the applied stress, the more through-hole cracking. Indeed, under the fatigue load with a stress level of 90 MPa, less than 30% of specimens showed cracks propagating through the hole, while, at the stress level of 120 MPa, the percentage reaches 36.3%. At the stress level of 160 MPa, 100% of specimens failed through the hole. Moreover, aimed to use experimental data for probabilistic methods, a statistical analysis was performed according to the Anderson-Darling test. This method allowed the analysis of the datasets, in terms of both fatigue life and critical crack size, providing information about the best distribution function able to fit experimental results.

Keywords: Fatigue | Probabilistic method | Riveted joints

Abstract: In the era of Industry 4.0, automation plays a key role in improving manufacturing production processes in terms of working times, accuracy of operations, products’ quality, and so on. With focus on the working tasks on composite components, drilling and riveting operations require particular attention due to the possibility of damage to the final product, especially when they are executed manually. To reduce these kinds of risks, the introduction of a robot in the working area could represent an improvement to speed up the processes and to ensure a better quality result. It is worth noting that human intervention remains necessary for carrying out a part of the sub-tasks, especially in the case of composite assembly procedures. This paper aims at presenting a case study about the drilling and riveting operations on a composite aircraft fuselage whose working cell is characterized by the coexistence of a human and a robot. Moreover, the implementation of a numerical simulation allows validating the working cycle and the adopted solutions in terms of ergonomic performance.

Keywords: aircraft fuselage assembly | composite manufacturing | ergonomics | human–robot interaction | simulation

Abstract: In the era of Industry 4.0, several advantages for industries come by the implementation of new technologies that play a key role for improving production processes, focusing on working times, product quality, accuracy of operations and other important parameters of the production systems. In order to evaluate these parameters, simulation may be used as a tool to verify (i) the improvement adopted on existing production lines or (ii) the design solutions adopted for a new line, optimizing the processes. The aim of this paper is to investigate the possibility to assess the before said parameters in a specific case study by implementing a Discrete Event Simulation (DES). The study concerns two consecutive workplaces of an automotive assembly line in which three workers are involved in assembly activities. The results demonstrated that the Digital Manufacturing (DM) approach and simulation may be used for verifying the performances of the line, thanks to the evaluation of important parameters, such as the Overall Equipment Effectiveness (OEE).

Keywords: Overall Equipment Effectiveness | Simulation | Work measurement

Abstract: Composite materials are increasingly used in those fields where it is necessary to achieve the requirements of lightweight and high mechanical properties. Even though their high specific strength which get these materials very attractive, especially for the transport field, there are several critical issues that still limit their application in primary structures. Among these, dynamic loading conditions play a critical role because they can significantly lower their residual strength. This paper aims to investigate experimentally the structural response of a 25 mm thick Omega composite structure under different impact loading conditions. The investigated test article consists of E-glass fibres (40% volume fraction) reinforced polyester matrix. The structure is covered by a HELIOPOL 1401 M AGC W 11 gelcoat layer and it has been impacted through a drop mass of 3.94 kg, dropped from heights of 50 mm, 75 mm, 100 mm, 150 mm, 200 mm, 250 mm, 350 mm and 500 mm.

Keywords: Composite | Fibreglass | Impact behaviour | Mechanical testing

Abstract: The optimization of production processes has always been one of the cornerstones for manufacturing companies, aimed to increase their productivity, minimizing the related costs. In the Industry 4.0 era, some innovative technologies, perceived as far away until a few years ago, have become reachable by everyone. The massive introduction of these technologies directly in the factories allows interconnecting the resources (machines and humans) and the entire production chain to be kept under control, thanks to the collection and the analyses of real production data, supporting the decision making process. This article aims to propose a methodological framework that, thanks to the use of Industrial Internet of Things—IoT devices, in particular the wearable sensors, and simulation tools, supports the analyses of production line performance parameters, by considering both experimental and numerical data, allowing a continuous monitoring of the line balancing and performance at varying of the production demand. A case study, regarding a manual task of a real manufacturing production line, is presented to demonstrate the applicability and the effectiveness of the proposed procedure.

