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Fatigue Experiments (fatigue + experiment)
Selected AbstractsInfluences of the Process Chain on the Fatigue Behavior of Samples with Tension Screw Geometry,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Marcus Klein To analyze the influence of the material batch, the structure of the manufacturing process chain, and the process parameters, four different material batches of the quenched and tempered steel SAE 4140 were used to manufacture samples with tension screw geometry. Five different, manufacturing process chains, consisting of the process steps heat treatment, turning, and grinding, were applied. After selected process steps, light and SEM micrographs as well as fatigue experiments were performed. The process itself as well as the process parameters influences the properties of the surface layers and the fatigue behavior in a characteristic manner. For example the variation of the feed rate and cutting speed in the hard-turning process leads to significantly different mechanical properties of the surface layers and residual stress states, which could be correlated with the fatigue behavior. The cyclic deformation behavior of the investigated components can be benchmarked equivalently with stress,strain hysteresis as well as high precision temperature and electrical resistance measurements. The temperature and electrical resistance measurements are suitable for component applications and provide an enormous advantage of information about the fatigue behavior. The temperature changes of the failed areas of the samples with tension screw geometry were significantly higher, a reliable identification of endangered areas is thereby possible. A new test procedure, developed at the Institute of Materials Science and Engineering of the University of Kaiserslautern, with inserted load-free-states during constant amplitude loading, provides the opportunity to detect proceeding fatigue damage in components during inspections. [source] Comparison of the modified three-rail shear test and the [(+45°,,45°)]ns tensile test for pure shear fatigue loading of carbon fabric thermoplasticsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 6 2008I. DE BAERE ABSTRACT The (three)-rail shear test is rarely considered for testing of fibre-reinforced composites under pure shear fatigue loading conditions because of all experimental difficulties. However, in this article, a carbon fabric-reinforced PPS is tested using a modified three-rail shear test setup. The results are compared with [(+45°,,45°)]4s tensile tests with good correspondence. All fatigue experiments were done with R= 0 and the influence of maximum shear stress and frequency is investigated. It can be concluded that an increase in maximum shear stress decreases fatigue lifetime, whereas an increase in frequency increases the lifetime. Before failure, a sudden increase in both temperature and permanent deformation could be detected. Creep tests yielded that the occurring deformation is mainly due to the fatigue loading, rather than due to creep phenomena. [source] A shear stress-based parameter for fretting fatigue crack initiationFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 7 2001C. D. Lykins The purpose of this study was to investigate the fretting fatigue crack initiation behaviour of titanium alloy, Ti,6Al,4V. Fretting contact conditions were varied by using different geometries of the fretting pad. Applied forces were also varied to obtain fretting fatigue crack initiation lives in both the low- and high-cycle fatigue regimes. Fretting fatigue specimens were examined to determine the crack location and the crack angle orientation along the contact surface. Salient features of fretting fatigue experiments were modelled and analysed with finite element analysis. Computed results of the finite element analyses were used to formulate a shear stress-based parameter to predict the fretting fatigue crack initiation life, location and orientation. Comparison of the analytical and experimental results showed that fretting fatigue crack initiation was governed by the maximum shear stress, and therefore a parameter involving the maximum shear stress range on the critical plane with the correction factor for the local mean stress or stress ratio effect was found to be effective in characterizing the fretting fatigue crack initiation behaviour in titanium alloy, Ti,6Al,4V. [source] Similarities of stress concentrations in contact at round punches and fatigue at notches: implications to fretting fatigue crack initiationFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 7 2000Giannakopoulos A linear elastic model of the stress concentration due to contact between a rounded flat punch and a homogeneous substrate is presented, with the aim of investigating fretting fatigue crack initiation in contacting parts of vibrating structures including turbine engines. The