A Low-Stress Machining Method and System for Impact-Type Runner Buckets Based on Machining Sequence Control

Abstract

This invention provides a low-stress machining method and system for impact turbine runner buckets based on machining sequence control. The method includes: dividing the bucket machining area into a high-stress sensitive area, a transition area, and a low-stress sensitive area based on the geometric characteristics of the impact turbine runner buckets, and determining the machining sequence priority; dividing the machining area into a high-stress area and a low-stress area according to the stress distribution characteristics of the impact turbine runner buckets, and determining the machining sequence priority again; performing staged machining based on the two determined machining sequence priorities, performing residual stress detection after each stage is completed, and determining the cutting sequence for the next stage based on the detection results. This invention solves the deformation problem caused by uneven residual stress distribution during bucket machining by using a multi-dimensional partitioning strategy and a closed-loop feedback mechanism, thereby improving the machining accuracy of the runner.

Description

Technical Field

[0001] This invention relates to the field of hydropower equipment manufacturing technology, specifically to a low-stress machining method and system for impact turbine water buckets based on processing sequence control. Background Technology

[0002] Before the overall CNC milling of the runner bucket of the ultra-large impact turbine, it needs to go through forging, preliminary milling and welding processes. The residual stress distribution is complex. During the processing, as the material is removed, the residual stress is redistributed, causing stress deformation of the bucket. This directly affects the machining accuracy of the parts and is one of the main reasons for the out-of-tolerance profile of turbine parts.

[0003] The main problems in controlling residual stress and deformation during the machining of the runner buckets of ultra-large hydro turbines can be summarized into the following three points: 1) The runners and buckets of ultra-large impulse turbines are huge in size and complex in structure, with high value and long processing cycle. The processing deformation caused by residual stress seriously affects the precision of the parts. If deformation occurs, it will seriously affect the delivery cycle. 2) The residual stress distribution of the runner of the ultra-large impulse turbine is uneven and requires processing in different areas, resulting in an unclear stress deformation pattern; 3) The demand for ultra-large impact turbine runners is often in small batches, making it difficult to determine a low-stress deformation processing scheme through trial cutting of experimental parts; Traditional machining methods typically only consider geometric constraints when selecting the cutting sequence. As machining progresses, stress balance is disrupted, leading to problems such as excessive machining deformation, which is particularly pronounced for large-sized, high-strength alloy water tanks. Current technologies lack dynamic control methods that address the coupling effect between water tank geometry and stress distribution. Therefore, a solution is urgently needed that can optimize the machining sequence by region and achieve coordinated control of residual stress. Summary of the Invention

[0004] The purpose of this invention is to provide a low-stress machining method and system for impact turbine water buckets based on machining sequence control, so as to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a low-stress machining method for impact-type turbine water buckets based on machining sequence control, comprising: Based on the geometric characteristics of the impeller bucket of an impulse turbine, the bucket processing area is divided into a high-stress sensitive area, a transition area, and a low-stress sensitive area, and the processing sequence priority is determined. Based on the stress distribution characteristics of the impeller bucket of the impulse turbine, the processing area is divided into high-stress zone and low-stress zone, and the processing sequence priority is determined. Based on the two determined processing sequence priorities, the processing is carried out in stages. After each stage is completed, residual stress is detected, and the cutting sequence of the next stage is determined according to the detection results.

[0006] Furthermore, based on the geometric characteristics of the impeller bucket of the impulse turbine, the bucket processing area is divided into a high-stress sensitive area, a transition area, and a low-stress sensitive area, including: The high-stress sensitive area is defined by the connection between the bucket root and the runner body, the transition area of ​​the bucket surface, and the area of ​​sudden change in thickness at the water outlet edge. The low-stress sensitive area is the edge of the bucket; the connection between the two is the transition area.

[0007] Furthermore, determining the processing sequence priority includes: Prioritize processing the low-stress-sensitive areas, then process the transition areas and high-stress-sensitive areas in sequence.

