Crush Forces Research Articles

Energy Absorption of Aluminium Extrusions Filled with Cellular Materials Under Axial Crushing: Study of the Interaction Effect

This investigation focuses on the interaction effect during the quasi-static axial crushing of circular and square thin-walled aluminium extrusions filled with polymeric foam or cork. The increment in the absorbed energy due to interactions between materials was assessed using a validated numerical model calibrated with experimental material data. Simulations were run with variable cross-section dimensions, thickness, and foam density. The results were used to adjust the parameters of design formulas to predict the average crush forces of foam- and cork-filled thin-walled tubes. The analysis of the energy dissipation per unit volume revealed that the highest increments due to the interaction between materials appeared in the foam-filled square extrusions. Energy dissipation increased with higher density foams for both cross-sections due to a stronger constraint of the aluminium walls, and thus a reduction of the folding length. Thinner tube walls also delivered a higher improvement in the energy dissipation per unit volume than those with thicker walls. The contribution of friction was also quantified and investigated.

Effects of external crushing forces on a novel below-the-knee vascular implant.

The Tack Endovascular System® is a novel vascular implant designed to focally treat dissections with low radial force and minimal metal burden. As there are currently no approved below-the-knee (BTK) implants in the USA, a unique, 3-stage model was developed to characterize crush deformation and fracture potential of the Tack Endovascular System in BTK arteries. First, 35 Tack® implants were deployed bilaterally in the posterior tibial, anterior tibial, and peroneal arteries of 3 cadavers, and clinically relevant external forces were applied to simulate BTK crushing deformation including focal load, leg crossing, and leg bending. Intravascular ultrasound images of the implanted vessels were used to assess the magnitude of artery deformation. Outputs of the cadaver testing were input into a finite element analysis (FEA) model to determine the appropriate conditions for subsequent bench testing. Tack implants were then subjected to increasing crush forces at 30Hz for up to 650,000 cycles at 25% flat plate deformation within the worst-case FEA test condition. Crush deformation across all arteries ranged from 0% to 23.1%. The posterior tibial artery and large male cadaver exhibited the most vulnerability to external crush forces, while the small female model exhibited the most resistance. No fractures were observed during cadaver or bench testing. This study characterized deformation forces in tibial arteries during various loading conditions. Tack implants withstood the loading conditions without fracture within the limits of this ex-vivo human vascular model and in-vitro bench testing.

Correlation between retinal ganglion cell loss and nerve crush force-impulse established with instrumented tweezers in mice

ABSTRACT Objectives: Rodent models of optic nerve crush (ONC) have often been used to study degeneration and regeneration of retinal ganglion cells (RGCs) and their axons as well as the underlying molecular mechanisms. However, ONC results from different laboratories exhibit a range of RGC injury with varying degree of axonal damage. We developed instrumented tweezers to measure optic nerve (ON) crush forces in real time and studied the correlation between RGC axon loss and force-impulse, the product of force and duration, applied through the instrumented tweezers in mice. Methods: A pair of standard self-closing #N7 tweezers were instrumented with miniature foil strain gauges at optimal locations on both tweezers’ arms. The instrumented tweezers were capable of recording the tip closure forces in the form of voltages, which were calibrated through load cells to corresponding tip closure forces over the operating range. Using the instrumented tweezers, the ONs of multiple mice were crushed with varied forces and durations and the axons in the immunostained sections of the crushed ONs were counted. Results: We found that the surviving axon density correlated with crush force, with longer duration and stronger crush forces producing consistently more axon damage. Discussion: The instrumented tweezers enable a simple technique for measurement of ONC forces in real-time for the first time. Using the instrumented tweezers, experimenters can quantify crush forces during ONC to produce consistent and predictable post-crush cell death. This should permit future studies a way to produce nerve damage more consistently than is available now.

