Explicit Finite Element Analysis Research Articles

An effective finite element modeling approach for prediction of the behaviour of a jute fibre-reinforced composite tube under axial impact

The focus of the work reported here is on the prediction of the behaviour of a hollow cylindrical jute– polyester composite tube under axial impact using the explicit finite element analysis code, LS-DYNA. An efficient finite element modelling approach using a single shell element through the thickness of a thin-walled structural part has been chosen. Effective orthotropic material properties of a laminate which can be determined through standard ASTM tests have been used as input data for a popular constitutive model titled ‘Enhanced Composite Damage’ with the option of specifying either the Chang–Chang criteria or the Tsai–Wu criterion for failure. A unique feature of the current approach is to verify the modeling procedure initially for coupon-level tensile, compressive and flexural tests through a numerical design of experiments involving a set of physically meaningful fibre and matrix failure strain parameters, and then extend the same toward successfully predicting the mechanical behaviour of a jute composite tube subject to axial drop-weight impact. Theoretical predictions of peak responses for flexural and tube impact tests are also presented.

Numerical study of top-and seat-angle with double web-angle connection with high-strength steel

Past experimental research on top-and seat-angle with double web-angle connection (TSACW) was limited by the rate and magnitude of actuator displacement and hence results did not give information on failure mode and ultimate capacities of connection. Furthermore, extensive literature review on TSACW revealed the need for developing an accurate finite element approach to represent the characteristics of the moment-rotation behavior. Therefore, this study examined the influence of connection parameters on flexural resistance, stiffness, rotation, ductility and failure modes obtained for such joints. Explicit Finite element (FE) analyses of connection models were carried out by using ABAQUS/CAE to explore the effect of material properties of bolts and angles on moment-rotation (M-ϕ) characteristics of TSACW under monotonic loading. Applicability of six currently available M-ϕ functions was assessed by comparing them with those obtained from FE analyses. In most cases, the ultimate flexural resistance of TSACW was increased whilst its rotational capacity was decreased with the use of A572 or A514 angles with less pronounced effect on the initial stiffness. The connection failure was controlled via large deformations achieved by the top angle. Among the six selected M-ϕ functions, Richard-Abbott model was found suitable for fitting the normalized moment-rotation curves for TSACW joints.

Determination of the Impact Damage Threshold Point of Composite Material Using Fuzzy-Base Taguchi Method

In this study, the impact damage threshold point of the composite material was determined using the optimum design parameters obtained from Fuzzy Based Taguchi Method (FBTM). It is known that both Taguchi and Fuzzy methods provide optimization of design parameters yet, in Taguchi method, optimization of design parameters is not sufficient in order to solve multi response optimization problem. Therefore, Fuzzy Logic system was combined with the Taguchi system for working out the multi response optimization problem. In this study, the low velocity impact damage analyses were implemented in a LS-DYNA 3D explicit finite element program. ASTM D7136/D7136M standard was considered during the low velocity impact analyses. In explicit finite element analyses, contact algorithms were executed to observe better damage zone shapes. Furthermore, the control parameters (termination and computation time step) were tuned to provide perfect correlation with the force-energy-time histories. Eventually, it was seen that Fuzzy Based Taguchi Method (FBTM) is much more capable of optimizing the design parameters that predict the impact damage threshold point of the composite material.

Experimental and Numerical Study on Crashworthiness Parameters of Mild Steel Square Tube under Quasi-Static Axial Compression

In the present research, an experimental and numerical study on the crush response of square tube is presented. The explicit Finite Element Analysis (FEA) in LS-DYNA software is carried out to simulate crash behaviour under the quasi-static test conditions. Compression load is applied quasi-statically in an experimental study on the square tube specimens using Universal Testing Machine (UTM). In quasi-static test the bottom platen speed used is 1 mm/min. From experimental testing symmetric collapse mode is observed in all deformed specimens. The development of the symmetric collapse mode in a Finite Element (FE) model is also observed. Thus fold formation and crush response predicted by FE analysis are observed to be in very good correlation with the results obtained from experimental testing. Furthermore, the effect of the thickness of tube on crashworthiness parameters is investigated. From the FE analysis, it is found that the thickness of the square tube influences significantly the crashworthiness parameters.

