Fatigue testing specimens

Fig. 13.10 Corrosion-fatigue tests specimen sprayed with 3% sodium chloride (after Fescol...

TEM observations were performed in the as-received and deformed samples in order to reveal the effects of microstructure on the fatigue response of the studied alloy. Fracture surfaces of the deformed fatigue test specimens were comprehensively examined in a scanning electron microscope (JEOL JSM6500F) equipped with field emission gun to determine the macroscopic fracture mode and characterize the fine-scale topography and microscopic mechanisms governing fatigue fracture. 

Figure 1. ASTM constant force fatigue test specimens.

Additional striations were also observed in 3D SiC/SiC composite deformed by tension-tension fatigue, as shown in Fig. 7.54. Here, the fractured surface of monotonic tension and tension-tension fatigue results are compared. Note that the whole cross-section surface of the monotonic tension-tested specimens is coarse. On the cross-section surface of the tension-tension fatigue tested specimens, two different areas may be seen one area composed of ringed striations, taking up about half of the whole section, while the other area is smooth. 

Paper machine components other than suction rolls can experience corrosion fatigue cracking. Dorsch et al. [43] used a fuU size felt roll journal as a laboratory fatigue test specimen in simulated white waters containing thiosulfate ions. 

FIGURE 8. Fatigue test specimen for structural adhesives. 

Fig, 14. Effects of test environments air, 0.1 M NaCl, and 0.1 M NaCl with 1000 ppm CeCl3, on the cycles to failure of 7075 Al alloy fatigue test specimens, at two alternating stress levels. The hatched regions indicate scatter bands. 

Figure 1.8 Illustration of typical molded flat sheet fatigue-testing specimens, (a) Flat sheet fatigue specimen with rectangular cross-section (b) flat sheet fatigue specimen with circular cross-section.

Figure 1.17 Illustration of cantilevered fatigue-testing specimens per ASTM D671.

Horger undertook rotating-beam fatigue tests of press-fitted assemblies using specimens as large as 305 mm diameter shafts. 

Constant deflection amplitude fatigue testing is probably the less demanding of the two techniques, because any decay in the modulus of elasticity of the material due to hysteretic heating would lead to lower material stress at the fixed maximum specimen deflection. In the constant load amplitude tests, maximum material stress is fixed, regardless of any decay in the modulus of elasticity of the material. 

The fatigue strength is defined as that stress level at which the test specimen will sustain N cycles prior to failure. The data are generated on a machine that runs at 1800 cycles per minute. This test is of value to material manufacturers in determining consistency of their product (Chapter 2). 

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