Cylindrical Impactor Research Articles

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ПРОНИКАНИЯ ЦИЛИНДРИЧЕСКИХ УДАРНИКОВ В СУХОЙ ПЕСОК

For the most complete study of the laws of shock interaction of solids with soil barriers, further development of experimental techniques for recording the parameters of the interaction process in direct and inverse experiments is necessary. In this work, to determine the parameters of the movement of the projectile (displacement and speed) in a direct experiment, a millimeter-wave radio interferometer is used. This method allows continuous recording of the movement of the rear end of the striker with high accuracy over a wide range of movements. Using the proposed technique, experiments were carried out to record the motion parameters of cylindrical impactors made of steel and aluminum alloy when interacting with an obstacle made of dry sand. At the same time, the movement of the rear end of the striker was also controlled using high-speed filming until the full immersion of the striker. The experiments showed that the measurement results obtained using two methods coincide within the measurement error. Based on the experiments, it can be concluded that the methodology for determining the displacement and velocity of a projectile in a ballistic experiment using a millimeter-wave radio interferometer allows continuous measurement of large displacements (100 mm or more), including when completely immersed in a target with sufficient practical goals accuracy. Based on the results of the experiments, the dependences of the movement of the projectile and its speed on time are constructed. A change in the penetration law was found with a decrease in the penetration velocity to values less than 100 m/s.

Optimizing Weight Percentage of MWCNTs for Enhancing LVI Resistance of Quasi-Isotropic Symmetric Laminate of Carbon Woven Fabric/ Epoxy Embedded with MWCNTs

This research work investigates the energy absorption, and damage tolerance behavior of three phased (carbon woven/epoxy/multiwall carbon nanotubes) polymer composites. Five doping weight fractions of multi-wall carbon nanotubes (MWCNTs) are considered as 0, 1, 2, 3 and 4 wt.% of thermosetting epoxy resins. Low-velocity impact (LVI) tests are conducted on drop tower setup with three different velocities, 3.5, 4.5 and 5.5 m/s. Damage caused by a 10 kg, hemispherical headed cylindrical impactor is analyzed and compared. The experimental results showed an increase in the energy absorption up to 3 wt.% of the MWCNT doping. However, reinforcing above this percentage, the energy absorption is reduced due to the formation of MWCNT agglomerations. Therefore, this work proposed an optimized doping percentage for CFRP laminates. The maximum improvement of 51.83% in energy absorption was found at 3 wt.% of MWCNT reinforcement in epoxy resins.

Basalt Fibres in Vinyl Ester Resin Laminates Under Low Velocity Impact Conditions

A study was conducted to investigate the impact strength of basalt fibres in vinyl ester resin, a composite laminate material used for the design of marine vessels. The basalt/vinyl ester laminate material was dynamically loaded with a Ceast/Instron falling weight machine, using a 3.6 kg cylindrical impactor with a 19.8 mm diameter hemispherical nose. Impact tests were conducted at various energy levels—up to complete penetration—to obtain the full load–displacement curve, identify the material’s penetration energy, and investigate damage initiation and propagation. After the impact tests, the internal damage of each specimen was evaluated using the non-destructive Ultra Sound technique.

Effects of the impactor geometrical shape on the non-linear low-velocity impact response of sandwich plate with CNTRC face sheets

In this study, non-linear low-velocity impact response of a simply supported sandwich plate with CNTRC face sheets subjected to the impactors with different geometrical shapes is investigated. It has been assumed that the sandwich plate is made up of two face sheets reinforced with CNTs graded along their thickness as X profile and a homogeneous core. In CNT-reinforced layers, a micromechanical model has been used to obtain the effective material properties and the analysis is performed in the framework of the Reddy's higher order shear deformation theory with regard to thermal effects. An analytical model is proposed to capture the response performance of the three-layer sandwich plates under different thermal environments. Through the proposed analytical study, in order to characterize the contact force between the sandwich plate and the impactors, the modified Hertz contact law is utilized. Rayleigh-Ritz method is applied to the Hamilton principle in order to find the set of equations of motion for the impactor as well as the CNTRC sandwich plate. Afterwards, the solution in the time domain is obtained based on Newmark's numerical time integration scheme. After validating the proposed approach, in order to examine the influences of various involved parameters, different parametric studies are conducted. It has been demonstrated that the variation of the initial kinetic energy as one of the parameters under study has a significant effect on the central displacement, contact force, and indentation in both conical and cylindrical impactors and the change in the radius of the cylinder has an insignificant effect on the central displacement. As well, in the case of equal masses, the cylindrical impactor causes more amount of indentation with respect to conical.

