Stress-controlled testing, fatigue

SA mixes exhibit significantly higher fatigue lives than comparable conventional mixes under stress-controlled testing. 

Static fatigue tests were performed in air at elevated temperatures of 1373 K using a hydraulically controlled testing machine with an electric furnace and terminated in 100 h according to the Japan Industrial Standard (JIS R1632) The applied stress (Oq>p) at which the specimen did not fracture within 3.6 x 10 sec (100 h) was defined as the static fatigue limit (Oto) in this study. 

Crack texture was tested to determine the influence of Growth dwell time at maximijm tensile stress on the fatigue crack growth rates (see table). All of the fatigue tests were conducted using displacement-controlled constant stress intensity (iiO, in air (relative humidity not specifled), at room tempera-tvire. The Ti-6246 alloy exhibited a nominal two- to... 

The fatigue resistance of nano- and microcomposites was also compared by Mallick and co-workers [46,56]. In particular, th performed stress-controlled tension-tension fatigue tests on PP nanocomposites reinforced with 5 wt% of organoclay and on 40 wt% talc-filled PP. As reported in Figure 9.15, the S-N diagram of nanocomposites was slightly better than that of neat PP and much higher than that of talc-filled composites. 

Figure 9.15. Fatigue S-N curves of (a) neat PP, (b) PP - 5 wt% organoclay, and (c) PP -40 wt% talc. Tests have been performed at room temperature under stress-control with R = 0.1 and a frequency of 1 Hz [56]...

The machines are usually run in a force- or stress-controlled manner. This particular example includes an environmental chamber which can be used to control the temperature, humidity, and atmosphere the fatigue test will take place in. 

Stress-controlled fatigue tests and the properties generated by these tests are useful for HCF analysis where elastic strains are dominant. One... 

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