Crashworthiness optimization of hierarchical hexagonal honeycombs under out-of-plane impact

This paper presents a numerical study of regular and hierarchical honeycomb structures subjected to out-of-plane impact loading. The specific energy absorption capacity of honeycomb structures via nonlinear explicit finite element analysis is investigated. The constructed finite element models are validated using experimental data available in the literature. The honeycomb structures are optimized by using a surrogate-based optimization approach to achieve maximum specific energy absorption capacity. Three surrogate models polynomial response surface approximations, radial basis functions, and Kriging models are used; Kriging models are found to be the most accurate. The optimum specific energy absorption value obtained for hierarchical honeycomb structures is found to be 148% greater than that of regular honeycomb structures.

Bionic design of thin-walled structure based on the geometry of the vascular bundles of bamboo

Several bamboo features are responsible for its known mechanical performance and thus were applied on bionic thin-walled structures, still the particular geometry of individual vascular bundles remains unexplored mechanically. This research investigates the mechanical influence of that region in the design of thin-walled structures, comparing it with bamboo-inspired designs from the literature. X-ray microtomography was used to explore bamboo bundle's geometry, applying it as reinforcement. The proposed new design showed improvements in strength and energy absorption in axial, lateral, and flexural explicit Finite Element Analyses. The vascular bundle's geometry was revealed as an important characteristic of bamboo performance.

Finite-element modelling of NiTi shape-memory wires for morphing aerofoils

AbstractThis paper presents the development and implementation of a user-defined material (UMAT) model for NiTi Shape-Memory Alloy (SMA) wires for use in LS-DYNA commercial explicit finite-element analysis software. The UMAT focusses on the Shape-Memory Effect (SME), which could be used for actuation of aerostructural components. The actuation of a fundamental structure consisting of an SMA wire connected in series with a linear spring was studied first. The SMA thermomechanical behaviour obtained from the finite-element simulation was compared with that obtained from the analytical solution in MATLAB. A further comparison is presented for an SMA-actuated cantilever beam, showing excellent agreement in terms of the SMA stress and strain as well as the tip deflection of the cantilever beam. A mesh sensitivity study on the SMA wire indicated that one beam element was adequate to accurately predict the SMA thermomechanical behaviour. An analysis of several key parameters showed that, to achieve a high recovery strain, the stiffness of the actuated structure should be minimised while the cross-sectional area of the SMA wire should be maximised. The actuation of an SMA wire under a constant stress/load was also analysed. The SMA material model was finally applied to the design of morphing aluminium and composite aerofoils consisting of corrugated sections, resulting in the prediction of reasonably large trailing-edge deflections (7.8–65.9 mm).

Mesoscale modelling of extended bearing failure in tension-absorber joints

ABSTRACT This paper presents the development and validation of a mesoscale composites damage model for predicting the energy absorption capability of “tension-absorber” joints. Tension-absorber joints are composite bolted joints specially designed to absorb energy in a crash via “extended bearing failure”, which involves the bolt forcing its way through the composite over a long distance. They have been proposed for use in future narrow-body composite fuselages. Here, extended bearing failure tests on a carbon fibre/epoxy laminate, are simulated using explicit three-dimensional finite element analysis. A physically based damage model is implemented in a user-defined subroutine. The model uses in-situ ply strengths, stress-based fibre failure criteria, Puck's criteria for matrix damage, a nonlinear law for in-plane shear, a cohesive zone model for delamination, a crack band model to mitigate mesh sensitivity, and frictional contact between the pin and the laminate, and between adjacent plies once they delaminate. The model is found to accurately predict the global response, in terms of bearing strength, mean crush stress and energy absorption, and comparison with CT scans shows that it also captures the mesoscale damage very well. The model is used to predict the effects of pin diameter, laminate thickness and stacking sequence, and the results show excellent agreement with experimental findings.

