Papers by Keyword: Energy Release Rate

Abstract: In this paper a new formalism based on the complementarity between the optical full field techniques and integral invariant Mtheta is proposed in order to evaluate the fracture parameters in cracked specimen made of wood, under mixed mode loadings. The coupling between the experimental and numerical approaches allows identifying the fracture parameters in terms of energy release rate without any the material elastic properties such as the elastic modulus and the Poissons ratio. The proposed formalism allows also determining, in addition with the fracture parameters, the local elastic properties in terms of reduced elastic compliance. The fracture mixed mode tests are realized using a Single Edge Notch sample made in Douglas with the Arcan fixtures and dried to 11% moisture content and the crack is cutting in Radial-Longitudinal system.

Abstract: Double-G fracture model was recently proposed based on the conception of energy release rate to describe the fracture behaviour on cracked concrete. Two fracture parameters, i.e., the initiation fracture energy release G_Icⁱⁿⁱ and the unstable fracture energy release G_Ic^un, are termed to distinguish the different crack propagation stages undergoing during the whole fracture process in concrete. In present work, following the Double-G fracture model at ambient temperature, the residual Double-G fracture parameters of post-fire concrete is elaborately introduced. Totally ten temperatures varying from 20oC to 600oC and the specimens size of 230×200×200 mm with initial-notch depth ratios 0.4 were considered. Wedge-splitting method is adopted to measure the loadcrack mouth opening displacement curves (PCMOD) and double-G fracture parameters are experimentally determined.

Abstract: Two fracture parameters, i.e., the initiation fracture energy release G_Icⁱⁿⁱ and the unstable fracture energy release G_Ic^un, are termed to distinguish the different crack propagation stages. Totally ten temperatures varying from 20oC to 600oC and the specimen size of 230×200×200 mm with initial-notch depth ratios 0.4 were considered. Wedge-splitting method is adopted to measure the loadcrack mouth opening displacement curves (PCMOD) and double-G fracture parameters are experimentally determined. In order to verify the feasibility of this model in post-fire concrete, the effective double-K fracture parameters converted by double-G fracture parameters using are compared with the double-K fracture parameters.

Abstract: The double cantilever beam (DCB) test method and the modified beam theory are adopted to investigate the Mode I interlaminar fracture toughness of multi-directional composite laminates. The test procedure was developed by using a stereoscopic microscope to observe the delamination front tip and a testing machine to record the displacement and load data. A dial indicator was used to eliminate the error due to initial clearance in the clamp. A modified beam theory and a compliance calibration method were used to calculate the interlaminar fracture toughness. The Mode I interlaminar fracture toughness of carbon fiber reinforced bismaleimide resin matrix (BMI) composite laminates with four different interface patterns ( 0/0, 45/-45, 0/-45 and 0/90, respectively) was obtained. The results show that the patterns of interface ply angles have an obvious influence on Mode I interlaminar fracture toughness of composite laminates.

Abstract: The engine knock has direct relation with the energy release rate. The faster combustion speed is, the higher heat release rate is. If heat release rate is too high, it will deteriorate reliability of the engine. A dual-fuel engine combustion mechanism model is established and intake pressure boundary conditions influence on the dual-fuel engine reliability is studied. Injection timing can supress engine knock and inprove engine reliability. Studies have shown that the greater the intake pressure, the smaller injection timing should be selected and the smaller the intake pressure, the larger injection timing should be selected. Appropriate injection timing can ensure reliability and power of the engine.

Abstract: The paper reviews the numerical methodology to investigate fracture parameter namely energy release rate, G, of a mixed mode crack. An inclined, through, centre crack is assumed in a ductile steel plate subjected to bi-axial tension. Applied stress and crack size are suitably selected to simulate small scale yielding (SSY) condition at the crack tips. The cracked plate is modelled by finite element method. Both plane stress and plane strain situations are examined. G value is found from J integral. Equations of transformation are employed to obtain normal and shear stress in the plane of the crack. G is then again determined for Mode I and Mode II cracks by modelling each case separately. The analysis is finally validated by fulfilment of the conservation of energy release rate criterion, G (Mixed mode) = G (Mode I) + G (Mode II).

Abstract: The delamination at the interface between the aluminium and prepreg layers has greater influence on the fatigue crack growth in fiber metal laminates. To study delamination propagation property of one kind of new fiber metal laminates, by using 2/1 lay-up specimen, this article accomplished delamination propagation test under various stress levels at R=0.1 by optical method and compliance method respectively. The delamination propagation property of this laminate is obtained by analyzing and calculating. A modified compliance equation is created to calculate the delamination size of this laminate more accurately by adding a non-dimensional factor.

Abstract: Finite element method is carried out to calculate the fracture mechanics parameter of interfacial cracking of TSOP (Thin Small Outline Package). Fracture mechanics approach together with finite element results are used to study the impacts of material properties and thickness of die attach on the energy release rate at crack tip of interfacial delamination between die pad and die attach. The results show that larger Young’s modulus, smaller CTE as well thinner thickness of die attach can reduce ERR at crack tip during reflow.

Abstract: This paper deals with the advantages of the finite element modeling and design, especially, of delamination test coupons involved in fracture analysis of laminated composite plates. This is shown through two relevant aspects in delamination toughness measuring, say: data reduction and Iso-G delamination front design. Many experimental data reductions are based on beam theories and thus assumes straight delamination front during propagation, which is not true when investigating laminates with general anisotropy. Another aspect is also emphasized, and concern test procedure simplification to avoid displacement measurements. This is done through a direct energy release rate calculations via the crack closure integral method.

Abstract: The interfacial reinforcement with interlaminar chopped fibers of piezoelectric composite under impact electro-mechanical load was studied using nonlinear finite element method. A meso- mechanical model based on the main toughness reinforcement mechanism of single fiber bridging and pull out was adopted, and then a tri-linear bridging law was obtained, while the interface chopped fibers by defining nonlinear bidirectional spring elements between coincident nodes on the two crack surfaces within bridging zone and the energy release rate was calculated using the virtual crack closure technique. The numerical investigation indicates that the interlaminar chopped fiber can effectively reduce the crack tip energy release rate whether the applied voltage is positive or negative, which was an effective technique improve the interfacial toughness of the piezoelectric composite adhesive structure.