Product design and engineering

Styling design, as every creature of the modern world, is born from various and multiple parents: taste's, evolution, marketing requirements, technical design constraints, costs and qualitative standards of the project. Furthermore, the multiplying of material and technological resources, extends the creative potential of designers, yet requires the acquisition of new knowledge: this leads to the need, from the very preliminary stages, of concurrent engineering approaches to manage the product development process and the different product views depending on the specialists involved. Time Compression Techniques (Rapid Prototyping, Reverse Engineering, conceptual modelling, process simulation) are suitable tools in implementing Concurrent Engineering principles, especially if based on Internet applications. However, today, the research effort has to be oriented towards the definition of an effective and well-structured model of the design process to successfully integrate such technologies. In this context the goal of the present work is the study of a styling product development methodology to minimize the process iterations maintaining an aesthetically coherent product model representation. We focus on the product model definition (using functional-aesthetic features) and on the 3D digitizing phase, that is the most critical aspect for the shape preservation. A practical example, developed in the office furniture domain, is reported.

In the recent past several studies have been conducted, and several methodologies have been set up to aid the designer in product design development. Another useful development in this field would be tools able to support the designer when he/she is manipulating abstract elements that roughly approximate their final shape and placement in the definitive layout. The paper describes a methodology and a prototype software to support the designer during the conceptual phase. It is based on the creation of a 3D environment, the "design space", where the functional representation of the problem, that the designer has outlined, is increasingly clarified and solved in an architectural lay out of a product.

Keywords: Conceptual design , Creative design , Early phases of design

The object of this paper is an investigation of the relationship existing between two experimental techniques, both aimed at the assessment of micro-plastic phenomena and micro-friction inside a material: thermographic analysis and specific damping measurement. A model has been developed here considering the main thermal effects during fatigue tests, and a theoretical relationship between temperature increment and specific damping has been proposed. Successively, an extensive experimentation has been carried on groups of specimens made of two different metals, stressed by means of an Amsler vibrophore. Different stress amplitudes (80-270 MPa) and frequencies (80-160 Hz) have been employed. The analysis of experimental results has allowed the validation of the suggested model, leading, on one side, to the development of a further experimental technique for the evaluation of specific damping, and, on the other side, to the employment of specific damping measurement for the assessment of fatigue in metals. © 2003 Elsevier Science Ltd. All rights reserved.

Keywords: Elastoplastic behaviour , Fatigue , Hysteresis strain energy , Internal damping , Thermal , Thermographic analysis

The development of extremely high performance aerospace power transmissions will be a very interesting technological challenge for the next future. In gear design for high power transmissions, desirable characteristics, such as low noise emissions, low vibrations, minimum size, minimum maintenance cost, but most of all minimum weight can be obtained through the development of innovative layouts. However, most of the rules based on experimental data, by which common gears are calculated and verified, are not applicable to transmissions which can be defined unconventional in terms of geometry and/or operating conditions (high power, high rotating speed, low weight). In these cases, numerical simulations can be performed by using FEM codes. The objective of this work is to describe how integrated CAD/FEM tools can be employed to develop procedures for the static performance analysis of unconventional gears. In the paper, potential characteristics, limits and capabilities of simulating real system behaviours are discussed.

Keywords: Computer aided design , Finite element method , Gear design

In this paper, we analyse the design of a support plate for the accumulator of an electric motor vehicle. The support is an integral part of motor vehicle chassis. Therefore, geometrical configuration and boundary conditions require careful optimisation research of both function and structural behaviour, since lightness and dimension problems in the presence of dynamic stresses due to external factors have to be considered. Since these factors are complex and not homogeneous, the problem requires multi-criteria analysis. The presence of factors that are not precisely computable calls for fuzzy-logic application to optimisation problems, because fuzzy-logic is non-standard logic, particularly suitable for making choices in structural design. In plate optimisation, in fact, not numerically quantifiable characteristics such as a part's workability, numerically determinable structural values such as stresses and strains, and analytically calculable properties such as weight come into play. These four parameters become the domain of fuzzy membership functions, by which we will extract membership grade values (co-domain). Design variables (domain) are plate thickness, ashlar's number on the plate and stiffening ashlar's depth. In our research, we characterise fuzzy correlation between parameters and required characteristics in order to determine, according to non-standard logics, the best topological configuration which corresponds to the optimisation of individualised characteristics in conformity with design constraints. Results show value improvement in stress and strain in comparison with the not yet optimised plate and small reduction in workability, whereas the mass is almost the same. © 2002 Published by Elsevier Science B.V.

