查看更多>>摘要：? 2022In this work was analyzed the fatigue resistance performance of several universal cardan joint for direction column in automotive application. For this purpose, were performed a simulation by finite element (FEA), laboratory fatigue tests and Weibull distribution reliability analyses to evaluate the fatigue life performance of universal joints in according with MAN PV 2892 BR criteria. These analyses were made taking into account a torsional working load in addition to torque applied in the fasten clamp yoke region with the shaft. Additionally, mechanical stakes tests retention was performed in order to attend the requirements of MAN PV 2892 BR. The results indicate that although laboratory fatigue testing exceeds 500,000 cycles, there is an 8% probability that failure will occur at less than the required number of cycles. Thus, the material design and manufacturing process employed, mainly in relation about the amount and mechanical stakes locations and fork roughness, as well as the microstructure inclusions content could bring significant gains in fatigue life in this automotive component.
查看更多>>摘要：? 2022 Elsevier LtdThis work aimed to study the “blushing” phenomenon occurring on epoxy-phenolic coated tinplate after boiling sterilization at 127 ℃ for 1 h. The corrosion resistance of the “blushing” coating and intact coating were measured in NaCl solutions. The possible failure causes were investigated by electrochemical impedance spectroscopy (EIS) combined with surface and cross-section morphology analyses. Electrochemical equivalent circuit (EEC) analyses revealed that, the coating resistance of the “whitening” sample was ～ 6 times lower than the intact sample, while the charge transfer resistance at the tinplate/coating interface of the “whitening” sample was ～ 10 times lower than the intact sample. The capacitance arc at low frequency range showed a constant phase element (CPE) behavior (a time constant dispersion at the tinplate/coating interface), which was due to the material composition inhomogeneity at that interface. Severe underfilm corrosion and coating disbondment were observed on the “whitening” sample after immersing into NaCl solution for 3d, which was due to the poor anticorrosion resistance of the epoxy-phenolic coating and poor coating adhesion. Thin thickness, poor adhesion and disbondment led to a “white” appearance after boiling sterilization.
查看更多>>摘要：? 2022 Elsevier LtdStratum subsidence is one of the important factors threatening the pipe safety. Buckling phenomenon occurs on the pipe crossing subsidence area that may cause leakage accidents. The pipe soil coupling numerical model was established in this paper, buckling behavior of buried pipe crossing stratum area was investigated. The effects of subsidence displacement, radius-thickness ratio, internal pressure, buried depth and stratum on buried pipe's mechanical behavior were discussed. The results show that buckling appears on the pipe when subsidence displacement is large. With the increasing of subsidence displacement, diameter-thickness ratio and buried depth of pipe, the buckling phenomenon becomes more serious. When the internal pressure of pipe increases, the buckling mode changes from concave fold to convex wrinkle gradually, and it is more serious with the increasing of internal pressure. The pipe in rock stratum is more dangerous than that in clay stratum and sand stratum. Those results can be used for the evaluation and maintenance of gas or hydrogen pipes.
查看更多>>摘要：? 2022 Elsevier LtdCorrosive marine environment has negative impact on welded steel structures, so it is necessary to investigate the effect of sea exposure on such materials. This research investigates the change of mechanical properties and surface condition of AH36 shipbuilding steel butt-welded specimens exposed to natural marine environment for prolonged periods (6, 12 and 24 months). Contrary to accelerated tests in simulated laboratory environment, this approach is rarely used. Engineering stress–strain diagrams are obtained using standardized procedures for uniaxial tensile tests, giving insight into the change of material strength due to length of exposure and type of corrosive environment (water, sea water, sea waves). Using impact tests, values of measured Charpy impact energy are given. Additionally, relative mass change over time is given along with calculated corrosion rates. Corroded surface is microscopically inspected and comparison, based on number and dimensions of corrosion pits in the observed area, is given.
查看更多>>摘要：? 2022 Elsevier LtdWater and defects of composite insulator may cause its abnormal temperature rise, which seriously affects the safety of power grid. In this paper, the temperature rise tests of a 110 kV composite insulator before, after water immersion, and after water immersion and drying are firstly carried out. Then a phased array ultrasonic detector is used to detect the internal defects of the insulator. And the phased array ultrasonic recognition model for internal defects is proposed. Finally, the transverse anatomical test is carried out to verify the defects of composite insulator obtained by the temperature rise test and the phased array ultrasonic testing test. The results show that the temperature rise of composite insulator after water immersion is higher than that before water immersion. The maximum temperature rise of the insulator after water immersion is 1.2 ℃. And there is no temperature rise after drying. The defect between the sheath and the core rod at the temperature rise position after immersion is detected by the phased array ultrasonic testing. Cracks and discharge defects are observed anatomically. The accuracy of identification model is proved. And it provides an effective method for nondestructive detection of internal defects of composite insulator in the laboratory. According to the results of temperature rise test, ultrasonic detection and anatomical test, the high water content of the composite insulator sheath is one of the reasons for the slight temperature rise of the insulator. And water and defects are the direct reasons for the obvious temperature rise of composite insulator.
