Papers by Keyword: Fatigue

Abstract: According to the BS7448 fracture toughness test standard, this paper conducted a CTOD(crack tip open displacement) fatigue crack precast test with the bridge steel and analysis the tests results, thus obtained the related conclusions. With the increase of thickness and strength of the steel plate, the security of fatigue performance and toughness of the plate is becoming more important for the structure. So the evaluation of fatigue performance is a very significant work for engineer. This dissertation through the text study the CTOD Specimens Fatigue Crack Prefabricated process of bridge steel and its characteristics, and its results will provide the important experimental basis and computation basis.

Abstract: Study on Strength design of steel components including residual stress. First, sample with residual stress of shot peening were detected, material properties change with residual stress was analyzed. And problems in the strength design were discussed. On this basis, design criteria for design of static strength and fatigue strength under plane stress state were derivated, the design criteria formula of the unification form is obtained. Finally, examples illustrate the reasonableness of the conclusions and deriving formulas.

Abstract: Shiftwork disrupts the sleep-wake cycle, leading to sleepiness, fatigue, and performance impairment, with implications for occupational health and safety. Aircraft maintenance crews work a 24-hour shift rotation and sustain flight punctuality rate of job stress.If an error occurs during the aircraft maintenance process, this error may become a potential risk factor for flight safety.This paper focuses on optimal work shift scheduling to reduce the fatigue of aircraft maintenance crews. We model fatigue as a dynamic system, and the objective is to find the optimal shift schedules that minimize the maximum fatigue values. Various constraints such as holidays, company and government regulations are included in our model. This optimization problem is formulated as a mixed-integer program, in which the shift assignments are described by 0-1 variables. We take a sample aircraft maintenance crews schedule to demonstrate the proposed methods.

Abstract: G70 Tank car uesd for transportation on liquidsliquids of gas and bulck goods in form of powder,is one of the major class of Chinese railroad freight cars.And the tank car makes about 18% of the toatal amount of freight cars. In this stduy, the carbdoy finite element model of tank car was constructed,and calculated stress of carbody both empty car and fully loaded car,then get the results of key postsitions. According to the AAR load spectrums on the part of the tank car,translated the results into dynamic stress through the quasi-static method. Calculated the damage of carbody with the fatigue analysis method provied in AAR, compared the fatigue life under various comonent.

Abstract: Herein, two models of long-span bridges, namely a suspension and a cable-stayed one, are developed at the numerical level in a commercial finite elements code, starting from original data, and they are used to simulate the structural response under wind excitation and seismic excitation. The main goal of this study consists in the evaluation of a control strategy, designed and proven effective for the wind action, considering the suspension bridge, or for the seismic action, for the cable-stayed one, when the bridge structure is subjected to the seismic and the wind action respectively.

Abstract: In order to improve fatigue life of wheel steel, secondary-refining process is done with Al-deoxidation and slag of high basicity, high Al2O3 content and low oxidizing property. By slag-steel-inclusion interaction, harmful inclusions could be controlled well to be eliminated by floation, lowering T[O] content to 0.0007% in round billets, enhancing fatigue life of wheel steel. It is found that (Al2O3) in slag is positive factor for decrease of T[O], while (CaO)/(Al2O3), (SiO2) in slag and [Al]s in molten steel is negative factor for it. As a result, by INSTRON fatigue testing machine, tested steel samples achieve ultra-high cycle of 108 above, realizing experimental purpose of improving fatigue life of wheel steel.

Abstract: Glass fiber reinforced polymeric (GFRP) composite laminates have been prepared by hand layup method. According to ASTM standard, the test specimens have been prepared to carry out the flexural bending tests. The specimens have been subjected to both cyclic impact load and cyclic gradual load with various frequencies prior to the flexural bending analysis. Three point bend method has been adopted to find out the flexural strength and flexural modulus. Flexural strength and modulus have been calculated from the load deflection curve obtained from the tensometer for respective specimens. The flexural bending properties of GFRP composites subjected to cyclic gradual load and cyclic impact have been compared and found that the GFRP composite materials are effective for gradual cyclic load than the cyclic impact load.

Abstract: The paper presents the researches to determine the best technologies to improve the lifetime of the corner welding. Generally it is says that the convex corner welding presents high mechanical properties because of the greater area section. The practice activity shows that in fact, because of the stress concentrators, these shapes of the welding are not the best solution. A better shape of the corner welding is the concave one that provides better results in the working conditions. To provide better results of the convex shape corner welding different recondition techniques are known. The paper is focused on fatigue testing performed on different samples realized with different beads on different working parameters. There are studied different reconditioned probes and the results are reported in fatigue curves.

Abstract: When coupling with temperature is incorporated, the problem of fatigue is formulated within the general framework of thermomechanical fatigue. Considering the special case of steel structures, in addition to variations of material and fatigue parameters with temperature, fatigue damage depends on the phasing existing between the concomitant strain and temperature cycles. In this work, the extended finite element method is used to simulate crack growth under thermomechanical fatigue coupling. Assuming large cycle duration for which temperature variations can be considered to be uniform, this approach is applied in the context of linear elastic fracture mechanics for the particular case of the three dimensional Compact-Tension specimen. The objective is to attempt understanding more closely crack growth mechanism under thermomechanical loading. Characterization of fatigue was assessed as function of phasing and strain restraint.