Parametric design of multi-cell thin-walled structures for improved crashworthiness with stable progressive buckling mode

Thin-walled single and multi-cell structures are an ongoing topic of interest in the field of crashworthiness, due to their wide range of applications in automotive and aerospace industry as lightweight energy-absorbing structures in crash environments. This work presents a new five-cell cross-section that merges high performance multi-cell and twelve-edge cross-sections from previous research, and compares its performance to four- and nine-cell square cross-sections. Super Folding Element (SFE) theory and Finite Element Analysis (FEA) in LS-DYNA are used to analyze cross-sections and found to have good agreement. The LS-DYNA environment is validated with physical testing. The geometry of the cross-sections is varied in order to find maximal values of the performance parameters specific energy absorption (SEA) and crush force efficiency (CFE) under stable progressive buckling mode and constraints for manufacturability. The nine- and five-cell cross-sections ultimately out-perform the four-cell cross-section, with the nine-cell having the highest SEA and CFE, though the five-cell design has a significantly lower (47%) mean crush force (Pm) for only an 11% and 14% loss in SEA and CFE respectively. As a final refinement, the geometry was varied across these two high-performing cross-sections to create equivalent mean crush forces to the four-cell cross-section, which showed the five-cell cross-section to have an improved SEA and better mass efficiency over the nine-cell under a mean crush force constraint.

Comparative analysis of energy absorption behavior of tapered and grooved thin-walled tubes with the various geometry of the cross section

ABSTRACTIn this paper, Crush force efficiency (CFE), Specific Energy Absorption (SEA), Energy Absorption per Crush Length (Ecl), Maximum and average crush forces of straight and grooved tapered thin-walled tubes with various cross-section shapes (circle, ellipse, square, rectangle, hexagon, and octagon) have been studied. The effects of taper, the groove (as initiator) and their interaction have been presented in the current study using Finite Element Method as a numerical method. The tubes have the same volume, height, average cross-section area, thickness and material and have been subjected to axial and oblique dynamic loading. The results of simulations show that the section's geometry, taper and groove addition have a significant effect on energy absorption behavior and the hexagon cross section have better energy absorption behavior compared with other considered geometries. On the other hand, it was found that the behavior of these structures could improve against dynamic axial and oblique impact loading with the cost-effective geometry modifications. These results could help to improve and choose appropriate energy absorber structure based on desirable crush force and energy absorbing characteristics.

Behaviour of passenger cars on impact with underride guards

Much experience has been gathered on the impact behaviour of passenger cars crashing against flat barriers. This is quite different from impacting underride guards at the rear end of commercial vehicles. The side members in the car's front structure are the main energy absorbing structural elements, thus it is of considerable significance whether they hit on the underrider beam. Thirty–four clash tests were carried out in order to measure impact forcer and deformations. The quadstatic crush forces of simplified side members can be calculated by approximation on the basis of many experimental results. A ratio of crash to crush forces was found from dynamic impact and static crush tests. The frontal impact of a passenger car on a flat barrier was simulated by crashing a simplified structural model consisting of an engine, gearbox, and front–axle, etc. The required strength of an underride prevention device can be found from the deformation resistance of the ramming car's front structure. The weight of the commercial vehicle carrying the underride guard has little influence on the impact force and deformation because as the kinetic energy to be absorbed does not decrease in proportion as the commercial vehicle's weight is reduced and, because of its inertia, the vehicle hardly moves until the peak clashing load is reached. Quasistatic strength requirements are presented as an aid in the design of underride guards.

Response of Filled Thin-Walled Square Tubes to Axial Impact Load

This paper presents the results of an investigation into the response of thin-walled square (60x60 mm and 76x76 mm) tubes made from mild steel filled with four different fillers; aluminium foam (Cymat 7%), two types of aluminium honeycomb and polyurethane foam to quasi-static and dynamic axial impact load. The energy absorption characteristics of the foam-filled tubes are compared to that of a hollow tube, through efficiency calculations. The tubular structures are subjected to axial impact load generated by drop masses of 320 kg and 390 kg released from a height ranging between 2.1 m to 4.1 m. Footage from a high speed camera is used to determine the average crush forces exerted by each specimen. The results show that the fillers have insignificant effects on the initial peak forces based on the quasi-static results but increase the overall mean crushed force. The findings also indicate that the fillers affect at times the size of the lobe formed thus compromising the energy absorption capacity of the tube.

