Papers by Keyword: Mixed-Mode Fracture

Abstract: A major difficulty in simulating load response of a concrete structure in mixed-mode fracture lies in the fact that crack path is not known a priori. Predicting both the crack path and the associated load response involves advanced simulation techniques and novel numerical methodologies. Here, an intrinsic cohesive crack model is employed to study mixed-mode fracture in a concrete beam. The present approach requires neither preliminary results from linear elastic fracture mechanics simulations nor a re-meshing procedure or special implementation to prevent crack locking. Simulations with regular meshes illustrate that this concise approach can provide a reasonable estimation of peak load of the pre-cracked concrete beams in mixed-mode fracture. This study shows that the energy ratio in the bilinear softening law has larger effects than the stress ratio.

Abstract: In this research mixed-mode fracture behaviour of glass fibre/epoxy composite with randomly distributed glass fibres investigated. Various modes of loading were applied. Compact tension shear (CTS) fixture with different loading angles were used. The testing is used to measure the fracture toughness. Critical strain energy release rate (CSERR) of the composite was then calculated using the measured fracture toughness. A model is proposed to predict the value of CSERR based on the constituents and interfacial properties. Different failure mechanisms are considered in developing a criterion. To derive the criterion a FE model is used to determine the amount of energy released during the fibre pull out which is major part of energy dissipation.

Abstract: In this work, a new damage model for mixed-mode fracture in the scope of the discrete crack approach is introduced. An energy-based internal damage variable is adopted. In the model, deformation-driven loading surfaces are defined and the dual loading surfaces in the traction space are derived. Under proportional loading, it is found that the constitutive relationship is symmetric. Further enrichment of the energy-based variable on the traction field is also introduced, allowing for a better approximation of: i) the limit surface defined in traction space and ii) non-proportional loading. However, in this case symmetry of the constitutive tensor is lost.

Abstract: The objective of this work is to develop fracture simulations of rubber undergoing a combined tensile and out-of-plane shear loading. Rubber sheets are tested under mode-I (opening mode), mode-III (tearing mode) and mixed-mode [I/II of fracture. The experiments are simulated in finite element software to evaluate the J-integral for each mode of deformation. Comparison between simulation and testing results are in good agreement. The simulations serve as test cases and evaluation tools for the development of mixed mode fracture criterion of rubber.

Abstract: Aluminum alloy 5083 is taken for the study of fracture parameters in mixed-mode I/III. Three point bend specimens with load inclination and notch inclination are fabricated and precracked. They are tested with various inclination angles and for two different thicknesses. The results are analyzed and found that the fracture toughness decreases for larger inclination angles. Also, it is found that the thinner specimens are found to be tougher than the thicker specimens. Material and methods Symmetrical three-point bend cracked specimens have been used extensively in fracture mechanics to study mode I fracture properties because they are one of the standard types of specimens used in the ASTM codes for determining the fracture toughness J_Ic._. In the mixed-mode I/III fracture, there is only a limited amount of experimental work done so far. The observations on combined mode I - mode III fracture have been very scarce and there is no general agreement among researchers on the effect of the addition of a mode III component to pure mode I loading. Limited study (Avci et al 2005 [, Kamat and Hirth 1996 [) has been done on bend specimens subjected to mixed-mode I/III when compared to the mode I case, i.e., a center-loaded specimen.

Abstract: The length of crack extension under stable crack extension is measured by digital image correlation technology and based on mixed-mode I/II fracture test. Quantitative analyses of the fracture properties are provided for thin sheet metals at stable crack extension under mode I, mode II and mixed-mode I/II loading conditions. The strain field of the crack tip at crack initiation is calculated by VIC-2D. It is suggested that the location of crack initiation is not at the crack tip. The fracture of recycled thin sheet metals is tough due to the large plastic deformation; mode I crack is the most difficult to extend; the load-carrying capacity is the minimum in 45° loading.

Abstract: Using the asymmetric semi-circular bend specimen (ASCB) a set of mixed-mode fracture tests were carried out in the full range from pure mode I to pure mode II. The tests were conducted on two polyurethane materials characterized by different properties. The fracture parameters were obtained from experiments and are compared with the predictions based on the generalized MTS criterion (GMTS). The agreement between the experimental results and those predicted based on the GMTS criterion is discussed finally.

Abstract: A new criterion (failure stress criterion) is presented for the mixed-mode fracture of concrete by comprehensively evaluating several mixed-mode crack criteria. The new criterion absorbs some results fitting in with concrete from G.C.Sih and Erdogen’s maximum circumference stress criterion and G.C.Sih’s minimum strain energy intensity factor criterion. It combines concrete material fracture property with the condition of loads at the moment of concrete fracture by Weibull theory. It is concluded that concrete crack expands neither along the direction of maximum circumference stress nor along minimum strain energy factor S. The crack extends along the direction limited in the area controlled by two criteria. The accurate crack position is determined by failure probability of the strength of concrete structure. The experimental results indicate that the new criterion has better precision and adaptability comparing with other criteria and it can be applied to engineering very well.

Abstract: The computational analysis of a three-dimensional (3D) finite element model of all fracture modes (AFM) specimen on mixed-mode I-II fracture was presented in this paper. The separated energy release rates (SERRs) along the crack front of the AFM-model were calculated by the modified virtual crack closure integral (MVCCI)-method and commercially available software ANSYS. The influence of finite geometry and loading angles on mixed mode I-II fracture was investigated.

Abstract: The bonding of fiber reinforced polymer (FRP) strips and plates to the concrete structures has been found to be an effective technique for flexural strengthening. The FRP is then under both pulling and peeling forces, resulting in a combination of shear sliding and opening displacement along the FRP/concrete interface. A novel experimental set-up is studied that a peeling load is applied on the FRP sheet by a circular rod placed into the central notch of the beam. Based on the linear-elastic fracture mechanics approach, a theoretical analysis is conducted on specimens representing the peeling behavior. From the numerical analysis, the load–displacement curves, load–stiffness of FRP sheet curves, and load–fracture energy curves affected by different variables are discussed. The peel load is related to the FRP sheet stiffness and to the interfacial fracture energy. Therefore, only two material parameters, the interfacial fracture energy of FRP–concrete interface and stiffness of FRP sheets, are necessary to represent the interfacial fracture behavior. The theoretical load–deflection curves of specimens agree well with the corresponding experimental results in the literatures.