Strain-based Failure Criterion Research Articles

Short-term behavior of glass fiber-polymer composite bending-active elastica beam under service load application

Bending-active elastica beam is a structural configuration that is based on the elastic deformation of an initially straight beam. This deformation occurs when horizontal displacements are applied to a sliding support, causing the beam to bend into an arched shape. Previous research has focused on the stability of small-scale bending-active structures, thus not considering material strength, which is crucial in real-scale applications and structural design. This paper investigates the short-term structural behavior of bending-active elastica beams using pultruded glass fiber-polymer composite profiles, as used in real-scale structures. A series of short-term bending and service load application experiments were performed considering different bending degrees and loading scenarios. These results were used to validate finite element modeling. They demonstrated that steeper bent beams experience material failure, while shallower ones exhibit snap-through buckling. Material failure initiates on the tensile side of the beams, with cracks initiating at locations of maximum curvature. Higher bending degrees and symmetric loading result in higher maximum loads than lower bending degrees and asymmetric loading. A strain-based failure criterion, which can serve for structural design, is derived.

Comprehensive integrity assessment of spent nuclear fuel cladding during normal and postulated conditions of transportation

As a part of Spent Nuclear Fuel (SNF) management, it is important to maintain the cladding integrity to prevent the potential release of hazardous radioactive materials. Accordingly, assessing the integrity of SNF under the generated shock and vibration loads during normal conditions is essential for safe transportation. In this study, failure criteria for two zirconium alloys were derived by utilizing data from tensile property tests, mechanical model calculations, and machine learning estimations. Integrity assessment under normal and postulated transportation conditions was also performed via finite element analyses. Loading conditions were generated by real time-acceleration data collected during transportation tests in the Republic of Korea. Shock and vibration loads were applied to a simplified light-water reactor assembly. Furthermore, postulated transportation conditions and pre-cracked cladding were assumed for more challenging conditions. Consequently, a comprehensive integrity assessment of SNF cladding under shock and vibration loads for both free-defect and defective (pre-cracked) cladding was conducted. In each case, the resultant maximum principal strains, stress intensity amplitudes, and stress intensity factors were significantly smaller than the strain-based failure criteria, S-N curve, and fracture toughness, respectively. Therefore, the integrity of SNF cladding under transportation conditions remained intact even when assuming further challenging postulated transportation load conditions.

Patient-specific finite element analysis for assessing hip fracture risk in aging populations

The femur is one of the most important bone in the human body, as it supports the body’s weight and helps with movement. The aging global population presents a significant challenge, leading to an increasing demand for artificial joints, particularly in knee and hip replacements, which are among the most prevalent surgical procedures worldwide. This study focuses on hip fractures, a common consequence of osteoporotic fractures in the elderly population. To accurately predict individual bone properties and assess fracture risk, patient-specific finite element models (FEM) were developed using CT data from healthy male individuals. The study employed ANSYS 2023 R2 software to estimate fracture loads under simulated single stance loading conditions, considering strain-based failure criteria. The FEM bone models underwent meticulous reconstruction, incorporating geometrical and mechanical properties crucial for fracture risk assessment. Results revealed an underestimation of the ultimate bearing capacity of bones, indicating potential fractures even during routine activities. The study explored variations in bone density, failure loads, and density/load ratios among different specimens, emphasizing the complexity of bone strength determination. Discussion of findings highlighted discrepancies between simulation results and previous studies, suggesting the need for optimization in modelling approaches. The strain-based yield criterion proved accurate in predicting fracture initiation but required adjustments for better load predictions. The study underscores the importance of refining density-elasticity relationships, investigating boundary conditions, and optimizing models through in vitro testing for enhanced clinical applicability in assessing hip fracture risk. In conclusion, this research contributes valuable insights into developing patient-specific FEM bone models for clinical hip fracture risk assessment, emphasizing the need for further refinement and optimization for accurate predictions and enhanced clinical utility.

