# Optimization of Pile Driver Frame Based on Sensitivity Analysis
## 2 Body Model Structure and Analysis
### Finite Element Model (FEM)  
The rapid development of computer technologies has made it possible to use simulation techniques to complete the design and analysis of complex product structures. The finite element method is based on the principle of variability, and is essentially a numerical approximation method. It helps to solve complex engineering problems by approximating the structure as a whole, using a finite number of organic combinations of discrete units. Since the finite element method has a very clear physical concept, this method is also highly suitable for more complex structures. At the same time, the calculations of the finite element method can be implemented by computer and are highly efficient. Currently, the finite element method is widely used in the study of static structural dynamics, fluid analysis, thermal analysis, electromagnetic field analysis and other problem areas. The use of parametric finite element modeling techniques for the modeling, analysis, and optimization of product design is one of the commonly used approaches in engineering practice. A high-precision model construction based on the finite element analysis method is able to recover the true model with relative accuracy. The analysis and design of product batches through parameters considerably improves design efficiency and saves design costs. In this paper, the ANSYS parametric design language provided by the ANSYS finite element analysis software is used to perform computer-aided modeling. The finite element model of the large body structure of the YZY400 hydraulic pile driver is used as the object of study, and all the performance parameters of the pile driver are shown in Table 1.  
The large body structure of this model of the static pile driver is welded by steel plates and is a complex space box system structure. In order to ensure that the finite element analysis is carried out properly and effectively, the original model is simplified appropriately.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{2}{c}{**Numerical**} & \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Numerical Value**} \\  & & **Value** & & \\ \hline Total mass & 140 t & Crane rated lifting & 16 t \\ Pling capacity & 400 t & Whole machine size & 12.9 \(\times\) 10.0 \(\times\) 7.38 m\({}^{3}\) \\ Grounding & Longship & 0.119 MPa & Line & Longship & 3.3 m \\ specific voltage & Shorthship & 0.127 MPa & Size & Shorthship & 0.8 m \\ Pressing piles & Maximum speed & 4.7 m/min & Stake & Square pile & 250, 300, 400 mm \\ Speed & Minimum speed & 1.3 m/min & size & Round pile & 300, 400, 500 mm \\ \hline \hline \end{tabular}
\end{table}
Table 1: YZY400 pile driver performance table.  
Members without load-bearing effects were removed, details such as unnecessary holes and rounded corners were simplified, and legs attached to the bulk structure were simplified. In this paper, in order to facilitate the optimization analysis of the bulk structure based on its properties, we parametrically model it using the ANSYS APDL pc-software(Mechanical APDL 2020 R1, ANSYS, USA). Since the bulk structure belongs to a large thin plate structure, with a large difference between the thickness and the rest of the dimensions, the plate and shell units are chosen to simulate actual steel plates when modeling. The specific type is chosen from the shell 63 in APDL [17]. During the finite element analysis, the transmission of forces relies on the nodes between the units. In order to ensure that the finite element analysis is performed correctly, a proper meshing is particularly important. Therefore, in this paper, the model is meshed in the form of free triangles. The meshing of local locations in the model is shown in Figure 2.  
After the establishment of the finite element model of the large body structure, the boundary conditions are applied to the model, and the static analysis is carried out based on the loads that the large body skeleton is subjected to in the actual work.