Maximum Strain Failure Criterion Research Articles

On Nonlinear First Ply Failure Study of Laminated Composite Thin Skewed Hypar Shell Roofs

The skewed hypar shells have gained immense popularity in practical civil engineering fields due their highly aesthetic look. Light weight laminated composite material has increased its wide acceptance day by day in practical structures by virtue of superior material properties like high strength, high stiffness to weight ratio, prolonged fatigue life etc. Different types of bending as well as free and force vibration studies of laminated composite skewed hypar shells were done by earlier researchers. In some literatures, the first ply failure was also investigated using geometric linear strains only. So, the present paper aims to study the first ply failure behaviour of laminated composite skewed hypar shell roofs considering geometric nonlinearity. An eight noded isoparametric curved finite element having five degrees of freedom at each node is used here for finite element method. To establish the correctness of the present approach different benchmark problems are solved in this paper. Various types of lamina stacking sequences are taken up by the authors’ problems for first ply failure analysis of symmetric and antisymmetric skewed hypar thin shells with practical boundary condition. Along with the maximum stress and maximum strain failure criteria the authors use interactive failure criteria like Hoffman, Tsai-Hill and Tsai-Wu criteria as well as failure mode based criteria like Hashin and Puck criteria for the present study. The results obtained from this numerical investigation are analysed and post processed from different engineering standpoints to extract meaningful conclusions regarding first ply failure behaviour of the composite skewed hypar thin shells and to arrive at important practical guidelines which are expected to be beneficial for practicing civil engineers.

Evaluasi Perilaku Lentur Balok Tinggi LVL Sengon dengan Pengekang Lateral pada kedua Tumpuan

Slender beams (beams having a large section height to width ratio ( )) are commonly used in a structure that needs a large bending moment capacity. However, the use of slender beams in a structure is susceptible to overturning and torsion occurrence. Therefore, lateral bracing is usually placed in several points of the beam to prevent lateral-torsional buckling. In this study, a three-point bending test was conducted to evaluate the capacity of 250 mm x 50 mm x 2500 mm Laminated Veneer Lumber (LVL) beams made from Sengon. Two lateral supports were placed at both ends to prevent the beam's lateral displacement. The bending test result shows that the ultimate load of the LVL beam reach 27.88 kN before failure. Furthermore, the LVL beams' bending capacity was calculated using the mechanical properties provided by several previous studies. The LVL beam's capacity was predicted using manual calculation (based on SNI 7973: 2013) and numerical analysis. Numerical analysis was performed using ABAQUS software, and the results were evaluated using the Tsai-Hill and maximum strain failure criterion. The results showed that the maximum strain criterion provides a better prediction of the LVL beam's capacity than Tsai-Hill failure criterion.

Progressive Fatigue Failure Analysis of a Filament Wound Ring Specimen with a Hole

A progressive FEA mechanical fatigue degradation model for composites was developed and implemented using a UMAT user material subroutine in Abaqus. Numerical results were compared to experimental strain field data from high frequency digital image correlation (DIC) of split disk fatigue testing of pressure vessel cut outs with holes. The model correctly predicted the onset and evolution of damage in the matrix as well as the onset of fiber failure. The model uses progressive failure analysis based on the maximum strain failure criterion, the cycle jump method, and Miner’s sum damage accumulation rule. A parameter study on matrix properties was needed to capture the scatter in strain fields observed experimentally by DIC. S-N curve for the matrix material had to be lowered by 0% to 60% to capture the experimental scatter. The onset of local fiber failure had to be described by local S-N curves measured by DIC having 2.5 times greater strain than that of S-N curves found from standard coupon testing.

A study of residual burst strength of composite over wrapped pressure vessel due to low velocity impact

The aim of this research was to study the residual burst strength, dynamic structural response, and failure mechanism of composite overwrapped pressure vessel (COPV) subjected to low velocity impact by numerically and experimentally. A three-dimensional composite pressure vessel model was developed using Wound composite module (WCM) plugin of Abaqus. The impact response of composite pressure vessels was calculated based on the Hashin progressive damage criteria. The residual burst strength was predicted using maximum strain failure criteria. The COPV was impact tested and the residual burst strength was calculated. The predicted and testing results were compared, and a good correlation was found.

