Fatigue Life Calculation

An important step in local strain fatigue analysis under irregular variation of load with time, as schematized in Fig. 6.16a, is the knowledge of the local notch strain-stress history, as shown in Fig. 6.16c. This, in turn, necessitates the knowledge of the cyclic stress-strain characteristic of the material (see Sect. 1.3.1). Advanced elastic-plastic analysis technique such as finite element computer code is needed or it can be used a simplified Neuber s rule as described in the next section. 

Once the elastic-plastic response is known, Fig. 6.16c, using Eqs. (6.6) and (6.7) and the memory effect each hysteresis loop of Fig. 6.16d can be separately analyzed. In using Eqs. (6.6) and (6.7) it must be recalled what has been said in Sect. 6.2 about the Masing hypothesis and the factor of two that must be applied to handle the case as if the hysteresis loop traces were equivalent to a cyclic stress-strain curve. Therefore, Eqs. (6.6) and (6.7) becomes 

6 Strain-Based Fatigue Analysis Low Cycle Fatigue 

The global effect may be obtained using the Patmgren-Miner rule (see Sect. 8.3.1) 

Furthermore, for repeating load time history it must be 

---

Fatigue life calculation of SLS is given as follows stroke available in fatigue testing machine, 0-200 mm initial deflection of SLS, 100 mm initial stress (measured by experiment), 420 MPa final deflection of SLS (camber), 175 mm maximum stress in the final position (measured by experiment), 805 MPa. Fatigue life cycles predicted for SLS is less than 10,00,000 cycles (Fig. 8) by the procedure outlined in (SAE manual,1990). 

Gothenburg, 9th-12th May 1995, Paper E4, pp.I4. 012 FATIGUE LIFE CALCULATIONS FOR ELASTOMERIC ENGINEERING COMPONENTS... 

The most important statistical subjects relevant to reverse engineering are statistical average and statistical reliability. Most statistical averages of material properties such as tensile strength or hardness can be calculated based on their respective normal distributions. However, the Weibull analysis is the most suitable statistical theory for reliability analyses such as fatigue lifing calculation and part life prediction. This chapter will introduce the basic concepts of statistics based on normal distribution, such as probability, confidence level, and interval. It will also discuss the Weibull analysis and reliability prediction. 

Fatigue Life Calculation with Local Stresses and Local S/N-curves... 

One of the main aims of a big research project in our group is the generation of a comprehensive database which is necessary for the applicability of fatigue life calculation with local S/N curves for fiber reinforced composites. In this work the effect of fiber orientation and concentration as well as stress ratio R on fatigue behavior of two materials was investigated. The stress Ratio R is defined by equation 1, where a is the lower stress amplitude and CTq is the higher stress amplitude of a sinusoidal loading. 

For fatigue life calculation using the FEMFAT concept which is based on finite element results, the knowledge of local S/N-curves is necessary. The... 

Fatigue Life Calculation, short-glass-fiber reinforced polymer, fiber orientation, S/N-curve... 

Figure 1. Schematically graphic of fatigue life calculation based on local S/N curves. [1]...

If anything, the equal area method tends to over-estimate the compensation required and in some instances the additional material can reduce the fatigue life of the vessel. More sophisticated methods for determining the compensation required have been introduced into the latest editions of the codes and standards. A critical discussion of the methods that are used in the various national codes and standards for calculating the compensation for openings and branches is given in the British Standards Institute publication PD 6437 (1969) and PD 6550 (1989). 

Sample Calculation. For illustration, the fatigue life for a high-strength steel plate containing a semicircular flaw may be used. For this case, = 7t/2. Taking... 

Here the basic model used is one which is tested hi the laboratory and contains as much as is known about the influences of the X and Y parameters on the fatigue life. The known variabilities of the X and Y in the WOL are then used to calculate a fuzzy probability of failure which is the chance that the actual life will be less than the design life. A fuzzy logical hierarchy is then set up exactly as in the example of Section 10.5, to allow for the uncertainty associated with the application of the model in the laboratory. This new fuzzy probabUity is then again truth functionally modified to allow for the uncertainty of the matching with the WOL The procedure would then be exactly as for that example, so that a fuzzy truth restriction upon the statement, the structure is perfectly safe would result and this is the final measure of structural safety. 

Figure 29 Comparison of experimentally obtained and calculated fatigue life in P355N (StE 335, 1.0545, cf UNS KOI600) [73]...

The acquisition of analytical techniques and practical skills in the engineering sciences is important to the design system. Through a study of engineering of any label based on mathematics and physics applied through elemental studies, one acquires an all-round engineering competence. This enables, for example, one to calculate fatigue life, creep behavior, inertia forces, torsion and shaft stresses, vibration characteristics, etc. 

By formula (15), (17) and (7) the maximum likelihood function parameters m and can be obtained. According to formula (11) the fatigue life under different stress levels in any survival rate can be calculated properly. 

---