3. a. Draw the stress-strain curves for the following materials/items. (We recommend trying to put them all on the same plot for perspective, but make sure you have plenty of space.) Label the elastic and plastic regions. For each material, add the true stress- strain curve as a dotted line. The dotted line doesn't need to be super precise; you can just convert engineering quantities to true quantities for 1 or 2 points and sketch the rest. You may need to look up some published data for these materials. i. Bone (depends on whether it's wet or dry. Use dry bone.) ii. A Co-Cr alloy (often used in hip implants) ii. Polylactic acid (PLA) (note: this depends on temperature; just pick one) b. Provide a few key observations or comparisons. 4. The following equation can be used to calculate the fracture energy (Im 2) of a material: Gc= 25awo Vic tawo where 2 is the critical extension ratio, a is the notch length, and wo is the strain energy density. Ac is the point during a single-edge notch test (left graph below) where the max stress is reached and a drop in stress is seen as the gel begins to tear. This value of lc is needed to calculate the area under the curve from the stress strain curve (obtained via a regular tensile test; right graph below), from x = 0 and y = 0 until the point where x = c. Single edge notch test 3wt% tannic acid 3wt tannic acid - Stress strain curve 6 5 Wayanada keperlawanan dalam satu hal yawaluhyang Stress (kPa) tress (kPa) Stress Stress (kP 2 1 4 0 20 60 70 30 40 Strain (%) -1 0 10 20 30 60 70 80 90 40 50 Strain (%) The calculated area is the wo. a. Given this data, determine ic and calculate the fracture energy (G) of this hydrogel, which has a notch length of 1.4 mm and area under the curve (wo) of 244.91 kPa. Hint: Convert all units to base units and do not convert percentage to a fraction. b. If you increase the amount of crosslinker in the hydrogel, what do you expect will happen to lc and G? Why? Assume that a and wo remain constant