Progressive Failure Simulation Research Articles

Progressive failure simulation in laminated composites under fatigue loading by using discrete damage modeling

The discrete damage modeling method is extended for progressive failure analysis in laminated composites under fatigue loading. Discrete damage modeling uses the regularized extended finite element method for the simulation of matrix cracking at initially unknown locations and directions independent of the mesh orientation. A material history variable in each integration point is introduced and updated after each loading increment, corresponding to certain load amplitude and number of cycles. The accumulation of the material history variable is governed by Palmgren-Miner’s rule. Cohesive zones associated with mesh-independent cracks are inserted when the material history parameter reaches the value of 1. Cohesive zone model consistently describing crack initiation and propagation under fatigue loading without any assumption of initial crack size is proposed. The fatigue properties required for matrix failure prediction include shear and tensile S-N curves as well as Mode I and II Paris law parameters. Tensile fiber failure is assumed unaffected by fatigue. All input data required for model application are directly measured by ASTM tests except tensile fiber scaling parameter and compression fiber failure fracture toughness, which were taken from literature sources. The model contains no internal calibration parameters. Fatigue damage extent, stiffness degradation and residual tensile and compressive strength of IM7/977-3 laminates have been evaluated. Three different layups, [0/45/90/-45]2S, [30/60/90/-60/-30]2S and [60/0/-60]3S, were modeled and tested. The predictions captured most experimental trends and showed good agreement with X-ray CT damage assessment; however, significant further work is required to develop reliable methodology for quantitative composite durability prediction.

Integrated XFEM-CE analysis of delamination migration in multi-directional composite laminates

Progressive damage and failure in composites are generally complex and involve multiple interacting failure modes. Depending on factors such as lay-up sequence, loading and specimen configurations, failure may be dominated by extensive matrix crack-delamination interactions, which are very difficult to model accurately. The present study further develops an integrated extended finite element method (XFEM) and cohesive element (CE) method for three-dimensional (3D) delamination migration in multi-directional composite laminates, and validates the results with experiment performed on a double-cantilever beam (DCB). The plies are modeled by using XFEM brick elements, while the interfaces are modeled using CEs. The interaction between matrix crack and delamination is achieved by enriching the nodes of cohesive element. The mechanisms of matrix fracture and delamination migration are explained and discussed. Matrix crack initiation and propagation can be predicted and delamination migration is also observed in the results. The algorithm provides for the prediction of matrix crack angles through the ply thickness. The proposed method provides a platform for the realistic simulation of progressive failure of composite laminates.

Optimization of structural contact stiffness and strength for discrete simulation of progressive failure of healed structure

AbstractGeotechnical analysis for underground excavation design in complex tectonic environments requires an increased understanding and more rigorous consideration of the impact of healed or "intrablock" structure, such as veins, on rockmass behaviour. Intrablock structure occurs between blocks of rock defined and bounded by "interblock structure", the network of joints and other fractures conventionally considered in classic rockmass characterization, classification or rockmass property estimation. Discrete simulation of fractures has become a more commonplace model analysis technique for excavations in jointed rockmasses. Here too, however, special attention is required to simulate intrablock structure within the model. In particular, the selection and evolution of stiffness and strength values for the model discontinuity elements must follow a different logic than that adopted for fractures and true joints. A new concept to better represent the behaviour of intrablock structure in explicit numerical models is proposed and tested in this paper by means of finite element method (FEM) analysis and case study data from a 1, 200 m deep drift. This approach changes the stiffness and strength values of failed intrablock structural elements between pre‐peak ("primary"), post‐peak ("secondary"), and ultimate ("tertiary") states. The FEM models in the tertiary state match 96 % of overbreak patterns along the case drift, versus 80 % in primary state models. These findings suggest that the proposed method is a good option to more accurately model the influence of intrablock structure on rockmass behaviour.

