A mushroom head for a swaging machine and a method for optimizing the profile thereof

Abstract

A kind of mushroom head for swaging machine and its profiling optimization method belong to metal plasticity processing swaging process technical field, the profile of mushroom head and roller contact is formed by three sections of tangential connection of circular arc, the starting point to the end of circular arc profile is continuous surface without gap, and each circular arc meets first derivative continuity (tangent direction is consistent) at connecting point;By establishing multi-objective function including load fluctuation term, forging load term and geometric retention term, the profile parameters are optimized using sequential quadratic programming algorithm;The present application improves the average impact load of swaging machine on blank, peak load, reduces load fluctuation rate, significantly enhances motion stability, and can be applied to large-diameter shell swaging machine to improve forming precision and equipment life.

Description

Technical Field

[0001] This invention belongs to the field of metal plastic forming and rotary forging technology, specifically relating to a mushroom head for a rotary forging machine and its shape optimization method. Background Technology

[0002] Rotary forging achieves localized continuous plastic deformation of metallic materials through high-frequency radial compression, enabling precision forming of high-strength, low-plasticity alloys at room temperature. It is widely used in the manufacture of large-diameter shells in military, aerospace, and other fields. Existing technologies, such as the patent application titled "A Rotary Forging Equipment for Forming Large-Size Variable Cross-Section Parts" (Publication No.: CN120190304A) and the patent application titled "A Rotary Forging Machine Forging Unit for Forming Complex Parts with Large Aspect Ratios" (Publication No.: CN120190305A), utilize four forging dies arranged rotating around an axis, a main / auxiliary mushroom head, and a double roller cage structure to effectively process ultra-large-sized shells with diameters greater than 200 mm and lengths greater than 600 mm.

[0003] In the structure of the forging unit of the existing rotary forging mill, the contact state between the mushroom head (including the main mushroom head and the auxiliary mushroom head) and the rollers is complex and variable. As a key intermediate component for transmitting forging loads, the geometric features of the mushroom head's contact surface with the rollers directly determine the radial displacement law of the mushroom head, which in turn affects the peak forging load applied to the billet, the load fluctuation rate, and the service life of the mushroom head itself.

[0004] Traditional mushroom-shaped surfaces, such as those described in the patent application "An Improved Design Method and Usage Method of a Mushroom Head for a Rotary Forging Machine" (Publication No.: CN115870443A), often employ simple circular arcs or straight lines. During the high-speed rolling of the rollers along the surface, abrupt changes in surface curvature can easily lead to drastic fluctuations in contact force. This manifests as uneven impact loads during forging, affecting the shell forming accuracy and exacerbating equipment vibration. Furthermore, for large deformation processing of high-strength alloy materials, the equipment requires sufficiently high forging peak loads to ensure adequate metal flow and filling. However, the traditional mushroom-shaped surface parameters fail to adequately optimize the equivalent contact stiffness, resulting in low impact energy transfer efficiency and difficulty in meeting the requirements for high-performance shell forming. Under high-frequency impact loads, stress concentration easily occurs at geometrical discontinuities in the surface, leading to premature fatigue cracking or excessive wear of the mushroom head, reducing the equipment's continuous operation capability. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a mushroom head structure for a rotary forging machine and its optimized design method, which can significantly reduce load fluctuations during forging, increase peak forging load, and extend the service life of the mushroom head.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: A mushroom head for a rotary forging machine is installed in the forging unit of the rotary forging machine and works in conjunction with rollers and forging dies; the surface in contact with the rollers is a composite curved surface formed by three tangentially connected circular arcs in sequence.

[0007] The three arc segments include a first arc segment, a second arc segment, and a third arc segment that are tangent to each other in sequence. The center of the first arc segment is located inside the mushroom-shaped base. The center of the second arc segment is located outside the mushroom-shaped base and smoothly transitions with the first arc segment at the first tangent point. The center of the third arc segment is located inside the mushroom-shaped base and smoothly transitions with the second arc segment at the second tangent point. The surface is a continuous surface without breaks from the start point to the end point, and the first, second, and third arc segments satisfy the continuity of the first derivative at the connection point, that is, the tangent directions are consistent.

