The Structural Strength And Fatigue Analysis On The Engine Block Of Some Marine Diesel Engine

This topic comes from a school-enterprise cooperation project developing a new type of marine low speed two-stroke diesel engine, which primarily responsible for engine block structural strength and fatigue analysis to guide the design. During the project process, load cases selection, key simulation technology, structural strength and fatigue of engine block were carried out in this paper. At last fatigue influence factors farther analysis were studied. The feasible measures to improve the fatigue safety factor were proposed in addition. In this paper the main contents and conclusions are as follows:(1)Based on the structural feature of Marine low speed diesel engine, the block composition and the specific function of components were learned. The force analysis and operation conditions selection of block groups were finished.(2)Some key simulation technology of structural analysis such as the simulation of bearing force and the simplify simulation of bolt connection were verified by examination. At the same time, methods and measures of improving the convergence of complex model were researched, which made the subsequent analysis more persuasive. According to the analysis steps, the main force data such as main bearing force, explosion pressure and crosshead side force were achieved in Virtual Engine.(3)The solid model simplification and simulation object model extract were finished, establishing a correct and simple grid model. The corresponding constraints, boundary and load of engine block were completed, and the FE model was built.(4)Structural strength analysis of engine block including frame box, bedplate and stay bolts were carried out and discussed, by which the weak area of structure was found. The detailed analysis of assembly strength, thermal expansion characteristic, frame strength and stiffness under limit cross lateral force and strength of the frame under the ultimate bearing stress were studied. At last bolt structure strength respectively from the VDI standard and finite element analysis two aspects were checked through and contrasted.(5)the fatigue of engine block was analyzed, based on the previous structural strength analysis, which found the weak fatigue areas. Fatigue safety coefficients of frame, bedplate and stay bolt were checked. In view of the fatigue influence factors temperature and surface roughness, father research about impact rules of temperature and roughness to engine frame fatigue were studied. At last the feasible measures to improve the fatigue safety coefficient were proposed accordingly.