2011 年 2011 巻 56 号 p. 13-18
The shape of a stabilizer bar for automobile suspension systems is usually designed from the standpoint of avoiding physical interference with other components. Also, the diameter of the bar is usually pre-selected and fixed to achieve a desired vehicle anti-roll stiffness. Therefore, engineers/designers have little design flexibility to adjust the resultant stress that a given bar will experience in use. In order to improve the durability of stabilizer bars, there are conventional approaches such as a material approach (for example using high strength materials) or a manufacturing approach (for example using efficient shot peening process). It is also known that increasing the radius of bend portions will reduce stress since high stress usually occurs at bends, but this approach is not always possible when interference to other components becomes an issue or when the clamping position of the bar is difficult to change. Unlike conventional methods mentioned above, this paper provides a method to reduce the stress at a bend by slightly modifying the bend shape. By properly adjusting the bend shape from an arc (constant radius) to a non-constant radius curve (Bezier curves are used in this study), stress reduction could be as much as 8.8%, thereby extending the fatigue life of the bar approximately 1.7-1.8 times. This is accomplished by decreasing curvature in high stress areas and increasing curvature in low stress areas, resulting in flat stress distributions. This paper shows that the stress reduction depends on the bar shape and the stress distribution of the original bend shape. It is also shown that a stress reduction can be achieved by creating the bend, not only with continuously changing radius, but also with a series of arcs with different radius.