Impact Compressive Loading Research Articles

Dynamic energy evolution and fragmentation characteristics of damaged rock under impact compression loading

Dynamic energy evolution and fragmentation characteristics of damaged rock under impact compression loading

Mechanical properties of periodic rectangular tube sandwich structure subjected to out-of-plane impact compression loading

Owing to its unique deformation form, negative Poisson’s ratio sandwich structure has attracted significantly widespread interest, especially in the impact protection field. However, inferior mechanical properties severely limit their practical applications. To enhance its mechanical properties, a new type of periodic sandwich structure of rectangular tube was designed and fabricated, and the structure presents negative Poisson’s ratio characteristic under out-of-plane impact compression load. To evaluate its mechanical properties, the deformation form and equivalent yield strength of the periodic rectangular tube sandwich structure were obtained through the split Hopkinson pressure bar (SHPB) experiment. A numerical model of the different wall thicknesses of periodic rectangular tube sandwich structure (PRTSS) was established, and the accuracy of the model was verified by comparing it with the deformation form and equivalent yield strength obtained from experimental results. The results show that with the increase of rectangular tube wall thickness in PRTSS, the equivalent yield strength increases, and the equivalent yield platform strain decreases. Moreover, through the simulation results under four different strain rates, it is obtained that the equivalent yield stress of PRTSS increases with the increase of strain rate, and the straining length of the equivalent yield platform decreases with the increase of strain rate. The effect of wall thickness and strain rate on PRTSS was analyzed, which provided certain guiding significance for the application of the structure in the field of impact protection.

Behaviour of polymer-filled–concrete–steel double-skin tubular columns under combined lateral impact and axial compression loading

The paper presents a study on the suitability of using a Polymer as a protective layer for critical structural elements prone to impact damage. Conventional damage mitigation methods include using an outer steel jacket with a void, protecting the inner concrete-steel composite column. Whilst it is usually found that the outer steel jacket can partially negate the impact load, the inner column still experiences a significant brunt of the impact load. In order to minimise the damage to the overall critical structural element, a concept of a Polyurethane Polymer-Filled–Concrete–Steel Double-Skin Tubular Column is proposed. Scaled-down versions of two polymer-filled double-skin column configurations were tested under low-velocity impact using a drop tower. The pre and post-damage columns were tested for their axial capacities. These polymer-filled columns were critically compared to their nominal samples without the Polyurethane fill. It was shown that the mid-span deflection and localised indentations were reduced by 17%, and the localised deformations (at the point of impact) were reduced by up to 70% overall. The columns with Polyurethane also showcased retention of 70% of axial capacity post-impact, whilst the nominal sample was only capable of retaining 48%. Finally, the intrinsic properties of Polyurethane were discussed along with a critical discussion on its ability and mechanism on how energy is dissipated by comparing mechanical and chemical properties.

Impact loading of additively manufactured metallic stochastic sheet-based cellular material

The mechanical response of additively manufactured sheet-based stochastic cellular materials under impact loading was investigated in this work. Samples with four different relative densities (13%, 16%, 19%, and 21%) were fabricated out of 316 L stainless steel using the powder bed fusion (PBF) additive manufacturing (AM) technique. The samples were then tested under quasi-static and dynamic (impact) compressive loading conditions to evaluate their mechanical behavior. All analyzed samples showed a similar progressive plateau stress behavior at all analyzed strain rates. The Crash Force Efficiency (CFE) values of samples at analyzed strain rates were in the range of 67–70%, indicating the uniformity of their mechanical response, which is a vital application feature. The samples exhibited excellent Specific Energy Absorption (SEA) capacity ranging between 5 and 9.2 J/g in the quasi-static deformation mode while achieving up to 35 J/g in the shock deformation mode. Thus, the proposed design approach has great potential for impact and blast mitigation applications. The first and second critical loading velocities of analyzed samples are proportional to the relative density and are in the range of 25–32 m/s and 43–56 m/s, respectively. Minor strain rate hardening was observed in quasi-static deformation mode, while a significant strain rate hardening was observed in shock deformation mode achieved by powder gun testing. The developed and validated computational models offered a more detailed analysis of the deformation mechanism and provided means to predict the sample's behavior at very high strain rates.

