Rigid Impact Research Articles

Biofidelity and Limitations of Instrumented Mouthguard Systems for Assessment of Rigid Body Head Kinematics.

Instrumented mouthguard systems (iMGs) are commonly used to study rigid body head kinematics across a variety of athletic environments. Previous work has found good fidelity for iMGs rigidly fixed to anthropomorphic test device (ATD) headforms when compared to reference systems, but few validation studies have focused on iMG performance in human cadaver heads. Here, we examine the performance of two boil-and-bite style iMGs in helmeted cadaver heads. Three unembalmed human cadaver heads were fitted with two instrumented boil-and-bite mouthguards [Prevent Biometrics and Diversified Technical Systems (DTS)] per manufacturer instructions. Reference sensors were rigidly fixed to each specimen. Specimens were fitted with a Riddell SpeedFlex American football helmet and impacted with a rigid impactor at three velocities and locations. All impact kinematics were compared at the head center of gravity. The Prevent iMG performed comparably to the reference system up to ~ 60g in linear acceleration, but overall had poor correlation (CCC = 0.39). Prevent iMG angular velocity and BrIC generally well correlated with the reference, while underestimating HIC and overestimating HIC duration. The DTS iMG consistently overestimated the reference across all measures, with linear acceleration error ranging from 10 to 66%, and angular acceleration errors greater than 300%. Neither iMG demonstrated consistent agreement with the reference system. While iMG validation efforts have utilized ATD testing, this study highlights the need for cadaver testing and validation of devices intended for use in-vivo, particularly when considering realistic (non-idealized) sensor-skull coupling, when accounting for interactions with the mandible and when subject-specific anatomy may affect device performance.

Quasi-static uniaxial compression and low-velocity impact properties of composite auxetic CorTube structure

Auxetic structures are gaining great attention due to their unique contraction deformation characteristics under compression and impact. In this paper, high performance carbon fiber-reinforced composites are used to fabricate the auxetic structure consist of corrugated sheets and tubes (CorTube). The quasi-static uniaxial compression and low-velocity impact properties of composite CorTube structure are explored. The response of the composite CorTube structures under quasi-static compression loads are analyze through a combination of theoretical analysis, simulations, and experimental tests. Additionally, drop-weight impact tests are conducted using a rigid impactor with a hemispherical head to examine the effects of impact energy levels, impact locations, and corrugated sheet thickness on the impact response of CorTube structure. Enhancing corrugated sheet-tube bonding via modified cross members and reducing tube crushing during quasi-static compression are notable findings. The results also highlight the remarkable auxetic properties of the composite CorTube under low-speed impact, and the impact resistance could be enhanced by increasing the corrugated sheet thickness and stiffness. Various failure modes were observed, including cracks, pits, tube crushing, and delamination. Significantly, peak-impacted specimens exhibited greater maximum displacement with lower peak impact forces. This study offers insights into the deformation and failure modes of auxetic CorTube structures under low-velocity impact.

Low-velocity impact behaviors of sandwich composites with different structural configurations of foam core: numerical study and experimental validation

Sandwich composites have very weak properties as well as superior properties. Damages will be invisible and may create huge problems due to the high strength difference of composite components. To investigate sandwich composites, numerical studies’ importance is so high because experimental studies require high labor and are time-consuming. In this study, low-velocity impact properties of the configurations of sandwich composites with E-glass fiber/epoxy and PVC foam core are investigated numerically, and the results are compared with experimental results. Reference sandwich composite, and four different types of configurations are modeled with homogenized properties. Numerical simulations are performed using the material models of rigid impactor, foam core, and composite material models of LS-DYNA software. Numerical and experimental results of these sandwich composites are compared in terms of contact force-time and contact force-displacement curves, core/facesheet debonding areas, peak contact forces, absorbed energy, maximum displacement, and contact time; a good agreement is obtained.

Studying the Properties of Metamaterials with a Negative Poisson’s Ratio when Punched by a Rigid Impactor

Studying the Properties of Metamaterials with a Negative Poisson’s Ratio when Punched by a Rigid Impactor

Studying the Properties of Metamaterials with a Negative Poisson’s Ratio when Punched by a Rigid Impactor

Some properties of metamaterials with a negative Poisson’s ratio (auxetics) have been studied experimentally when punched along the normal by a rigid spherical impactor. Samples of a metamaterial with a chiral structure (hexachirals honeycomb) are made of e-PLA plastic using a 3D printer. In experiments, a deviation of the direction of movement of the impactor after leaving the punched sample from the approach direction (normal to the side surface) is observed. The dependence of the impactor projection direction on the orientation of the elements of chiral symmetry of the samples is established. A FE model for calculating the penetration of a chiral structure has been developed. Numerical results are presented and their agreement with experimental data is noted.