Analytical and experimental studies on quasi-static axial crush behavior of thin-walled tailor-made aluminum tubes

In this paper, the crush behavior of segmented circular tubes, made of aluminum alloy 6061 and subjected to quasi-static axial loading, has been analytically and experimentally investigated. Crush behavior of these tubes was modeled by integrating available analytical models and superposition principle. In the certain overall length of segmented circular tubes, effects of changing the wall thickness and length of each segment on the energy absorption characteristics have been evaluated. One successful approach toward obtaining lightweight energy absorbers with high energy absorption capacity is the use of thin-walled Tailor-Made Tubes (TMTs). In these tubes, the thickness and mechanical properties of the wall vary along the length of the tube. Applying these tubes; crush force can be controlled by changing the length and thickness of each tube segment, improving the performance of energy absorbing systems. Results of this research showed that Tailor-made tubes have higher energy absorption capacity at identical crush lengths, and they can absorb more energy per unit weight compared to simple tubes with constant wall thickness and mechanical properties. Moreover, for the same specific energy absorption, the TMTs exhibit a considerable reduction in the magnitude of the mean and initial maximum crush forces. With the use of TMTs, the maximum crush force shifts to the end of the crush range, reducing the exerted deceleration on occupants and equipments. Comparing mean crush force and specific energy absorption obtained by analytical and experimental approaches, it was observed that combining current analytical models with superposition principle can prepare a set of analytical formulations to predict TMTs crush characteristics within an acceptable proximity.

Modelling and analysis of the crush zone of a typical Australian passenger train

In this paper, a three-dimensional nonlinear rigid body model has been developed for the investigation of the crashworthiness of a passenger train using the multibody dynamics approach. This model refers to a typical design of passenger cars and train constructs commonly used in Australia. The high-energy and low-energy crush zones of the cars and the train constructs are assumed and the data are explicitly provided in the paper. The crash scenario is limited to the train colliding on to a fixed barrier symmetrically. The simulations of a single car show that this initial design is only applicable for the crash speed of 35 km/h or lower. For higher speeds (e.g. 140 km/h), the crush lengths or crush forces or both the crush zone elements will have to be enlarged. It is generally better to increase the crush length than the crush force in order to retain the low levels of the longitudinal deceleration of the passenger cars.

3D/1D 하이브리드 유한요소 모델을 이용한 동력 분산형 차세대 고속열차 전체차량의 충돌 해석

Abstract : In this paper, collision analysis of the full rake for the Next Generation High-speed EMU is conducted using a 3D/1D hybrid model, which combines 3-dimensional (3D) front-end structure of finite element model and 1-dimensional (1D) multi-body dynamics model in order to analyze train collision with a standard 3D deformable obstacle. The crush forces, passengers’ accelerations and energy absorptions of a full rake train can be easily obtained through a simulation of a 1D dynamics model composed of nonlinear springs, dampers and masses. Also the obtained simulation results are very similar to those of a 3D model if an overriding behavior does not occur during collision. The standard obstacle in TSI regulation has been changed from a rigid body to a deformable body, and therefore 3D collision simulations should be conducted because their simulation results depends on the front-end structure of a train. According to the obstacle collision analysis of this study, the obstacle collides with the driver’s upper structure after overriding over the front-end module. The 3D/1D hybrid model is effective to evaluate a main energy-absorbing module that is frequently changed during design process and reduce the need time of the modeling and analysis when compared to a 3D full car body.

