E. C. Chirwa

Review of the Jordan Rollover System (JRS) vis-a-vis other dynamic crash test devices

A review of most of the existing rollover dynamic devices was conducted in view of assessing their flexibility, reliability, repeatability and crash reconstruction potential. The outcomes indicate the Jordan Rollover System (JRS) to offer the better potential with respect to a repeatable dynamic test procedure in all aspects than the Inverted Drop Test, the Dolly Test Procedure SAE J2114 or FMVSS 208, the Controlled Rollover Impact System, the Corkscrew Rollover System, and above all the newly updated FMVSS 216 Roof Crush Resistance Test. The positive attributes of the JRS are that the device as a research tool is flexible and accurate enough to accommodate most prescribed input conditions; it measures dynamic near and far side impact roof crush loads, not possible with other test devices; it has excellent repeatability en par with the National Highway Traffic Safety Administration and the Insurance Institute for Highway Safety dynamic frontal, side and rear impact tests; it is scientifically acceptable and indeed represents an improvement over other dynamic test devices used by the industry; it provides reliable roof crush and roof crush speed comparisons between vehicles; and it measures cumulative roof crush data believed by many experts in rollover to be a function of head–neck system injury severity. In addition, the JRS is a self-contained device that occupies a small footprint to perform controlled tests within industry-accepted laboratory crash test tolerances at a far more reasonable cost than other test devices. It is the best available dynamic test device in terms of assessing the interaction between roof deformation, occupant kinematics and restraint systems. Original equipment manufacturers and associated researchers can use the device to supplement the new FMVSS 216 in this regard. This is particularly so considering that the next phase of the FMVSS 216 is the development of a dynamic procedure. Moreover, the device can be readily used to star rate rollover crashworthiness of vehicles.

‘Egg-box’ panel for commercial vehicle front – compressive loading tests

The numbers of serious accidents and fatalities from accidents between commercial vehicles and vulnerable road users (VRUs) are still high and show no sign of declining. For pedestrians, this is traumatic due to high incompatibility of vehicle fronts. Hence, decisions have been made to implement countermeasures that have the potential for casualty reduction. This paper proposes an ‘egg-box’ energy-absorbing panel to be incorporated in a commercial vehicles cab front and sides. As a consequence it is expected to reduce the load between vehicle and pedestrians, while at the same time eliminating the risk of serious injuries and fatalities. The egg-box panel herein has been compressed under quasi-static conditions in order to study the collapse mechanism of the structure and quantify the corresponding load regimes for various stages of collapse. An attempt has been made to understand the structures energy-absorption capability from the resulting load-deflection curves. Also, a simple assessment of the structures crashworthiness is discussed and comparison made to existing energy absorbers. The maximum load that a 30 mm high panel structure can withstand is approximately 18 kN. Unlike in a concertina tube where a sudden drop in load is observed after the formation of the first plastic hinge, there is no drastic fall in this load after the collapse has started. A steady load is observed with the progressing deformation. With the height reduced to 20 mm, the maximum load capacity increases by 20% approximately along with increase in the stiffness.

Benchmarking and accident characteristics of flat-fronted commercial vehicles with respect to pedestrian safety

Abstract The information about pedestrian accidents and kinematics involving commercial vehicles is not properly understood. In general the total accident scenarios with heavy vehicles are unique in the sense that one has a very strong structure impacting a very soft pedestrian. This makes the problem complex and the solution requires the development of a new description of accident kinematics. This study has shown this by assessing flat-front vehicle accidents involving pedestrians. The study has also shown that those most at risk are the child pedestrians, due to the fact that their height compares well with the height of the rigid bumper, and their fragility in comparison to adults makes them more vulnerable. The truck used in this study is the MAN L2000 truck model driver cabin. This is analysed for different contact zones and corridors. An effort is made to derive an “Aggressivity index,” which would enable designers to assess the Aggressivity of vehicle during the design process. Quasi-static experiments and material testing on the driver cabin components are carried out to determine their mechanical properties and the energy absorption capability of component in the interface.

