Papers by Keyword: Fatigue Test

Abstract: This study discusses the performance and durability of manganese steel wire ropes under different loading conditions and environmental exposures. Steel wire ropes are critical elements in several industries that require high tensile strength and elasticity. It is driven by the fact that these ropes fail prematurely within two years of service despite them being designed for five years during the process of fabrication. The nature and cause of these premature failures can be attributed to residual stresses, which increase the wear, fatigue, and corrosion. These tests included tensile testing at various strain rates in both the aged and unaged states, and fatigue testing performed under a 0.7 strain rate in a purely non-pre-strained state, and pre-strained under the three conditions of dry pre- strain, corrosion pre-strain, and aging pre-strain. An SEM analysis was performed to determine the failure mechanism. An increase in the strain rate reduced the lifespan but increased the yield and ultimate tensile strength; the 0.7 strain rate represented the highest energy density compared to the strain rates of 0, 0.43, 1.0 and 1.35 strain rate. This study highlights the critical role of residual stress in steel wire ropes in terms of their performance and lifetime. The residual stress increased with the strain rate. Corrosive conditions showed a drastically reduced fatigue life, and the non-pre-strain condition had the longest cycles. Understanding the mechanical effects of steel wire ropes and optimizing the testing conditions will increase the durability and reliability of steel wire ropes with reduced maintenance costs and increased safety in industrial applications.

Abstract: The subject of the study presented in this paper is to quantify the effect of fiber content on the mechanical and mainly fatigue response of fine-grained cement-based composites. The reference cement-based composite was without fibers. Three types of fibers were used as dispersed reinforcement: tire cords (waste material), steel, and polypropylene. For each type of fiber, mixtures with varying reinforcement levels per volume were prepared: 0.0 % (reference composite), 0.5 %, 1.0 %, and 1.5 %. Prismatic specimens 40 mm × 40 mm × 160 mm were prepared and tested. A total of 10 composite variants were investigated. The ages of the specimens for the static three-point bending tests were 28 days, for the compression tests were 28, 120, and 275 days. While for the fatigue tests, it was approximately between 110 and 180 days. The obtained compressive strength values for the above-mentioned composite ages were approximated by a selected exponential function and the results of the fatigue tests were standardized to a nominal age of 28 days using them. All used types of reinforcement increase the strength values of the composites even from the lowest fiber doses. A positive effect of fiber dosage above 0.5 % on the fatigue behavior of composites was shown only in the case of reinforcement with commercial steel fibers.

Abstract: The effect of angle abutment on the stress distribution of bone tissue around implant is not clear. Using abutments with different gingival height (GH) may cause changes in the stress distribution of the implant and implant-bone interface. This study aims to investigate whether angled abutments with varied GH have a significant effect on stress distribution of surrounding bone and the biomechanical behavior of the implant system. Three implant-supported restoration models were designed by changing the angled abutment GH (1 mm, 3 mm and 5 mm). Force of 200N was applied on the crown surface at 45° to the long axis of the implants. The biomechanical performance of the restorations (including implants and angled abutments) and stress distribution pattern were evaluated by finite element analysis (FEA). Results showed that angled abutments with larger GH resulted in increased stresses on the implant and implant-bone interface.

Abstract: In an initiative to reveal the property of welded joint, investigation and assessment of the welding parameters in friction stir spot welding (FSSW) was carried out. In this study, the AA5052-H112 sheets with 2mm thickness was welded using cylindrical tool pin profile under different combinations of main process parameters i.e. spindle speed, tool depth, and dwell time. The fatigue test under cyclical load condition was performed to investigate the dynamic behavior of the welded joint. Failure mode analysis on the fracture of the weld joint after fatigue test was took also consideration. Finally, results from the test were evaluated using analysis of variance (ANOVA) to deter-mine statistically significant factors and associated percentage contribution together with the generation of main effects plots. From ANOVA results, dwell time had the highest influence on fatigue load with a PCR of 52.8%, followed by the spindle speed 37.1%, and then tool depth 6%.

Abstract: The fatigue tests were carried out under two kinds of hole-making technology, forming EDM and high-speed EDM. The hole taper and fracture surface of the sample were compared and analyzed. The finite element model with hole taper was established and the influence of the hole making technology on fatigue life was analyzed. Three conclusions have been obtained:First, the inner surface of the hole of the formed EDM is relatively flat, the residual deposit formed during the processing is less. and thickness of the recast layer and the content of oxygen are also lower than the high-speed EDM. Second,The fracture surface of the formed EDM shows obvious crack source, while the high-speed EDM has no crack source, and the area of the crack propagation area of the high-speed EDM is obviously larger. Third,the high-speed electric spark machining has obvious taper, under the load condition, the stress at the large hole end is higher than that at the small hole end, and large strain and damage are generated at the same time, resulting in crack initiation at the end of the large hole.

