Yuichi Kitagawa

Development of a Collapse Mode Control Method for Side Members in Vehicle Collisions

Sie members are provided with beads that promote more effective absorption of crash energy in vehicle frontal collisions. In this work, finite element analysis was used to investigate a method of calculating the most effective beading position. First, it was found that an inelastic buckling mode as a numerical imperfection makes it possible to analyze the collapse behavior of beaded members. Second, a new method was developed for calculating the most effective beading position along the buckling mode of side members. When a side member is provided with beads according to this method, it collapses axially, enabling it to absorb crash energy more efficiently. It was also found that the buckling mode used as a numerical imperfection for determining the placement of beads should be calculated at the peak point of the load curve.

Development of A Human Ankle/Foot Model

A finite element model of the human ankle/foot was developed in this study. The bony part was originally developed by ESI and was well validated against inversion/eversion and dorsiflexion responses of the cadaveric lower leg. In this study, the ankle/foot model was revised to simulate mechanical response in compression. Tendons and ligamens were added to the bony model to reproduce deformation of the mid-foot. Comparison with static test results showed excellent performance of the revised model. Dynamic response was examined by applying an impact to the sole of the foot with muscular tension. Model predictions demonstrated a better match with test results than those calculated by the original bony model.

Simulation of Automobile Side Member Collapse for Crash Energy Management

Vehicle collision characteristics are among the most im portant performance parameters to be examined at the design stage. These characteristics are greatly affected by the collapse mode of the box columns making up the side members of the vehicle body. An accordion-type collapse mode in which the columns do not bend but collapse in sequence is ideal. Beads or reinforcements are often used to produce this kind of mode; however, the work done on them to date has been mainly experi mental, owing to an absence of adequate analytical methods such as the finite element method. In this study, we have developed a new analytical method for providing beading on side members along the buckling mode using finite element analysis calculations.

Evaluation of Vehicle Body Stiffness and Strength for Car to Car Compatibility

When considering a car to car frontal crash between a small light car and a large heavy car, it is necessary to evaluate the stiffness and strength of each vehicle body. As interactive force at the contact surface cannot be measured directly in a car to car crash test, a simplified practical method has been developed to estimate the interactive force based on the vehicle deceleration. The adequacy and consistency of the proposed method was verified by using the principle of conservation of energy. The calculated force-deformation curves revealed that the interactive force reached the maximum designed strength of the small light car based on the ODB (Offset Deformable Barrier) test for crash protection, while the force level was far below the corresponding design limit of the large heavy car. It was observed that the relatively lower stiffness of the small light car resulted in absorbing a larger share of the total input energy of the system when crashed into the large heavy car. By analyzing the interactive force profile in detail, it was found that the maximum impact force and the end of crash force could be used as a barometer to assess car to car crash compatibility.

Finite element simulation of ankle/foot injury in frontal crashes

Finite element models of human body segments have been developed in recent years. Numerical simulation could be helpful when understanding injury mechanisms and to make injury assessments. In the lower leg injury research in NISSAN, a finite element model of the human ankle/foot is under development. The mesh for the bony part was taken from the original model developed by Beaugonin et al, but was revised by adding soft tissue to reproduce realistic responses. Damping effect in a high speed contact was taken into account by modeling skin and fat in the sole of the foot. The plantar aponeurosis tendon was modeled by nonlinear bar elements connecting the phalanges to the calcaneus. The rigid body connection, which was defined at the toe in the original model for simplicity, was removed and the transverse ligaments were added instead in order to bind the metatarsals and the phalanges. These tendons and ligaments were expected to reproduce a realistic response in compression. It is well known that the arch of the mid-foot is extended before the tibial shaft is deformed when a large compressive force is applied. The model was first validated against static compression data to evaluate its mechanical response. Then, its dynamic response was calculated to simulate the cadaver impact tests conducted by the authors previously. Good agreement between model predictions and test results was achieved. Improvements made to the model by adding the soft tissue are described in detail. (A) For the covering abstract see ITRD E106349.

Evaluation and Research of Structural Interaction between of two cars in Car to Car Compatibility

Incompatibility between two colliding cars is becoming an important issue in passive safety engineering. Among various phenomena, indicating signs of incompatibility, over-riding and under-riding are likely caused by geometrical incompatibility in vertical direction. The issue of over-riding and under-riding is, therefore, not only a problem for partner-protection but also a possible disadvantage in self-protection. One of the possible solutions of this dual contradictory problem is to have a good structural interaction between the front-ends of two cars. Studies have been done to develop a test protocol for assessment of this interaction and to define criteria for evaluation but mostly in terms of aggressivity, which is a term describing incompatibility of a relatively stronger car. In this study, it was hypothesized that homogeneous front-end could be a possible better solution for good structural interaction. A homogeneous front-end will result in less aggressivity and better self-protection at the same time, regardless of the front-end stiffness of an opponent car. Stress distribution at the front-end surface can be taken as possible indicators to quantitatively evaluate homogeneity of the car front-end. A multiple load-cell barrier enables to analyze stress distribution by measuring force inputs at discrete load-cells outputs through a crash test. In addition to digitizing stress distribution on the load-cell surface, statistical techniques can be used to quantify the deviation. A simulation study was conducted on simple frame models to examine the validity of the hypothesis and the capability of the proposed indicators. (A) For the covering abstract see ITRD E121867.