查看更多>>摘要：? 2022 Elsevier LtdThe effects of hydrostatic pressure on the performance of passive film and the pitting growth process of 17-4PH martensitic stainless steel (17-4PH SS) were investigated by electrochemical measurements and stochastic theory. The results revealed that the growth rate and compactness of the passive film were changed by hydrostatic pressure, which inhibited the diffusion of point defects in the passive film and enhanced the protection performance of the passive film. The change of the performance of the passive film affects the pitting nucleation, metastable pitting process and reduces the transition probability from the metastable pitting to the stable pitting, which eventually leads to the decrease of pitting sensitivity of 17-4PH martensitic stainless steel.
查看更多>>摘要：? 2022 Elsevier LtdThe adoption of composite insulators on high voltage power transmission lines remains the state of the art in electricity transmission/distribution, owing to their excellent electrical insulation, mechanical strength-to-weight ratio, anti-pollution flashover properties, ease of installation, and maintenance. However, long-term exposures of the composite insulators to mechanical and environmental stresses have been a major challenge to the power industries. Thus, the various fracture failure form of composite insulator core rods, such as interfacial bonding defects, brittle fractures, and decay-like fractures in association with these stresses was discussed in the review study. Furthermore, as the fracture failure of composite insulator rods affects the stable and safe operation of power lines, the authors, however, concluded the study with recommendations for better practice of power transmission lines using composite insulators. As such, the review will also give a reference for further research in this area.
查看更多>>摘要：? 2022 Elsevier LtdIn this study, concrete slabs subjected to blast loading with 1.5 kg explosive B at different stand-off distances were investigated to study the fragment behavior of concrete slabs. Furthermore, the particle size of the concrete fragments after the explosion was measured. The erosion criterion of coupling tensile damage and the maximum principal strain was introduced to calculate the fragment behavior of a concrete slab subjected to blast loading. The validity of the numerical calculation model was verified by comparison with the experimental data. Moreover, the concrete slab fragment behavior with different charge masses and stand-off distances was analyzed. Finally, a fragment model of the shock wave over-pressure peak, shock wave energy, charge mass, and stand-off distance under blast loading was established. This model can predict the fragment degree of a concrete slab subjected to blast loading by considering the over-pressure peak and energy of the shock wave as criteria.
查看更多>>摘要：? 2022 The Author(s)Fiber-reinforced polymer (FRP) composite materials have gained popularity in civil, mechanical, aircraft, and chemical engineering domains due to their superior mechanical properties and durability. They have been used for strength and durability enhancements of civil structures and a wide range of steel structures subject to static (flexure, compression) and dynamic (fatigue, impact, and seismic) loads have been strengthened and retrofitted. The strength enhancement provided by FRP composites to steel structures depends on several parameters including fiber types, fiber orientations, number of fiber layers, steel section types (geometry and grade), member slenderness etc. Although the superior properties of FRP are sometimes affected by severe environmental conditions that the structures are exposed to, these adverse effects can be minimized. This paper provides a comprehensive review of various techniques to improve the performance and design of steel structures using FRP composites. Strength prediction models under a range of loading and environmental conditions are presented in this single document for the evaluation and safe design of FRP strengthened steel structures and thereby minimise their vulnerability to failure.
查看更多>>摘要：? 2022 Elsevier LtdThe high-precision ball bearing is fundamental to the performance of complex mechanical systems. As the working condition extremely, the micro-pitting become a key problem to influence the rotational accuracy of bearing. This paper developed an experimental method to analyze the relationship between the micro-pitting on the surface of inner groove and the rotational accuracy of bearing, the non-repetitive run-out (NRRO) is applied for rotational accuracy evaluating. In this method, the laser processing method is used to simulate micro-pitting on the surface of inner groove and the laser scanning confocal microscope is used to measure dimension of micro-pitting. Then, the high-precision instrument is applied to measure the values of NRRO with different rotational speeds and loads. Finally, the influence of a micro-pitting for NRRO under different speeds and loads are analyzed for bearing failure predicting. In the future, the NRRO with different micro-pitting size will be measured for failure prediction.