Keywords: Internet of Things—IoT | Methodological framework | Production line performance | Simulation | Wearable devices

Abstract: This paper deals with the experimental and numerical investigations of the structural behaviour of a rolling stock's seats system under static and fatigue loading conditions, aimed to assess the reliability of some multiaxial fatigue failure criteria implemented in the FE model. According to the NF F31–119 standard, a specific full-scale multiaxial testing machine has been used for the fatigue test. During the test, a visual inspection approach with a detection interval of 3·105 cycles has been adopted. After 1.2·106 cycles the test has been stopped and a Liquid Penetrant Inspection (LPI) has been carried out in order to detect accurately cracks nucleation and propagation. Moreover, numerical analyses, based on the Finite Elements (FE) Method, have been performed on the EN-AW 6060 T5 aluminium alloy structure of a rolling stock's seats to predict the most affected zones where the cracks nucleation may occur under multiaxial fatigue loads. Since the in-service applied loads belong to Multiaxial High-Cycle Fatigue (MHCF) load class, Sines, Crossland and Dang Van criteria have been used to post-process the predicted results achieved by the FE analyses. For validation purpose, numerical and experimental results have been compared. According to the numerical-experimental results comparison, Dang Van criterion provided the best level of accuracy.

Keywords: Fatigue assessment | Fatigue testing | Finite element analysis | High cycle fatigue | Railway engineering

Abstract: Biomechanical overload is a critical issue for the health of workers employed in manufacturing production systems, and so far it has been analysed by applying conventional observational methods. This research aims to introduce a procedure for quantitative biomechanical overload risk assessment in which surface electromyography integrates with a motion capture system, enhancing the use of Internet of Things (IoT) devices directly in the factory. A case study concerning an experimental session in a Fiat Chrysler Automobiles (FCA) assembly line is described in order to demonstrate how these devices, worn in actual working conditions, can be integrated to provide reliable data, despite possible influences of electromagnetic noise in the measures.

Keywords: biomechanical overload | IMU | IoT | manufacturing | risk assessment | surface electromyography

Abstract: A critical point for manufacturing companies has always been the optimization of their production processes to increase the productivity and minimize the related costs, chasing an efficiency principle. Thanks to advent of Industry 4.0 (I4.0) era, some technologies, perceived as far away few years ago, now can be reached by everyone. The use of these technologies allows factories to acquire and evaluate their production data (and much more) and carry out complex analyses in short time making possible the improvement of the production processes. Aim of this paper is to propose a methodological framework in which, starting from an existing process, where workers and machines have already been assigned to each station of a production line, the use of Industrial Internet of Things (IIoT) devices, such as wearable ones, allows to carry out analyses of the performance parameters of the production lines by means of an event-based simulation. In this way it is possible to evaluate if improvements are possible by re-balancing or re-scheduling the line. A case study, regarding a manual task of a real manufacturing production line, is presented to demonstrate the applicability and the effectiveness of the described framework.

Keywords: Internet of Things | Line balancing | Methodological framework | Wearable devices

Abstract: During recent years, industrial world faced transformations that led companies to introduce the concepts and the technologies of a new industrial paradigm, named Industry 4.0 (I4.0), in order to improve their products and their production processes. In the context of I4.0, factories are becoming smart, more flexible and collaborative, satisfying the current demands of increasingly competitive markets and of products closer to the real needs of customers. Within this framework, the approach to product and process design is changing too, supported by the use of complex numerical analyses for testing and validating the performance of both products and production processes. This is made possible thanks to the Digital Manufacturing (DM) approach, that allows to reduce the design times and to validate the design solution in virtual environments, without setting up detailed and expensive experimental sessions. This paper aims to propose a possible methodological framework to better carry out the design of new products and production systems, according to the DM principles.

Keywords: Digital Manufacturing | Product design | Production process design | Simulation

Abstract: Recently, human-centered design has become one of the most promising approaches for improving the entire production process design. During the design phase, among the main important aspects to investigate, ergonomic performance of the workplace (WP) plays a key role. It is well known that design errors can lead to significant delays in the design and engineering of a production process, especially when it is related to a complex system such as the assembly line of an automotive industry. Prediction of the ergonomic performance, which is often coarsely considered during the design phase, can represent a fundamental step in preventing ergonomic issues since the early design phase of a production process, avoiding also negative consequences on line balancing. Based on a concurrent engineering (CE) approach, the aim of this paper is to present a framework that uses digital twins of stations in order to minimise the time necessary to develop and design a new assembly line. The application of this procedure will allow avoiding the possibility of realising a line that reveals ergonomic problems and correcting design errors during the design phase and not just during the production phase. In this way, it is possible to achieve great advantages in terms of cost avoidance for the correction of the design errors and in terms of time to market, which will be significantly reduced. A digital twin of a real station of a Fiat Chrysler Automobiles (FCA) assembly line is presented to validate the numerical procedure and the design approach proposed in this paper. Finally, numerical results, regarding the evaluation of an ergonomic index, were compared with experimental ones achieved by analysing data collected during an experimental session.