Damage and energy absorption behaviour of composite laminates under impact loading using different impactor geometries

The present paper compares the damage and energy absorption behaviour of composites subjected to low-velocity impact using different frontal geometries for the impactor, with the composites possessing a layup of [02/902]2s. In this study, the rigid impactors with either round-nosed or flat-ended frontal geometry are employed to perform drop-weight tests at various impact energies ranging from 10 to 30 J. The measured loading response and energy absorption are analysed and compared. Additionally, the types and extent of impact-induced damage in the composite specimens are assessed via ultrasonic C-scan, optical microscopy (OM) and scanning electron microscopy (SEM) studies. It is shown that the impact energy threshold for damage initiation is greater than 20 J when using the flat-ended impactor but is less than 10 J when using the round-nosed impactor. In both cases, delamination initiates between the plies in the composite laminate. However, for the flat-ended impactor, the damage behaviour of the fibres exhibits kinking fracture, which differs from the pull-out fibre-fracture caused by the round-nosed impactor. These differences in behaviour are attributed to impactor/composite contact geometry effects which leads to different extents of indentation damage, which in turn directly affects the degree of delamination and fibre damage in the composite.

A simplified method to assess the elasto-plastic response of standalone tubular Offshore Wind Turbine supports subjected to ship impact

This paper presents a simplified analytical approach to rapidly simulate the elasto-plastic response of standalone tubular Offshore Wind Turbine (OWT) supports (e.g. monopiles and spar floating platforms) that are subjected to a ship collision. The wind turbine, idealized as a constant cross-section cantilever tube with a tip mass, is assumed to be struck by a rigid impactor. In a first step, a series of preliminary finite element simulations enable the identification of three successive phases in the deformation process: (i) local elastic denting, (ii) local plastic denting combined with global elastic bending, and (iii) plastic buckling at the base of the structure. In a second step, from these observations, existing analytical formulations extracted from the literature are integrated into a time-stepping algorithm. Finally, resulting force-penetration and energy balance curves are compared to finite element results. Simulations are performed considering mid and quarter-length impacts of a 6000-tonnes Offshore Supply Vessel approaching at different velocities. Seven different OWTs are tested. A good correlation between analytical predictions and numerical simulations is found in the vast majority of the investigated collision scenarios. Limitations are encountered for stockier supports, where the contribution of the global elastic bending mode is underestimated by the proposed analytical model. Overall, the method presents a promising alternative for risk assessment and structural optimization applications.

Numerical simulation of axially impacted elastic bar

This numerical analysis considers a model of an elastic cylindrical bar impacted by rigid mass, where the accuracy of the model is benchmarked by a closed-form solution developed for this impact process. The analytical solution provides theoretical background and understanding, however, practical problem is not always restricted to a simple one-dimensional geometry and boundary conditions of a purely elastic material behaviour. Hence, the current work numerically simulates the impacted elastic bar, then explores parameters which are not considered in its theoretical model. A two-dimensional (2D) solid axisymmetric system is considered, in which rigid impactor is assigned with initial velocity corresponding to certain drop height and a 2D contact type is defined between interacting bodies. Both elastic and time-dependent viscoelastic material models are considered in this study. The simulation results reveal time intervals gradually increase in every sequential intervals, while relatively small discrepancies are recorded for peak load and pulse width outputs. The parameters of impactor’s mass, drop height and structural stiffness are varied; showing how these parameters individually affect the resulting force response at end struck. The models then evaluate time-dependent viscoelastic material model; showing stiffer response of the resulting force in comparison to models assigned with long-term elastic moduli. Derived elastic modulus-output variable relations show comparable mathematical forms to corresponding equations formulated analytically.

