Advanced Stress Analysis

In all but a very few vehicles today crush or crumple zones are employed as a method to reduce energy transfer to the occupants in a crash.  For the most part crumple zones form a structural part of the car such as frontal rail or rear bumper beams.  In the early stages of development these crumple zones can be designed via a series of equations that take into account materials properties and geometrical features.

This assignment consists of the following three sections:

Question 1. Provide a literature review of thin-walled tube crushing and bending high-lighting mechanisms of deformation with respect to material and geometry including such phenomena of strain-rate sensitivity.

Question 2. Using an envelope of 600 mm in length, and a maximum of 100mm width and 100mm depth; design a crumple zone that is capable of absorbing ~8,500 Joules of energy at 50 km/h.  You can choose any geometrical shape and material to achieve this, but all choices
have to be backed up by analytical equations.  Use a crush distance of 75% of the original tube length (ie. 400 mm).  Make sure if you use a strain-rate sensitive material you include this into your calculations.

Question 3. Depending on your material choice do the following:

a. If you choose a metallic material for a single lobe of deformation show how stress and strain profiles and ultimately fracture (if occurs) progress through the deformation, show this via explanations, calculations and images

b. If you choose a composite material show how the fracture mechanisms/stress/strain work through lobe or ribbon formation; again show this via explanations, calculations and images.