Effect Of Impact Loading Research Articles

Restrained tibial rotation may prevent ACL injury during landing at different flexion angles.

Internal tibial rotation is a risk factor for anterior cruciate ligament (ACL) injury. The effect of restraining tibial rotation (RTR) to prevent ACL injury during single-leg landing is not well understood. We aimed to investigate the effect of impact load and RTR on ACL injury with respect to flexion angle. We hypothesized that RTR could protect the knee from ACL injury compared to free tibial rotation (FTR) regardless of flexion angle and create a safety zone to protect the ACL. Thirty porcine specimens were potted in a rig manufactured to replicate single-leg landing maneuvers. A mechanical testing machine was used to apply external forces in the direction of the tibial long axis. A 3D displacement sensor measured anterior tibial translation (ATT). The specimens were divided into 3 groups of 10 specimens and tested at flexion angles of 22 ± 1°, 37 ± 1° and 52 ± 1° (five RTR and five FTR) through a consecutive range of actuator displacements until ACL failure. After dissection, damage to the joint was visually recorded. Two-way ANOVA were utilized in order to compare compressive forces, torques and A/P displacements with respect to flexion angle. The largest difference between peak axial compressive forces (~3.4 kN) causing ACL injury between RTR and FTR was reported at a flexion angle of 22°. Tibial torques with RTR was in the same range and < 20 Nm at the instance and just before ACL failure, compared to a significant reduction when cartilage/bone damage (no ACL failure) was reported. Isolated ACL injuries were observed in ten of the 15 FTR specimens. Injuries to bone and cartilage were more common with RTR. RTR increases the threshold for ACL injury by elevating the compressive impact load required at lower flexion angles. These findings may contribute to neuromuscular training programs or brace designs used to avoid excessive internal/external tibial rotation. Caution must be exercised as bone/cartilage damage may result.

Effects of Chromium Content and Impact Load on Microstructures and Properties of High Manganese Steel

In this paper, the effects of Cr content and impact load on the microstructure and properties of High Manganese Steel (HMS) were investigated. The results show that the hardness of HMS was increasing when the Cr content increased, but the hardness was not much changing when the Cr contents changed from 2% to 2,5% of weight. Under the impact load, the microstructure and the hardness were changed also. The Cr content effected on the depth of transition layer on surface under the impact load and the twinning occurred during impacting load.

Effects of cyclic impacts on the performance of a piezo-composite electricity generating element in a d33 mode energy harvesting.

The increasing use of piezoelectric generators to harvest energy from various ambient sources requires the establishment of durability data for piezoelectric materials. In this paper, a d3 mode piezocomposite electricity generating element (PCGE) was tested for its durability under cyclic impact loading. For this purpose, a motor driven lever system was designed to apply constant impact force on PCGEs. To investigate the durability of PCGEs, the output voltage of the PCGEs was observed upon repeated application of an impact force until eventual loss of the generated voltage. The experimental results enabled to determine the number of cycles until which PCGEs can be used without loss of their electricity generation performance with respect to the stress level applied on the PCGEs. At low stress level (around 0.76 MPa or lower), the PCGE showed almost insignificant degradation even after 2 million cycles whereas degradation occurred sooner (after 8 x 10(5) cycles) at higher stress levels (around 0.92 MPa or higher). The effects of impact loading on the durability of the PCGEs were also examined by X-ray photographs of the specimens.

Impact and cyclic shaking on loose sand properties in laminar box using gap sensors

This paper focuses on using high-frequency GAP-SENSORs (GSs), accelerometers, and load cells in a laminar shear box (LSB) filled with loose Toyoura sand to understand the effects of impact loads and cyclic shaking at 1-G on soil properties. The shear wave velocity at small strain (Vs) was calculated directly from first arrival reference using displacement time-history of two GSs under impact loading. Moreover, from first peak using the reduced deformation amplitude technique, damping ratio was calculated. In addition, shaking table tests were performed under harmonic loading with amplitude of acceleration inside the model ground varying from 0.02g to 1g. The frequencies of excitation varied from 1Hz to 10Hz. GSs and inside accelerometers were used to directly measure the outside lateral deformation and shear stress at different elevations of LSB, respectively. Results show that the shear modulus (G) and the damping ratio (D) behavior of model sand are generally consistent with the behavior presented by similar tests using only accelerometers. In addition, damping ratio increases as frequency loading increases. Characteristic changes in two shear stress components in shaking loading conditions were also investigated using high precision inside load cells.