[0008] Furthermore, based on the stress distribution characteristics of the impeller bucket of the impulse turbine, the processing area is divided into a high-stress zone and a low-stress zone, including: Based on the absolute value of residual stress, the processing area is further divided into high-stress and low-stress areas. Within the high / low stress sensitive areas, processing is carried out in the order of high-stress area → low-stress area.

[0009] Furthermore, methods for determining the priority of processing order include: The residual stress distribution of the water bucket was determined using the blind hole method; With the goal of minimizing stress deformation, and based on the initial stress distribution, the sequence optimization is carried out by designing experiments with different processing sequences.

[0010] Furthermore, after each stage of machining is completed, residual stress is detected, and the cutting sequence for the next stage is determined based on the detection results, including: The method for detecting residual stress is the blind hole method.

[0011] Furthermore, after processing, the surface of the water tank is subjected to stress homogenization treatment through a surface heat treatment process, wherein the surface heat treatment adopts laser cladding.

[0012] Secondly, the present invention provides a low-stress machining system for impact-type turbine water buckets based on machining sequence control, comprising: The processing area division module is used to divide the processing area of ​​the bucket into high-stress sensitive area, transition area, and low-stress sensitive area based on the geometric characteristics of the bucket of the impulse turbine runner, and to determine the processing sequence priority; according to the stress distribution characteristics of the bucket of the impulse turbine runner, the processing area is divided into high-stress area and low-stress area, and the processing sequence priority is determined. The sequence determination module is used to perform phased machining based on the priority of two determined machining sequences. After each phase of machining is completed, residual stress is detected, and the cutting sequence of the next phase is determined based on the detection results.

[0013] Thirdly, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the low-stress machining method for impact-type turbine water buckets based on machining sequence control.

[0014] Fourthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the low-stress machining method for impact-type turbine water buckets based on machining sequence control.

[0015] Compared with the prior art, the present invention has the following technical effects: This invention provides a low-stress deformation machining method for the water buckets of an ultra-large turbine runner based on the sequential control of the machining area. By implementing a multi-dimensional partitioning strategy and a closed-loop feedback mechanism for the water bucket machining area, the method solves the deformation problem caused by uneven residual stress distribution during water bucket machining and improves the machining accuracy of the runner.

[0016] This invention achieves effective control of residual stress and reduces the deformation of the water bucket by about 20% through a processing sequence optimization strategy based on a two-dimensional partitioning model (stress dimension + structural dimension). This invention optimizes the water bucket processing sequence in stages, further reducing the amount of deformation during water bucket processing; The laser cladding process of this invention improves the uniformity of surface stress and extends the fatigue life of the water tank. Attached Figure Description

[0017] Figure 1 It is a two-dimensional partitioning model; Figure 2 A schematic diagram showing the division of the processing area for structural dimensions; Figure 3 A schematic diagram showing the division of high / low stress regions in the stress dimension; Figure 4 This is a flowchart of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] Example 1: This invention provides a low-stress machining method for impact-type turbine water buckets based on machining sequence control, comprising: Based on the geometric characteristics of the impeller bucket of an impulse turbine, the bucket processing area is divided into a high-stress sensitive area, a transition area, and a low-stress sensitive area, and the processing sequence priority is determined. Based on the stress distribution characteristics of the impeller bucket of the impulse turbine, the processing area is divided into high-stress zone and low-stress zone, and the processing sequence priority is determined. Based on the two determined processing sequence priorities, the processing is carried out in stages. After each stage is completed, residual stress is detected, and the cutting sequence of the next stage is determined according to the detection results.

[0020] This invention solves the deformation problem caused by uneven residual stress distribution during water bucket processing by implementing a multi-dimensional partitioning strategy and a closed-loop feedback mechanism in the water bucket processing area, thereby improving the processing accuracy of the rotary wheel.

