Abstrac In this paper, a method of modeling a seat belt on a crew seat during a dynamic seat testing was studied. The body segments
of the occupant were modeled with joints that consisted of various stiffness, damping, and friction. Three types of seat belt
restraint systems were investigated and an analysis on the injury assessment of the helicopter’s crew under a drop impact
was conducted. The effectiveness of the seat belt system for crashworthiness and safety was likewise evaluated. From the impact
analysis results, it was determined that the head, neck, and spine of the crew body can be easily damaged in the vertical
direction more than the longitudinal direction. Based on the verified model, the human body’s behavior was studied using three
point restraint systems. The displacement and injury level of the 12-point restraint system was the smallest.
This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008.
Young-Shin Lee received a B.S. degree in Mechanical Engi-neering from Younsei University, Korea in 1972. He received master and Ph.D. degree
in Mechanical Engineering from Yonsei University, Korea in 1974 and 1980 respectively. He is currently professor and Dean
of Industry Graduate School and Director of BK21 Mechatronics Group at Chungnam National University, Korea. Prof. Lee’s research
interests are in area of impact mechanics, optimal design, biomechanical analysis and shell structure analysis.
Jung-Hyun Lee received a B.S. degree in Mechanical Design Engineering from Chungnam Na-tional University, Korea in 2007. He received master
degree in Mechanical Design Engineering from Chungnam National Uni-versity, Korea in 2009. He is currently researcher of Korea
Aerospace Research Institute, Korea.
Kyu-Hyun Han received a B.S. degree in Mechanical Design Engineering from Hanbat National University, Korea in 2002. He received master
degree in Mechanical Design Engineering from Chungnam National University, Korea in 2004. He is currently researcher of Simuline
Inc, Korea. 相似文献
Structural effectiveness differences have been observed in a recent study on the progressive axial collapse of thin-walled structural sections when made from different classes of steels (mild steel, interstitial-free rephosphorized high-strength steel and high-strength low-alloyed steel). A higher effectiveness was observed for spot-welded top-hat sections made from a mild steel than for similar sections made from a high-strength steel. For square sections, the structural effectiveness was not affected by the steel classes. It is anticipated that this observation applies not only for spot-welded top-hat and square sections, but for other joined and unjoined thin-walled structures as well.
The part and full failure of spot-welds, during the axial collapse of the thin-walled structural sections, is one possible explanation for the above inconsistency. This is investigated experimentally in this article using peel tests on spot-weld samples under quasi-static and dynamic conditions. Despite having a lower material strength, the mild steel spot-weld samples exhibited a higher peak force and similar energy absorption during failure when compared with a high-strength steel, both under quasi-static and dynamic loadings.
The potential contribution to the mean crushing force during progressive axial collapse is estimated from the experimental results and comparisons are made with deformed thin-walled structural sections from a recent experimental study. Possible implications for the determination of the mean crushing force from analytical and numerical models are identified and discussed. 相似文献
Vehicle fleets in developed countries have benefitted from improved technology and regulation leading to safer vehicles. Nevertheless, for various reasons the public do not necessarily choose particular makes and models of cars according to their safety performance. This study aimed to identify areas for potential crashworthiness improvement in the Australasian fleets by studying the distribution of these fleets according to vehicle age and estimated crashworthiness. We used an existing database that encompassed the vast majority of the crash fleets studied, with existing estimates of crashworthiness generated by the Australasian Used Car Safety Ratings project. There were clear tendencies for older and younger people to be driving less safe vehicles that were also generally older. Given that older drivers are more fragile, and hence more liable to be injured in crashes, and younger drivers have a greater propensity to crash, it is clearly undesirable that these driver groups have the least crashworthy vehicles. Some suggestions are made to encourage safer vehicle choices. 相似文献
Rising complexity of industrial development in the automotive industry is leading to a higher degree of interdisciplinarity,
which is especially true in the virtual design area. New methods and solution procedures have to be evaluated and integrated
in the overall process. For example, in car body design process, a new topic emerged recently: the multidisciplinary optimization
of car bodies with respect to crash and NVH (noise, vibration, and harshness). Because rigorous evaluation of appropriate
numerical algorithms is still missing, an intense study was realized at the research center of BMW. The results are summarized
in this article. Four benchmarks have been studied: (a) a full vehicle model for NVH analysis, (b) a simplified multidisciplinary
problem with a single crash case and linear statics and dynamics, (c) a lateral impact problem for multi-criteria optimization,
and finally, (d) a small shape optimization problem was included to demonstrate the potential of transferring the results
to the more complex problem of optimizations based on real changes in the shape of the structures. Because response surface
methods have already been discussed in the literature and because of their failure in certain industrial cases, the focus
was set on the evaluation of stochastic algorithms: simulated annealing, genetic and evolutionary algorithms were tested.
