1)In the framework of visoelasticity of materials, explain what are damping phenomena during cyclic elastic loading and

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1 In The Framework Of Visoelasticity Of Materials Explain What Are Damping Phenomena During Cyclic Elastic Loading And 1 (74.88 KiB) Viewed 20 times

1)In the framework of visoelasticity of materials, explain what are damping phenomena during cyclic elastic loading and how these could be used to study structural transition in polymers using dynamic mechanical thermal analysis. 2) Explain why the condition for necking writes &= n/1-m. Explain the physical meaning of n and m and how they help postponing necking, from a physical point of view 3) Explain what are the physical reasons that led to the suggestion of the Tresca and of the Von Mises Yield criterion. In particular, show, using a drawing, that an applied hydrostatic pressure does not influence the yielding of a material obeying Von Mises. What about Tresca? 4)One can show that the strain energy of a dislocation is proportional to ub². Explain what are m and b. Be very specific regarding b, use a drawing for example. What are important consequences of this relationship regarding the mechanical behaviour of crystalline materials? 5)Explain what are partial dislocations. Why are they energetically favoured? What is a stacking fault and why is this related to partial dislocations? 6)Show that the driving force for dislocation motion submitted to a shear stress in its shear plane is equal to f=tb. What are the units off? Based on this idea, derive Schmid law in the case of the plasticity of single crystals. 7)When submitted to a shear force, a dislocation will start bowing. The radius of curvature is given by equation slide 68. Based on this equation (given), explain the Frank and Read mechanism for dislocation multiplication and the associated yield strength. Explain how you can derive the very important Taylor formula (slide 86, would be given) from this mechanism and so the dependence of the yield strength with dislocation density. 8) What is the different hardening mechanisms, explain it ?