Wheelchair occupant kinematics during a rail carriage crash

Over recent years, a number of legislative tools and codes of practice have been put in place to provide wheelchair users with greater access and freedom of using trains. However, much more is still needed to be done to improve the safety of wheelchair occupants (WOs) while on board. In the United Kingdom, under the Disability Discrimination Act, only approved dimensions are the minimum requirements for use of a wheelchair in a rail carriage. This paper seeks to provide an analysis of the experimental kinematics of a WO under frontal impact tests carried out using a 57 kg dummy subjected to a sudden stop generating a pulse of about 15 g, which is less than the ECE M1 vehicle category. However, this is more severe than the 5 g pulse that covers both the European Commissions TSI and prEN 15227 with regards to train crashes. Results of frontal impacts are presented where the resulting kinematic characteristics are used to assess the potential injury severity of the occupant. A loaded sled with a combined mass of about 200 kg was accelerated horizontally to 3.3 m/s and suddenly stopped using a rigid barrier to simulate the worst loading condition. Eight restraint scenarios are covered. These form the basis for making recommendations considering the safety of a WO during a crash of a rail carriage. The baseline scenario constitutes not securing the wheelchair and not restraining the occupant. This also represents the worst case for injury potential. The ideal scenario involves securing the wheelchair and restraining the occupant using a three-point occupant restraint system. The paper concludes by providing recommendations for seating configurations to improve the survivability of a WO during a crash in a railway vehicle.

Numerical investigation into the collapse behaviour of an aluminium egg-box under quasi-static loading

A wide range of energy absorbing structures and geometries have been researched upon and proposed for safety applications, particularly for automotive safety. Aluminium pressload panels are being researched to explore the energy absorption capabilities of the unique geometry so as to utilise them for automotive vehicle structures as energy absorbers. Preliminary research outputs describing the deformation of the egg-box under quasi-static loads were presented and the structure was proposed for a commercial vehicle front by the authors. Also the underlying reasons for the specific mode of deformation of the geometry were experimentally explored and research results were published. The current work serves as an extension to the recently published work as a numerical study using HYPERMESH and LS-DYNA software packages and validation against the experiments was carried out. The panel was experimentally tested to further explore the deformation pattern of the egg-box geometry. The effect of natural restraint that occurs due to the existence of the surrounding finite number of peaks/frusta and the flanges surrounding each frustum that comprises the panels geometry was investigated as three separate cases: (1) single peak with free-free edges, (2) single peak with constrained edges and (3) single-peak in-situ, all tested quasi-statically. The egg-box geometry was modelled numerically and the simulated results were in good agreement with those from the experiment. The specific energy absorption of the single peak cut from the panel and edges left unconstrained was 300 J/kg and that with constrained four corner edges was 700 J/kg. The single peak in-situ absorbed as high as 775 J/kg of specific energy, which is nearly 2.6 times greater than that of for a single peak with free-free edges. This indicates the positive influence of the natural occurring restraint within the egg-box panel geometry to its energy absorption capability.

Search for pedestrian protection regulations for commercial vehicles

In effort to make transportation safer, crashworthiness engineers strive to obtain optimum design solutions to protect pedestrians and occupant passengers. The achieved solution leads to formulation of a set of rules and criteria for a vehicle to behave during an accident, thereby protecting either pedestrians, occupants or both. These test criteria are developed by validated experimental procedures, which have to be followed prior to the launch of vehicle into the market. Hence, vehicles are equipped with active and passive safety systems to satisfy the regulations. As there are different classes of vehicles along with varying geometry/design, there exists a necessity for regulations for each class of vehicles. The present study recognises the existing issues with flat-front vehicles and necessary solutions with respect to pedestrian protection. A new test methodology for accessing the flat-front vehicles for pedestrian protection is also proposed. Additionally, the test requirements for formulations of regulations are emphasised.

