title: Crash pulse optimization for occupant protection at various impact velocities.
abstract: OBJECTIVE
  Vehicle deceleration has a large influence on occupant kinematic behavior and injury risks in crashes, and the optimization of the vehicle crash pulse that mitigates occupant loadings has been the subject of substantial research. These optimization research efforts focused on only high-velocity impact in regulatory or new car assessment programs though vehicle collisions occur over a wide range of velocities. In this study, the vehicle crash pulse was optimized for various velocities with a genetic algorithm.
  
  
  METHODS
  Vehicle deceleration was optimized in a full-frontal rigid barrier crash with a simple spring-mass model that represents the vehicle-occupant interaction and a Hybrid III 50th percentile male multibody model. To examine whether the vehicle crash pulse optimized at the high impact velocity is useful for reducing occupant loading at all impact velocities less than the optimized velocity, the occupant deceleration was calculated at various velocities for the optimized crash pulse determined at a high speed. The optimized vehicle deceleration-deformation characteristics that are effective for various velocities were investigated with 2 approaches.
  
  
  RESULTS
  The optimized vehicle crash pulse at a single impact velocity consists of a high initial impulse followed by zero deceleration and then constant deceleration in the final stage. The vehicle deceleration optimized with the Hybrid III model was comparable to that determined from the spring-mass model. The optimized vehicle deceleration-deformation characteristics determined at a high speed did not necessarily lead to an occupant deceleration reduction at a lower velocity. The maximum occupant deceleration at each velocity was normalized by the maximum deceleration determined in the single impact velocity optimization. The resulting vehicle deceleration-deformation characteristic was a square crash pulse. The objective function was defined as the number of injuries, which was the product of the number of collisions at the velocity and the probability of occupant injury. The optimized vehicle deceleration consisted of a high deceleration in the initial phase, a small deceleration in the middle phase, and then a high deceleration in the final phase.
  
  
  CONCLUSIONS
  The optimized vehicle crash pulse at a single impact velocity is effective for reducing occupant deceleration in a crash at the specific impact velocity. However, the crash pulse does not necessarily lead to occupant deceleration reduction at a lower velocity. The optimized vehicle deceleration-deformation characteristics, which are effective for all impact velocities, depend on the weighting of the occupant injury measures at each impact velocity.
authors.affiliation: a Department of Mechanical Science and Engineering , Nagoya University , Nagoya , Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ito
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yokoi
authors.forename: Koji
authors.initials: K
authors.lastname: Mizuno
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D001696:Biomechanical Phenomena; D003654:Deceleration; D006801:Humans; D008297:Male; D008348:Manikins; D008954:Models, Biological; D014947:Wounds and Injuries / Q000517:prevention & control*
keywords: crash pulse; crashworthiness; front impact; injury; optimization; various impact velocities; vehicle design