Effect Of Impact Energy Research Articles

Dynamic Behaviour and Catenary Action of Axially-restrained Steel Beam Under Impact Loading

In this paper, the dynamic response and catenary action of axially restrained steel beam under impact loadings is examined through a combination of experimental and numerical investigations. The results of six impact tests on the axially restrained welded H-beams by means of the drop hammer test machine are presented. The main behavioural patterns and the key response characteristics including the development of impact force, deformation and strain, as well as failure modes are examined, with emphasis on the effect of impact energy and the width to thickness ratio of beam flange. Finite element models are also developed and validated against the available testing results. It is demonstrated that the detailed FE model can reasonably capture the response of the welded H-beams under impact loadings. Moreover, the mechanism of catenary action was identified based on the development of the internal force in the welded H-beams.

Effect of impact energy on damage resistance and mechanical property of C/SiC composites under low velocity impact

The present study investigated the damage resistance of two dimensional carbon fiber reinforced silicon carbide (C/SiCs) composites subjected to low velocity impact (LVI). Damage microstructures of specimens under different impact energies (Ei) were characterized by infrared thermography, X-ray computed tomography and scanning electron microscopy. The real damage radii of specimens were found to change slightly with Ei, whereas apparent damage radii where much larger. Overall, the fabricated 2D C/SiC composites exhibited good damage resistance to LVI with nominal post-impact tensile strengths remaining at 89.4%, 83.35%, 76.97%, and 74.84% of their pre-impacted counterpart of 158MPa, for impact energies of 3, 4, 5, and 6J, respectively. Compared with the as-received one, after LVI real tensile strengths of the C/SiC composite specimens increased by 5.84% for the Ei of 3J, 9.27% for 4J, −1.83% for 5J, −3.16% for 6J.

Theoretical model of low-velocity impact on foam-core sandwich panels using finite difference method

In this article, a three-dimensional solution based on the Fourier’s series and finite difference method has been presented to study the low-velocity impact on sandwich panels with foam core and composite face sheets. The Navier’s equations are derived and displacements are substituted by their corresponding Fourier’s series and three partial differential equations with coefficients of Fourier’s series are obtained. The contact force has been considered as a Fourier’s series of impactor displacement and deflection of top face sheet. Also, the model is verified by experiments performed on sandwich panel with epoxy/woven-fiberglass composites, face sheets and polyurethane foam core, and other researchers’ works. The history of contact forces and lateral displacement of contact point has been obtained experimentally and compared with theoretical model. Finally, the effects of impact energy and geometrical parameters including in-plane dimension ratio, core thickness, and face sheet thickness on contact force and lateral deflection histories have been investigated.

Low-speed bending impact behavior of adhesively bonded single-lap joints

This study addresses the low-speed impact behavior of adhesively bonded single-lap joints. An explicit dynamic finite element analysis was conducted in order to determine the damage initiation and propagation in the adhesive layers of adhesive single-lap joints under a bending impact load. A cohesive zone model was implemented to predict probable failure initiation and propagation along adhesive–adherend interfaces whereas an elasto-plastic material model was used for the adhesive zone between upper and lower adhesive interfaces as well as the adherends. The effect of the plastic deformation ability of adherend material on the damage mechanism of the adhesive layer was also studied for two aluminum materials Al 2024-T3 and Al 5754-0 having different strength and plastic deformation ability. The effects of impact energy (3 and 11 J) and the overlap length (25 and 40 mm) were also investigated. The predicted contact force-time, contact force-central displacement variations, the damage initiation and propagation mechanism were verified with experimental ones. The SEM and macroscope photographs of the adhesive fracture surfaces were similar to those of the explicit dynamic finite element analysis.

