Narrow Results

To solve the problem of rail crack propagation, inadequate studies mainly use a two-dimensional (2D) model for macroscopic crack analysis owing to the failure of accurately reflecting the contact status between the wheel and rail. In this work, we use ANSYS software to establish a three-dimensional (3D) wheel–rail contact model to clarify the microcracks on the rail tread. The influence of the number of horizontal and vertical cyclic loads during the rail’s fatigue crack growth is analyzed. The results suggest that as the number of vertical and tangential cyclic loads increases, the length of the rail crack increases. Using experiments to verify the law between the number of cyclic loads and rail crack growth length, the experimental findings proved that the law of crack growth is basically consistent with the aforementioned simulation results and the outcome of the Paris expansion curve, verifying the validity of the simulation results.

Premium threaded connections (PTCs) act as an important part to connect the martensitic stainless-steel tubes in deep wells under the co-action of cyclic loads by axial tension–compression and radial internal–external pressure. Local elasto-plastic deformation and crack are usually found to occur at PTCs, which result in leakage, raw material waste and environmental pollution. Therefore, predicting the deformation behaviours of PTCs and then to find the load boundary for crack mean a lot. However, since the obvious anisotropy, tension–compression asymmetry and Bauschinger effect of the material dynamically evolve with deformation, the challenge for modelling lies in the determination of mass of constitutive parameters which also dynamically evolves with deformation. To solve the problems above, a J2–J3 anisotropic yield criterion together with an Armstrong–Frederick (A-F) kinematic hardening equations are adopted in this work, and a microstructure-based crystal plasticity finite element model (CPFEM) is utilised to produce data for the determination of constitutive parameters. The established model is applied to predict the local elasto-plastic deformation of PTCs to investigate the rule of plastic strain distribution and the effects of cyclic load on it. The results show that the Bauschinger effect caused by the cyclic internal pressure has a large impact on the deformation of PTCs in the early few cycles. The radial internal pressure is the main factor that causes high contact stress and the accumulation of plastic deformation at the sealing surface and the shoulder of PTCs. The combined effect of radial internal pressure and axial tension exits and extremely large magnitude of load (tension force > 1400 MPa, compression force >1000 MPa) may cause failure of PTCs.

Railways form one of the major worldwide transportation networks and they continue to provide quick and safe public and freight transportation. In order to compete with other modes of transportation and to meet the ever growing demand of public and freight transport, railway industries face challenges to improve their efficiency and decrease the costs of maintenance and infrastructure. Large cyclic loading from heavy haul and passenger trains often leads to progressive deterioration of the track. The excessive deformations and degradations of the ballast layer and unacceptable differential settlement or pumping of underlying soft and compressible subgrade soils necessitate frequent costly track maintenance works. Hundreds of millions of dollars are spent each year for the construction and maintenance of rail tracks in large countries like the USA, Canada and Australia. A proper understanding of load transfer mechanisms and their effects on track deformations are essential prerequisites for designing the new track and rehabilitating the existing one. The reinforcement of the track by means of geosynthetics leads to significant reduction in the downward propagation of stresses and assures more resilient long-term performance. The geocomposite (combination of biaxial geogrid and non-woven polypropylene geotextile) serves the functions of reinforcement, filtration and separation, thereby reducing the vertical and lateral deformations.

To stabilise subgrade soil under rail tacks and road embankments, two advanced ground improvement schemes have been introduced. Stabilization of soft subgrade soils using prefabricated vertical drains (PVDs) is essential for improving overall stability of track and reducing the differential settlement during the train operation. The effectiveness of using geocomposite geosynthetic and PVDs has been observed through field measurements and elasto-plastic finite element analyses. These have been the first fully instrumented, comprehensive field trials carried out in Australian Railways, and it was very encouraging to see the field observations matching the numerical predictions. Moreover, the improvement of an unstable formation soil with pH neutral chemical admixture and the sub-surface drainage is described. Internal erosional behaviour of lignosulfonate treated erodible soils has been studied using the Process Simulation Apparatus for Internal Crack Erosion (PSAICE) designed and built at the University of Wollongong (UOW). Effectiveness of lignosulfonate treated erodible soils on the erosion resistance has been investigated and its advantages over conventional methods are presented and discussed.

A one-third scale, five-story steel staggered structure with Pratt truss was tested under cyclic loading firstly to study the seismic performance of this structural system. Based on the test results, the failure mode, as well as its bearing capacity, ductility, stiffness, and energy absorbing ability, were obtained. At last, conclusions and suggestions were put forward for design based on the results of experimental results.

Based on the test results of a one-third scale, five-story steel staggered structure with Pratt truss under cyclic loading, a finite element (FE) model was established and verified by comparing the numerical results with test ones. In general, they agreed well. After that, a series of 18-story Pratt truss buildings were designed, and numerical analysis was carried out by using the FE model to study the influences of some main parameters on seismic behavior of this structural system, including height to width ratio of building, aspect ratio of truss, height to width ratio of open-web panel, and truss arrangement in ground floor. At last, conclusions and suggestions were put forward for design based on the results of numerical analysis.