Robert E. Fulton

C-FAR, change favorable representation

In this paper, a methodology called Change Favorable Representation (C-FAR) is presented and explored. This methodology uses existing product data information to capture possible change consequences to a product. C-FAR uses this existing product information model to facilitate change representation, propagation, and qualitative evaluation. The information model schemas main elements are entities, relations among entities, and attributes that describe the entities. C-FAR facilitates change and change evaluation at the attribute level. C-FAR has been evaluated using case studies in structural analysis bumper design, injection molding and printed wiring board thermal analysis. Results show that C-FAR is capable of representing change and provides a reasonable qualitative evaluation of the change consequences.

Substructuring techniques—status and projections☆

Abstract Status and recent developments of substructuring techniques and their application to structural analysis and design are summarized. Discussion focuses on a number of aspects including: multilevel substructuring algorithms; use of hypermatrix and other sparse matrix schemes, use of substructuring in automated design systems and application of substructuring in elasto-plastic problems. Numerical examples are presented to demoostrate the reduction in the number of arithmetic operations and disk storage requirements obtained by using multilevel substructuring techniques. Also discussed are the potential benefits of using such techniques with new computing hardware such as CDC STAR-100 and minicomputer systems.

Integrating Engineering Design and Analysis Using a Multi-Representation Approach †

With the present gap between CAD and CAE, designers are often hindere in their efforts to explore design alternatives and ensure product robustness. This paper describes the multi-representation architecture (MRA)—a design-analysis integration strategy that views CAD-CAE integration as an information-intensive mapping between design models and analysis models. The MRA divides this mapping into subproblems using four information representations: solution method models (SMMs), analysis building blocks (ABBs), product models (PMs), and product model-based analysis models (PBAMs). A key distinction is the explicit representation of design-analysis associativity as PM-ABB idealization linkages that are contained in PBAMs.The MRA achieves flexibility by supporting different solution tools and design tools, and by accommodating analysis models of diverse discipline, complexity and solution method. Object and constraint graph techniques provide modularity and rich semantics.Priority has been given to the class of problems termedroutine analysis—the regular use of established analysis models in product design. Representative solder joint fatigue case studies demonstrate that the MRA enables highly automated routine analysis for mixed formula-based and finite element-based models. Accordingly, one can employ the MRA and associated methodology to create specialized CAE tools that utilize both design information and general purpose solution tools.

Correlation of analytical and experimental approaches to determine thermally induced PWB warpage

Thermomechanical design effects in the printed wiring board (PWB) design process are considered, In particular, a research project for developing advanced finite-element method (FEM)-oriented capabilities to simulate thermally induced PWB warpage is reported. The FE analysis results are validated by correlating them with measurements obtained from a separate experimental approach using the shadow Moire method. >

Application of a parallel equation solver to static fem problems

Abstract This paper reports on a study carried out on the development, evaluation, and implementation of a parallel equation solver for finite element problems. A triangular decomposition approach was used and good parallel processing performance was obtained on a FLEX/32 multicomputer using up to seven processors. The parallel program was incorporated in MSC/NASTRAN and tested for several static stress analysis demonstration problems on CRAY X-MP, IBM 3090 and ALLIANT computers with up to four processors. It was shown that a parallel processing approach can significantly reduce execution time for large scale finite element problems.

Experimental and analytical investigation of thermally induced warpage for printed wiring boards

An analytical approach using finite-element techniques has been developed to simulate PWB (printed wiring board) thermo-mechanical behavior. To validate the analytical approach, a separate experimental approach is being conducted. Four different experimental techniques were investigated for their suitability for PWB warpage measurements: ultrasonics, laser, projection speckle (using vision system), and shadow moire. The shadow moire method has been chosen for measuring warpage of PWBs because it offers good resolution and full-field measurement. Seven test samples with different configurations were carefully designed and fabricated to ensure that the thermally induced warpage would be sufficient for measurement. These test samples consist of copper layers and various FR-4 dielectric layers. Two specimen configurations were tested for a temperature range from 25 degrees C to 100 degrees C. Attempts have also been made to correlate the experimental results with the analytical results, although accurate material properties are not known. A good match was obtained for a set of material properties extracted from a number of publications.<<ETX>>

