Contact Definition Research Articles

Design Modification and Finite Element Analysis of Stainless Steel 316L Locking Compression Plates for Mid-Transverse Fractures

Bone fracture is the most common orthopedics problem. To achieve stability in the internal fixation of bone fragments, apply a Locking Compression Plate (LCP), which consists of a set of plates and screws. Common materials used for the bone fixation plate are stainless steel, titanium, and other metal alloys. Those materials are stiffer than cortical bone, causing a stress shielding effect. The stress shielding phenomenon takes place during bone remodelling, which affects the growth of bone and bone loss upon the healing process. The purpose of this study is to design the best LCP to minimize or eliminate the stress shielding issue for tibia shaft fracture. A reverse engineering process is used to obtain the solid part using 3D scanning, and data clean-up is done in CATIA V5, which is then used to be imported into the finite element software ANSYS 23R2. The fracture simulation is on transverse type fractures with the creation of a gap of 1 mm around the mid-tibial shaft region. Several boundary conditions will be parametrized, such as material properties, contact definitions, meshing, and loading conditions in preprocessing. This paper examines and simulates the behaviour of LCP under a load via finite element analysis (FEA). Design 2 was selected due to its superior stress distribution,resulting in the LCP bearing only 177.98 MPa with a total deformation of 0.57 mm

Weighted families of contact maps to characterize conformational ensembles of (highly-)flexible proteins.

Characterizing the structure of flexible proteins, particularly within the realm of intrinsic disorder, presents a formidable challenge due to their high conformational variability. Currently, their structural representation relies on (possibly large) conformational ensembles derived from a combination of experimental and computational methods. The detailed structural analysis of these ensembles is a difficult task, for which existing tools have limited effectiveness. This study proposes an innovative extension of the concept of contact maps to the ensemble framework, incorporating the intrinsic probabilistic nature of disordered proteins. Within this framework, a conformational ensemble is characterized through a weighted family of contact maps. To achieve this, conformations are first described using a refined definition of contact that appropriately accounts for the geometry of the inter-residue interactions and the sequence context. Representative structural features of the ensemble naturally emerge from the subsequent clustering of the resulting contact-based descriptors. Importantly, transiently populated structural features are readily identified within large ensembles. The performance of the method is illustrated by several use cases and compared with other existing approaches, highlighting its superiority in capturing relevant structural features of highly flexible proteins. An open-source implementation of the method is provided together with an easy-to-use Jupyter notebook, available at https://gitlab.laas.fr/moma/WARIO.

Interaction of guided Ultrasonic Waves with delaminations in Fiber Metal Laminates represented by contact definition

The main objective of the present work is to investigate the influence of delamination including contact on guided ultrasonic waves in fiber metal laminates. For this purpose, a numerical model of a fiber metal laminate consisting of layers made from steel and carbon fiber-reinforced polymer is introduced. The wave propagation is simulated in damaged and undamaged models. Afterwards, the results are compared and discussed. The considered undamaged model represents the reference model for the comparison. This model has been sufficiently investigated and validated numerically and theoretically in previous works [1]. For the damaged models, the investigation is restricted to centered and off-center placed delaminations of elliptical shape. A contact condition is applied to the boundary interfaces for each damage case. The results show that reflections, transmissions, and mode conversions occur when the wave encounters the two ends of the delamination. A closer look at the models with differently located delaminations across the thickness reveals that a particular phenomenon can be observed in the centered delamination, the trapped mode. This effect also occurs in both damaged models without and with contact definition. In these cases, the wave resulting from the mode conversion remains trapped in the delamination area and is repeatedly reflected between the corners of the delamination. In addition, the models with delaminations show a significant increase in the displacement amplitude in the delamination area compared to the rest of the laminate, probably due to the energy balance in the propagation from full to half thickness. However, the frequency analysis of the model with contact definition shows a significant influence on the frequency spectrum compared to the model without contact. 1. Mikhaylenko, A., et al., 2022, “Numerical Analysis of the Main Wave Propagation Characteristics in a Steel-CFRP Laminate Including Model Order Reduction,” Acoustics, 4(3):517–537, doi: 10.3390/acoustics4030032.