asymptotic forms for the stress fields in the vicinity of a rounded punch-on-flat substrate are derived for both normal and tangential loading, using both analytical and finite element methods. Under the action of the normal load, P, the ensuing contact is of width 2b which includes an initial flat part of width 2a. The asymptotic stress fields for the sharply rounded flat punch contact have certain similarities with the asymptotic stress fields around the tip of a blunt crack. The analysis showed that the maximum tensile stress, which occurs at the contact boundary due to tangential load Q, is proportional to a mode II stress intensity factor of a sharp punch divided by the square root of the additional contact length due to the roundness of the punch, Q/(,(b,,,a),,b). The fretting fatigue crack initiation can then be investigated by relating the maximum tensile stress with the fatigue endurance stress. The result is analogous to that of Barsom and McNicol where the notched fatigue endurance stress was correlated with the stress intensity factor and the square root of the notch-tip radius. The proposed methodology establishes a ,notch analogue' by making a connection between fretting fatigue at a rounded punch/flat contact and crack initiation at a notch tip and uses fracture mechanics concepts. Conditions of validity of the present model are established both to avoid yielding and to account for the finite thickness of the substrate. The predictions of the model are compared with fretting fatigue experiments on Ti,6Al,4V and shown to be in good agreement. [source] Corrosion fatigue behaviour of a 15Cr-6Ni precipitation-hardening stainless steel in different tempersFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 6 2000C.-K. Lin Systematic fatigue experiments, including both high-cycle axial fatigue (S,N curves) and fatigue crack growth (FCG, da/dN,,K curves), were performed on a precipitation-hardening martensitic stainless steel in laboratory air and 3.5 wt% NaCl solution. Specimens were prepared in three tempers, i.e. solution-annealed (SA), peak-aged (H900) and overaged (H1150) conditions, to characterize the effects of ageing treatment on the corrosion fatigue (CF) resistance. S,N results indicated that fatigue resistance in all three tempers was dramatically reduced by the aqueous sodium chloride environment. In addition, the smooth-surface specimens in H900 temper exhibited longer CF lives than the H1150 ones, while those in SA condition stood in between. However, for precracked specimens, the H1150 temper provided superior corrosive FCG resistance than the other two tempers. Comparison of the S,N and FCG curves indicated that early growth of crack-like defects and short cracks played the major role in determining the CF life for smooth surface. The differences in the CF strengths for the S,N specimens of the given three tempers were primarily due to their inherent differences in resistance to small crack growth, as they were in the air environment. [source] Corrosion fatigue of spot-welded austenitic stainless steels in 3.5% NaCl solutionMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2004M. E. Somervuori Abstract Corrosion fatigue and fatigue properties of spot-welded austenitic stainless steels EN 1.4301 and EN 1.4318 in 2B or 2F and 2H conditions were investigated in 3.5% sodium chloride (NaCl) solution and in air. The shear-loaded specimens were single spot overlap joints. The effect of steel grade, load, frequency, temperature and type of chloride on fatigue strength of the 1.0 mm thick steel specimens was evaluated by using the Taguchi Method®. Increase of the load, rise of temperature and lowering of the frequency accelerate corrosion fatigue of the spot-welded steel samples. Type of chloride had only a minor effect on fatigue strength. The 2B grade spot-welded steel samples exhibited better fatigue strength than the 2H grade samples of the same steels. On the basis of the results obtained by the Taguchi Method® the S-N curves were defined for the spot-welded 1.9 mm thick steels in 3.5% sodium chloride solution at 50°C. For reference the fatigue experiments were performed in air at the ambient temperature. Comparison of the results shows that corrosive environment decreases remarkably the fatigue strength of the spot-welded steels. The EN 1.4301 2H and EN 1.4318 2H steels have no distinctive difference in their corrosion fatigue strength even though they show a different fatigue behaviour in air. The microscopic investigations indicate that the fatigue cracks in the spot welds initiate from either side of the recrystallised area in the HAZ outside the spot-weld nugget both in air and in the corrosive environments. Pre-exposure in the corrosive environment seems to have no major influence on the crack initiation, because the cracks do not initiate at the heat-tinted area of the crevice where the crevice corrosion occurs. [source] | ||||||||||