a) Describe how the constraint applied by a typical axial testing machine results in the rotation of slip planes with respect to the primary loading axis. [6 marks] b) With the aid of a schematic plot of stress versus strain, define the characteristic three stages of slip that may be demonstrated during loading of a single crystal. Describe the slip mechanisms controlling this response. [8 marks] c) Describe how the stages of slip are affected by crystal structure. [6 marks] d) Describe the difference in slip behaviour and hence strength in polycrystalline materials when compared with single crystal materials. [5 marks]