Research On The Method Of Stress Amplitude Of Fatigue Based On Diesel Engine Block

Railway is the main artery of national economy. With the rapid development of economy and the gradual improvement of the living standards of the people, railway in China has entered into a dangerous period of high-speed and heavy load.At present the analysis method of fatigue life on theoretical is not mature and the experimental date relevant to fatigue is not sufficient. Despite that, the fatigue strength of locomotives been checked in its design and manufacture time, the accidents of fatigue fracture still occurred. The phenomenon above shows that the analysis method of fatigue life estimation on locomotive is an important subject.The fatigue risk points maybe missed in fatigue estimation with static or dynamic analysis separately. At the same time, the current multiaxial fatigue life assessment is mostly through principal stress or Von Mises stress equivalent to uniaxial stress. In process of calculating stress amplitudes of fatigue life estimation, principal stress method is two mutually perpendicular vectors, and Mises stress method is the concept of the deviator strain energy. The two methods above are deviated to fatigue fracture mechanics theory.The thesis takes 16V240ZJ diesel engine block as the research object, and studies the method of fatigue life evaluation with finite element analysis technology. During the research process, designs geometric model of 16V240ZJ block by CAD software Pro/E firstly. Then import the geometric modal into HyperMesh to establish the finite element model. Adopts the above model to calculate the results in the conditions of the cylinder outbreak with ANSYS and analyzes the stress of the 16V240ZJ diesel engine block. Setting load step with 5°, conducts transient dynamic analysis. Observe the stress distribution of the static analysis and transient dynamic analysis. Compare the dangerous points of fatigue between static and dynamic analysis. In the process of fatigue life estimation, the thesis also calculates the fatigue stress amplitude with principal stress, Von Mises stress and normal stress.Obtains the dangerous points with the methods above respectively, and discusses their reliability.The conclusion revealed that the critical points obtained by static and dynamic analysis are not consistent, and different stress amplitude methods provide different crtical points. In process of calculating stress amplitudes of fatigue life estimation, the fatigue life estimation results obtained by principal stress method slant to conserve and the results obtained by Mises stress method slant to danger. The result does not only provide evidence for judging the dangerous points on 16V240ZJ engine block, but also provide important theoretical significance for locomotive vehicle fatigue evaluation.