Research and theoretical practice of spring calculation parameters

The circular motion friction creep error phenomenon of the high-speed precision servo feed table of the mechanical engineer's moving guide rail and the ball screw leads to the following conclusion: The friction model of "two-dimensional hybrid friction" is adopted in the mathematical model of the servo feed system. The magnitude of the contour error caused by the friction in the ball screw and the rolling guide can be predicted relatively accurately. The small displacement trajectory and the small velocity characteristic curve of the creeping stage can be simulated and actually measured on the ballbar. Using the mathematical model of the servo feed system considering the friction effect proposed in this paper, it is convenient to analyze and study the influence of the dynamic parameters such as stiffness, mass and damping on the system characteristics. In this paper, the circular section torsion bar spring widely used in vehicles is calculated and optimized by the node axisymmetric coordination unit in software. The analysis results show that the structure of the torsion bar spring transition zone has a great influence on the stress distribution. The optimized design of the torsion bar spring structure is beneficial to improve its performance. Torsion bar spring calculation and optimization structure and calculation The circular section torsion bar spring structure is divided into three parts, namely: working straight part, transition part and connecting parts at both ends. The stress concentration of the carrier generally occurs in geometrically discontinuous regions. For a torsion bar spring, the transition zone and surface defects between the working straight bar and the connecting portion at both ends cause stress concentration. For surface defects to be compensated by improving the processing technology, and the transition zone, it is necessary to design appropriate transition forms and design parameters to reduce stress concentration. State variables are functions of design variables that are used to constrain the values ​​of design variables and are constraints in optimizing the design process. The software can use parameters such as displacement, stress, weight, and volume as state variables. The torsion bar optimized in this paper has strict requirements on the space volume when it is installed and used. Therefore, the volume is selected as the constraint variable and the upper limit is specified. The objective function is the ultimate optimization goal. In software, it is a function of design variables and can only find its minimum value. In the optimized design of this paper, the purpose of optimization is to minimize the maximum shear stress of the torsion bar spring transition section, so the maximum shear stress is chosen as the objective function. Load and material characteristics The torsion bar spring acts as an elastic element and is subjected to a pure torsional load during operation. The stress and life requirements are relatively high. The maximum torque that the torsion bar spring is subjected to is the most dangerous condition. In this paper, the maximum torque of the torsion bar spring is due to the influence of temperature, the material coefficient is taken as a constant, and its elastic mode, Poisson's ratio of 12, is an isotropic material and is limited to linear elasticity. The geometry and constraints of the unit and meshed torsion bar spring calculation model, as well as the applied load are symmetric to its central axis. Using the characteristics of axis symmetry, it can be seen from the optimization results that the shear stress value of the torsion bar is the two largest. At the transition between the large end and the small end of the stress concentration, the axial stress is small, the edge stress is large, and the shear stress on the cross section gradually increases along the radial direction.

Experimental verification According to the optimization results, three arc-transition torsion bar springs were machined by the same process and tested experimentally. The experimental results show that the shear stress of the arc-transition torsion bar is the largest at the junction of the transition section and the connecting section, and the largest one is the average maximum shear stress. The maximum shear stress of the torsion bar of the original structure is 2,301. It can be seen that the maximum shear stress of the torsion bar after optimization is greatly reduced, and the performance is greatly improved.

Conclusion In this paper, the finite element model is established for the torsion bar springs commonly used in vehicles. The torsion bars of the two transition structures are calculated and optimized respectively, and the experimental verification is carried out. The results show that the optimized torsion bar is more conducive to reducing the stress concentration in the transition part. The finite element optimization design method proposed in this paper provides an effective method for the design of torsion bar spring. By optimizing the design of the torsion bar spring transition form, the stress distribution and the torsion bar performance can be effectively improved, so that the design can be better. A comprehensive performance of the torsion bar spring, which shortens the product development cycle and reduces the research cost.

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