Papers by Keyword: Fatigue Limit

Abstract: Smooth and notched specimens of a wrought nickel-base superalloy GH4698 were subjected to high cycle fatigue (HCF) loading at room temperature and 650°C in ambient atmosphere. The experimental results show that the fatigue strength decreased with the increasing of temperature and cyclic stress, and fatigue limit of notched specimens was lower than that of smooth specimens. The fracture surface presents typical characteristics of fatigue fracture, where both stage I and stage II crack propagation can be found. For the smooth specimens, the single primary crack initiated on the surface or subsurface, while multiple primary cracks initiated on the surface for the notched specimens because of local stress concentration.

Abstract: This work has carried out on Type 316L stainless steel of hollow bar specimen. The aim of this work is to determine the fatigue life prediction using Finite Element Analysis (FEA). The simulation performed by applied the different stress level to predict the stress of operation to measured life at the measured of operation stress. The simulation emphasis is focused upon the importance of characterize the fatigue limit with compared to data experimental. Comparison of fatigue limit between both simulation and experiment is 150 MPa and 161 MPa, respectively which will provide good agreement in terms of accuracy prediction even various aspects should be taken into account in simulation.

Abstract: This paper is devoted to the initiation of fatigue crack in Armco iron from low cycle fatigue to gigacycle fatigue. It is shown that the basic mechanisms of initiation are very similar from a physical point of view: PSB and Grain boundary cracking. But the mechanical aspect is specific in LCF and in GCF.

Abstract: PSB formation and its relevance for an eventual fatigue limit of polycrystalline electrolytic copper was studied in the very-high cycle fatigue regime with the ultrasound fatigue loading method. PSBs are formed at much lower stress/strain amplitudes than reported in earlier literature, if a high enough number of cycles is applied. Fatigue fracture takes place at approximately 50% higher amplitudes than needed for PSB formation, which is likewise in contrast to former literature results. Non-propagation of small cracks, originating from intrusions or PSB-induced non-propagating grain-boundary cracks are made responsible for this different material response.

Abstract: Selective laser melting (SLM) is a relatively new additive manufacturing (AM) technology which uses laser energy for manufacturing in a layered pattern. The unique manufacturing process of SLM offers a competitive advantage in case of very complex and highly customized parts having quasi-static mechanical properties comparable to those of wrought materials. However, it is not currently being harnessed in dynamic applications due to the lack of reliable fatigue data. The manufacturing process shows competitive advantages particularly in the aerospace and medical industry in which Ti-6Al-4V is commonly used, especially for high performance and dynamic applications. Therefore, in this exploratory research, high cycle fatigue (HCF) tests were performed for as-built, polished and shot-peened samples to investigate the capability of SLM for these applications. As-built samples showed a drastic decrement of fatigue limit due to poor surface quality (R_a ≈ 13 µm) obtained from the SLM process. Polishing improved the fatigue limit to more than 500 MPa, the typical value for base material. The effect of shot-peening proved to be antithetical to the expected results. In this context, fractographic analysis showed that very small remnant porosity (less than 0.4%) played a critical role in fatigue performance.

Abstract: In the present study, scatter behavior of fatigue limit for the die-cast magnesium alloy AM60B was investigated. Twelve fatigue limits were determined based on S-N curves obtained according to the standard fatigue test methods (that is based on the 0-2 or 0-1-2 combinations). The scatter of fatigue limit for the die-cast material was large where the values of Weibull modulus and COV were 16 and 6.8, respectively. This value of COV was in agreement with that obtained by simulated staircase method. The scatter of fatigue limit in the die-cast magnesium alloy was comparable to those in the die-cast aluminum alloy. In the die-cast materials, the fatigue limit determined based on S-N curve should be taken into account to have 6-10% of scatter from the mean value.

Abstract: Fatigue properties of the newly-formed and served canopy PMMA, which was applied in a certain airplane, were studied by experimental method. In order to gain the fatigue strength in the designated life, experiments based on up and down method had been conducted. The S-N curves of the PMMA were acquired based on three-parameter exponential function. Fatigue properties of the canopy PMMA in the two different condition of service were discussed. The results of analysis showed that fatigue properties of the served PMMA did not decrease significantly compared to the newly-formed PMMA.

Abstract: In order to evaluate the fatigue endurance for an ultra lightweight inline skate frame, FEM analyses was performed. The tensile properties and an S-N curve were determined through tensile and fatigue tests on a modified Al-7075+Sc alloy. The yield and ultimate tensile strengths were 553.3 MPa and 705.5 MPa, respectively. The fatigue endurance limit of this alloy was 201.2 MPa. To evaluate the fatigue endurance of the inline skate frame, the S-N data were compared with the stress analysis results through FEM analyses of the frame. The maximum von Mises stress of the frame was determined to be 106 MPa through FEM analysis of the frame, assuming that the skater weight is 75 kg. Conclusively, on the basis of the fatigue limit, the inline skate frame has a safety factor of approximately 2.0.

Abstract: 15CrMo steel is widely used in engineering. In order to evaluate the fatigue performance of 15CrMo, axial loading for 15CrMo specimen has applied by high frequency fatigue testing machine under stress ratio R=0.1 at room temperature, the linear S-N relationship has obtained by grouping fatigue test, the fatigue limit has obtained and compared by two different fatigue limit analysis method. The consequences of this test could provide a theoretical support for the use of 15CrMo in engineering and the research of fatigue limit theory.

Abstract: The paper presents the determination of fatigue life of 316L stainless steel at room temperature. Plenty of steel in the world has been investigated for a lot of application in the science and technology market. The mechanisms of fatigue of 316L stainless steels were studied and investigated. Fatigue tests of specimens were performed in accordance with ASTM E466-96. The fatigue tests were performed in constant load amplitude, constant frequency of 5 Hz with load ratio R=0.1. Fracture surface of specimens were examined by using Scanning Electron Microscope (SEM). The results showed that the endurance fatigue limit of 316L stainless steel was 146.45 MPa.