Effect of High Loading Rate on SCC Behaviour of SUS304 Austenitic Stainless Steel

This study deals with the effect of intermittent impact loading on the SCC growth behaviour of SUS304 austenitic stainless steel. To this end, the Split-Hopkinson pressure bar (SHPB) experiments on SUS304 were performed first to establish the dynamic tensile stress-strain response at strain rates up to 700s-1. The analyses of dynamic stress intensity factors for wedge loading experiments on modified compact tension specimens, designated WLCT, were then performed by the finite element method. The SCC experiments with the intermittent impact loading for WLCT specimens of SUS304 by the use of the SHPB were mentioned and discussed as well.

Hopkinson bar techniques for the intermediate strain rate testing of bovine cortical bone

Detailed knowledge of the dynamic viscoelastic properties of bone is required to understand the mechanisms of macroscopic bone fracture in humans, and other terrestrial mammals, during impact loading events (e.g. falls, vehicle accidents, etc.). While the dynamic response of bone has been studied for several decades, high-quality data remain limited, and it is only within the last decade that techniques for conducting dynamic compression tests on bone at near-constant strain rates have been developed. Furthermore, there appears to be a lack of published bone data in the intermediate strain rate (ISR) range (i.e. 1-100 s(-1)), which represents a regime in which many dynamic bone fractures occur. In this paper, preliminary results for the dynamic compression of bovine cortical bone in the ISR regime are presented. The results are obtained using two Hopkinson-bar-related techniques, namely the conventional split Hopkinson bar arrangement incorporating a novel cone-in-tube striker design, and the recently developed wedge bar apparatus. The experimental results show a rapid transition in the strain rate sensitive behaviour of bovine cortical bone in the ISR range. Finally, a new viscoelastic model is proposed that captures the observed transition behaviour.

Investigation of Impact Compressive Mechanical Properties of Sandstone After as well as Under High Temperature

AbstractConducting experimental studies on the impact compressive mechanical properties of rock under the high temperature environment is of both theoretical value and practical significance to understanding the relationship between the rock under the effect of impact loads and the high temperature environment. Based on the Φ100 mm SHPB and the self-developed Φ100 mm high-temperature SHPB test devices, the impact compressive tests on the sandstone, whether cooling after high temperatures or under real-time high temperatures are carried out. As the test results indicate that since the two high-temperature ways of loading are different from each other, the impact compressive properties of sandstone, after as well as under high temperatures, show different variations along with changes in temperature. Under the effect of the same impact loading rate, there exists a clear critical temperature range in the impact compressive mechanical properties of sandstone after high temperature, and, near the critical temperature, there occurs a significant mutation in the impact compressive mechanical properties. Under high temperatures, however, the impact compressive mechanical properties follow an overall continuity of change except that there are slight fluctuations at individual temperatures.

Geometrical effects in the impact response of the aluminium honeycomb sandwich structures

Low-velocity impact tests have been conducted on sandwich beams and panels based on [0°, 90°] glass fibre-reinforced epoxy skins with an aluminium honeycomb core. The sandwich beams were placed on simple supports positioned at different separations to investigate the effect of target size on their impact response. Two thicknesses (13 and 26 mm) of honeycomb core were investigated. Following impact, damage within the beams was assessed by sectioning the samples and observing them under a low-power microscope. An energy-balance model was used to predict the maximum impact force for subsequent comparison with the experimental results. The energy-balance model was used to partition the energy absorbed during the impact event, giving an understanding of the energy absorption process. Finally, a limited number of tests have been conducted on square sandwich panels in order to investigate the effect of impact loading on their indentation behaviour. An examination of the cross-sections of impacted samples highlighted regions of core buckling and local plastic folding. At higher energies, damage in the form of localized fibre fracture was observed in the top skin close to the point of impact. The energy-balance model predicted the elastic response of the sandwich beams with reasonable success. The accuracy of the model decreased as damage became more extensive in the beams. It has been shown that the level of permanent indentation in both the beams and the square panels collapsed onto a single curve when the data are plotted against maximum impact force.

