Question

Question 1 (a) List three key defining characteristics of micrograin superplasticity and draw a schematic diagram of a typical superplastic forming process. (b) Describe with the aid of diagrams, four general principles of Design for Manufacture. 141 (c) In order to estimate the strain-rate sensitivity of a superplastic alloy, uniaxial test specimens are manufactured and tested at two different crosshead velocities, with the flow stress being measured in each case, as shown in Table Q1. The initial gauge length of the specimen is 10 mm and the final length is 20 mm. Using the data provided, determine the: i) ii) iii) Final engineering and true strains True strain-rates for each case Strain-rate sensitivity Discuss the significance of strain-rate sensitivity in the super plastic forming process and especially in relation to ductility. Table Q1: Test data for superplastic alloy Crosshead velocity (mm/min) Measured flow stress (MPa) 12

Answer 1

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.*|| characteristics of micrograin superplasticity :- |i) It is a creep_phenomenon observed at temperatures at or above 0.5 of the melting point. Ilij) It is a diffusion-controlled process represented by the dimensionless equation, ÝKT = A(6386399 and D= Do-exp ) lüüs It refers to the ability of fine grained materials |(between I lem to 10 lem) to exhibit extensive neck- free elongations during de formation at elevated teme * Diagram:- ZICIT Pressurised চিতাত প্ৰষ্ঠ Part 7 I/II/IIAC