Contact framework for total Lagrangian smoothed particle hydrodynamics using an adaptive hybrid kernel scheme

AbstractTotal Lagrangian SPH (TLSPH) offers many advantages that can overcome instability and computational time issues. However, it is not naturally applicable to problems with contact. Many problems in solid dynamics and structural analysis require contact definition. In order to use the total Lagrangian formulation, further development for the contact algorithm is required. This research proposes an algorithm to implement inter‐particle contact in TLSPH using an adaptive hybrid‐kernel scheme for the first time. A combination of the updated and total Lagrangian formulations at the contact surface is introduced, in which the kernel type change automatically when particles from a different body are detected. In kernel change from the updated to the total Lagrangian formulation, the gradient correction cannot be performed using a common correction method because different frames of reference are used. Therefore, a hybrid‐kernel correction technique is proposed to maintain the zeroth‐ and first‐order completeness. Then, the contact force is obtained from the inter‐particle force using the conservation of momentum. The proposed method does not require a user‐defined parameter that makes the application straightforward. Based on the test, the proposed method agrees well with the data available in published literature and the finite element method. Compared with the contact method in classical SPH, the proposed TLSPH shows a significant stability improvement.

Biomechanical conditions of subtalar joint arthrodesis with calcaneal locking nail: A probabilistic numerical study.

Subtalar joint arthrodesis is primarily indicated for advanced osteoarthritis, hindfoot deformity, and/or instability. During the first 6-10 weeks after surgery, there is an intermediary structurally weaker state before complete bony fusion of the calcaneus and talus occurs. Loading of the foot can lead to mechanical stresses and relative movements in the former joint gap, which can impede the fusion process. The objective of this study was to examine the mechanical healing conditions for a subtalar arthrodesis with a calcaneal locking nail. A probabilistic finite element model of the subtalar joint with a calcaneal locking nail was created to represent the foot post-surgery that accounts for the uncertainty of the material properties. The model differentiates between cortical and cancellous bone and includes non-linear contact definitions in the subtalar joint. Multiple loading scenarios, including hindfoot inversion/eversion, were simulated to determine bone and implant stresses. Utilizing local articular coordinate systems, a displacement analysis was established to separate normal and tangential components and account for their separate effects. The loading of the locking nail was assessed through section moments. Under inversion/eversion loading, the area near the locking screws and upper end of the nail experienced the highest stresses. The maximum stresses in cortical and cancellous bone were 112±8.3 MPa and 2.1±0.2 MPa, respectively. The comparison of the von Mises and maximum principal stresses for the bones showed a load case dependency with strong effect on tensile loading states. The proposed method for the analysis of relative displacement in the local articular coordinate systems showed joint regions exhibiting normal and tangential movements that changed with the considered loading states. It was found that tangential displacements of up to 0.19 mm are related to the torsional loading of the calcaneal locking nail, which is connected to the corresponding torsional stiffness of the implant and its fixation in the calcaneus and talus. Normal displacements in the joint gap of up to -0.18 mm can be shown to be governed by the bending moments acting on the calcaneal locking nail, which are linked to the nail's bending stiffness. The ratio of tangential and normal displacement in the critical inversion configuration was determined to be -1.1. Inversion and eversion loads can lead to significant mechanical loading of the bones and to bending and torsional loading of the locking nail. The bending leads to normal displacements in the articular gap. Torsions can lead to significant tangential displacements that have been shown to promote non-union instead of bony fusion.

Parameter optimization in a finite element mandibular fracture fixation model using the design of experiments approach

Only a few mandibular bone finite element (FE) models have been validated in literature, making it difficult to assess the credibility of the models. In a comparative study between FE models and biomechanical experiments using a synthetic polyamide 12 (PA12) mandible model, we investigate how material properties and boundary conditions affect the FE model's accuracy using the design of experiments approach.Multiple FE parameters, such as contact definitions and the materials' elastic and plastic deformation characteristics, were systematically analyzed for an intact mandibular model and transferred to the fracture fixation model. In a second step, the contact definitions for the titanium screw and implant (S–I), implant and PA12 mandible (I-M), and interfragmentary (IF) PA12 segments were optimized. Comparing simulated deformations (from 0 to −5 mm) and reaction forces (from 10 to 1′415 N) with experimental results showed a strong sensitivity to FE mechanical properties and contact definitions. The results suggest that using the bonded definition for the screw-implant contact of the fracture plate is ineffective. The contact friction parameter set with the highest agreement was identified: titanium screw and implant μ = 0.2, implant and PA12 mandible μ = 0.2, interfragmentary PA12 mandible μ = 0.1. The simulated reaction force (RMSE = 26.60 N) and surface displacement data (RMSE = 0.19 mm) of the FE analysis showed a strong agreement with the experimental biomechanical data. The results were generated through parameter optimization which means that our findings need to be validated in the event of a new dataset with deviating anatomy.Conclusively, the predictive capability of the FE model can be improved by FE model calibration through experimental testing. Validated preoperative quasi-static FE analysis could allow engineers and surgeons to accurately estimate how the implant's choice and placement suit the patient's biomechanical needs.