Effect of cyclic impact loading on the surface properties of flowable resin composites.

The aim of this study was to examine the effect of cyclic impact loading (CIL) on the surface properties of flowable resin composites for posterior restorations. Cavities were filled with one of four flowable resin composites—Clearfil Majesty LV, Estelite Flow Quick, Beautifil Flow Plus F00, or Unifil Loflow Plus—and photo-polymerized. Clearfil Majesty was used as a control. Specimens were subjected to in vitro CIL testing with a mechanical loading device. The CIL-generated defect in the resin composite was scanned and traced at 10,000, 20,000, 30,000, and 40,000 cycles with a profilometer (n=5). An image scanner and computer program were used to calculate the mean defect depth on each resin composite restoration. Data were statistically analyzed with ANOVA and the post-hoc Tukey test. All tested flowable resin composites showed more surface degradation than the control after 40,000 CIL cycles.

J2240301 単結晶シリコンの衝撃破壊試験([J224-03]『マイクロ・ナノ機械の信頼性』のための材料創製・測定・解析技術 シリコンの破壊と疲労)

Impact test of single crystal silicon was performed at room temperature and 200℃. We fabricated test chips that consists of four beams supporting central dead weight. It was mounted on an impact shuttle that freely falls on a steel base from different heights. Fracture probability of the test chip was plotted as a function of initial shuttle heights. The fracture probability curves did not differ by the environmental temperature in a range from room temperature to 200℃. Most of the beams cleaved at a stress concentration part. Regardless of the temperature rise up to 200℃, fracture made remained brittle same as at room temperature. We think this is due to impact loading effect that enhanced the brittleness.

Research on the Characteristics of Steel Frame Node under Explosive and Impact Load

With the characteristics of huge energy,short acting time and large destructiveness, Explosive and Impact Load leads a large punching force towards construction units. Once happened, it can cause serious of damaging effects. Therefore,the explosion protection performance of construction is being more and more concerned[1].The large finite element analysis software ABAQUS is being used to deal with numerical simulation of cross steel frame node, to analyses the response of the steel frame node and to discusses different steel material parameters on the influence of the nodes dynamic response under the effect of Explosive and Impact Load in this paper. According to conclusions, increase strength and modulus of elasticity of steel can reduce the damage of Explosive and Impact Load to construction. Meanwhile taking advantage of the function of transferring information between explicit processor and standard processor in ABAQUS, this paper analyses the effect of Explosive and Impact Load on steel frame node under low cyclic loading and concludes that it is harmful to the structural performance that the effect of Explosive and Impact Load can lower the ductility of the structure. According to the conclusion from the research on steel frame nodes characteristics under the effect of Explosive and Impact Load, this paper present that negative influence of Explosive and Impact Load should be taken fully into account, beneficial materials to explosion protection performance should be choosen and the corresponding measures to improve the ductility of structure should be taken to reduce structures degree of damage under Explosive and Impact Load in future structural design. All the research have a certain significance to the future structural design of explosion protection.

Effect of boundary conditions, impact loading and hydraulic stiffening on femoral fracture strength

Patient specific quantitative CT (QCT) imaging data together with the finite element (FE) method may provide an accurate prediction of a patient's femoral strength and fracture risk. Although numerous FE models investigating femoral fracture strength have been published, there is little consent on the effect of boundary conditions, dynamic loading and hydraulic strengthening due to intra-medullary pressure on the predicted fracture strength. We developed a QCT-derived FE model of a proximal femur that included node-specific modulus assigned based on the local bone density. The effect of three commonly used boundary conditions published in literature were investigated by comparing the resulting strain field due to an applied fracture load. The models were also augmented with viscoelastic material properties and subject to a realistic impact load profile to determine the effect of dynamic loads on the strain field. Finally, the effect of hydraulic strengthening was investigated by including node specific permeability and performing a coupled pore diffusion and stress analysis of the FE model. Results showed that all boundary conditions yield the same strain field patterns, but peak strains were 22% lower and fracture load was 18% higher when loaded at the greater trochanter than when loaded at the femoral head. Comparison of the dynamic models showed that material viscoelasticity was important, but inertial effects (vibration and shock) were not. Finally, pore pressure changes did not cause significant hydraulic strengthening of bone under fall impact loading.

