Service life fatigue effects

The presence of internal stresses in coatings is of importance because of their effect on service life (e.g., corrosion resistance, fatigue properties) [44]. Stresses may arise from the following ... 

Fatigue tests can be peifonned under a variety of loading conditions as specified by the service reqnirements. Thermal effects and the presence or absence of cracks are other variables to be considered when the fatigue life of a material is to be evaluated. 

Up to 40% of all aircraft tyres have to be taken out of service on account of mechanical damage. Up to now there has been practically no analysis of the effectiveness and level of reliability of tyres with widened tolerances in respect of mechanical damage, and this has led to a study of the fatigue life and service life and service reliability of such tyres, leading to considerable financial savings. 4 refs.Translation of Kauch.i Rezina, No.4, 1992, p.l2 RUSSIA... 

Synergistic degradation effects can also lead to early joint failure. Fatigue causes faster crack growth than do steady-state stresses. Mechanical stress in combination with environmental stresses like standing water, heat, ultraviolet light, acid rain, ozone or solvents can reduce service life many fold. 

In 2002, an experimental test was conducted on the FRP-reinforced pipes by Meniconi et al. (2002). These tests were verified with finite element analysis (FEA) and showed that overwraps only take part in carrying the loads after steel yielding. Kessler et al. (2004) did some investigations on an FRP with the trade name Diamond-Wrap . They did two tests on the repaired pipes the first was to smdy the effectiveness of rapier on pipes with different depths of axisymmetric defects. It showed an almost 140% increase in the burst strength. The cyclic fatigue pressure teshng was the second test performed in this study the results revealed a considerable increase in the service life of the repaired pipes. 

Service tests characterize the performance of materials in specific applications and should mimic the environment of the actual application as much as possible. This includes simulating the chemical composition of the atmosphere, the temperature and thermal cycle profiles, stress states, fatigue conditions, and design. These tests may be accomplished by exposing test racks to actual service conditions or through the use of prototype apparatus designed and constructed to duplicate the end-use application. Additionally, laboratory service tests designed to evaluate the effect of one or more critical aspects of the exposure conditions may be employed. Service test data enable one to determine failure mechanisms, component or material life, or to screen materials for an application. 

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