Virtual testing for the assessment of a double-sided roof crush based on the newly updated Federal Motor Vehicle Safety Standard 216

The newly updated Federal Motor Vehicle Safety Standard 216 enhances the requirements of the roof crush behaviour as it particularly focuses on the double-sided test protocol. This test will be mandatory from the year 2012 and will replace the single-sided test. The research presented herein aims at investigating the behaviour of a small European vehicle subjected to this newly updated Federal Motor Vehicle Safety Standard 216 and at assessing the effect of the variation in the loading combination of the pitch angle and the roll angle on the roof crush strength to quantify the difference in the performances. A Ford Fiesta FE model developed at the University of Bolton was refined and validated against the roof crush test. Thereafter a full factorial method was employed to the design of the experiment based on varying the pitch angle and the roll angle. The response functions concerning the resistance force of the double-sided roof were hence constructed with the results from a series of virtual tests based on nine levels of the roll angle and four levels of the pitch angle. Parametric studies were then conducted with respect to the effects of the body structural components, the windscreen and the variations in the roll angle and the pitch angle on the roof strength. The results show that the roll angle and the pitch angle are functions of the roof strength. In general, the roof on the near side performs in a stronger way than the roof on the far side and greatly influences the overall collapse behaviour. Within a crush distance of 127 mm (5 in), the strengths on both sides of the roof decrease as the roll angle varies from 10° to 45°. The variation in the pitch angle influences the resistance force. In addition, the windscreen is found to contribute significantly to the roof strength on the far side, hence demonstrating a strength which is artificially high, not quantifiable and not observed in real-world rollover crashes. From the virtual parametric analysis carried out, it shows once again that the recommended loading-angle combinations in the newly updated Federal Motor Vehicle Safety Standard 216 roof crush test should be a roll angle of 45° (and not 25°) and a pitch angle of 10° (and not 5°) for both near-side and far-side roof load application.

The newly updated FMVSS 216 roof crush modelling and analysis

There is no doubt that rollovers are more complicated than planar crashes and attributed injury mechanisms are still debated among original equipment manufacturers (OEMs), design engineers, safety experts, impact biomechanics specialists and research scholars at academic institutions. Two intertwining factors and their assumed interpretations have been at the core of these discourses, namely the roof crush strength versus the legislative requirement Federal Motor Vehicle Safety Standard 216 (FMVSS 216) and the real associated injuries in rollovers. The newly updated roof crush standard FMVSS 216 (effective from 2012) seems to answer some of the queries raised in the many debates, which include the increase in the applied force from 1.5 to 3.0 times the vehicles unloaded weight, the addition to the legislative requirement of heavier vehicles between 2.7 and 4.5 tons and the improved crush procedure that includes the roof testing of both sides at platen combination angles of 5° pitch and 25° roll. From the National Highway Traffic Safety Administrations (NHTSA) own regulatory analysis estimates, the new FMVSS 216 will save 135 lives from the recorded 10,000 yearly rollover fatalities. The interpretation of these survival figures is that the societal cost is still high and can be further reduced by looking at the European rollover analysis and how the European Union (EU) has approached the reconstruction of rollover problems. Through in-depth numerical analysis using finite element model of a passenger vehicle tested at different platen combination of pitch-to-roll angles, this paper demonstrates that using the regulatory requirement of 5° pitch and 25° roll does not constitute the worst loading condition. The roof resisting resultant force and the energy associated therewith depict the force for the 10° pitch and 45° roll angle combination to be, in reality, twice smaller than that for the 5° pitch and 25° roll angle combination. This can be interpreted with conviction that occupants will be put at high risk of injuries because the roof, despite meeting the new FMVSS 216 requirement, will collapse catastrophically. As a result, the new regulation will be rendered inadequate unless the platen angle combination of 10° pitch and 45° roll is adopted.