Impact tolerance in mussel thread networks by heterogeneous material distribution

The Mytilidae, generally known as marine mussels, are known to attach to most substrates including stone, wood, concrete and iron by using a network of byssus threads. Mussels are subjected to severe mechanical impacts caused by waves. However, how the network of byssus threads keeps the mussel attached in this challenging mechanical environment is puzzling, as the dynamical forces far exceed the measured strength of byssus threads and their attachment to the environment. Here we combine experiment and simulation, and show that the heterogeneous material distribution in byssus threads has a critical role in decreasing the effect of impact loading. We find that a combination of stiff and soft materials at an 80:20 ratio enables mussels to rapidly and effectively dissipate impact energy. Notably, this facilitates a significantly enhanced strength under dynamical loading over 900% that of the strength under static loading.

A Comparison of the Human Lumbar Intervertebral Disc Mechanical Response to Normal and Impact Loading Conditions

Thirty-four percent of U.S. Navy high speed craft (HSC) personnel suffer from lower back injury and low back pain, compared with 15 to 20% of the general population. Many of these injuries are specifically related to the intervertebral disc, including discogenic pain and accelerated disc degeneration. Numerous studies have characterized the mechanical behavior of the disc under normal physiological loads, while several have also analyzed dynamic loading conditions. However, the effect of impact loads on the lumbar disc--and their contribution to the high incidence of low back pain among HSC personnel--is still not well understood. An ex-vivo study on human lumbar anterior column units was performed in order to investigate disc biomechanical response to impact loading conditions. Samples were subjected to a sequence of impact events of varying duration (Δt = 80, 160, 320, 400, 600, 800, and 1000 ms) and the level of displacement (0.2, 0.5, and 0.8 mm), stiffness k, and energy dissipation ΔE were measured. Impacts of Δt = 80 ms saw an 18-21% rise in k and a 3-7% drop in ΔE compared to the 1000 ms baseline, signaling an abrupt change in disc mechanics. The altered disc mechanical response during impact likely causes more load to be transferred directly to the endplates, vertebral bodies, and surrounding soft tissues and can help begin to explain the high incidence of low back pain among HSC operators and other individuals who typically experience similar loading environments. The determination of a "safety range" for impacts could result in a refinement of design criteria for shock mitigating systems on high-speed craft, thus addressing the low back injury problem among HSC personnel.

Numerical Analysis for Ferro Cement Panels Resisting Projectile Penetration with Different Initial Velocities

Resistance to penetration by high velocity projectiles through concrete target is an essential design parameter for fortification structures. Due to the expensive costs of field test experiments, numerical modeling is considered one of the most efficient procedures to predict the response of concrete panels under the effect of impact loads. The change in strain rate influences the material behavior. Studying this behavior needs experimental test. In this study, the experimental work is conducted to record the penetration depth through the concrete panels using the bullet at the industry. Two different panels are tested. Each panel has a different arrangement in the ferrocement layers. The finite element analysis (FEA) isused to model the concrete panels subjected to the penetration of the bullet. The results obtained by the FEA are compared with those obtained by the experimental work to verify the proposed finite element model. Different initial velocities of the projectile are set to study the response of the target. The penetration depth and the strain energy are compared for each panel. The difference between the penetration depth and the strain energy, can describe the influence of the strain rate on the target behavior. The performance of the concrete panel reinforced by the ferrocement isimproved to reduce the penetration of the bullet.

