Explicit Dynamic Analysis Research Articles

Modeling of wound ballistics in biological tissues simulators

Modern weapons cause severe damage, accompanied by high rates of complications and mortality. The investigation of such kinds of weapons is in high demand considering the ongoing active phase of russia's war against Ukraine since February 2022. In order to understand the pathological processes that occur in and outside the gunshot wound, we conducted an experimental study using mathematical simulation. The results presented in the article will help to choose the appropriate surgical management and improve the results of treatment. The aim of this study was to investigate and evaluate the damaging effect of a 5.45 mm 7N6M bullet and a 5.45 mm V-max expansive bullet using numerical modeling of wound canals in ballistic plasticine. The Ansys Explicit Dynamics engineering complex was used to simulate the dynamics of the bullet’s motion. The basic equations, solved by the explicit dynamic analysis, express the conservation of mass, momentum, and energy in Lagrange coordinates. Together with the material model and the set of initial and boundary conditions, they determine the complete solution to the problem. Taking into account that the initial velocity of the bullet is 1185 m/s at a mass of 3.9 g, we obtain energy 2740 J. All this energy acts at the area of the wound canal with a depth of 150 mm. Injury with a conventional 7N6M bullet is characterized by the fact that it passes through the block and loses only part of the kinetic energy. The simulation results showed that the velocity of the bullet at the outlet is 220 m/s. Taking into account the initial velocity of the bullet 918 m/s with a mass of 3.4 g, we obtain the kinetic energy acting on the walls of the wound canal with a depth of 200 mm of about 830 J. Mathematic analyses showed that the expansive bullet has a soft core that deforms and transfers all the kinetic energy to the tissues immediately after penetration into the tissues. The loss of kinetic energy of the bullet (ΔE, J) is defined as the difference between the kinetic energy at the time of injury (Ec, J) and the residual energy of the bullet when leaving the material (Er, J). Numerical modeling of wound ballistics in biological tissue simulators allows us to determine with high accuracy the features of wound canal formation and tissue response to damage of bullets having different kinetic energy, which contributes to the choice of adequate surgical management during surgery for gunshot wounds.

Analysis of the explosion resistance of an I-shaped steel‒concrete composite structure under contact explosion

Reinforced concrete and steel structures are commonly used in bridge construction; thus, researchers have conducted relatively comprehensive analyses of their dynamic responses and damage mechanisms under blast loads. However, for a new type of I-shaped steel‒concrete composite structure with various structural performance advantages, there remains a lack of effective experiments and analyses of damage modes. In this paper, three I-shaped steel‒concrete composite specimens are designed and fabricated, and explosion experiments under different explosion scenarios are performed. The experimental results show that under the support of an I-shaped steel plate, the structure has a strong ability to withstand the blast load. The concrete damage area on the rear blast surface is small, and the I-shaped steel plate does not yield under a small explosive equivalent. Based on the experimental results, the dynamic response and failure behavior of the I-shaped steel‒concrete composite structure are numerically evaluated using Autodyn explicit dynamic analysis software. By considering different working conditions and by taking the deformation and damaged areas of the structure as the damage index, the key explosion resistance factors of the structure under contact explosion are studied. Some important structural parameters greatly influence the explosion resistance of the structure, including the thickness of the I-shaped steel plate; however, increasing the strength of concrete does not significantly improve the explosion resistance of the composite structure.

Impact Damage Analysis of Skid Landing Gear of the UAV

In this paper, by analyzing the structure and material characteristics of skid landing gear, the skid landing gear model is established by using CATIA software. In the explicit dynamic analysis type of ANSYS software, the force comparison between the impact surface of soil material and the impact surface of rigid material is made, combined with the change of momentum and energy in the process of touching the ground. This explains the necessity of landing drones on soft landing surfaces such as soil. In addition, LS-DYNA was used to simulate the dynamics of landing gear, and the strength of landing gear was analyzed according to failure criterion.

