Explicit Finite Element Analysis Research Articles

A numerical study on impact and compression after impact behaviour of variable angle tow laminates

Recent developments of variable angled tow (VAT) technology have indicated that variable stiffness composite laminates offer a strong potential for structural tailoring. However, the design complexity requires use of numerical analysis and novel techniques for this type of structural composites. This paper addresses the problem of the impact and compression after impact (CAI) behaviour prediction of variable stiffness composite laminates with emphasis on the effect of the interaction between fibre orientations, matrix-cracks and delaminations. An explicit finite element analysis using bilinear cohesive law-based interface elements and cohesive contacts is employed for the investigation. Examples are presented to illustrate the effectiveness of the current models for predicting the extent of impact damage and subsequent compression strength. The current study has improved the understanding of interactions between matrix-cracks and delaminations to clarify open questions on delamination initiation and how matrix cracks and fibre orientations interact.

Numerical study on crashworthiness assessment and improvement of composite carbody structures of tilting train using hybrid finite element model

This paper describes the numerical results on crashworthiness assessment and improvement scheme of tilting train made of composite materials. The bodyshell of tilting train was composed of aluminum honeycomb sandwich panels and carbon-fabric/epoxy laminate composites. The input parameters for numerical analysis were obtained from material tests. Crashworthiness analysis of the tilting train was conducted using the explicit finite element analysis code LS-DYNA3D and according to four collision scenarios of the Korean railway safety rule. The hybrid finite element modeling technique, which is made up of 2D shell and 3D solid elements for three cars in the front and 1D equivalent element for the rest cars in the rear, was introduced to ensure fast and accurate design verification for crashworthiness of railway vehicle. The numerical results showed that hybrid modeling technique was an economical approach for the analyzed results, finite element modeling, and calculating time in comparison with conventional modeling method using 2D shell and 3D solid elements for railway vehicles.

Meso-scale modelling of shock wave propagation in a SiC/Al nanocomposite reinforced with WS2-inorganic fullerene nanoparticles

It has been postulated that nanocomposites incorporating IF-WS2 nanoparticles within a strong matrix might form the next generation of highly shock-resistant materials. The present work describes initial analyses into the shock response of such materials via a sequential multi-scale dynamic analysis. Density functional theory is used to calculate the elastic properties of the multilayered WS2 nanoparticles. These properties are then used within an explicit finite element (FE) analysis of wave propagation through an embedded statistical volume element (SVE) of a two-phase nanocomposite consisting of a matrix with IF-WS2 nanoparticles. Some wave front dispersion was noted, particularly where the modulus of the matrix is significantly different from that of the particles. A three-phase nanocomposite consisting of an aluminium matrix with IF-WS2 and SiC nanoparticles was also considered, and showed more apparent wave front dispersion than for the two-phase nanocomposite. Hugoniot shock propagation data have been derived from the simulation outputs. It is concluded that sequential multiscale modelling of these systems is appropriate and can provide useful information about shock wave propagation in the elastic region. The work also provides a foundation for more realistic simulations at higher rate loading, where it will be necessary to incorporate material failure in the models.

Research and Application on Automotive Aluminum Bumper Based on Topology Optimization

Based on the explicit dynamic finite element analysis software, the use of hybrid cellular automata (HCA) as an optimization model, the collision of beams in the aluminum front structure optimization design. The 6061 aluminum alloy before the collision of beams to replace a model of the original steel beams, trolley collision simulation and experimental validation of the results show that the aluminum front impact beams than the original steel before the collision beam quality to reduce by 25% and has a higher flexural strength, low-speed collision, aluminum front impact beams than the original steel system energy absorption increased by 45.6%.