Progressive fatigue damage modeling of laminated composites using strain-based failure criteria

The progressive fatigue damage (PFD) model is a well-known approach for simulating the fatigue behavior of laminated composites. In the PFD model, stress-based failure criteria detect failure modes in a unidirectional (UD) ply of laminated composites. Using stress-based failure criteria requires performing numerous UD ply characterization tests. The present research presents a series of strain-based failure criteria for the unidirectional ply under fatigue loading conditions. Using the current criteria, the need for strength degradation tests was eliminated, and the number of characterization tests was reduced drastically. Using a user-defined material behavior (UMAT) subroutine code, stress-based failure criteria were replaced by the present strain-based failure criteria in the PFD model. To evaluate the results of the model, a comprehensive experimental program was conducted to characterize the mechanical properties of UD ply and laminated composites (with/without hole) under static and fatigue loading conditions. Moreover, the PFD model was also evaluated by the available experimental data of pin-loaded composites under fatigue-loading conditions. Compared to the stress-based criteria, the present criteria improved the accuracy of the predicted fatigue life by up to 63% and reduced the cost of testing by about 50%.

Modelling of Fatigue Delamination Growth and Prediction of Residual Tensile Strength of Thermoplastic Coupons.

Thermoplastic composites are continuously replacing thermosetting composites in lightweight structures. However, the accomplished work on the fatigue behavior of thermoplastics is quite limited. In the present work, we propose a numerical modeling approach for simulating fatigue delamination growth and predicting the residual tensile strength of quasi-isotropic TC 1225 LM PAEK thermoplastic coupons. The approach was supported and validated by tension and fatigue (non-interrupted and interrupted) tests. Fatigue delamination growth was simulated using a mixed-mode fatigue crack growth model, which was based on the cohesive zone modeling method. Quasi-static tension analyses on pristine and fatigued coupons were performed using a progressive damage model. These analyses were implemented using a set of Hashin-type strain-based failure criteria and a damage mechanics-based material property degradation module. Utilizing the fatigue model, we accurately foretold the expansion of delamination concerning the cycle count across all interfaces. The results agree well with C-scan images taken on fatigued coupons during interruptions of fatigue tests. An unequal and unsymmetric delamination growth was predicted due to the quasi-isotropic layup. Moreover, the combined models capture the decrease in the residual tensile strength of the coupons. During the quasi-static tension analysis of the fatigued coupons, we observed that the primary driving failure mechanisms were the rapid spread of existing delamination and the consequential severe matrix cracking.

Energy-based approach to study liquefaction triggering in homogeneous and stratified soils under consolidated undrained cyclic loading

Pore water pressure development through seismic effect is one of the key reasons for liquefaction failures in the foundations, dams, bridges, slopes and other vulnerable geotechnical engineering structures. The energy dissipation theories have provided a remarkable understanding of the pore water pressure generation inside a soil skeleton. In the present study, a series of consolidated undrained cyclic triaxial tests have been performed to evaluate the normalized dissipated energy (Wn) required for triggering liquefaction in both homogeneous and stratified soil specimens (prepared using silt interlayer) to replicate the site conditions nearby marine or alluvial deposits. The generated hysteresis loops using cyclic loading facilitate the calculation of dissipated energy. Also, the test results indicated a significant variation in the dissipated energy of homogeneous specimens at different magnitudes of cyclic stress ratios (CSR) and relative densities (Dr). With an increase in the cyclic stress ratio from 0.14 to 0.20, the trend of dissipated energy was observed to be different when relative densitie of sand varied from 30% to 65%. In the stratified specimens, thickness (t) and location of the silt layer (d) in the given soil specimen were the major influencing factors for estimating the liquefaction potential in loose conditions. Additionally, the highest value of Wn,max was obtained as 0.51 for the stratified specimen with topt = 28 mm at a cyclic stress ratio of 0.14. Based on the trendline variations, empirical models have been developed to estimate the normalized dissipated energy (Wn) for both homogeneous and stratified conditions. The developed models for homogeneous specimens are functions of CSR and Dr, whereas, in the case of stratified specimens, t, d and σd/σ'c (σd = deviator stress, σ'c = effective confining stress) have been utilized to predict the Wn with an satisfactory R2 value above 0.90. From the analysis of liquefaction resistance curves, the energy-based approach used in this study has been observed to provide more realistic results than the pore pressure ratio and strain-based failure criteria.

