Explicit Dynamic Finite Element Analysis Research Articles

In-silico modelling of multi-strike insertion and torsional resistance of tapered revision hip stems: Insight into spline design philosophy.

Despite the clinical success of tapered splined titanium stems, a knowledge gap still exists between spline design and its primary mechanical stability, which is critical to the long-term success of revision hip arthroplasty. Additionally, almost all published pre-clinical studies relied on resource-intensive benchtop and cadaveric testing. Hence, the present study developed a novel computational model to investigate effects of spline geometry and configuration on axial and torsional stability of tapered stem. Dynamic explicit Finite Element Analysis coupled with a state-of-the-art adaptive meshing technique was used to simulate the highly non-linear contacts and large bony material deformations. Hybridising primary straight splines with secondary angled splines results in 41% and 10% increases of peak insertion force and post-seating moment than the predicate device for the same seating position. The primary straight splines cut at multiple circumferential bony locations, enhancing torsional stability; while the alternatively placed secondary angled splines form wedges with the bone, providing reliable seating and additional torsional resistance. To the best knowledge of the author, this is the first in-silico investigation of its kind to simulate multi-strike seating and torsional resistance of revision hip stems, offering an effective and efficient platform for future multi-factorial parametric study and uncertainty quantification.

Blast enhanced façade design by means of an optimal balance between security and sustainability

The major objective of this paper is to show that glazed curtain wall has a surprising potential for blast enhancement. However, often this potential is partially lost because of inaccurate and only presumed safe side approach. Indeed, in curtain wall it is much important to assess properly the beneficial effect of the deformable supports, framing and possibly brackets, on the glazing response under blast wave effects. Only in this way a true balanced design approach can be carried out and the protective requirement can be integrated into the façade design by preserving the architectural requirements, comfort, classical energy efficiency requirements and novel demand for sustainability. On the other side the large variability of materials and component behaviour under nonlinear range and the uncertainties related to the blast threat recommend a flexible calculation tool, which must be coupled with a sensitivity analysis on the most relevant inputs. For this reason, a Multi Degree of Freedom approach shows several advantages with respect to the Explicit Dynamic Finite Element Analysis, considering also the large number of geometry, component design and blast load variations are existing in a typical application of the protection on a high rise building. The impact of the calculation method is demonstrated by means of a comparative exercise and by means of real case applications.

A numerical strategy for predicting the interface stresses in metal strip rolling with small reduction

This paper has developed a numerical strategy for predicting the interface stresses in metal strip rolling at a small reduction. Key rolling factors such as the roll elasticity, fluid lubrication, random asperity contacts, asperity-lubricant interaction, rolling speed and reduction were comprehensively integrated into the numerical analysis. The random asperity contact at the roll-strip interface was addressed by a statistical approach with considering the elastoplastic deformations of surface asperities. A transient average Reynolds equation was utilised to deal with the fluid flow subjected to the interruptions caused by the asperity contacts. With the aid of a dynamic explicit finite element analysis, a novel modularised strategy was established to systematically accommodate the mathematical models governing the above key rolling factors, which allows the affordable computation and the effective predictions of contact characteristics in the strip rolling. It was found that both the lubrication and microscale asperity contacts disturb considerably the contact stresses at the rolling interface, and that a proper selection of rolling conditions can reasonably regulate the stresses.

Strain prediction and benchmark with measurement in the Spallation Neutron Source mercury target without gas injection

