Crankshaft Strength Calculation

The crankshaft is one of the most important parts in an internal combustion engine. The fatigue failure and fracture of crankshaft may lead to damages to the other parts, even some accidents. Especially when the requirement of engine's power and reliability is increased, the research of the crankshaft strength becomes more important. However, it's difficult to make a precise estimation of the crankshaft strength. Therefore, it has a great practical significance for the enterprises to find a reliable method for crankshaft strength assessment. This thesis toke the crankshaft of WD615-type diesel as the main research object. The process of conventional crankshaft strength design was improved via the methods of dynamic simulation and the finite element. Combined nonlinear multi-body dynamics simulation with the finite element method to get the crankshaft's dynamic stress, the fatigue computation was carried out. The bending fatigue test was conducted to assess the crankshaft strength.The major coverage is as follows:1. Through multi-body rigid kinematics & dynamics simulation of the cranktrain using dynamic software ADAMS, a more accurate boundary condition was provided for crankshaft strength design. Comparing the modern simulation method and the traditional method, the analysis result shows that the traditional method has the advantages of quickness, simplicity and credibility when the computation of piston acceleration, piston side-force and crankpin force is conducted. However, if we need calculate the main bearing load, the modern simulation method not only is in more simple operation and higher accuracy, but also can provide the abundant and comprehensive simulation data for the analysis of whole cranktrain dynamics.2. Based on the comparative analysis of several methods of conventional crankshaft strength design, the improved method was put forward. It's to utilize the solid model software to calculate section modulus and the finite element method to compute the stress distribution, which can gain the stress concentration factor of fillet accurately. Through the test of crankshaft static stress to prove the finite element method's computation model, the dependency of the quality of mesh was discussed. Meanwhile, the result showed the gravitation and centrifugal force could be neglected in the analysis of crankshaft static stress. Through the fatigue estimation for the crankshaft of WD615-type diesel, the validity of the improved method is estimated.3. Combined the finite element method with nonlinear multi-body dynamics simulation software EXCITE to study the dynamic response of cranktrain assembly, considering the coupling effect of bending and torsion, the crankshaft's dynamic stress was computed in the whole operating cycle. Based on the dynamic stress, the fatigue strength was computed by the fatigue analysis software. The comparative analysis showed the crankshaft's flexible effect could not be neglected when the crankshaft detail design and calculation of bearing lubrication & strength was conducted. The fatigue strength analysis method based on the dynamic stress was more convincing than the conventional strength analysis method.4. Utilizing the method of fatigue limit statistical analysis, the crankshaft fatigue test of WD615-type diesel was carried out on the resonant bending fatigue test rig.