Jiye Chen

Bone–cement interfacial behaviour under mixed mode loading conditions

Interfacial behaviour of the bone-cement interface has been studied under tensile, shear and mixed mode loading conditions. Bovine cancellous bone was used to bond with acrylic bone cement to form bone-cement interface samples, which were mechanically tested under selected tensile, shear and mixed mode loading conditions. The influence of the loading angle and the extent of the cement penetration on the interfacial behaviour were examined. The failure mechanisms with regard to loading mode were examined using micro-focus computed tomography. The measured tensile and shear responses were utilized in a cohesive zone constitutive model, from which the pre-yield linear and the post-yield exponential strain softening behaviour under mixed mode loading conditions was predicted. The implications of the work on the studies of cemented joint replacements are also discussed.

A Numerical Investigation of Thermal-related Matrix Shrinkage Crack and Delamination in Composite T-Piece Specimens Using a Modified Interface Cohesive Model

This article numerically investigated the curing temperature effect on matrix shrinkage crack and the effect of matrix shrinkage cracking on delamination in composite T-piece specimens using a modified interface cohesive model with thermal effects accounted. Thermal relative coefficient was introduced to produce the relative thermal displacement in the formulation of interface cohesive elements. The thermal shrinkage crack in the deltoid region of T-piece was simulated. Effect of this thermal initial cracking on the prediction of dominated delamination [Chen, J., Ravey, E., Hallett, S., Wisnom, M. and Grassi, M. (2009). Prediction of Delamination in Braided Composite T-Piece Specimen, Composites Science and Technology, 69(14): 2363–2367; Chen, J. (2011) Simulation of Multi-directional Crack in Braided Composite T-Piece Specimens Using Cohesive Models, Fatigue & Fracture of Engineering Materials & Structures, 34(2): 123–130.] of T-piece under T-pull loading case was also studied. The investigation indicated that some improper restraints to T-piece specimens during the curing process will induce so called thermal shrinkage cracks in the deltoid region of T-piece. This sort of thermal related matrix shrinkage crack has limited effect on the capacity of T-piece to resist T-pull loading. Radius laminates are the main load carrier in the T-pull loading case. This modeling investigation supplied considerable information for the design and manufacture of T-piece related composite components under pulling condition. Further investigation considering loading cases such as bending and combination with bending and T-pull is suggested in the future work to explore general effects of thermal related matrix shrinkage cracking on delaminating.

Modelling behaviour of ultra high performance fibre reinforced concrete

Abstract The cohesive crack model (CCM) is the most commonly accepted discrete crack approach for modelling concrete based materials. It is applied to ultra high performance fibre reinforced concrete (UHPFRC) in this study because it can be easily represented as cohesive interface elements in finite element modelling. Cohesive crack model using a bilinear traction–separation relationship is used to simulate the load–deflection behaviour of UHPFRC test specimens. Cohesive crack model based numerical simulation of three-point bend specimens are implemented using cohesive elements in ABAQUS FE software. Progressive crack propagation and failure mechanism of UHPFRC test specimens are simulated in order to predict their load capacities. Comparison of the simulation to existing experimental test results indicates that CCM with a bilinear traction–separation curve can provide predictions of both the load–deflection curves and peak load of 100 and 150 mm deep UHPFRC test specimens to  = /−6% of the average for 50 and 100 mm wide beams and to  = /+20% for 150 mm wide beams. Model predictions of the peak load for the 50 mm wide and 50 mm deep beams were to  = /−25% of the average.

A highly efficient numerical approach: extended cohesive damage model for predicting multicrack propagation

Abstract A highly efficient numerical approach: extended cohesive damage model (ECDM) for predicting multicrack propagation is introduced in this paper. The ECDM is developed within the framework of the eXtended Finite Element Method (XFEM). Unlike XFEM the enriched degrees of freedom (DoFs) are eliminated from the final condensed equilibrium equations in the ECDM. To account for the cohesive crack effect, an equivalent damage scalar relating to a strain field is introduced in terms of energy dissipation. The ECDM is capable of characterizing discontinuities with conventional DoFs only, thus it is significantly efficient in modelling multicrack propagation. The basic formulations, numerical implementation and detailed investigation of the performance of the ECDM through modelling the selected benchmark specimens are given in this paper. This investigation shows the ECDM can effectively guarantee the convergent solutions in nonlinear fracture analysis and can efficiently reduce the computer CPU time in modelling selected fracture benchmark specimens by more than 60% compared to the XFEM in ABAQUS. Therefore, the ECDM is a robust computational approach for predicting multicrack failure mechanism in engineering materials and structures.

Extended digital image correlation method for mapping multiscale damage in concrete

AbstractThis paper presents a novel extended digital image correlation (EDIC) method for mapping multiscale damage in concrete. The EDIC method is developed based on the distance transformation alg...