The 1.4-MW Spallation Neutron Source (SNS) currently operates as the world's highest time-average power spallation source and uses mercury as the spallation target material. The mercury circulates through a stainless-steel target vessel and heat exchanger loop that removes the heat deposited from the incident proton beam in the target. The mercury vessel is part of the fixed but replaceable target module. The target module is not safety credited in the SNS design, but reliable long life is vital for meeting operational goals and minimizing cost and waste. SNS is a short-pulse ($\ensuremath{\sim}0.7\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$) neutron source with a repetition rate of 60 Hz with 1.0 GeV protons onto the target. The short-pulse operation introduces two mechanisms that threaten the longevity of the mercury vessel. The pulsed target heating is essentially isochoric, which results in a distributed pressure field in the mercury with each pulse. After each pulse, the pressure propagates, interacts with, and strains the stainless-steel vessel. For intermittent times, this pressure field leads to mercury cavitation. The first mechanism of concern for the target lifetime is high-cycle fatigue to the stainless-steel vessel and the second is cavitation erosion. At the onset of the SNS project, the R program sought to address the need for an accurate and practical method to estimate the fatigue life of the mercury vessel. Around 2000, the R team conducted a series of in-beam mercury target experiments at the Weapons Neutron Research Facility at Los Alamos Neutron Science Center. These experiments successfully produced a small database of pulse response strain data. The data were used to develop and benchmark an explicit dynamic finite element analysis technique for estimating target fatigue life. SNS is now a mature facility with about 15 years of operation and 29 SNS target modules consumed. Since 2015, strain measurements have been collected from actual targets, and abundant target vessel strain data are now available in greater detail than was possible in 2000. Variances in pulse response data have been characterized using tolerance interval analysis to benchmark the simulation technique more thoroughly. The simulated results were found to match measurements generally well, but the method is always conservative. A potential adjustment to the cavitation threshold parameter value was suggested. Variances in the pulse response data are moderate, which is largely explained by the fact that data were acquired in 60-Hz burst mode and by the lasting vibration of the vessel between pulses.

A Study on Impact Force Detection Method Based on Piezoelectric Sensing.

Impact force refers to a transient phenomenon with a very short-acting time, but a large impulse. Therefore, the detection of impact vibration is critical for the reliability, stability, and overall life of mechanical parts. Accordingly, this paper proposes a method to indirectly characterize the impact force by using an impact stress wave. The LS-DYNA software is utilized to establish the model of a ball impacting the steel plate, and the impact force of the ball and the impact response of the detection point are obtained through explicit dynamic finite element analysis. In addition, on this basis, a correspondence between the impact force and the impact response is established, and finally, an experimental platform for impact force detection is built for experimental testing. The results obtained by the finite element method are in good agreement with the experimental measurement results, and it can be inferred that the detected piezoelectric signal can be used to characterize the impact force. The method proposed herein can guide the impact resistance design and safety assessment of structures in actual engineering applications.

A multiscale soft-contact modelling method for rough surfaces in contact with coupled slipping/sliding and rolling

This paper presents a multiscale soft-contact modelling (SCM) method for characterising the rough surfaces in contact with coupled slipping/sliding and rolling. The microscale flattening of the random surface asperities subjected to a plastically deformed substrate was accommodated by a statistical analysis with a dynamic explicit finite element analysis (FEA). A soft-contact algorithm was developed to effectively treat the cross-scale deformation of the microscopic asperities and that of the macroscopic body. An efficient modularised strategy including an input module and a hybrid SCM-FEA module was established to analyse the interaction at the interface of the two contacting bodies associated with coupled slipping/sliding and rolling. The modelling method was validated by a typical metal forming process, cold rolling of metal strips.

HD-lubricated high-speed small reduction rolling of hard steel strips with elastically deformable work rolls

This research investigates the effects of elastic work rolls on the hydrodynamic (HD)-lubricated high-speed rolling of hard steel strips with a small reduction. An innovative numerical method was established to couple the interactions across deformable rolls, pressurised lubricant and strips undergoing elastoplastic deformation. A dynamic explicit finite element analysis (FEA) was used to obtain the deformed solid bodies while a transient Reynolds equation was utilised to govern the hydrodynamic pressure. A non-linear lubricant shearing stress was integrated in obtaining the interface friction. The analysis demonstrates that the hydrodynamic pressure can be more affected by the yield strength of the metal strip and roll radius for a fixed rolling gap in lubricated strip rolling.

