## 2 Methodology
### Simulation Model  
The main work of this paper is completed by MSC Patran, MSC Nastran and AVL EXCITE Power Unite (abbreviated as EXCITE) software. The crankshaft and block are created, meshed, and set material properties by MSC Patran. Export the bdf format model files of the crankshaft and the block from the Patran to the Nastran for the reduction. Set the main degree of freedom nodes of the crankshaft and block. The selection of the main degree of freedom nodes mainly considers the factors such as the action point of the external loads, the coupling point between moving parts, the distribution of the mass, and stiffness of the crankshaft and block. A schematic diagram of the main degree of freedom nodes model of the crankshaft of an in-line 4-cylinder engine after reduction is shown in Figure 1b. The blue dots in the Figure 1b represents the main degree of freedom nodes, and these main degrees of freedom nodes are selected at the main journal, crank pin, output end, and free end of the crankshaft. The mass and inertia of the crankshaft and the block will be concentrated on these main degrees of freedom nodes after condensation. According to research needs, determine the number of crankshaft and block modes to be retained in the condensation. Then, use the modal analysis solver Sol 103 in Nastran for reduction. After reduction, the mass, inertia, and dynamic characteristics of the crankshaft and block are retained, and the total number of degrees of freedom of the crankshaft and block are reduced from several hundred thousand to several thousand. Through reduction, the calculation amount of the multi-body dynamics model can be reduced. The reduced crankshaft and block are imported into EXCITE software as elastic bodies for calculation. EXCITE is used for the calculation of multi-body dynamics and elastohydrodynamic lubrication calculation for main bearings. The calculation results of the main bearing lubrication are directly given by EXCITE. The stress of the crankshaft or block is obtained by the Direct data recovery process with the MSC Nastran Sol 109 method. In this study, it is assumed that only linear and elastic deformation of the crankshaft and block occur. The dynamic stiffness of the main bearing is obtained through multi-body dynamics calculations. In order to simplify the engine model, the main bearing cap and the main bearing wall are built as one model, ignoring the preload of the bolts of the main bearing caps. The finite element model diagram of the crankshaft and the block is shown in Figure 2, the block diagram of the calculation workflow is shown in Figure 3, and the dimensions of the crankshaft and block are shown in Table 1.  
Figure 1: The schematic diagrams of the finite element model of a crankshaft of an in-line 4-cylinder engine and the main degree of freedom nodes model: (**a**) the schematic diagram of a finite element model of an in-line 4-cylinder engine crankshaft; (**b**) a schematic diagram of the main degree of freedom nodes model of the crankshaft of an in-line 4-cylinder engine after reduction. Figure 3: The block diagram of workflow of the anti-shock calculation model of the 16-cylinder V-type diesel engine. Figure 2: The diagram of the finite element model of the crankshaft and the block. The 16-cylinder V-type diesel engine used in this research is a 4 stroke engine and has a mass of 22.6 tons, which exceeds the measurement range of a heavy impact machine. The impact experiments cannot be carried out on conventional impact machines. The method of calculation is used to analyze the anti-shock performance of the 16-cylinder V-type diesel engine. The main structure and performance parameters of the 16-cylinder V-type diesel engine are shown in Table 2.  
The schematic diagram of the anti-shock calculation model of the 16-cylinder V-type diesel engine by EXCITE is shown in Figure 4. Figure 4 shows the logical connection between the components in the EXCITE model. The model includes crankshaft, block, piston, connecting rod, etc.