[0008] The aforementioned method for optimizing the shape of a mushroom head in a rotary forging mill involves multi-objective optimization, including: With the radius of curvature R of the first arc segment o1 The radius of curvature R of the second circular arc segment o2 The radius of curvature R of the third circular arc segment o3 The first tangent point P1(x) o1 ,y o1 )), Second tangent point P2(x o2 ,y o2 ), First center Q1(q xo1 ,q yo1 ), second center Q2(q xo2 ,q yo2 ), third center Q3(q xo3 ,q yo3 The optimization variable vector x consists of 13 parameters. Load fluctuation, forging load, and geometric retention analyses were performed to obtain the load fluctuation term f. 波动 Forging load item f 载荷 Geometric preservation term f 几何 ; Among them, the load fluctuation term f 波动 Used to measure the degree of load fluctuation under multi-roller cycle forging: In the formula, N is the number of cage rollers, and ΔF i The extreme difference of single contact load on the optimized mushroom-shaped transmission surface, ΔF 原 The extreme difference of single contact load on the original transmission mushroom head surface, α is the pressure angle, ΔR is the radial downward compression, and R O1 Let be the radius of curvature of the first circular arc segment.

[0009] Forging load item f 载荷 Used to measure the maximum energy of a single forging stroke: In the formula, F c E0 represents the Hertzian contact force between the single-drive mushroom head and the roller, and E0 represents the forging energy before optimization.

[0010] Geometric preservation term f 几何 Used to constrain displacement deviations at surface connection points, ensuring the continuity of radial displacement and its derivative: In the formula, β1 and β2 are the displacement direction coefficients before and after optimization, ΔP1 is the rigid body position deviation of the constraint connection point P1, and ΔP2 is the rigid body position deviation of the constraint connection point P2.

[0011] The weights ω of each item in the objective function are specified according to the priority orientation. i By comprehensively considering forging load, load fluctuation rate, and geometric retention, the weighted summation form of the final objective function minF(x) is obtained. The final multi-objective optimization function is minF(x): In the formula, ω1, ω2, and ω3 are the weighting coefficients for each term, and f 波动 For the load volatility term, f 载荷 For the forging load term, f 几何 This is a geometric preservation term.

[0012] Based on the original parameter values, the Sequential Quadratic Programming (SQP) algorithm is used to iteratively solve the final objective function minF(x) to obtain the optimal combination of surface parameters that minimizes the objective function.

[0013] Compared with the prior art, the present invention has the following advantages: 1. Significantly reduced load fluctuation and improved forming stability: By adopting a smooth, continuous surface composed of three tangent circular arcs and introducing a load fluctuation suppression term to optimize the arc radius and tangent point position, the velocity gradient change is smoothed when the roller moves along the surface. Dynamic simulation shows that the impact load fluctuation rate of the mushroom head on the blank is significantly reduced after optimization, the consistency of the load pulse is significantly improved, effectively suppressing equipment vibration and improving the forming accuracy of the shell.

[0014] 2. Improve peak forging load and enhance processing capability: By optimizing the mushroom head shape, the energy transfer efficiency of roller-mushroom head collision is improved, and the average load and peak load of the equipment are increased, thereby meeting the load requirements of large deformation processing of high-strength alloys.

[0015] 3. Extend the service life of the mushroom head: The optimized surface achieves first derivative continuity (with consistent tangent direction) at each arc connection point, eliminating stress concentration caused by curvature abrupt changes, making the contact stress distribution more uniform, and reducing the risk of fatigue cracking and excessive wear under high-frequency impact. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the mushroom head shape parameters according to an embodiment of the present invention.

[0017] Figure 2 This is a comparison diagram of the mushroom head shape contour before and after optimization in an embodiment of the present invention.

