Crash Situations Research Articles

Optimization of car frontal protection system

Aim of the current study is to design the extra frontal protection system of a car satisfying the requirements of directive 2005/66/EC of the European Parliament and of the Council. The car frontal protection system is treated as additional energy absorbing element. An analysis of a car-pedestrian crash situation is performed by use of explicit Finite Element Analysis solver and the following stiffness analysis with implicit Finite Element Analysis solver. For modeling response surface and search for optimal solution the LS-OPT software is utilized and some comparative simulations are performed by use of MATLAB. The experimental validation of the models designed is performed.

Modular Modelling of Stress-Strain Behaviour of Ferritic Steel Grades in Strain Rate Ranges Relevant for Automotive Crash Situations

Modular Modelling of Stress-Strain Behaviour of Ferritic Steel Grades in Strain Rate Ranges Relevant for Automotive Crash Situations

Toward Developing an Approach for Alerting Drivers to the Direction of a Crash Threat

This study explored the potential for auditory and haptic spatial cuing approaches to alert drivers to the direction of a crash threat. For an automobile equipped with multiple crash avoidance systems, effective cuing of the crash threat direction may help the driver avoid the crash. Because the driver may not be looking in the direction of a visual crash alert, nonvisual crash alerts were explored as an additional means of directing attention to a potential crash situation. In this in-traffic study, 32 drivers were asked to verbally report alert direction in the absence of any crash threats. Driver localization accuracy and response time were examined as a function of eight alert locations surrounding the vehicle and four directional alert approaches (auditory, haptic, haptic and auditory, and haptic and nondirectional auditory). The auditory directional alert approach used four speakers and broadband alert sounds, and the haptic directional alert approach used vibrations generated at various locations on the bottom of the driver's seat. Overall, relative to the auditory alert approach, the three approaches that included the haptic seat alert component reduced correct localization response times by 257 ms and increased percentage correct localization from 32% to 84%. These results suggest that seat vibration alerts are a promising candidate for alerting drivers to the direction of a crash threat. These findings should facilitate developing a multimodality integrated crash alert approach for vehicles equipped with multiple crash avoidance systems.

Modeling initial contact dynamics during ambulation with dynamic simulation

Ankle-foot orthoses are frequently used interventions to correct pathological gait. Their effects on the kinematics and kinetics of the proximal joints are of great interest when prescribing ankle-foot orthoses to specific patient groups. Mathematical Dynamic Model (MADYMO) is developed to simulate motor vehicle crash situations and analyze tissue injuries of the occupants based multibody dynamic theories. Joint kinetics output from an inverse model were perturbed and input to the forward model to examine the effects of changes in the internal sagittal ankle moment on knee and hip kinematics following heel strike. Increasing the internal ankle moment (augmentation, equivalent to gastroc-soleus contraction) produced less pronounced changes in kinematic results at the hip, knee and ankle than decreasing the moment (attenuation, equivalent to gastroc-soleus relaxation). Altering the internal ankle moment produced two distinctly different kinematic curve morphologies at the hip. Decreased internal ankle moments increased hip flexion, peaking at roughly 8% of the gait cycle. Increasing internal ankle moments decreased hip flexion to a lesser degree, and approached normal at the same point in the gait cycle. Increasing the internal ankle moment produced relatively small, well-behaved extension-biased kinematic results at the knee. Decreasing the internal ankle moment produced more substantial changes in knee kinematics towards flexion that increased with perturbation magnitude. Curve morphologies were similar to those at the hip. Immediately following heel strike, kinematic results at the ankle showed movement in the direction of the internal moment perturbation. Increased internal moments resulted in kinematic patterns that rapidly approach normal after initial differences. When the internal ankle moment was decreased, differences from normal were much greater and did not rapidly decrease. This study shows that MADYMO can be successfully applied to accomplish forward dynamic simulations, given kinetic inputs. Future applications include predicting muscle forces and decomposing external kinetics.

Application of Switching Control for Automatic Pre-Crash Collision Avoidance in Cars

In recent years, a number of European Commission funded projects have investigated how the objective of increasing pedestrians' safety can be attained by means of intelligent driver assistance systems. The results already available show that, while in the long range case, a warning system, to alert the driver as soon as a vulnerable road user (VRU) is detected and classified by the sensors, can be sufficient to reduce the number of accidents, an active intervention system is mandatory in pre–crash situations. The generation of collision avoidance manoeuvres appears to be a suitable application for switching control. In this paper, in particular, an automatic pre–crash collision avoidance strategy for cars based on sliding mode control is presented. It produces a collision avoidance manoeuvre, if feasible, or, otherwise, an emergency braking to reduce the energy at the impact. Experimental results based on a scaled radio–controlled car are provided.

