Högskolan i Skövde

A method to determine constitutive properties of thin adhesive layers loaded in shear is presented. The test specimen consists of two adherends joined by the adhesive layer. By loading the specimen antisymmetrically with respect to the adhesive layer a state of pure shear is ensured. To avoid instability the test specimen is designed to give a non-uniform stress distribution in the adhesive layer. This is achieved by using a long specimen loaded at one side. The method is based on an exact inverse solution which is derived utilizing the balance of the energetic forces of the applied loads and of the adhesive at the start of the adhesive layer. The method is intended for determination of both hardening and softening behaviour of adhesives but is confined to monotonic loading

An experimental method to determine the stress–elongation relation for a thin adhesive layer loaded in peel is presented. The method is based on equilibrium of the energetic forces acting on a DCB-specimen. These energetic forces are identified to be associated with the geometrical positions of the acting loads and the start of the adhesive layer. The first energetic force is shown to be given by the product of the force and the rotation of the loading point. The second energetic force is shown to be given by the area under the stress–elongation curve for the adhesive layer. Using equilibrium of these energetic forces, the shape of the stress–elongation curve is determined. A test set-up is developed to facilitate the experiments. Special consideration is given to the accuracy of the measurement of the elongation of the adhesive. Results from two sets of experiments with slightly varying geometry are presented. The main result is that the stress–elongation relation can be described by a curve divided into three parts; initially the stress increases proportionally to the elongation. This corresponds to a linear elastic behaviour of the layer. The next part is given by a constant limiting stress. The curve ends with a parabolically softening part. After this point, a crack has been initiated in the adhesive. The experimental results are first compared to an asymptotic analysis using linear elastic fracture mechanics. This shows that the new method to evaluate the fracture energy gives consistent results. The experiments are also simulated using the measured stress–elongation law. Good agreement with the experiments is achieved which further validates the method. The fracture energy and the maximum peel stress are found to agree well within each set of experiments. Some variation is found between the two sets. This is accredited to differences in fracture initiation

The valence photoemission spectra of alkali metals exhibit multiple plasmon satellite structure. The calculated spectral functions within the GW approximation show only one plasmon satellite at too large binding energy. In this Letter we use the cumulant expansion approach to obtain the spectral functions of Na and Al from ab initio calculations including the effects of band structure. The GW spectral functions are dramatically improved and the positions of the multiple plasmon satellites are in very good agreement with experiment while their intensities cannot be explained from intrinsic effects only.

The spectral functions of highly correlated systems Gd and NiO have been calculated within the GW approximation. In the case of Gd, satellites are found at the positions of the experimental main peaks. However, some quasiparticle weight remains at the local density eigenvalue but its weight is unusually small (0.3). In NiO, satellite structure is observed at around -10 eV when starting from the local density Hamiltonian. It is found, however, that the satellite intensity is reduced towards self-consistency and almost disappears. © 1996 The American Physical Society.

The aim of the present case study is to present and evaluate a computer-based standardized procedure to order, perform and document virtual ergonomic analyses. Results showed that the use of the new working methodology increased the number of factors considered during analysis. Participants indicated that the proposed methodology, including task analysis and use of manikin families, would increase the reliability of the results. The increase in numbers of factors considered during analysis and the improved reliability of the results is also likely to reduce the number of iterations needed in the design process to make products meet established requirements, therefore reducing total development time.

Developers, reviewers and users of human simulation tools claim that the use of these tools may reduce development time and development cost. However, before these benefits will be fully visible, there are some barriers to overcome. The aims of this case study are to identify which departments at Saab Automobile use some sort of human simulation tool today, and to identify the information flow and procedure when the tool is used. Four departments crash safety, packaging, production planning and vehicle ergonomics were identified as direct users of human simulation tools. The tools used were finite element with crash dummy representation, SAE human model, Safework and Ramsis. Communications between human simulation tool users are limited. Communications are done through the project management. The crash safety and packaging departments have formal descriptions of the human simulation process, whereas production planning and vehicle ergonomics have no formal process descriptions. To gain from the benefits of human simulation tools, Saab Automobile needs to adapt them to the organization and the organization to the tools. Integration of a working methodology is essential for effective and efficient use in the other human simulation departments where this is currently lacking.

Sensor simulation in Computer Aided Robotics (CAR) can enhance the capabilities of such systems to enable off-line generation of programmes for sensor driven robots. However, such sensor simulation is not commonly supported in current computer aided robotic environments. A generic sensor object model for the simulation of sensors in graphical environments is described in this paper. Such a model can be used to simulate a variety of sensors, for example photoelectric, proximity and ultrasonic sensors. Tests results presented here show that this generic sensor model can be customised to emulate the characteristics of the real sensors. The preliminary findings from the first off-line trained mobile robot are presented. The results indicate that sensor simulation within CARs can be used to train robots to adapt to changing environments.

