External high-pressure forming of metal spiral tube of equal wall thickness

Abstract

Positive displacement motors are widely used underground power tools in oil and gas extraction. In order to solve the problems of the short life of the conventional positive displacement motor and the difficulty of machining the constant wall positive displacement motor, this paper proposes a metal bush stator. Based on theoretical analysis and tensile experiment of 304 stainless steel, a finite element model of an external high-pressure forming equal-wall-thickness metal spiral tube was established. The finite element method is used to study the external high pressure forming spiral tube with equal wall thickness. According to the results of the numerical simulation, we choose the tube blank with the inner diameter of 88 mm×the wall thickness of 3 mm for the experiment of external high pressure forming spiral tube. The result of the experiment is that the inner and outer surfaces of the metal spiral tube are smooth, and the spiral tube has no wrinkles or cracks. The maximum gap between the spiral tube and the mold is 0.12 mm, and the inner surface of the spiral tube is close to the mold. The maximum gap are at the transition of convex arc and concave arc. The minimum wall thickness and the maximum wall thickness of the spiral tube are 2.6 mm and 3.205 mm, respectively. The quality of the spiral tube is better when the inner circumference length of the tube (D2)/the contour line circumference (D1) of the mold is 0.974. The experimental results are in good agreement with the numerical simulation results. We have designed an assembled mold, which can be removed smoothly after the experiment. The research results of this paper have important engineering significance for improving the working performance of positive displacement motors.