Peridynamic Modeling of Compression After Impact Damage in Composite Laminates

This study presents a peridynamic (PD) simulation of compression-after-impact (CAI) of a laminate in two subsequent stages of impact and compressive type of loading. In the first stage, a transient analysis is performed that simulates the motion of a rigid impactor hitting a laminate resulting in matrix and delamination damage. After the impactor rebounds and the transient effects due to impact die out, the simulation continues for additional time steps under compressive in-plane loading resulting in further damage and eventual structural failure of the laminate. The PD simulations effectively capture the deformation fields and damage patterns due to impact and subsequent compressive loading until failure. The predictions are consistent with the experimentally observed damage patterns due to impact and subsequent compressive failure load.

Dynamics of stochastically excited energy harvesting systems with impact

Focusing on rigid impact (RI) and elastic impact (EI) vibratory energy harvesting systems with the excitation of Gaussian white noise, the stochastic response characteristics, and energy harvesting performance of the systems are presented and compared. The stochastic averaging of the energy envelope is introduced with different processing methods in these systems to derive the theoretical probability density functions. Numerical simulation results verify the effectiveness of such theoretical methods. Effects of the coefficients and positions of impact barriers in the systems on the mean square voltage are analyzed. The analysis can help explain the physical mechanisms of the systems and provide ideas for optimizing energy harvesting performance by properly tuning the coefficients. Effects of the existence of three kinds of impact on the output energy are explored and compared. It is found that the existence of EI can help to enhance the energy harvesting performance of the system in most cases, and setting the impact barrier at the origin is more conducive to harvesting energy compared with other impact positions.

Numerical Study on Shear Studded Tubed Steel Reinforced Concrete Columns Under Impact Loads

Tubed steel reinforced concrete (TSRC) columns are the advanced version of steel reinforced concrete column (SRC) which consists of inner and outer confinement along with the concrete core. In this composite member, a structural steel member and the outer confinement provides inner confinement as well as outer confinement. During recent years, TSRC sections got wide attention mainly because of its advantages over common CFST sections. Main advantage is that it simplifies the construction of beam-column joints and spalling of concrete during an event of earthquake can be avoided as outer steel confinement is provided. Many studies are done to check the performance of these TSRC columns in different loading scenarios. During the initial stages behavior under axial and eccentric loading was done on this section by different researchers and tried to develop analytic formulas and equations for TSRC columns. In this era of time it is necessary to check the ability of structures under impact loads. This study aims to investigate the performance of TSRC columns under impact loading condition and concluded. For the finite element analysis LS-Dyna software is adopted and for modelling purpose Hypermesh software is used. In this study, first validation is done by applying axial load vertically to the tubed steel reinforced concrete column. For the application of axial load rigid impactor plate is used. Impact force is applied to the TSRC short column in two directions: vertical, horizontal. For providing vertical impact a rigid plate impactor is used and for horizontal impact a dogde neon vehicle is used. Here in this analysis shear studs are incorporated on the surface of flanges of the inside steel section.

Parametric study on impact behaviour of sisal and cenosphere reinforced natural rubber-based hybrid composites: FE approach

This paper aims to study the impact analysis of sisal fiber and cenosphere filler reinforced natural rubber composite using commercially available finite element software. The proposed green composite is studied for impact behaviour by varying the weight percentage of the cenosphere filler particles in a natural rubber sheet. Composite is modelled with stacking sequence sisal-rubber-sisal using finite element software and impacted by three different rigid impactors (Conical, Hemi-spherical and Flat) at the velocity of 8 m/s. Modelling and simulation of this proposed composite laminate are solved using the explicit dynamic solver of Abaqus Computer-Aided Engineering Finite Element Modelling. The results of the low-velocity impact of the proposed green composite with sisal-rubber-sisal stacking sequence exhibit better energy absorption by varying the weight percentage of the Cenosphere. Also, the energy absorbed by laminate was more for the Conical impactor than the Hemi-spherical and Flat impactors and the extent of damage is more when impacted by the Flat impactor due to its larger contact area.

Experimental and numerical studies on the impact resistance of large-scale liquefied natural gas (LNG) storage outer tank against the accidental missile