Experimental and numerical research on the low velocity impact behavior of hybrid corrugated core sandwich structures

Corrugated core sandwich structures are fabricated with carbon fiber reinforced polymer (CFRP) face sheets and aluminum alloy cores. This lightweight design concept enables sandwich structures to maximize the specific bending stiffness/strength and improve the energy absorption capability. The low velocity impact behavior of such structures is investigated by experimentally and numerically. A range of low velocity impact tests are conducted to study the impact resistance, considering the effects of impact energy, core thickness and impact site on the impact load, absorbed energy and failure modes. A user subroutine VUMAT is developed to model the composite face sheet behavior, in which a progressive damage model based on the Hashin failure criteria and Yeh delamination failure criteria is implemented in ABAQUS/Explicit. There is a generally good agreement between the experimental and predicted results in terms of impact force, absorbed energy, and failure modes of sandwich structures. These studies reveal that fiber damage, matrix damage and delamination of face sheets as well as buckling of core members occur under varied impact energies. The results provide insight into the low velocity impact behavior of such structures, and the knowledge of failure mechanisms could be useful for the development of novel lightweight multifunctional structures.

Nano-Impact Tests with Ultra-High Strain Rate Loading Using Graphene and Ion Impact

Strain rate is essential in study of the physics of fluids and solids undergoing deformation. State-of-art high strain rate tests have mainly been in macro-scale with an upper limit of [Formula: see text]. A graphene-based layered system is proposed to conduct nanometer-scale high strain rate testing. The process is investigated by molecular dynamics simulations. Accelerated single ion or group of ions are used to impact on the proposed system to generate ballistic or plate-like impact scenarios. The effects of impact energy, shape of impact absorber and the impaction location are investigated. The graphene layer is the key of the proposed system to spread the load and protect the sample. The results indicate that ion group and single ion impacts produce strain rates of [Formula: see text]–[Formula: see text] and [Formula: see text]–[Formula: see text], respectively. Ion group impact produces a more significant signal than single ion impact on the sensing nano-layer in the system. The ultimate strength of an Al-Cu alloy sample during ion impact is estimated to be 215[Formula: see text]MPa to 251[Formula: see text]MPa, significantly lower than predicted by the Johnson–Cook model because of the rapidly increased temperature and melting in the sample. The results demonstrate new possibilities for understanding high strain rate effects at nano-scale.

Micromechanical Modeling of Impact Damage Mechanisms in Unidirectional Composite Laminates

Composite laminates are susceptible to the transverse impact loads resulting in significant damage such as matrix cracking, fiber breakage and delamination. In this paper, a micromechanical model is developed to predict the impact damage of composite laminates based on microstructure and various failure models of laminates. The fiber and matrix are represented by the isotropic and elastic-plastic solid, and their impact failure behaviors are modeled based on shear damage model. The delaminaton failure is modeling by the interface element controlled by cohesive damage model. Impact damage mechanisms of laminate are analyzed by using the micromechanical model proposed. In addition, the effects of impact energy and laminated type on impact damage behavior of laminates are investigated. Due to the damage of the surrounding matrix near the impact point caused by the fiber deformation, the surface damage area of laminate is larger than the area of ​​impact projectile. The shape of the damage area is roughly rectangle or elliptical with the major axis extending parallel to the fiber direction in the surface layer of laminate. The alternating laminated type with two fiber directions is more propitious to improve the impact resistance of laminates.

Flexural impact response of textile-reinforced aerated concrete sandwich panels

Abstract Mechanical response of textile-reinforced aerated concrete sandwich panels was investigated using an instrumented three-point bending experiment under static and low-velocity dynamic loading. Two types of aerated concrete: autoclaved aerated concrete (AAC) and polymeric Fiber-Reinforced Aerated Concrete (FRAC) were used as the core material. Skin layer consisted of two layers of Alkali Resistant Glass (ARG) textiles and a cementitious binder. Performance of ductile skin-brittle core (TRC–AAC) and ductile skin-ductile core (TRC–FRAC) composites was evaluated in terms of flexural stiffness, strength, and energy absorption capacity. The effect of impact energy on the mechanical properties was measured at various drop heights on two different cross-sections using energy levels up to 40 J and intermediate strain rates up to 20 s− 1. The externally bonded textile layers significantly improved the mechanical properties of light-weight low-strength aerated concrete core under both loading modes. Dynamic flexural strength was greater than the static flexural strength by as much as 4 times. For specimens with larger cross-sections, unreinforced-autoclaved AAC core had a 15% higher apparent flexural capacity. With 0.5% volume of polypropylene fibers in the core, the flexural toughness however increased by 25%. Cracking mechanisms were studied using high speed image acquisition and digital image correlation (DIC) technique.

