posted on 2012-09-21, 13:50authored byJohn D. Dakin
This research work involved the prediction of the fatigue life of an automotive rear
suspension twistbeam assembly fitted to a vehicle travelling over a customer correlated
durability route. This was achieved by making use of the integrated concepts of scaling and
superposition of linear static finite element analysis being driven by experimental load data
- the so called 'quasi-static time domain' approach. A study of the free body diagram of the
twistbeam resulted in an indeterminate load set of some 24 components, with experimental
data indicating that a state of static unbalance existed. Subsequent to developing a
matrix-based generalised method ofload cell calibration to confum the foregoing, a modal
technique was developed to partition the experimental data into a static load set, causing
elastic deformations, and a rigid load set, imparting rigid body accelerations. The
semi-independent characteristics of the twistbeam necessitated the coupling of large
structural displacements with inertia relief. This required extensive modifications to the
current techniques and led to the development and use of a three dimensional functional
response matrix in place of the conventional two dimensional one. Recommendations
concerning appropriate finite element boundary conditions were also formulated to handle
these effects. Finally, the limitations of the uniaxial fatigue model were revealed under the
application of a set of tools for analysing the biaxiality and mobility of the maximum absolute
principal stress.
History
School
Aeronautical, Automotive, Chemical and Materials Engineering