Virtual robotics can be used to dramatically improve the capabilities and performance of industrial robotic systems. Virtual robotics encapsulates graphical off-line programming systems and Computer Aided Robotics (CAR). However current virtual robotic tools suffer from a number of major limitations which severely restrict the ways in which they can be deployed and the performance advantages they offer to the industrial user. The research study focuses on simulation of sensors, programming of event based robotic systerns and demonstrates how intelligent robots can be trained adaptive behaviours in virtual environments. Contemporary graphical programming systems for robots can only be used to program limited sections of a robot program, since i) they do not support methods for the simulation of sensors and event detection; ii) they normally use a post-processor to translate programs from a general language to a controller specific language; iii) conternporary robots can not easily adapt to changes in their environments; and iv) robot programs created off-line must be calibrated to adjust to differences between the virtual and real robotic workcells.

The thesis introduces a generic sensor model which can be used to model a variety of sensor types. This model allows virtual sensors to work as independent devices. It is demonstrated that using simulated sensors, event-based robot programs can be created and debugged entirely off-line. Off-line programming of event-based robotic systems demands methods for realistic handling of the communication between independent devices and process. The system must also possess the ability to manage and store information describing status and events in the environment. A blackboard architecture has been used in this research study to store environmental conditions and manage inter-process communication.

Self-learning robots is a possible strategy to allow robots to adapt to environmental changes and to learn from their experience. If suitable learning regimes are developed robots can learn to detect changes between virtual and real environments thus minimising the need for calibration. Most learning is based on experience and this requires experimental data to be fed to the learning system. This thesis demonstrates that robot controllers using artificial neural networks for knowledge acquisition and storage can be 'pre-emptively learnt' in virtual robotic environments using virtual robots and simulated sensors. The controllers are able to generalise from the information acquired by the virtual sensors operating in the virtual environment. Arguably the biggest obstacle to the use of self learning robotic systems in real applications has been the need to train the 'real robots' extensively in the 'real environment'. 'Pre-emptive learning' removes this problem. Furthermore, it is therefore possible to develop and evaluate new learning regimes using virtual robotic systems. This approach provides an opportunity to create a variety of environments and conditions which would be impractical to create in a real environment (due to constraints of time, cost and availability). 

The employment of the design methods of characters and scenarios in the conceptual design of a gearshift system for future automobiles is presented. The main objective for the project was to provide design suggestions for a gearshift system that people will appreciate in future cars in view of market trends, technology developments and environmental demands. The methods were tested for concept evaluation at a Swedish car component manufacturer. The methods gave rough, but important, indications of possible appreciation and acceptance of design proposals, and assisted consideration of user diversity. This low-cost approach is sufficient for evaluation purposes at early design stages, but may be complemented with more thorough studies if time and money permits.

The employment of the finite element (FE) method in conceptual and detail design of a secondary deck platform for trailer bodies is presented. The main objective of the project is to design a versatile, light and cheap secondary deck. To assist the designer with sufficient means for the concept generation and evaluation process, the FE method is used in order to gain fair structural analysis data. Assistance from the computer software stimulates creativity, reduces the time required in the design process, and eventually increases probability to gain customer satisfaction. This approach is precise enough for comparison purposes at this stage of the design process. The structural data gained is compared mainly with weight and access criteria.

The automotive industry faces increasingly tough competition in a global market. One key for competitiveness is product differentiation, in order to attract clearly defined market segments. However, designing cars for specific customer groups incorporates the risk that a car appeals to only a small number of potential buyers. Another issue is that the actual customer group in many cases differs fromthe initially targeted customer group. The use of the ‘design for all’ (DfAll) concept may very well enlarge a car manufacturer’s market and improve the vehicles by making them suit larger populations. This paper discusses the aims of a research project that seeks to identify areas where both the main targeted customer group andothers can gain from a ‘design for all’ approach. Other objectives are to suggest working methods that enable ‘design for all’ in the automotive development process and the identification of computer tools, such as virtual manikins, that can support these objectives early in a virtual design process.

Ergonomic evaluation typically comes late in the automotive design process, often not performed until physical mock-ups are produced. This may lead to expensive and cumbersome iterations, or to reductions of the final product quality due to low priority of meeting set ergonomic requirements. Computer aided design (CAD) is intensively used for design in the automotive industry. Performance and usability of computers and software are improving at a rapid pace, which enables CAD to be employed even more intensively. This encourages a digital design process where expensive, inflexible and time consuming physical mock-ups are only built at the end of the design process. This incorporates the risk that ergonomic evaluation will be put back even further. A way to address this problem is to enable ergonomics to be evaluated in the digital design process - in a virtual product. However, in many cases, evaluation made in a physical prototype is unbeatable in establishing ergonomic conditions. This paper discusses possible advantages of moving ergonomic evaluation earlier in the automotive design process by implementing planned overlapping strategies. It also shows initial results from a project at a car company, which aims at improving ergonomics integration in the automotive design process, e.g. by looking at task overlapping. These strategies are believed to be applicable both for evaluations made in a virtual environment and evaluations performed in the real world.