Constitutive Behavior and Mechanical Failure of Internal Configuration in Prismatic Lithium-Ion Batteries under Mechanical Loading

Internal short circuits and thermal runaway in lithium-ion batteries (LIBs) are mainly caused by deformation-induced failures in their internal components. Understanding the mechanisms of mechanical failure in the internal materials is of much importance for the design of LIB pack safety. In this work, the constitutive behaviors and deformation-induced failures of these component materials were tested and simulated. The stress-strain constitutive models of the anode/cathode and the separator under uniaxial tensile and compressive loads were proposed, and maximum tensile strain failure criteria were used to simulate the failure behaviors on these materials under the biaxial indentations. In order to understand the deformation failure mechanisms of ultrathin and multilayer materials within the prismatic cell, a mesoscale layer element model (LEM) with a separator-cathode-separator-anode structure was constructed. The deformation failure of LEM under spherical punches of different sizes was analyzed in detail, and the results were experimentally verified. Furthermore, the n-layer LEM stacked structure numerical model was constructed to calculate the progressive failure mechanisms of cathodes and anodes under punches. The results of test and simulation show the fracture failure of the cathodes under local indentation will trigger the failure of adjacent layers successively, and the internal short circuits are ultimately caused by separator failure owing to fractures and slips in the electrodes. The results improve the understanding of the failure behavior of the component materials in prismatic lithium-ion batteries, and provide some safety suggestions for the battery structure design in the future.

An elastoplastic axisymmetric borehole problem using a deformation theory of gradient plasticity

ABSTRACT A deformation theory of gradient plasticity is employed to study elastoplastic axisymmetric boreholes subjected to far-field biaxial tension. The gradient dependence is introduced in the constitutive framework by assuming that the flow stress (i.e., an effective stress measure) depends not only on an effective strain measure but also on the Laplacian thereof. The classical theory of linear elasticity is adopted for the elastic deformations while strain softening is assumed for the plastic part, where an equivalent work hypothesis is used to associate the stress state to the final total strain. Representative stress distributions are illustrated and compared in the context of size effects, which originate from the presence of the gradient term in the governing equations. The influence of the borehole radius on the initiation of plastic deformation, the nominal stress-strain response and the evolution of the elastoplastic interface are examined. Moreover, a maximum principal strain failure criterion is employed to discuss size effects on the onset of macroscopic fracture. The obtained results show that narrower boreholes have higher plastic and failure strength.

The Maximum Stress Failure Criterion and the Maximum Strain Failure Criterion: Their Unification and Rationalization

The maximum strain failure criterion is unified with the maximum stress failure criterion, after exploring the implications of two considerations responsible for this: (1) the failure strains for the direct strain components employed in the maximum strain criterion are all defined under uniaxial stress states, not uniaxial strain states, and (2) the contributions to the strain in a direction as a result of the Poisson effect do not contribute to the failure of the material in that direction. Incorporating these considerations into the maximum strain criterion, the maximum stress criterion is reproduced. For 3D stress/strain state applications primarily, the unified maximum stress/strain criterion is then subjected to further rationalization in the context of transversely isotropic materials by eliminating the treatments that undermine the objectivity of the failure criterion. The criterion is then applied based on the maximum and minimum direct stresses, the maximum transverse shear stress and the maximum longitudinal shear stress as the invariants of the stress state, instead of the conventional stress components directly.

Design and development of a filament wound composite overwrapped pressure vessel

A detailed design optimization of a composite over wrapped pressure vessel (COPV) is performed through finite element analysis (FEA) and testing. The design optimization of a type IV polymer-lined composite overwrapped pressure vessel is performed by means of the finite element method using ABAQUS software. A plug-in named WCM in ABAQUS is used that automates the entire process of constructing a COPV FEA model. This work investigates the influence of winding angle, number of layers, and sequence of layers on the burst strength of COPV. Maximum stress, maximum strain, Tsai Hill, Tsai Wu and Hashin progressive failure criteria are used to find the burst strength of the COPV. Comparing all the results obtained using above the failure criteria, it is found that the maximum strain criterion is more conservative, and the Hashin criterion is the least conservative. Digital Image Correlation (DIC) was utilized during burst testing to quantify the failure strain in different directions. The numerical results were compared with the experimental burst testing results and a reasonably good comparison was found.