Keywords: Digital twin | Ergonomics | Human-centered design | Managerial methodological framework | Simulation

Abstract: In a bolted joint, the preload level resulting from the tightening torque represents a very important parameter governing the stresses distributions involving the joint under the real loading conditions. This paper deals with the development of a Finite Element (FE) model for the investigation of the effects of some selected preload levels on the stress-strain states affecting both bolt and plate in a single lap joint. The aim of this FE model is to support the design phase of strain gauges instrumented bolt to evaluate experimentally the rate of tensile load applied to the joint that the bolt absorbs with different preloads. The test article consists of two steel plates, a steel bolt and an aluminum nut. The results herein presented showed firstly that, without bolt preload, the tensile load applied to the joint is completely transferred to the bolt and that the load transferred to the bolt almost linearly decreases as the preload increases. Moreover, at a selected preload level, the transversal and longitudinal stresses (with respect to the load direction) increase as the tensile load increases, while the stress along the plate thickness direction decreases, reaching negative values. On the other hand, at a selected tensile load level, the transversal and longitudinal stresses as well as the stress along the thickness direction decrease as the preload level increases. Predicting the mechanical behaviour of the only bolted joint, if the same bolt model will be used to simulate the mechanical behaviour in a hybrid single-lap joint, possible imperfections of the model will have to certainly be linked to the modelling of the adhesive.

Keywords: Bolted joints | Numerical modeling | Tightening torque

Abstract: This study used the Finite Element (FE) method to numerically analyze the thermo-mechanical behavior and residual stresses in dissimilar welded T-joints. Residual stresses induced by the fusion arc-welding of steel joints in power generation plants are a concern to the industry. The structural integrity assessment of welded structures requires the consideration of weld-induced residual stresses for the safe operations in power plants, which may be compromised by their presence. Details on the used thermo-mechanical FE model and the results analysis are herein presented.

Keywords: Finete Element Method | Residual Stresses | T-Joint | Welding

Abstract: OBJECTIVE: To estimate the three-year cumulative risk of work-related upper limb disorders (WRULDs) in a cohort of automotive industry workers and to provide a first test of the ability of the European Assembly Worksheet (EAWS) methodology to predict WRULDs. METHODS: 292 workers were investigated by reviewing workers' medical records during the period from 2012-2015 to determine their exposure to biomechanical overload according to EAWS risk scores (0-25, low risk, Green zone; 26-50, medium risk, Yellow zone; >50, High risk; Red zone). RESULTS: The risks were 0.83%, 5.71%, and 11.88% for the Control (unexposed), Green and Yellow Groups, respectively. Only the comparison between the Yellow/Control Groups was significant (p = 0.0014). In total, we observed 17 cases of musculoskeletal disorders (MSDs) (14 symptomatic and 3 cases detected by physical examination). CONCLUSIONS: The EAWS is a useful tool for the preliminary risk assessments of biomechanical overload among automotive industry workers. The finding of mainly non-specific disorders highly suggests that health surveillance should aim to identify not only full-blown diseases but also symptomatic cases.

Keywords: biomechanical overload | EAWS (European Assembly Worksheet) | Musculoskeletal disorders

Abstract: According to the international literature postures, exerted forces, manual handling and repetitive actions with upper limbs must be considered in order to estimate the workers’ exposure to biomechanical overload risk, but also a preventive ergonomic approach in the design phase is possible. Within the Industry 4.0, the digitalisation of manufacturing processes generate benefits in terms of production costs and time. Regarding the ergonomics, it is possible to set up a predictive model for the evaluation of biomechanical overload risk. This paper proposes an appraisal of a workplace design and ergonomics validation procedure based on simulation: data from assembly tasks simulation of Digital Human Models (DHM) can be used to assess the ergonomic indexes (OWAS, NIOSH, OCRA, EAWS, etc.). So, it is possible to preventively solve ergonomic risks during the design phase. A test case, regarding a real workplace of an assembly line of an important automotive Company, is also presented.