Structural optimization of modular product families with application to car space frame structures

This paper extends classical structural optimization from single-product optimization to optimization of a whole family of products that have common modules. It integrates the family commonality problem with the finite element models of the structures. A general mathematical frame where optimization is seen as a balance between cost and performance is given. The most obvious cost function is mass, while performance is taken to be a weighted sum of compliances. As a case study, a car product family consisting of three products is presented. These three products are a base model, a seven-seat version, and a pickup version. The study shows how optimal results are effected by requiring modules to be shared between products. Loads emanating from prescribed acceleration fields that simulate crash situations are used. This is a proof-of-concept paper which is a first step toward including more general manufacturing costs than mass and performance measures other than compliance.

Influence of Seat Geometry and Seating Posture on NICmax Long-Term AIS 1 Neck Injury Predictability

Objective. Validated injury criteria are essential when developing restraints for AIS 1 neck injuries, which should protect occupants in a variety of crash situations. Such criteria have been proposed and attempts have been made to validate or disprove these. However, no criterion has yet been fully validated. The objective of this study is to evaluate the influence of seat geometry and seating posture on the NIC max long-term AIS 1 neck injury predictability by making parameter analyses on reconstructed real-life rear-end crashes with known injury outcomes. Methods. Mathematical models of the BioRID II and three car seats were used to reconstruct 79 rear-end crashes involving 110 occupants with known injury outcomes. Correlations between the NIC max values and the duration of AIS 1 neck injuries were evaluated for variations in seat geometry and seating posture. Sensitivities, specificities, positive predictive values, and negative predictive values were also calculated to evaluate the NIC max predictability. Results. Correlations between the NIC max values and the duration of AIS 1 neck injuries were found and these relations were used to establish injury risk curves for variations in seat geometry and seating posture. Sensitivities, specificities, positive predictive values, and negative predictive values showed that the NIC max predicts long-term AIS 1 neck injuries also for variations in seat geometry and seating postures. Conclusion. The NIC max can be used to predict long-term AIS 1 neck injuries.

Crash management using advanced aluminium extrusion-based solutions

Structural components such as bumper systems made from formed, high-strength aluminium extrusions have been successfully used for several decades. Recent trends in pedestrian safety and the focus on high-speed crash situations call for new design concepts.

Pedestrian lower limb injury criteria evaluation

In the field of pedestrian injury biomechanics, knees and lower legs are highly recruited during crash situations, leading to joint damage and bones failures. This paper shows how numerical simulation can be used to complete injury mechanism analysis and then to postulate on a knee injury criteria in lateral impact. It focuses on relationships between ultimate lateral bending and shearing at the knee level and potential ligament damage, based on subsystem experimental tests. These ultimate knee lateral bendings and shearings for potential failure of ligaments (posterior cruciate, medial collateral, cruciates and tibial collateral) were estimated at 16° and 15 mm in pure lateral shearing and bending impact tests respectively. Then this methodology was applied on a full test of pedestrian impact.

Using a finite element model to evaluate human injuries application to the HUMOS model in whiplash situation.

In the field of numerical simulation, the finite element method provides a virtual tool to study human tolerance and postulate on potential trauma under crash situations, particularly in case of whiplash trauma. To show how medical and biomechanical interpretations of numerical simulation can be used to postulate on human injuries during crash situations. This methodology was applied to whiplash trauma analysis. A detailed analysis of kinematics of joints, stress level in hard tissues, and strain level in soft tissues was used to postulate on chronology and patterns of injury. Data were compared with published biomechanical and clinical studies of whiplash. Although many in vitro and in vivo studies have been conducted to investigate whiplash cervical injury, and despite the number of finite element models developed to simulate the biomechanical behavior of the cervical spine, to date, there are only limited finite element models reported in the literature on the biomechanical response of the whole cervical spine in these respects. A complete finite element model of the human body (HUMOS) build in a sitting position in a car environment was created to investigate injury mechanisms and to provide data for automotive safety improvements. It includes approximately 50,000 elements, including descriptions of all bones, ligaments, tendons, skin, muscles, and internal organs. A 15-g whiplash injury was simulated with the HUMOS model. The model predicted cervical motion segment kinematics, deformations of disks and ligaments, and stresses in bone. Model output was then compared with experimental and clinical whiplash literature. In term of kinematics during the chronology of whiplash, two injury phases were identified: the first was hyperextension of the lower cervical spine (C6-C7 and C5-C6) and mild flexion of the upper cervical spine(C0-C4). The amount of upper cervical flexion was 15 degrees from C0 to C4. The second phase was hyperextension of the entire cervical spine. Potential patterns of ligamentous injuries were observed; the anterior longitudinal ligament experienced the most strain (30%) at the lower cervical spine at the time of lower cervical extension and the interspinous ligament experienced the most strain (60%) at the time of upper cervical flexion. Von Mises stresses in bone do not exceed 15 Mpa, which is largely under injury levels reported in the literature. CONCLUSIONS.: This study reports a methodology to describe and postulate on human injuries based on finite element model analysis. The output of the HUMOS model in the context of whiplash shows a strong correlation with clinical and experimental reported data. HUMOS shows promise for the modeling of other types of trauma as well.

