Papers by Keyword: Fatigue

Abstract: Aiming at most of the aviation products are facing the problem of fatigue fracture in vibration environment, we analysis the structure of a bracket with ANSYS-Workbench, predict the life of the bracket by different ways, and compared with the testing result, then use the Fatigue damage spectrum (FDS) and Extreme Response Spectrum (ERS) to analysis expected results. The research not only ensure the accuracy of simulation analysis and life predict, but also make a dynamic supervision of product life process, promote the application of finite element simulation analysis in engineering practice.

Abstract: In order to improve the system reliability testing efficiency, Reliability Enhancement Testing was applied to it. Taking the spring of the mechanical system as research object, the enhancement testing technology, increasing the initial compression, was confirmed through failure mechanism analysis. Based on the virtual prototype of the system established in simulation software ADAMS, the dynamics of the spring under different stress levels were analyzed. The load spectrums are obtained under both normal and enhancement testing conditions. The static stress distribution is gotten after finite element analysis with quasi-static method in Patran. According to the load spectrums and stress distribution, the life of the spring is gained through calculation in Fatigue. Then the enhancement testing result was evaluated. The testing shows that the enhancement testing technology is able to accelerate the failure of the spring and reduce the testing time. The enhancement testing technology is feasible, and could direct Reliability Enhancement Testing in practice.

Abstract: The purpose of this study was to evaluate the effects of aqueous extract from Atractylodes macrocephala (AME) on the physical fatigue. A total of 48 mice were randomly divided into four groups of 12 mice each: control (C), low-dose AME-treated (LAT), middle-dose AME-treated (MAT) and high-dose AME-treated (HAT) groups. The mice in the treated groups received AME (50, 100 and 200 mg/kg, respectively) intragastrically (ig) and the mice in the control group received distilled water ig. After 30 days, a forced swimming test was performed and the biochemical parameters related to fatigue were examined. The results suggested that AME could extend the swimming time to exhaustion of the mice, as well as increase the liver and muscle glycogen contents, and decrease the blood lactate and blood urea nitrogen levels. These finding indicates that AME had anti-fatigue effects.

Abstract: Due to excellent mechanical properties and high working efficiency, FRP sheet has attracted significant attention from the field of strengthening in civil engineering. This paper summarizes the current achievements in the FRP strengthened reinforced concrete beams under fatigue loading. The review and discussion focuses on the development of fatigue design, the fatigue failure mechanism, reinforcement methods,and environmental effects. Finally, it puts forward the main research directions in this field in the future.

Abstract: The fundamental mechanical responses of woven CFRP (carbon fibre-reinforced plastics) test coupons subjected to static and fatigue loading were extensively carried out and results are presented in this paper. These results were then used in the development of a generalized cumulative damage model to predict static and fatigue response of a woven CFRP beam structure with an I-shaped cross section. The damage model was then applied to the beam under four-point bending to simulate the progression of failure. The results of the static response, fatigue response, fatigue life and stiffness decay predictions were compared with the experimental data. Good correlations between predicted and experimental results provide the necessary confidence in using the proposed approach.

Abstract: The leakage and fatigue characteristics of polyvinylidene fluoride (PVDF) are investigated for flexible electronics. The crystallization, frequency responses, leakage currents, current-voltage characteristics, and fatigue characteristics of PVDF film are measured using X-ray diffraction and an electrometer. Results show that a PVDF model with a resistive load exhibits high-pass filter characteristics. The frequency band of PVDF film increases with increasing resistive load and capacitance. The break frequencies for 100 kΩ, 300 kΩ, 700 kΩ, and 1 MΩ at the break frequency are 611, 207, 88, and 61 Hz, respectively. The hysteresis area of ΔH slightly increases with increasing input voltage. The leakage current of PVDF film is higher for a lower delay time under a given applied electric field. The average leakage currents for delay times of 10 and 1000 ms are 0.565 and 73.8 pA, respectively. The magnitude of the current values increases with decreasing delay time at a given drive voltage. PVDF film induced larger degradation when the number of stress cycles was increased to about 105 cumulative cycles.

Abstract: The influence of increased dislocation density; dispersity of Ni-rich (Ti₃Ni₄ and Ti₂Ni₃) particles and volume fraction of Ti-rich (Ti₂Ni) particles on the low-cycle (high amplitude) and high-cycle (low amplitude) fatigue resistance of nitinol has been considered in this paper. It was revealed that the fatigue resistance of nitinol in low-cycle conditions may be improved by increasing the part of deformation which is realized by martensitic mechanism. This part may be estimated by measuring ε_cr, which can reflect the influence of the structure parameter both on σ_M and σ_slip. It was found that in high-cycle fatigue conditions the substructure of nitinol predominantly determine its fatigue resistance, which is being the better in samples that had higher dislocation density or high dispersity of Ni-rich particles (up to 30 nm).

Abstract: Applications of the functional, smart materials SMA need a careful evaluation of the working conditions and fatigue life. Structural fatigue failure in NiTi usually comes from a surface defect inducing crack growth, and this means that fatigue has to be studied for concrete applications, with the correct samples, as the state of the material presents size effects. Testing machine experiments on Ni-rich pseudoelastic wires indicate that the main parameter controlling the fatigue life in the traction-traction experiments is the effective stress on the NiTi wire. Long wire life (in the million cycle regime) can be achieved under limited stresses (under 170 MPa) in traction-traction tests. Also, experiments have been done on thermal actuation of NiTi wire under traction at constant load. Long actuator life (larger than 400000 cycles) can be achieved at low stresses (around 100 MPa), coherently with the results from the mechanical cycling.

Abstract: The purpose of this paper is to investigate the stress concentration and fatigue of the prosthetic blood vessels. A three-dimensional finite element analysis was performed with three loading. The good man fatigue thoery was introduced for the fatigue study. As the results, the stress concentration and fatigue mode can be determined. The results prove that the mechanical property of the prosthetic blood vessels can be smiulated through the finite element analysis.

Abstract: In this article, the technology of ultrasound impacting is mentioned. The toe of 16Mn welded joints are treated by the ultrasound impacting, and the fatigue, hardness and residual compressive stress of the 16Mn welded joints are compared after treated by ultrasound impacting. The results shows that, the ultrasound impacting bring high residual compressive stress on the surface of the 16Mn welded joints, besides, the treatment of ultrasound impacting can improve the fatigue and hardness of the 16Mn welded joints, and when the impacting electric current is 1.5A, and the impacting time is 10 min, the fatigue and hardness of the sample is the best.