Explicit finite element analysis can predict the mechanical response of conical implant press-fit in homogenized trabecular bone

Prediction of primary stability is a major challenge in the surgical planning of dental and orthopedic implants. Computational methods become attractive to estimate primary stability from clinical CT images, but implicit finite element analysis of implant press-fit faces convergence issues due to contact and highly distorted elements. This study aims to develop and validate an explicit finite element method to simulate the insertion and primary stability of a rigid implant in a deformable bone while accounting for damage occurring at the bone-implant interface. Accordingly, a press-fit experiment of a conical implant into predrilled bovine trabecular bone was designed and realized for six samples. A displacement-driven cyclic protocol was used to quantify the reaction force and stiffness of the bone-implant system. Homogenized finite element analyses of the experiments were performed by modeling contact with friction and converting an existing constitutive model with elasto-plasticity and damage of bone tissue to be applicable to an explicit time integration scheme where highly distorted elements get deleted. The computed reaction forces and unloading stiffnesses showed high correlations (R2 = 0.95 and R2 = 0.94) with the experiment. Friction between bone and implant exhibited a strong influence on both reaction force and stiffness. In conclusion, the developed explicit finite element approach with frictional contact and element deletion accounts properly for bone damage during press-fit and will help optimizing dental or orthopedic implant design towards maximal primary stability.

사용자-서브루틴과 양해법 유한 요소 해석을 이용한 선박의 유빙 저항 추정

사용자-서브루틴과 양해법 유한 요소 해석을 이용한 선박의 유빙 저항 추정

Study on the strength of converted school pick-up truck’s roof in case of rollover accidents

In 2015, it has been reported that road traffic fatality rate in Thailand ranks number 2 in the world at 36.2 per 100,000 with an annual estimate of 66 deaths every day. Based on the survey of the Road Safety Group Thailand in 2017, at least one student got injury by school transport each day. A recent survey also revealed that the number of private hire pick-up trucks as school buses in Thailand, especially in upcountry areas, is increasing due to its lower cost in comparison to that of a van or a minibus. To get the optimal capacity as vans or minibuses, pick-up trucks’ roofs were converted for the highest passenger number at the lowest cost. Therefore, to focus on the strength of converted pick-up truck’s roof is required to help reduce losses in terms of both human injury and inside cabin’s damage due to rollover accidents. This article demonstrates an approach to design the vehicle’s roof as a superstructure of school pick-up truck based on design inputs, including structural strength, capability of local motor vehicle mechanics, nature of drivers, and nature of passengers. Explicit dynamic finite element analysis is applied to simulate the investigation on full-scale prototype according to American Federal Motor Vehicle Safety Standard No 220 standard. To validate the numerical analysis results, the roof crush test of full-scale roof prototype is performed. The analysis results showed the accurate prediction on the strength and the corresponding deformations of the full-scale prototype. These findings provide means of evaluating the strength of vehicle’s roof, which can be further applied as a guideline for national regulation. This study is planned to bring this tried prototype: the superstructure of school pick-up truck’s roof, to use in a commercial scale.

Thermodynamic behavior of NiTi shape memory alloy against low-velocity impact: experiment and simulation

The study of thermodynamic behavior of shape memory alloy (SMA) against impact is of great importance for the use of SMA as damping devices. This paper investigates the thermodynamic behavior of NiTi SMA sheet subjected to low-velocity impact loading, by means of experiment and explicit finite element (FE) analysis. First, the impact tests are carried out with different impact energies on the drop-weight impact system, the thermal response during the impact process is captured by the infrared camera. The impact force and the temperature rise achieve the maximum values of 8716 N and 46.93 ∘C at impact energy of 25 J. Then, an explicit Euler integration scheme is introduced to implement the SMA model (Wang et al., 2017, IJP) into finite element software ABAQUS by means of the explicit user-defined material subroutine VUMAT. Finally, the impact tests are simulated using the proposed numerical algorithm. Numerical results show good correlation with the experimental data, the maximum deviations between both for the impact force and the temperature are 5.78% and 0.63%, respectively. The analysis approach captures the prime thermodynamic features of SMA against low-velocity impact load such as superelastic deformation, stress-induced martensite phase transformation and temperature variation.