[0018] Figure 3 This is a comparison diagram of the radial relative velocity curves of the mushroom head before and after optimization in an embodiment of the present invention.

[0019] Figure 4 This is a comparison chart of the impact load curves of the mushroom head on the billet before and after optimization in an embodiment of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the embodiments and accompanying drawings.

[0021] A mushroom head for a rotary forging machine is installed in the forging unit of the rotary forging machine and works in conjunction with rollers and forging dies; the surface in contact with the rollers is a composite curved surface formed by three tangentially connected circular arcs in sequence.

[0022] The three arc segments include a first arc segment, a second arc segment, and a third arc segment that are tangent to each other in sequence. The center of the first arc segment is located inside the mushroom-shaped base. The center of the second arc segment is located outside the mushroom-shaped base and smoothly transitions with the first arc segment at the first tangent point. The center of the third arc segment is located inside the mushroom-shaped base and smoothly transitions with the second arc segment at the second tangent point. The surface is a continuous surface without breaks from the start point to the end point, and the first, second, and third arc segments satisfy the continuity of the first derivative at the connection point, that is, the tangent directions are consistent.

[0023] Reference Figure 1 In this embodiment, the contact surface between the mushroom head and the roller consists of three segments with radii R... o1 R o2 and R o3 It consists of tangent circular arcs, with the centers of each arc being Q1, Q2, and Q3 respectively, and the points of tangency between adjacent arcs being P1 and P2 respectively; the starting point of the shape is S, and the ending point is T.

[0024] The aforementioned method for optimizing the shape of a mushroom head in a rotary forging mill involves multi-objective optimization, including: With the radius of curvature R of the first arc segment o1 The radius of curvature R of the second circular arc segmento2 The radius of curvature R of the third circular arc segment o3 The first tangent point P1(x) o1 ,y o1 )), Second tangent point P2(x o2 ,y o2 ), First center Q1(q xo1 ,q yo1 ), second center Q2(q xo2 ,q yo2 ), third center Q3(q xo3 ,q yo3 The optimization variable vector x consists of 13 parameters, x=[R o1 ,R o2 ,R o3 ,x o1 ,y o1 ,x o2 ,y o2 ,x o3 ,y o3 ,q xo1 ,q yo1 ,q xo2 ,q yo2 ,q xo3 ,q yo3 [These are optimization variables; the initial parameter values ​​for this embodiment are shown in Table 1.]

[0025] Table 1 Initial values ​​of key parameters for the mushroom head shape parameter initial value Ro1 380mm Ro2 75mm Ro3 60mm P1(xo1,yo1) （-35.930，11.691） P2(xo2,yo2) （-19.121，15.266） Q1(qxo1,qyo1) （0，-366.6） Q2(qxo2,qyo2) （-43.2，86.4） Q3(qxo3,qyo3) （0，-41.6） Load fluctuation, forging load, and geometric retention analyses were performed to obtain the load fluctuation term f. 波动 Forging load item f 载荷 Geometric preservation term f 几何 ,in: Load fluctuation term f 波动 Used to suppress fluctuations in multi-roller cycle loads; In the formula, ΔF i The extreme difference of single contact load on the optimized mushroom-shaped transmission surface, ΔF 原 The extreme difference of single contact load on the original transmission mushroom head surface, α is the pressure angle, ΔR is the radial downward compression, and R O1 Let be the radius of curvature of the first circular arc segment.

[0026] Forging load item f 载荷 Used to maximize forging energy; In the formula, F c E0 represents the Hertzian contact force between the single-drive mushroom head and the roller, and E0 represents the forging energy before optimization.

[0027] Geometric preservation term f 几何 Used to maintain the positional deviation of the surface connection point; In the formula, β1 and β2 are the displacement direction coefficients before and after optimization, P1 is the position parameter of the constraint connection point P1 after optimization, and P O1 To optimize the position parameters of constraint connection point P1 before optimization, P2 is the position parameter of constraint connection point P2 after optimization. O2 To optimize the position parameters of the pre-constraint connection point P2.