Development, Validation and Comparison of Higher Order Finite Element Approaches to Compute the Propagation of Lamb Waves Efficiently

When considering structural health monitoring (SHM) applications efficient and powerful numerical methods are required to predict the behavior of ultrasonic guided waves and to design SHM systems. The existing commercial explicit finite element analysis tools based on standard linear displacement elements quickly reach their limits when applied to ultrasonic waves in thin plates, so called Lamb waves. It is known that the required temporal and spatial resolution causes enormous computational costs. One resort to overcome this problem is the application of special finite elements utilizing higher order polynomial shape functions (p> 2). The current paper is focused on the development of such higher order finite elements and the verification of their accuracy and performance. In the paper we compare and evaluate the capabilities of spectral finite elements,p-version finite elements and isogeometric finite elements. Their advantages and disadvantages with respect to ultrasonic wave propagation problems are discussed and their properties are demonstrated by solving a benchmark problem. Higher order finite elements with varying polynomial degrees in longitudinal and transversal direction (anisotropic ansatz space) are investigated and convergence studies are performed. The results of the convergence studies are summarized and a guideline to estimate the optimal discretization is prepared. If the required accuracy is known, the proposed guideline provides a helpful means to determine both the element size and the polynomial degree template for a given model.

Study of Mechanical Deformations on Tough Skinned Vegetables during Mechanical Peeling Process (A Review)

Peeling is an essential phase of post harvesting and processing industry; however undesirable processing losses are unavoidable and always have been the main concern of food processing sector. There are three methods of peeling fruits and vegetables including mechanical, chemical and thermal, depending on the class and type of fruit. By comparison, the mechanical methods are the most preferred; mechanical peeling methods do not create any harmful effects on the tissue and they keep edible portions of produce fresh. The main disadvantage of mechanical peeling is the rate of material loss and deformations. Obviously reducing material losses and increasing the quality of the process has a direct effect on the whole efficiency of food processing industry, this needs more study on technological aspects of these operations. In order to enhance the effectiveness of food industrial practices it is essential to have a clear understanding of material properties and behaviour of tissues under industrial processes. This paper presents the scheme of research that seeks to examine tissue damage of tough skinned vegetables under mechanical peeling process by developing a novel FE model of the process using explicit dynamic finite element analysis approach. A computer model of mechanical peeling process will be developed in this study to stimulate the energy consumption and stress strain interactions of cutter and tissue. The available Finite Element softwares and methods will be applied to establish the model. Improving the knowledge of interactions and involves variables in food operation particularly in peeling process is the main objectives of the proposed study. Understanding of these interrelationships will help researchers and designer of food processing equipments to develop new and more efficient technologies. Presented work intends to review available literature and previous works has been done in this area of research and identify current gap in modelling and simulation of food processes.

Crashworthiness optimisation of vehicle structures with magnesium alloy parts

This paper explores the effects of replacing the baseline steel with lightweight magnesium alloy parts on crashworthiness characteristics and optimum design of a full-vehicle model. Full frontal, offset frontal and side crash simulations are performed on a validated 1996 Dodge Neon model using explicit nonlinear transient dynamic finite element analyses in LS-DYNA to obtain vehicle responses such as crash pulse, intrusion distance, peak acceleration and internal energy. Twenty-two parts of the vehicle body structure are converted into AZ31 magnesium alloy with adjustable wall thickness while the remaining parts are kept intact. The magnesium alloy material model follows a piecewise linear plasticity law considering separate tension and compression properties and maximum plastic strain failure criterion. Six different metamodelling techniques including optimised ensemble are developed and tuned for predictions of crash-induced responses within the design optimisation process. The crashworthiness optimisation problem is solved using the sequential quadratic programming method with most accurate surrogate models of structural responses considering both constrained single- and multi-objective formulations. The results show that under the combined crash scenarios with the selected material models and design constraints, the vehicle model with magnesium alloy parts can be optimised to maintain or improve its crashworthiness characteristics with up to 50% weight savings in the redesigned parts.

Crashworthiness optimization design of honeycomb sandwich panel based on factor screening

This paper presents a crashworthiness robust optimization design of aluminum honeycomb sandwich panel with regular hexagonal core cell based on explicit finite element analysis. First, the crashworthiness of honeycomb sandwich panel and the bare honeycomb core are compared with each other in the aspects of specific energy absorption and peak crushing force. The comparative results show that honeycomb sandwich panel can absorb more energy than the bare honeycomb core, though the peak crushing force of honeycomb sandwich panel is larger. Then the factor screening experiments are carried out to find out variables that have significant effects on the crashworthiness of honeycomb sandwich panel. The ultimate purpose of factor screening experiments is to decrease the computational expense by reducing the number of design variables. Finally, the dual response surface method and the crossed array design are employed to formulate the complex robust optimization design problem. The regression expressions of specific energy absorption and peak crushing force are defined as the objective and constraint function respectively in the robust design of crashworthiness optimization.