The influence of pre-existing rib fractures on Global Human Body Models Consortium thorax response in frontal and oblique impact

Many post-mortem human subjects (PMHS) considered for use in biomechanical impact tests have pre-existing rib fractures (PERFs), usually resulting from cardiopulmonary resuscitation. These specimens are typically excluded from impact studies with the assumption that the fractures will alter the thoracic response to loading. We previously used the Global Human Body Models Consortium 50th percentile whole-body finite element model (GHBMC M50-O) to demonstrate that up to three lateral or bilateral PERFs do not meaningfully influence the response of the GHBMC thorax to lateral loading. This current study used the GHBMC M50-O to explore the influence of PERFs on thorax response in frontal and oblique loading. Up to six PERFs were simulated on the anterior or lateral rib regions, and the model was subjected to frontal or oblique cylindrical impactor, frontal seatbelt, or frontal seatbelt + airbag loading. Changes in thorax force-compression responses due to PERFs were generally minor, with the greatest alterations seen in models with six PERFs on one side of the ribcage. The observed changes, however, were small relative to mid-size male corridors for the loading conditions simulated. PERFs altered rib strain patterns, but the changes did not translate to changes in global thoracic response. Within the limits of model fidelity, the results suggest that PMHS with up to six PERFs may be appropriate for use in frontal or oblique impact testing.

Experimental dynamic analysis of polymer-based nanocomposite beams under low-velocity impact loading

An experimental study was performed on low-velocity impact response of nanocomposite beams reinforced with different loadings of nanoclay (0, 3, 5 or 7 wt%). Using two commercially organo-modified nanoclays (Cloisite 30B and Cloisite 15A), as well as two types of manufacturing methods (hand lay-up and vacuum assisted resin transfer molding), a set of composite/nanocomposite beam samples was prepared. To apply identical boundary conditions along the width of the beam, a cylindrical impactor was selected, whose lateral surface was in contact with the beam. The comparative results of the low-velocity impact (LVI) and quasi-static tests for the beam with 3 wt% Cloisite 30B showed that energy absorption capacity of dynamic loading and quasi-static one was equal to 20.75 and 40 J, respectively. Therefore, it was deduced that the energy absorption capacity of an LVI sample was approximately twice as much as that of a quasi-static one. In addition, the smaller after-impact damage to the beams with a higher content of nanoclay was justified as a result of the impermeable nature of nanoclays. Moreover, it was observed that addition of Cloisite 15A significantly increased the energy absorption capacity of the composite than that of the Cloisite 30B. However, increasing the weight percentage of Cloisite 15A had no significant effect on energy absorption capacity of nanocomposite. The reason of the last result has been described in the paper with a precise study of the microstructure of the materials.

Investigation of dynamic resistance to the shear of water-saturated sand according to the results of the inverse experiment technique

The results of an investigation of the shear resistance for compacted dry and water-saturated sand are presented on the basis of the experimental-calculation analysis of the drag force at the quasi-stationary penetration stage of a cylindrical impactor. We used a method proposed earlier based on the inverse experiment technique and using a measuring rod with a flat end. It is shown that with almost the complete water saturation of sand its shear properties decrease but remain significant in the practically important range of penetration rates.