Infection rate among close contacts of patients with coronavirus disease in Japan: a descriptive study and literature review.

In Japan, on April 20, 2020, the definition of a close contact regarding coronavirus disease (COVID-19) was changed from a long-term contact time to a specified contact time of 15 min and from a contact distance of 2 m to 1 m. We aimed to determine the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rate among close contacts of patients with COVID-19 and determine the impact of the infection on transmission among close contacts. The numbers of SARS-CoV-2 tests, SARS-CoV-2-positive cases, and close contacts of patients with COVID-19 were assessed between March 2020 and February 2021 in Fukui Prefecture, Japan. The study period was subdivided into 3 periods. The second and third period contained data with the changed definition of close contact. Overall, 32,238 SARS-CoV-2 tests were performed. There were 545 patients with COVID-19 and 1487 close contacts, of whom 267 tested positive. The highest infection rate occurred in period 3. Distance, protective measures, and contact time with COVID-19 patients influenced the increased infection rate. The infection rate showed a rising trend from 11.1% in period 1 to 19.2% and 20.0% in periods 2 and 3, respectively (Cochran-Armitage test; P < 0.004). Multivariate analysis revealed that female sex was an independent risk factor for infection of close contacts (odds ratio: 2.23; 95% confidence interval: 1.700-2.930). Female sex is a risk factor for transmission by close contacts. The rate of infection among close contacts may be associated with contact time, contact distance, and protective measures.

Influence of setting-dependent contacts and protective behaviours on asymptomatic SARS-CoV-2 infection amongst members of a UK university

We survey 62 users of a university asymptomatic SARS-CoV-2 testing service on details of their activities, protective behaviours and contacts in the 7 days prior to receiving a positive or negative SARS-CoV-2 PCR test result in the period October 2020–March 2021. The resulting data set is novel in capturing very detailed social contact history linked to asymptomatic disease status during a period of significant restriction on social activities. We use this data to explore 3 questions: (i) Did participation in university activities enhance infection risk? (ii) How do contact definitions rank in their ability to explain test outcome during periods of social restrictions? (iii) Do patterns in the protective behaviours help explain discrepancies between the explanatory performance of different contact measures? We classify activities into settings and use Bayesian logistic regression to model test outcome, computing posterior model probabilities to compare the performance of models adopting different contact definitions. Associations between protective behaviours, participant characteristics and setting are explored at the level of individual activities using multiple correspondence analysis (MCA). We find that participation in air travel or non-university work activities was associated with a positive asymptomatic SARS-CoV-2 PCR test, in contrast to participation in research and teaching settings. Intriguingly, logistic regression models with binary measures of contact in a setting performed better than more traditional contact numbers or person contact hours (PCH). The MCA indicates that patterns of protective behaviours vary between setting, in a manner which may help explain the preference for any participation as a contact measure. We conclude that linked PCR testing and social contact data can in principle be used to test the utility of contact definitions, and the investigation of contact definitions in larger linked studies is warranted to ensure contact data can capture environmental and social factors influencing transmission risk.

Numerical Investigation on Protective Mechanism of Metal Cover Plate for Alumina Armor against Impact of Fragment by FE-Converting-SPH Method.

It is of extreme importance to develop a reliable numerical prediction technique to simulate the ballistic response of ceramic armor subjected to high-velocity impact (HVI) to economize the test cost and shorten the design period. In the present manuscript, a series of experiments on tungsten heavy alloy (WHA) fragment's penetration into 99.5% alumina (AD995) armors are systematically simulated by employing the FE-converting-SPH technique. The numerical results are compared with the experimental counterparts to find that the FE-converting-SPH method is fairly efficient in predicting the depth of penetration, the residual velocity, length and mass of fragment, and reproducing the crack forms of ceramic. The applicability and accuracy of the numerical model in terms of the algorithm, material model parameters and contact definitions are validated. Then, the relevant parameters of the calibrated numerical model are incorporated to explore the influence of cover-layer thickness on the armor performance. A few mechanisms regarding the cover plate have been identified to act on the armor performance, such as the alteration of fracture cone half-angle, proportion of energy absorbed by ceramic, mushrooming deformation of fragment, etc. The result of multi-mechanism superposition is that the best ballistic performance is endued with 1 mm cover-layer armor, which demonstrates a 24.6% improvement over the bi-layer armor with 4.96 g/cm2 area density, only at the cost of 15.7% increase in areal density, when back-plate thickness is held as 2 mm; for a constant area density of 4.96 g/cm2, a 1 mm cover-layer is also expected to be the best choice, with 10.7% improvement in armor performance.

