11. Steady-state creep rate data are given below iron at 900 C. &($) 104 10-6 σ (MPa) 17 6.5 If it is known that the activation energy for creep is 248,000 J/mol, calculate the steady-state creep rate at a temperature of 950 C and a stress level of 22 MPa

The flow stress of a coarse-grained dilute copper alloy increased from 2 to 55 MPa when the dislocation density was increased from a low value of 10 cm via cold working to a modest value of 100 cm2. Calculate the flow stress for this alloy when heavy cold working introduces a dislocation density of 10¹2 cm². An equation similar to the Hall-Petch equation has been proposed for dislocations, and is: Tflow To ka Paisl where Tflow is the flow stress (i.e., the force per unit area necessary to get plastic deformation), pdisi is the dislocation density (the dislocation line length per unit volume), and To and ka are constants for a given material. The easiest way to solve this problem is to put values into this equation twice, subtract one expression from the other, and solve for ka. Then enter your value of ka into either original equation to determine To. Keep track of units, and then solve the problem stated above.

Sintered silicon nitride parts are expected to experience tensile stresses 50% of the ultimate tensile strength of the material. What will be the maximum allowable size of internal flaws for these parts not to fail in service? Given the following properties of the material: Specific surface energy: 0.3 J/m2 its Youngs Modulus: 304 GPa Ultimate tensile Strength: 570 MPa Select one: a. 1.43 µm b. 0.71 µm c. 15 µm d. 85 µm e. 9.5 µm

Estimate the theoretical fracture strength of a brittle material if it is known that fracture occurs by the propagation of an elliptically shaped surface cra of length 0.5 mm and having a tip radius of curvature of 0.005 mm, when a stress of 1040MPa is applied. Your answer must be in GPa. Write your answer to 1 decimal place. Answer: V 30 (0) 00 a W 4340 steel alloy. Determine the ductile to brittle transition