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      MSE 5090: Case Studies in Material Selection

      Week 7 - Material Selection: Constraints and Design Requirements

      Read this entire document before starting the assigments.
       
      1. Objectives
      2. Reading assignment
      3. Discussion questions
      4. Lecture Topics
      5. Week 7 assignments:  Ashby ProblemsCS Criteria  CS InterviewsCS Indices
      6. Reference Material


      Objectives:
      How to include multiple constraints and performance indices in selection
      How to deal with overconstrained and underconstrained problems in selection
      Compare and contrast spread sheets, graphs and software in materials selection
      How to differentiate problem space, design requirements, constraints and performance indices in materials selection
       This week we will be studying cases in the materials selection without shape. Materials selection problems can be  over-constrained or under-constrained, and some can  have multiple selection criteria. In that sense the selection problem is like a phase diagram problem . There are a certain number of variables under your control, the so-called free variables. A variable is like a degree of freedom in thermodynamics. This week we will be studying how to develop performance indices for various types of problems.

      In solving Ashby problems one can use the software or the materials selection charts included with the book. The software , because of the enhanced data bases, provide a more specific materials selection than the charts. In that regard, if you want to use the charts , feel free to use the department coursework auditron to copy the charts you need.

      The CMS software focuses on mechanical variables and process variables. Electrical variables are not treated at all; ultrasonic and thermal variables are treated in a cursory manner; and corrosion and environmental variables are just touched upon. Economics and failure modes are hardly treated at all. Therefore , for problems that fall outside the variables the CMS software treats one has to fall back to the use of spreadsheets such as the type used on an earlier homework. In essence , one selects , normalizes and weights the data and comes up with  scores ranking the materials.
       



      Reading Assignment:
      Page 66-69  Materials Selection with multiple constraints
      Ashby pages 70-131-Materials Selection  Case Studies


      Discussion Questions:
      How does one handle a problem with conflicting constraints?
      How does one handle problems with multiple constraints and selection criteria?
      How does one handle over or underconstrained problems?
      What are the values of external contacts compared to the net or the literature in obtaining technical information.?
      What are  the values of external contacts in obtaining non-technical information?ss


      Lecture Topics:
       
      Monday Review of Ashby problems, homework  and others from book
      Wednesday Materials selection with multiple constraints
      Friday Dealing with over/underconstrained problems. Managing contacts



      Week 7 Assignments:

      Ashby B 3.10, B 3.11, B 3.13, B 3.14 and B 3.17 (Due 10/21/98)
      Subject: Week 7 - Ashby B 3.10, 3.11, 3.13, 3.14 & 3.17
      10/10/98
       

      Compose Case Study:  Selection Criteria, Constraints, and Enumerations of Performance (Due 10/30/98)
      Subject: Week 7 - Case Study Selection Criteria

      Conduct Case Study External Contact interview(s) (Due 10/28/98)
      Subject: Week 7 - External Contact Log

      This is an extension of the contact plan you developed in week six.  Conduct your interview(s) as soon as you can.  You may need to make adjustments based on new insights gained from your contact.  Include significant quotes, notes, and summations in your log.  It will make it much easier for you to include quotes in your case study when you have them at hand including the reference notations. Verify with your contact that what you heard is what was said.

      Presentation of Case Study: Functional Requirements and Indicies (Class period 10/23/98)
      At this time a couple of students will discuss how they are developing a meta model of their case study application. It is worth noting in that regard that the use of performance indices obviates the need for a full modelling activity . In essence, the performance indices facilitate materials selection by determining the key variables(degrees of freedom) in a selection problem and using a graphical representation of the data to select the best material for the application. A full blown simulation of the application would model the performance of the material in the application, but would not yield any more optimum solution. The key is the accurate determination of key parameters. This is true for both modelling applications and for selection of materials. Good scientific and engineering insight is worth many gigaflops of computation.



      Reference Material:
      The CMS system is focused on mechanical properties. For non-mechanical properties the VISTA server of the Institute of Microelectronics is a good starting point. Their approach to materials data bases differs substantially from that of CMS. If you are interested , click on the link below and explore.
      http://h50.iue.tuwien.ac.at:8001/vistab11/node94.html

      The NIST virtual library is a good starting point if you are interested in precision data and the structure of materials data bases. NIST is the lead agency trying to standardize the formats of materials data bases and to automate them. Click below for more information
      http://nvl.nist.gov/

      Rumours to the contrary , all software and materials data base activity doesn't occur in the US . A highly regarded object oriented data base is being developed at a research center in Japan (Tohuku University). Their motivation is materials data and models for advanced manufacturing, and their page is a good source of materials database activity.
      http://mood.mech.tohoku.ac.jp/index.html

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       Last update 10-10-98