Abstract
Existing methods of stress analysis for pistons assume axial symmetry of form and loading; they cannot predict stresses in the region of the gudgeon pin bosses. In the method of analysis proposed in this paper a piston is idealized as a portal, including the gudgeon pin bosses; allowance is made for the restraining effect of the rest of the skirt on this portal; the deformations of piston and gudgeon pin are made to conform.
The idealized problem may now be formulated for solution by a standard structural analysis program; however this involves a considerable amount of hand calculation, especially for the evaulation of thermal stresses. In order to reduce this, a special purpose program was written. This uses the force method of structural analysis and can evaluate both mechanical and thermal stresses.
Stresses measured during rig tests are compared with those calculated using the new method. Good agreement is obtained and, in the authors' view, the use of the ‘restrained portal’ idealization is confirmed.
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