查看更多>>摘要：? 2022 Elsevier LtdThe galvanic corrosion of a tower grounding device consisting of a flexible graphite grounding electrode and Zn-coated steel grounding wire was investigated in a simulated soil environment using corrosion tests and numerical simulation. The significant potential differences between graphite and Zn-coated steel suggest that macro-galvanic corrosion could occur readily in soil, while the dissolution of Zn-coated steel parts was accelerated under the galvanic interaction. The most preferential fracture site resulted from galvanic corrosion of such grounding device was the metallic grounding wire. The conductivity of the soil environment also had a significant influence on the galvanic effect of the couple. The results suggest that the coupling structure of graphite and Zn-coated steel should be avoided in the grounding device design.
查看更多>>摘要：? 2022Solar power installations are increasing every year due to the decarbonization policy established around the world. Photovoltaic (PV) systems and specifically one-axis solar trackers are the most used type of installations in solar power plants. Those solar trackers are slender structures installed in open-air areas sometimes subjected to high speed winds. During the last years, failures in these structures are starting to appear, and most of them are related to a dynamic phenomenon called torsional galloping. The torsional galloping is an aeroelastic instability that presents very high deformation amplitudes and can be triggered at certain wind speeds and tilt angles of the solar tracker. In this paper, a failure investigation of a solar tracker due to torsional galloping is carried out. The broken structure has been analyzed in the field and a numerical model of the structure has been built up. The numerical model is used to identify the natural frequencies of the structure as well as the maximum stresses in the different pieces of the solar tracker. The numerical investigation confirmed that the cause of the failure was torsional galloping occurring for high speed winds and with a tilt angle of the solar tracker of 0 degrees.
查看更多>>摘要：? 2022 The Author(s)In this paper, the bench test spectrum of charge air cooler of Semi-trailer truck, which is the bench test method of Charge Air Cooler reliability durability, and has the correlation with customer, is studied. Affecting CAC B10 life, thermal mechanical fatigue, gas pulse pressure fatigue and vibration fatigue are the main failure modes on the market. According to the principle that the users’ damage is equal to the bench damage in the laboratory, the durability assessment test method of Charge Air Cooler on the bench in the laboratory is established. By collecting the fleet data of the user groups, the target driving path covering 95% of the actual use intensity of vehicle users is determined. The field load spectrum on the target driving path is collected, the fatigue damage is calculated and comparing it with the damage of the test bench in the laboratory, and the relevant bench test spectrum of the Charge Air Cooler of semi-trailer truck with B10 life is formulated. The practical application results show that this method can accurately predict the potential failures of the Charge Air Cooler of semi-trailer truck. And product development cycle is effectively shortened.
查看更多>>摘要：? 2022 Elsevier LtdIn this work, the distortion failure of mechanical components undergoing a heat treatment is dealt with. Samples made of a 9–12% Cr steel with beam-like geometry and different set-ups in the furnace were measured with laser scanner system, before and after a solubilization (air quenching) heat treatment to evaluate its permanent deflection. A numerical model, based on the Finite Element (FE) method, was then developed and a transient thermo-mechanical analysis was performed to simulate the thermal cycle. A simulation approach, which differs from the usual methodology adopted dealing with quenching, is proposed, taking into account phase changes (Sang's semi-empirical method) but also viscoplasticity (Nabarro-Herring creep law combined with bilinear elasto-plastic kinematic model), while the material properties were related to temperature. Comparing numerical results with experiments, it has been observed that, with respect to the case of water quenching, where the distortion is mainly related to phase transformation strains and TRIP (Transformation Induced Plasticity), in the considered case the failure seems to be mainly affected by a low-stress diffusional creep due to the proper weight, when the component is held at high temperature. The influence of different set-up to support the sample in the furnace was also investigated.
查看更多>>摘要：? 2022The manufacturing process of railway axles usually includes axle surface treatment to induce compressive residual stress on the axle surface to increase impact resistance and fatigue lifetime. A proper determination of residual stress enables to obtain correct input data for other procedures, e.g., optimization of specialized treatment or lifetime estimation, which sets safe, but not unnecessary frequent, maintenance intervals of the axles. The most common methods for residual stress determination used by R&D centers of axle manufacturers are the hole drilling method and X-ray diffraction. However, we can use these methods for the determination of surface or close-to-surface residual stress only. In the case of large components like railway axles, it is essential to have information about the residual stress in the whole cross-section, not only from the axle surface, especially if the residual stress is developed by induction hardening, which can influence the residual stress distribution in a considerable depth. The work presented in this paper aims to develop a reliable methodology for determining residual stress in the whole cross-section of a railway axle with reasonable equipment prices or commonly used equipment. Two presented methods follow the defined methodology. They combine well-known destructive methods (layer removal and sectioning methods) with X-ray diffraction and numerical simulations to evaluate correct residual stress distribution. Both ways are applied to the case of an induction-hardened railway axle from the EA4T steel. Results of both methods are then compared to results obtained by neutron diffraction technique and other experimental methods to validate the plausibility of the proposed scenarios.
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