查看更多>>摘要：? 2022 Elsevier LtdThis paper presents the delamination effect on the metal sandwich panel of AR500 with magnesium alloy of AZ31B as main core under constant spectrum loading. Recent sandwich panel mostly dealt with static loading, with least research under constant cyclic loading while also having cavity element on its structure, which made them exposed to the catastrophic failure under consistent loading. The metal sandwich panel were simulated using three types of core design for Magnesium alloy; smooth surface, rounded dimple and hemispherical dimple smooth under static and constant cyclic loading. Two types of conditions are applied to the simulation model; with and without pre-stress loads with varying load ratios. Gerber and Goodman stress life fatigue theory was used as a corrective model. Result shows that sandwich panel with dimple core design obtained up to 5% better fatigue life value compared to solid core panel, with and without pre-stress. This study is important as it can improve sandwich panel's bonding strength and reduces the risk of early delamination, especially when it is use for real world application such as protection panel for military purposes.
查看更多>>摘要：? 2022 Elsevier LtdThis work deals with the failure analysis of a super duplex valve operating in technical waters with high chlorides content up to 80 °C. A careful fracture surfaces and microstructural characterization was combined with corrosion studies (SKPFM (Scanning Kelvin Probe Force Measurements) and polarization curves) of different valve regions in order to determine the failure mechanism. It was found that the cast material presents a segregated microstructure containing ferritic phases with different PREN (Pitting Resistance Equivalent Number). This strongly affects the corrosion properties of the material, enhancing the susceptibility to localized corrosion and leading to SCC (Stress Corrosion Cracking) failure.
查看更多>>摘要：? 2022 Elsevier LtdTo understand and analyse fatigue cracking that occurred in heavy truck trailers, a framework based on the damage tolerance concept was proposed to investigate the structural integrity of a high-strength steel trailer structure and to improve its fatigue resistance through local geometric modifications. To illustrate the framework, the fatigue behaviour at a critical region located at a circular cut-out in the trailer was studied. Firstly, a simulated loading spectrum was developed based on the dynamic analysis of a trailer under different driving scenarios together with the FEA analysis of the trailer structure. After that, for the fatigue analysis, crack growth rate at the critical region was computed using the NASGRO equation, and the fatigue life associated with the simulated loading spectrum was predicted. This damage tolerance approach was further applied to explore possible new designs of trailer structures with either improved fatigue performance or reduced tare weight. The results indicate that the proposed framework can be utilised to both monitor the structural integrity of current vehicle structures and design future trailers with longer life and lighter weight.
查看更多>>摘要：? 2022 Elsevier LtdThe purpose of the work is to investigate the causes of vehicle ignition by analyzing the microstructure of copper conductive elements of automotive wiring. This study considers the three most likely vehicle fire scenarios. According to the first scenario, a fire occurs due to overheating of the automotive wiring by short circuit currents. In the second scenario, car fires result from direct exposure to an open flame. In the third scenario, vehicle fires are due to the combined effects of short circuits and open flames. These three scenarios affect the microstructure of copper conductive automotive wiring elements in different ways. Microstructural analysis of copper wires exposed to the temperature conditions of these three fire scenarios was carried out using an optical microscope (OM) and a scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) spectrometer. It has been disclosed that when exposed to an open flame on a copper wire, the fine-grained microstructure of the original copper wire turns into a coarse-grained one. The impact of an electric arc caused by a short circuit can instantly melt copper wires. As a result, local spherical inclusions (beads and pits) appear on the surface of the copper wire, and grains of the dendritic structure are formed in its surface layer. The impact of an open flame on already short-circuited copper wires transforms their fine-grained microstructure containing local spherical inclusions into a kind of coarse-grained microstructure with clear boundaries between grains consisting of copper(II) oxide. The study of the microstructure of copper wires taken from a burned-out car should form the basis for studying the causes of car fires.
查看更多>>摘要：? 2022 Elsevier LtdThis paper investigates the influence of turbine size on the aerodynamics and the force-deflection behavior of the Savonius turbine blades built from aluminum alloy during high winds in static conditions. A one-way fluid-structure interaction (FSI) simulation with the Ansys Workbench environment 2019 R3 is used to predict the flow structures and the force response of various turbine diameters (D) from size 1D until 5D at different wind speeds (8 m/s < v < 18 m/s) and bucket angles (0°–180°). The coefficient of static torque (Cts) from the fluid simulation is validated against experimental work in the literature with average errors of less than 9%. The static torque, blade deformation, stress-induced, and fatigue response are studied extensively herein. This investigation reveals that the induced stress and blade deformations increase proportionally with turbine size and wind speed but even in the worst case scenario the outcome is not even 40% of the failure limit. The existence of endplates reduces the deformation and the alternating stress of the blades (about five times) and also improve the static torque performance by about 30% on average.
