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Railway transportation system is one of the main needs of the population living in industrialized countries. Many studies have been conducted by engineers due to the importance of railway wheels and railways as a major part of the train. But due to progress in railway technology, in recent years a new type of train wheel known as rim-wheels is presented that their fracture is investigated in this study. The goal of the present study is to calculate stress intensity factors numerically using the boundary element method in railway wheels based on experimental data of material behavior. For this purpose, a series of experiments were performed to determine the behavior of the railway wheel material as well as the data required for numerical analysis. The innovation of this research is that the stress intensity factor is calculated resulting from residual stress of press-fit and heat-treatment processes. Then, the stress intensity factors resulting from the two processes are superimposed in pure mode I, mode II, and mode III loading due to the same crack geometries. Also, the study includes a survey on the effect of crack length on crack propagation as one of its main effective factors. Besides, fatigue crack growth path is calculated and its propagation is also estimated and the effect of different parameters is studied on fatigue crack growth and path.

In this paper, the fracture behavior of 2024-T351 aluminum alloy as a key engineering material in the aeronautical industry is investigated under various planar and nonplanar mixed-mode loading conditions involving pure mode-I and pure mode-III loadings. A newly suggested loading setup accompanied by compact tension shearing and tearing (CTST) specimens is utilized to perform fracture tests. Three-dimensional finite element modeling using the interaction integral method is carried out to derive the stress intensity factors (SIFs) and their ratios through the crack front for several mixed-mode configurations. The numerical results reveal that the coupled effect of modes II and III under mixed-mode I/II, I/III and I/II/III loading conditions is remarkable. Moreover, the amounts of SIFs at the center of the specimens are employed to predict the critical fracture loads according to different mixed-mode criteria. Also, scanning electron microscope (SEM) images of the fracture surfaces of CTST specimens are examined to evaluate the effect of different loading angles from a morphological viewpoint. A good consistency can be found among the results of the theoretical solutions of the criteria and the experimental observations for different loading conditions.

The purpose of this study is to investigate dental strength and mechanical behavior of Premolar teeth with fissure sealants. Due to the large number of studied parameters, Taguchi algorithm was used to design the experiments and reduce the number of tests. 36 Premolar teeth were selected from three different age groups (child/young/Adult), gender (Male/Female), indenter (Flat/Wedge/Sphere) two types of quality (Intact/Restored) and jaw (Maxilla/Mandible). In this study, two kinds of adhesive (Margin/Single Bond) and fissure sealant material (Seal.it/Wetbond) with various strength and modulus of elasticity were chosen. Also, tooth was stored under different relative humidity amounts (52% and 95%), and was curried by light cure device with intensities of 1000 and 1200 W/cm2. The etching process was performed in acid concentrations of 32% and 37%. The compressive loading was carried out using a universal test machine under displacement-control. The results of interaction effects of gender on age demonstrated that in young age group, male teeth are stronger than female teeth while in child and adult age groups, male and female teeth show relatively same values. The interaction effect results of Taguchi analysis between different indenter surfaces and age groups recommended the spherical indenter, due to the distinction of strength results among different age groups and consequently, ability to investigate the interaction effects between indenter and other parameters. As expected, the results show that the quality factor is the most effective factor. In terms of dental materials and jaw type, the amount of changes is also quite noticeable. Also, the effect of other parameters (humidity, etching, light cure intensity, and adhesive) is negligible in comparison with others.

The purpose of this paper is to estimate the fatigue life of AA2024 aluminum alloy sheets in riveted joints under the influence of cyclic loading. First, the factors affecting the plastic equivalent strain resulting from the riveting process have been identified using the finite element method. For this purpose, a three-dimensional elastoplastic model is used for simulation. The relevant geometrical parameters such as the rivets shank length, the rivets shank diameter, and dimensional tolerances as well as pattern of where the rivets are and the material of the riveted joints are determined and subsequently the fatigue life of the aluminum joint is obtained by experimental tests. Then the fatigue life of the riveted joints is calculated using the Paris equation. To prove the validity of the analytical results, numerical modeling and experimental tests are performed on AA2024 aluminum alloy sheets in riveted joints. Numerical analysis has been performed using linear fracture mechanics and boundary element method (BEM) for the fatigue crack growth of AA2024 aluminum alloy sheets in riveted joints. Finally, the results of the analytical method for fatigue life are compared with experimental tests and numerical method that results in acceptable achievements.