Bird Strike Analysis on 19 Passenger Aircraft Windshield with Different Thickness and Impact Velocity

Abstrct - A Windshield is a component that must be tested to comply with the certification requirements in the bird strike phenomenon based on Civil Aviation Safety Regulations (CASR) subpart 23.775. The purpose of this study is to obtain the thickness of 19 passenger aircraft windshield that meets the certification requirements and determine the dynamic response of the windshield to impact velocity variations. The finite element is used to simulate bird strike phenomena. The elastic-plastic polymethyl methacrylate (PMMA) material with the maximum principal strain failure criterion is used to model the dynamic response of the windshield. Numerical modeling is validated, both with analytical and experimental results which are then used to investigate the effect of variations in windshield thickness and impact velocity. The results obtained that with a thickness of 9 mm, the windshield is able to withstand bird strikes based on cases that have been determined by the regulation. In addition, the impact velocity that causes the dynamic response of the windshield in the elastic, plastic deformation, and the greatest failure is the velocity of 87.5 ms-1(cruising phase). The uppermost of the windshield (fixed) is the weakest part due to the stress concentration.

A novel failure criterion based upon forming limit curve for thermoplastic composites

This study aims to explore failure mechanism and failure criteria of carbon fiber reinforced polypropylene (CFRPP) by presenting a novel notch-shaped design of specimens with two different fiber orientations (0/90)4 and (+45/-45)4 subject to stamping process under room temperature. Two forming limit curves/diagrams (FLCs/FLDs) were established based upon the minor strain and major strain, as well as the developed equivalent fiber strain combined with a ratio of minor to major strain (SR), respectively. A novel notch-shaped design enables to minimize the influence of fiber orientation on failure modes and FLC of CFRPP effectively. Not only did the equivalent fiber strain based FLC reflect the failure mode in terms of a certain SR value, but also showed the failure strain on fiber bundles quantitatively. Finite element (FE) models involving the new failure criteria (FLC) were developed on the basis of the experimental results. It was found that such a new FE model is able to better predict the results than those with the conventional maximum strain or maximum stress failure criteria. The difference in failure behaviors among these three failure criteria (i.e. FLC, maximum strain and maximum stress) was compared. The history of failure evolution and potential damage status of typical specimens were further analyzed through the FE model. The results indicated that the new FLC failure criteria can be used for the failure assessment in CFRPP structures. This study is anticipated to provide a guideline for further investigation into failure mechanism and failure criteria of thermoplastic composites under different service conditions.

Study of constituent effect on the failure response of fiber reinforced composites to impact loading with the material point method

It is still not clear how the constituent properties and arrangements in fiber reinforced composites (FRC) could affect the impact response involving failure evolution quantitatively. Recent reports on mesoscopic modeling via the material point method (MPM) for textile-based FRC have demonstrated that the macroscopic residual velocity as obtained with the model-based simulation matches very well with available experimental data for projectile impact/penetration problems, even if all the FRC constituents are modeled as linear elastic with the maximum tensile strain failure criterion. A quantitative investigation via the MPM is therefore performed to explore the effect of constituent modeling and configuration on the textile-based FRC response to impact. It is found that the orientation of mesoscopic structure with given fiber geometry and property in FRC, instead of the matrix material, governs the impact response. The matrix material failure could be either brittle or ductile with a trivial effect on the impact response.

Simulated lesions representative of metastatic disease predict proximal femur failure strength more accurately than idealized lesions

Metastatic disease in bone is characterized by highly amorphous and variable lesion geometry, with increased fracture risk. Assumptions of idealized lesion geometry made in previous finite element (FE) studies of metastatic disease in the proximal femur may not sufficiently capture effects of local stress/strain concentrations on predicted failure strength. The goal of this study was to develop and validate a FE failure model of the proximal femur incorporating artificial defects representative of physiologic metastatic disease. Data from 11 cadaveric femur specimens were randomly divided into either a training set (n = 5) or a test set (n = 6). Clinically representative artificial defects were created, and the femurs were loaded to failure under offset torsion. Voxel-based FE models replicating the experimental setup were created from the training set pre-fracture computed tomography data. Failure loads from the linear model with maximum principal strain failure criterion correlated best with the experimental data (R2 = 0.86, p = 0.024). The developed model was found to be reliable when applied to the test dataset with a relatively low RMSE of 46.9 N, mean absolute percent error of 12.7 ± 17.1%, and cross-validation R2 = 0.88 (p < 0.001). Models simulating realistic lesion geometry explained an additional 26% of the variance in experimental failure load compared to idealized lesion models (R2 = 0.62, p = 0.062). Our validated automated FE model representative of physiologic metastatic disease may improve clinical fracture risk prediction and facilitate research studies of fracture risk during functional activities and with treatment interventions.