Modelagem simplificada do processo de fissuração e colapso em pórticos e arcos de concreto armado

A simulação consistente de processos de falha progressiva e colapso estrutural ainda é um problema aberto de grande interesse para a engenharia. Dentre as teorias que são capazes de modelar de alguma forma tal classe de problemas, a mecânica do dano contínuo é a maisrecente. Entretanto, um dos gargalos que ainda persistem é quando nas simulações numéricas a estrutura passa a apresentar o fenômenode localização de deformações, com consequente dependência dos resultados sobre a malha empregada. Para sanar este problema diversosmétodos ditos de regularização foram desenvolvidos. Todavia, apesar de eficazes, estes métodos podem inserir um grau de complexidadesignificativo nas abordagens numéricas. Neste trabalho propõe-se uma metodologia simplificada para análise estrutural não linear de pórticose arcos por meio da localização prévia dos fenômenos inelásticos em rótulas, posicionadas nas extremidades dos elementos finitos de barra earco. Desta forma é possível contornar a dependência de malha e reproduzir de forma satisfatória problemas reais, como mostram os exemplos de estruturas de concreto armado reunidos no fim deste artigo.

A semi-spring and semi-edge combined contact model in CDEM and its application to analysis of Jiweishan landslide

Continuum-based discrete element method (CDEM) is an explicit numerical method used for simulation of progressive failure of geological body. To improve the efficiency of contact detection and simplify the calculation steps for contact forces, semi-spring and semi-edge are introduced in calculation. Semi-spring is derived from block vertex, and formed by indenting the block vertex into each face (24 semi-springs for a hexahedral element). The formation process of semi-edge is the same as that of semi-spring (24 semi-edges for a hexahedral element). Based on the semi-springs and semi-edges, a new type of combined contact model is presented. According to this model, six contact types could be reduced to two, i.e. the semi-spring target face contact and semi-edge target edge contact. By the combined model, the contact force could be calculated directly (the information of contact type is not necessary), and the failure judgment could be executed in a straightforward way (each semi-spring and semi-edge own their characteristic areas). The algorithm has been successfully programmed in C++ program. Some simple numerical cases are presented to show the validity and accuracy of this model. Finally, the failure mode, sliding distance and critical friction angle of Jiweishan landslide are studied with the combined model.

A three-dimensional progressive failure model for laminated composite plates subjected to transverse loading

A novel, three-dimensional computational model is presented for the simulation of progressive failure in laminated composites subjected to out-of-plane loading conditions. Solid-like shell elements are used to model the thin plies of the laminate. In order to model mesh independent matrix cracking, a discontinuous solid-like shell element (DSLS) is utilized. A partition of unity approach is exploited to incorporate the discontinuity in the shell mid-surface, shell director and internal stretching field. A shell interface model is presented for the modeling of delamination damage. The model allows for the computationally efficient simulation of delamination and the evaluation of a consistently linearized tangent stiffness matrix for large deformation problems, which is essential for convergence. To model the coupled response of matrix cracking and delamination under large deformations, a computational framework is developed. The combined modeling of matrix cracking and delamination is achieved without incorporation of additional degrees of freedom. Numerical results are presented to show the performance and several distinct features of the model to simulate progressive failure in laminated composite shell structures.

Computational modeling of complex failure mechanisms in laminates

A computational framework for the simulation of progressive failure in composite laminates is presented. The phantom-node method (a variation to the XFEM) is used for a mesh-independent representation of matrix cracks as straight discontinuities in the displacement field. Furthermore, interface elements are used for delamination and a continuum damage model for fiber failure. The framework is validated against experimental observations for open-hole tests and compact tension tests. It is shown that different failure mechanisms are captured well, which allows for the prediction of size effects.