Comparison study on the impact compression mechanical properties of coral aggregate concrete and ordinary Portland concrete

Coral aggregate concrete (CAC) has been widely used in the construction of South Sea islands and reefs. However, the dynamic mechanical properties of CAC under high strain rate loading are rarely reported. This study aims to compares the mechanical properties of CAC and ordinary Portland cement concrete (OPC). A 100 mm-diameter split Hopkinson pressure bar (SHPB) was used to perform an impact compression loading test on CAC and OPC. The dynamic mechanical properties of CAC were assessed in terms of the failure pattern, particle evolution after failure, dynamic increase factor (DIF), brittleness analyses and impact toughness. The results show that the failure plane of CAC directly penetrates the coral aggregate, unlike OPC, which has an interfacial transition zone (ITZ). When the strain rate reaches 166 s−1, the evolution of the particle size after CAC breaks basically becomes stable compared with that after OPC breaks. Under the same strain rate, the DIF value of CAC is higher than that of OPC. An empirical equation is proposed for the estimation of the DIF of CAC based on the experimental results. A significant influence of the strain rate on the dynamic elastic modulus of CAC was observed. Moreover, a method for evaluating the brittleness of concrete under dynamic loading is proposed. At a strain rate of 10-5-166 s−1, comparing with OPC materials shows that there is an obvious brittle-ductile transition in CAC materials. The impact toughness of CAC is significantly lower than that of OPC, and the energy absorbed by CAC before crushing is significantly less than that absorbed by OPC.

Low velocity impact and compressive response after impact of thin carbon fiber composite panels

Impact damage of laminated composite structures continues to be a challenging problem. The complexity of damage morphology, the sequence of damage events, and multiple damage modes pose significant challenges when it comes to design for damage tolerance. In an effort to reduce some of the complexity, a systematic experimental study was conducted to understand the sequence of damage during impact of a thin composite plate. Two configurations of carbon fiber reinforced epoxy composite panels were impacted with increasing impact energies. Digital image correlation (DIC), using high speed camera, was performed to measure plate deflection and strain evolution during the impact event. Detailed post impact measurement and imaging were conducted to quantify the extent of damage and delamination. Compression after impact (CAI) tests were conducted to ascertain the post impact compressive load carrying capability of the panel. The results of the experiments indicate a sequence of damage from back surface splitting, delamination and then impact surface compressive failure. Correlations were also found between impact energies, panel configuration and damage type and morphology. The data thus generated is useful for validating computational models for impact damage and CAI. An approach to performing such validation is also provided in this study.

Local deformation of Mg–7Gd–5Y–1.2Nd–0.5Zr magnesium alloy under high speed impact along extrusion direction

The high strain rate deformation behavior of Mg–7Gd–5Y–1.2Nd–0.5Zr alloy was carried out at several temperatures. Through the truncated test of cap specimen, it was found that the local deformation occurred in the design shear zone, but no adiabatic shear band was observed. The deformation mechanism was mainly pyramidal slip, supplemented by prismatic slip, basal slip, and dynamic recrystallization. Among them, pyramidal 〈c + a〉 slip could coordinate deformation through the slip component along the 〈c〉 direction. The Johnson–Cook constitutive model and failure model were modified, and then the local deformation of the cap specimen along the extrusion direction was simulated by LS-DANY software. The results showed that the local severe deformation occurred in the area of the cap specimen with sharp change in shape, which was at an angle of 45 ° with the impact compression loading along extrusion direction. The temperature increased continuously with the amount of deformation until fracture occurred. The results showed that the alloy had high resistance to local high strain deformation and fracture.

Near-fiber nanomechanical mapping and impact failure mechanism of 3D braided composites subjected to thermo-oxidative environment

The macroscopic mechanical behaviors generally correlate with nanomechanical properties, especially elastic modulus. This paper presents the thermo-oxidative ageing effects on nanoscale elastic modulus and impact failure mechanism of 3D braided composites at micro and macro levels using PeakForce Quantitative Nano-Mechanics (PF-QNM) and digital image correlation (DIC) technologies. The values of nanoscale elastic modulus of near-fiber resin pocket were about three times than that of global modulus in neat resin under low-velocity impact compression (LVIC) loading. However, the modulus retention rates were consistent which was ∼88% after ageing for 16 days at 180 °C. The decline of them has provided a direct evidence for resin degradation after ageing. In addition, the in-plane impact failure mechanism of braided composites mainly contained five modes, i.e., matrix cracking, interface cracking, matrix fracture and peeling off, fiber buckling and slipping, and fiber breakage. Thermo-oxidative ageing only changed the crack propagation path but not the damage modes.

Dynamic Behaviors of Mortar Reinforced with NiTi SMA Fibers under Impact Compressive Loading.