Concepts and implementation of parallel finite element analysis

Abstract The design of complex engineering systems such as advanced aircraft structures and offshore platforms requires continually increasing levels of detail in supporting analysis. The finite element method is widely used as a computational method with which to model physical systems in various engineering problems. For detailed analyses of complex designs, structural models composed of several thousands of degrees of freedom are no longer uncommon. Such design activities require large order finite element and/or finite difference models and excessive computation demands in both calculation speed and information management. The computer simulation of the nonlinear dynamic response of structures and the implementation of parallel FEM systems on a high speed multiprocessor have received considerable attention in recent years. The driving forces of these activities included the reliable simulation of automotive and aircraft crash phenomena, and the increased performance of computers. Most existing major structural analysis software systems were designed 10–20 years ago and have been optimized for current sequential computers. Such systems often are not well structured to take maximum advantage of the recent and continuing revolution in parallel vector computing capabilities. These parallel vector computer architectures not only occur in the form of large supercomputers, but are now also occurring for minicomputers and even engineering workstations. To benefit from advances in parallel computers, software must be developed which takes maximum advantage of the parallel processing feature.

Structural dynamic analysis on a parallel computer: The finite element machine

Abstract The development of general-purpose finite element computer software systems has provided the capability to analyze a wide range of linear and non-linear structural problems. However, these software systems are severely limited for non-linear response calculations because of the available speed on current sequential computers. Recent and projected advances in parallel multiple instruction multiple data (MIMD) computers provide an opportunity for significant gains in computing speed and for broadening the range of structural problems which may be solved. The key to these gains is the effective selection and implementation of algorithms which exploit parallel computing. This paper documents experiences solving transient response calculations on an experimental MIMD computer, termed the Finite Element Machine. The paper describes the algorithm used, its implementation for parallel computations, and results for representative one- and two-dimensional dynamic response test problems. The results show computation speedups of up to 7.83 for eight processors, and indicate that significant speedups of solution time are possible for non-linear dynamic response calculations through the use of many processors and appropriate parallel integration algorithms. The results are extremely encouraging and suggest that significant speedups in structural computations can be achieved through advances in parallel computers.

Structural dynamics methods for concurrent processing computers

Abstract In the area of crash impact, research is urgently required on the development and evaluation of parallel methods for crash dynamics analysis of complex nonlinear finite element and/or finite difference structural problems. An investigation of selected nonlinear dynamics algorithms appropriate for parallel computers is reported. Implicit methods such as those of the Newmark type which build on the Cholesky decomposition strategy and explicit methods such as the central difference time integration method are included. Both implicit and explicit dynamics algorithms are investigated on two significantly different parallel computers, the FLEX/32 shared memory multicomputer and the INTEL iPSC Hypercube local memory computer.

A data management strategy to control design and manufacturing information

This paper presents an information-based approach to integrate the parallel and serial functions that occur in a typical design and manufacturing environment. EMTRIS (Engineering and Manufacturing Technical Relational Information System), a relational data base application designed using ORACLE [1], was developed to cater to the engineering data needs of practicing designers and engineers working in a large industrial setting. The design and manufacturing activities within a large computer manufacturing plant provided a realistic case study environment for implementing some of the strategies discussed here. A description of the methodology that was employed in designing and implementing EMTRIS and the numerous issues that arise while undertaking such endeavors is presented. Strategies to coordinate the data transfer between different groups of individuals as well as mechanisms to ensure data consistency in such environments are discussed in this context. Various techniques used in documenting the data flows and the interrelationships between different forms of data are also reviewed. The end result in a plantwide database system that integrates the information requirements of multiple groups and disciplines.