Keywords: Decision making , Fuzzy logic , Structural optimisation

Spacedesign is an innovative mixed reality (MR) application addressed to aesthetic design of free form curves and surfaces. It is a unique and comprehensive approach which uses task-specific configurations to support the design workflow from concept to mock-up evaluation and review. The first-phase conceptual design benefits from a workbench-like 3-D display for free hand sketching, surfacing and engineering visualization. Semitransparent stereo glasses augment the pre-production physical prototype by additional shapes, textures and annotations. Both workspaces share a common interface and allow collaboration and cooperation between different experts, who can configure the system for the specific task. A faster design workflow and CAD data consistency can be thus naturally achieved. Tests and collaborations with designers, mainly from automotive industry, are providing systematic feedback for this ongoing research. As far as the authors are concerned, there is no known similar approach that integrates the creation and editing phase of 3D curves and surfaces in virtual and augmented reality (VR/AR). Herein we see the major contribution of our new application.

Noise and vibrations levels are basic parameters in passenger comfort. Vibrations are commonly reduced by adding a layer of damping material to the metal sheet of parts of the vehicle body such as the floor, the roof, the firewall. In common practice the panels to be treated are uniformly covered by a layer of damping material; however this is not an efficient design solution especially with regard to the weight containment. In this paper a novel approach to the optimal damping material distribution will be presented. The proposed method is based on a genetic algorithm procedure which takes into account both the vibrational performance and the weight and cost reduction. A simple case study will be illustrated to demonstrate the capabilities of the developed procedure.

In this paper is analysed the problem, using soft models, of soft dependence of parameters in design systems. A new form of computing, called Soft Computing, is recently used in many emerging disciplines because it is tolerant to imprecision, uncertainty and partial truth. The Soft Computing uses many disciplines as Bayesian inference and maximum entropy method. The logic relationship that ties the different elements can be defined more easily using the axioms of soft design emanating from MinEnt principle. The fundamental axiom of design is: valid design has minimum values of information and depends on a finite and limited number of independent, or soft dependent, parameters. © 2002 Published by Elsevier Science B.V.

Keywords: Axiomatic design , Entropy , MaxEnt , Soft Computing , Soft design , Uncertainty

In the mechanical transmission field, shaft-hub couplings with polygonal profiles play an interesting role because of their characteristics of self-alignment, lack of projecting elements (responsible for high stress concentration) and constructive compactness. Other characteristics, like transmission of static/oscillating torque load, even with small overall dimensions, and easy hub interchangeability, make such couplings competitive with the traditional ones based on keys and splined shafts. This work concerns a study on steel made polygonal couplings, with trochoidal three-lobe profile, and is aimed to highlight the contact stress and strain state of shaft-hub interface, with reference to particular profile geometric parameters. From Mechnik's and Kollmann's works, in which the analysis was performed by the Finite Element Method, this work develops a CAD/CAE methodology for coupling design, oriented to an efficient integration between CAD systems and BEM solvers. The stress analysis is carried out with a Boundary Element code (BEASY) well suited for this kind of contact problems while coupling geometric model is made by Pro/Engineer, a solid parametric modeller.

In this paper, B-spline curve fitting and sweep surface generation are used for the geometric design of involute gears. Tooth profiles are described by a B-spline formulation based on interpolating data points with first and second derivative constrains. Tooth surfaces are generated by sweeping the B-spline profiles along specified trajectories. This representation scheme enables tooth shapes to be interactively controlled by manipulating control polygons and sweep trajectories. A CAD-CAE integration allows the analysis of contact and structural three-dimensional problems for various geometric configurations. In the paper, the methodology is applied to the geometric design of involute pinions of face gear drives.

Keywords: B-splines , CAD , Curve fitting , Gear design , Geometric design , Sweep surfaces

Face gear drives have many advantageous characteristics compared to other angular transmissions but their complex geometry makes their design difficult with common approaches. This work is aimed at investigating the stress state of the teeth of a face gear and the mating pinion by integrating a 3D CAD system and a FEA code, and by simulating the meshing of a pinion and gear three teeth sector using contact elements and an automated contact algorithm. The procedures followed to create the 3D models of teeth in mesh are described and finite element analysis results are discussed.

Keywords: CAD , Contact analysis , FEM , Gear design

The paper presents a robot prototype designed for the autonomous fuelling of vehicles, with attention on users safety and surrounding impact. The overall duty is analysed and proper suggestions are developed to organise the operation cycle in view of regulatory schemes, most likely, soon issued by Authorities for development sustainability rules. The manipulation architecture appears to be central requirement for the effectiveness of any feasible fixture and the main characteristics of the purposely selected solution are shortly summarised. For the related overseeing arrangement, the project moves from an analysis of prototypal fixtures, already built and tested in the USA and EU, and looks about opportunities in standardising subsets of vehicles devices to simplify the fuelling tasks.