Dynamic Response Analysis of the Reinforced Concrete Column under the Effect of Explosive Impact Load

This paper does the data simulation analysis by using the large-scale finite element nonlinear ANSYS/LS-DYNA software. It chooses the MAT111(MAT-JOHNSON-HOLMQUIST -CONCRETE）concrete materials and the MAT3 (MAT-PLASTIC-KINEMATIC) reinforcement material model in ANSYS/LS-DYNA finite element software, builds the separating RC column finite element model, dynamically simulates the hurting process of RC column under the effect of explosive impact load, and mainly does research into the damage degree of RC column under different effects of explosive load of different peak pressures.

Formation of micro-grooves under impact loading in elliptical contacts with surface ridges

This paper is focused on the effect of impact loading on micro-deformation of asperities in elliptical elastohydrodynamic contacts. Based upon isothermal Newtonian numerical analyses, it is elucidated that a micro-groove, which appears in the ridge under impact loading in elliptical contacts, is brought about by two different mechanisms. One is the smooth surface local pressure difference across the virtual ridge and the other is the macroscopic pressure difference along the ridge. The formation of the micro-groove due to the former mechanism is influenced by the shape, size and orientation of the ridge, and the smooth surface pressure distribution depending on the initial impact gap and loading speed, and that due to the latter is markedly influenced by the loading speed.

Transverse impact and axial compression behaviors of glass/epoxy pipes subjected to seawater and impact loading

This article investigates the effects of seawater and impact loading on the impact behavior and compressive strength of impacted glass/epoxy composite pipes. The specimens were immersed into artificial seawater at laboratory conditions for 3, 6, 9, and 12 months. First, the impact tests were carried out on composite pipes at room temperature, and then, the axial compression tests were performed. The results of immersed samples were compared with that of reference specimens (dry). Seawater effect on the force–deflection behavior and failure mechanism is more than impact energy with increase in pipe diameter, while impact energy effect is more dominant than seawater effect for small diameters of the pipe. Compressive strength generally reduces with increase in seawater immersion time and specimen diameter except for the highest diameter.

Determination of peak deflections from human surrogates using chestbands in side impact tests

To understand the biomechanics of the human body in motor vehicle environments, physical models including anthropomorphic test devices (ATD) and biological models (postmortem human surrogates) are used, and sled tests are conducted. Deflection is often used as a biomechanical variable to characterize the effects of impact loading and derive injury criteria. The objective of the present study was to evaluate different techniques and recommend a methodology to determine the peak thorax and abdominal deflections from temporal contours using chestbands in oblique lateral impacts. The side impact ATD WorldSID representing human surrogates was positioned on a seat. The seat was rigidly fixed to the platform of an acceleration sled. The oblique load-wall fixed to the sled consisted of separate and adjustable plates to contact the shoulder, thorax, abdomen, and pelvis. Two 59-gage chestbands were wrapped on the thorax and abdomen. Tests were conducted at low, medium, and high velocities (3.4, 6.7, and 7.5m/s) and three methods, termed the spine-sternum, bilateral, and spine-box, were used to determine the global peak deflection and its angulation. Results indicated that all three methods produced very similar angulations, for all velocity tests, and at both thorax and abdominal regions. However, maximum deflections were the lowest in the spine-sternum, followed by bilateral and spine-box methods, with one exception. Based on the development of deflection contours, locations used in the definitions of the origin, and accuracy in identifying critical locations/points in time-varying contours, results of the present study indicate that the bilateral method is the optimum procedure to determine the oblique peak deflection vector in biomechanical tests.

Impact Characteristics of CFRP Hat-Shaped Members According to Changes in Outer Layer under the Hygrothermal Environment

CFRP composite material, which is reinforced with carbon fiber, features superior heat and corrosion resistance, and these benefits enables the gradual applications on aerospace industries and sports-entertainment business. However, guarantee on superior strength and rigidity on harsh condition, such as hot moisture environment and collision load is extremely difficult. Therefore, in study moisture absorption test was conducted until complete moisture absorption in test specimen using hygrothermal heat chamber to evaluate strength degradation in CFRP composite under hygrothermal environment. As a result, the effect of moisture absorption and impact loads of approximately 50% reduction in strength are shown.