Prediction of the Time to Failure of Boiler Tubes Flawed With Localized Erosion

AbstractA failure mechanism prevalent with boiler tubes operating in harsh environmental conditions is localized erosion. The consequence of the erosion mechanism is a substantial reduction of the tube thickness, ultimately leading to plastic collapse and consequently rupturing of the tubes. Locating and repairing all the affected tubes within the boiler are time consuming and expensive. It will be worthwhile to rank all the identified flaws so that critical flaws that cannot survive till the next scheduled shutdown are prioritized for repair. Consequently, nonlinear structural analysis was conducted on various boiler tubes that failed by localized erosion. The tubes had a wide range of localized erosion flaws that required a detailed assessment technique. The failure was evaluated numerically using various stress and strain-based failure criteria as well as performing the American Petroleum Institute and the American Society of Mechanical Engineers (API-ASME) fitness-for-service (FFS) assessment on the tubes. A projected time to failure (Pt) for each tube based on the various criteria used in this study was determined. This enabled the ranking of the flawed tubes based on the priority of their repair. The outcome of this study demonstrates the potential for a tool which will enable industry users to prioritize the replacement or repair of critically flawed tubes and avert replacing tubes that are still safe for future operation.

Mechanical Properties of Prismatic Li-Ion Batteries—Electrodes, Cells, and Stacks

Abstract Mechanical abusive loadings, as an inevitable consequence of road accidents, can damage the embedded energy storage system in an electric vehicle and deform its constitutive parts, e.g., the lithium-ion batteries. Therefore, to study the mechanical responses of these batteries and avoid expensive testing equipment and rigorous safety percussions, researchers are propelled toward utilizing numerical models. Computationally cost-efficient homogenized finite element models that represent the whole battery in the form of a uniform medium are the most feasible solution, especially in large-scale battery stacks simulations. Compared to the other form factors of the batteries, prismatic cells have been understudied even though they have higher packaging efficiency, by making optimal use of space. In this article, a comprehensive homogenization and failure calibration method was developed for these prismatic cells. The homogenization was done through extensive uniaxial components tests of the jellyroll and the shell casing. In addition, biaxial tensile tests and simulations were used to calibrate strain-based failure criteria for the components. The calibrated homogenized model is validated in various punch loading scenarios and used in the characterization of the load–displacement responses and failure modes of the stacked cell configurations. In the stacked simulations, due to the cushion-like behavior of the other cells, the failure happens in higher values of displacement compared to a single cell. However, the normalized intrusion percentages for the battery stacks are lower compared to a single battery cell. This emphasizes the importance of the safety assessment of an electric vehicle based on the failure analysis of the battery stacks rather than a single cell. This goal would be feasible through simulations of only homogenized cell models in the stacked configurations, which are elaborated in this article for prismatic cells.

An improved bond-based peridynamic model with shear bonds for eliminating rigid body rotation

Peridynamics (PD) is a kind of nonlocal theory based on displacement calculation of material particles around a horizon. The calculation of bond force, which determines the distribution of displacement field, is the key to damage and fracture simulation. Due to introduction of tangential stiffness, the bond-based PD models with shear bonds (PDS models), put forward higher requirements for the calculation of bond force. Because PDS models cannot remove the false shear deformation of bonds caused by rigid body rotation, the calculation of bond force may be inaccurate. To eliminate the influence of rigid body rotation on the calculation of bond force, an improved PDS model is proposed. Based on the principle of minimum energy and the nonlocality of peridynamics, the formula of rigid body rotation is derived. By deducting the influence of rigid body rotation, the improved PDS model ensures the accuracy of bond force calculation. In addition, a new failure criterion, strain-based failure criterion, is developed to improve the accuracy of PD model in calculating fracture energy. The results of deformation and fracture examples with finite rigid body rotation illustrate the necessity of removing the effects of rigid body rotation, and prove that the improved PDS model has high precision in the calculation of elastic displacement and prediction of cracking process. Finally, verification of the developed strain-based failure criterion was tackled with dynamic crack examples.