Low secondary attack rate after prolonged exposure to sputum smear positive miliary tuberculosis in a neonatal unit

BackgroundSeveral neonatal intensive care units (NICU) have reported exposure to sputum smear positive tuberculosis (TB). NICE guidelines give support regarding investigation and treatment intervention, but not for contact definitions. Data regarding the reliability of any interferon gamma release assay (IGRA) in infants as a screening test for TB infection is scarce. We report an investigation and management strategy and evaluated the viability of IGRA (T-Spot) in infants and its concordance to the tuberculin skin test (TST).MethodsWe performed an outbreak investigation of incident TB infection in a NICU after prolonged exposure to sputum smear positive miliary TB by an infant’s mother. We defined individual contact definitions and interventions and assessed secondary attack rates. In addition, we evaluated the technical performance of T-Spot in infants and compared the results with the TST at baseline investigation.ResultsOverall, 72 of 90 (80%) exposed infants were investigated at baseline, in 51 (56.7%) of 54 (60%) infants, follow-up TST at the age of 6 months was performed. No infant in our cohort showed a positive TST or T-Spot at baseline. All blood samples from infants except one responded to phytohemagglutinin (PHA), which was used as a positive control of the T-Spot, demonstrating that cells are viable and react upon stimulation. 149 of 160 (93.1%) exposed health care workers (HCW) were investigated. 1 HCW was tested positive, having no other reason than this exposure for latent TB infection. 5 of 92 (5.5%) exposed primary contacts were tested positive, all coming from countries with high TB incidences. In total, 1 of 342 exposed contacts was newly diagnosed with latent TB infection. The secondary attack rate in this study including pediatric and adult contacts was 0.29%.ConclusionThis investigation highlighted the low transmission rate of sputum smear positive miliary TB in a particularly highly susceptible population as infants. Our expert definitions and interventions proved to be helpful in terms of the feasibility of a thorough outbreak investigation. Furthermore, we demonstrated concordance of T-Spot and TST. Based on our findings, we assume that T-Spot could be considered a reliable investigation tool to rule out TB infection in infants.

Investigating transmission of SARS-CoV-2 using novel face mask sampling: a protocol for an observational prospective study of index cases and their contacts in a congregate setting

IntroductionThis study aims to measure how transmission of SARS-CoV-2 occurs in communities and to identify conditions that lend to increased transmission focusing on congregate situations. We will measure SARS-CoV-2 in...

Definition of Atomic-Scale Contact: What Dominates the Atomic-Scale Friction Behaviors?

The definition of atomic-scale contact is a very ambiguous issue owing to the discrete atomic arrangement, which hinders the development of contact theory and nano-tribological techniques. In this work, we studied the atomic-scale contact area and their correlations with friction force based on three distinct contact definitions (interatomic distance, force, and interfacial chemical bonds) by performing large-scale atomistic simulations on a typical ball-on-disk contact model. In the simulations, the measured contact areas defined by interatomic distance, force, and interfacial chemical bonds (referred as to Adist, Aforce, and Abond, respectively) are not equivalent at all, while we interestingly clarify that only Adist is consistent with the one calculated by continuum Hertz contact mechanics, and moreover, only Abond is proportional to the friction force indicating that Abond is the dominant one for determining materials' frictional behaviors. The above fundamental insights into the atomic-scale contact problems are useful to deeply understand the origins of tribological phenomena and contribute to the further prediction of atomic-scale friction.

Further Development of 3D Crack Growth Simulation Program to Include Contact Loading Situations

Crack growth in structures depends on the cyclic loads applied on it, such as mechanical, thermal and contact, as well as residual stresses, etc. To provide an accurate simulation of crack growth in structures, it is of high importance to integrate all kinds of loading situations in the simulations. Adapcrack3D is a simulation program that can accurately predict the propagation of cracks in real structures. However, until now, this three-dimensional program has only considered mechanical loads and static thermal loads. Therefore, the features of Adapcrack3D have been extended by including contact loading in crack growth simulations. The numerical simulation of crack propagation with Adapcrack3D is generally carried out using FE models of structures provided by the user. For simulating models with contact loading situations, Adapcrack3D has been updated to work with FE models containing multiple parts and necessary features such as coupling and surface interactions. Because Adapcrack3D uses the submodel technique for fracture mechanical evaluations, the architecture of the submodel is also modified to simulate models with contact definitions between the crack surfaces. This paper discusses the newly implemented attribute of the program with the help of illustrative examples. The results confirm that the contact simulation in Adapcrack3D is a major step in improving the functionality of the program.

