MATS 322 Homework #2 Due February 16th at 11:59 pm (Submit PDF through Canvas-Gradescope) Name: Student ID #: Q1. (5 pts) Describe the step-by-step process for the hardness experiments with copper (weeks 3 & 4). Q2. (5 pts) What is the purpose of pre-annealing the copper bars at 600°C for 1 hour? Q3. (5 pts) Describe the various types of hardness testing techniques used in material testing and explain the significance of Rockwell scale F in measuring the hardness of copper. Q4. (5 pts) What is the purpose of applying a small pre-load before applying the main load in the Rockwell hardness test? Q5. (5+5=10 pts) Why does cold working change the hardness? To explain this, describe how cold working changes the internal structure of the Cu bar. Then, describe how those changes in structure affect the hardness. Q6. (5 pts) Show the calculation for finding the actual percent cold work using the posted data for the 25% cold work target value. Q7. (10 pts) Use the posted hardness data, create a 2D scatter plot between the actual percent cold work (%CW) vs. average hardness. Your plot should have nine points including 8 different amounts of cold working as well as a point for a Cu bar that has no cold work (0%CW). Each point should have vertical error bars showing the standard deviation of the hardness measurements. The error bars will be different for each point, since they come from three hardness test per %CW. For full credit, your plot should include axis labels with units, a figure number, and an explanatory caption. Use straight-line segments to connect the points rather than using a non-physical fitted function, e.g. a spline or polynomial fit generated by the graphing software you are using, where the variables do not have a physical interpretation. Q8. (5 pts) Regarding the plots you made in Q7, briefly describe two trends you can find in the relationship between cold work and hardness. Q9. (15 pts) Plot a 3D surface plot using Matlab or Excel (or any other plotting program) of Rockwell hardness test F values after annealing (in the z-axis) vs. actual %CW vs. Annealing Temperature (6 temperatures) (in x- and y-axes). You are not required to include 0%CW, because we did not anneal any bars with 0%CW. You are not required to include error bars. Include axis labels with units. Include a figure number with a descriptive caption. Q10. (5 pts) Referring to the 3D plot in Q9, describe the effect of %CW on hardness. Q11. (5+5 = 10 pts) Briefly describe the effect of annealing temperature on hardness. Why does annealing have this effect? (Describe both the driving force and the physical mechanism for the change in hardness with annealing). Q12. (5+5=10 pts) Briefly describe the effect of annealing temperature on hardness with the change in CW%. What change do you see in recrystallization temperatures?