A computational insight on damage-based constitutive modelling in femur mechanics

The present paper addresses femur failure mechanics, by numerically investigating the influence of brittle/ quasi-brittle bone constitutive description when combined with several failure criteria and different descriptions of bone ultimate parameters. Starting from computed tomography images of an experimentally-tested cadaveric femur, the bone geometry has been reconstructed through a semi-automatic segmentation procedure, and patient-specific material properties have been derived. Loading-induced loss of structural integrity has been simulated through a progressive thermodynamically-based damage model, by introducing different strain- and stress-based damage evolution laws. An in-house displacement-driven incremental approach has been implemented in a finite element framework to mimic the in-vitro experimental procedure. An energy-based regularization technique allowed to obtain results which are mesh independent and therefore physically meaningful. Depending on the adopted modelling strategy, significant differences in terms of yield and failure load, as well as in fracture patterns, have been numerically experienced. Comparisons between the proposed numerical results and the available experimental outcomes have been carried out. For the femur model herein analysed, an elastic quasi-brittle bone description combined with strain-based failure criteria seems to be more effective in predicting the mechanical behaviour up to the fracture. Presented mesh-independent results therefore contribute to justify the need of damage-based approaches for predicting in an effective way failure mechanisms of femurs.

The Influence of Selected Strain-Based Failure Criteria on Ship Structure Damage Resulting from a Collision with an Offshore Wind Turbine Monopile

Abstract Offshore wind farms are developing well all over the world, providing green energy from renewable sources. The evaluation of possible consequences of a collision involves Finite Element computer simulations. The goal of this paper was to analyse the influence of selected strain-based failure criteria on ship damage resulting from a collision with an offshore wind turbine monopile. The case of a collision between an offshore supply vessel and a monopile-type support structure was examined. The results imply that simulation assumptions, especially the failure criteria, are very important. It was found that, using the strain failure criteria according to the minimum values required by the design rules, can lead to an underestimation of the ship damage by as much as 6 times, for the length of the hull plate, and 9 times, for the area of the ship hull opening. Instead, the adjusted formula should be used, taking into account both the FE element size and the shell thickness. The influence of the non-linear representation of the stress-strain curve was also pointed out. Moreover, a significant influence of the selected steel grade on collision damages was found.

A combined fugacity and multi-axial ductility damage approach in predicting high temperature hydrogen attack in a reactor inlet nozzle

High temperature hydrogen attack (HTHA) and creep damage and cracking are time-dependent phenomena which can occur at relatively low temperatures (300–500 °C) in low alloy steel components used in petroleum refinery and petrochemical plant. The present study combines a novel multiaxial ductility creep model with a sub-grain level fugacity partial pressure strain-based failure criterion due to a build-up of methane gas to predict progressive damage accumulation and HTTA degradation in an aging nozzle component. Finite element (FE) simulations using appropriate subroutines for the coupled approach allow progressive failure predictions combining HTHA and creep deformation in a C-0.5Mo steel inlet nozzle which had seen 80,000 h operation. A sensitivity study has been carried out to quantify the effects of different operating temperatures, failure strains, hydrogen concentration and pressure and material hydrogen diffusivity on the levels of damage in the nozzle over its lifetime. The predictions accurately bound the measured damage observed in the nozzle component and highlight the sensitivity of the model with respect to the input variables.

Modeling of damage behavior of carbon fiber reinforced plastic composites interference bolting with sleeve

Interference-fit is getting increasing attentions in the aerospace field owing to its excellent enhancement on the sealing and fatigue life of composites assembly, but the severe damage around the hole caused by installation is still a huge challenge. In this paper, a three-dimensional anisotropic non-linear progressive damage model based on continuum damage mechanics was developed to reveal the damage mechanism of carbon fiber reinforced plastic (CFRP) composites interference bolting with sleeve. The proposed model adopted strain-based failure criteria and non-linear damage evolution law to predict damage initiation and propagation of composite laminates. A cohesive model taking into account the traction-separation constitutive response was employed to capture the delamination behavior between the composite plies. The elastoplastic model was utilized to characterize the sleeve's deformation behavior. Numerical simulations of different installation modes are performed and compared with experiments. The inserting load, damage modes and damage positions predicted by the proposed model agree well with the experimental results. Moreover, it is also verified that the interference installation of sleeved fasteners can remarkably reduce the intra-laminar damage and avoid the inter-laminar delamination of composite laminates compared to the conventional bolt.