Regarding the disastrous consequences when the dome or cylindric wall of Liquefied Natural Gas (LNG) was damaged, the large-scale LNG storage tank should be designed to resist the potential impact loadings, e.g., turbine and wind-borne missiles. This paper aims to study the impact resistance of large-scale LNG storage outer tank subjected to the accidental low-velocity and large weight missile experimentally and numerically. Firstly, the reinforced concrete/steel liner (RC/steel) composite targets designed according to the dome of LNG storage tank were fabricated. Fifteen free dropping tests of rigid impactor on the RC/steel targets were conducted, in which the mass of the impactor were 500 kg, 800 kg and 1100 kg, and the corresponding impacting velocities were ranged from 14 m/s to 26.19 m/s, respectively. The local damage and failure modes of RC/steel target panels under large caliber hard projectile impact are assessed experimentally. Then, the commercial finite element (FE) program LS-DYNA was utilized to perform the corresponding numerical simulations, the numerical algorithm, constitutive models and the corresponding parameters are validated by comparing with the test data. Finally, the impact resistance of the prototype of Chinese Dalian large LNG storage outer tank subjected to the accidental impact of missiles specified by British standard BS 7777 and United States regulatory guide U.S. 1.76 are evaluated numerically. The present work and conclusions can provide helpful references for the design and impact resistance evaluation of large-scale LNG storage tank subjected to the accidental missile.

The Biomechanics of Indirect Traumatic Optic Neuropathy Using a Computational Head Model With a Biofidelic Orbit.

Indirect traumatic optic neuropathy (ITON) is an injury to the optic nerve due to head trauma and usually results in partial or complete loss of vision. In order to advance a mechanistic understanding of the injury to the optic nerve, we developed a head model with a biofidelic orbit. Head impacts were simulated under controlled conditions of impactor velocity. The locations of impact were varied to include frontal, lateral, and posterior parts of the head. Impact studies were conducted using two types of impactors that differed in their rigidity relative to the skull. The simulated results from both the impactors suggest that forehead impacts are those to which the optic nerve is most vulnerable. The mode and location of optic nerve injury is significantly different between the impacting conditions. Simulated results using a relatively rigid impactor (metal cylinder) suggest optic nerve injury initiates at the location of the intracranial end of the optic canal and spreads to the regions of the optic nerve in the vicinity of the optic canal. In this case, the deformation of the skull at the optic canal, resulting in deformation of the optic nerve, was the primary mode of injury. On the other hand, simulated results using a relatively compliant impactor (soccer ball) suggest that primary mode of injury comes from the brain tugging upon the optic nerve (from where it is affixed to the intracranial end of the optic canal) during coup countercoup motion of the brain. This study represents the first published effort to employ a biofidelic simulation of the full length of the optic nerve in which the orbit is integrated within the whole head.

Effect of taper angle on crashworthiness performance in hybrid tubes

The present paper dealt with the finite element analysis (FE) analyzing the taper angle design of aluminum/E-glass fiber reinforced polymer hybrid tubes. This study investigated the crushing characteristics involving peak crush force (PCF), crush force efficiency (CFE) and specific energy absorption (SEA) capacity of thirty different configurations of hybrid tubes. Three types of geometries were studied numerically, including circular, square and hexagonal. The structures evaluated included circular hybrid tubes fabricated with aluminum alloy and composite. The hybrid structures were subjected to axial impact loads using a 750-kg rigid impactor with an initial velocity of 15 m/s. It was found that the crashworthiness performance increased with increasing taper angle. The SEA and CFE values of the circular hybrid tube with a 10° taper angle were high in the other square and hexagonal hybrid tubes. That hybrid structure can preferable as impact energy absorber due to the ability to withstand axial impact loads effectively.

Low velocity impact analysis of high-order rectangular FG-CNTRC plates using the weak form QEM

The functionally graded carbon nanotubes reinforced composites (FG-CNTRC) plates have excellent properties and broad application prospects. In the analysis of low velocity impact response of functionally graded carbon nanotubes reinforced composite plates, innovative numerical formulations are urgently needed. As a new high-order numerical method, the weak form quadrature element method (QEM) has its unique advantages and has been widely used in the engineering structural field. In this paper, the nonlinear Hertzian contact law is employed to describe the impact process between a rigid impactor and the rectangular FG-CNTRC plate, that was modelled with the Reddy’s high-order shear deformation theory. By using the weak form QEM, the calculation model for the impact system is established, and the numerical solution is carried out with the help of Newmark-β step-by-step time domain integration method and Newton-Raphson iteration technology. The effectiveness and accuracy of the weak form QEM formulation were verified through the comparison with the existing literature and the relevant low velocity impact properties of FG-CNTRC plate are explored.

