Papers by Keyword: Fracture

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Authors: Glenda T. Motsi, Peter A. Olubambi, Tleyane J. Sono, Lerato Shoke
Abstract: In this study tensile deformation mechanisms of aluminium alloy 5083 were investigated under observations made from SEM equipped with a tensile stage. Observations during tensile testing revealed a sequence of surface deformation events. These included micro-cracking of large intermetallic particles, decohesion of small intermetallic particles from the matrix producing microvoids and slip bands distribution. The fracture surface was characterised with closely spaced dimples, typical for aluminium alloys.
Authors: Jian Ping Wang, He Jia Liu, Shao Kai Sun, Shi He Jian
Abstract: To provide the doctors a basis for treating sacral fractures and offer optimal surgical program, three-dimensional (3D) finite element method was used to simulate normal pelvis and the unstable pelvis sufferedIsection, IIsection and III section sacral fracture respectively.The unstable pelvises were respectively fixed with five different internal fixation implants types, which are respectively rectangular plate with cannulated screw, rectangular plate with solid screw, expansile bolt, convex plate with cannulated screw, convex plate with solid screw. The stress distribution and the X, Y, Z direction displacement of the sacrum were calculated for each sacral fracture treatment of five internal fixation implants after giving 500N axial load on lumbar vertebra and were compared with the normal pelvis, then the optimal surgery program were determined. After the analysis, by comparing the five combinations for each sacral fracture treatment of five internal fixation implants, the preferred combinations for the reset treatment of theIsection sacral fractures were rectangular plate with cannulated screw and convex plate with cannulated screw; The preferred combination for the reset treatment of the II section sacral fractures was expansile bolt; The preferred combination for the reset treatment of the III section sacral fractures was convex plate with cannulated screw.
Authors: Han Wang, Ming Hao Zhao, Ji Gao, Guang Yuan Wang
Abstract: Concrete is usually described as a three-phase material, where matrix, aggregate and interface zones are distinguished. The beam lattice model has been applied widely by many investigators to simulate fracture processes in concrete. Due to the extremely large computational effort, however, the beam lattice model faces practical difficulties. Moreover, real fracture processes are 3D and not 2D. In our investigation, a new 3D lattice called generalized beam (GB) lattice is developed to reduce computational effort. Numerical results obtained by the model are in agreement to what are observed in tests. The 3D effects of the particle content on the peak load and ductility are discussed as well as the 3D fracturing phenomenon.
Authors: Chun He Yang, Guibin Wang, Liming Yin
Abstract: Based on the field geology survey data, the probability distribution function of joint aperture was analyzed and the availability of the fitting data was verified. The joint aperture data observed the previous fitted function can be generated in the process of joint simulation. The seepage of rock mass is proportional to the third power of joint’s aperture. It is much more reasonable and feasible to analyze the permeability tensor of rock mass with the previous generated data. At the same time, the method comprehensively considered the effect of joint’s orientation, aperture, scale and their distribution.
Authors: Yu Zhou Sun, Dong Xia Li, Hui Wang
Abstract: This paper presents a boundary element-free computational method for the fracture analysis of 2-D anisotropic bodies. The study starts from a derived traction boundary integral equation (BIE) in which the boundary conditions of both upper and lower crack surfaces are incorporated into and only the Cauchy singular kernal is involved. The boundary element-free method is achieved by combining this new BIE and the moving least-squares (MLS) approximation. The new BIE introduces two new variables: the displace density and The dislocation density. For each crack, the dislocation density is first expressed as the product of the characteristic term and unknown weight function, and the unknown weight function is approximated with the MLS approximation. The stress intensity factors (SIFs) can be calculated from the the weight function. The examples of the straight and circular-arc cracks are computed, and the convergence and efficiency are discussed.
