Fatigue diagram

Fig.16 S-N fatigue diagram of a bulk diglycidyl ether of bisphenol (DGEBA)/isophoron diamine (IPD) epoxy polymer giving the maximum applied stress as a function of the number of cycles to failure (three-point bending, 25 Hz, stress ratio OminMnax = 0.1) (from [53]). The two dotted lines correspond to theoretical values of the amplitude of the effective tensile stress, Acr, calculated for (a) gross slip condition and (b) under partial slip condition for an imposed displacement ( 10 xm) which corresponds to the experimental contact endurance limit at 105 cycles...

As for the epoxy polymers, a quantitative comparison of the contact fatigue behaviour was attempted on the basis of an estimate of the maximum tensile stress at the edge of the contact. The coefficient of friction of the copolymers increased as the tests proceeded, with a variation which was dependent upon the level of the normal loading. As a first approach, the value of //. at crack initiation was taken into account in the calculation of a . The results are reported in a S-N fatigue diagram giving the maximum applied tensile stress as a function of the number of cycles to crack initiation (Fig. 23). These data show a marked increase in the contact fatigue resistance of the GIM copolymers compared with the MIM material. 

Fig. 1.50 Fatigue diagram obtained by Murakami and Matsuda with specimens containing cracks of different size (modified from [69])...

Fig. 1.56 Fatigue diagram for Armco iron with marked zones of different damage evolution [47]...

To ensure that blade stress levels are within the fatigue life requirements of the eompressor, it is usual praetiee to strain-gauge the blading on one or two prototype maehines, measure the stress levels, and generate a Campbell diagram showing the plotted test data. To measure data, an impeller ean also be mounted on a shaker table with a variable frequeney output (0-10,000 Hz). Aeeelerometers ean be mounted at various positions on the... 

Fig. 8.60 Schematic diagrams showing common surface profiles produced during fatigue (a) coarse slip and crack initiation adjacent to grain boundaries (b) extrusions and intrusions (c) coarse slip within a persistent slip band (after Lynch Y...

The data on which Fig. 8.74 is based are for tests carried out in carbonate well-water. McAdam made the further interesting discovery that if mild steel were tested in condenser water and a similar graph constructed, the set of contours corresponded more closely to the right-hand side of Fig. 8.74, i.e. the behaviour of mild steel in condenser water was similar to that of Monel in carbonate water. The apparent universality of this diagram is an interesting observation, but it has not provoked a basic theory of corrosion fatigue. 

Examples of fatigue curves for unreinforced (top) and reinforced (bottom) plastics are shown in Fig. 2-44. The values for stress amplitude and the number of load cycles to failure are plotted on a diagram with logarithmically divided abscissa and English or metrically divided ordinates. 

Figure 1.13 Typical fatigue curve (S-N diagram for a material having an endurance limit, oe).

Figure 13.29 A diagram summarising three possible mechanisms for central fatigue. It is possible that all three mechanisms could occur simultaneously, giving rise to severe fatigue.

Figure 13.30 A summaiy diagram illustrating the mechanisms by which central and peripheral fatigue can cause fatigue. Central fatigue could be caused by changes in concentration of blood glucose, 5-HT or lumaine concn. in presynaptic neurones.

Figure 5.104 Fatigue S-N diagram for SMC-R65 composite. Reprinted, by permission, from Composite Materials Technology, P. K. Mallick and S. Newman, eds., p. 52. Copyright 1990 by Carl Hanser Verlag.

The occurrence of irreversible fatigue phenomena and grain-size effects indicates that important features of the SMA phenomenon lie outside the domain of equilibrium thermodynamics. Nevertheless, details of the SMA T-x (and T-P-x) phase diagram are clearly important for the understanding and engineering of this curious thermal effect. 

Figure 13.11 Paris diagrams for fatigue crack propagation of polyldimethyl-siloxane)-modified epoxy networks. (Rey et a/., 1999 with kind permission from Kluwer Academic Publisher.)... 

Figure 6.2. Schematic diagram of probable mechanism of plastic fatigue wear (from Briscoe and Evans, 1987) (a) Formation of plastically deformable grooves in series (b) Deformation of the grooves pushed in one direction (c) Sway back to the opposite direction (d) Deterioration of ridges after repeated fluttering (e) Detachment of ridges in the form of band-shaped debris.

Figure 6.69 Venn diagram illustrating the interrelationship among stress corrosion, corrosion fatigue, and hydrogen embrittlement R — ratio of minimum stress to maximum stress (Phull)5...

Fig. 6.6 Fatigue life diagram for the tension-tension fatigue of unidirectional SiCf/Si3N4 at 1000°C and a stress ratio (o /cr, ) of 0.1. Fatigue run-out (5 x 106 cycles) was observed when the maximum stress was below apt. After Holmes et al.43...

Fig. 6.7 Fatigue life diagram for the tension-tension fatigue of unidirectional SiQ/1723 at room temperature (10 Hz, VmJ max — 0.1). The 106 cycle fatigue limit of 440 MPa is higher than cr. and

For the characterization of the fatigue properties of polymers and polymer composites, Wohler experiments to establish S-N diagrams are usually employed (Fig. 3). 

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