Papers by Keyword: Fatigue Life

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Authors: Xiao Hua Yang, Ding Zhang, Yong Zhang
Abstract: A 2D FE model of cracked aluminum plates repaired with adhesively bonded composite patches was established in this paper, and then the model was validated by comparing the calculated SIF and fatigue life of repaired structure with existing results. The result shows that the model is accurate enough to be used to analyze the mechanical property of cracked aluminum plates repaired with adhesively bonded composite patches.
Authors: Li Bin Zhao, Feng Rui Liu, Jian Yu Zhang
Abstract: An three-dimensional FE model of threaded connection is proposed by means of the general purpose program ANSYS. The model is accurately constructed according to the helical thread profiles. The mechanical behavior of each bolt subjected to eccentrically loading is investigated and the stress distribution is discussed detailedly. Based on the stress level, the fatigue life of threaded connection is predicted by the cumulative damage method. This work can provide a deeply understanding on the mechanics behavior of bolt connection in engineering, especially for its application on the appending equipments of airplane.
Authors: Wen Guang Liu, Hong Lin He
Abstract: There are different modes of damage in any engineering structures, and most of them are cracks. In order to study the influence of coupling effect on the fatigue life, a calculation method of structure vibration fatigue life with crack propagation is proposed. In analysis, a series of finite element model with crack of different length is built to simulate the crack propagation, and Paris equation is employed to calculate the vibration fatigue life by stepwise method. The crack initiation life is got based on the change law of natural frequency from test results, and the total life is calculated in the end. Results indicate that the simulation results identical with the experimental results well.
Authors: Yue Ting Niu, Xi Hui Mu, Xin Yong Qiao
Abstract: Transmission casing fatigue fracture is one of the most serious failure of the transmission system in the form of tracked vehicles. This article through the analysis of materials and structural stress analysis of a typical fracture failure mechanism of the tracked vehicle transmission cabinet. And in obtaining the stress on the basis of load spectrum its fatigue life was calculated. The results show that in the structure of the stress concentration and cabinet material number ZL101 cast aluminum defects such as inclusions, porosity are the main cause of fatigue crack initiation and propagation.
Authors: Pablo Lopez-Crespo, Belen Moreno, Jose Zapatero
Abstract: There are a number of theories available to model biaxial fatigue problems. Among these, the critical plane models try to predict not only the fatigue life but also the orientation of the crack or failure plane. This work attempt to analyse the biaxial tension-torsion problem from a strain-based analysis focused on plane failures predictions. Fatigue life and critical plane predictions are carried out applying multiaxial models proposed by Brown-Miller, Fatemi-Socie and Smith-Watson-Topper. The theoretical results are compared with constant amplitude test data, in-phase and out-of-phase (90˚) in a structural steel. The results suggest that Smith-Watson-Topper model predictions of fracture plane do not match the real fracture plane. The critical fracture plane predictions of the Brown-Miller and Fatemi-Socie models do not match in most cases with experimental observations either, but considering the second plane of the maximum shear strain amplitude, the predictions of the fracture plane and fatigue life improve substantially.
Authors: Xian Min Chen, Qin Sun, Di Guan, Feng Ping Yang
Abstract: A damage evolution model is presented for fatigue life prediction of metallic structures. This model is formulated based on damage mechanics and the irreversible thermodynamics framework developed by LEMAITRE and CHABOCHE. Using this model, the fatigue lifetime can be predicted both in the high cycle fatigue (HCF) regime and the low cycle fatigue (LCF) regime. Based on the energy theory and material fatigue test data, the plastic strain threshold for damage initiation was modified for HCF and LCF respectively. The damage evolution parameters were determined according to the fatigue test results of standard specimens. A damage mechanics-finite element full-couple method was adopted to simulate the process of fatigue damage evolution. The numerical simulation of fatigue lives were compared with the fatigue tests of 2A12-T4 open-hole plates and good agreement was obtained.
Authors: Jun Cheng Lv, Tao Qian, Kai Song, Bing Heng Qin, Xiao Ming Ding
Abstract: A new fatigue life simulation analysis method for spot weld joints is proposed which considers the fatigue crack propagation from the point of fracture mechanics. The traditional fatigue simulation analysis methods for spot weld joints are mainly LBF method based on force and LMS method based on stress, while there exist some issues such as the prediction accuracy is not high, modeling and computational efficiency is low. A modular spot weld model is adopted in this paper, the node forces and moments around the spot weld are extracted through the finite element analysis, then a average stress intensity factor through the crack propagation path is calculated as the evaluation parameter of fatigue life. Shear fatigue test is designed for spot weld joints with two high strength steel materials (HSLA340GI and DP600GI) and four different thicknesses, then double logarithmic regression analysis is implemented between the average stress intensity factor and the fatigue life data of spot weld joints, then a matching curve is obtained as the fatigue life prediction curve for spot welds. Comparative analysis of prediction accuracy is implemented for these three methods, the results show that the prediction accuracy of fatigue simulation method for spot weld joints in this paper is higher than traditional LBF and LMS methods.
Authors: Kai Qi, Wei Xiong Wang, Xin Hua Wang, Ai Hua Jiang, Bai Qing Liu
Abstract: The fatigue life of crane steel structure will inevitably decrease in the course of work, which directly affects the work of crane. So the correct fatigue life evaluation is necessary. Based on crack propagation theory, a framework of assessing remaining fatigue life of crane metal structures is built in this paper. Moreover, in order to descript the analysis process, an example about fatigue life estimation of a shipbuilding gantry crane whose maximum hoist 100 ton was shown. During assessment of remaining fatigue life of aged crane structure, some important indexes were inspected such as corrosion,strength and defection in focused weld joints, besides of finite element simulation of structure. The results can also be used to evaluate the whole metal structure of this crane.
Authors: Hong Seok Kim, Yong Sung Lee, Ki Hoon Shin
Abstract: Shot-peening is the process of repeatedly hitting the work piece surface with small balls, making overlapping indentations on the surface. This process is extensively used on shafts, gears, springs, and jet engine parts because it imparts compressive residual stresses on the surface, thus improving the fatigue life of components. Under-peening does not give a sufficient fatigue life while over-peening induces cracking and reduces fatigue performance. Hence, determining optimal peening conditions such as peening time is very important. In general, optimal peening conditions are experimentally determined by measuring arc-height using Almen-strip or calculating coverage using microscope images. Shot-peening coverage is defined as the proportion of the exposed surface that has been impacted in a given time of shot-peening. To save the time and effort spent in repeating experimental measurement needed whenever the geometry of a work piece and peening conditions change, this paper presents a computer simulation algorithm for the prediction of shot-peening coverage, which is based on the geometry of a work piece. An example is presented to validate the proposed method.
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