Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
The midsemester quiz for the aerospace materials laboratory (ase 224l) course held in spring 1993. The quiz covers various topics related to materials testing, phase diagrams, and material behavior under different conditions. Students are required to answer questions related to choosing the appropriate load cell for tensile tests, determining elastic behavior, calculating material toughness, identifying phases in the iron/carbon phase diagram, and discussing deformation mechanisms. The quiz also includes questions about the atomic packing structure of different phases and the strengthening mechanisms of certain materials.
Typology: Quizzes
1 / 5
This page cannot be seen from the preview
Don't miss anything!
This is a closed book exam. There are four questions to be answered. The number of points assigned to each question is shown in [ ].
Section: T W Th (Circle One)
(a) You have a choice of a 50 kN or a 100 kN load cell with which to conduct tensile tests to failure. Indicate, with quantifiable explanation, which one you would choose.[2]
(b) Determine the displacement range that a diametrical extensometer would have in order to capture the complete elastic behavior of the material. [4]
(c) Determine the toughness of the material if the stress/strain response was bilinear with a change in slope at the yield point and the ultimate tensile strength occurred at the failure strain. [3]
(d) Could the strength of the alloy be improved by cold working? Explain your answer by referring to dislocation-based models of plastic deformation. Indicate how it is that dislocations can cause strain hardening. [6]
(a) Identify which deformation mechanisms are dominant for the range of conditions given above. [2]
(b) Discuss the experiments you would need to conduct and the data reduction required in order to determine the constants A, α and the stress exponents for the secondary creep rates, ˙ε (^) s. [4]
(c) Explain why it would be advantageous to operate at lower stress levels rather than different temperatures. Determine the difference in rupture times from operating at the two extreme stress levels to assist your explanation. [4]
Plastic Flow
Elastic
Dislocation Creep
Diffusional Flow
Bulk Diffusion
Boundary Diffusion
5 - α/T
log σ/G
(b) The combination of springs and dashpot shown below is used to represent the creep of a polymer. Show that the differential stress/strain law for the material is
d ε dt
σ η
kg
d σ dt
(c) The creep of the model developed in (b) due to a constant stress, σo, is
ε ( t ) = σ o kg
Determine the creep compliance of the material and explain whether or not this represents a thermoset material. [2]
k
k η g