Deployment Dynamics Analysis of an Origami-Folded Spacecraft Structure with Elastic Hinges

Self-actuated deployable space structures present a novel challenge for deployment dynamics modeling efforts, where the system-level influence of strain energy components must be captured. Here, the free deployment of an origami-folded structure through actuation of strain energy hinges is studied. Studies include experimental testing, multibody dynamics modeling, and finite element modeling. An approach for modeling high strain tape spring hinges for use in a multibody simulation of free-deployment dynamics analysis is presented and demonstrated. This approach considers hinges with multiple degrees of freedom beyond the primary fold axis angle. A novel folded deployable structure is designed and prototyped with a segmented fold pattern and strain energy hinges integrated in the design. A suite of deployment tests is conducted on the prototype using videogrammetry. A full simulation of the prototype is constructed from a multibody dynamics model and the hinge model, and the predicted deployment behavior for relative hinge states is evaluated against the experimental testing. Additionally, the prototype deployment is replicated using an explicit dynamic finite element analysis for a performance comparison. The models demonstrate strong correlation for deployment time predictions across the relative hinge states, and the finite element analysis correlates all deployment behaviors.

Modal Research of Underground Arch Structure With Elastic Support

Elastic support is a commonly used method of vibration isolation and vibration reduction. The research on the mode of underground arch structure with elastic support can improve the battlefield survival ability of personnel and equipment in underground protection engineering. In this paper, the ANSYS/LS-DYNA nonlinear explicit dynamic finite element analysis program is used to numerically simulate the mode of the elastically supported underground arch structure, and the natural vibration circle frequency variation curve and mode diagram of the structure are obtained. The results show that the elastic support reduces the natural frequency of the structure, prolongs the natural vibration period of the structure, and has a good vibration isolation and vibration reduction effect; the critical stiffness coefficient causes the first and second modes of the structure to be easily excited at the same time, which should be avoided in structural design.

Targeting the acceleration-time response of vehicle structures under crash impact using equivalent dynamic loads

This work introduces an optimization procedure derived from the targeting force-displacement response (TFDR) method to improve the crashworthiness of full-size vehicle structures. The proposed method aims at targeting the vehicle’s acceleration-time response (ATR) under a crash event using topometry (thickness) optimization. In contrast to the original TFDR method, the proposed targeting method uses a moving coordinate system (MCS) that allows addressing fully dynamic crash models with initial velocity. By setting a proper target ATR curve, the proposed method can improve several crashworthiness indicators including specific energy absorption, maximum deceleration, dynamic penetration, and crash load efficiency. The result of the topometry optimization could be a guideline for the further design. In the proposed method, the nonlinear optimization problem is discretized into a series of analytical subproblems using equivalent dynamic load (EDL). In each iteration, the dynamic response from an explicit dynamic finite element (FE) analysis is utilized to define and solve a subproblem. To demonstrate the proposed iterative method, the baseline FE model of a Dodge Grand Caravan vehicle, obtained from the US National Highway Traffic Safety Administration (NHTSA) website, is optimized. The results show the effectiveness of the algorithm finding the element thickness distribution to make the acceleration-time response of the vehicle’s center of gravity (VCG) gradually approach a target curve. The proposed EDL algorithm finds a converged solution using less than 15 crash simulations. This makes it possible to solve problems involving full-size vehicle FE models.

Modeling and Simulation of RDX Powder Thermo‐Mechanical Response to Drop Impact

AbstractA computational framework to predict the deformation, flow, and compaction of an energetic material (EM) powder subjected to drop impact is discussed. Explicit dynamic finite element analysis was performed to simulate drop‐weight impact tests for comparison with experimental results and to gain insight into the ignition sensitivity of RDX powder. The computations simulated the Thermo‐Mechanical behavior of a thin layer of energetic powder subjected to drop impact to study the dependence of ignition sensitivity on the anvil material properties. By modeling high strength steel and a low strength copper anvil, a direct comparison is made on how energy dissipation within the EM is influenced by anvil properties. A hybrid finite element model is introduced that captures the mesoscale discrete particle nature of the powder response in regions of interest while using a continuum model elsewhere to reduce computational cost. To capture the mesoscale behavior, a multi‐particle finite element method (MPFEM) approach was used in selected regions in the hybrid model. Powder temperatures were computed to understand how the striker impact energy is dissipated by plasticity and friction into localized heating of the EM that triggers the ignition. Munition designers can use such a framework to study the low‐level impact sensitivity of munitions in a computationally efficient manner. Results of the simulation using the hybrid model suggest that copper anvil undergoes plastic deformation which absorbs a significant portion of the impact energy reducing the energy dissipated within the EM and suppressing ignition.