Lognormal Distribution Function for Describing Seepage Damage Process of Single‐Cracked Rock

The precondition of rock stress and deformation analysis is a reasonable rock constitutive model. Most of the previous studies have described the heterogeneous microdamage by Weibull distribution or normal distribution. However, both of them have limitations. Therefore, this paper intends to use the lognormal distribution as the probability distribution model of rock microunit strength. Based on the tensile failure of the single‐fractured rock under the hydrodynamic force, the maximum tensile strain failure criterion is used as the distribution parameter of rock microunit strength. And, considering the multiphase properties of the filling fractured rock, the equivalent elastic modulus parameter is adopted in the model. We design a triaxial seepage test for the filled single‐fractured rock and analyze the applicability and rationality of the modified lognormal statistical damage model for characterizing the fractured rock by using the test data. According to the comparison of the experimental stress‐strain curve and the model stress‐strain curve and the analysis of the damage value test curve and the model curve, the rationality of the established statistical damage constitutive model is verified, and the advantages and limitations of the model are proposed.

An experimental and numerical investigation on low-velocity impact damage and compression-after-impact behavior of composite laminates

This study investigated the damage and failure mechanism of composite laminates under low-velocity impact and compression-after-impact (CAI) loading conditions by numerical and experimental methods. Ultrasonic C-scan, DIC and SEM methods were combined to give a new and deep insight of damage evolution and failure mechanisms in composite laminates. A novel three-dimensional damage model based on continuum damage mechanics was developed to investigate the impact and CAI behavior with consideration of both interlaminar delamination damage and intralaminar damage. The maximum-strain failure criterion and an improved three-dimensional Puck criterion, which was physically-based, were employed to capture the initiation of fiber and matrix damage respectively and a bi-linear damage constitutive relation was used for characterization of damage evolution. The interlaminar delamination damage was simulated by the interfacial cohesive behavior. Good correlation between numerical and experimental results demonstrated the effectiveness and rationality of the proposed numerical model. The effects of impact energy level and multiple impacts were discussed.

Failure pressure of medium and high strength pipelines with scratched dent defects

Abstract It is very important in engineering design and integrity assessment of pipeline to accurately predict its failure pressure, especially for the pipeline with mechanical damages. This paper numerically investigates the failure pressure of medium and high strength pipelines with scratched dent which is on the outer surface of the pipe. Pipe materials of two different grades are chosen in the analysis which represent medium and high strength steel, respectively. Failure pressure of an intact pipeline with fixed ends is derived analytically. On the basis of the maximum plastic strain failure criterion put forward by previous scholars, failure pressure of finite element models containing dent and scratch defects is determined. Parametric studies are carried out to obtain the influencing rule of the dimensions of dent and scratch. The effects of scratch length and depth on failure pressure with various dent depths are obtained. Finally, a formula is fitted for predicting the failure pressure of pipelines with scratched dents on the basis of finite element results. Compared to burst test data from literature, the proposed formula is proved to be reasonable.