查看更多>>摘要：? 2022Tooth flank fracture (TFF) is a critical fatigue failure mode in case-hardened gears, especially in large-scale and heavy-duty carburized gears. In this study, a TFF failed gear detached from wind turbine gearbox is examined. A contact model incorporating inhomogeneous inclusion and hardness gradient is developed based on semi-analytical method (SAM) and equivalent inclusion method (EIM). The risk of TFF is evaluated by considering a wide depth range of the material gradient properties and the site of inclusion by using material exposure theory. Results indicate that the increase of mean shear stress dominate the stress concentration around the inclusions. The risk of TFF rises dramatically once the inclusions present near the case-core interface. The higher core hardness is more effective to resist the stress concentration caused by inclusions.
查看更多>>摘要：? 2022 Elsevier LtdCorrosion is a naturally occurring process in steel that can degrade the safety and durability of steel structures. Corrosion is inevitable; hence, the assessment of the load carrying capacity of corroded structural members is essential. In this study, compression tests and parametric finite element analysis were conducted on intermediate tubular steel columns to examine the effects of the degree of volume loss (DOV) of corrosion damage, and damage location along the column on the residual compressive strength. The results showed that the corrosion damage affects the compressive strength of the column and the reduction indicates a linear trend. However, the corrosion height does not affect the compressive strength when its value is greater than or equal to the half-wavelength of buckling. A simple approach with the DOV as a reduction factor is proposed to evaluate the compressive strength of locally corroded intermediate columns.
查看更多>>摘要：? 2022 Elsevier LtdWheel flats are a key source of issues in railway systems, as they generate significant wear on both the infrastructure and the train carriages. Flat zones on the wheel tread are created by the wheel sliding unintentionally on the rail. They can cause serious damage to the train and accidents, so identifying worn wheels is critical for human safety and rail transit. The purpose of this study is to present the real-time implementation of fiber Bragg grating sensors on rail tracks and to investigate the train's flat wheel status. By considering passenger train running at speed 70kmph, it has been monitored for 35 sec in the interrogator. Real time analysis of strain induced in the rail was calculated and it has been found from the sensor reading there is peak value of strain of the order of 303.4 μ? which implies that wheel flatness is present whereas for normal wheel strain value is minimal up to 173.23 μ?. By collecting experimental strain data simulation has been done and shift in peak wavelength at 1550.804 nm and reflectivity obtained was 89.3% for flat wheel. Simulation result shows that there is a remarkable wavelength shift for the flat wheel and normal wheel from the Bragg center wavelength.
查看更多>>摘要：? 2022 Elsevier LtdModeling fiber-reinforced concrete at failure by fracture is a challenging task because we need insight into the post-peak behaviour of the model after failure, including crack propagation. In this paper, we present the basic properties of the fiber-reinforced concrete model and its ability to capture the phenomena in three-point bending tests. In this work, we deal with a proof of concept - the verification of the model. The verification of the code includes the selection of the optimal solution algorithm and the selection of the appropriate solution from possible pairs of solutions. Verification of the calculation includes the influence of the number of layers used in the discretisation and, in particular, the influence of the shape of the piecewise defined force–displacement curves of the layers. Only the first stage of verification was performed, i.e. qualitative comparison of the model and experimental results and the influence of the shape of the force–displacement curves. One of the most desirable features of the model is its suitability for subsequent inverse analysis and parameter determination.
查看更多>>摘要：? 2022 Elsevier LtdDeformation and fracture of metal-matrix composites are numerically investigated. Composite microstructures with a single ceramic particle in a homogeneous or polycrystalline matrix are generated by the step-by-step packing method. The thermoelastic-plastic reaction of the matrices is described using isotropic and anisotropic relations, including the associated plastic flow rule and crystal plasticity theory. The thermoelastic response of a ceramic particle is isotropic. In order to describe the crack initiation and propagation in the matrix and particle, two fracture criteria with the limiting values of the equivalent plastic strain and stress are developed. During cooling both pure shear and volumetric tension stress regions are formed in the matrix around the particle. The polycrystalline structure of the matrix prevents through-the-thickness crack formation during subsequent mechanical loading of the composite. Grain boundaries cause multiple stress concentrations and plastic strain localizations all over the matrix material, which delays fracture near the matrix-particle interface.
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