Buckling of automatic transmission clutch plates due to thermoelastic/plastic residual stresses

The plates of multidisk automatic transmission are known to buckle under extreme operating conditions. Axisymmetric (coning) and nonaxisymmetric (potato chip) modes can be obtained It is shown that these modes result from in-plane axisymmetric residual bending moments in the disk and the critical value for each mode is found. A numerical algorithm is then developed to determine the residual moment due to a prescribed axisymmetric thermal history. Allowance is made for the temperature dependence of yield stress, elastic modulus, and coefficient of thermal expansion. The results show that susceptibility to buckling depends on a dimensionless geometric shape factor, the material properties, and the magnitude of the largest thermal excursion. With steel disks and typical design values for the shape parameter; buckling is predicted for temperature differences of about 600 degrees C between inner and outer radii.