Emphasizing Decision Analysis Techniques in the Design Curriculum

Theoretically strong decision approaches such as utility theory are currently being researched for use in engineering design. Countless ad hoc decision tools have preceded this recent work, yet only a handful of these tools are used by industry or taught in universities. Reasons for the emergence of such a small number of acceptable decision tools are not known. In this paper, the opinions of undergraduate engineering students in an industry-sponsored senior design class and their sponsor mentors are studied to identify reasons why some decision tools are more popular than others. Two established decision tools were introduced to the class and used in the projects. A survey was used to gather student and sponsor opinions about the two tools and important aspects of decision tools. Results indicate a variety of factors influencing the students’ preference of one decision tool, including simplicity, clarity of results, the ability to give more emphasis to certain criteria, and ease of communication of results to their sponsors. Other results from the study include information about strategies for integrating decision tools into a design process and the role of projects in promoting reflection and learning by students.

Longitudinal Design Teams: Students Teaching Students

We report on the characteristics of our year-long Longitudinal Design Team (LDT) courses, which have been taught since Fall 1998. Our main goal in these courses is to have teams of undergraduates at all educational levels work together solving problems that involve design in biomedical engineering. Consisting of about ten students, each team is composed mostly of freshmen, who, with the help of upperclassmen mentors and an upperclassman Team Leader, are able to use the knowledge they have gained in their introductory courses and from their life experiences and apply it to biomedical engineering problems. In the Fall semester, teams work on one or two projects, where they design, perform, measure and apply principles of physics to develop an understanding of a bio-mechanical event. In the spring, teams work on individual design projects proposed by “customers.” Faculty mentors interact with the team leaders and they decide how to proceed with their respective projects. Because the course is open to all educational levels, freshman students often reregister for the course as more upper level students. In addition to a learning environment, the design team is also a place for underclassmen to develop relationships with upperclassmen and vice versa. These relationships have proved particularly useful to the freshmen in choosing their courses, as well as in deciding summer and research plans. The upperclassmen are also learning how the knowledge they have gained in their coursework applies to solving practical problems. Although only in operation for three years, others perceive tangible results as well. In particular, the majority of customers are satisfied with the prototypes they receive. These preliminary results indicate that this unique program helps our students become acclimated to our curriculum and in preparing them for their profession.

Thermal Behavior of Aluminum Metal-Matrix Composite During Cooling Process

The paper presents a thermal behavior analysis of metal matrix composite lamina and laminates during a cooling process. A long stainless steel fiber reinforced aluminum metal matrix composite lamina and laminate are used for this purpose. Metal matrix composites were manufactured by using modulus under the action of 30 MPa pressure and heating up to 600 °C. The thermal stresses generated during cooling have a profound effect on the distortion and strength of the composite materials. In this study, thermal stresses, residual stresses and effective thermal expansion coefficients as a function of orientation angle of the aluminum metal matrix composite during a cooling process are investigated. The finite element method was used for thermal stress analysis. For this purpose, four noded rectangular elements were used in the ANSYS finite element code.

Modeling for Optimization (MO-OP): Tools for Manufacturing and Design Engineering Problems

In this paper, a new statistical optimization technique is proposed. The technique employs new variance reduction schemes (VRTs). The performance of three standard designs: L27/L27 OA, L54/L27 OA and L243 / L27 OA are studied. These designs, although both orthogonal and balanced, exhibit high variance reduction properties with questionable convergence in very short number of iterations. Four new composite designs are developed, implemented and compared with the standard ones. These designs are known as: 5-, 7-, 9- and 11-point composite L27 OA. The problem of tolerance allocation with optimal process selection is revisited as a case study for simulation. Results indicate the efficiency of these new designs to reduce variances to lower levels than standard designs and better convergence in fraction of experiments. These designs are then integrated in an optimization algorithm previously developed (Gadallah, M.H., 2000). The algorithm is then modified to deal with the least sensitive optimal solutions for standard and composite designs. Particularly, the parameters that affect the algorithm are varied and their effects on performance of algorithm are studied. A standard manufacturing case study is used for analysis and simulation results for the composite designs are also given.

