查看更多>>摘要：? 2022 Elsevier LtdCeramics rolls/rollers recently developed can be used efficiently in steel manufacturing industries to produce high-quality steel plates under high temperature. However, sometimes the shrink-fitted shaft is coming out from the ceramic sleeve during the use even though no external force is applied in the coming out direction. In the previous studies, to realize the phenomena under a large number of roll rotations, numerical simulations were performed by using two-dimensional modelling. Towards preventing the failure, this paper focuses on identifying the driving out force by applying 3D numerical simulation. Here, the driving out force can be defined as the contact force appearing at a ball-stopper designed to prevent the coming out. The results show that the summation of frictional shear stress along the shrink-fitted surface is in good agreement with the driving out force. As the most fundamental design factors, the friction coefficients, the shrink fitting ratios, the shrink fitting length, and the Young's modulus of the shaft are focused. Then, those effects on the driving out force are discussed towards preventing the coming out failure.
查看更多>>摘要：? 2022 Elsevier LtdThe fracture of coil springs occasionally appears in rail vehicles, which may severely jeopardise the train running safety. In this study, the fracture phenomenon of the locomotive coil spring is investigated mainly using the experimental methods. Field surveys are preliminarily carried out, including statistical analysis, visual observations, material properties tests, and measurement of the wheel out-of-roundness (OOR), all of which can help to discover the potential contributing factors to the coil spring fracture. To ascertain the root cause of the coil spring fracture, a well-designed modal test is carried out to determine the natural frequency of the coil spring. The dynamic stress of the coil spring is also measured to verify whether the structural resonance existed. Moreover, dynamic simulation is performed to reproduce the resonance phenomenon. The experimental results show that the 1st expansion modal of the coil spring will be motivated by the excitation frequency of the 17th order wheel OOR if the locomotive runs frequently in the speed of 75–80 km/h. Two mitigation measures are presented, including the wheel re-profiling and structure optimization for the coil spring. Furthermore, the proposed countermeasures are proved to be effective for reducing the risk of coil spring fracture according to the filed tracking tests.
查看更多>>摘要：? 2022 Elsevier LtdThis paper presents the failure analysis of the pivot of a metro train. For this purpose, two pivots that contained cracks were analyzed. The cracks were detected during rutinary non-destructive liquid penetrant testing, which is schedule within the maintenance routine. For the failure analysis the material of the pivots was characterized to determine its chemical composition, microstructure and hardness. Additionally, fractographic analysis was accomplished by visual observation and scanning electron microscopy. Finally, a model of the stress state of the pivot was developed, which allowed determining the areas of highest stress and computing the fatigue life. The failure analysis showed that cracking was due to a fatigue phenomenon that exhausted the life of the component. Also, catastrophic failure was prevented by the non-destructive rutinary inspection.
查看更多>>摘要：? 2022 The AuthorsProduction of high-quality and high-grade casts at the lowest possible cost is a priority of every foundry. Innovation and optimization of the currently applied production processes is a necessary step to achieving such a goal. Costly and long experiments performed in real foundries may be replaced with numerical simulations, as they provide reliable representation of the casting process using the computer technology. A detailed analysis of simulation results facilitates forecasting various risks that might negatively affect the quality of produced casts, and hence the quality of the entire production process. The present article discusses the effects of adjustments to the design of a gating system on the quality of a cast made of EN-GJS-500-7 ductile cast iron, which is used as a clutch wheel in turbines in wind power plants. During the production of the cast, two models of the gating system were created in Solid Works CAD software. The gating systems were validated using NovaFlow&Solid casting simulation software. The modification of the gating system design resulted in a reduced amount of liquid metal used for casting, which has significant economic effects in the mass production. Eight simulations of the designed gating systems were carried out. The main purpose of the simulations was to determine the mesh density as well as the casting and solidification conditions so that they are as close as possible to the real conditions in a foundry. Subsequently, the gating system was modified with the result of eliminating defects in the cast that occur during the solidification process as well as increasing the utilization of liquid metal.
查看更多>>摘要：? 2022 Elsevier LtdIn order to solve the problem of tunnel diseases caused by lining cracking in mountain tunnels, this paper studies the crack repair technology of mountain tunnels. Based on this, this paper innovatively puts forward a new repair method of tunnel cracks—plate-short anchor assembly structure. Through literature investigation and theoretical derivation, the mechanical mechanism of the plate-short anchor assembly structure is analyzed, and the calculation formula of bearing capacity is proposed. The loading device for the bias pressure test of prototype components of tunnel lining is independently designed, and the destruction test is successfully carried out by simulating the stress mode of tunnel lining. By simulating the state changes of the plate-short anchor assembly structure under different cracking states, the ultimate bearing capacity under different working conditions is obtained, and the evolution process of the failure mode of the new structure is revealed.