Abstract: Aiming at the damage and failure problem of copper alloy netting structure, the ultimate strength and fatigue performance of the net structure were studied by test method. Based on the research on the ultimate strength of copper wire, through a series of fatigue tests on copper wire and net structure, the fatigue life and failure modes of copper wire and net structure under different loads are analyzed, and their fatigue life curves are also drawn. The results show that the fatigue strength of copper wire and net structure considering corner processing is lower than that of copper wire not considering corner processing, which indicates that corner processing has a great influence on the fatigue strength of actual copper net structure. Compared with the fatigue strength value of 32.8 MPa of the copper net, the fatigue strength value of the net structure decreases to a certain extent (about 14.3%), which indicates that the assembly process of the copper net has certain influence on the fatigue life of the net structure.

Abstract: The carbon fiber reinforced polymer composite are widely used in industry as major structural materials. They represent the greatest interest for the production of gas turbine engines parts because of their high specific strength. But before adaptation these materials into the structure, it is necessary to conduct a number of tests, both on test coupon and on structurally equivalent samples for determining physical, in particular, fatigue properties of these materials. However, the high cost of manufacturing coupons for such tests has a negative impact on the adaptation of carbon fiber reinforced polymer composite into the composition of final products. In this paper it is presented a method for fatigue tests of test coupon and structurally equivalent samples of carbon fiber reinforced polymer, aimed at reducing the consumption of coupons which are necessary for obtaining fatigue properties. Based on the developed method, a series of carbon fiber coupons was tested and the fatigue limit was obtained. At the same time, the use of coupons was minimized.

Abstract: In work the analysis of influence of structurization and nonmetallic inclusions on regularity of change of growth rate of a fatigue crack in different zones of a welded seam of steel X65 is carried out. Welded seams of the pipelines received by a combined method of welding of STT+API were investigated. Growth rate of a fatigue crack low in a root of the seam received when welding in the way STT. On border of the fatigue crack passing in the filling layers of a welded seam the inclusions which are settling down chains on borders of grains are found, being concentrators of tension.

Abstract: Existing scientific research and engineering practice have shown that the proper use of mineral admixtures can improve both the mechanical behavior and the durability property of concrete structures, but due to lack of necessary fatigue test basis, the use of mineral admixtures is strictly limited in railway bridges in China. Pre-stressed concrete T-beams with different dosage of mineral admixtures were prepared and then were subjected to fatigue test and failure test. It is found that these beams have good stiffness and ductility, which means excellent fatigue resistance within a certain dose range. By a suitable mix design, concrete with mineral admixtures can be applied to railway bridge construction.

Abstract: From the viewpoint of engineering, fatigue is an important issue as most of the mechanical failures are associated with fatigue damage. In fact, these disastrous events had occurred unexpectedly during the regular working conditions and most of the time the applied stresses are well below the yield strength of the material. Thus, it makes the prediction of fatigue damage a challenging task in the field of engineering, especially when the manmade structures and machines are getting more complex than before. Even though fatigue has been studied extensively in the past 170 years, many limitations are still being found within the current fatigue analysis, testing and the non-destructive inspection. Hence, there is a great need to develop a precise and yet efficient inspection technique in quantifying the fatigue cracks. Therefore, the objective of this study is to develop a quantifiable approach in monitoring the fatigue cracks using digital image correlation technique. This can be achieved by using a developed two-dimensional sub-pixel accuracy deformation measurement algorithm which determines the deformation parameters of the first-order shape function of a material subjected to cyclic loading. Next, fatigue tests for samples made of mild steel (Grade: JIS G 3101 SS400) were conducted in accordance to the ASTM E466. Simultaneously, an industrial grade camera was used to capture the fatigue crack’s region at a specific interval until the sample broke into two pieces. The captured images were then analysed and the deformation parameters such as translations, normal and shear strains values were determined by using the developed digital image correlation algorithm. Based on the determined deformation patterns, a specific trend was observed throughout the graphs of respective deformation parameters against the number of cycles. Besides, drastic changes were observed when the average number of cycles was approaching 95.5% (min. loading) and 93.8% (max. loading) of the total fatigue life. In conclusion, the digital image correlation technique was proven to be capable in monitoring the severity of a fatigue crack and the proposed monitoring system would serve as an inspection technique in examining the fatigue damage of a structural component throughout its operational period.