[0028] The constraints include: 1. Geometric constraints: Each tangent point lies on the corresponding circular arc (6 equations in total); 2. Tangent continuity: The dot product of the unit tangent vectors of adjacent arcs at the point of tangency is 1 (two equations in total); 3. Boundary constraints: The variation range of each variable shall not exceed ±25% of the initial value; Considering the characteristics of the rotary forging process for complex internal cavity parts and the service requirements of the equipment, this embodiment adopts a priority-oriented weight allocation scheme: the influence of load fluctuation on forming accuracy is weighted at 60%, the requirements of forging load on the life of the transmission mushroom head and the equipment structure are weighted at 30%, and the weight of geometric retention as the basic constraint of the final quality indicator is 10%. In summary, the objective function for optimization is: Based on the original parameter values, the Sequential Quadratic Programming (SQP) algorithm is used to iteratively solve the final objective function minF(x) to obtain the optimal combination of surface parameters that minimizes the objective function; In this embodiment, the SQP algorithm is implemented on the MATLAB 2024 platform, with a maximum number of iterations of 1000 and a difference step size of 0.001s. The optimization converges after 72 function evaluations, and the objective function value decreases from the initial 1.47 to 0.11.

[0029] The optimal parameter combination after optimization is shown in Table 2.

[0030] Table 2 Comparison of mushroom head surface parameters before and after optimization parameter Before optimization After optimization Ro1 380mm 314.68mm Ro2 75mm 74.83mm Ro3 60mm 48.39mm P1(xo1,yo1) （-35.93，11.69） （-25.00，14.05） P2(xo2,yo2) （-19.12，15.27） （-11.53，17.00） Q1(qxo1,qyo1) （0.00，-366.60） （-5.00，-300.00） Q2(qxo2,qyo2) （-43.20，86.40） （-34.23，88.31） Q3(qxo3,qyo3) （0，-41.60） （0.00，-30.00） f(x) 1.47 0.11 Reference Figure 2 , Figure 2 The comparison of the surface before and after optimization is shown, and it can be seen that the curvature transition of the surface is smoother after optimization.

[0031] To verify the effectiveness of the optimization results of the above embodiments, a multibody dynamics model of the forging die mechanism was established based on the Adams platform. The model is based on the existing rotary forging machine forging unit, simplifying the 18 rollers and roller cage into a single rigid body, and merging the mushroom head, tongue plate and die into an integral structure.

[0032] Drive parameters: Inner spindle speed 320 rpm (1920° / s), outer spindle speed 240 rpm (-1440° / s), the two rotate in opposite directions.

[0033] Material parameters: The mushroom head is made of W6Mo5Cr4V2 (elastic modulus 218 GPa, density 8160 kg / m³), the rollers are made of G20Cr2Ni4A (elastic modulus 206 GPa, density 7850 kg / m³), and the blank is made of 30CrNi2MoVE (elastic modulus 206 GPa, density 7850 kg / m³). Contact parameters are shown in Table 3.

[0034] Table 3 Contact Parameters Parameter type Roller-Mushroom Head (Before Optimization) Roller-Mushroom Head (Optimized) Mushroom head - blank Stiffness (N / mm) 2.556×108 2.406×108 4.3×107 Force Index 2.2 2.2 2.2 Damping (N·s / mm) 10 10 1.508×105 Penetration depth (mm) 0.30 0.27 0.80 coefficient of kinetic friction 0.08 0.08 0.08 static friction coefficient 0.1 0.1 0.1 Simulation results are as follows Figure 3 , Figure 4 As shown; Figure 3 The radial velocity curve of the mushroom head centroid relative to the billet centroid is shown. After optimization, the maximum negative radial relative velocity increased from 4039 mm / s to 4467 mm / s, and the consistency of the waveform in each cycle was significantly improved, indicating enhanced motion stability.