Experimental study on tubular K-joints under impact loadings

This paper experimentally examines the behaviour of tubular K-joints subjected to impact loadings. An experimental programme involved two tests on unstiffened tubular K-joints under different impact energies and one on stiffened configuration is carried out through a high-performance drop hammer machine. The dynamic responses of three tubular K-joints are described and discussed with emphasis on the effect of impact energy and internal stiffeners. Based on the experimental results, the key behavioural patterns including the development of impact force, deformation and strain, as well as failure modes are identified, and impact mechanism is also investigated. It is shown that the local indentation at the impacted area of the chord is the main plastic deformation of tubular K-joints under impact, and higher applied impact energy results in larger plasticity. Moreover, the presence of internal ring stiffeners significantly improves the impact resistance of tubular K-joints.

Experimental study on the behavior of wear resistant steels under high velocity single particle impacts

High velocity solid particle erosion may cause severe damage and high wear rates in materials used for wear protection. An experimental work on the behavior of wear resistant steels, including three high-strength martensitic alloys and a carbide-reinforced metal matrix composite, was performed in high rate single impact conditions. Characterization of the mechanical behavior of the materials at high strain rates was conducted using the Hopkinson Split Bar technique to identify the effects of strain rate on strain hardening and the prevailing failure mechanisms. The high velocity impact experiments using spherical projectiles were carried out at various impact angles and projectile velocities. The effects of impact energy and impact angle were studied and discussed. Wear was analyzed as volume loss from the surface, but it was also presented in a more precise way by taking into account the actual energy spent on the plastic deformation and wear. In-situ high speed photography and post impact characterization of the impact craters were used to reveal the prevailing failure and wear mechanisms. Depending on the impact angle and impact energy, different wear mechanisms of plastic deformation, cutting, shear banding and fracture were identified. The martensitic steels exhibited adiabatic shear banding in the microstructure at high strain rates and impact velocities, which may accelerate the wear. The carbide reinforced steel was found susceptible to catastrophic fracturing especially at high impact angles.

Low-velocity flexural impact response of fiber-reinforced aerated concrete

Impact response of fiber-reinforced aerated concrete was investigated under a three-point bending configuration based on free-fall of an instrumented impact device. Two types of aerated concrete: plain autoclaved aerated concrete (AAC) and polymeric fiber-reinforced aerated concrete (FRAC) were tested. Comparisons were made in terms of stiffness, flexural strength, deformation capacity and energy absorption capacity. The effect of impact energy on the mechanical properties was investigated for various drop heights and different specimen sizes. It was observed that dynamic flexural strength under impact was more than 1.5 times higher than the static flexural strength. Both materials showed similar flexural load carrying capacity under impact, however, use of 0.5% volume fraction of polypropylene fibers resulted in more than three times higher flexural toughness. The performed instrumented impact test was found to be a good method for quantifying the impact resistance of cement-based materials such as aerated concrete masonry products.

Simple approach to estimate residual flexural strength distribution of composite sandwich structure with impact-induced damage

A new approach was developed to predict the statistical distribution of residual flexural strength of composite structures subjected to low velocity impact. Based on the assumption that the flexural strength of unimpacted structures follows the two-parameter Weibull distribution, the model was formulated as a function of the Weibull parameters for strength of unimpacted structures and residual strength of impacted structures. The model was verified by using an experiment for honeycomb core sandwich structure. The experiments included impact and flexural tests to generate the residual strength of structure. Theoretical predictions on the statistical distribution were in conformance with the experiments. The effect of impact energy on the distribution of residual flexural strength was also examined.

