MIT 3 032 - Plastic deformation from the micro- to nanoscale (4 pages)

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Plastic deformation from the micro- to nanoscale



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Plastic deformation from the micro- to nanoscale

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Pages:
4
School:
Massachusetts Institute of Technology
Course:
3 032 - Mechanical Behavior of Materials

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3 032 MECHANICAL BEHAVIOR OF MATERIALS FALL 2007 LABORATORY EXPERIMENT 3 Plastic deformation from the micro to nanoscale PreLab Questions 1 Name 2 ways in which instrumented indentation is different from uniaxial mechanical testing of materials 2 Explain the physical meaning of a material s hardness in words I Introduction There are several examples in materials engineering in which materials are available only in small volumes either because they result from new expensive and difficult processing techniques or because they are designed intentionally to be small in one dimension An example of the latter is a thin film or structural coating In such cases mechanical properties cannot be quantified easily through uniaxial force displacement testing of structures e g Laboratory Experiment 1 or stress strain responses of macroscale materials e g Laboratory Experiment 2 One alternative is mechanical testing based on three dimensional contact between the sample surface and a rigid probe of known geometry and mechanical properties In this experiment you will analyze the contact response of several classes of materials via the simple but widely used approach of microscale hardness testing as well as the more quantitative instrumented indentation testing at the nanoscale We analyze the data from such experiments using concepts from contact mechanics In hardness testing a probe such as a cone shaped diamond is pushed into a flat well polished sample surface to a specific maximum load held for a specified duration and then retracted from the surface Figure 1 Hardness Plastic deformation results in a mark indentation for Vickers indentation in the surface and square pyramid measurement of the size of that mark indenter geometry Ares is determined by measuring indicates the material hardness which is the indentation diagonals defined as Image removed due to copyright restrictions Please see H Pmax Ares 1 http www imagemet com images hardness2 Result jpg where Pmax is the maximum



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