Deformation behavior of single and multi-layered materials under impact loading

Finite element (FE) simulations using Abaqus/Explicit are performed to study the deformation behavior of materials under impact loading. Various configurations including monolithic and multi-layered plate having combinations of ceramic, metal and composite material layers are investigated to determine the critical failure velocity Vcf as a function of layer thickness and stacking. While cylindrical impactor is assumed to be rigid, Johnson-Cook (JC), Johnson-Holmquist (JH2) and Hashin 3D and Puck criteria is used to characterize damage/failure in metal (Al and steel), ceramic (SiC) and composite (carbon fiber/epoxy) layer respectively. Constitutive equations for composite material are supplied via user subroutine VUMAT. The results of FEM simulations reveal that Ceramic-Al-Carbon fiber/epoxy multilayer plate provides most desirable combination with higher critical failure velocity, lower average density, lower pressure and displacement at the back plate as compared to other material combinations considered in this work. Moreover, the analysis presented shows that the numerical approach developed can be used as a tool to predict the geometry and material combinations of a multilayer system to improve its resistance against impact loading.

DAMAGE MODES AND FAILURE MECHANISM OF 160,000 m3 LNG OUTER CONCRETE TANK UNDER IMPACT LOADING

In order to investigate the damage models and failure mechanism of the outer concrete tank of the liquefied natural gas (LNG) storage tank under impact loading, the finite element (FE) model of the outer concrete tank of 160,000 m3 LNG storage tank for an actual LNG project and a cylindrical impactor are established based on ANSYS/LSDYNA FE analysis software platform. Through the result comparison of the numerical simulation and an impact perforation test of reinforced concrete slabs subjected to projectile with high speed, the accuracy of the numerical simulation method and material model proposed from this paper are verified. The dynamic response of the concrete dome for LNG outer concrete tank structures under impact loading is studied. Based on response rules and failure phenomena of the dome for LNG outer concrete storage tank subject to impact loading, three damage modes are defined, and the failure mechanism for each mode is revealed from the view point of energy.

Evaluation of adaptive carbon fibre-reinforced door beams

An expandable, carbon fibre reinforced polymer (CFRP) door beam was designed, built and experimentally evaluated to improve side impact performance and reduce mass in passenger vehicles. Pressurisation and expansion of the beam was achieved using gas generator technology. The impact performance of the beam was evaluated by means of a sub system test method, mimicking vehicle-to-pole side impact. The sub system test method comprised a 3-point, bending load case, with a spring loaded sliding boundary condition at one end of the beam, while the other end was rigidly fixed. The beam was impacted by a 60 kg cylindrical impactor at 6 m/s. For the expanded and pressurised beam peak deflection was 193 mm. For the folded unpressurised beam peak deflection was 216 mm. To achieve the same impact performance with the expandable CFRP beam, as with a state of the art aluminium door beam, mass reductions seem plausible.

Numerical investigation of damage area due to different shape of impactors at low velocity impact of GFRP laminate

In this paper numerical investigation of damage area caused by different shapes of impactor is studied. Quasi-isotropic symmetric glass fiber reinforced polymer (GFRP) laminate have been used with zero bending extension coupling. Four different shape of impactors used for analysis are: (i) Hemispherical headed cylindrical impactor, (ii) Spherical impactor, (iii) Oval shaped impactor and (iv) Flat base cylindrical impactor. These impactors having mass of 5.23 kg and impact velocity 3 m/sec. FEM analysis is done using commercially available software LS-DYNA. On impacting with energy of 23.5 J, oval headed impactor lead to minimum damage area of 394.61 mm2 and form maximum fiber breakage pyramid structure on the back face of GFRP laminate. On the other hand, flat base cylindrical impactor causes no fiber damage and causes maximum damage area of 1211.27 mm2.