Mechanical Characterisation and modelling of the rolling process of potato-based dough

Motivated by social, economic and health factors, food product manufacturers are increasingly attracted towards the incorporation of potato into snack foods. However, the lack of gluten degrades the mechanical properties of potato dough, posing a challenge in ensuring optimal manufacturing processes. An important process of industrial dough production is the sheeting or rolling process. This study developed a computational design tool to ensure smooth sheeting processes for potato doughs. A visco-hyperelastic constitutive model was calibrated using uniaxial compression data, providing the required material parameters for the rolling simulation. The model output was validated through tests on a laboratory small-scale instrumented rolling rig, where the roller speed and roll gap were varied to determine the effect on the rolling force and sheet exit thickness. A good agreement between the experimental and numerical results for the roll force and sheet exit thickness was found for smaller reduction ratios. At larger reductions, the numerical rolling force and exit thickness values were higher than the experimental values, and this was attributed to the dough being damaged while being fed through small roll gaps. A critical tensile strain-based failure criterion was proven to be accurate in predicting conditions for sheet tearing. The combination of the newly developed numerical model and tensile strain failure criterion can serve as a simple and powerful design tool for predicting the roll forces, the rolled sheet height as well as the process conditions which may lead to damage in the potato dough. As a result, interruptions in the continuous sheeting process associated with sheet damage or tearing may be avoided. Since the present study focuses on rolling parameters in a laboratory scale setup, future work will provide greater insight in scaling up the results to industrial rolling processes.

A new failure criterion for determining the cyclic resistance of low-plasticity fine-grained tailings

Reasonable determination of the cyclic resistance of low-plasticity fine-grained tailings is important for the engineering design of new tailings dams. In this paper, a series of monotonic and cyclic triaxial undrained tests were conducted to investigate the mechanical response of low-plasticity fine-grained tailings (Taiping tailings). A unified Viscous Energy Dissipation Ratio (VEDR) was then used to develop an energy-based method to study the failure mode under cyclic loading. The VEDR is a normalized energy ratio based on the relationship between cyclic stress and strain. Collapse failure was observed when the dynamic properties suddenly changed beyond the peak point of VEDR (VEDRpeak). These changes included a sudden decrease in VEDR, an abrupt increase in cyclic amplitude strain (εcyc), and the prominent failure pattern of hysteresis curve. In this regard, VEDR failure criterion was proposed by considering VEDRpeak as the failure point. Comparisons based on the effective stress path and the cyclic resistance ratio (CRR) indicate that the VEDR failure criterion is more suitable for determining the CRR than conventional strain-based failure criteria for Taiping tailings. Furthermore, a relationship between the VEDR failure criterion and strain-based failure criterion was introduced. In general, the VEDR failure criterion will provide an insight into the determination of CRR for low-plasticity fine-grained tailings.

Numerical modeling of shear nonlinearity and failure analysis for composite laminates

In this paper, the shear nonlinearity and failure behavior of composite laminates were investigated with experimental and numerical method. A nonlinear shear model that includes progressive stiffness reduction and permanent shear strain was developed to characterize the nonlinear shear behavior. Strain-based failure criteria were combined with a set of stiffness degradation method to predict in-ply damage initiation and evolution of composite laminates. Delamination damage was simulated with cohesive zone model. The progressive damage model was implemented in commercial finite element software ABAQUS by a VUMAT subroutine. The capability of the proposed model was validated by predicting the tensile behavior of open-hole tensile specimen.

Image-based anatomical reconstruction and pharmaco-mediated bone remodeling model applied to a femur with subtrochanteric fracture: A subject-specific finite element study