Progressive Failure Simulation of Security Cable Barriers

Perimeter security cable barriers are widely used by various agencies all over the world to defeat threat vehicle penetration. New barrier designs require crash test validation prior to implementation. Full-scale vehicular crash tests are costly, whereas designs via finite element simulations are time consuming and require specialized skills. Based on full-scale crash tests, an innovative and simple algorithm has been developed to model the progressive failure of security cable barriers. A multi-body approach based on the first principles of physics was developed to substantially reduce computer runtime. The solution algorithm uses a large number of small time steps. Nonlinear vehicle and cable forces and deformations are calculated based on compatibility conditions. This methodology has been validated against three full-scale crash tests. This cable barrier model, displaying simulation results graphically in a time series, provides realistic response parameters of a security cable barrier design in less than 10 minutes of runtime with reasonable accuracy.

Fire resistance simulation of loaded deck sandwich panel and deck-bulkhead assembly structures

In this study, fire resistance of a deck sandwich panel and deck-bulkhead assembly structures subject to service mechanical loads and to the action of fire is considered. The deck panel mid-span deflection was chosen as a criterion for the fire resistance assessment of both structures. Two simulation approaches were employed to determine the deck panel mid-span deflections. In the first approach, the GENOA progressive failure analysis software was used to evaluate the damage in the structure based on the equivalent temperature load profile predicted by thermal analysis. In the second approach, coupled thermal–progressive failure simulation was performed on the structure where the progressive failure analysis was invoked immediately after the temperature redistribution had been calculated for each time interval. In both approaches, the effect of fire on the bottom part of the deck panel was simulated through the application of surface heat fluxes to the bottom of the panel to calculate the equivalent temperature load required for the progressive failure analysis. The calculated mid-span deflection of the simply supported deck sandwich panel, after one-hour exposure to fire, correlated well with the experiment performed at Clemson University. Both the simulation and experimental results show that the mid-span deflection was significantly below the 2-ft deflection limit. In addition, the initiation and propagation of damage and fracture patterns over the deck structures were computed.

Progressive failure and post-buckling response of tapered composite plates under uni-axial compression

Abstract The objective of the present work is to predict the first-ply failure load, the ultimate failure load, the buckling load, the associated maximum transverse displacements, and locations and modes of failure of tapered laminated plates under the action of uni-axial compression. A non-linear finite element formulation is developed based on the first-order shear deformation theory and the geometric non-linearity in the von Karman sense. The tensor polynomial form of the maximum stress criterion is used in conjunction with a progressive failure simulation methodology. A parametric study on tapered composite plates is conducted, considering the influences of different laminate configurations, taper configurations and fiber orientation angles.

Numerical Simulation of Progressive Failure in Cut Slope of Soft Rock Using a Soil-Water Coupled Finite Element Analysis

In the present paper, based onan elastoplastic model with strain hardening and strain softening, a soil-water coupled finite element analysis is conducted to investigate the progressive failure of a cut slope in a model ground. In order to verify the validity of the analyses related to the strain-softening behavior, numerical analyses are firstly conducted for plane-strain compression in different meshes and loading steps under complete drained condition. It is confirmed by the analyses that the analysis conducted in this paper has a small dependency on the mesh size. Then, the mechanical behaviours of a cut slope, such as the change of excessive pore-water pressure, the redistribution of stress in ground due to strain softening, the propagation of shear band and the progressive failure are discussed in detail by the soil-water coupled finite element analysis. It is found that a soil-water coupled analysis based on an elastoplastic model can describe the time dependent behavior of soft rock in boundary-value problems. It is also found that a soil-water coupled analysis based on a strain-softening model can simulate the progressive failure of a cut slope.