Failure Mechanisms and Energy Absorption in Composite Elements under Axial Crush

Test methods are presented to determine failure modes and energy absorption properties of composite crash structural elements from quasi-static tests on chamfered carbon fabric/epoxy tube segment specimens under axial compression loads. High speed film and CT scans of failed specimens are used to identify trigger mechanisms, failure mode evolution at the crush front and failure processes during steady crushing. FE models of failure were developed which could be the basis for materials selection and design procedures for crashworthy composite structures. These are based on meso-scale composites ply damage models combined with cohesive interfaces to represent delamination failures, which damage and fail when the interface fracture energy is reached. The models are implemented in an explicit FE code and parameters for the ply damage and delamination models were obtained from related materials test programmes. The FE models were applied to simulate axial crushing in tube segments and C-channels, showing good predictions of measured peak forces at failure initiation, steady crush forces and total energy absorption.

Historical view and experiences with crush test for light weight packages

AbstractThe crush test for light weight and low density type B packages was introduced for the first time into the 1985 edition of the International Atomic Energy Agency (IAEA) transport safety regulations. In the early 1970s, the need for an additional mechanical test besides or instead of the well known 9 m drop test was deliberated. Various authors and test facilities, including BAM and Sandia National Laboratories (SNL), were able to prove that the level of safety provided by IAEA drop and puncture tests in the regulations did not protect against dynamic crush forces to smaller packages. As early as the third PATRAM symposium held in 1971 (Richland, WA, USA), Robert F. Barker asked for ‘…a more strenuous crushing test for protecting small, light weight packages…’. BAM developed from research activities a proposal as to which types of packages should be subject to crush tests and how the crush tests should be performed, which was presented at the 5th PATRAM symposium held in 1978 (Las Vegas, NV, USA). ...

Effects of pre-strain and bake-hardening on the crash properties of a top-hat section

The effects of pre-strain on the crushing properties of a crash-box structure are reported for two Advanced High Strength Steels produced by ArcelorMittal (Dual-Phase DP600 and Transformation Induced by Plasticity TRIP780 steels). In addition, the effect of a bake-hardening treatment is studied on the TRIP780 steel. The material's behaviors have been determined in tensile loading in a wide range of strain-rates ( 8 × 10 − 3 s − 1 ≤ ε ˙ ≤ 10 3 s − 1 ) including strain-rate jump tests from quasi-static to dynamic loading. These interrupted tests allow us to characterize the effect of the (quasi-static) forming process on the subsequent dynamic behavior associated to the crash event. A phenomenological visco-plastic model, based on the evolution of an internal variable, has been implemented in PAMCRASH using a user-defined subroutine in order to simulate the crushing of the crash-boxes. A simple approach is proposed to account for the bake-hardening treatment in numerical simulations. A good correlation between experimental and predicted mean crush forces is obtained.

The effect of geometrical parameters on the energy absorption characteristics of thin-walled structures under axial impact loading

In this study, the crush behaviour of thin-walled straight and conical shell structures was systematically determined for various absorber designs and investigated comparatively under axial impact loading. The main parameters in the design of these structures are cross-section geometry, wall thickness and semi-apical angle. Several cross sections have been studied: circular, square and hexagonal. In the finite element simulations, these designs were fixed at one end and impacted by a rigid wall from the other with specified mass and velocity giving the required impact energy according to the European regulation ECE R29 by using explicit finite element code LS-Dyna. After crash simulations, energy absorption characteristics and crush forces were obtained for each crush element having different cross sections, wall thicknesses and semi-apical angles. Peak crush force, mean crush force, crush force efficiency and specific energy absorption (SEA) were calculated for a deformation length of 100 mm. In all cases it was found that tubes were crushed progressively. The results of the simulations showed that the square cross-sectioned energy absorber has the lowest crush force efficiency among three cross-section geometries. The crush force efficiency was found to be the highest for the circular absorber which has a semi-apical angle of 12.5° and a wall thickness of 2 mm. Finally, the peak crush forces were lowered by creating blanks and corrugations.

