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Tips & Tricks - designing for impact loads

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As we have seen in impact design, the energy absorption can be doubled by using the entire section to carry the load. This is achieved by using a variable cross-section beam. The stress distributions are compared below for a rectangular beam in 3 point bending.

Stress Distribution Comparison

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As highlighted above, all the material in the variable section beam is completely utilised, resulting in reduced beam weight. Other manufacturing issues may need consideration (such as additional plate profiling and plate rolling), however the basic concept holds - the variable section beam is optimised for impact loading.

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Impact Energy Formulas

The formulas for the impact energy absorbed by the two different beams are shown below:

The coefficient of the variable section beam is twice that of the constant section, hence the impact strength is doubled.