Theoretische und experimentelle Untersuchungen für eine Bemessung und serienreife Entwicklung von Ein- und Auslassventilen aus Siliziumnitrid

A concept for the fatigue assessment of intake and exhaust valves from silicon nitride was developed. The concept includes the definition of operational stresses on the valves and the determination of the fatigue strength. The loading conditions temperature (stationary and instationary), valve opening, combustion pressure and valve closing were studied. For these loading conditions, the operational stresses at different points of the valve were calculated by finite element method. The fatigue strength of the ceramic valves were examined by experimental fatigue tests. Additional to the fatigue tests, Adam Opel AG investigated ceramic intake and exhaust valves by motor tests. To proving the behaviour of ceramic valves under traffic conditions, driving tests were carried out by five Mercedes Benz Cars.