Commonly percentiles are used to define users’ bodily dimensions. The percentile approach is however not suitable for multivariate problems such as the design of car cockpits, i.e. where a range of body segment dimensions affects the design. An alternative way is to use a set, afamily, of manikins for evaluation that better represents human variety. The aim of this study was to compare seat and steering wheel adjustment ranges obtained when using manikin families or a percentile approach as the user representation in human simulation software. Results obtained indicate that a more elaborate and careful consideration of users can be achieved when using a manikin family approach for human accommodation compared to apercentile approach.

We have calculated the plasmon-width dispersion of Li within the random-phase approximation including the full band structure. The dispersion is found to be negative for small momentum transfers, which is in agreement with experiment. This anomaly is due to the band structure. The energy-loss spectra are found to exhibit a small peak at low energy which can be traced back to the gap at the zone boundaries. This confirms the interpretation of the peak as a so called zone-boundary collective state.

Information management in 21st century industry has many aspects that have to be fully understood and covered in an information plan. With the emergence of CAD, problems with version management became more profound. Product data management (PDM) systems offered a partial solution, but these systems do not cover complete product life cycle support across complete supply/demand chain networks and seldom address manufacturing resource and process modeling in an adequate manner. This paper discusses some trends and tools in manufacturing information management and product life cycle support, with a focus on reuse of existing production resource information throughout the product process resource domain

Over the past years, it has become more common in industry to use virtual manufacturing applications such as robotic simulations, FEM-analysis and factory flow simulation in various stages of the development of products and production facilities. As a result, today’s industry struggles with providing sufficient data for the growing virtual manufacturing activities, especially in situations where multiple subcontractors and project partners are involved. However, there have seldom been any specific requirements on the data shared by these engineering tools. This paper describes a project for maintaining context, semantic and structure on information acquired by VMS applications in an adequate way. The use of standards associated with this kind of work is strongly advocated. Therefore, standards covering different areas have to be considered and combined in order to form a solid foundation for the project.

There are many things that make products successful in the market place. This paper is a comprehensive tool for understanding how to develop products with special respect to integrated product development. Materials selection, marketing and design analysis in the form of a design manual are presented as a tool for the product developer. Many different methods for materials selection and design have been presented over the last couple of decades. However, most methods have been limited to the material as a physical entity to give shape for a product. The method presented in this paper is an approach to present a materials selection model that is an integral part in an integrated product development model, in which both physical and metaphysical properties are analysed for different types of products. The new integrated product materials selection (IPMS) model presented incorporates factors such as fashion, market trends, cultural aspects, aesthetics and recycling, as well as the target group. Interesting examples of successful product contra failures are presented, as well as examples of materials selection for different products. Different methods for materials selection are discussed and analysed with respect to the IPMS method presented.

An increase in functionality of Semi-Autonomous Vehicles (SAV) through the implementation of intelligent distributed control and smart sensing techniques is presented. In combination with a modular design approach, this facilitates system modification and improvement, combined with faster customisation of the platform. A distributed and reactive behavioural control architecture will be used to realise local autonomous navigation capabilities; improved operator interaction; self protection and safer operation. A virtual engineering environment based on a suitable computer-aided-graphics platform will be used for modelling the vehicle; the environment in which it can operate; and pre-emptive learning and training of responses / behaviours.

An increase in functionality of semi-autonomous vehicles (SAV) through the implementation of intelligent distributed control and smart sensing techniques is presented. In combination with a modular design approach, this facilitates system modification and improvement, combined with faster customisation of the platform. A distributed and reactive behavioural control architecture is used to realise local autonomous navigation capabilities; improved operator interaction; self protection and safer operation. A virtual engineering environment based on a computer-aided-graphics platform is used (1) for modelling the vehicle and the environment in which it can operate; (2) developing pre-emptive learning and training of responses/behaviours, and (3) for evaluation of vehicle functionality as part of an integrated materials handling system.

Simulation of sensor systems for mobile robots are described in this paper. By simulation of smart sensor systems, the performance of semi-autonomous vehicles / mobile robots can be enhanced. Smart sensor systems used in the field of mobile robotics can utilise adaptive algorithms. e. g. artificial neural nets, fuzzy logic or hybrid variants of these systems. The development, training and evaluation of adaptive algorithms for sensor systems can be done within a virtual environment in which graphical models are built to simulate an intelligent vehicle, its sensors, and its environment. The virtual sensors are validated by comparing the characteristics of the virtual sensors with those of the real devices.

The paper describes the development of Semi-Autonomous Vehicles (SAVS) in the context of Automated Guided Vehicle Systems (AGVS). During the design process of a complete material handling AGV-system many variables must be decided. A two-stage simulation approach of discrete event simulation and continuous path simulation, improves development and testing of SAVS, Decisions need to be made e. g. what main navigation sensor to use, how many vehicles are needed for the task. The interrelation of these parameters makes it difficult to find optimum or near-optimum values. Because of this, simulation is a very useful tool to design and evaluate AGV-systems. Copyright (C) 2000 IFAC.