Application In Communication Equipments Antiseismic Time History Analysis Based on Advanced Mass Scaling

RADIOSS is a powerful and stable explicit non-linear finite element analysis (FEA) solver in Altair HyperWorks. In this paper, the seismic time history analysis of communication equipment based on RADIOSS solver was taken as the research object. In the numerical simulation, three methods were applied in the computational efficiency enhancement: the non-timestep control method, the traditional mass scaling technology, and the advanced mass scaling technology (AMS). Calculations prove that the AMS technology in RADIOSS can not only improve the solution efficiency, but also guarante the calculation accuracy in antiseismic time history analysis.

Design of process parameters for the manufacturing of wrapped connections with single solid round wires using the explicit finite element analysis

The importance of simulation has grown significantly in recent years and, in addition to its application in product and process planning, it is increasingly used in all planning and implementation phases as well as in the optimization of existing systems. The solderless wrapping process is a highly reliable electrical connection technology. A wrapped connection is a gas-tight, mechanically, and electrically durable pressure connection and often exhibits a lower probability of failure under vibration load compared to soldered connections. Appropriate material selection and correct execution of the wrapping process are prerequisites. In order to achieve these, an exact knowledge of the wire behavior and the design of the process parameters is necessary. In this paper, the wrapping process is simulated using a finite element simulation. In the first step, the relevant parameters are identified by a cause-effect analysis and then integrated into the modeling. The validation of the model is carried out by comparing geometric parameters of the connection and the resulting mechanical stresses of simulation and experiment. The model can be used to simulate a wrapped connection with an accuracy of approximately 95 %. The model is suitable for varying process parameters and investigating their influence on the quality of the connection.

Identify challenges in vibration measurements for rotating tyres using a finite element model

In the current paper, the measurements from a tyre testing on a dynamometer are replicated using a finite element analysis to identify the feasibility of obtaining mode shapes using rotating tyre data. Performing vibration analysis using computer-aided engineering (CAE) reduces the human effort of executing the complex experimental setup and performing the tests. Furthermore, it provides test engineers with an understanding of the dynamic performance of tyres. In this work, an explicit finite element analysis was performed on the rolling tyre. Using the data from the simulation, an operational modal analysis was performed to extract the modal parameters of the tyre in the rolling condition. The results are analysed with those obtained from the experimentation of the Kettering Formula SAE (FSAE) tyre.

Minimum Required Distance of Strain Gauge from Specimen for Measuring Transmitted Signal in Split Hopkinson Pressure Bar Test

The minimum required distance of the strain gauge on the transmitted bar of the split Hopkinson bar has been determined from the position of a metallic specimen via an explicit finite element analysis. The minimum required distance was determined when the strain-time profiles at r = 0, 0.5Ro and 1.0Ro, were coincident (r is the radial position and Ro is the radius of the bar.). The determined minimum required distance, f(x), is presented as a function of the relative specimen diameter to that of the bar (x = D/D0): j(x) = - 0.9385.x3 + 0.6624.x2 - 0.7459.x + 1.4478 (0.1 ≤ x ≤ 0.9). This result demonstrates the Saint-Venant's principle of rapid dissipation of localized stress in transient loading. The result will be useful for the design/modification of the pseudo-one-dimensional impact instruments that utilise a stress pulse transmitted through the specimen. The result will also allow one to avoid unnecessarily remote strain gage position from the specimen.

A finite element analysis-based study on the dynamic wheel–rail contact behaviour caused by wheel polygonization

In this study, an explicit finite element analysis method was adopted to investigate the wheel–rail impact response generated by wheel polygonization, using a three-dimensional wheel–rail rolling contact finite element model. In this model, the infrastructure below the rails and the stiffness and damping of the sleeper supports were considered. Then, the characteristics of the wheel–rail contact zone, the stress/strain state and the wheel–rail impact force of the polygonal wheel–rail system were presented and discussed and were compared with those of the ideally perfect wheel–rail system. A parametrical study was then carried out to examine the influences of train speed and the polygonal order of the wheel on the wheel–rail impact response. The finite element analysis results revealed that the vertical wheel–rail impact force induced by wheel polygonization is related to the wheel radial deviation; the maximum contact force, stress and strain are all elevated with the increase of the order of the polygonal wheel, which suggested that the wheel should be repaired when it is in the initial lower order polygonal state. These findings can provide some theoretical and technical support for the optimal design of the wheel–rail system and the safe operation of high-speed trains.