Impact Performance of GFRP Laminates with Modified Epoxy Resin

Glass fiber composite materials in epoxy resin with different content of a nitrile rubber modified hybrid resin were manufactured by infusion with two different rubber concentrations. SX 10 epoxy resin was modified to improve the response of the laminates under impact loads. At the aim to test the improvement of the impact resistance over the conventional epoxy resin system, the rectangular specimens 100*150 mm2 were dynamically loaded in the center by a falling weight machine, Ceast Fractovis, using a cylindrical impactor with a hemispherical nose 19,8 mm in diameter and a total mass of 3.6 kg. Impact tests were carried out at penetration to obtain the complete load-displacement curve useful to measure the penetration energy and to highlight the characteristics points for the increasing energies evaluation, 5J, 10J and 20J, to investigate the damage start and propagation. After the impact tests, the specimens were observed by visual inspection to investigate the delamination extension whereas a confocal microscope was used for the indentation measurements. The obtained results on the modified epoxy system were compared to neat GFRP laminates impact performances. No significant impact performance difference was recorded between samples with different nitrile rubber modifier content. A higher indentation was recorded on the modified samples related with a lower delamination extension. It could represent a good practical results since from a simple external damage measurement it can be possible to obtain information about a low internal delamination.

Analysis of symmetric and asymmetric glass fiber reinforced plastic laminates subjected to low-velocity impact

Low-velocity impact induced damage in symmetric and asymmetric laminates is analyzed. A generalized lay-up sequence is proposed for asymmetric laminate. Asymmetric laminate fabricated according to the proposed lay-up sequence have its stiffness characteristic almost identical to those of a symmetric laminates. Proposed lay-up sequence provides a laminate which have zero bending-extension coupling and behaves as quasi-isotropic laminate. A cylindrical impactor with hemispherical nose having mass 5.23 kg is impacted with a velocity of 3 ms−1, 4 ms−1, and 6 ms−1. Damage pattern and energy–time relation of proposed asymmetric laminate are compared with symmetric laminate having similar stiffness matrices. Energy absorbed by proposed quasi-isotropic asymmetric and symmetric laminate is also compared with laminate of different stacking sequence proposed by various researchers. Numerical analysis is done by commercially available software LS-DYNA.

Low velocity transverse impact response of a composite sandwich plate subjected to a rigid blunted cylindrical impactor

The low velocity impact problem of a composite sandwich plate impacted by a rigid blunted cylinder is analytically studied. The sandwich plate is composed of laminated face sheets and a rigid-plastic core which can be rigidly supported or simply supported. In contrast to the previous works, the face sheets are with no limitation for the stacking sequence. Also, the effects of in-plane displacement components u and v as well as initial in-plane forces acting on the edges of the sandwich plate are incorporated in the present article. First, by using the minimization of the total potential energy approach, closed form solutions are derived for the static indentation problem and the contact law (contact force–indentation relation) is determined. Then, spring-mass-dashpot models are developed to study the low velocity impact problem. The characteristics of the equivalent spring and dashpot are identified from the derived contact law and by incorporating the effect of the dynamic material properties of the sandwich plate. Analytical predictions for the impact force history are compared well with the experimental and analytical results in the literature. Results of a parametric study show that the stacking sequence of the face sheet has an insignificant effect on both the impact force and the contact duration. Furthermore, if the zero in-plane forces case to be considered as a reference state, the positive in-plane forces increase the impact force and decrease the contact duration, while the negative in-plane forces, with exactly the opposite effects, decrease the impact force and increase the contact duration.

Inclusion of Strain-Rate Effects in Low Velocity Impact Simulation of Laminated Composites

Composite materials are widely used in aircraft, automotive, marine and railway applications and are exposed to impact loads, in particular low velocity impact. As material properties of composites are affected by strain-rate [, finite element analysis (FEA) by using static properties would not predict their impact behaviour accurately. Thus, the objective of this study was to include strain-rate effects in the simulation of composite laminates under low velocity impact. This was achieved using ABAQUS anisotropic damage model (ADM) by taking account of material properties changes as a function of log strain-rate using user-defined ABAQUS/VUSDFLD subroutine Strain-Rate Dependent ADM (SRD ADM). Results obtained from SRD ADM were validated using simple tensile test done by Okoli [. Subsequently a three-point bending impact event of a simple composite laminate beam by a cylindrical steel impactor was simulated using both the original ABAQUS Static ADM and the user-defined SRD ADM, and compared with experimental impact test results done by [. The results show that reductions in errors of predicted maximum impact reaction force (compared to experimental data) were achieved from 29% using Static ADM to 14% using SRD ADM and from 35% using Static ADM to 15% using SRD ADM respectively for impactor speeds of 2 ms-1 and 5 ms-1.