In this study, a compressive impact test was conducted using the split Hopkinson pressure bar (SHPB) method to investigate SMA fiber-reinforced mortar’s impact behavior. A 1.5% fiber volume of crimped fibers and dog-bone-shaped fibers was used, and half of the specimens were heated to induce recovery stress. The results showed that the appearance of SMA fibers, recovery stress, and composite capacity can increase strain rate. For mechanical properties, the SMA fibers reduced dynamic compressive strength and increased the peak strain. The specific energy absorption of the reinforced specimens slightly increased due to the addition of SMA fibers and the recovery stress; however, the effect was not significant. The composite behavior between SMA fibers and the mortar matrix, however, significantly influenced the dynamic compressive properties. The higher composite capacity of the SMA fibers produced lower dynamic compressive strength, higher peak strain, and higher specific energy absorption. The composite behavior of the dog-bone-shaped fiber was less than that of the crimped fiber and was reduced due to heating, while that of the crimped fiber was not. The mechanical properties of the impacted specimen followed a linear function of strain rate ranging from 10 to 17 s−1; at the higher strain rates of about 49–67 s−1, the linear functions disappeared. The elastic modulus of the specimen was independent of the strain rate, but it was dependent on the correlation between the elastic moduli of the SMA fibers and the mortar matrix.

Geometrically Nonlinear Dynamic Response of Perforated Plates by Modified Differential Quadrature Method

The paper presents a modified differential quadrature (MDQ) method to investigate the dynamic response of perforated plates with elastically restrained edges under uniaxial impact compressive load. The perforated plate is divided into several separate plate elements that can be connected by using penalty function method (PFM) to ensure continuity along the shared edges. The in-plane stress distribution of the plate under the mechanical edge loading is determined by the pre-buckling analysis. To analyze the effect of elastically restrained edges on the dynamic response of perforated plates, artificial springs imposed for the edges are considered in the governing equilibrium equations. Verification analysis is carried out to demonstrate the efficiency and accuracy of the proposed method by comparing the results obtained with those available in the literature. Finally, the various effects of initial imperfection, rotational restrained stiffness, hole size and location, and shear load, on the dynamic response of perforated plates are investigated. The results show that the dynamic buckling load of perforated plates is significantly influenced by the rotational restraint stiffness, hole size and shear load as well as the initial geometric imperfection, whereas the effect of hole location can be neglected in the analysis of dynamic buckling of plates. Additionally, the results predicted by the proposed method can correlate well with the available numerical results.

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.

An Experimental Investigation of the Behavior of Strain-Hardening Cement-Based Composites (SHCC) under Impact Compression and Shear Loading

The ductile behavior of strain-hardening cement-based composites (SHCC) under direct tensile load makes them promising solutions in applications where high energy dissipation is needed, such as in earthquakes, impacts by projectiles, or blasts. However, the superior tensile ductility of SHCC due to multiple cracking does not necessarily point to compressive and shear ductility. As an effort to characterize the behavior of SHCC under impact compressive and shear loading relevant to the aforementioned high-speed loading scenarios, the paper at hand studies the performance of a particular SHCC and its constituent, cement-based matrices using the split-Hopkinson bar method. For compression experiments, cylindrical specimens with a length-to-diameter ratio (l/d) of 1.6 were used. The selected length of the sample led to similar failure modes under quasi-static and impact loading conditions, necessary to a reliable comparison of the observed compressive strengths. The impact experiments were performed in a split-Hopkinson pressure bar (SHPB) at a strain rate that reached 110 s−1 at the moment of failure. For shear experiments, a special adapter was developed for a split-Hopkinson tension bar (SHTB). The adapter enabled impact shear experiments to be performed on planar specimens using the tensile wave generated in the SHTB. Results showed dynamic increase factors (DIF) of 2.3 and 2.0 for compressive and shear strength of SHCC, respectively. As compared to the non-reinforced constituent matrix, the absolute value of the compressive strength was lower for the SHCC. Contrarily, under shear loading, the SHCC demonstrated higher shear strength than the non-reinforced matrix.

Constitutive model of water-saturated marble under coupling effects of uniaxial impact compressive loading and low-temperature

Constitutive model of water-saturated marble under coupling effects of uniaxial impact compressive loading and low-temperature

Usefulness of FEM Analysis: Comparison with the Experimental Results of Woven Fabric CFRP Cylinders under Axial Impact Compressive Load

Usefulness of FEM Analysis: Comparison with the Experimental Results of Woven Fabric CFRP Cylinders under Axial Impact Compressive Load

Qualitative comparison of dynamic compressive pressure load and impact of WC/Co composite

Degradation of Cermet Materials (CM) under impact and pulse pressure is not thoroughly investigated. In this study, we qualitatively compare the behaviour of WC/Co samples under these types of loading.The new models of impact and dynamic compressive load of a WC/Co plate were investigated. We developed two models of the composite plate, namely, a continuous model and a model with crack appearance possibility in the interfaces/binders.We noted a qualitative difference of the shapes of the deformed structure due to different models and kind of loading. The differences also concern the Mises stress, equivalent plastic strains and damage parameter.The proposed models are suitable for both impact and pressure load. The possibility of cracks appearance should not be neglected. In case of the model with discontinuities, for both kinds of loads, the grains rotation and sliding is more distinct than in case of the continuous model.