Avoiding failures during building construction using structural fuses as load limiters on temporary shoring structures

The risk of structural failure of buildings can be significant during construction. Temporary adjustable telescopic steel shores or props are commonly used in building construction. The failure of shores is sudden and therefore structural fuses as load limiters (LL) can be introduced to provide ductility in the temporary member for a specified limit failure load. Previous work by the authors showed that the design of shoring systems can be improved using LL for standard cases of imposed loads applied during construction. This paper extends this work to cases of accidental loading where the shoring system-permanent structure interaction is less known. The main principles of LLs are discussed and implemented in advanced numerical simulations of a real case RC building during construction by means of explicit nonlinear dynamic finite element analyses. Different local failure scenarios were investigated corresponding to cases observed in practice. The comparison of the numerical results obtained with and without LLs demonstrated for the first time the benefits of using LLs in terms of: (a) mitigating the risk of failure of the temporary structure; and (b) reducing permanent damage (cracking and short-term deflections in the slab) affecting the durability and functionality of the building.

Elasto-Plastic Finite Element Modeling of Short Carbon Fiber Reinforced 3D Printed Acrylonitrile Butadiene Styrene Composites

This research extends the existing classical lamination theory based finite element (FE) models to predict elasto-plastic and bimodular behavior of 3D printed composites with orthotropic material properties. Short carbon fiber reinforced acrylonitrile butadiene styrene was selected as the 3D printing material. Material characterization of a 3D printed unidirectional laminate was carried out using mechanical tests. A bimodular material model was implemented using explicit FE analysis to predict the tension and bending behavior of a 3D printed laminate. The results of the FE model predictions were experimentally validated. Hill’s yield function was effective at predicting the elasto-plastic stress–strain behavior of the laminate in tension. In bending, bimodular material behavior along with Hill’s yield function worked reasonably well in predicting the elasto-plastic bending of the laminate. The material model proposed can be used to predict the mechanical behavior of 3D printed parts with complex geometry under complex loading and boundary conditions.

On lateral compression of circular aluminum, CFRP and GFRP tubes

Thin-walled structures made of lightweight materials, e.g. aluminum, fiber reinforced composites, have been increasingly used as energy absorption structures in vehicles. This work aimed to characterize the lateral crushing behaviors of circular aluminum, glass fiber reinforced plastics (GFRP) and carbon fiber reinforced plastics (CFRP) tubes with different geometric configuration such as diameter-to-thickness (D/T) ratio or thickness. In the experimental investigation, four different D/T ratios varied from 10.78 to 48.02 were considered here for the aluminum, GFRP and CFRP tubes. Crushing behaviors such as force-displacement curves, deformation histories, and crushing force were quantified. The experimental results revealed that the load carrying capacities, energy absorption (EA) and specific energy absorption (SEA) of the circular tubes decline with increasing D/T ratio. It was found that better crashworthy characteristics of thicker composites, with a smaller D/T ratio, were due to the more favorable failure modes occurring throughout lateral compression. The lateral crashworthy performance of the GFRP tubes was marginally better than that of the CFRP counterparts. Due to ductile behavior of aluminum tubes and brittle behavior of composites, aluminum tubes showed much better lateral crashworthiness than that of the composite counterparts. Moreover, with the increase in the D/T ratio, aluminum tubes exhibited greater advantage on crashworthiness than the composite tubes. On the basis of the experimental data, explicit finite element analysis was further carried out for modeling the lateral crushing behavior of aluminum, GFRP and CFRP tubes. The numerical results were in good agreement with the experimental data, demonstrating the validity of these finite element (FE) models in predicting lateral crushing responses of aluminum, GFRP and CFRP tubes. The proposed FE models can be exploited to further study similar thin-walled metal and composite structures for design optimization.