The purpose of this paper is to estimate the fatigue life of 2024 aluminum plates in riveted joints under the influence of cyclic loading. First, the factors affecting the plastic equivalent strain resulting from the riveting process have been identified using the finite element method. For this purpose, a three-dimensional elastoplastic model is used for simulation. The relevant geometrical parameters such as the rivets shank length, the rivets shank diameter, and dimensional tolerances as well as pattern of where the rivets are and the material of the rivet joints are determined and subsequently the fatigue life of the aluminum joint is obtained by experimental tests. Then the fatigue life of the riveted joints is calculated using multiple site damage (MSD). To prove the validity of the analytical results, numerical modeling and experimental tests are performed on 2024 aluminum plates in riveted joints. Numerical analysis has been performed using linear fracture mechanics and boundary element method (BEM) for the fatigue crack growth of 2024 aluminum plates in riveted joints. Finally, the results of the analytical method for fatigue life are compared with experimental tests and numerical method that results in acceptable achievements.

Fatigue crack is one of the most common defects in railway system. Fatigue crack growth may lead to wheel and rail failure and damage to other components. In this paper, by applying the including service conditions of the railway system, first, a 3D nonlinear stress analysis model has been applied to estimate stress fields of the rail under the influence of periodic overloads. For this purpose, an UIC60 rail with accurate geometry using finite element method (FEM) is studied. Next, the results of this model are used for fatigue crack growth and also to estimate the fatigue life in rails using boundary element method (BEM). In this regard, first, the types of cracks and the corresponding factors which cause them were analyzed. In addition to performing stress analysis for different positions of the wheel, different values of the stress intensity factors (SIFs) were also obtained. Using these stress intensity factors, two characteristics of fatigue crack propagation namely, crack growth and direction of its development, were obtained. In this study, Paris Equation is used as a criterion of fatigue crack growth rate and the maximum tangential stress was considered as the crack growth direction. The numerical analysis results showed that the effect of periodic overloads on the fatigue life in rails was significant and could not be ignored.

Accurate prediction of fatigue crack growth on railway wheels and the influence of residual stresses by finite element method (FEM) modeling can affect the maintenance planning. Therefore, investigation of rolling contact fatigue and its effect on rolling members life seem necessary. The objective of this paper is to provide a prediction of rolling contact fatigue crack growth in the rail wheel under the influence of stress field from mechanical loads and heat treatment process of a railway wheel. A 3D nonlinear stress analysis model has been applied to estimate stress fields of the railway mono-block wheel in heat treatment process. Finite element analysis model is presented applying the elastic–plastic finite element analysis for the rail wheel under variable thermal loads. The stress history is then used to calculate stress intensity factors (SIFs) and fatigue life of railway wheel. The effect of several parameters, vertical loads, initial crack length and friction coefficient between the wheel and rail, on the fatigue life in railway wheels is investigated using the suggested 3-D finite element model. Three-dimensional finite element analysis results obtained show good agreement with those achieved in field measurements.

One of the most important issues in railway wheels is residual stresses. It is desirable to produce less residual stresses when possible and to decrease the remaining residual stresses in the wheels. The objective of this paper is to provide an estimation of the residual stresses in the rail wheel caused by the stress field from heat treatment process of a railway wheel. A three-dimensional nonlinear stress analysis model has been applied to estimate stress fields of the railway mono-block wheel in heat treatment process. After forging or casting, railway wheels are heat-treated to induce the desirable circumferential compressive residual stress in the upper rim. Finite element analysis model is presented applying the elastic–plastic finite element analysis for the rail wheel under variable thermal loads. Calculative analysis applying a finite element method (FEM) has been used to predict residual stresses. The quenching and annealing segments of the wheel manufacturing process are simulated using a decoupled heat transfer and stress analysis. Three-dimensional finite element analysis results obtained show good agreement with those achieved in field measurements.