Key Engineering Materials Vols. 452-453

Abstract: In the public transport vehicle, vertical and lateral behaviors have a significant effect on ride comfort and safety of passengers on curved track. Based on vertical and lateral vibration accelerations measured on floor level in passenger compartment when the K-AGT ran on the minimum curvature of the 2.4km-test track in driverless mode, expanded uncertainties in measurement were estimated statistically. In addition, vertical and lateral dynamic behaviors of the K-AGT were discussed in this paper.

Abstract: Many mechanical components are subjected to multiaxial fatigue. These conditions are typically coming from external loads, the geometry of the component and/or residual stresses. However the majority of experimental data available in the literature are focused on the simpler uni-axial fatigue problem. The present work describes a series of experimental tests conducted to characterise in a comprehensive way the multiaxial behaviour of a ST52-3N structural steel. First, the monotonic properties of the steel were obtained experimentally. Then cyclic properties were also measured both in the longitudinal and torsional axes. Finally another series of tests were carried out to study the multiaxial response of the material. Both in-phase (proportional) and out-of-phase (non proportional) loadings were employed, thus providing a complete database for improving current models which describe the multiaxial behaviour of materials.

Abstract: Waves generated by a moving source are discussed. Introducing a simple model for the stick-slip motion of the source, an exact response of SH-wave in an infinite elastic solid is derived. The response is composed of an infinite sum of time-harmonic wave with multiple frequency of the stick-slip motion and Doppler effects are derived from the far-field approximation. This shows that Doppler effects take place even if the source magnitude is uniform, not time-harmonic.

Abstract: This paper describes the results of structural analysis and loading test of a bogie frame. The purpose of the analysis and test is to evaluate the safety and functionality of the bogie frame under maximum load. The bogie system consist of the bogie frame, suspensions, wheel-sets, a brake system and a transmission system. Of these components, the bogie frame is the major component subjected to the vehicle and passenger loads. The evaluation method used the JIS E 4207 specifications throughout the FEM analysis and static load test. The test results have shown the bogie frame to be safe and stable under design load conditions.

Abstract: There are a number of theories available to model biaxial fatigue problems. Among these, the critical plane models try to predict not only the fatigue life but also the orientation of the crack or failure plane. This work attempt to analyse the biaxial tension-torsion problem from a strain-based analysis focused on plane failures predictions. Fatigue life and critical plane predictions are carried out applying multiaxial models proposed by Brown-Miller, Fatemi-Socie and Smith-Watson-Topper. The theoretical results are compared with constant amplitude test data, in-phase and out-of-phase (90˚) in a structural steel. The results suggest that Smith-Watson-Topper model predictions of fracture plane do not match the real fracture plane. The critical fracture plane predictions of the Brown-Miller and Fatemi-Socie models do not match in most cases with experimental observations either, but considering the second plane of the maximum shear strain amplitude, the predictions of the fracture plane and fatigue life improve substantially.

Abstract: A variational technique has been developed to evaluate the static stress intensity factors of mixed mode problems with mesh free method in this paper. The stiffness is evaluated by regular domain integrals and shape functions are determined by both radial basis function (RBF) interpolation and moving least-square (MLS) method. The stress intensity factors are obtained by two boundary integrals with variation of crack length. The applications of proposed technique to two-dimensional fracture mechanics have been presented with several examples. Comparisons are made with benchmark solutions.

Abstract: Where the self weight of the overall RC(Reinforced Concrete) or PC(Precast Concrete) floor system needs to be considered, the quantity of in-situ concrete required can be reduced by the application of polystyrene void forms to slab. In this study, flexural behaviors of void RC and PC slab with polystyrene form were evaluated to understand the effect on the self weight reduction of the slab. This paper presents experimental works and finite element analysis on the bending of the void slabs. Six specimens were tested. The main parameters of experiments were the slab types (RC and PC), the types and arrangement details of polystyrene form, and the thickness of slab. Structural behaviors of void slabs were evaluated on the basis of failure mode, load-displacement curve, and ultimate strengths. Test results indicated that nominal strengths by ACI code agreed well with experimental results. The results of analysis were compared with the results of test for estimating the validity of analysis model.

Abstract: The fracture processes in cement paste at microscale are simulated by the 3D lattice fracture model based on the microstructure of hydrating cement paste. The uniaxial tensile test simulation is carried out to obtain the load-displacement diagram and microcracks propagation for a Portland cement paste specimen in the size of 100×100×100 µm3 at the degree of hydration 69%. The Young's modulus, tensile strength, strain at peak load and fracture energy are computed on the basis of the load-displacement diagram.

Abstract: The lattice fracture model is presented in this paper, which is intended to simulate the fracture processes in multiphase materials to obtain the mechanical behavior in terms of load-displacement diagram and the cracks propagation. The basic procedures of lattice fracture analysis is that imposing a prescribed displacement on a lattice structure, finding the critical lattice element with the highest stress/strength ratio, removing it from the system and repeating until the system fails globally. One of the challenges in computer implementation of 3D lattice fracture model is the huge demand for computer memory. Matrix free technique is adopted to solve this problem.

Abstract: Torsion experiments should be adopted to characterize large strain elasto-plastic behavior of material instead of traditional uni-axial tension experiments due to the plastic stability of specimen in torsion deformation. Study on spins and deformation rate in finite torsion deformation is the key to determine the material parameters by torsion experiments and understand the finite deformation characteristics of material. In this paper, five spins and deformation rate in torsion deformation with solid circular shafts are investigated in cylinder coordinates. The expressions of the deformation rate and spins, namely the material spin, the relative spin, the spin of the frame of the deformation rate, logarithmic spin and instantaneous spin considering the effect of stress, are deduced by analyzing the finite torsion deformation. The comparisons are made among all spins obtained in this paper. The results obtained in this paper are the basis of analyzing the large strain constitutive relationship based on torsion experiments with solid circular shafts.