Development of Door Impact Loads Using Pedal Force Sensor and First Principles

The first step in designing or analyzing any structure is to understand “right” set of loads. Typically, off-road vehicles have many access doors for service/getting into cab etc. Design of these doors and their latches involve a knowledge of the closing loads when the door is shut mostly with an impact of varying magnitudes. In scenarios of these impact events, where there is sudden change of velocity within few milliseconds, produces high magnitude of loads on structures. One common way of estimating these loads using hand calculations involves evaluating the rate-of-change-of-momentum. However, this calculation needs “duration of impact”, and it is seldom known/difficult to estimate. Failing to capture duration of impact event will change load magnitudes drastically, e.g. load gets doubled if time-of-impact gets reduced from 0.2 to 0.1 seconds and subsequently fatigue life of the components in “Door-closing-event” gets reduce by ~7 times. For these problems, structures are usually designed and analyzed with certain assumptions for impact loads, and they end up either overdesigned or under designed for the reasons cited above. To design doors/latches structures under these impact loads further gets challenging due to not-so-easy way of measurements of impact forces. In this presentation, authors talk about how door impact loads were developed using frugal use of pedal force sensors, strain gages and effective use of mathematical techniques like load reconstruction. Further authors will also talk about correlation of developed loads with measured loads along with parameterization of these loads with respect to mass and door opening angle.