A method and apparatus for designing a screw-tightening element are
disclosed for designing the screw-tightening element (mechanical
element). The design method comprises representing material
characteristics of the screw component with factors including at least
one of an elastic limit, an endurance strength, a true breaking power and
a tension strength, representing a material characteristic of the
tightening object with a factor including an elastic limit, providing a
plurality of damage patterns associated with the material characteristics
of the screw component and the tightening object, and calculating
tolerance values of fluctuating loads in the plurality of damage patterns
based on the material characteristics of the screw-tightening element and
the elastic limit of the tightening object. The tolerance values of
fluctuating loads are compared to determine an optimum tolerance load for
the screw-tightening element.