Educating for Global Product Realization on a Global Scale

Three universities on three continents co-operated in teaching global product realization. The Global Product Realization (GPR) course is a highly innovative course in which virtual classrooms and workshops have been formed via ISDN lines, internet facilities and other information technological means representing the state-of-the-technology. This paper gives an insight into the background, the goals, and the implementation of the course. It also outlines the course contents, the layout, and the supporting infrastructure. The GPR course is based on three backbones: academic lectures, company case studies, and a product development project. Parallel to learning of the theoretical and practical backgrounds from academic and industry experts, the international student groups were busy with the development of a global product. It was a coffeemaker for the American, Dutch and Korean markets. The results achieved by the students were presented at the GPR Closing Workshop and Exhibition, where all participants came together to meet the media and the interested parties from academia and industry. The GPR course is a good example of a successful utilization of the opportunities offered by the latest technologies for the implementation of global design and manufacturing in a global environment.

Design on an International Project

Three US National Laboratories are cooperating on a project to design and provide hardware for a new particle accelerator in a European laboratory. This paper describes the efforts and tools that are being used to coordinate the design and to control the design requirements and configurations between Europe and the US laboratories. The uses of design reviews, technical specifications, and electronic communications are described.

The Effects on Critical Load of Metal-Matrix Composite Plates With a Hole Under In-Plane Loadings

Metal-matrix composite plates consists of several layers of unidirectionally reinforced, fibrous composite laminae which have different in-plane orientations and are bonded together in a certain stacking sequence. Thus, they provide new materials with superior properties of high strength and stiffness. This study deals with analysis of rectangular metal-matrix composite laminates with circular holes under in-plane static loadings. The first-order shear deformation theory is employed in mathematical formulation. The effects on critical load by hole size, ply lamination geometry, plate thickness ratio, loading types and material modulus ratio have been investigated. The finite element method is used for finding critical loads. Numerical solutions are given in graphical forms.

Development and Validation of a S-N Based Two Phase Bending Fatigue Life Prediction Model

The stress-life (S-N) method along with the Palmgren-Miner cumulative damage theory is the simplest and the most commonly used fatigue life prediction technique. Its main advantage is that the material properties needed are easy to collect and life calculation is simple. However under many variable amplitude loading conditions, life predictions have been found to be unreliable. Various modifications have been proposed to the Palmgren-Miner theory, but they have not lead to more reliable life predictions. In this paper, a two-stage cumulative damage model will be developed and validated. This model divides fatigue life into two phases — a crack initiation phase and a crack propagation phase. It will be shown that the proposed method results in greatly improved life prediction capabilities. Also, the proposed method retains the simplicity of the S-N based approach in that the material data is still relatively simple to generate and the calculations are straightforward.

Tolerance Optimization: A Decomposition Scheme, Variance Reduction and Fractional Approximation

Development of involved optimization algorithms is not an easy task for several reasons: First, every analyst is interested in a specific problem; Second, the capabilities of these methods may not be fully understood a priori; Third, coding of multi-purpose and more involved algorithms is not an easy job. In this paper, the optimization problem employing the near to global optimum algorithm is studied (Gadallah, M.H., 2000). The focus is to exploit 2 ideas: First, the algorithm can be modified to act as a variance reduction technique; Second, the algorithm can be modified to tackle the problem of system decomposition. Both ideas are novel within the context of statistical design of experiments. The first, if fully proved experimentally could yield the simultaneous integration of nominal and variance optimization possible. The second, can be extended to deal with multi-dimensional highly constrained systems with ease. These two ideas are explained wife the use of a simple example to illustrate the idea. An algorithm is developed that deal with the problem in several stages according to a predetermined decomposition scheme. The original objective and constraint functions are dealt with to suit each stage. Accordingly, all NP hard problems can ideally be transformed into NP complete ones with a consequence on the number of stages resulting from decomposition. Several decomposition scenarios are used and their results are compared numerically. Two orthogonal arrays and four composite arrays are used to plan experimentation; these are L27OA and L54OA and their subfamilies. These arrays are compared with respect to their statistical measures. The algorithm as such, is very promising optimization tool, especially for coupling system decomposition and variance reduction. Past work focused on either decomposition or statistical optimization. This work offers both capabilities. Several studies are reviewed and conclusions are drawn.

Application of Double Impact Oscillator in Forming

The double impact oscillator represents two symmetrically arranged single impact oscillators. It is the model of a forming machine, which does not spread the impact impulses into its neighborhood. The anti-phase impact motion of this system has the identical dynamics as the single system. The in-phase motion and the influence of asymmetries of the system parameters are studied using numerical simulations. Theoretical and simulation results are verified experimentally.