Authors: Liang Wu, Ze Li, Shang Huang
Abstract: The cohesive crack model and the crack band model are two convenient approaches in concrete fracture analysis. They can describe in full the fracture process by the different manner: The entire fracture process zone is lumped into the crack line and is characterized in the form of a stress-displacement law which exhibits softening; or the inelastic deformations in the fracture process zone are smeared over a band of a certain width, imagined to exist in front of the main crack. The correlation of the two models is developed based on a characteristic width of crack band. The analysis shows that they can yield about the same results if the crack opening displacement in the cohesive crack model is taken as the fracturing strain that is accumulated over the width of the crack band model. Some basic problems are also discussed in finite element analysis.
Authors: Jarosław Kaczmarek, Wiesław M. Ostachowicz
Abstract: In this paper we introduce nanoscale description of fracture in a single crystal in order to obtain foundations for modelling damage at more averaged scale. Nanoscale model of fracture is discussed together with nanoscale model of slip plasticity. Fracture systems and slip systems are introduced consistently by means of free energy. They enable us to express critical conditions for initiation of both crack and slip. Evolution equations which describe evo- lution of crack, slip and boundary of slip surface are introduced. Furthermore, we also discuss crack initiation and propagation on active slip surface. With the aid of variables characterizing damage at nanoscale level we discuss the form of damage tensor for more averaged model. One discusses larger context of nanoscale modelling in which the nanoscale models are considered as a segment of multiscale description of behaviour of materials.
Authors: Catalin Cirstoiu, Razvan Ene, Dan Popescu, Monica Cîrstoiu
Abstract: In surgical experiences of the fractures of the proximal tibia, which are named tibial plateau fractures, with important damage of the articular surfaces of the tibia is very important to realise a correct reduction and an adequate osteosinthesys . But in real time this is a very difficult aim, because the correct reduction by various methods, induced an important bone deficiency. This is the principal aspect of the proximal tibial reconstruction, because this reconstruction s essential for the stability of the implant, for the correct reduction, for the correct allignemment of lower limb and for the reduction of the malunions results, for the abnormal consolidations and for devloppemment of the ostheoarthritis of the knee.We have two posibilities to reduce the bone gap - with bone grafts , by collaboration with the National Bone Bank , or by using a bone substituent - a new method of reconstruction.In our opinion, the bone graft is the perfect solution for recent fracture and the bone substituent is indicated for the severe difformities secondaries of articular surface.
Authors: Zhan Guo Wei, Xu Feng Cheng, Jin Hao Liu
Abstract: ROPS is an effective way to reduce casualty rate in the rolling accident. This paper introduces the design of a cab to strengthen safety-ROPS large wheel loader method. The finite element model, it's a ROPS rear, absorbers and supporting structure frame of the safety-cabs, was created. Force and displacement boundary conditions obtained in accordance with the international standard ISO3471:2008-The large deformation elastic-plastic finite element analysis, horizontal, vertical and ROPS vertical load cases of performance testing and the corresponding lab for investigation. The test results show that the design can meet the requirements of ISO3471 ROPS: 2008. Test results differences and simulation and welded joint of the fracture analysis on the reason.
Authors: A. Arteiro, Giuseppe Catalanotti, J. Xavier, P.P. Camanho
Abstract: A new model based on Finite Fracture Mechanics (FFMs) has been proposed to predict the open-hole tensile strength of composite laminates [1]. Failure is predicted when bothstress-based and energy-based criteria are satisfied. This model is based on an analytical solution, and no empirical adjusting parameters are required, but only two material properties: the unnotched strength and the fracture toughness. In the present work, an extension of the proposed FFMs model to predict the notched response of composite laminates with notch geometries other than a circular opening [2] is presented and applied to the prediction of size effects on the tensile and compressive notched strength of composite laminates. The present model is also used to assess the notch sensitivity and brittleness of composite laminates by means of versatile design charts and by the identification of a dimensionless parameter designated as notch sensitivity factor. A further extension of the FFMs model is proposed, which takes into account the crack resistance curve of the laminate in the model's formulation, and it is used to predict the large damage capability of a non-crimp fabric thin-ply laminate [3].
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