Dynamic Behavior Analysis of I-Shaped RC Beams under Combined Blast and Impact Loads

The existing literature mainly focuses on the research of reinforced concrete (RC) beams under a single load such as blast or impact. In this paper, the slab–rib–slab RC beam, a new type of structure widely used in bridge structures, was taken as the research object. The explicit dynamic analysis software LS-DYNA was used to numerically analyze the dynamic response and failure behavior of I-shaped RC beams under combined blast and impact loads. For this reason, an effective numerical analysis model was obtained by carrying out experiments on I-shaped RC beams under contact explosion. The key factors affecting the dynamic response of the structure under combined loads were numerically analyzed. Numerical results showed that different load application sequences have important effects on the dynamic response of the structure. When the impact load was first applied to the structure, more severe concrete damage and deformation occured in the depth direction of the beam. However, when the blast load was first applied to the structure, the concrete at the lower flange was damaged in the span direction of the beam due to tension, and no large-scale concrete spallation occurred in the depth direction. This was mainly due to the different mechanisms of blast and impact loads. In addition, the vulnerability of the I-shaped RC beams varied with some structural parameters, including span, depth, and configuration of reinforcement. At the same time, the results showed that the structure is more sensitive to changes in structural parameters when it is first subjected to impact loads.

Virtual Lab Simulator in Mechanical Engineering Education-Hybrid Approach

Many universities worldwide are partially disrupting their education by the spread of the coronavirus. Consequently, the Universities took the necessary steps to change their teaching methods to online laboratory experiments and workshops. However, universities should continue to maintain their higher education standards and provide a high-quality student experience required for the learning outcomes associated with each degree program. Adhering to online teaching methods for both theory and practical lectures has created a challenge in education. The discussion of the theory lessons by showing PPTs and video presentations was comfortable for students. In addition to that, virtual labs came into existence. These virtual labs had a significant impact on students' learning process, but this did not apply to all labs. This paper projects the outcome of the virtual lab using the explicit dynamic analysis application in solid works software and integration of AR & VR teaching techniques. This paper also includes the work done by the students and the effective outcome utilization of virtual labs compared with practical labs by using mild steel specimens.

Multidisciplinary Structural Optimization of Low-Pyroshock Separation Nuts for Aerospace

This paper presents a multidisciplinary structural optimization approach to design separation nuts with low-level pyroshock responses for aerospace. A parametric modeling method is developed to automatically construct a multibody finite element model for separation nuts according to the predefined structural parameters. A new explicit dynamics analysis workflow tailored to separation nuts is proposed to simulate the pyroshock environment efficiently. Based on a backpropagation neuron network technique, certain surrogate models are established to describe the equivalence relationship between the structural parameters and the multidisciplinary structural responses including the pyroshock, the bending stiffness, and the structural weight. Finally, a pyroshock minimization problem with the constraints of structural weight and bending stiffness is solved by using a genetic algorithm, resulting in an optimized low-pyroshock separation nut design. The comparison between the optimized structure and a reference structure shows the effectiveness of the proposed approach.

Impact Analysis of Bio-composite Laminate for Low and Intermediate Velocity Application

The bio-composite materials are compatible with many diversified applications except in marine or submerged instances. An attempt is made in this work to foresee the bio-composite built with Poly Lactic Acid (PLA) as a principal constituent and natural biodegradable fibres (peels of lemon, sweet lime, potato and onion). The project is aimed to build the laminate structure model with the substrate as PLA reinforced with natural fibres using ANSYS Workbench. The simulation test was carried out with various parameters: single impact, uniform pressure, sphere of influence energy absorption. Natural fibre composites were built with a volume fraction of 10%, 20% and 30% of PLA to arrive at optimum results. The computation analysis was carried out using explicit dynamic analysis as a solver and a model of impact analyser was built-in design modeller that is available in ANSYS Workbench. The simulation results are considered for further experimental testing as future work with analytical calculations referred to in ASTM D7136.