Dynamic axial crush response of circular cell honeycombs

The dynamic axial crush response of circular cell polycarbonate honeycombs was studied for 3-cell and 7-cell specimens experimentally and through finite-element (FE) simulation. The experiments were conducted using two loading methods: (i) the wave loading device (WLD) method and (ii) the direct impact method (DIM). The specimens were subjected to crush velocities of about 12 000 mm s −1 in the WLD method and 5000 mm s −1 in the DIM. The two methods were used to obtain a fairly wide range of input velocities. The collapse sequence and displacement information of the specimens were captured using a high-speed camera. The mode of collapse was through progressive concertina-diamond fold formation over a fairly constant state of load, which is referred to as the crush load. The crushing was simulated using an explicit FE analysis using ABAQUS, with geometrically imperfect 3-cell and 7-cell honeycomb models that incorporated the rate-dependent properties of polycarbonate. The FE results were found to agree well with the experimental results in terms of overall force–displacement plots, thus providing a basis to extract energy absorption estimates from the models and to draw comparisons between the 3-cell and 7-cell response behaviour. Moreover, the dynamic crush results were compared against a quasi-static axial crush response to demonstrate the presence of rate effects.

Finite element analysis of multi-particle impact on erosion in abrasive water jet machining of titanium alloy

Abrasive water jets (AWJs) are finding growing applications for machining a wide range of difficult-to-machine materials such as titanium alloys, stainless steel, metal matrix and fibre reinforced composites, etc. Current applications of AWJs include machining of Titanium alloys for aircraft components and bio-medical implants to removal of aircraft engine coatings. This paper presents the application of an elasto-plastic model based explicit finite element analysis (FEA) to model the erosion behaviour in abrasive water jet machining (AWJM). The novelty of this work includes FE modelling of the effect of multiple (twenty) particle impact on erosion of Grade 5 Titanium alloy (Ti-6Al-4V). The influence of abrasive particle impact angle and velocity on the crater sphericity and depth, and erosion rate has been investigated. The FE model has been validated for stainless steel and yields largely improved results. Further, the same FEA approach has been extended to model the multi-particle impact erosion behaviour of Titanium alloy.

An extensive study of a ship's survivability after collision – A parameter study of material characteristics, non-linear FEA and damage stability analyses

Throughout the world, ships are continuously being declared as total losses and a significant part of these accidents are collisions between ships. The International Maritime Organization strives towards a more risk-based view on addressing the damage stability of ships. The current study addresses the survivability following a ship collision by the use of a sequential (de-coupled) computational methodology. The methodology is comprised of structural analysis of a collision scenario followed by dynamic damage stability simulations of the struck ship in order to establish the time to capsize of the struck ship. The emphasis of the current investigation is on the structural computations of the collision event; explicit finite element analyses are presented for a case study of a collision scenario. In particular, uncertainties of input parameters in the finite element simulations and their impact on the shape and size of the damage opening area, and time to capsize of the struck ship, are addressed. Material modelling aspects are studied; scatter in material properties within a material class as well as damage modelling. In addition, the effects of using a deformable or rigid striking bow section, the friction coefficient, the collision angle and the speed of the striking ship are studied. On the basis of the results presented, assumptions commonly used in these kinds of analysis are discussed. Recommendations for a sufficient level of simplifications for arriving at reliable results in numerical simulation of ship collisions are made.

Investigation of the feasibility and effectiveness in using heat pipe-embedded drills by finite element analysis

Drilling is a sufficiently severe machining process coupled with thermomechanical effect, in which mechanical work is converted to heat through the plastic deformation involved in chip formation and friction between tool and workpiece. The elevated temperature at the tool–chip interface has deleterious effects on the dimensional accuracy of the workpiece and shortens the service life of the tool. In this paper, the feasibility and effectiveness of heat pipe cooling in drilling operations are investigated numerically. A new embedded heat pipe technology was utilized to remove the heat generated at the tool interface in the foregoing cutting process. Numerical studies involved four different cooling conditions, i.e., dry drilling, fluid cooling, heat pipe cooling, and heat pipe cooling with cutting fluid supplied. The thermal, structural static, and dynamic characteristics of the drill were investigated using a numerical calculation with fast finite element plus solvers based on explicit finite element analysis software COSMOS\works. The results demonstrate that the heat pipe drill is most feasible and effective in the actual drilling processes.

