Search Results

In general, the improvement of vehicle body stiffness involves a trade-off with the body weight. The objective of this research is to derive the lightest-weight solution from the original vehicle model by finding the optimized spot-weld layout and body panel thickness, while keeping the body stiffness and number of spot welds constant. As the first step, a method of deriving the optimal layout of spot welds for maximizing body stiffness was developed by applying the topology optimization method. While this method is generally used in shape optimization of continuous solid structures, it was applied to discontinuous spot-weld positions in this work. As a result, the effect of the spot-weld layout on body stiffness was clarified. In the case of the body used for this research, body stiffness was improved by about 10% with respect to torsion and vertical and lateral bending.

The numerical relations between occupant restraint systems and injury indexes were investigated by multi-parameter optimization of an integrated restraint system model of frontal crash simulations. This paper proposes a method of optimizing restraint systems in two types of test configurations: a 35-mph full overlap crash model and a 40-mph 40%-offset crash model.

This paper presents a method for optimizing occupant restraint system parameters in vehicle frontal crashes. Simulation models incorporating restraint systems and dummies are used for predicting injury indexes. A full-scale survey of all of the design parameters related to the injury indexes would require a vast number of simulations. Therefore, the Design of Experiments (DOE) method involving a minimum number of experiments is more realistic. However, dummy behavior often shows discontinuity if the dummy comes in contact with the steering wheel, so it is not predicted well with usual DOE methods. This paper shows how to incorporate such discontinuity in a DOE study and how to optimize the restraint system parameters to reduce occupant injury indexes. It also discusses the feasibility of this method for integrated optimization of 50th percentile and 5th percentile dummies.

The Flexible Pedestrian Legform Impactor (Flex-PLI) was developed to evaluate the risk of pedestrian lower extremity injuries. However, it has been pointed out that the post-crash kinematics of the Flex-PLI differs from those of a human body when it is hit by high-bumper vehicles. This paper describes the feasibility of applying the Flex-PLI to a wide range of vehicle types by adding a supplemental weight. The following aspects are discussed in this regard: A human body finite element (FE) model analysis shows that the upper body of the Flex-PLI is not involved in tibia and knee ligament injury indexes in the first contact with a high-bumper vehicle. A rigid bar model is introduced and its rotational energy ratio is formulated. The rotational energy ratio is employed to evaluate the post-crash kinematics of the Flex-PLI and a human leg model. The feasibility of adding a supplemental weight to the Flex-PLI with regard to the bumper height is discussed.

A logistic regression analysis of accident cases in the NASS-PCDS (National Automotive Sampling System-Pedestrian Crash Data Study) database clearly shows that pedestrian pelvis injuries tend to be complex and depend on various factors such as the impact speed, the ratio of the pedestrian height to that of the bonnet leading edge (BLE) of the striking vehicle, and the gender and age of the pedestrian. Adult female models (50th %ile female AF50: 161 cm and 61 kg; 5th %ile female AF05: 154 cm and 50 kg) were developed by morphing the JAMA 50th %ile male AM50 and substituting the pelvis of the GHBMC AM50 model. The fine-meshed pelvis model thus obtained is capable of predicting pelvis fractures. Simulations conducted with these models indicate that the characteristics of pelvis injury patterns in male and female pedestrians are influenced by the hip/BLE height ratio and to some extent by the pelvis bone shape.

A comprehensive analysis was performed to evaluate the effect of BMI on different body region injuries for side impact. The accident data for this study was taken from the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS). It was found that the mean BMI values for driver and front passengers increases over the years in the US. To study the effect of BMI, the range was divided into three groups: Thin (BMI<21), Normal (BMI 24-27) and Obese (BMI>30). Other important variables considered for this study were model year (MY1995-99 for old vehicles & MY2000-08 for newer vehicles), impact location (side-front F, side-center P & side-distributed Y) and direction of force (8-10 o'clock for nearside & 2-4 o'clock for far-side). Accident cases involving older occupants above 60 years was omitted in order to minimize the bone strength depreciation effect. Results of the present study indicated that the Model Year has influence on lower extremity injuries.