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Which of the following factors are affecting critical shear stresses? 1. Purity of metals reduces the critical shear stress 2. Surface films greatly enhance the critical shear stress 3. Rise in temperature 4. Rate of deformation and the extent of initial deformation also help in raising the critical shear stress

Which of the following factors are affecting critical shear stresses? 1. Purity of metals reduces the critical shear stress 2. Surface films greatly enhance the critical shear stress 3. Rise in temperature 4. Rate of deformation and the extent of initial deformation also help in raising the critical shear stress Correct Answer 1 ,2, 3 and 4

Critical Shear Stress – The shear stress needed to cause slip in a given direction along a given crystallographic plane of the single crystal. Critical shear stress in constant for each material.

Factors Influencing critical shear stress:

  • The rate of deformation and the extent of initial deformation will also raise critical shear stress.
  • Purity in metals reduces the critical stress.
  • Surface effects like surface films greatly increase the critical shear stress
  • Temperature increases thermal mobility and hence decreases the critical shear stress.
  • In polycrystalline metals, slip takes place in the preferred directions.
  • Alloy or solid solution increases the critical shear stress.

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