Papers by Keyword: Progressive Failure

Abstract: The article is devoted to the description of analytical and structural methods used in the design to avoid progressive collapse of buildings and structures in the case of extreme influences. Three directions are described to avoid the process of development of local to global destruction. The concept realized in the LIRA-SAPR software, which is aimed at automating analysis for progressive collapse in quasi-static and dynamic formulations, including linear and nonlinear analysis taking into account the dynamic factor, is also substantiated. The purpose of the analysis is to design structures for various purposes, which in addition to accident-free performance of functions during the specified period of operation, in case of an accident due to natural and man-made phenomena (defects in production technology, explosions, impacts), as well as other causes not provided for by the conditions of normal operation, would cause minimal damage to people and the environment.

Abstract: Composite overwrap systems have been widely used to repair damaged pipelines. Its effectiveness has been proven by many researches and engineering applications. However, the research on progressive failure mode of the repaired structure has not been reported. In the present paper, finite element method with Hashin failure criteria is developed to realize the progressive failure analysis. The predicted burst pressure is in good agreement with the burst experiment. Different from widely-reported failure progress in Composite Overwrapped Pressure Vessels (COPV), the progressive failure analysis for the defected pipeline overwrapped by composite reveals very different failure stages: stable failure propagation and rapid failure propagation. The identification of critical pressure between these two stages is valuable in composite reparation design for the defected pipeline.

Abstract: This paper presents a methodology to carry out Reliability-Based Design Optimization (RBDO) in composite stiffened panels. The target is to maximize the reaction force that the panel can withstand before collapse, setting the shortening of failure as the probabilistic constraint. The design variables are the stacking sequence orientations of the composite plies while the random parameters are the elastic properties of the material. In order to predict the collapse load properly, post-buckling and progressive failure analyses are considered within the FE solver employed.

Abstract: A novel experimental method was proposed for characterizing the energy absorbing capability of composite materials during the progressive crushing process under impact loading. A split Hopkinson pressure bars system was employed to carry out the progressive crushing tests under impact loading. The stress wave control technique was used to avoid the inhomogeneity of dynamic stress field in the specimen. The progressive crushing behavior was successfully achieved by using a coupon specimen and anti-buckling fixtures. With increasing strain rate, the absorbed energy during the crushing process slightly decreased, whereas the volume of the damaged part clearly increased regardless of material type. Consequently, the energy absorbing capability decreased with increasing loading rate. The effects of material composition, such as fiber type, matrix type and fabric pattern, on energy absorbing capability were also investigated by using the proposed method.

Abstract: This study presents the details of experimental and analytical investigations on three different types of composites on their progress to failure under varied type of loadings. The composites are glass/epoxy-GFRP, Kevlar/epoxy-KFRP and Carbon/epoxy-CFRP composites. A series of experiments were carried out to find the variation in mechanical properties in all composites due to displacement controlled tests with different displacement rates such as 0.5mm/min, 1.0 mm/min and 1.5mm/min. The experimental results for CFRP, GFRP and KFRP under three different zones of response viz., stage I- response upto design load-DL, stage II-later from design load to ultimate load-UL followed by Stage II-response upto failure load-FL were discussed. Comparisons of relative performance under different rates and types of damage occurred are discussed from strength, stiffness and energy points of view.

Abstract: The aim of this work is to introduce a novel constitutive material model for the progressive failure analysis of composite laminates able to predict the Gradual degradation of laminates up to their complete failure. As a relevant added value with respect to state of the art constitutive models, the presented model uses energy considerations to avoid mesh and time-step dependences. In order to prove its effectiveness and accuracy, the proposed material constitutive model has been implemented in the FE software ANSYS© as a User defined material subroutine (USERMAT) and used to simulate the mechanical behavior of an Open Hole Tension specimen. The obtained numerical results have been compared to experimental literature data and to the numerical outputs of Instantaneous and Standard Gradual Degradation Models.

Abstract: A novel experimental method was proposed for characterizing the compressive properties of composite materials under impact loading. Split Hopkinson pressure bar system was employed to carry out the dynamic compression tests. The dynamic stress-strain relations could be precisely estimated by the proposed method, where the ramped input, generated by the plastic deformation of a zinc buffer, was effective to reduce the oscillation of the stress field in the specimen. The longitudinal strain of gage area could be estimated from the nominal deformation of gage area, and consequently the failure process could be grasped in detail from the stress-strain relation. The dynamic compressive strength of the material was slightly higher than the static compressive strength. In addition, the validity of the proposed method was confirmed by the computational and experimental results.

Abstract: The progressive failure study of the slope is a challenging problem. There exist a lot of problems at present in this area, it’s necessary to do some summaries. This paper did some analysis and discussion from four aspects: limit equilibrium analysis of the slope progressive failure; test analysis of the slope progressive failure, numerical simulation of the slope progressive failure and limit equilibrium analysis on the basis of finite element, and provided some reference for slope progressive failure study.

Abstract: Uniform safety factors are normally assumed in slope stability analysis and this assumption can influence the rationality of the analysis. New analysis methods were obtained based on Fellenius, Bishop and multi sliding surface method to study a failed slope of a port in southern China. The calculation results show that the safety factors of soft soil layers will be overestimated and the safety factors of hard soil layers will be underestimated if soil mass of slope vary widely in the strength. For the failed slope in this paper, the factors obtained with normal methods will be overestimated because of the hard soil layer of this slope.

Abstract: Braided composite tubular structures are of interest as viable energy absorbing components to improve vehicle passive safety. Unfortunately, there are many difficulties in predicting the crash response of braided composite tubes. In this study, a progressive failure model for braided composite materials, which had been implemented as a user material model in ABAQUS/Explicit, was used to simulate the axial crash response of braided composite tubes. It was shown that the model adequately captured the failure characteristics (such as matrix cracking, fiber fracturing and delamination) and energy absorption of braided composite tubes under axial compression. In addition, the simulation results show that braided composites have higher energy absorption performance compared to traditional metals.