Simulation methodology development for rotating blade containment analysis

An experimental and numerical investigation on the aeroengine blade/case containment analysis is presented. Blade out containment capability analysis is an essential step in the new aeroengine design, but containment tests are time-consuming and incur significant costs; thus, developing a short-period and low-cost numerical method is warranted. Using explicit nonlinear dynamic finite element analysis software, the present study numerically investigated the high-speed impact process for simulated blade containment tests which were carried out on high-speed spin testing facility. A number of simulations were conducted using finite element models with different mesh sizes and different values of both the contact penalty factor and the friction coefficient. Detailed comparisons between the experimental and numerical results reveal that the mesh size and the friction coefficient have a considerable impact on the results produced. It is shown that a finer mesh will predict lower containment capability of the case, which is closer to the test data. A larger value of the friction coefficient also predicts lower containment capability. However, the contact penalty factor has little effect on the simulation results if it is large enough to avoid false penetration.

Numerical Analyses to Investigate the Feasibility and Effectiveness in Using Heat Pipe Embedded End Mills

In this paper, the feasibility and effectiveness of heat pipe cooling in end milling operations are investigated. A new embedded heat pipe technology was utilized to remove the heat generated at the tool-interface in end milling processes. Numerical studies involved four cases, including dry milling, fluid cooling, heat-pipe cooling and heat-pipe cooling with cutting fluid supplied. The thermal, structural static and dynamic characteristics of the end-mill were investigated using a numerical calculation with Fast Finite Element (FFE) plus solvers based on explicit finite element analysis software. The results demonstrate that the heat pipe end-mill is most feasible and effective in the actual end milling processes.

Explicit dynamic finite element analysis of an automated grasping process using highly damped compliant fingers

This paper has been motivated by the need to reduce the number of live animal tests in the development of an automated live-bird transfer system (LBTS) for the poultry meat-processing industry. Simulation-based models have been developed, which carefully address key engineering issues prior to live animal tests so that physical experiments can be focused on understanding reflex issues such as fear and escape behavior. To gain insights into the effects of operational timing on the LBTS handling performance, the multibody dynamics is modeled numerically based on the method of explicit dynamic finite element analysis (FEA) using off-the-shelf FEA packages. The findings also offer information on contact forces and their locations acting on the object’s body and legs by the compliant fingers and grippers respectively for optimizing designs and avoiding damage to the object. Specifically, this paper discusses computational issues such as time-step considerations and highly damped behavior of compliant fingers when modeling using dynamic FEA methods. The FEA model has been validated by comparing simulated handling of an ellipsoidal object by a pair of robotic hands with multiple compliant fingers against published experimental data. It is expected that the FEA-based method presented here can be extended to a spectrum of applications where flexible multibody dynamics involving large deformable contacts and highly damped behaviors plays an important role.

Simulation of Rolling Forming of Precision Profile Used for Piston Ring based on LS_DYNA

The rolling process of precision profile used for piston ring is simulated by large general-purpose explicit dynamic finite element analysis software ANSYS/LS_DYNA. The modeling of finite element models, the selection of material models and element types, the meshing of the model are introduced in detail. The rolling metal flow rulers of each pass are gained. The deformation of rolled piece and distribution of stress field are analyzed deeply. These can provide guidance for the design of forming roller and the optimization of process.

1A1-R07 陽解法有限要素法解析による蚊の穿刺メカニズムの検討(バイオミメティクス・バイオメカトロニクス(1))

Explicit finite element analysis (FEM) is applied to the analysis, in which microneedles imitating mosquito's proboscis are inserted to a viscoelastic material imitating human skin. The needles are central straight one imitating labrum, and side two needles imitating maxillas. The results obtained by simulation are as follows: 1) jagged shape of side needle is effective for reducing resistance force in forward motion due to decrease of contact area between needle and skin organism, 2) it has anchoring effect in backward motion, which eases the forward motion of central straight needle, 3) cooperative motion of these three needles makes the insertion force lower, which may be useful for low-invasive insertion of medical needle in future. A microneedle of bundling three needles is fabricated by MEMS technique, which imitates the shape and size of real mosquito. Using this bundled needle, the above-mentioned effect of cooperative three needles motion having phase to each other is experimentally confirmed.