Modeling and Analysis of Low Velocity Effect (LVI) on Mixed Lamination Fibers

Composites experience corruption of primary solidness because of different kinds of effect stacking bringing about the harm which is challenging to see from the outer layer of the design. The paper manages the limited component model (FEM) to concentrate on the conceivable displaying methodology in low-speed influence (LVI) and disappointment system of carbon fiber built up polymer (CFRP) composite cover of CCF300/epoxy and its primary reactions. In limited component estimation, a proposed three-layered moderate harm model is utilized to decide the intralaminar harm, while the firm contact definition is utilized to break down the interlaminar harm. The disappointment model exhibitions are approved and checked given various limit conditions while keeping up with the effective energy. Through reenactment, the variety in limit conditions fundamentally changes the underlying reactions and energy retention of the covers. It is trusted this study will be an extraordinary device in deciding the different composite.

Analysis of Optimal RAP Content Based on Discrete Element Method

Methods of recycling a large amount of waste asphalt mixture generated in pavement maintenance and decreasing the waste of existing resources are one of the problems that will be solved in the future. In this study, the mechanical parameters of asphalt mixture containing different amounts of RAP were analyzed by discrete element method (DEM), and the reasonable RAP content was discussed in combination with uniaxial compression test results. And it is considered that the contact between different particles will produce the failure of stress transfer between particles with different modulus, and the contact definition between RAP particles and virgin aggregate particles is added to make the discrete element model more in line with the actual situation. The results indicated that the trend of discrete element analysis was consistent with that of the uniaxial penetration test, but there were differences in the specific values. Uniaxial compression test results showed that the optimum RAP content of the recycled asphalt mixture was 30%. The optimal RAP content analysis result from the DEM simulation was smaller than the laboratory test result, and the theoretical optimal RAP content was 28%. The results of this study provide a reference for the mixture design of recycled asphalt mixture.

Determinants of grandparent–grandchild digital contact in Italy

The broad definition of intergenerational contact includes not only meeting face-to-face, but also the important element of communication at a distance, such as via telephone. With the pervasion of the Internet and electronic devices, digital contact has become another increasingly important option. We examined digital contact between grandparents and grandchildren in comparison with traditional forms of contact (i.e. face-to-face and by telephone) using Italian data from the 2016 Families, Social Subjects and life cycle (FSS) survey. We found that grandparents belonging to younger cohorts, those with higher education, those who lived in urban areas and those in better health were more likely to maintain digital contact with their grandchildren. Results also show that digital contact tends to compensate for a lack of (frequent) face-to-face contact, and to cumulate with telephone contact. Our results have significant implications for the current and future development of intergenerational relationships as they suggest an increasing role of digital contact for distant geographical situations. Against the background of persisting inequalities in the access and the use of the Internet, our findings emphasise the need to improve digital network connectivity and user skills, particularly among specific sub-groups of the population.

A subject-specific FEM to predict deep tissue mechanical stresses when supine: Development of efficient contact interfaces using Shared Topology

Prior studies have demonstrated Finite Element (FE) analysis is a useful tool when analysing the complex interplay of tissue and body loads which act through the human pelvis in a subject lying supine. The computational accuracy and efficiency of FE models that contain complex non-linear geometric interfaces between different anatomical and tissue regions can be compromised by superfluous node interactions and contact penetrations. This study proposes a method for the development of efficient contact definitions using shared topology. The Shared Topology Finite Element Model (FEM) resulted in a 37% reduction in solution time compared to an equivalent FEM defined with Bonded contact. At all tissue interfaces, contact penetration occurred in the Bonded FEM, with subsequent under-prediction of peak compressive strains and stresses by 1–7% compared to the Shared Topology FEM. Simulating supine lying of a 19-year-old male, the Shared Topology FEM predicted peak compressive stress in the muscle interfacing the sacrum of 29.4 kPa, and peak compressive strain of 50%. The proposed methodology can be applied for any medical imaging derived FEM where there are multiple congruent 3D geometries with negligible sliding across interfaces.

