Totally found 57 items.

  • [期刊] Optimisation and validation of full and half foam filled double circular tube under multiple load cases
    In this study, numerical results are conducted to determine the deformation mode of foam filled double circular tubes, namely; half foam filled double circular tube (FD), and full foam filled double circular tube (DD) under oblique loading. To validate the simulation and experimental results, two-parameter Weibull probability distribution was used. The proposed function of the multi-objective optimisation design (MOD) process was based on the Finite Element Analysis results. The metamodels in were constructed to predict the crashworthiness criteria of specific energy absorption and peak crushing force under oblique impact loading. Also examined in the study were the MOD problems of the two structure types under multiple impact angles using the NSGA II algorithm. The findings from the study determined that the optimal full foam filled double circular tube had better crashworthiness under pure axial loading. While the optimal half foam filled, double circular tube had more space to enhance the crashworthiness under an oblique impact.
  • [期刊] Reliability analysis of vehicle speed estimation based on uncertainty of information obtained on accident scene
    In numerical analysis of vehicle-pedestrian accidents, the estimation of impact speed is often completed based on some on-scene information such as pedestrian projection distance. In this article, aimed at the uncertainty of accident on-scene information, error calculation formulas of crucial information are derived based on the process of on-scene investigation. Meanwhile, the reliability model of pedestrian projection distance measurement is established using first-order reliability method. With the vehicle-pedestrian accident scene that has been built, the reliability safety factors of projection distance measurement under different impact velocity are calculated. Furthermore, the influence of positioning methods, impact velocity, and datum points on reliability of on-scene information is discussed, and some suggestions are made to improve the reliability of on-scene investigation.
  • [期刊] Studies on shape memory alloy-embedded GFRP composites for improved post-impact damage strength
    Embedding shape memory alloys (SMAs) in composites is a promising method resistance against impact loading.In the present paper, an attempt is made to quantify the improvement in damage mitigation properties of FRP (fibre reinforced plastic)composites by embedding SMA.Numerical modelling of low velocity impact was carried out topredict the delamination in composites and composites embedded with SMA and steel wires. Through modelling, effect of location and quantity of SMA material in decreasing the impact induced delamination size was also studied.Compression after impact (CAI) tests were carried out on pristine and SMA hybrid composite (SMAHC)specimens to quantify the change in damage resistance. Experimental results show an improvement in compressive load-carrying capacity after impact in SMAHC as compared to pristine composites.Experimental results match well with numerical findings in terms of; location of placement of SMA wire and optimum quantity of SMA wires.
  • [期刊] A contribution to full-scale high fidelity aircraft progressive dynamic damage modelling for certification by analysis
    The era of powered flight began with the introduction of the first flying machine in 1903. Sadly, less than two years later, the first fatal accident in a powered aircraft occurred. Motivated in part by this early tragedy, engineers have raised aerospace standards so that air travel is now the safest means of mass transit in the world. However, unplanned landings on unanticipated surfaces continues to pose an ever-present risk of casualty, due in-part to a lack of understanding about such interactions. The experimental characterisation of full-scale airframe crashworthiness has traditionally been cost-prohibitive and therefore rare. In an effort to complement current airframe certification requirements and contribute towards certification-assisted analysis, this paper presents a partially validated comprehensive numerical methodology. This methodology is applied to assess the progressive structural damage resulting from a full-scale aircraft model impacting soft and hard surfaces with comparison to a real-life commercial aircraft crash landing test.
  • [期刊] Structural qualification of a developed GFRP-reinforced TL-5 concrete bridge barrier using vehicle crash testing
    Corrosion of steel reinforcement due to environmental effects is a major cause of deterioration problems in bridge barriers. Glass fibre reinforced polymer (GFRP) bars, not only addresses this durability problem but also provides exceptionally high tensile strength. A recent design work conducted at Ryerson University on a test level 5 (TL-5) bridge barrier considered the use of 16 and 12-mm diameter GFRP bars as vertical reinforcement in the barrier front and back faces, respectively, with 16-mm diameter GFRP bars as horizontal reinforcement in the barrier wall, all at 300 mm spacing. The connection between the deck slab and the barrier wall utilised the GFRP headed end bars for proper anchorage. This paper summarises the procedure and the results of a recent vehicle crash test conducted on the developed barrier. The crash test involved the 36 000 V tractor trailer impacting the barrier at a nominal speed and angle of 80 km/h and 15 degrees, respectively. Crash test results satisfied crash test evaluation requirements including structural adequancy, occupant risk and vehicle trajectory after collision. Estimates of the equivalent impact force and associated energy absorbed by the barrier wall due to vehicle impact were deduced.
