THE RESULTS OF STUDIES OF THE CRACKS DEVELOPMENT IN THE CYLINDER HEADS OF THE ENGINE YAMZ-238НБ

The purpose of the study is to identify the maximum depth of the crack does not affect the normal working movement of the gates. To determine the nature and dynamics of growth heattransaction cracking of the cylinder head and waveness the maximum value of the crack depth and without disrupting the normal operation of the engine. Head material is grey cast iron SCH25 implies the presence of graphite inclusions, lamellar form. Also, this material structure is not optimal to improve the heat transfer, which increases thermal stresses. On the surface and the thickness of the firing of the bottom and leads to the appearance of such incidental defects, such as heatmobile cracks inside cylinder jumpers. Therefore, this defect limits the resource base. The study termodecreased depth of cracks was carried out according to the above method. The results of the studies the magnitude of this defect for the engine YAMZ-238НБ showed that the greatest dynamics of development of this defect is observed in inside cylinder the jumper between the injector hole and socket of the inlet valve. This area is characterized by the greatest temperature changes and mechanical stresses along the thickness and width of the site. It is observed during the period of achievements of 2000-3000 hours. Justified and proposed maximum allowable depth of cracks termodecreased for fire bottom of the cylinder heads in which no emergency is occurring defects of this part. This value should be considered the 6.5 mm because remaining intact the thickness of this zone provides the resource of this part until the next major overhaul. Depth control termodecreased of cracks will allow you to save some spare parts for major repairs of the engine to optimize the reuse of cylinder heads of engines.

stress, deformation, fatigue, crack