LAUSR

In order to clarify the thermal deformation and failure mechanism of the nodular cast iron cylinder head of marine diesel engines during long-term service, a high-efficiency thermal cycling experiment was conducted on scaled cylinder head specimen based on the similarity principle, and the thermal cycling load was simulated by flame heating and water spray cooling method. Then the Chaboche combined hardening model considering temperature and cumulative effect was established. The cyclic plastic behavior of the scaled specimen model during non-uniform thermal cycling was verified from transient temperature, cumulative out-of-round deformation and crack failure. Subsequently, the law of cyclic plastic deformation of specimens under thermal cycling was studied. The results showed that with the increase of the cycle number, the plastic strain of the valve bridge region of the scaled specimens accumulated gradually, showing a large amount of permanent strain of the circular hole within a maximum of 20.3 μm out-of-round deformation. The difference between the calculated and tested deformation is 1.9 μm (10.5%), which shows the excellent predictability of the numerical model. The research findings are valuable for predicting and evaluating the thermal-structural behavior of the prototype cylinder head.