Impact properties of tungsten-based alloys under conditions of high-speed interaction

Some aspects of obtaining alloys of the tungsten–nickel–iron–cobalt (TNIC) system have been investigated by the method of liquid-phase sintering of powder preparations, including those containing nano-size tungsten powders. By varying the initial porosity of the powder preparations, samples of highly porous composites have been obtained. A calculational-experimental method was used to investigate the penetrating power of cylindrical impactors made from TNIC alloys on steel plates. An increase in penetration depth with growth of porosity of the sample has been established in the considered range of impact speeds.

Towards reducing impact-induced brain injury: lessons from a computational study of army and football helmet pads

We use computational simulations to compare the impact response of different football and U.S. Army helmet pad materials. We conduct experiments to characterise the material response of different helmet pads. We simulate experimental helmet impact tests performed by the U.S. Army to validate our methods. We then simulate a cylindrical impactor striking different pads. The acceleration history of the impactor is used to calculate the head injury criterion for each pad. We conduct sensitivity studies exploring the effects of pad composition, geometry and material stiffness. We find that (1) the football pad materials do not outperform the currently used military pad material in militarily relevant impact scenarios; (2) optimal material properties for a pad depend on impact energy and (3) thicker pads perform better at all velocities. Although we considered only the isolated response of pad materials, not entire helmet systems, our analysis suggests that by using larger helmet shells with correspondingly thicker pads, impact-induced traumatic brain injury may be reduced.

Changes in chondrocyte gene expression following in vitro impaction of porcine articular cartilage in an impact injury model

Our objective was to monitor chondrocyte gene expression at 0, 3, 7, and 14 days following in vitro impaction to the articular surface of porcine patellae. Patellar facets were either axially impacted with a cylindrical impactor (25 mm/s loading rate) to a load level of 2,000 N or not impacted to serve as controls. After being placed in organ culture for 0, 3, 7, or 14 days, total RNA was isolated from full thickness cartilage slices and gene expression measured for 17 genes by quantitative real-time RT-PCR. Targeted genes included those encoding proteins involved with biological stress, inflammation, or anabolism and catabolism of cartilage extracellular matrix. Some gene expression changes were detected on the day of impaction, but most significant changes occurred at 14 days in culture. At 14 days in culture, 10 of the 17 genes were differentially expressed with col1a1 most significantly up-regulated in the impacted samples, suggesting impacted chondrocytes may have reverted to a fibroblast-like phenotype.

Approximate modeling of wave processes in elastoplastic solids

The single- and multi-wave processes in the elastoplastic solids are modeled based on the approximate approach proposed. We consider one- and two-dimensional problems on propagation of the longitudinal waves arising at normal impact on the boundary of an isotropic half-space, the problem of shock-wave reflection from a free surface of a plate and the problems on two-dimensional fracture of a plate, produced by a cylindrical impactor. The proposed approach allows one to simplify considerably the analysis of these and others similar problems taking into account the elastoplastic behavior of the solid.

Failure Modes for Single-Layer Reticulated Domes under Oblique Impact

FE models of both the single-layer Kiewitt-8 reticulated domes with a span of 60m and the cylindrical impactor were developed incorporating ANSYS/LS-DYNA. Afterward, fourteen groups impact are simulated by changing the impact position or impacted angle on reticulated dome, and impact velocity and mass of impactor are changed for each group impact. On the basis of large numbers of numerical simulations, characteristics of dynamic response for reticulated dome under impact are shown. And four failure modes (Members slightly damaged, Local collapse of dome, Global collapse of dome, Members shear failed) are presented for single-layer Kiewitt-8 reticulated dome under diverse impact. The distributing of failure modes for the fourteen types impact are different from each other, and the adverse position and angle are summrized.