Influence of multiaxial loading on the failure of Kevlar KM2 single fiber

The role of multiaxial loading on the failure of Kevlar® KM2 ballistic fibers during transverse loading is not well understood. Quasi-static experiments reported by Hudspeth M, Li D, Spatola J, et al. (2015) on single KM2 fiber subjected to transverse loading by three indenter geometries over a wide range of loading angles exhibit significant reductions in the average axial tensile failure strain. In this study, a three-dimensional finite element model is developed to predict the degree of multiaxial loading present at the location of fiber failure in these experiments. The model predicts an axial tensile strain concentration within the indenter–fiber contact zone. The fiber is also subjected to multiaxial stress/strain states within the contact zone consisting of axial tension, axial compression, transverse compression and interlaminar shear that can degrade axial tensile failure strain. For a round indenter with a radius much higher than the fiber diameter, the axial tensile strain concentration and multiaxial strain in the fiber are negligible. In the case of a fragment-simulating projectile and a razor indenter, significant axial tensile strain concentrations (2.2–5.9) are predicted and the localized transverse loading results in extensive inelastic deformation within the fiber cross-section. Based on the results, a maximum axial tensile strain failure criterion incorporating the multiaxial loading degradation effects is developed. The failure criterion correlates well with the experimental measurements reported by Hudspeth et al. for all three indenters. Modeling the experiments provides new insights into the tensile failure strain of high-performance ballistic fibers at extremely small gage lengths subject to transverse impact loading.

Finite-Element and Residual Stress Analysis of Self-Pierce Riveting in Dissimilar Metal Sheets

The residual stress profile in dissimilar metal sheets joined by a self-piercing rivet is simulated and compared to experimental measurements. Simulation of joining aluminum alloy 6111-T4 and steel HSLA340 sheets by self-piercing riveting (SPR) is performed using a two-dimensional axisymmetric model with an internal state variable (ISV) plasticity material model. Strain rate and temperature dependent deformation of the base materials is described by the ISV material model and calibrated with experimental data. Using the LS-DYNA simulation package, an element erosion technique is adopted in an explicit analysis of the separation of the upper sheet with maximum shear strain failure criterion. An explicit analysis with dynamic relaxation technique was then used for springback and cooling down analysis following the riveting simulation. The residual stress profile of SPR experimental joint with same configuration is characterized using neutron diffraction, and good agreement was found between the simulation and residual stress measurements.

Predicting the Buckling Behavior of Pultruded Beams Under Axial Static Compression

Buckling behavior of U-section glass/polyester pultruded beams subjected to axial static compression was investigated. Numerical model of the problem was implemented in the finite element code with a dynamic explicit analysis. Experimental tests were performed to validate numerical model. Maximum stress, maximum strain, Hashin, Hou and the combination of maximum strain and Hou failure criteria (maximum strain and Hou criteria are used for fiber and matrix failure, respectively) were compared in predicting the behavior of the beams in axial compression. Results showed that the maximum stress and the Hashin criteria predicted force–displacement curve, buckling mode and damage mode shapes correctly, while the model without failure criteria could not predict the behavior of the beam properly.

Optimum design of the carbon composite bipolar plate (BP) for the open cathode of an air breathing PEMFC

The proton exchange membrane fuel cells (PEMFCs) are a promising source of portable power due to its high energy density, low emissions and wide power range. However, PEMFCs have some limitations for portable applications because of the supplementary power consumption and the mass increase by balance of plants, such as the fuel pump, air compressor and humidifier.In this study, a light mass PEMFC system was developed using carbon composite bipolar plates (BPs) and an air breathing stack design with open cathode channel configurations to reduce the mass of the stack. However, under the high compaction pressure, the failure occurred in the carbon composite BPs for the open cathode.To enhance the durability of the BP against the compaction pressure, the finite element analysis, the compressive test and the fracture toughness test were performed. The maximum compaction pressure on the BP was calculated by applying the maximum strain failure criterion to the composite BP. Then, the optimum thickness and stacking sequence of the open cathode bipolar plate were determined by considering the mass and the maximum compaction pressure.

Establishing a new Forming Limit Curve for a flax fibre reinforced polypropylene composite through stretch forming experiments

In developing an understanding of the failure in natural fibre reinforced polymer composites, the failure limits of this class of the material system are required. It is found that the conventional Forming Limit Curve is not suitable to predict the failure initiated in the natural fibre composite as principal strains cannot differentiate the strain on the flax fibres and the polypropylene matrix. This study proposes a new Forming Limit Curve for the composite which expresses limiting fibre strain as a function of forming mode depicted by the ratio of minor strain to major strain. The new Forming Limit Curve, along with the Maximum Strain failure criterion have been successfully implemented in FEA simulations, and numerical simulations suggest that the former is more accurate. The current work provides an innovative method to predict the onset of failure in natural fibre composites, which can be applied in composite forming and structural design.