ME 471/671 COMPUTER AIDED ENGINEERING ANALYSIS & DESIGN Dr. Georges M. Fadel 0. Introduction What is Computer Aided Design? What is Computer Aided Design or CAD? This acronym has been used by many to signify the use of the computer to help in the design process. So where in the design process does the computer help? Obviously, in the drafting process, the computer can help eliminate redundant operations; it can help ensure that lines are perpendicular or parallel to each other. It can allow cut and paste operations to reproduce sections of a design, it allows easy mirroring, rotating, translating, zooming, etc. Thus, is CAD Computer Aided Drafting? You know you use the computer for many more applications. Where else can computers help? Naturally, in the process of performing calculations, simulations, and analyses, they can also help in visualization, in making decisions, and in storing information. Thus, the computer as a tool has a much broader application range than just drafting. Furthermore, the computer can be used as an interface to machines; this is where computer aided manufacturing, rapid prototyping and or NC machining come into play. If making a prototype to help the design is part of the process, then computer driven prototyping is also part of CAD, however, what comes after the design process, in particular production or manufacturing, is at the fringes of CAD, and in this write-up, Computer Aided Manufacturing, CAM, will not be treated as part of the CAD process. Thus, computer aided design education has to deal with the computer as a tool to help perform the various tasks that comprise the design process. This is referred to in the design field as design automation. In order to understand the capabilities of that tool, one has to study how the tool is used in the different steps of the design process. This course will cover several topics. First, the design process will be detailed to identify where the computer plays a role. Once this is done, the aspects of computer aided graphical representation must be covered. Here, it is important to understand how the computer is used to represent lines, curves, surfaces, solids, and features. To this end, the mathematics of geometric modeling have to be understood. Since these mathematics are based on matrix operations, a review of matrix mathematics is covered. The material covered is by no means exhaustive. The purpose of the class is to impart a good understanding of the capabilities and limitations of computer tools for design. It is also designed to wet the appetite of the student to motivate him or her to take additional courses, which treat of some of these topics in more detail. Once the object to be designed has been represented, analysis tools come into play. Here, the finite elements method is becoming a de-facto tool for the analysis of strength, fatigue, heat dissipation, noise, fluid flow, etc.. Therefore, an introduction to the process of approximating an object by finite elements for purposes of analysis will be presented. The results of the finite element analyses must be used to help the designer make decisions. First, can the designer understand the results obtained? Are these results according to expectations? Are the design features correctly placed to accomplish the desired functions? If yes, what can be modified in order to improve that design? Here, optimization plays a role. Again, this mathematical approach to modifying parameters in the search for a better solution is an essential tool for the designer. He or she has to take these results and examine them, making sure that predicted trends coincide with the results obtained. If not, why are these results different? Once iterations of the design have been accomplished, and the designer is happy with the outcome, a prototype should be prepared. The topics of virtual and physical prototypes will be discussed. The functionality of these prototypes, their usefulness for touch and feel issues, for manufacturing or assembly issues should be studied, and a final recommendation on the design derived. During this whole process, the storage of information and the issue of decision aiding will be explored. The student is expected to come out with an appreciation for the impact of the computer in the design process. The student should be able to further his knowledge in any of the fields covered, and have a working introduction to the CAD tools. This course is not a training course where we select some software and teach the students to use that particular software. It is not a course in Autocad, Catia, Ideas, UG, Pro-E, Ansys, or Abaqus, it is a course in Computer Aided Engineering Analysis and Design. Chinyere Onwubiko  gives a comprehensive definition of CAD: “Computer Aided Design is an automation process in which computer systems are used to aid in the design process from conception and synthesis, through analysis, optimization and drafting, to building and testing of prototypes.” He adds: “The educational objectives should be to provide the fundamentals, so that the graduate will leave the academic environment with the ability to take the steps necessary to become a CAD practitioner in industry”. To do design with the computer, that computer as a tool must be programmed, mathematical issues must be explored, limitations must be well understood, and an increase in productivity from the designer must ensue. The practitioner must especially appreciate that the use of a tool is not an ends all; the garbage in garbage out syndrome is often the result of relying on computational tools without using sound engineering judgment to verify the validity of the assumptions and results. I intend to provide you the engineer with an appreciation for these issues by offering this course.