Compatibility between passenger vehicles and road barriers during oblique collisions

In the European and US testing procedures for road barriers, vehicles are specified for the tests essentially by their mass properties. However, vehicles with similar mass can behave quite differently during a crash event. For the specific crash situation with the roadside restraint systems, e.g. W-beam guardrail, cable barriers, etc., the vehicle structure has to be compatible with the road restraint systems in geometry and crash stiffness to ensure safe operation during the interactions of vehicles and road barriers. The goal of this paper is to make a parametric investigation for the geometric compatibility between the compact passenger vehicles and the road barriers. The Finite Element model Ford Festiva and a weak-post W-beam guardrail were used for analyzing the oblique impact situation with a high impact speed and a small angle. For this specific situation the dynamic responses of the vehicle and the guardrail during impacts were investigated to study their structural interactions. The simulation results of the modified vehicle model and guardrail model were reasonable in comparison with the crash test data under the similar impact conditions.

On the Response of Stitched Woven S2-Glass/Epoxy Composites to High Strain Rate Compression Loading

Experimental investigations were carried out to understand the response of stitched/unstitched S2-Glass/SC-15 epoxy composites to high strain rate compression loading using a Split Hopkinson Pressure Bar set-up. Fifteen layers of plain weave S2-glass fabric were used to fabricate stitched/unstitched laminates with a low viscosity room temperature curing SC-15 epoxy resin system. For stitching, a 3-cord Kevlar thread was used. The fabric preforms were stitched through the thickness in a lock-stitch pattern, maintaining a pitch of 6 mm. The fabric was stitched along the length and width, forming a 25.4 mm stitch grid. Four different types of samples were considered. Sample configuration was designated according to the location of the stitch line with reference to the loading direction. Dynamic and static responses of the laminate under compression were compared. Failure modes were studied using optical microscopy. For high strain rate loading, samples of dimension 22.5 × 22.5 × 9.5 mm were tested at five different pressure settings of the Hopkinson Bar Set-up. Results were analysed in terms of peak stress, strain at peak stress, modulus and failure modes. Results of the study showed that, under higher strain rates loading, the stitched laminates exhibited a confining effect. The primary mode of failure for unstitched samples was fibre microbuckling with multiple delaminations. For stitched samples, fibre microbuckling and micro-delaminations were the major modes of failure and were contained within the bounds of the stitch. Overall, stitched laminates will provide increased damage resistance, which will prove very crucial under crash situations.

A comparison of the crash performance of three-spoke and four-spoke steering wheel armatures during impact loading

This research focuses on the crash performance of three-spoke and four-spoke aluminum steering wheel armatures using finite element methods. Finite element model verification was completed with a limited number of experimental tests investigating impacts between a rigid plate and both types of steering wheel armatures. An acceptable correlation between the experimental testing observations and numerical simulation results was observed which suggests that information obtained from finite element simulations can be used to assess the crashworthiness of the armatures during impact. Twenty-five numerical simulations were conducted for both the three-spoke and the four-spoke armature models under different impact conditions (investigating variations in the column angle and wheel angle). The simulations have shown that both steering wheel armatures absorb more energy under low wheel angles and the specific energy absorption for the four-spoke armature is generally higher than that of the three-spoke armature. These observations provide an understanding into the characteristics of energy management in crash situations for the two armature designs.

Observations on the energy absorption characteristics of a three-spoke steering wheel armature during impact

This research deals with experimental and finite element simulation of impacts occurring between a rigid plate and an aluminium three-spoke steering wheel armature to investigate the energy absorption capabilities of the armature. A limited number of experimental tests were conducted to validate a numerical model of the armature. An acceptable correlation between the experimental testing observations and numerical simulation results was observed for this highly non-linear problem. The numerical model was used to investigate the energy absorption abilities of the armature with variations in the impact location (wheel angle) and orientation of the armature (column angle). The finite element simulations have illustrated that the hub region is the location where most energy due to plastic deformation in the structure is absorbed. These results are very dependent upon the location of impact and the armature orientation. These observations provide an understanding into the characteristics of energy management in crash situations for the steering wheel armature.

Processing and Characterization of Porous Aluminum

Aluminum foams are now being introduced into automotive industry to reduce weight, to absorb energy in crash situations and to carry sound or heat absorbing functions. In the present study, a novel Spark Plasma Sintering (SPS) process for producing porous aluminums with controlled pore size and porosity and superior energy absorption has been developed. Experimental procedures included the mixing of starting powders, compacting, SPS sintering and leaching out of the space-holding particles. Porous aluminums with various porosities and a wide range of pore size distributions can be produced by the SPS process. Optical microscopy, scanning electron microscopy (SEM) and quantitative image analyses were used to characterize the porous aluminums. Compressive tests were carried out on the aluminum foams to evaluate the mechanical properties.

