Research On Dynamic Stress Of The Cylinder Head Bolts Of The Diesel Engine

Bolt joints are common and important connection structures on the machinery and equipment. The cylinder head bolt connects the cylinder and the head,which is one of the engine bolts that require the highest.During installation,it bears a great preload;during working,it bears a complex alternating load,of which size and the direction change with the change of the crankshaft. So it is important to carry research on the strength of cylinder head bolt.This paper takes the cylinder head bolt as an example to analysis and research on the dynamic characteristics and modeling method.The paper presents a research on the dynamic stress on the cylinder head bolt by two different method:check the static strength based on the VDI2230guidelines and check the dynamic strength of the cylinder head bolt. Then make a comparison with the two result that obtained by the two methods, the major work I make are as follows:①The3-D model can be simplified by using the software HyperMesh, some component will be ignored which take little effect on the bolt, then define boundary conditions, give the material properties, element type to the different element, then import the file of the type of.dbb to ANSYS, the finite element model will be got.②Use software ADAMS to compute the dynamic stress, such as piston side thrust, vertical and horizontal loads of the main bearing, which look as the dynamic loads that will be loaded on the engine.③Load preloads on the bolt, then load dynamic loads within a work cycle on the finite element model.④ccording the main stress cloud picture of the result that calculated in the ANSYS, analysis the stress of the bolts on different time within a working cycle of the engine, then access the strength according to the result.⑤Testing the dynamic strain and stress of the cylinder head bolts, then get the curve of the dynamic strain of the two nodes selected, compare it to the result calculated in ANSYS, to validate the accuracy of the method of the ANSYS calculation.⑥In accordance with the VDI2230criteria described, calculating the strength of cylinder head bolt at the time of the maximum pressure of the fourth cylinder achievedBy calculation with the two method, at the time of the maximum pressure of the fourth cylinder achieved, the maximum force the bolt bears achieve679MPa using the finite element method, and674MPa calculated based on VDI2230guidelines.The two result are close to each other, and the safety factor meet the requirement, which proves the effectiveness of these two method, besides, it also prove the feasibility of the finite element calculation and the VDI2230criteria in other types of the bolt joints, taking advantage of the two methods to get an accurate results, which accumulated a more reliable method of calculating the strength of bolted joints, so the relevant units could save some time and reduce the cost.