Effect of Reinforcement in Energy Absorption Characteristics of Honeycomb Structures Under Blast Loading

During recent decades demand for cellular structures has increased due to raised concern for protection of important buildings and components from blast loads. These types of cellular materials possess important features that includes less weight, higher energy absorption capabilities, higher strength to weight ratio in comparison with monolithic counterpart. Cellular material includes honeycomb, corrugated, web type structure, open and closed cell metal foam etc. However, in the present investigation, honeycomb sandwich panel are rein forced and are analysed for blast response mitigation. Further, obtained response of reinforced honeycomb structure is compared with the conventional honeycomb sandwich panel on the basis of mass. The Finite Element (FE) software LS-DYNA®, commonly used for dynamic explicit analysis, is used for numerical simulation and blast response investigation. Total three different reinforced configurations are developed and compared with conventional honeycomb i.e. honeycomb without any reinforcement. From FE analysis, it is noticed that reinforcing the honeycomb structure enhances the energy absorption capabilities significantly due to reinforcement which in turns increases the density of honeycombs.

Plastic Deformation of High Explosive Projectile 155 mm during Gun Launch Conditions using Finite Element Method

The structural integrity of artillery projectile 155mm high explosive Extended Range Full Bore (ERFB)boat tail designed for 155mm howitzer guns of 39, 45 and 52 calibre plays a key role inside the gun barrel. Thisprojectile comprises a shell body, a driving band, a boat tail, nubs, an explosive, and a fuze. Plastic deformationof the projectile and stripping of driving band are not permitted, when projectile is fired. An investigational study is necessitated to check the plastic deformation of the projectile subjected to maximum propellant charge pressure.The aim of this study is to check the effective plastic deformation and affirm the structural integrity. A 3-D explicit dynamic structural analysis of 155 mm HE ERFB BT during gun launch conditions is carried out by finite element method using FE code ABAQUS/Explicit. To understand the non-linear mechanical behavior of the projectile, the true stress-strain curves of the materials are considered. The plastic behavior of the projectile subjected to the time-dependent loading is studied by using the von Mises plasticity model. The results reveal that the shell body and boat tail have no plastic deformation and the most stressed component is the driving band. The investigation has affirmed the structural integrity of the projectile during gun launch conditions.

Experimental and Numerical Study on Steel Fiber Concrete under Blast Loading

In this paper, 30 SFRC (Steel Fiber Reinforced Concrete) spindle specimens with different steel fiber contents were subjected to static loading tests and blast wave loading tests on spindle specimens with different steel fiber contents using a self-developed planar blast wave loading device (a new type of patent recognized by the State Intellectual Property Rights). The dynamic response, impact performance and damage mode of Steel Fiber Reinforced Concrete under blast loading were investigated. The experimental results show that with the increase of steel fiber content (within 2%), the strength of the Steel Fiber Reinforced Concrete increases slightly. The flatter the falling section of the stress-strain curve, the better the energy absorption effect. With the increase of explosive equivalent(24 g RDX and 36 g RDX), the more obvious the strain rate effect, the greater the increase of peak stress, and the SFRC with 2% steel fiber content has the best energy absorption effect. Furthermore, the dynamic response of SFRC spindle specimens was numerically simulated using the improved K&C material model with LS-DYNA explicit finite element dynamic analysis software. The results verify the validity and reliability of the improved K&C material model.

FE mesh density influence on blast loading analysis

To examine the influence of mesh density on the blast loads of anti-landmines (ALMs) and improvised explosive devices (IEDs) under an armored vehicle, models with different FE mesh densities were numerically analysed. The multi-material arbitrary Lagrangian-Eulerian (MM-ALE) algorithm was used to simulate under armored vehicle explosions. Explicit dynamic analysis was performed in LS-DYNA. Blast loading simulation was performed using the ConWep (conventional weapon) loading model, which is implemented in LS-DYNA. The material characteristics of high-strength steel were used to model the protective plates on the armored vehicle. Protective plates were modeled in a V-shape and as a deformable solid with the Johnson-Cook plasticity model. In this paper, the FE model with different mesh densities was numerically tested to analyse the influence of mesh density on the obtained results. For the purposes of the modeling, different types of finite elements were used for the FE models. The floor of the vehicle was modeled with 3D hexahedral eight-noded finite elements, and the protective plates were modeled with four-noded plate finite elements. The maximal value of plastic strain and the maximal value of the displacement of the central node on the protective plate was chosen as the parameters to compare the obtained results.

