Question

1. Fatigue equations are based solely on theoretical assumptions. Experimental data is only used to verify the theory. a. True.b. False.2. While most steels have a well‐defined endurance limit, both aluminum and titanium do not—they will both eventually fail at even the lowest alternating stress levels. a. True.
b. False3. The mean, or midrange, stress is the average of the maximum and minimum stress in a cycle. a. True.
b. FalseThe alternating, or amplitude, stress is the stress range from peak to valley, i.e., the difference between the maximum and minimum stresses.a. True.
b. False
4. Low‐cycle fatigue is defined as less than 103 cycles and high cycle fatigue is between 103 and 106 (or 107).a. True.
b. False5. Fatigue analysis for brittle materials is better‐defined and can be more generally applied than fatigue for ductile materials. a. True.
b. False6. Torsional fatigue is handled in the same manner as bending fatigue with the appropriate modifications to the ultimate and yield strengths. a. True.
b. False7. S‐N diagrams are based on fluctuating stresses but can be modified for reversible stresses. a. True.
b. False8. The Strain‐Life method for predicting fatigue failure is more accurate than the Stress‐Life method, but is more difficult to analyze. a. True.
b. False9. The Linear‐Elastic Fracture Mechanics method is based on the assumption that initial cracks do not exist in materials, and predicts fatigue failure when a crack initiates.a. True.
b. False

Answer 1

Answer:

1.  b. False

2. b. False

3.  b. False

4.  b. False

5. a. True

6. a. True

7.  b. False

8.  b. False

9. a. True

Explanation:

1. The fatigue properties of a material  are determined by series of test.

2. For most steels there is a level of fatigue limit below which a component will survive an infinite number of cycles, for aluminum and titanium a fatigue limit can not be defined, as failure will eventually occur after enough experienced cycles.

3. Although there is a cyclic stress, there are also stresses complex circumstances involving tensile to compresive and constant stress, where the solution is given into the mean stress and the stress amplitude or stress range, which is double the stress amplitude.

4. Low‐cycle fatigue is defined as few thousand cycles and high cycle fatigue is around more than 10,000 cycles.

5. The number of cycles for failure on brittle materials are less and determined compared with the ductile materials.

6.  The bending fatigue could be handled with specific load requirements  for uniform bending or axial fatigue of the same section size where the material near the surface is subjected to the  maximum stress, as in torsional fatigue, which can be performed on  axial-type specially designed machines also, using the proper fixtures if  the maximum twist required is small, in which linear motion is changed to rotational motion.

7.  A SN-Curve for a given material, is a plot displayed on logarithmic scales of the magnitude of an alternating stress in relation to the number of cycles to failure

8. The strain life method measures the strain resistance of local stresses and strains around stress concentration that controls the fatigue life of the material. It is more accurate than determining fatigue performance as the stress-life method is for long life millions of cycles in elastic stresses, but an it gets an effective stress concentration in fatigue loading.

9. Linear Elastic Fracture Mechanics (LEFM) states that the material is isotropic and linear elastic so, when the stresses near the crack surpasses the material fracture toughness, the crack grows.