Nylon fatigue data

Fig. 6.3 Typical dynamic fatigue data at 20 C and mean stress = 0 square waveform at 0.5 Hz (a) ABS, (b) polyethersulphone, (c) unplasticized PVC, (d) acetal copolymer, (e) dry glass-fibre-filled nylon 66, and (f) cast acrylic...

Fatigue data for Nylon 6 plastics are shown in Figs. 8.6-8.14. 

The data presented in Figure 19.7 were obtained on a Sonntag-Universal machine which flexes a beam in tension and compression. Whereas the acetal resin was subjected to stresses at 1800 cycles per minute at 75°F and at 100% RH, the nylons were cycled at only 1200 cycles per minute and had a moisture content of 2.5%. The polyethylene sample was also flexed at 1200 cycles per minute. Whilst the moisture content has not been found to be a significant factor it has been observed that the geometry of the test piece and, in particular, the presence of notches has a profound effect on the fatigue endurance limit. 

Figure 11.26 The relationship between AK and fatigue crack growth rates for poly(methyl methacrylate), PMMA polysulfone, PSF polystyrene, PS polyfvinyl chloride), PVC poly(2,6-dimethyl-1,4-phenylene oxide), PPO polycarbonate, PC nylon 66 and polyfvinylidene fluoride), PVp2 (49). Samples with data to the right are more fatigue resistant than on the left, because they require higher levels of stress at the crack tip to propagate the crack.

This chapter has provided a general summary of fatigue concepts, measurement techniques or methods, data presentation, and theory. It was meant to be introductory only and additional details should be obtained from the literature cited in this chapter [24-26], Chapters Styrenic Plastics, Polyether Plastics, Polyester Plastics, Polyimide Plastics, Polyamide Plastics (Nylons), Polyolefins and Acrylics, Thermoplastic Elastomers, Fluoropolymers, High-Temperature Polymers contain hundreds of plots of fatigue-related data on hundreds of different plastics. 

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