Keywords: human-centred design | industrial ergonomics | simulation | Workplace design

Abstract: Automation plays a key role in the realisation of the Factory 4.0 and technological research, combined with the use of innovative materials, contributes to the improvement of products in terms of functional, technical and production quality. Within this context, the so-called Digital Twin allows to reproduce the real behaviour of a production system in a virtual environment, giving the possibility to numerically perform the desired analysis. Human-robot interaction (HRI) is increasing in those workplaces where the manual activity is not safe nor efficient in terms of performance (e.g. cycle time) and it is characterised by several levels of interaction (cooperation, collaboration and coexistence). The aim of this paper is to propose a numerical procedure that, based on the simulation, allows verifying the process feasibility, validating the interaction between human and robot and programming the logic controller to be implemented on the real robot. A case study about assembling of composite components of an aircraft fuselage panel is proposed. The use of the robot allows to speed up the processes of drilling and sealing, leaving to human less dangerous operations.

Keywords: Composite Assembly | Digital Twin | Robot | Simulation

Abstract: Since the early development for health purposes in 1950s, motion tracking systems have been strongly developed for several applications. Nowadays, using Micro Electro-Mechanics Systems (MEMS) technologies, these systems have become compact and light, being popular for several applications. Looking at the manufacturing industry, such as the automotive one, ergonomic postural analyses are a key step in the workplaces design and motion tracking systems represent fundamental tools to provide data about postures of workers while carrying out working tasks, in order to assess the critical issues according to ISO 11226 standard. The aim of this work is to present an experimental wearable inertial motion tracking system, developed at the Dept. of Engineering of the University of Campania “Luigi Vanvitelli” in collaboration with Linup S.r.l., composed by several low-cost inertial measurement units (IMU). The system allows to estimate the orientation of selected human body segments and to analyze the postures assumed during the working tasks. To increase the flexibility of use, the system is highly modular: it’s composed by 4 independent modules in full-body configuration, each one made of 3 or 4 inertial units. In this paper, the overall system is presented, supported by several test cases, carried out in Fiat Chrysler Automobile (FCA) assembly lines, to test the system reliability in industrial environments. Furthermore, an automatic posture analysis code is presented to evaluate the postural critical issue of the workplaces.

Keywords: Industrial environment | Inertial measurement unit | Wearable devices | Working postures

Abstract: Among the technologies included in Industry 4.0, the fourth industrial revolution, Digital Manufacturing (DM) represents a new approach to evaluate the performance of production processes in a virtual environment. DM can be seen as the industrial declination of Virtual Reality (VR) that, by using an integrated computer-based system, allows creating simulation, 3D visualization and provides different tools to define the product and the manufacturing process simultaneously. Virtualization and simulation of production processes generate benefits for companies in terms of time and costs, optimizing the assembly line and providing parameters for studying human-machine interaction. Regarding this last topic, the aim of this paper is to propose an innovative procedure to support the workplaces design, based on simulation techniques that allow setting a virtual scenario in which a Digital Human Model (DHM) is able to carry on assembly tasks. Data from simulations can be analyzed and used to assess ergonomic indexes in a preventive and proactive approach. As other automotive manufacturers, Fiat Chrysler Automobiles (FCA) applies EAWS (European Assessment Work Sheet), a first level screening, to assess the ergonomic biomechanical overload of workplaces in the design phase, according to international standards (ISO 11226 and ISO 11228-1, -2, -3). The ergonomics risk assessment, since the design phase, allows identifying critical issues and to define and put in practice corrective actions in the earlier phase, being more successful and less expensive. In order to support the procedure proposed in this research, a case study is described, based on the EAWS index evaluation of a workstation in a FCA plant assembly shop. The simulation has been realized by using PLM software Tecnomatix Process Simulate by Siemens® and the EAWS analysis has been performed by using EAWSdigital by MTM®. The procedure can be considered innovative to support human-centered design of production process in developing new products.