ОЦЕНКА КОНТАКТНЫХ НАПРЯЖЕНИЙ ПРИ ВНЕДРЕНИИ УДАРНИКА В ПРОЧНЫЙ ГРУНТ

Finite formulas have been derived for evaluating contact stresses in a rigid impactor penetrating a soil, taking into account the friction in the framework of the local interaction model. In analyzing dynamic deformation of the soil, its volumetric compressibility, shear resistance and initial strength are accounted for. The obtained evaluations of resistance to penetration of an impactor into the soil are based on a quadratic relation between the stress normal to the impactor surface and impact velocity. The authors have pioneered in deriving finite expressions for coefficients of a trinomial approximation as a function of experimentally determined physical-mechanical parameters of the soil - a dynamic compressibility diagram (a shock adiabat) and a yield strength - pressure diagram. Impact compressibility of soils is described based on Hugoniot's adiabat - a linear relation between shock wave velocity and mass velocity of the medium particles behind the shockwave front. Plastic deformation obeys the Mohr - Coulomb yield criterion with a constraint on the limiting value of maximal tangential stresses according to Tresca's criterion - the Mohr - Coulomb - Tresca plasticity condition. An earlier obtained analytical solution of a one-dimensional problem of a spherical cavity expanding at a constant velocity from a point in a half-space occupied by a plastic soil medium is used. A formula for determining critical pressure (a minimal pressure required for the formation of a cavity, accounting for internal pressure in the framework of Mohr - Coulomb's yield criterion) is also used, which generalizes a known solution for an elastic ideally plastic medium with Tresca's criterion. The derived formulas have been verified by comparing their results with the available data from experiments on the penetration of a steel conical impactor into a frozen sandy soil. It is shown that the disagreement between the numerical and experimental results is within 10%.

Surface deformation and rebound for normal single-particle collisions in a surrounding fluid

This article presents experimental measurements involving immersed collisions between a rigid impactor and a deformable target for a wide range of Reynolds and Stokes numbers. Three aluminium alloys are used as solid targets submerged in seven different fluids covering a wide range of viscosity and density. The collision and rebound velocities as well as the depth and diameter of the crater produced by the collisions are measured with high resolution. Most of the experiments in this study occur at velocities for which the deformation is within the elastic–plastic regime. Results of the experiments in air are analysed by elastic, plastic and elastic–plastic theories, and demonstrate the complexities of modelling elastic–plastic collisions. For collisions in a liquid, the measurements show that the size of the crater is independent of the fluid characteristics if the Stokes number is beyond a critical value. The normal coefficient of restitution can be estimated by including both viscous losses and plasticity effects and assuming that the collision time scale is significantly shorter than the hydrodynamic time scale. The results of the crater dimensions are also used to develop an analytical expression for the volume of deformation of the material as a function of material properties and the impact and critical Stokes numbers.

Dynamic analysis of cold-formed steel channel-section columns under axial impact loading

In this paper we present an investigation of the impact of cold-formed steel channel section columns when subjected to an axial impact by a rigid impactor. The work involves both the numerical simulations and experimental tests. The former was done by using nonlinear finite element analysis method and the latter was done by using drop hammer tests. In the present finite element analysis, material nonlinearity, strain rate effect, initial geometric imperfection, and interactions between the impactor and column are considered. It is shown that the impact deformation of the channel-section column under the axial impact of rigid impactor can be characterized initially by its axially compressive deformation, followed by the localized bending deformation in the region where the geometric imperfection is large. The validation of the numerical results using the drop hammer test results demonstrates the appropriateness of the numerical model developed in the paper.

Modeling And Simulation On Composite Laminates Subjected To Low Velocity Impact

Composite laminates are very much susceptible to low velocity impacts. The elastic behaviour of the fiber-reinforced plastics is studied in this paper. A numerical analysis of dynamic low-velocity impacts is performed on E-Glass/Epoxy and Carbon/Epoxy using Abaqus software. An 18 ply finite element model with dimensions 180×50×7mm is formulated. A hemispherical nosed rigid impactor with a 24mm diameter is modelled for low-velocity impacts. The impact response of the composite laminates is examined for different velocities [3], [6], [9]m/s, for impactor mass(mi) to composite plate mass(mp) ratios [0.5,1,4] and with two different stacking sequences [0/-45/45/0/90/0/45/-45/0]s and [0/45/90/45/0/-45/90/-45/0]s. The contact forces between the impactor and composite plate, energy absorption of the plate and deflections for the above mentioned conditions are presented. Further, the behaviour of the composite plate is analysed at same impact energy by changing the mass and velocity of the impactor.