Aluminium and magnesium castings ? experimental work and numerical analyses

Abstract The long-term objective of this work is to develop design and modelling tools that allow the structural behaviour of thin-walled cast components to be predicted when subjected to static and dynamic loads such as in crash situations. The approach consists of the following ingredients: casting of generic geometry relevant for automotive design, component and materials testing, constitutive modelling and validation simulations using the finite element method. Here, HPDC components of both AM60 and AlSi7Mg have been subjected to axial crushing and 3-point bending. An existing elastoplastic constitutive equation has been calibrated and evaluated based on material tests. Next, validation analyses of the generic structural components subjected to static loading were performed. The thin-walled cast components are modelled in the explicit FE-code LS-DYNA using shell elements. So far, it has been found that an elastoplastic material model based on the isotropic yield criterion of von Mises reasonably well captures the behaviour of HPDC components subject to both axial loading and 3-point bending. In addition, the ultimate loads in the different load cases are over-predicted analytically with the use of Eurocode 9 (EC9).

Processing of fine-grained aluminum foam by spark plasma sintering

Porous materials are now becoming attractive to researchers interested in both scientific and industrial applications due to their unique combinations of physical, mechanical, thermal, electrical and acoustic properties in conjunction with excellent energy absorption characteristics. Metallic foams allow efficient conversion of impact energy into deformation work, which has led to increasing applications in energy absorption devices. In particular, foams made of aluminum and its alloys are of special interest because they can be used as lightweight panels, for energy absorption in crash situations and sound or heat absorbing functions in the automotive industry with the aim to reduce weight to improve crashworthiness, safety and comfort.

Aluminium and magnesium castings – experimental work and numerical analyses

The long-term objective of this work is to develop design and modelling tools that allow the structural behaviour of thin-walled cast components to be predicted when subjected to static and dynamic loads such as in crash situations. The approach consists of the following ingredients: casting of generic geometry relevant for automotive design, component and materials testing, constitutive modelling and validation simulations using the finite element method. Here, HPDC components of both AM60 and AlSi7Mg have been subjected to axial crushing and 3-point bending. An existing elastoplastic constitutive equation has been calibrated and evaluated based on material tests. Next, validation analyses of the generic structural components subjected to static loading were performed. The thin-walled cast components are modelled in the explicit FE-code LS-DYNA using shell elements. So far, it has been found that an elastoplastic material model based on the isotropic yield criterion of von Mises reasonably well captures the behaviour of HPDC components subject to both axial loading and 3-point bending. In addition, the ultimate loads in the different load cases are over-predicted analytically with the use of Eurocode 9 (EC9).

An investigation into the energy absorption characteristics of a four-spoke steering wheel armature subjected to impact loading

This research focuses on the energy absorption abilities of a four-spoke aluminum steering wheel armature using finite element methods. Finite element model verification wav completed with experimental impact testing investigating impacts between a rigid plate and a four-spoke steering wheel. An acceptable correlation between the experimental testing observations and numerical simulation results was observed which suggests that information obtained from finite element simulations can be used to assess the energy absorbing abilities of the armature and of its regions during the impact. Information on the strain energy absorbed by the various regions of the armature can only be determined using numerical methods, experimental procedures can only provide information for the entire armature during the collision. To gain further insight into the energy absorption capabilities of different parts of the armature, highly detailed finite element models were developed and 25 numerical simulations were conducted under different impact conditions (investigating variations in the column angle and wheel angle). The simulations have shown that the steering wheel armature absorbs more energy under a high column angle and the rim region absorbs more energy compared with all other steering wheel regions. Those observations provide an understanding into the characteristics of energy management in crash situations for the steering wheel armature.

The distribution of energy absorbed by a three-spoke steering wheel armature in an impact with a deformable chestform

This research deals with experimental and finite element simulation of impacts occurring between a deformable chestform and an aluminium three-spoke steering wheel armature. Experimental testing was conducted to investigate the effect of impact location and armature orientation on the energy-absorbing capabilities of the automotive component. Numerical (finite element) models were developed to simulate the experimental process and to investigate further how the energy absorption abilities of the armature, and specific sections of the armature, vary with different impact situations. An excellent correlation between the experimental testing observations and numerical simulation results was observed for this highly non-linear problem. Most importantly, the finite element simulations have illustrated that the steering wheel armature hub and rim regions are the locations where most energy, because of plastic deformation in the structure, is absorbed. These observations provide an understanding of the characteristics of energy management in crash situations for the steering wheel armature.