An Investigation into the Texture Transfer in the Process of Lubricated Skin Pass Rolling

Abstract This article investigates the surface texture transfer mechanisms in lubricated skin pass rolling of metal strips with three-dimensional rough surfaces of both regular patterns and random surface asperity distributions. Two important steps have been completed. The first is the successful establishment of an efficient numerical method for predicting the 3D texture transfer. It was identified that the new method can be used reliably with the key complex factors coupled in skin pass rolling, such as the effects of lubricant and surface roughness. The second is the exploration of the texture transfer mechanisms with the aid of this new method. In addition, the effects of hydrodynamic pressure on the texture transfer efficiency were comprehensively investigated by a dynamic explicit finite element analysis. It was found that lubrication plays a critical role in determining the surface texture transfer. The texture transfer ratio decreases with increasing the lubricant viscosity. A larger pressure coefficient brings about a lower texture transfer ratio, but a larger reduction ratio leads to a greater texture transfer.

Exploring simplification methods in reducing simulation time for drop test analysis

- Automotive electronics can produce an unprecedented level of passenger comfort and optimized performance of engine and components. However, the increasing intricacy of these electronic devices makes them more susceptible to damage due to thermal loads, mechanical drops, and engine vibrations. While physical handling of automotive components is comparatively rare, the weight and complexity of specific components such as the ECU, power module, and sensor modules, makes any drop functionally fatal. Simulation approach is considered to be essential in solving these problems by minimizing costs and effort. This paper attempts to solve the issue of mechanical drops using an explicit dynamics finite element analysis solver. Moreover, simplification methods are applied to further minimize solution costs.

In-plane dynamic crushing behaviors of joint-based hierarchical honeycombs with different topologies

Introducing the hierarchy into cellular materials has attracted increasing attention in the effort to pursue improved absorbed-energy abilities and impact resistance. In this paper, the dynamic crushing properties and energy absorption capacities of joint-based hierarchical honeycombs with different topologies were explored by means of explicit dynamic finite element (FE) analysis using ANSYS/LS-DYNA. Four types of joint-based hierarchical honeycombs with uniform cell-wall thickness were firstly constructed by substituting each vertex of regular honeycombs with a smaller self-similar cell (hexagon or square). The respective influences of hierarchical parameters and impact velocities on in-plane dynamic deformation modes, mechanical characteristic and energy absorption of joint-based hierarchical honeycombs were discussed. Research results showed that the hierarchy had a far greater influence on the in-plane deformation modes of honeycombs. Compared with regular honeycombs, the dynamic plateau stress and specific energy absorption of joint-based hierarchical honeycombs can be improved if the proper hierarchical parameters were chosen. Adding the joint-based hierarchy into regular honeycombs can enhance the crushing stress efficiency (CSE) of the specimens. In addition, by introducing a non-dimensional dynamic sensitivity index, the dynamic shock enhancement of hierarchical honeycombs was also investigated. These researches are useful for the multi-objective dynamic optimization design and controllable properties of cellular materials.

Mechanical Design of Long-Term Body-Adhered Medical Devices to Maximize On-Body Survival

Long-term, body-adhered medical devices rely on an adhesive interface to maintain contact with the patient. The greatest threat to on-body adhesion is mechanical stress imparted on the medical device. Several factors contribute to the ability of the device to withstand such stresses, such as the mechanical design, shape, and size of the device. This analysis investigates the impact that design changes to the device have on the stress and strain experienced by the system when acted on by a stressor. The analysis also identifies the design changes that are most effective at reducing the stress and strain. An explicit dynamic finite element analysis method was used to simulate several design iterations and a regression analysis was performed to quantify the relationship between design and resultant stress and strain. The shape, height, size, and taper of the medical device were modified, and the results indicate that, to reduce stress and strain in the system, the device should resemble a square in shape, be short in height, and small in size with a large taper. The square shape experienced 17.5% less stress compared to the next best performing shape. A 10% reduction in device height resulted in a 21% reduction in stress and 24% reduction in strain. A 20% reduction in device size caused a 7% reduction in stress and 2% reduction in strain. A 20% increase in device taper size led to a negligible reduction in stress and a 6% reduction in strain. The height of the device had the greatest impact on the resultant stress and strain.

