Papers by Keyword: Fatigue Test

Abstract: WJ-8 fasteners are widely used in passenger dedicated line in China. Ballastless track structure is required due to the special line for passenger transport. Fasteners for fixed rail, adjust orbit deformation, etc. Therefore, study the changing rule of the fastener performance especially fastener torque for the design and maintenance of track structure has important theoretical and practical significance. Combined with the force of the track structure, this article through the fatigue test was carried out on the track structure. A simulated train bogie of loading. Research WJ-8 fastener torque as the change of fatigue loading two million times. To provide reference for design and maintenance of Ballastless track.

Abstract: In this paper, by experiments on the low-cycle fatigue life of groups of base metal test specimens under constant total strain control, the number of cycles to fracture failure are obtained. The measured S-N curve of base metal is established and the fitted formulas based on three low cycle fatigue life prediction models are caculated according to the test data. The relationship between the low-cycle fatigue life and strain amplitude are concluded. The results of observation show that the elastic strain effect can be negligible in the range of strain amplitudes used for the study of low-cycle fatigue (0.01-0.08). In addition, the calculation suggests that the three-parameter power function is suitable for the low-cycle fatigue life prediction of the base metal because its prediction accuracy is higher than other methods. The research provides technology supports for life prediction and engineering application of the shock absorber.

Abstract: The aim of this study is to examine the effect of the clearance and interference-fit on the fatigue life of composite lap joints in double shear, 3D finite element simulations have been performed to obtain stress (or strain) distributions around the hole due to interference fit using FEM package, Non-linear contact analyses are performed to examine the effects of the clearance and interference for titanium and composite lap joint. Fatigue tests were conducted for the titanium and composite lap joints with clearance fit and interference fit with 0.5, 1, and 1.5% nominal interference fit levels at different cyclic loads. The results shows that interference fit increases fatigue life compared to clearance fit specimens, the titanium and composite lap joint with 1% interference fit level has the better fatigue life.

Abstract: By means of chemical composition testing, scanning electron microscopy observation, metallographic observation and hardness gradient detection etc, analysis of the typical failure samples from a well-known brand GD8020×1100 ball screw unit in the fatigue test was carried on. Results show that there is no obvious surface wear of the ball screw, showing the normal contact fatigue failure. But severe surface wear happens on the raceway of nut A with obvious flaking and many local cracks; which is the main reason leading to the failure of ball screw unit. So effective measures to avoid earlier failure of the ball screw unit can be put forward by controlling the steel quality strictly and improving the hardness and depth of the hardened layer on the raceway of nut A.

Abstract: According to the requirements of fatigue test of aircraft cabin, large engine and mining machinery for heavy-duty six dimensional generalized force sensors, a new method of using piezoelectric quartz as force-sensitive element on the basis of the theory of heavy force division and equivalent capacity compression is proposed in this study. Furthermore, in order to minimize the force-coupling for the six-dimension force sensor, the optimization objective function is devised and the calculation method for decoupling is also proposed, on the basis of which, the generalized force sensor with high sensitivity, high stiffness, high linearity but light in its weight is designed. At last, the static calibration experiment is carried out the result shows that the sensor has a good ability of heavy force division and capacity for equivalent compression it can be well used in large tonnage six component force loading device and fatigue test system.

Abstract: This article proposes whether fatigue failure is same under laboratory condition and theoretical calculation based on loader fatigue test. Analyzing and calculating the loading cycles, then counting by counting method, then obtain the S-N curve of loader by finite element method. Combines gray correlation theory to analyses the correlation of fatigue failure between laboratory condition and theoretical calculation.

Abstract: Hoisting machinery belongs to special machinery equipment and is gradually developing towards advanced technologies such as lightweight, energy conservation and safety reliability. Therefore objective evaluation for safety circumstances of bridge crane has major engineering significance. The fuzzy-AHP comprehensive evaluation model has been established by fuzzy evaluation method and analytic hierarchy process (AHP) method. In addition, application of the fuzzy-AHP method in bridge crane safety evaluation has been discussed. Firstly, the safety evaluation index system is established according to working environment, manufacturing technology and service condition of bridge crane. Secondly, weight coefficient is determined by AHP method and single stage fuzzy evaluation is processed. Based on this result, multi stage fuzzy comprehensive evaluation is conducted. Finally, the safety grade of bridge crane is obtained. Besides, fatigue test of relevant main girder model is conducted and the accuracy of safety evaluation based on the fuzzy-AHP method is verified through test results.

Abstract: Oil dampers are widely used as a popular countermeasure to mitigate the stay cables vibration. In this study, one actual oil damper designed for some long cable-stayed was experimentally investigated to evaluate the durability. 4 million cycles loading, with frequency of 4 Hz and amplitude of 1 mm, was imposed on the damper. The excitation displacement and damping force were measured and the equivalent damping was calculated from the experimental results. The stiffness effects of dampers behaved during durability tests were also analyzed quantitatively. The test results showed that the dampers were still in good condition after 4 million cycles loading and the dampers temperatures were stable at 50 degree centigrade during the test. According to the durability test results, a model for performance deterioration of damper was proposed to predict the lifetime of oil dampers.

Abstract: Mechanical failure of a structure or a machine during the regular working conditions are often related to the fatigue damage. As a consequence, the structural integrity monitoring of a system has always been a laborious task in the field of engineering. Since the strain measurement is one of the most important predictors of fatigue life, a precise strain measurement method is therefore required. There are many strain measurement methods in fatigue analysis; namely strain gauge, brittle coating method, photoelastic-coating and other optical strain measurement methods. However, various advantages and disadvantages have been found in each of the method mentioned above. Hence, there is always a need to develop a precise and yet informative strain measurement method in mechanical testing. The objective of this study is to develop the first-order shape functions for fatigue test using the Digital Image Correlation technique. In this study, sub-pixel accuracy image correlation algorithm was developed by using MATLAB whereby the positions of the points were precisely selected by using the fine-tuned function. As a result, the first-order shape functions were determined by retrieving the information that is stored in the affine transformation matrix. The works presented in this paper were mainly focused on the development of the algorithms, together with the results and the discussions for the validation exercises. In conclusion, a good agreement was achieved and the newly developed algorithm was proven to be accurate.

Abstract: In order to study anti-cracking performance for geosynthetics, the splitting and fatigue test of bituminous mixtures with geosynthetics and without geosythetics are carried out. The mechanical performance for tensile strength and elastic modulus of asphalt mixture are obtained through two tests. The tensile strength and elastic modulus of bituminous mixture are increased by 14.9% and 54.9% respectively. Through adding the geosynthetics overlay to achieve the purpose of retarding the development of cracks in the pavement.