Keywords: Digital human models | Digital manufacturing | EAWS | Simulation

Abstract: Biomechanical overload represents one of the main risks in the industrial environment and the main possible source of musculoskeletal disorders and diseases. The aim of the this study is to introduce new technologies for quantitative risk assessment of biomechanical overload, by integrating surface electromyography (sEMG) with an innovative motion-capture system based on inertial measurement units (IMU). The case study was carried out in collaboration with Fiat Chrysler Automobiles Italy S.p.A. and deals with the analysis of the “central tunnel cabinet assembly” activity, performed by two workers of assembly lines during a working task, which lasts about one minute. The electromyography signals were acquired bilaterally, in three different body regions on the right and on the left side of the Erector Spinae, during standard working activities; the progression of trunk postures (flexion-extension, lateral flexion and twisting) was tracked by using an inertial motion-capture system made of wearable inertial sensors, to evaluate the alignment of the major body segments, using a developed algorithm. Data analysis showed kinematic and muscular activity patterns consistent with the expected ones. In particular, data show that the proposed technologies can be integrated and simultaneously used during workers’ real performing activities. Data quality also demonstrates that both types of sensors, EMG electrodes and IMU, not influenced each other, neither by electromagnetic noise usually present in an industrial environment. The results of this study show feasibility and usefulness of the integration of kinematic and electromyography technologies for assessing the biomechanical overload in production lines.

Keywords: Biomechanical overload | Inertial sensors | Surface electromyography

Abstract: Biomechanical overload is one of the main risk factors for musculoskeletal disorders among manufacturing workers and so far, it has been evaluated with observational methods. The aim of this research was to introduce a procedure for quantitative biomechanical overload risk assessment in which surface electromyography integrates with a motion capture system. The paper deals with actual test cases performed in an automotive company, using surface electromyography and a homemade inertial motion capture system. The quality of the data produced by it demonstrates that these devices can be integrated, worn in actual working conditions and are not influenced by electromagnetic interference.

Keywords: Biomechanical load | IMU | Industrial ergonomics | sEMG | Wearable devices

Abstract: The study of human factors is fundamental for the human-centered design of Smart Workplaces. IIoT (Industrial Internet of Things) technologies, mainly wearable devices, are becoming necessary to acquire data, whose analysis will be used to make decision in a smart way. For industrial applications, motion-tracking systems are strongly developing, being not invasive and able to acquire high amounts of data related to human motion in order to evaluate the ergonomic indexes in an objective way, as well as suggested by standards. For these reasons, a modular inertial motion capture system has been developed at the Department of Engineering of the University of Campania Luigi Vanvitelli. By using low cost Inertial Measurement Units – IMU and sensor fusion algorithms based on Extended Kalman filtering, the system is able to estimate the orientation of each body segment, the posture angles trends and the gait recognition during a working activity in industrial environment. From acquired data it is possible to develop further algorithms to online asses ergonomic indexes according to methods suggested by international standards (i.e. EAWS, OCRA, OWAS). In this paper, the overall ergonomic assessment tool is presented, with an extensive result campaign in automotive assembly lines of Fiat Chrysler Automobiles to prove the effectiveness of the system in an industrial scenario.

Keywords: IMU | Industrial environment | Industrial ergonomics | Motion capture | Wearable device

Abstract: In the present paper, the preload reduction over the time attributed to the relaxation phenomenon which involves hybrid (composite-metal) bolted joints has been experimentally and numerically investigated. Unlike conventional materials (steel, aluminium, etc.), composite ones, due to the presence of the polymeric matrix with viscoelastic properties, feel more considerably the relaxation phenomenon, which begins at room temperature (around 20°C). As a result, the loss in the mechanical fastening is a very critical aspect to consider when composite components have to be bolted to other; further investigations are still mandatory to increase the effectiveness of such jointing techniques. The test article consists of two bolted plates made of mild steel and a composite laminate made by E720 770gms 3×1 T E-Glass roving 1200 Tex 35% RW, respectively. Under this purpose, the preload reduction in the bolt has been experimentally emphasized by developing a novel strain-gauged bolt. Moreover, the relaxation phenomenon has been numerically simulated by developing a complex Finite Element (FE) model.

Keywords: Bolted Joints | Polymeric and Composite Materials | Preload | Stress Relaxation

Abstract: This paper deals with an experimental tests campaign addressed to investigate the structural behaviour of short Glass Fibre Reinforced Polymers (GFRP) plates (PA66 GF30) under Low Velocity Impact (LVI) phenomena, characterized by different impact energy levels, according to the ASTM D7136 requirement. The scope of this research activity must be found in a wider scenario, in which the experimental characterization can be the key-step to develop an established numerical model for the simulation of the experimental tests. Under a Certification by Analysis (CbA) purpose, an established numerical model can be used, rather than to virtually characterize the behaviour of specimens (reducing the costs related to the experimental tests), to simulate LVI on large structural component difficult to test in a laboratory.