Direct measurement of shot velocity and numerical analysis of residual stress from pneumatic shot peening

Shot peening is widely used in several fields to improve the fatigue strength of manufactured parts via the introduction of compressive residual stresses. The shot velocity is significant physical factor; however, it is difficult to measure this velocity directly in pneumatic shot peening. In this study, an experiment was performed to record shot movement with a high-speed camera. Particle image velocimetry (PIV) was used to measure the shot velocity distribution: the shot accelerated after being projected from the nozzle and reached a steady shot velocity at approximately 80 mm from the nozzle. The steady shot velocity was proportional to approximately the 0.51st power of the air pressure: 30 m/s at 0.14 MPa and 49 m/s at 0.35 MPa for steel shot ASR170. For an A7075 aluminum alloy, the depth of the compressive residual stress increased with the shot velocity and was greater than 0.5 mm at 0.35 MPa air pressure. Finite element analysis (FEA) was performed on the residual stress distribution with the shot velocity measured by PIV as the input value. Peening with multiple shots was evaluated through dynamic explicit FEA. The residual stress distribution after shot peening was obtained through subsequent static implicit FEA. The analytical results for the residual stress distribution complied with the experimental results. Thus, the shot velocity measurement technology and the FEA model that were used to calculate the residual stress from shot peening were both validated.

Effect of the Reinforced Concrete Slab on the Blast Shock Wave Properties

Based on advanced numerical simulation technologies, such as the birth and death of element technique, large displacement technique, and fluid-solid coupling mechanism, and combined with the strain rate effect of concrete and steel materials, a complicated finite element model of a TNT–air–slab system is set up using the nonlinear explicit dynamic finite element analysis software LS-DYNA. A series of numerical simulation analyses is conducted on the reinforced concrete slab to evaluate the properties of the blast shock wave at the back of the slab. First, the typical characteristics of the blast shock waves at the front and back of the slab are described concisely. Then, the relation between the incident wave and the reflected wave is built by further studying the influence of the slab on the properties of the reflected wave at the front of the slab. And then, the relation between the reflected wave and the reformed wave is established by analyzing the effect of the slab on the change law of the reformed wave at the back of the slab. Finally, the basic steps for predicting the properties of the reformed wave are given considering the effect of the reinforced concrete slab on it. In addition, the case study demonstrates that the predicted results are true and reliable, and it indicates that the proposed method can accurately and effectively predict the properties of the reformed wave at the back of the reinforced concrete slab.

Research on Response Characteristics of Hydraulic Gate Subjected to Non-contact Underwater Explosion Load

In this paper, the response characteristics of deep-hole planar steel gates under the separate induction of bubble pulsating load are studied. Through the large-scale finite element simulation software ABAQUS, using the explicit dynamic finite element analysis method, the contact surface of the gate and the water is taken into account by the fluid-solid coupling algorithm. When the water level is constant, the gate is subjected to explosion and the impact of the generated bubble impact on the gate structure and its anti-explosion ability are analyzed. The equivalent stress, displacement, and equivalent plastic strain of the gate under six different cases were simulated. Then, the effect of bubble pulsating load on the stress characteristics of the gate and the anti-explosion ability of the gate were summarized.

Preliminary of finite element analysis (FEA) investigation on the stent expansion

The requirement of stent expansion is important to stent deployment on the inner of the defected blood vessel. This defected blood vessel decreases in lumen diameter size because of accumulation of fat or plaque and caused the reduction of blood flow and oxygen supply to overall body. According to clinical guidelines, blood vessel that blockage by 70% need to be stenting. Stent expand past it elastic limit and plastically deform until the targeted diameter is achieved. Explicit dynamics Finite Element Analysis (FEA) was used in this paper to analyse the stent expansion process. The knowledge of stent radial displacement could prevent the injury of inner surface of artery while understanding on longitudinal foreshortening that aided the stent placement on targeted artery location. The controlled variable was geometry, material and boundary condition of stent. The manipulated variable was the speed of pressure application. The outcomes of this stent expansion simulation are maximum radial expansion, the uniform of radial displacement and longitudinal foreshortening. This simulation results help to improve stent installation on human body for balloon expandable stent and increase the understanding of explicit dynamics structure simulation of finite element in biomedical application.

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.