Investigation of plasma-powder hardfacing of Hadfield steel with impact treatment

The combination of forging with plasma-powder hardfacing is a further development of the method applied in the reconditioning of railway junctions. The process, equipment and the effect of impact energy on the properties of layers are investigated. The technology is promising for the hardening (reconditioning) of long components and eliminates the need for preliminary bending and subsequent heat treatment.

Impact-based pulverisation of dried and screened Norway spruce (Picea abies) sawdust in an oscillatory ball mill

Abstract This study investigates the impact-based pulverisation of dried and screened Norway spruce (Picea abies) sawdust into a median particle size range of less than 100 μm in an oscillatory ball mill. Pulverisation is studied by considering the effects of impact energy, the number of impact events and the amount of feed on the size and shape properties of the pulverised wood. The impact energy is treated as the kinetic energy of the grinding ball and the impact event is considered as a period during which the grinding ball travels from one end-wall of the grinding jar to the other. Given a certain number of impact events, the use of higher impact energy lowers the particle sizes of the wood particles until a minimum size is attained. The minimum value for the median particle size is found between 13 μm and 20 μm. In the pulverisation, the aspect ratios of the wood particles decrease with the use of a higher impact energy and larger number of end-wall collisions. Within a certain range, the changes in the size and shape properties can be predicted from the total impact energy available for the pulverisation when the energy efficiency of the pulverisation remains constant. The energy efficiency of the pulverisation process can be affected by varying the amount of the feed. The pulverisation of dried Norway spruce sawdust from a median size range of 1 mm and 2 mm down to a median size below 100 μm is accomplished with the specific energy consumption of 0.36 kJ/g (100 kWh/t); reduction to a median size below 20 μm is accomplished with the specific energy consumption of 1.4 kJ/g (380 kWh/t).

Microstructure and surface roughness of graphite‐like carbon films deposited on silicon substrate by molecular dynamic simulation

Molecular dynamics simulations are performed on the atomic origin of the growth process of graphite‐like carbon film on silicon substrate. The microstructure, mass density, and internal stress of as‐deposited films are investigated systematically. A strong energy dependence of microstructure and stress is revealed by varying the impact energy of the incident atoms (in the range 1–120 eV). As the impact energy is increased, the film internal stress converts from tensile stress to compressive stress, which is in agreement with the experimental results, and the bonding of C‐Si in the film is also increased for more substrate atoms are sputtered into the grown film. At the incident energy 40 eV, a densification of the deposited material is observed and the properties such as density, sp3 fraction, and compressive stress all reach their maximums. In addition, the effect of impact energy on the surface roughness is also studied. The surface morphology of the film exhibits different characteristics with different incident energy. When the energy is low (<40 eV), the surface roughness is reduced with the increasing of incident energy, and it reaches the minimum at 50 eV. Copyright © 2012 John Wiley & Sons, Ltd.

Influence of Moisture Absorption on Impact Strength and Failure Behavior of Hybrid Jute-Carbon/ Epoxy Composite

Hybrid jute-carbon/ epoxy composites, fabricated by hand lay-up method with fiber volume fractions of 0.47, 0.58 and 0.68 were used to investigate water absorption behavior as a function of immersion time and fiber content. The effect of moisture content on impact strength and failure modes was also studied. Results show that the moisture absorption increased with increasing the immersion time in water and it was more with higher fiber fraction specimens. Maximum moisture contents of 0.45%, 0.52% and 0.61% were recorded for the specimens containing fiber volume fractions of 0.47, 0.58 and 0.68, respectively. The impact strength reduced with increasing moisture absorption in all specimens containing different fiber fractions. Composites with higher fiber content gave reduced impact strength under all test conditions. Composites of different fiber fractions and of highest moisture content produced impact strengths about 20 to 28% less than those strengths obtained without water immersion. The 47 vol% fiber specimen was least affected by water immersion and impact strength reduction was only 17% after immersion till saturation. Failure occurred by mainly by delamination and it was evident in all fractured specimens. Results of the effect of impact energy on moisture content have been evaluated using ANOVA ANALYSIS and the results gave errors of 1%, 0.6 % and 0.8 % for 0.47, 0.58 and 0.68 fiber volume fraction specimens, respectively.