Keywords: composite materials | experimental tests | GFRP | Low Velocity Impact

Abstract: This paper deals with a numerical investigation, based on the Finite Element (FE) theory, of a Structural Health Monitoring (SHM) system for a large radio-telescope, aimed to damage detection and location. The investigated SHM system is based on the comparison of the Frequency Response Functions (FRFs) achieved under both pristine and damaged configurations, respectively. A preliminary study has been carried out in order to achieve information on the optimal sensors locations. As a result, the structural response of the radio-telescope under the in-service loading conditions has been numerically investigated. All FE analyses have been carried out by means of MD Nastran® code.

Keywords: Damage | FE Analysis | Modelling | Radio-Telescope | SHM

Abstract: Manual Material Handling (MMH), by pushing or pulling carts, is a common task that characterizes any manufacturing or service operation, and there is always a significant human input to those operations in terms of physical load. The physical load represents the effect of input forces during MMH operations that depend on the interaction between material handling equipment and the working environment. Many times MMH represents a critical issue related to human-machine interaction due to the carts can work in environment with parameters different from those used in designing, subjecting workers to risk of musculoskeletal disorders. The aim of this work, developed in collaboration with Fiat Chrysler Automobiles (FCA), is to develop a new procedure that allows estimating the initial and the maintenance forces necessary to push or pull carts, knowing the characteristics of the cart and the environment in which it works, in order to preventively assess the ergonomic indexes according to ISO 11228-2. The procedure is based on multibody simulations. The cart is modeled by Computer Aided Design (CAD) code and, then, imported in a multibody code where numerical simulations are performed in order to calculate the forces. In the multibody code static and dynamic friction coefficients of bearing of wheels are assigned, together with parameters of contact between wheels and floor. Changing the pivot angle of two floating wheels, several simulations have been carried out. Moreover, considering a cart used at the assembly line of the FCA plant of Pomigliano d'Arco (Naples), experimental tests have been performed in order to validate the procedure by comparing numerical results with the experimental ones.

Keywords: Ergonomics | Material Manual Handling | Multibody | Pushing/Pulling actions

Abstract: In the Industry 4.0 and digital revolution era, the world of manufacturing industry is experiencing an innovative reconfiguration of design tools and methodologies, with a different approach to the production processes organization. The design philosophy is changing, integrating to engineering contribution interpretative aspects (design thinking), executive practices (design doing) and cognitive aspects (design cultures). The design becomes human-centered. The new Virtual Reality technologies allow to validate performances of designed products and production processes by means of virtual prototypes in a virtual simulated environment. This approach generates several benefits to the companies, in terms of costs and time, and allows optimizing the assembly line design and related workplaces, by improving workers' benefits too. This paper proposes an innovative method to validate the design of workplaces on automotive assembly lines in a virtual environment, based on ergonomic approach, according to ERGO - Uas system, applied by FCA (Fiat Chrysler Automobiles) groups, that integrates UAS method for measurement and EAWS method for biomechanical effort evaluation. Creating 3D virtual scenarios allows to carry on assembly tasks by virtual manikins in order to be evaluated from different points of view. In particular, data coming from the simulation can be used to assess several ergonomic indexes, improving safety, quality and design. The analysis is supported by the use of a motion capture system, developed by the University of Campania and composed of wearable inertial sensors, that estimates the attitude of fundamental human segments, using sensor fusion algorithms based on Kalman filtering. In this way, it is possible to make a further design validation, assessing the EAWS index basing on posture angles trends evaluated. This method can represent an innovation for human-centered design of workplace in developing new products, reducing costs and improving job quality.

Keywords: design | ergonomics | manufacturing | motion capture | product feasibility | simulation | Virtual reality

Abstract: Usually during the design of landing gear, simplified Finite Element (FE) models, based on one-dimensional finite elements (stick model), are used to investigate the in-service reaction forces involving each subcomponent. After that, the design of such subcomponent is carried out through detailed Global/Local FE analyses where, once at time, each component, modelled with threedimensional finite elements, is assembled into a one-dimensional finite elements based FE model, representing the whole landing gear under the investigated loading conditions. Moreover, the landing gears are usually investigated also under a kinematic point of view, through the multibody (MB) methods, which allow achieving the reaction forces involving each subcomponent in a very short time. However, simplified stick (FE) and MB models introduce several approximations, providing results far from the real behaviour of the landing gear. 'erefore, the first goal of this paper consists of assessing the effectiveness of such approaches against a 3D full-FE model. 'ree numerical models of the main landing gear of a regional airliner have been developed, according to MB, "stick," and 3D full-FE methods, respectively. 'e former has been developed by means of ADAMS® software, the other two by means of NASTRAN® software. Once this assessment phase has been carried out, also the Global/Local technique has verified with regard to the results achieved by the 3D full-FE model. Finally, the dynamic behaviour of the landing gear has been investigated both numerically and experimentally. In particular, Magnaghi Aeronautica S.p.A. Company performed the experimental test, consisting of a drop test according to EASA CS 25 regulations. Concerning the 3D full-FE investigation, the analysis has been simulated by means of Ls-Dyna® software. A good level of accuracy has been achieved by all the developed numerical methods.

