Investigation of creep behavior analysis of a coiI spring

Tsukimori, Kazuyuki

A mechanical hold down method is under discussion as the means to prevent fuel assemblies from being lifted up in the scope of investigation of the recycle reactor conception at Plant Engineering Section. The device of the mechanical hold down system is a coil spring. In this case it is necessary to maintain enough pressure force in high temperature region. Therefore, it is needed to analize creep behaviors of coil springs. At this stage it is desirable to survay parametrically the creep behaviors of various dimensions of coil springs rather than to analize detailed behaviors by FEM. This paper describes the investigation of a creep behavior analysis method of coil springs. In the development process of the method the torque of the spring is derived from the assumption of shear stress field and hear distribution of shear strain in the radius direction and the constitutive equation of creep, and finally the spring force can be obtained by the equilibrium equation as the function of time. For implementation of this method a simple program should be created since the shear stress distribution in the radius direction is nonlinear, however, a wide ranged parametric survay can be done on the creep behavior of coil springs of arbitrary shape, dimension and material.