[0035] Figure 4 The impact load curve of the mushroom head on the billet was optimized as follows: maximum impact load increased from 95.4t to 102.1t (+7.0%); average impact load increased from 88.7t to 101.1t (+15.1%); load fluctuation rate (standard deviation / mean) decreased significantly from 35.34% to 7.14% (-28.2 percentage points). The load curve exhibits a more uniform periodic pulse characteristic, which meets the process requirements of "uniform impact and stable forming".

[0036] In summary, this embodiment demonstrates that the mushroom-shaped surface optimized by the SQP algorithm can effectively improve the peak forging load, reduce the load fluctuation rate, and ensure motion stability.

Claims

1. A mushroom head for a rotary forging machine, characterized in that: The surface in contact with the roller is a composite surface formed by three tangentially connected circular arcs.

2. A mushroom head for a rotary forging machine according to claim 1, characterized in that: The three arc segments include a first arc segment, a second arc segment, and a third arc segment that are tangent to each other in sequence. The center of the first arc segment is located inside the mushroom-shaped base. The center of the second arc segment is located outside the mushroom-shaped base and smoothly transitions with the first arc segment at the first tangent point. The center of the third arc segment is located inside the mushroom-shaped base and smoothly transitions with the second arc segment at the second tangent point. The surface is a continuous surface without breaks from the start point to the end point, and the first, second, and third arc segments satisfy the continuity of the first derivative at the connection point, that is, the tangent directions are consistent.

3. The method for optimizing the shape of a mushroom head in a rotary forging machine as described in claim 2, characterized in that, include: With radius of curvature R o1 R o2 R o3 The coordinates of the point of tangency are P1(x) o1 ,y o1 P2(x) o2 ,y o2 ), the center coordinates are Q1(q) xo1 ,q yo1 ), Q2(q xo2 ,q yo2 ), Q3(q xo3 ,q yo3 A total of 13 parameters are used as optimization variables; a load fluctuation term f is established. 波动 Forging load item f 载荷 and the geometric preservation term f 几何 The multi-objective function is solved by using a sequential quadratic programming algorithm to obtain the optimal surface parameters, under the conditions of satisfying geometric constraints, tangent continuity constraints, and variable boundary constraints.

4. The surface optimization method according to claim 3, characterized in that: Load fluctuation term f 波动 Used to measure the degree of load fluctuation under multi-roller cycle forging; In the formula, N is the number of cage rollers, and ΔF i The extreme difference of single contact load on the optimized mushroom-shaped transmission surface, ΔF 原 The extreme difference of single contact load on the original transmission mushroom head surface, α is the pressure angle, ΔR is the radial downward compression, and R O1 The radius of curvature of the first arc segment; Forging load item f 载荷 Used to measure the maximum energy output in a single forging stroke; In the formula, F c E0 represents the Hertzian contact force between the single-drive mushroom head and the roller, and E0 represents the forging energy before optimization. Geometric preservation term f 几何 Used to constrain displacement deviations at surface connection points, ensuring the continuity of radial displacement and its derivative; In the formula, β1 and β2 are the displacement direction coefficients before and after optimization, ΔP1 is the rigid body position deviation of the constraint connection point P1, and ΔP2 is the rigid body position deviation of the constraint connection point P2. The weights ω of each item in the objective function are specified according to the priority orientation. i By comprehensively considering forging load, load fluctuation rate, and geometric retention, the weighted summation form of the final objective function minF(x) is obtained. The final multi-objective optimization function is minF(x): In the formula, ω1, ω2, and ω3 are the weighting coefficients for each term, and f 波动 For the load volatility term, f 载荷 For the forging load term, f 几何 This is a geometric preservation term; Based on the original parameter values, the Sequential Quadratic Programming (SQP) algorithm is used to iteratively solve the final objective function minF(x) to obtain the optimal combination of surface parameters that minimizes the objective function.

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