EXPERIMENTAL AND FINITE ELEMENT STUDIES ON FREE VIBRATION OF AUTOMOTIVE STEERING KNUCKLE Article in Press

Steering Knuckle is a basic part of vehicle which joins suspension and steering system, wheel and brake to the chassis. It experiences several loads subjected to different conditions, for example, multi-axial loads and vibration. Hence, the knowledge of its dynamics and vibrational behavior is very important. Several materials are used to produce steering knuckle, for example, SG Iron, white and grey cast iron. However, nowadays there is a tendency to use aluminum alloy by automakers. Material replacement which results in weight reduction and using advanced materials are highly preferable. One suggestion is the use of Metal Matrix Composite which has higher strength to weight ratio and better performance than a metal. The main aim of this research is to determine the best material for manufacturing of steering knuckle in order to reduce the weight by applying aluminum alloy and Metal Matrix Composite. To achieve this purpose, the Modal test has been performed to study vibrational behavior of steering knuckle. CAD Model has been prepared by using coordinate measuring machine (CMM). Finally, the finite element analysis has been performed to evaluate natural frequencies and mode shapes of knuckle. The obtained FEM results have been compared with experimental data to validate the simulation. Three groups of materials (iron, aluminum alloy and metal matrix composite with different fiber volume ratio) have been investigated to determine the best material for manufacturing. DIN 1.7035, unreinforced alumina and MMC-Al 15% Ti-C have been reported as the best materials in each groups. MMC materials has higher vibrational rigidity and by using it, about 63.65 percent weight reduction is possible. FEM results for different models including CMM and smooth model have been compared with test data. The CMM model is closer to reality and it contains all details such as barcode, data and surface defects. It is obvious that meshing of smooth surface is easier than CMM model, but some details will be ignored which could affect the results. However, it has been shown that use of CMM model creates about 5.21% errors related to test data in comparison of 2.58% when the smooth model is used.