Abstract: One of the critical issues characterizing the manufacturing industries, which within Industry 4.0 era are experiencing the new human-centered approach in design, is related to working postures assumed by the workers in assembly activities. In order to study the motion of human body, the research team developed an inertial MoCap system, composed by IMUs. The system allows to estimate the attitude of the fundamental segments of the human body, by using a Kalman filtering, and to evaluate the posture angles assumed during the motion. The system is modular, composed by 4 modules, made of 4 sensors. From acquired data it is possible to code algorithms to online assess the desired ergonomic scores, making the system able to take decisions for the workplace design optimization. In this paper, the full body inertial MoCap system is presented, supported by a test case to prove the reliability of the system in industrial environment.

Keywords: IMU | Industrial environment | Kalman filter | Motion tracking | Wearable devices

Abstract: In this paper, a new methodology supporting the design of landing gears is proposed. Generally, a preliminary step is performed with simplified FE model, usually one-dimensional, to achieve the reaction forces involving each component during all aforementioned aircraft operations. Though this approach gives a valid support to the designer, it is characterized by several problems, such as the related approximations. So, it is important, by a numerical point of view, to develop an isostatic FE model equivalent to the real one. In fact, if the landing gear is modelled as hyperstatic, the static equilibrium equations are insufficient for determining the internal forces and reactions on each sub-component; so, the modelled material properties and geometries assume an increasing importance, which gets the model too approximating. The proposed methodology consists of achieving the reaction forces by means of multibody simulations, by overcoming such problems, since each component is modelled as rigid. In this paper, also a FE model for the investigation of the structural response is proposed. Aimed to Certification by Analysis purposes, the developed multibody and the FE models have been assessed against an experimental landing gear drop test carried out by Magnaghi Aeronautica S.p.A., according to the EASA CS 25 regulations.

Keywords: Drop test | Dynamic behaviour | FE analysis | Landing gear | Multibody

Abstract: The introduction of new information and communication technologies (ICT) in factory environment is leading the world of manufacturing industry to a change. Indeed, we talk about Industry 4.0, the fourth industrial revolution, that facilitates the vision of a Smart Factory in which systems become cyber-physical, interact between themselves, monitor and validate physical processes, creating a virtual copy of the physical world and making decisions based on complex numerical analysis. Virtualization and simulation of production processes generate several benefits, in terms of costs and time, optimizing the assembly line design and studying human-machine interaction. Regarding the last topic, this paper proposes an innovative method for ergonomic analysis of workplaces on automotive assembly lines in a virtual environment. The method can represent an innovation for human-centered design of workplace in developing new products, reducing costs and improving job quality thanks to a preventive ergonomic approach.

Keywords: EAWS | Human-centered design | Motion capture system | Virtual ergonomics | Virtual simulation

Abstract: In this paper, a numerical model, based on finite element theory, useful to model the stress-strain state for a bonded single lap joint under peeling load has been presented. The numerical FE model has been developed by means of Abaqus® code in order to reproduce some experimental tests. For FE model validation purpose, the numerical results have been compared with the experimental ones and a good correlation has been achieved. In more detail, the adhesive layer has been modeled by means of cohesive elements. Such elements present some numerical difficulties related to the dependence from the own element size. So, a procedure useful to solve such mesh-dependence has been proposed.

Keywords: adhesive | cohesive zone | FEM | mechanical testing | peeling

Abstract: SPR joints will represent an alternative solution to spot welding in automotive field. However, their fatigue behavior shows several critical issues. After a brief introduction of this new solution, different crack modes are described, emphasizing the parameters that characterize them, i.e. the applied loads, the geometry of the joint and other phenomenon as fretting, vibration and corrosion.

Keywords: crack | fatigue load | joint | SPR