查看更多>>摘要：? 2022Failure analysis was carried out on yellow brass tubes that leaked after five years of service in a heat exchanger. The leaked tubes had numerous longitudinal cracks. The service fluid inside the brass tubes was cooling water, used to exchange the temperature with hot steam at the shell side. Microscopic examinations and energy dispersive spectroscopic analyses were carried out on the brass tube inside and outside surfaces to understand the root cause of the failure. A thin layer of deposits was also observed on the internal and external surfaces of the tubes. Microscopic examinations of the tubes at the fracture edges and cracked areas revealed that the cracks initiated and propagated from the regions that suffered dealloying. Both the plug and line types of dezincification were operative on tube surfaces. The failure investigation suggested that the brass tubes suffered severe dezincification, and the failure of the tubes was dezincification assisted corrosion cracking.
查看更多>>摘要：? 2022 Elsevier LtdThe welded hollow spherical joint (WHSJ) is one of the most commonly adopted joint types for spatial grid structures. It belongs to thin-walled structures, which are sensitive to corrosion. Actual projects indicate that aged grid structures are often deteriorated by corrosion. An efficient reinforcing scheme for WHSJs is of shortage for actual engineering application. On the basis of this research background, two reinforcing schemes for randomly corroded WHSJs are proposed in this study. The operational way is also suggested. The reinforcing efficiency is summarized. The presented work is mainly conducted based on a numerical analysis. The reliability of the established FE model is verified through experimental results. The influence of geometrical size on the reinforcement efficiency is then systematically analyzed. The work presented in this study can provide a possible way for the efficient reinforcement of grid structures connected by WHSJs.
查看更多>>摘要：? 2022 Elsevier LtdEngineering components with geometric discontinuous structures generally appear notch effect, which might eventually induce fatigue failure. In this study, a novel multiaxial fatigue prediction model is established for notched components by incorporating the notch effect and non-proportional hardening. Firstly, according to the notch effect, a computational procure of damage parameters is presented by combining the notion of stress intensity with finite element simulations based on the critical plane method. Secondly, considering the non-proportional hardening effect of path modes and material properties, a new modified non-proportional hardening factor is proposed. Particularly, the relationship between the relative stress gradient and the fatigue life is investigated under different stress concentration factors. Finally, with the help of the Manson-Coffin equation, a multiaxial fatigue life prediction model is developed subjected to multiaxial proportional/non-proportional loadings. Experimental data of medium steel En8 and GH4169 alloys are utilized to evaluate and validate the proposed model as well as four other classical models (FS model, MSWT model, Yu model and CXH model). The result indicates that the proposed model yields a higher accuracy on multiaxial fatigue life than other four models, and the majority of prediction results are within the ±2 life factor.
查看更多>>摘要：? 2022 Elsevier LtdCorrosion defects in steel pipes can lead to pipeline failure, and such failures can have severe impacts; thus, developing appropriate corrosion mitigation schemes to prevent them can be beneficial. To this end, the influences of variables such as the depth, length, and group spacing of corrosion defects on the failure of X80 steel pipes containing group corrosion defects were analysed in this study. Abaqus, a simulation software, was used for non-linear finite element analyses, and 52 groups corresponding to corrosions under different geometric factors were prepared. Furthermore, a pipeline failure pressure prediction model was established using 138 sets of simulations to determine the maximum von Mises stresses of pipelines subjected to internal pressures under different working conditions. Actual blast test data and error comparisons with various existing evaluation standards were conducted to verify the accuracy of the proposed model. The results revealed that an increase in the internal pressure and the changes in the depth, length, and group spacing of group corrosion defects impact the maximum von Mises stress in the pipe. Among the group corrosion defects considered, the depth of the deepest defect was found to be the most critical factor in determining the form of damage and the failure pressure of pipes containing corrosion defects. The length of corrosion defects and the axial spacing between groups of defects were found to be the secondary factors that affect the failure pressure. In an actual pipeline, group corrosion defects are expected to cause a reduction in the wall thickness and, thus, pose a threat to safety, an issue that warrants substantial attention. The results of this work can serve as a reference for assessing the failure of X80 steel pipelines containing group corrosion defects.
Muda M.F.Rahman M.A.Mohd Hashim M.H.Kamarudin M.K....
11页
查看更多>>摘要：? 2022 Elsevier LtdTo repair corroded subsea pipelines, composite fiber-reinforced polymer (CFRP) patches are often attached to the defected area. The aim of this paper is to present a method to assure if the strength of repaired subsea pipelines is sufficient enough to sustain burst pressure loads. A computational model for predicting the burst pressure strength of repaired pipelines with CFRP patches is presented. An algorithm of artificial neural networks (ANN) is applied. The geometry of corrosion damage is defined by three physical parameters, namely length, width and depth. The computational model is validated by comparison with refined finite element method solutions. The proposed method will be useful for developing a quick procedure for the CFRP based repair scheme of corroded subsea pipelines.
NSTL
Elsevier