| With the rapid development of economy, the demand for oil and natural gas is increasing, and the exploration and exploitation of unconventional oil and gas resources such as shale gas and coal bed gas have become one of the national energy development strategies. Fracturing pump is the core equipment in the development of unconventional oil and gas resources, which is used for the fracturing operation. The connecting rod is one of the main driving parts of the power end of the fracturing pump, which is subjected to the alternating load such as tension, compression,bending and so on. It is easy to be destroyed in the high stress area due to fatigue damages. This requires that the connecting rod not only has sufficient strength and anti fatigue performance at work, but also requires a reasonable shape and light mass as much as possible, so as to reduce the inertia force generated by the connecting rod during the operation. With the development of fracturing pump in the direction of large discharge, high power, high pump pressure, the working environment of the connecting rod is getting worse and worse. Therefore, lightweight design of connecting rod is very significant to improve its reliability and service life, so as to ensure the multi section continuous operation of the fracturing pump.The subject took a certain type of fracturing pump power end connecting rod as the research object, analyzed the static characteristics of connecting rod with contact finite element method, find out the weak links of the structure, on the basis of this, the connecting rod was lightweight designed. Mainly completed the following work:1. Connecting rod motion and force analysis. The analytical method was used to analyze the motion law of the connecting rod and the stress situation in the process of motion. And the relationship between the force of the connecting rod and the change of the crank angle was found. The load spectrum of the connecting rod in a working cycle was drawn, and the maximum load of the connecting rod under tension and compression working condition was obtained, which provided the basis for the finite element analysis of the connecting rod when applying load boundary conditions.2. Analysis of static characteristics of connecting rod. Firstly, the strength of the connecting rod bolt was analyzed considering the influence of the cross head pin and crankshaft on the connecting rod by using the contact finite element method. Then,the unreasonable layout of the bolt on the junction surface of the connecting rod andthe bearing pedestal is redesigned to make the load of each bolt is uniform. On this basis, the static analysis was carried out on the connecting rod under the condition of maximum tension and maximum compression. The stress distribution and deformation of the connecting rod under two conditions were obtained and the fatigue strength of the high stress area of the connecting rod was checked. Through the static analysis of the connecting rod, the weak link of the structure and the parts that need to be improved are found, which provides the basis for the design and improvement of the connecting rod.3. Lightweight design of the connecting rod. The fifth chapter is the lightweight design of connecting rod. Firstly, the topology optimization design of the connecting rod was carried out, and found the structures which need improving. On this basis, to make quality as the objective function, sensitivity analyses have been carried out for the bearing cover thickness, stress concentrative points and other related dimensions of the connecting rod and the dimension, which has a larger effect on the mass of connecting rod, has been found. By applying stress and boundary condition, the optimization design of the connecting rod was carried out. Finally, the static and dynamic performance analysis of the optimized connecting rod structure was carried out, and the rationality of the results by using topology optimization and size optimization has been verified. |
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