Research on Punched Pile Construction–Induced Dynamic Response of Bridge Pile Foundation

By use of the microseismic monitoring system, the dynamic response of punched pile construction of bridge pile foundation is studied and discussed for the first time. Wave data of loads acting on the construction is group-collected by means of the microseismic experiment on site. Then the waveform, vibration frequency and energy of testing data are analyzed. On the basis of the results, the weaken rules of vibration acceleration and energy are studied, and the effect of impact energy on the vibration velocity is analyzed. It shows that impact energy attenuates exponentially with the distance from the epicentre. The conclusion establishes the theoretical basis for studying the vibrant characteristic of punched pile construction, and provides valuable reference for engineering practice to take effective measures to reduce construction vibration.

Shock Attenuation of Intervertebral Disc Following Fatigue Loading

ABSTRACTShock absorption is one of the fundamental biomechanical functions of disc. The knowledge of the effect of fatigue loading, impact energy and contact period on the disc shock attenuation is important in clarifying the risk factors of back pain and evaluating the efficacy of novel disc prosthesis. The purpose of this study is to find the changes of shock attenuation of motion segment after fatigue loading, and the effect of impact energy and contact period on the disc shock attenuation pre and post fatigue loading.The 3-unit porcine spinal motion segment was used for testing. The impact test was applied pre and post fatigue loading. Impact energy and contact period were controlled in the experiment. Shock attenuation properties, including the acceleration attenuation (AA) of disc, force transmissibility (FT) and phase delay of force (PDF) of motion segment, were calculated from the acceleration and force responses.The results showed that the shock attenuation properties (acceleration attenuation and force transmissibility) decreased post fatigue. The disc acceleration attenuation was independent of impact energy and contact period. The disc acceleration attenuation was 0.78 (−1.06dB) pre fatigue and 1.04 (0.14dB) post fatigue. The force transmissibility of motion segment decreased post fatigue only during short contact period. The phase delay of force did not change significantly post fatigue.We found that the fatigue loading decreased the disc shock attenuation. The disc was at higher risk of injury following fatigue loading even at a mild impact loading. The disc acceleration attenuation was invariant of impact energy and contact period, but decreased post fatigue. The disc acceleration attenuation is a good index to evaluate the degree of fatigue injury.

High resolution measurement of dynamic (nano) indentation impact energy: a step towards the determination of indentation fracture resistance

A Micro Materials (UK) NanoTest has been modified for fast data acquisition at up to 200 kHz to enable high-resolution (sub-pJ) impact energy measurement. Displacement versus time data were acquired at 20 kHz in 3-s bursts to capture the acceleration, impact and rebounding of the pendulum-mounted indenter. The data acquired were analysed to provide measurements of position, velocity, acceleration, impact distance, impact depth (elastic and plastic) potential and kinetic energy throughout the impact cycle and provided high-resolution information throughout the impact event itself, which lasted only ∼ 10 ms. The ability of the system to detect fracture events and measure energies associated with these events is investigated. The effect of impact energy and indenter geometry is demonstrated and it is shown that the system is able to detect damage events and measure the difference in the energy absorbed in an impact when damage occurs.

Permeation-after-impact Properties of CFRP Laminates for Use on Propellant Tank

This paper describes the experimental study of impact testing and permeability testing of CFRP laminates for application of propellant tanks considering the reliability of the tank structures associated with foreign object impact damage. Three types of quasi-isotropic laminates with different laminate thickness were prepared and subjected to transverse impact tests, nondestructive inspections, and helium gas permeation tests in series. Transverse impacts induced delaminations, matrix cracking, and fiber breakage, which caused severe through-thickness gas leakage. Effects of impact energy and laminate thickness on the permeation-after-impact properties are discussed, and the critical damage mode controlling the severe gas leakage is identified.