Numerical simulation of progressive rock failure and associated seismicity

In this paper, a numerical approach to modeling progressive failure leading to collapse in rock and associated seismicity is reported. In the first part, a newly developed numerical code, RFPAZ° (Rock Failure Process Analysis), is introduced. The program allows modeling of the observed evolution of damage and associated seismic events due to progressive failure leading to collapse in brittle rock. There are three features distinguishing the approach from conventional numerical methods such as FEM: (1) by introducing heterogeneity of rock parameters into the model, RFPAZ° can simulate non-linear behavior in rock using a linear method, (2) by introducing elastic modulus reduction for failed elements, RFPA2D can process discontinuum mechanics problems by a continuum mechanics method; and (3) by recording the event-rate of failed elements, the seismicities associated with the progressive failure in rock can be simulated. In the second part of the paper, the applications of RFPA2D in simulating geological process and in solving mining design problems are illustrated. Numerical simulation of a fault initiation process indicates that some of the important phenomena, such as coalescence of microfracture, the nucleation and growth of crack clusters, fault initiation and development, elastic rebound, dilatation, uplift and seismic behavior, etc. can be simulated with this numerical code. The simulation of progressive failure leading to collapse in underground openings demonstrates the capacity of this code in solving mining design problems.

ADINA applied toward simulation of progressive failure in underground mine structures

The U.S. Bureau of Mines (USBM) conducts research to develop simple and practical computer-based tools to assist mine planners in assessing the structural stability of underground mine structures. One area of research is focusing on developing a numerical procedure that will anticipate rock mass behaviour surrounding underground mine openings prior to and during actual mining. This paper briefly overviews our experience with existing ADINA material models, presents an example of how two-dimensional boundary-element models are coupled with two-dimensional finite-element models to simulate an approximate three-dimensional situation, and demonstrates the use of a simplified progressive failure procedure. Outputs from plan-view, linear-elastic, boundary-element models executed at different mining stages are used as input to detailed, section-view, finite-element ADINA models to estimate to what degree and extent the immediate roof and floor strata and the coal pillar ribs surrounding an excavated area will weaken or fail for a given set of mining parameters. Using a pseudo-elastic approach, elastic rock mass properties are continually updated as different zones are predicted to fail. The procedure is relatively easy to use and is being designed to work interactively with the user. Inputs include parameters easily obtained from the field and rock mechanics laboratories. Specialized preprocessing and postprocessing PC-based graphics software tailored specifically to mine geometries has been developed and is described. Examples of computer-generated output from sample models representing typical mining situations are presented and results discussed.

A comparison between two optimization methods on the stacking sequence of fiber-reinforced composite laminate

This article is dealing with the study of optimization for the stacking sequence of composite laminates by two optimization methods of simplex and interior penalty. In the simplex method, both the applicable domain of magnifying factors (MFs) and the differences of stacking sequence optimization between symmetrical and unsymmetrical laminate composites are studied. When the values of MFs are 50, 70, 85, the converging of optimization process is faster and its result is more accurate. The strength of the unsymmetrical laminate with fewer layers is larger than that of the symmetric one by 8% only. But when the layers are increased, the strength of symmetric laminate is higher. In the interior penalty method, the error value can be kept within 5–6%, while in the simplex method the more layers the larger the error value. To sum up, proved by progressive failure simulation of finite element analysis, the best strength of composite laminate with optimal stacking sequence can be obtained.

Simulation of progressive failure in hanging-wall and footwall for mining with sub-level caving : U.K. Singh, O.J. Stephansson & A. Herdocia, Transactions — Institution of Mining & Metallurgy, Section A, 102(Sept–Dec), 1993, pp A188–A194

Simulation of progressive failure in hanging-wall and footwall for mining with sub-level caving : U.K. Singh, O.J. Stephansson & A. Herdocia, Transactions — Institution of Mining & Metallurgy, Section A, 102(Sept–Dec), 1993, pp A188–A194

Progressive failure simulation model for brittle rock : Lundquist, R G; Heins, R W Proc 21st US Symposium on Rock Mechanics, Rolla, Missouri, 28–30 May 1980, P591–595

Progressive failure simulation model for brittle rock : Lundquist, R G; Heins, R W Proc 21st US Symposium on Rock Mechanics, Rolla, Missouri, 28–30 May 1980, P591–595

岩盤の2次元逐次崩壊解析の試み

岩盤の2次元逐次崩壊解析の試み