Theoretical analysis for axial crushing behaviour of aluminium foam-filled hat sections

A theoretical analysis was performed to predict the crushing behaviour of aluminium foam-filled single hat and double hat sections subjected to axial compression. The experimental results and superfolding element theory were used to create deformation models for the aluminium foam contained in the hat sections, and several assumptions were made for the theoretical analysis. According to the energy method and superfolding elements theory, the mean crushing force and the interactive effect were theoretically predicted for the axial compression of the aluminium foam-filled hat sections. The final formula specified the relationship between the mechanical characteristics of the aluminum foam and the height of the superfolding element. The mean crush forces and the interactive effect predicted by the theoretical analysis were in good agreement with the experimental results. The theoretical prediction results showed that the interactive effect was mainly from the aluminium foam.

Blunt Trauma to the Abdomen

Serious injuries remain the number one cause of death among American children. Major trauma is responsible for more than 50% of the mortality in children between the ages of 1 and 14 years. The majority of these life-threatening injuries result from blunt trauma rather than from penetrating injuries, which are much more common in adults. The most common causes of blunt trauma to children are: motor vehicle crashes when a child is either a pedestrian, bicycle rider, or automobile occupant; falls from windows or farm buildings and machinery; and house fires. Children die in motor vehicle crashes as a result of multiple systems injuries, of which the most serious is to the head.Major blunt trauma to the abdomen frequently is associated with this series of injuries. This is a difficult injury to evaluate because often there are few signs of external damage to reflect the life-threatening trauma to internal abdominal organs. In addition, as noted previously, children commonly have associated head injuries and are unconscious at the time of evaluation, which makes early diagnosis and definitive treatment even more difficult, often resulting in disastrous delays in specific treatment.The pathophysiology of blunt injuries to the abdomen results from energy transfer of compression and crush forces or from rapid deceleration/acceleration forces, which cause shearing stresses within the abdomen.

Blunt Trauma to the Abdomen

Serious injuries remain the number one cause of death among American children. Major trauma is responsible for more than 50% of the mortality in children between the ages of 1 and 14 years. The majority of these life-threatening injuries result from blunt trauma rather than from penetrating injuries, which are much more common in adults. The most common causes of blunt trauma to children are: motor vehicle crashes when a child is either a pedestrian, bicycle rider, or automobile occupant; falls from windows or farm buildings and machinery; and house fires. Children die in motor vehicle crashes as a result of multiple systems injuries, of which the most serious is to the head. Major blunt trauma to the abdomen frequently is associated with this series of injuries. This is a difficult injury to evaluate because often there are few signs of external damage to reflect the life-threatening trauma to internal abdominal organs. In addition, as noted previously, children commonly have associated head injuries and are unconscious at the time of evaluation, which makes early diagnosis and definitive treatment even more difficult, often resulting in disastrous delays in specific treatment. The pathophysiology of blunt injuries to the abdomen results from energy transfer of compression and crush forces or from rapid deceleration/acceleration forces, which cause shearing stresses within the abdomen.

Safety restraint usage in fatal motor vehicle crashes

In 1987, following implementation of the Washington safety restraint mandatory usage law, collision statistics indicated an increase in motor vehicle crashes in which occupants had died while utilizing safety restraints. Because of concerns expressed by restraint use law advocates, a “Fatal Collision Research Team” was established to evaluate and reconstruct collisions in which restrained occupants had died. Collisions were analyzed over a three-year period and included 337 crashes involving 1,058 occupants, of whom 446 died. The team analyzed fatal collisions involving restrained occupants and documented restraint usage as well as severity of the crash. Crash severity was measured using either the Collision Deformation Classification (CDC) system, which defines the extent of crush to the vehicle, and/or intrusion into the passenger occupant area, or by measuring deceleration forces (delta v) acting on the vehicle, where sufficient data existed to do so. The survivability of the crash was determined individually for each occupant and independently of whether the occupant lived or died, as well as whether the occupant was restrained or not. The major findings were: (i) that in the majority of cases where a restrained occupant died, the fatality can be attributed to the extent of vehicle crush and deceleration forces, i.e. the crash forces and dynamics made the crash nonsurvivable, and (ii) restraint misuse seemed not to be a major contributory factor in fatal crash injuries.