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.

Sizing and Analysis of a Lift-Plus-Cruise Aircraft with Electrified Propulsion

This paper demonstrates an integrated approach to the sizing and analysis of all-electric, hybrid-electric, and turboelectric variants of a lift-plus-cruise urban air mobility vertical takeoff and landing concept using the Parametric Energy-based Aircraft Configuration Evaluator. In lieu of assuming a point mass performance model, the aircraft is trimmed explicitly for nominal and off-nominal flight conditions for sizing propulsion system components and evaluating mission energy usage. In lieu of using historical tail volume ratio guidelines for stabilizer sizing, an explicit dynamic stability analysis is incorporated to determine the stabilizer size that achieves specified bare airframe handling qualities targets. The effects of varying battery specific energy, C-rate, wing loading, hover disk loading, mission range, and cruise speed on the sizing of the three propulsion architectures are explored. A comparison of the weight breakdown of the three propulsion variants when sized to the same maximum takeoff mass is presented. The sensitivity of the sizing results to the requirement of full vs reduced payload capability at high, hot hover conditions is also assessed. In addition to being insightful, the presented results reinforce the need to incorporate more physics-based analyses, additional stability and control considerations, and configuration optimization studies, which form natural avenues for follow-on work.

A dynamic fracture finite element model of the buried gas transmission pipeline combining soil constraints and gas decompression

A long-distance natural gas transmission pipeline is the primary solution for natural gas resource distribution. In fact, the longitudinal crack propagation of gas transmission pipelines has always been a concern of the natural gas industry. Because it will cause disastrous accidents once the ductile crack in the pipeline propagates rapidly. Most natural gas transmission pipelines are buried underground to improve the safety of pipeline operation as the backfill soil can absorb energy during the fracture process and restrain the displacements of the flaps. Fracture control is a fundamental requirement for the safe operation of underground pipelines. In this study, the dynamic fracture finite element model of the buried gas pipeline is developed to simulate the actual fracture process instead of the costly full-scale burst experiments. The finite element model incorporates different external soil constraints and internal gas decompression behaviors during pipe rupture in which soil constraints are represented by discrete soil springs, and a user-defined subroutine realizes the gas decompression behavior. The explicit dynamic analysis is employed to simulate the high-speed dynamic fracture process of the pipeline, and the crack propagation is simulated by using the cohesive zone model. Finally, the crack propagation velocity is calculated by this model, and the influence of different internal pressures on the fracture velocity is studied; the crack tip opening angle (CTOA) is predicted, and the effect of soil spring stiffness on CTOA is evaluated.

Numerical simulation on dynamic response of prefabricated concrete pier under vehicle collision

To study the impact resistance of the prefabricated concrete pier under the action of vehicle collision, a finite element model was established by ABAQUS. The concrete damaged plasticity model was used to simulate the nonlinear behavior of the concrete, and the strain rate effect on the material’s dynamic strength was considered. Based on the explicit dynamic analysis method, the dynamic response analysis of the prefabricated bridge pier under the action of vehicle impact was carried out. The differences in impact force, residual displacement and concrete damage between the prefabricated pier and cast-in-place pier were analyzed. Finally, the parameter study was carried out. The results show that compared with the cast-in-place pier, the concrete damage degree of the prefabricated pier is lower under the vehicle impact, and the residual displacement is larger due to the slip at the segment joint. The final stresses in the prestressed tendons increase compared with the initial state, the stress of the prestressed tendon far away from the collision side increases significantly during the impact process. The size of mortise and tenon has effect on the horizontal stiffness of the prefabricated pier. Increasing the initial prestress level has little effect on the concrete damage, but it can improve the integrity of the prefabricated pier.

