Gear tooth root composite strengthening process technology based on ultrasonic rolling

Abstract

The invention discloses a tooth root rolling and finishing composite strengthening process method, which mainly considers that a gear is easy to generate tooth root bending fatigue failure under heavy load, obtains a modified tooth root through tooth root micro modification, and then adopts ultrasonic rolling to carry out tooth root local strengthening on the gear tooth root so as to improve the residual stress of the tooth root. And then the gear surface roughness after barreling and finishing is calculated according to the radius of the finishing abrasive particles, and the gear tooth root is subjected to finishing treatment based on a theoretical calculation result. And finally, the gear is processed to obtain the high-performance gear, so that the bending fatigue resistance of the gear tooth root is improved. And according to the gear material performance, the ultrasonic rolling strengthening tooth root performance parameters are determined. According to the stress relation, the tooth root residual stress after ultrasonic rolling strengthening is calculated, then the gear is subjected to barreling finishing machining analysis, the theoretical minimum roughness after barreling finishing is calculated according to the barreling finishing abrasive particle radius and tangential force, and finally actual machining is conducted. According to the method, grinding micro-modification, ultrasonic rolling strengthening and barreling finishing can be combined, the tooth surface of the gear is strengthened by correcting all technological parameters, the performance of the tooth root after machining is improved, and meanwhile the machining precision of the gear is improved.

Description

Technical Field

[0001] The invention belongs to the field of gear machining and relates to a high-strength steel spur gear tooth root ultrasonic rolling strengthening technology and a surface rolling finishing technology. Background Art

[0002] In the gear transmission system, the gear tooth root performance directly affects the bending fatigue reliability of the entire gear transmission system. This is especially significant under heavy load conditions, so it is particularly important to consider the strengthening process design to reduce the probability of crack initiation and expansion and improve the fatigue strength of the tooth root.

[0003] At present, in the conventional involute spur gear processing, most gears are mainly surface strengthened by heat treatment and tooth root shot peening, and then precision grinding is performed. However, the tooth root stress of conventionally processed gears has not been improved well. Therefore, the surface performance of the processed gears is poor, which affects the service life and reliability of the gears.

[0004] The present invention combines the requirements of the modern heavy-duty gear industry and the current production level to carry out process coupling design for ultrasonic rolling and surface rolling finishing of the gear tooth root, combines the calculation method of gear roughness and residual stress, strengthens the gear tooth root through a composite strengthening process, designs processing parameters that can achieve ideal tooth surface performance, improves the bending performance of the gear, and improves the meshing efficiency and service life. Summary of the invention

[0005] The invention discloses a tooth root rolling and finishing composite strengthening process technology, which includes gear tooth root transition curve optimization, tooth root ultrasonic rolling strengthening technology and tooth surface finishing processing technology.

[0006] The present invention aims to propose a process method for composite strengthening of the surface of gear tooth roots, which can improve the overall performance of the gear through tooth root strengthening and surface finishing after precision micro-grinding of the gear.

[0007] The specific implementation steps are as follows:

[0008] S1: The JC constitutive model of typical gear materials is obtained through the Hopkinson pressure bar test;

[0009] S2: Fit an accurate and reasonable tooth profile and root modification curve through the tooth root curve equation;

[0010] S3: Establish a gear ultrasonic rolling model, calculate and analyze the stress field under different rolling parameters and the overall stress field after unloading;

[0011] S4: Establish a finishing abrasive grinding model, calculate the material removal volume under the action of abrasive particles, and deduce the abrasive grinding depth under abrasive particle collision;

[0012] S5: Calculate the surface roughness limit after processing;

[0013] S6: Conduct actual tests to test the performance of the processed gear tooth surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a flow chart of the present invention;

[0015] Figure 2 Coordinate diagram of gear tooth root curve

[0016] Figure 3 This is a schematic diagram of ultrasonic rolling of gear tooth root;

[0017] Figure 4 This is the spherical cavity model under the impact of the rolling process;

[0018] Figure 5 It is a model of the micro-action of surface finishing abrasive particles on the surface;

[0019] Detailed description of the implementation plan

[0020] The gear tooth root transition curve is tangent to the involute. The tooth root curve parameters directly affect the ultrasonic rolling parameters and the tooth root surface rolling and finishing process. The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0021] A tooth root rolling and finishing composite strengthening process technology includes the following steps:

[0022] S1: The JC constitutive model of typical gear materials is obtained through the Hopkinson pressure bar test;

[0023] S2: Determination of gear tooth root transition curve: When the rack-type tool is machining a gear, the tool's machining pitch line is tangent to the gear's machining pitch circle. Assume that there is no displacement between the tool and the gear during the machining process. Figure 2 The rectangular coordinate system shown in the figure, where P is the node, nn is the common normal line of the contact point between the front corner of the tool and the transition curve of the tooth root, and α 1 is the angle between nn and the tool processing pitch line. With the coordinate system, the parametric equation of the gear tooth root transition curve is:

[0024]

[0025] In the formula, (x, y) is the horizontal and vertical coordinates of a point on the transition curve; r is the pitch circle radius of the gear being processed; θ is the angle that the gear rotates when the pitch circle of the gear and the pitch line of the tool are in pure rolling; Angle is a variable parameter, It varies in the range of α to 90°. By substituting the tool parameters, the coordinates of different points on the transition curve can be obtained, thereby fitting the gear tooth root transition curve.

