| Popis: |
During the creation and debugging of newly designed prototype of a piston engine, the main attention should be focused on the achievement of the technical requirements of durability of heat-stressed parts of piston engines surrounding the combustion chamber. These details are in thermal, power, kinematic interaction during operation of the internal combustion engine. When the engine is operating in transient modes, stresses occur in the cross sections of the cylinder head of piston engine not only from the action of gas forces, but also large stresses arise from temperature changes, since temperature over the period of the cycle changes. The temperature in the combustion chamber varies cyclically. Similarly, the thermal stresses vary cyclically. Variable stresses during a many loading cycles will lead to the crack in a cylinder head. It is necessary to choose those models for the calculation of a heat-stressed condition which would allow to find the durability of the cylinder head with high efficiency. The failure criterion of the heat-stressed parts of internal combustion engines is considered. The maximum strain criterion is used at viscous destruction. This criterion represents the sum of the ratio of the increment of the degree of damage to the magnitude of the plastic strain approaches unity. We examine the hypothesis of a linear summation of damages for the calculation method of the durability of the cylinder heads. |