Patient-specific finite element (FE) models are constructed in a way that boundary conditions, material and geometric FE models respect the unique characteristics of the patients, offering a more reliable and realistic structural analysis. This study presents an image-based construction process of a patient-specific FE model applied to a femur with a subtrochanteric fracture. Available procedures are systematized and described in greater depth aiming to investigate the difficulties and possibilities in the development of this type of model. A set of image processing techniques (segmentation, labeling, morphological operations and registering) were performed for volumetric reconstruction and registration of femoral fragments by assessing computed tomography (CT) images in a semi supervised procedure. The CT numbers feed the FE mesh with a non-homogeneous distribution of elasticity modulus. A FE analysis and a bone remodeling simulation with pharmacological stimulus based on the dynamics of bone cells populations were also developed for this study. The FE analysis revealed that the principal stresses provided results close to those obtained using a generic homogeneous model, with a difference of about 2%. In contrast, principal strains presented significant differences, up to 12 and 21 % for the maximum tensile and compressive principal strain values, respectively. The critical values of tensile principal strains were located in the superior part of the femoral neck, a typical region of femoral fractures, and maximum principal strains 2 and 3 (compressive) were concentrated in the diaphyseal region, rather close to the actual fracture. These results corroborate previous works indicating that the strain-based failure criterion is more successful in capturing the bone fracture sites when compared to stress-based criteria. The attempt to reconstruct the material state before the failure as implemented here constitutes an innovative way to analyze and reconstruct bone fractures. In the bone remodeling simulation, the inclusion of an antiresorptive agent stimulus produced cortical bone thickening, an increase in the BMD biomarker, and an overall increase in the bone ash density, just as expected in an osteoporosis therapeutic treatment. In conclusion, this study highlights the advantages of subject-specific FE models compared to generic ones in the study of abnormal clinical cases, evaluation of fracture risk, and optimization of surgical intervention. On the other hand, the high level of human intervention and expertise involved in patient-specific FE analyses hinders the incorporation of this technique into clinical practice.

Effects of curvature on ductile fracture initiation in curved compact tension specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides

The effects of curvature on K, J, plastic zone, near-tip stress and fracture initiation in curved compact tension (CCT) specimens of unhydrided and hydrided irradiated Zr-2.5Nb materials are determined by three-dimensional finite element analyses. Based on a strain-based failure criterion, the fracture initiation load for unhydrided CCT specimens is slightly lower than those for unhydrided compact tension (CT) and pressure tube (PT) specimens. For hydrided specimens, the reductions of fracture initiation loads for CT, CCT and PT specimens are similar. The fractions of fracture initiation loads for hydrided specimens are about 60–70% of those for unhydrided specimens.

Mechanical behavior of metastatic femurs through patient-specific computational models accounting for bone-metastasis interaction

This paper proposes a computational model based on a finite-element formulation for describing the mechanical behavior of femurs affected by metastatic lesions. A novel geometric/constitutive description is introduced by modelling healthy bone and metastases via a linearly poroelastic constitutive approach. A Gaussian-shaped graded transition of material properties between healthy and metastatic tissues is prescribed, in order to account for the bone-metastasis interaction. Loading-induced failure processes are simulated by implementing a progressive damage procedure, formulated via a quasi-static displacement-driven incremental approach, and considering both a stress- and a strain-based failure criterion. By addressing a real clinical case, left and right patient-specific femur models are geometrically reconstructed via an ad-hoc imaging procedure and embedding multiple distributions of metastatic lesions along femurs. Significant differences in fracture loads, fracture mechanisms, and damage patterns, are highlighted by comparing the proposed constitutive description with a purely elastic formulation, where the metastasis is treated as a pseudo-healthy tissue or as a void region. Proposed constitutive description allows to capture stress/strain localization mechanisms within the metastatic tissue, revealing the model capability in describing possible strain-induced mechano-biological stimuli driving onset and evolution of the lesion. The proposed approach opens towards the definition of effective computational strategies for supporting clinical decision and treatments regarding metastatic femurs, contributing also to overcome some limitations of actual standards and procedures.

Physical stochastic damage model for concrete subjected to fatigue loading

A unified damage model applicable to both monotonic and fatigue loading is developed for concrete in the framework of mesoscopic stochastic fracture models. Besides traditional strain-based failure criteria, a new kind of energy-based failure criteria for meso-elements is established relying on nanoscale mechanics. Verifications show that the proposed model can not only reasonably reproduce the randomness in fatigue lifetime but also well describe the nonlinearity in fatigue damage evolution of concrete. In addition, the physical mechanisms lying behind these randomness and nonlinearity are clearly demonstrated for the first time.