Dynamic Modeling of Damping Effects in Highly Damped Compliant Fingers for Applications Involving Contacts

In many industries, it is often required to transfer objects using compliant fingers capable of accommodating a limited range of object shapes/sizes without causing damage to the products being handled. This paper presents a coupled computational and experimental method in time domain to characterize the damping coefficient of a continuum structure, particularly, its applications for analyzing the damping effect of a highly damped compliant finger on contact-induced forces and stresses. With the aid of Rayleigh damping and explicit dynamic finite element analysis (FEA), this method relaxes several limitations of commonly used damping identification methods (such as log-decrement and half-power methods) that are valid for systems with an oscillatory response and generally estimate the damping ratio for a lumped parameter model. This damping identification method implemented using off-the-shelf commercial FEA packages has been validated by comparing results against published data; both oscillatory and nonoscillatory responses are considered. Along with a detailed discussion on practical issues commonly encountered in explicit dynamic FEA for damping identification, the effects of damping coefficients on contact between a rotating compliant finger and an elliptical object has been numerically investigated and experimentally validated. The findings offer a better understanding for improving grasper designs for applications where joint-less compliant fingers are advantageous.

Survivability analysis of a struck ship with damage opening – influence from model and material properties uncertainties

The conditions for damage stability and survivability of a ship struck in a collision in arbitrary sea-state are, from a structural point of view, determined by the size and shape of the damage opening in its side-shell. In the current investigation, explicit finite element analyses (FEA) are presented of a ship-to-ship collision scenario in which the damage opening of a struck ship is calculated for a selection of damage degradation models and realistic material properties, here referred to as model and material properties uncertainties. The model uncertainty is considered as a possible (user-related) insecurity in the selection of the most appropriate damage criterion for the analysis; the shear failure and the forming limit diagram (FLD) criteria were compared in the current investigation. The uncertainty in material properties is accounted for in the constitutive material model description and the material parameters used in the two damage criteria. The size and shape of the damage openings predicted by the FEA are used in damage stability analyses in which the struck ship is subjected to wave motions in an arbitrary sea-state and flooding into the damage opening. The survivability of the struck ship is estimated for all of the damage opening cases. One of the main conclusions is that the high degree of accuracy that a researcher on structure analysis strives for has to be considered together with the natural variation of the sea-state that defines the characteristics in the following damage stability analysis. Consequently, by adoption of a holistic approach in which structural integrity and damage stability research are combined using a systematic parameter (sensitivity) and collision-scenario-based analysis, simplified models and criteria can be developed more efficiently and with higher precision. It will also be clearer which variables are the most important to focus on when analysing the survivability or risk for capsizing.

Modeling of the dynamic delamination of L-shaped unidirectional laminated composites

One of the widely used geometrically complex parts in advanced commercial aircraft is the L-shaped composite. Due to the sharp curved geometry, interlaminar opening stresses are induced and delamination occurs under considerable mode-mixities in L-shaped beams. Dynamic phenomena during delamination initiation and propagation of L-shaped beams are investigated using dynamic (explicit) finite element analysis in conjunction with cohesive zone methods. The 2-D model consists of 24 plies of unidirectional CFRP laminate with an initial 1 mm crack at the center of the laminate at the bend. Loading is applied parallel to one of the arms quasi-statically. The loading type yields different traction fields and mode-mixities in the two sides of the crack in which delamination occurs under shear stress dominated loading on one crack tip and opening stress dominated loading on the other. The speed of the delamination under shear dominated loading at one side is 800 m/s and under normal stress dominated loading is 50 m/s. In addition radial compressive waves at the interface are observed. Finally, as the thickness is changed, a different failure mode is observed in which a secondary crack nucleates at the arm and propagates towards the center crack.