Keywords: Autonomous fuelling , Environment safety and protection , Marginal safety , Multibody systems dynamics , Robotic system design , Service robotics

The evolution of computer aided design (CAD) systems and related technologies has promoted the development of software for the automatic configuration of mechanical systems. This occurred with the introduction of knowledge aided engineering (KAE) systems that enable computers to support the designer during the decision-making process. This paper presents a knowledge-based application that allows the designer to automatically compute and evaluate mass properties of racing cars. The system is constituted by two main components: the computing core, which determines the car model, and the graphic user interface, because of which the system may be used also by nonprogrammers. The computing core creates the model of the car based on a tree structure, which contains all car subsystems (e.g., suspension and chassis). Different part-subpart relationships define the tree model and link an object (e.g., suspension) to its components (e.g., wishbones and wheel). The definition of independent parameters (including design variables) and relationships definition allows the model to configure itself by evaluating all properties related to dimension, position, mass, etc. The graphic user interface allows the end user to interact with the car model by editing independent design parameters. It visualizes the main outputs of the model, which consist in numeric data (mass, center of mass of both the car and its subsystems) and graphic elements (car and subsystems 3D representation).

A genetic algorithm has been designed to optimize the arrangement of stiffening ribs that serve to reduce vibrations and noise in dynamically excited panels. The algorithm was tested on the finite element model of a flat panel whose ribs were modeled by raising some of the nodes. The proposed algorithm, validated by comparison with a panel derived from a commercial software package optimization procedure, allows designers to investigate unconventional rib arrangements and evaluate their performance.

In the field of new stamping technologies, hydroforming represents one of the most attractive solution both to reach a better quality and reduce lead-times. This paper presents a study that is being carried out to assess an optimal hydroforming process for production of automotive panels. The major economical advantages are due to the need of only one dedicated shape-defining tool, this leads also to a more flexible production system. The research starts from the analysis of two different process arrangements: hydro-punch versus negative or positive die. Their numerical simulations (performed by LS-DYNA3D) are used to define the values of control factors (maximum pressure, blankholder force) and to highlight, in terms of shape and strain field accordance, the pros and cons of each solution. To assess the better arrangement an economical evaluation is carried out using a decision making approach. The discussion is based on press shop experience related to three different components: an exterior panel of a bus, a detail of bus luggage van and a bus roof. Copyright © 2000 Society of Automotive Engineers, Inc.

Screw Theory is well known to do kinematic computations. Recently it has been used to create kinematic models of assembly features so allowing to do assembly analysis. Motion Limit Analysis uses the mathematics of screw theory to model the ability of mechanical assembly features to allow or constrain rigid body motions in six degrees of freedom. A user of this theory is able to determine the directions and quantitative amounts of possible finite rigid body motions of a part that is being added to an assembly via calculation applied to a defined set of assembly features. The ability to calculate rigid body motions of a part is important for enabling in-process adjustment during assembly to precisely establish key assembly dimensions. MLA software is a part of a suite of software programs used to do assembly analysis.

An experimental investigation was undertaken to determine the causes of noise emission scatter in hosiery machines. Following the experimental measurement of the sound power levels, the hosiery machine's mechanical system was assembled and tested with components of various sizes. The results indicated that the source of the noise emissions was a bearing's outer race. Analysis of the outer race's roundness profile in relation to vibrations provided accurate predictions of machine behavior. On the basis of a correlation between noise and vibrations, a practical method of online monitoring was developed.

Keywords: Fault Detection , Needle Roller Bearings , Noise and Vibrations , Online Monitoring

Kinematic modelling of robots and flexible material simulation have been an important aspect in robotic research issues over the last years. In this article a new approach for the design of arbitrary gripper and robot architectures will be presented. It will be shown how these robot systems can be simulated based on the presented design structure. Further the integration of flexible material simulation will be displayed. A particle based object models will be shown and the mathematical basics will be described. Finally, the integration of the flexible material simulation into the robot simulation software will be displayed and evaluated.

A fuzzy method to handle vagueness and imprecision in the description of requirements for multi-attribute decision making (MADM) problem is presented. This method is applied to design of an apron conveyors to collect and transfer scraps. The aggregation function for the overall evaluation is obtained utilising the Taguchi loss functions.

A prst step towards a semi-immersive Virtual Reality (L!R) interface for Finite Element Analysis (FEA) is presented in this paper. During recent years, user interfaces of FM solvers have matured from characterbased command-line driven implementations into easy-touse graphical user interfaces (GUS). This new generation of GUIs provides access to intuitive and productive tools for the management and analysis of structural problems. Many pre-And post-processors have been implemented targeting the simplification of the manmachine interface in order to increase the ease of use and provide better visual analysis of FEA solver results. Nevertheless, none of these packages provides a real 3Denabled interface. The main objective of this project is to join state-of-The-Art visualization technology, VT devices, and FM solvers into the integrated development environment VRFM.

Keywords: 3D Modeling , Finite Element Analysis , Interactive Modeling , Simulation. , Virtual Reality