A 0-D Calculation Template to Define Crush Space Requirement and Body Front End Force Level Requirement in Concept Stage

Today’s automotive world has moved towards an age where safety of a vehicle is given the topmost priority. Many stringent crash norms and testing methodology has been defined in order to evaluate the safety of a vehicle prior to its launch in a particular market. If the vehicle fails to meet any of these criteria then it is debarred from that particular market. With such stringent norms and regulations in place it becomes quite important on the engineer’s part to define the structural requirements and protect the space to meet the same. If the concept level platform definition is done properly it becomes very easy to achieve the crash targets with less cost and weight impact.

In our project a calculation methodology is presented in form of an excel based template that defines the crush space requirement in a vehicle and gives an insight to the designer regarding the force level that needs to be managed in the vehicle’s front end (assuming the uniform property of barrier) to meet the frontal offset crash test. This calculator was compared by taking the measurement of real time crash pulse data of the accelerometer which was placed at the B-pillar of the vehicle. The deformation values that were obtained in the calculator matched with the displacement data obtained after post processing of the crash data with an accuracy of 97.99%. This calculator takes ‘M’, mass of a car and ‘g_av’, the average allowable vehicle deceleration (considering safe deceleration value at occupant level) as the input to evaluate the following parameters of a crash event: - Zero cross over time, time taken for barrier crush, time consumed in vehicle crush, the average deceleration imposed by the barrier on the vehicle and the average deceleration imposed on the vehicle due to deformation of its front end and the crush space requirement. The average deceleration due to vehicle front end deformation gives an insight to the designer regarding the section requirement and material usage in the front end load members to accommodate the required force before bottom out. In order to arrive at the same some statistical assumptions for rebound energy and barrier energy were collected based on our extensive prior art search for crash behavior of different benchmark vehicles. This calculation template is quite useful in defining the critical parameters of the vehicle like crush space, deceleration level of body (section requirement for load path) in concept stage to meet the frontal offset crash requirements.