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Fatigue Endurance (fatigue + endurance)
Selected AbstractsExperimental evaluation of creep and fatigue behaviour for microscale solder interconnectFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2007H. LU ABSTRACT This paper presents a novel experimental study for creep and fatigue of solder-interconnects in microstructures. The strains are directly measured in the fillet area of solder-joints with a typical linear dimension of 50 ,m. An analytical approach is developed for calculating shear stress based on the shear strain measurement and the established solder constitutive relations. Also obtained is the strain-rate as well as the separated elastic, plastic and creep components from the measured total strain. The data enables the determination of the strain energy density per temperature cycle for the characterization of the solder joint creep fatigue behaviour. Case studies provide evidence for the shear dominance and the creep fatigue mechanism in thermally induced solder joint deformation in surface-mounted electronic assemblies. Though a similar trend of variation in stress,strain is found in the joints of different solders, the substantial differences in the hysteresis loop area and shape as well as in the creep rate suggest that the solder constitutive parameters should have a profound impact on the creep fatigue endurance of the joints. [source] A computerized procedure for long-life fatigue assessment under complex multiaxial loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 3 2001B. Li A computerized procedure is presented and evaluated for application examples of long-life fatigue analyses of metallic materials under complex multiaxial loading. The method is based on the stress invariants and uses the minimum circumscribed ellipse approach for evaluating the effective shear stress amplitude under complex multiaxial loading. The applicability of the procedure for handling non-proportional loading is examined through typical examples such as combined normal/shear stresses and combined bi-axial normal stresses with complex stress time histories. The effects of phase shift angles, frequency ratios and waveforms on fatigue endurance were re-analysed and compared with available experimental results from the literature. The comparison shows that the presented procedure based on stress invariants is a potential conservative engineering approach, very suitable for fast fatigue evaluation in the integrated computer aided fatigue design. [source] Mechanical and corrosion properties of spot-welded high-strength austenitic stainless steel EN 1.4318MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2008M. T. Alenius Abstract Mechanical and corrosion properties of spot-welded high-strength austenitic stainless steels EN 1.4318 2H/C1150 and EN 1.4318 2H/C850 were studied. Microhardness measurements, lap shear and cross-tension tests, corrosion fatigue tests and corrosion tests were carried out. The corrosion environment was 3.5% sodium chloride solution at +50,°C in the corrosion fatigue tests and 3.5% sodium chloride solution at ambient temperature in the electrochemical pitting corrosion tests. Stainless steel EN 1.4318 2H/C850, t,=,1.92 mm, exhibited better fatigue endurance than EN 1.4318 2H/C1150, t,=,1.2 mm, and EN 1.4318 2H/C850, t,=,1.0 mm, stainless steels did. There were no significant differences between the stainless steels of different strength levels (2H/C850 vs. 2H/C1150) in the line load range analysis of the fatigue data. High hardness gradient was found in the heat-affected zone (HAZ) of EN 1.4318 2H/C1150 stainless steels. EN 1.4318 2H/C1150, t,=,1.2 mm, stainless steels seemed to have slightly higher lap shear strength with the same nugget diameter as EN 1.4318 2H/850, t,=,1.9 mm, stainless steel. In the case of EN 1.4318 2H/C1150 stainless steel increase in the nugget diameter bigger than required 5,t did not increase the cross-tension force significantly. The pitting corrosion susceptibility of the spot-welded samples and the base materials of the steels EN 1.4318 2H/C850 and EN 1.4318 2H/C1150, t,=,1.2 mm, was investigated by measuring the corrosion current for 1 h at +100 mV versus saturated calomel electrode (SCE) in 3.5% sodium chloride solution at ambient temperature. Pitting corrosion occurred in all spot-welded samples but not in the base materials. There was a difference between the investigated steels in the location of the pits. In stainless steels EN 1.4318 2H/C850 the pits appeared around the spot weld, but in the steel EN 1.4318 2H/C1150, t,=,1.2 mm, the pits are located mainly at the spot-weld area. [source] Identification of fiber misalignment in continuous fiber compositesPOLYMER COMPOSITES, Issue 3 2003S. C. Barwick Misaligned fibers are invariably present in nominally unidirectional high-performance composites. Such misaligned fibers are known to affect key mechanical properties of the composite, such as the longitudinal compressive strength, longitudinal tensile modulus, fatigue endurance, shear strength, and delamination resistance (1). In this paper we present a method for the automated detection of large angle fiber misalignment (, > 40°) in continuous fiber-reinforced composite materials. The method relies on the application of a series of geometrical criteria based upon measurements routinely obtained during optical scanning of polished sample cross-sections. As such, the technique is ideal for the automated identification of highly misaligned fibers in large-area (, cm2) specimens that may contain several millions of individual fiber images. The criteria applied take into account the fact that prepared cross-sections of such materials contain many damaged fibers as a result of attrition during polishing. Data obtained from three pultruded unidirectional rods reinforced with continuous carbon filaments are used to illustrate the effectiveness of this method in identifying regions where large angle misalignment occurs. [source] |