Effectiveness evaluation of digital contact tracing for COVID-19 in New South Wales, Australia

BackgroundDigital proximity tracing apps were rolled out early in the COVID-19 pandemic in many countries to complement conventional contact tracing. Empirical evidence about their benefits for pandemic response remains scarce. We evaluated the effectiveness and usefulness of COVIDSafe, Australia's national smartphone-based proximity tracing app for COVID-19.MethodsIn this prospective study, done in New South Wales (NSW), Australia, we included all individuals in the state who were older than 12 years with confirmed, locally acquired SARS-CoV-2 infection between May 4 and Nov 4, 2020. We used data from the NSW Notifiable Conditions Information Management System, the national COVIDSafe database, and information from case interviews, including information on app usage, the number of app-suggested contacts, and the number of app-suggested contacts determined by public health staff to be actual close contacts. We calculated the positive predictive value and sensitivity of COVIDSafe, its additional contact yield, and the number of averted public exposure events. Semi-structured interviews with public health staff were done to assess the app's perceived usefulness.FindingsThere were 619 confirmed COVID-19 cases with more than 25 300 close contacts identified by conventional contact tracing during the study period. COVIDSafe was used by 137 (22%) cases and detected 205 contacts, 79 (39%) of whom met the close contact definition. Its positive predictive value was therefore 39%. 35 (15%) of the 236 close contacts who could have been expected to have been using the app during the study period were identified by the app, making its estimated sensitivity 15%. 79 (0·3%) of the estimated 25 300 contacts in NSW were app-suggested and met the close contact definition. The app detected 17 (<0·1%) additional close contacts who were not identified by conventional contact tracing. COVIDSafe generated a substantial additional perceived workload for public health staff and was not considered useful.InterpretationThe low uptake of the app among cases probably led to a reduced sensitivity estimate in our study, given that only contacts who were using the app could be detected. COVIDSafe was not sufficiently effective to make a meaningful contribution to the COVID-19 response in Australia's most populous state over a 6 month period. We provide an empirical evaluation of this digital contact tracing app that questions the potential benefits of digital contact tracing apps to the public health response to COVID-19. Effectiveness evaluations should be integrated into future implementations of proximity contact tracing systems to justify their investment.FundingNew South Wales Ministry of Health (Australia); National Health and Medical Research Council (Australia)

Automatic tool-based pre-processing of generic structural models for water impact simulations in the aircraft pre-design

The integration of automated tool capabilities for the generation of models for transient dynamic calculations in the scope of the aircraft pre-design is described in this paper. The Python-based DLR framework PANDORA, initially developed for the modelling and the sizing of aircraft structures in multidisciplinary process chains, is considered for this work. The focus lays on the generation of suitable numerical models for the water impact simulation. To enable this, the internal tool database was extended to consider additional features such as contact definitions, mesh-free formulations, enhanced connection models and specific control options. The generation of the CPACS-based FE aircraft model was extended by means of discretisation and additional structural components. The generation of the water domain was also included according to user defined inputs like pool dimensions, initial conditions and the selection of an appropriate fluid modelling approach. In addition, a feature to launch a simulation directly within the framework was included. Finally, options to retrieve and visualize results from finished water impact simulations were also integrated, allowing to display contour and time history plots.

Finite Element Modelling Approach for Progressive Crushing of Composite Tubular Absorbers in LS-DYNA: Review and Findings

Robust finite element models are utilised for their ability to predict simple to complex mechanical behaviour under certain conditions at a very low cost compared to experimental studies, as this reduces the need for physical prototypes while allowing for the optimisation of components. In this paper, various parameters in finite element techniques were reviewed to simulate the crushing behaviour of glass/epoxy tubes with different material models, mesh sizes, failure trigger mechanisms, element formulation, contact definitions, single and various numbers of shells and delamination modelling. Six different modelling approaches, namely, a single-layer approach and a multi-layer approach, were employed with 2, 3, 4, 6, and 12 shells. In experimental studies, 12 plies were used to fabricate a 3 mm wall thickness GFRP specimen, and the numerical results were compared with experimental data. This was achieved by carefully calibrating the values of certain parameters used in defining the above parameters to predict the behaviour and energy absorption response of the finite element model against initial failure peak load (stiffness) and the mean crushing force. In each case, the results were compared with each other, including experimental and computational costs. The decision was made from an engineering point of view, which means compromising accuracy for computational efficiency. The aim is to develop an FEM that can predict energy absorption capability with a higher level of accuracy, around 5% error, than the experimental studies.