  • [期刊] Mixed FE-MB methodology for the evaluation of passive safety performances of aeronautical seats
    The certification of aircraft seats involves the investigation of the structural performance of their components under emergency landing conditions. . The paper reports the activities related to an experimental sled-test of a single row of two seats placed in front of a stiff fuselage bulkhead, by considering a single anthropomorphic dummy arranged on one of the seats. Tests have been developed at the facility equipped with a sled decelerator testing system compliant with certification requirements from FAR25 for TSO C127a regulations. Four different numerical models have been developed in order to simulate the experimental test: a full-FE modelby LSTC-LsDyna (R) code, a full-MB modeland a hybrid FE/MB developed using by TNO-Madymo (R) code and a Coupled FE/MB model. Numerical results achieved by these models have been compared with experimental ones, in order to assess their use for CBA (certification by analysis) purposeto be applied since the preliminary design phase of the seat.
  • [期刊] Numerical simulation and analysis of influencing factors of vehicle-pedestrian accidents in untypical contact state
    Current numerical analysis of car-pedestrian accidents pays more attention to typical contact state, which means pedestrians collide with the front of vehicle, but less to untypical contact state, which means pedestrians collide with the edge of vehicle. The keystone of this study is to discover appropriate initial parameters of accidents in untypical contact state fast and accurately because numerical simulation usually takes long time. Meanwhile, functions between optimised parameters and initial input parameters in an untypical-contact-state accident are fitted by polynomial regression analysis and has achieved a high degree of accuracy. Simulation of typical case indicates that the combination of orthogonal test and polynomial regression analysis can determine appropriate initial parameters more accurately compared with orthogonal test. Furthermore, the results of numerical simulation and medical identification have achieved a high degree of consistency, which indicates that the reliability and rationality of simulation have been verified.
  • [期刊] Occupant injury risk assessment and protective measures in frontal collision of a bus
    A significant issue worldwide is a bus frontal collision which can result in more than 10 fatalities per incident. The study aims to develop recommendations on injury risk reduction in such frontal collisions. A LS-DYNA and MADYMO coupling method as well as sled tests were employed to investigate the effect of seat layout variables including seat pitch, height difference and back inclination angle on occupant injury to different body parts, protection measures were subsequently developed to minimise occupant injury risk. The results show that secondary collision with the front seat back can cause severe head and neck injuries.Although the lap belt can restrict the movement of the pelvis and lower limbs, the collision and relative slippage between the head and the front seat back still cause a high neck bending moment. The study further reveals that seat layout variables should be design-specified to optimal values that minimise such injuries.
  • [期刊] Interaction of impact parameters for simulated falls in sport using three different sized Hybrid III headforms
    This study describes the interaction of impact parameters on peak head acceleration and strain variables for test conditions represented in sport. The Hybrid III 6-year-old child, 5th percentile female, and 50th percentile adult male headforms were subject to parametric tests using a monorail drop tower at four impact velocities (1.5, 3.0, 4.5, and 6.0 m/s), three surfaces (unprotected, protected/helmeted, and well-padded/mat), and four impact locations (frontal, sagittal, combined-plane motions, and a rotationally dominant motion). Scaled finite-element models of the brain were used to obtain peak strains. Regression analyses revealed that compliance produced the greatest increases in head acceleration, while impact velocity was for strain. Smaller headforms were associated with higher responses. Non-uniform trends for impact location were noted and are likely a result of localised headform properties interacting with velocity and compliance. These findings support the need for size-appropriate parameters in the design and development of head protection.
  • [期刊] The biomechanical differences of shock absorption test methods in the US and European helmet standards
    Nowadays crash helmets are tested by dropping a free or unrestrained headform in Europe but a guided or restrained headform in the United States. It remains unclear whether the free fall and the guided fall produce similar impact kinematics that cause head injury. A ?nite element helmet model is developed and compared with experimental tests. The resulting head kinematics from virtual tests are input for a ?nite element head model to compute the brain tissue strain. The guided fall produces higher peak force and linear acceleration than the free fall. Eccentric impact in the free fall test induces angular head motion which directs some of the impact energy into rotational kinetic energy. Consequently, the brain tissue strain in the free fall test is up to 6.3 times more than that in the guided fall. This study recommends a supplemental procedure that records angular head motion in the free fall test.
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