Finally, a complete industrial multidisciplinary example from the current development process was studied for the validation
of the results. 相似文献
Two-dimensional triaxially braided composites (2DTBCs) are attractive in crashworthiness design because their fracture can dissipate a significantly larger amount of impact energy than other light-weight materials. This paper aims at predicting the fracture energy, Gf, and the effective length of the fracture process zone, cf, of 2DTBC composites. Since the fracture parameters are best manifested in the scaling properties and are the main parameters in the size effect law, the nominal strengths of three geometrically similar notched beams of three different sizes are simulated in a 3D finite element framework. The simulations are run for three different bias tow angles: 30°, 45° and 60°. Continuum beam elements in front of the notch are replaced with repetitive unit cells (RUCs), which represent the 2DTBC’s mesostructure, and are located in the region of potential cracking. Multiscale simulations, incorporating damage mechanics, are used to predict the pre- and post-peak response from three-point bending tests. Nominal stresses are calculated from the predicted peak loads and used to fit the size effect law. The dimensionless energy release rate function g(α) is determined from the J-integral. The values of Gf and cf are then determined using g(α) and the size effect law. With some exceptions, the results in general match well with the results of size effect experiments, and particularly the strong size effect observed in the tests. 相似文献
Effects of temperature and strain rate on the cohesive relation for an engineering epoxy adhesive are studied experimentally.
Two parameters of the cohesive laws are given special attention: the fracture energy and the peak stress. Temperature experiments
are performed in peel mode using the double cantilever beam specimen. The temperature varies from −40 to + 80°C. The temperature
experiments show monotonically decreasing peak stress with increasing temperature from about 50 MPa at −40°C to about 10 MPa
at + 80°C. The fracture energy is shown to be relatively insensitive to the variation in temperature. Strain rate experiments
are performed in peel mode using the double cantilever beam specimen and in shear mode, using the end notch flexure specimen.
The strain rates vary; for peel loading from about 10−4 to 10 s−1 and for shear loading from 10−3 to 1 s−1. In the peel mode, the fracture energy increases slightly with increasing strain rate; in shear mode, the fracture energy
decreases. The peak stresses in the peel and shear mode both increase with increasing strain rate. In peel mode, only minor
effects of plasticity are expected while in shear mode, the adhesive experiences large dissipation through plasticity. Rate
dependent plasticity, may explain the differences in influence of strain rate on fracture energy between the peel mode and
the shear mode. 相似文献
This paper describes an assessment program for paratransit buses concerning their crashworthiness and safety of passengers. The program developed by the authors was approved by the Transit Office of the Florida Department of Transportation as a part of the Florida Vehicle Procurement Program (FVPP) in August 2007. Several valuable, worldwide vehicle safety standards were adopted in it with modifications addressing the bus construction process and relevance of particular structural components in crash events. Passenger compartment structure, which needs to be protected against the most dangerous accidents such as a side impact and a rollover, is a major area of concern in the standard. Lack of such standards may result in poor crashworthiness characteristics of the bus structure and in severe injuries and possible passenger fatalities. Either full-scale experiments or numerical standardized simulations were proposed as equivalent approval methods for paratransit buses. Selected results for partially validated Finite Element (FE) models and the nonlinear explicit dynamic code LS-DYNA were used to demonstrate a numerical approach for a bus structure approval. The FE models can also be used to assist the bus manufacturer in an effort to improve the crashworthiness of the new bus designs. The procedure described in this paper was implemented to monitor crashworthiness resistance of the paratransit buses distributed and operated in the state of Florida. 相似文献