Behavior of fiber reinforced mortar composites under impact load

This paper presents results of the experimental study on the behavior of plain and fiber reinforced cement mortars with different fibers under static and impact compressive load. Glass, polypropylene and carbon fibers were used in equal dosage by mass. The impact test was conducted using an impact tower with drop hammer, which represented the modification of the split-Hopkinson pressure bar system, with strain rates ranging from approximately 35 to 60 s-1. The results of the static test and impact test with two different drop heights were compared and discussed. Among other, it has been concluded that the tested fiber reinforced mortars had no greater static and impact strength compared to the plain mortar. Only their ductility was increased at both static and impact failure. Strengths and ductility of all composite specimens were similar, i.e. without the effect of fiber type. With the increase of strain rate, compressive strength is increased and ductility is decreased for all tested specimens.

Numeryczna analiza energochłonności cienkościennych słupów pryzmatycznych z przetłoczeniami

The paper presents results of a parametric study into energy absorption capability of thin-walled square section columns with redrawn dents, subjected to axial impact compressive load. Thin-walled aluminum tubes with four dents in the corners were under investigation. The varying parameters were the dent’s depth and distance of the dent to the base. The study was performed using Finite Element numerical code. Three crashworthiness indicators were examined: peak crushing force, crash load efficiency and stroke efficiency. The numerical results are shown in load-shortening diagrams, as well as diagrams and maps of crashworthiness indicators. It was found, that the main factor influencing a crushing mode and, subsequently, energy absorption capability, is a dent depth. The dent distance from the base is of less importance. Also a position of a dent, either at the bottom, or at the top base (the load application point) does not influence the crushing behavior significantly. For the deepest dents the relative increase of crash load efficiency (CLE) amounts 25% in comparison with the column without dents.

Analysis of Dynamic Plastic Deformation process on an Electrolytic Tough - Pitch copper (Cu-ETP): From material characterization to models improvement

This paper presents a comprehensive study of a direct impact compression loading on an Electrolytic Tough-Pitch copper (Cu-ETP). The aim of the study is to provide reliable experimental data in this dynamic loading using high-speed video camera records and real time projectile deceleration profiles. Test set-up has been optimized to ensure an efficient recovery of the samples after the Dynamic Plastic Deformation (DPD) process in the 103 to 104 s-1 strain rate range regime. Structural investigations have been made on post-mortem samples: microstructure investigations of recovered samples have shown more structural changes in terms of crystallographic texture and grain sizes. Post-mortem tensile tests have also been carried out to evaluate yield strength behavior of the Cu-ETP copper after the DPD process. Numerical simulations have been performed to evaluate the ability of empirical models to reproduce recorded signals. In-situ results (time evolution of strain, strain rate, temperature, etc.) given by the numerical analysis have contributed to enrich the post-mortem analysis.

On the tension-induced microcracks' nucleation in a PBX substitute material under impact compression loading

Nucleation and growth of microcracks is a dominant form of damage evolution in polymer bonded explosives (PBXs). The mechanism of such a damage evolution of PBX under impact loading was analyzed in this study. For safety and convenience, a PBX substitute material was firstly designed by mixing sugar and a new agglomerant to form polymer-bonded sugar materials (PBS). The dynamic test was carried out by SHPB technique at different impact velocity. The cracks' nucleation of PBS was analyzed by means of Micromechanics. The results indicate that the material possesses capability to adjust its microstructure, and the dynamic tensile stress at the surface of defects induces the microcracks' nucleation.

Plastic flow behavior based on thermal activation and dynamic constitutive equation of 25CrMo4 steel during impact compression

To evaluate the dynamic mechanical properties of 25CrMo4 steel, the stress-strain curve of 25CrMo4 steel have been obtained by performing quasi-static and impact compression experiments at strain rates ranging from 0.001 s−1 to 4163 s−1. The 25CrMo4 steel displays an obvious strain rate effect and its hardening rate changes with the strain and strain rate. It even shows softening effect at high strain rates. Further, the grains of 25CrMo4 steel show features of both body-centered cubic (BCC) and face-centered cubic (FCC) structures and are severely stretched and fragmented during impact loading, as evidenced by microscopic observations. Based on these two points, the Zerilli-Armstrong (ZA) constitutive equations have been improved reasonably. These can provide the mechanical properties of 25CrMo4 steel during impact compression loading, which can in turn be used as reference values for practical engineering analysis.