查看更多>>摘要：? 2022 Elsevier LtdIn view of the problem that the broken stope roof under repeated mining is prone to end face roof leaks, this paper's research background is the close distance coal seams mining of a mine in Guizhou province, China. The impact of stope roof structure movement on the immediate roof was elucidated from the analysis of stope roof structure movement under repeated mining employing a combination method of field measurement, physical simulation, theoretical analysis, and numerical simulation. As a result, the mechanism of end face roof leaks under repeated mining is investigated, and the corresponding control measures are proposed. The results show that the cantilever beam structure instability of the stope roof under repeated mining is an important reason for the end face roof leaks and support crushing accident. The fracture forms of cantilever beam structure are divided into direct fracture and hinged structure fracture. The direct fracture is affected by the support working resistance. The cantilever beam hinged structure is divided into sliding and rotational instability. The periodic weighting interval is small and the fracture degree is large under repeated mining, which leads to the sliding instability. It is concluded that reasonable support working resistance is the important reason to keep the cantilever beam structure stability. Therefore, the stope roof leakage control countermeasures under repeated mining are proposed. The UDEC numerical simulation is used to verify the above analysis again, so as to provide the basis for the end face roof leaks prevention and control under repeated mining.
查看更多>>摘要：? 2022 Elsevier LtdFailure Mode, Effects, and Criticality Analysis (FMECA) is a proactive reliability and risk management technique extensively used in practice to ensure high system performance by prioritising failure modes. Owing to the limitations of traditional FMECA, multi-criteria decision-making methods have been employed over the past two decades to enhance its effectiveness. To consider the vagueness and uncertainty of the FMECA evaluation process, an interval-based extension of the Elimination et Choice Translating Reality (ELECTRE) TRI method is proposed in the present paper for the classification of failure modes into risk categories. Therefore, ratings of failure modes against risk parameters are provided in an interval form by a panel of FMECA experts and then properly synthesised to provide a group consensus and improve the accuracy of the results. The relative importance of the risk parameters is also considered. The method is validated using a numerical example relating to the propulsion system of a fishing vessel.
查看更多>>摘要：? 2022 Elsevier LtdRail damage prediction is a complex task because it depends on numerous tribological parameters and the dynamic conditions produced by the vehicles operating at different speeds and configurations. Shakedown maps and Whole-Life-Rail-Model/T-Gamma have been used to predict rail damage, but they involve assumptions that may reduce their accuracy. This paper proposes a simulation modelling method to predict rail surface damage based on a locomotive digital twin, calibrated shakedown maps and friction measurements. The method improves the accuracy of rail damage predictions by including slip-dependent friction characteristics, co-simulation of locomotive traction mechatronic system and the mechanical properties of the wheel and rail materials measured through tensile tests. A set of operating conditions are simulated on a high-performance computing cluster, with stress results being post processed into calibrated shakedown heatmaps. The method clearly indicated the influences of the different operating conditions on rail damage for specific combinations of wheel-rail materials and vehicle-track configurations.
查看更多>>摘要：? 2021 Elsevier LtdThe author regret, Ref. [16] should be read as [16] 1. HBFM. 1st Air Maintenance Factory Directorate, Eskisehir, Turkey. The author regret, Ref. [16] is inadvertently omitted for Figs. 4–10. The figures should be read as: Fig. 4. The damaged turbine wheel [16]. Fig. 5. The material loss and part breaking from turbine wheel [16]. Fig. 6. Cracks on blade surface of turbine wheel [16]. Fig. 7. The detected cracks via BSM method [16]. Fig. 8. Asymmetrical circumferential wearing, crushing and starching on turbine wheel aft surface [16]. Fig. 9. Heat affected zones and discoloration on blade surfaces of turbine blade [16]. Fig. 10. Multiple cracks and pitting surfaces on turbine wheel blade [16]. The authors would like to apologise for any inconvenience caused.
查看更多>>摘要：? 2022 Elsevier LtdTorsional fatigue always exists after a wire rope is put into use, which results in damage aggravation and lifespan reduction. This study is aimed at exploring the comprehensive tribo-fatigue behaviors of wire rope considering torsional fatigue. To achieve this aim, a new type of self-made fatigue testing machine was introduced, and the bending fatigue tests were carried out. Furthermore, the diameter shrinkage ratio, the number and distribution of broken wires under different fatigue times were studied by means of manual detection and non-destructive testing. Moreover, the fractures and wear scars were investigated with the aid of the LW200-4JT optical microscope system. For the thicker outer wire of spiral strand (SS), the influences of bending fatigue times on the evolution of wear parameters were comparatively analyzed. The research results are as follows. With the increase of bending fatigue times, the diameter shrinkage ratio increases, and the increase decelerates gradually. The artificial statistical results agree well with the non-destructive testing results. To be specific, the broken wire develops slowly in the early stage of fatigue, whereas it develops rapidly when the fatigue times exceed 60,000. The broken wire is highly concentrated in the thicker outer wire of SS 1. The maximum width and depth of wear scars of the thicker outer wire of SS 1 increase with the increase of cycles. The values of the two parameters at different contact positions follow the order: contact with the pulley > contact with the adjacent SS 1 > contact with the SS 2 > contact with the wire in the adjacent layer in the same strand. This study is expected to find the fatigue failure rules of end-fixed hoisting wire rope, thus providing a basis for improving the safety of mine hoisting.
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