Optimal shape design of engine connecting rod with special lumping-mass constraint

In a typical reciprocating internal combustion engine, the connecting rod (conrod) is generally working under high-speed rotation and heavy dynamic loading, with relatively more complicated dynamics behavior than other components. The key issue in this study is to achieve an optimal design shape of the conrod not only with the optimum stress distribution, but also under the special constraint of accurate lumping-mass at piston pin and crankpin centers for optimal dynamic characteristics. Herein, the varied-mass lumping method, the finite element method and the optimization theory are combined to achieve the innovative design objective of dual optimization. This optimization is aided by the sensitivity analysis technique, the finite difference scheme, and the sequential secondary programming method to achieve a conrod shape design with fully stressed boundary curve and desirable dynamics features.