Fatigue life analysis

Mars, W.V. et al.. Fatigue life analysis of an exhaust mount, in Constitutive Models for Rubber IV, Austrell, K., Ed., Swets Zeiflinger, The Netherlands, 2005, 23. 

Figure 17. Pavement test sections used in fatigue life analysis...

Discussion of Results. The results of the relative fatigue life analysis of the four pavement sections are given in Table X. The analysis indicates that the 12-in. asphaltic concrete pavement (System 1) and the 1%-in. sulfur-asphalt over 10-in. asphaltic concrete base (System 4) were not able to withstand the 106 passes of an 18-kip axle load. For System 4, the iy2-in. S-A-S surfacing was adequate, but analysis indicated that... 

Fig. 8.38 General procedure fra- fatigue life analysis of a wide-band time history...

For the calculation of the stress distribution in geometrically complex components, the finite element method, Irequently under the assumption of a linear elastic materials behavior, is widely used. If the results of these finite element calculations are used for a fatigue life analysis, the local strength has to be considered. For the assessment of finite element results, with regard to its fatigue strength, the application of the concept of local stresses offers a solution Local S/N-curves are calculated. 

The manner in which the laminate design is approached can be expressed in flow-chart form as in Figure 7-59. There, some initial laminate is arbitrarily selected to start the procedure. Then, the laminate load-deflection behavior is evaluated by use of the laminate strength analysis procedure described in Section 4.5. That evaluation is theoretical in nature. The next step is to evaluate the laminate fatigue life, and that evaluation can only be done experimentally, although progress is... 

Mars, W.V. and Fatemi, A., Analysis of fatigue life under complex loading revisiting Cadwell, Merill, Sloman, and Yost, to be published in Rubber Chem. Tech. 

As pointed out by Britton (15), the measurements are useful in design and research studies pertaining to (1) vibration analysis of structure, (2) propellant viscoelastic behavior, (3) oscillating combustion, (4) internal attenuation of shock waves, and (5) fatigue life. 

The thin-wall bellows element should be designed for membrane stresses to conform to code-allowable stresses. The sum of membrane and secondary bending stresses should not exceed 1.5 times the yield stress in order to prevent the collapse of the corrugations caused by pressure. Bellows subjected to external pressure can be analyzed in a manner similar to a cylinder, utilizing an equivalent moment of inertia. The fatigue life can be estimated based on the sum of deflections and pressure stresses as compared to S/N curves based on bellows test data or using the curves in B31.3 Appendix X, Metal Bellows Expansion Joints. Formulas for the stress analysis of bellows are available in the Expansion Joints Manufacturing Association (EJMA) Standards (37). 

SNL (Sandia National Laboratories). 2000. Explosive Destruction System Fatigue/Life Cycle Analysis. Albuquerque, N.M. Sandia National Laboratories. 

If NDI techniques can detect initial cracks as small as 10 in., then using Ui = 10 in., the estimated resulting fatigue life would be about 5 x 10 cycles. If, on the other hand, the initial crack size must be estimated from proof testing, say at 150 ksi, the assumed initial crack size for use in the fatigue analysis must be equal to the critical size for the proof stress (cr r), Eqn. (7.14). 

Preliminary layered elastic analysis indicates that fatigue life of S-A-S at low-to-moderate rates of loading is better than asphaltic concrete and relatively equal at high rates. 

Several critical plane analysis methods have been independently proposed and studied in the last decade (Mars, 2002 Mars and Fatemi, 2006a,b Saintier et al., 2006a,b Harbour et al., 2008b Andriyana and Saintier, 2010 Zine, 2011 Ayoub et al., 2012). They are noteworthy for their ability to provide a detailed and accurate account of the effects of multiaxial loading on fatigue life, and for their ability to predict the plane in which cracks will develop. 

---