[0026] S3: Based on step S1, the finite element method is used to clarify the range of rolling depth. Based on Hertz contact theory and the law of conservation of energy, the finite stress distribution method is used to establish the ultrasonic rolling mechanical model.

[0027] The rolling ball acts on the tooth root surface, and elastic-plastic deformation occurs in the contact arc area, such as Figure 3 As shown. When the rolling ball is pressed into the tooth root surface at a certain rolling depth h, the center of the entire stress core area of ​​the tooth root first undergoes plastic deformation, and the area close to the edge is still in elastic deformation. The elastic area satisfies the Hertz contact theory. The contact radii a and b of the plane are:

[0028]

[0029] Where F is the external load applied to the rolling ball. 1 and μ 2 , E 1 and E 2 are the Poisson's ratio and elastic modulus of the rolling ball and tooth root materials, respectively. a and n b are the coefficients of the contact radii m and n, respectively. a and n b The value of can be obtained by looking up the ratio of A to B.

[0030]

[0031] During the entire machining process, the rolling ball and the tooth root surface remain perpendicular. According to Hertz contact theory, the maximum stress p in the contact arc area is:

[0032]

[0033] S4: Establish a finishing grinding model and calculate the volume of material removed by abrasive particles. In the gear rolling finishing process, the abrasive particles and the gears collide and squeeze at high speed. The volume of material removed by a single abrasive particle in a micro-grinding action is calculated as:

[0034] The groove depth, L i is the distance that the abrasive particles grind the surface. The grinding depth of the abrasive particles under the collision of the abrasive particles is derived, and the grinding depth of the abrasive particles h is calculated as:

[0035]

[0036] d is the width of the groove in the overlapping area produced by the downward movement of the abrasive particles, HB is the Brinell hardness of the gear surface, and P is the pressure distribution on the surface.

[0037] S5: Calculate the surface roughness limit after processing. Under a certain abrasive extrusion pressure, the surface roughness limit after processing is:

[0038]

[0039] S6: Conduct actual tests to test the performance of the processed gear tooth surface. According to the calculation results, the ground gear is shot peened and surface finished to produce the corresponding gear.

[0040] The above is a detailed introduction to a tooth root rolling and finishing composite strengthening process method provided by the present invention. For those skilled in the art, there may be differences in the implementation of the present invention, but as long as the use requirements are met, they are all within the protection scope of the present invention.

Claims

1. This method focuses on the fact that gears are prone to tooth root bending fatigue failure under heavy loads. Through micro-modification of the tooth root, a modified tooth root is obtained, and then ultrasonic rolling is used to locally strengthen the tooth root of the gear to increase the residual stress of the tooth root. Then, the tooth surface roughness after rolling and finishing is calculated according to the finishing abrasive radius, and the gear tooth root is finished based on the theoretical calculation results. Finally, the gear is processed to obtain a high-performance gear, thereby improving the bending fatigue resistance of the gear tooth root. The process comprises the following steps: Step S1: Obtain the JC constitutive model of typical gear materials through Hopkinson pressure bar test; Step S2: Determine an accurate and reasonable tooth profile and tooth root modification amount by specifically calculating the maximum elastic deformation amount; Step S3: Establish a gear ultrasonic rolling model, calculate and analyze the stress field under different rolling parameters and the overall stress field after unloading; Step S4: Establish a finishing abrasive grinding model, calculate the material removal volume under the action of abrasive particles, and deduce the abrasive grinding depth under abrasive particle collision; Step S5: Calculate the surface roughness limit value after processing; Step S6: Conduct actual tests to detect the performance of the processed gear tooth surface.

2. According to the process method described in claim 1, the reasonable modification amount of the tooth root is determined by calculating the maximum elastic deformation.

3. According to step 3 of claim 1, the residual stress on the tooth surface after impact is calculated based on the ultrasonic rolling model pulse frequency, impact load and impact angle.

4. According to step 4 of claim 1, the residual stress and surface roughness of the tooth surface after processing are calculated and analyzed according to the abrasive radius, and finally the processing verification is realized.

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