Influence of honeycomb core height on the blast mitigation performance of sandwich panel

Explosive attacks are a major terrorist threat that is increasing day by day. Honeycomb sandwich panels have a high capacity to absorb energy under blast loads and are very popular for protective structures against blast. Honeycomb sandwich panels are designed with various design parameters. The investigation of the blast mitigation performance of the sandwich panels through experiments is very costly as well as a hazard for both the environment and people. However, in this present work, the blast performance of the square honeycomb sandwich panels (SHSPs) was investigated numerically by dynamic explicit analysis using ABAQUS 6.14. The SHSPs with equal or unequal mass were modelled with 51 mm, 61 mm, and 71 mm core heights to analyse their effects on the face sheet deflection and energy absorption. The blast resistance characterization was carried out at 1 kg to 3 kg of trinitrotoluene (TNT) explosion for a 0.1 m stand-off distance after the mesh convergence and validation study. The simulation results show that increasing the core height improved blast resistance by reducing back face deflection and increasing energy absorption by the core. The SHSPs with a 71 mm core height outperform the other modelled sandwich panels and can be utilized for armoured applications.

RESEARCH ON DAMAGE CHARACTERISTICS AND PROTECTIVE STRUCTURE DESIGN OF STEEL PONTOONS UNDER NEAR-FIELD EXPLOSION LOAD

The focus of this paper is to investigate the damage characteristics and protective structure design of pontoons as an important barrier for the protection of ports. Two types of protective measures of pontoons are investigated：filling tanks with water and installing springs in tanks. In this paper, the damage characteristics of two types of pontoon side structures under the action of near-field explosion loads are simulated by using LS-DYNA explicit dynamic analysis software and the ALE algorithm. According to the numerical experiment results for filling different volumes of water in the side tanks, the volume of water for the minimum deformation of the shell plate is 100%, and for the first longitudinal bulkhead, it is 30-40%. Moreover, by applying weights to their deformations based on the actual explosion-proof performance requirements of the shell plate and the first longitudinal bulkhead, the pontoon side structure with the best explosion-proof performance can be obtained. The plastic deformation of the pontoon structure equipped with different types of springs is an order of magnitude smaller than that of the ordinary structure and of the pontoon structure filled with a water medium in the positive tanks. The explosive shock wave energy absorbed by the pontoon is effectively reduced by the addition of water or springs to the protective tanks. The minimum energy absorbed by the pontoon structure with water added in the protective tanks is 18.31% of the energy absorbed by the ordinary structure, and the corresponding volume ratio of water added in the protective tanks is 100%. The pontoon structure with springs in the side protection tanks absorbs only 7.2% of the energy absorbed by the ordinary structure. Both new side protection structures have demonstrated excellent explosion-proof performance.

FEA-based Design and Analysis of Spur Gear

Most mechanical devices contain gears as one of their basic component. Spur gears are a type of gear that is often used to transfer power between two parallel shafts. Spur gears have a parallel gear cut to the shaft axis. The design of gear has a direct impact on the efficiency of the transmission. As a result, the significance of proper gear design and testing is of the highest importance in modern machines. Simulation has recently gained popularity as a cost-effective alternative to laboratory testing. Explicit Dynamic, Static Structural and Modal Analysis performed on Spur Gear in this project to illustrate the gear's reaction to different boundary conditions. As a simulation tool, ANSYS workbench is utilized.

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.

Analysis of polypropylene material and hybrid bio mixtures for automotive applications

The car door is typically made of steel, with an internal and external panel that also serves as a mounting plate for the various connections. However, doors are among the most appealing vehicle parts for light weighting: the ability to reduce absolute weight with two or four entrances is critical. The objective of this work is to reduce the weight of car doors by using Natural Fibers (NF) such as Kenaf fiber (KF), Prosopis juliflora bark (PJb) and Jute fiber (JF) fortified polyester mixtures for modelling and simulation. These models are compared with existing polypropylene material. In this study, the car door has modelled through Solid works. Afterward, the various impact attributes of automobile car door panel for mixture material and polypropylene material at different speeds are performed using Ansys Explicit Dynamic Analysis. The analysis results of NF reveal the enhanced total deformation and equivalent strain by about 20.14%, 27.78%, 85.9%, and 68.9% respectively for the velocities of 60 and 72kmph compared with polypropylene material. The NF composite helps to absorb more stress and strain, preventing damage to the vehicle body as well as the passengers.