“…In the study of acceleration inputs under axial load loading, the equivalent peak acceleration G peak and the amount of velocity change (denoted as ΔV) are usually used as a measure of the strength of the acceleration. Kulkarni et al [13] suggested that ΔV is the best single metric for evaluating occupant damage for a given range of pulse durations for any seat type. Keeping ΔV constant, the acceleration signal can be equated to a perfectly regular triangular waveform, which has the peak acceleration G peak , pulse duration T, and velocity change ΔV, as shown in Equation ( 1).…”
Section: Simulation and Analysis Of Human Lower Limb Injury Under Axi...mentioning
Axial impacts to the lower extremities of personnel in events such as explosions and falls on the underside of vehicles, which are extremely hazardous to personnel, may result in serious injuries. Most of the current studies on human lower limb injuries from axial loading have not considered the restraining effect of the knee joint. In this paper, based on the THUMS human finite element model, the failure parameters of the tibia, calcaneus, and talus of the lower limb are added and verified. On this basis, the response behavior of the lower limbs of personnel under different axial loads is investigated, and the damage law is further analyzed and studied. It is found that the motion of human lower limbs under axial impact is divided into two phases: the axial motion phase and the rotation phase around the knee joint, and the lower limbs are mainly subjected to compression and bending loads, respectively. The duration of the axial motion phase is related to the impact velocity and the rate of change of velocity and affects the magnitude of tibial force.
“…In the study of acceleration inputs under axial load loading, the equivalent peak acceleration G peak and the amount of velocity change (denoted as ΔV) are usually used as a measure of the strength of the acceleration. Kulkarni et al [13] suggested that ΔV is the best single metric for evaluating occupant damage for a given range of pulse durations for any seat type. Keeping ΔV constant, the acceleration signal can be equated to a perfectly regular triangular waveform, which has the peak acceleration G peak , pulse duration T, and velocity change ΔV, as shown in Equation ( 1).…”
Section: Simulation and Analysis Of Human Lower Limb Injury Under Axi...mentioning
Axial impacts to the lower extremities of personnel in events such as explosions and falls on the underside of vehicles, which are extremely hazardous to personnel, may result in serious injuries. Most of the current studies on human lower limb injuries from axial loading have not considered the restraining effect of the knee joint. In this paper, based on the THUMS human finite element model, the failure parameters of the tibia, calcaneus, and talus of the lower limb are added and verified. On this basis, the response behavior of the lower limbs of personnel under different axial loads is investigated, and the damage law is further analyzed and studied. It is found that the motion of human lower limbs under axial impact is divided into two phases: the axial motion phase and the rotation phase around the knee joint, and the lower limbs are mainly subjected to compression and bending loads, respectively. The duration of the axial motion phase is related to the impact velocity and the rate of change of velocity and affects the magnitude of tibial force.
“…Except for the blast test, a better way to simulate the blast impact environment. 27 The drop tower consisted of a pulse generator, a drop platform, four guide rails, lifting and release devices, etc. According to the test demand, it can generate a half-sine wave pulse with different peaks and widths.Figure 3.Drop impact test setup: (a) unprotected and (b) protected.…”
Section: Finite Element (Fe) Analysis and Validationmentioning
A circular honeycomb lower limb protection device was proposed to reduce the damage to the occupant’s lower limbs under a vehicle under-belly blast. First, a local equivalent model of the occupant-restraint system was established, and drop impact tests and theory were used to validate the model’s accuracy. Then, under the same mass, the protection performance of eight lower limb protection devices using circular honeycomb, hexagonal honeycomb, reentrant honeycomb, etc., as sandwiches were compared. It was found that the lower limb protection device with a circular honeycomb sandwich provides the best defence for lower limbs. Subsequently, the effect of gradient structure settings and dimensional parameters on the protection performance of circular honeycomb lower limb protection devices was investigated. Finally, multi-objective optimization has been carried out to further improve its protection performance. The results indicated that the protection performance of the lower limb protection device could be effectively improved by reasonably selecting the cell arrangement, gradient type and gradient interval of the honeycomb sandwich. When the optimized lower limb protection device was employed, the occupant's left and right lower tibial peak forces were decreased to 3.67 kN and 3.55 kN, respectively. Compared with the initial design, the optimized lower limb protection device reduced the left and right lower tibial peak forces by 21.1% and 23.8%, respectively, and the total mass decreased by 51.5%.
“…Full system, end-to-end modeling and simulation methodologies [1][2][3][4][5] have been used extensively for the development of blastworthy ground vehicles in the Army acquisition process. More recently, reduced-order modeling approaches [6][7][8][9] have also been developed for this purpose. .…”
In this paper, concepts are investigated for tuning material properties and component configurations in order to design structures with unique dynamic characteristics for mitigating blast loads while maintaining or reducing weight. The Dynamic Response Index (DRI) is employed as an occupant injury metric for determining the effectiveness of the each blast mitigation configuration that is considered. A finite element model of a notional V-Hull structure is used as a numerical example in this study. The material properties and the configuration of the inner bulkheads that connect the V-shaped outer surface with the inner floor are used as design parameters for reducing the DRI at a typical occupant location. In this particular example, it is demonstrated that both the weight of the structure and the DRI can be reduced simultaneously. This is achieved by creating a new structural design that features energy absorbing and decoupling mechanisms among the bulkheads, floor, seat, and the occupant.
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