[0021] Example 2: This invention provides a low-stress machining method for impact turbine water buckets based on machining sequence control, comprising: (1) Based on the geometric characteristics of the bucket of the impeller of the impulse turbine, the processing area of ​​the bucket is divided into a high stress sensitive area, a transition area and a low stress sensitive area. The high stress sensitive area is divided into the connection between the bucket root and the main body of the impeller, the transition area of ​​the bucket surface and the abrupt change in thickness of the outlet edge; the low stress sensitive area is the edge of the bucket; the connection between the two is the transition area. (2) The water bucket processing sequence is initially arranged according to the order of processing the low stress sensitive area first, then processing the transition area and the high stress sensitive area in sequence; (3) Based on the stress distribution characteristics of the impeller bucket of the impulse turbine, the processing area is divided into a high-stress area and a low-stress area; (4) Within the same sensitive area, optimize the processing sequence according to the principle of processing low-stress areas first and then high-stress areas; (5) Determine whether it is necessary to proceed to the next processing stage. When the determination result is "yes", perform residual stress detection on the water tank stress surface after the current stage is completed, and determine the cutting sequence of the next stage based on the detection result. (6) When the judgment result is "no", the processing is completed and the surface of the water tank is subjected to stress homogenization treatment through surface heat treatment process.

[0022] This invention optimizes the machining sequence of the water buckets by comprehensively considering the characteristics of residual stress distribution and the structural features of the water buckets in ultra-large turbine runners. This significantly reduces deformation caused by the redistribution of residual stress after part machining. It provides a prerequisite for improving the machining accuracy of turbine runners and reducing the defect rate.

[0023] Example 3: Machining of Stainless Steel Water Buckets for a Certain Type of Impulse Turbine Runner 1. Processing area division and sequence control (1) Geometric structural partitioning Based on the three-dimensional model of the turbine runner and buckets, the machining-sensitive areas are divided: High stress sensitive areas: the connection between the root of the water bucket and the main body of the impeller (a circular arc transition area with a radius of 5mm), and the area where the thickness of the curved surface of the water bucket changes abruptly (the area where the thickness of the water outlet edge changes abruptly from 12mm to 8mm). Transition zone: A smooth curved transition area (approximately 10 mm wide) between the high-stress-sensitive area and the low-stress-sensitive area. Low stress sensitive area: the area with uniform thickness at the edge of the water tank (thickness 10mm ± 0.5mm).

[0024] (2) Stress distribution zoning The initial residual stress distribution of the water bucket blank was detected using the blind hole method. High stress zone: absolute stress value ≥100MPa (mainly distributed in the root of the water bucket and the area of ​​abrupt change in thickness at the water outlet). Low stress zone: absolute stress value ≤100MPa (distributed in the middle of the water bucket and the water inlet area).

[0025] (3) Global processing sequence optimization Process according to the following priority order: Low-stress area (edge ​​of water bucket) within the low-stress sensitive area. Transition zone (middle of the water tank); Low-stress zone within a high-stress-sensitive zone (area of ​​abrupt thickness change at the water's edge). The "high-stress zone" (the root of the water bucket and the transition area of ​​the curved surface of the water bucket) is located within the high-stress sensitive area.

[0026] (4) Optimization of local processing sequence Within the high-stress sensitive area, further processing is performed in the order of high-stress area → low-stress area: Layered cutting is used in the high-stress area at the root of the water bucket (each layer has a cutting depth of 0.05 mm and a feed rate of 0.08 mm / r). For the low-stress area of ​​the thickness abrupt change zone at the water outlet edge, conventional cutting (feed rate 0.12 mm / r) is used.

[0027] (5) Optimization of the phased processing sequence The total machining volume is divided into two stages, and the residual stress is detected by the blind hole method after each stage is completed. In each processing stage, the processing sequence is optimized from both global and local perspectives using the methods described in (3) and (4).

[0028] (6) Surface stress homogenization treatment After processing, laser cladding is used: Laser power: 2.5kW; Scanning speed: 4mm / s; Cladding layer thickness: 0.2mm; The range of residual stress fluctuation on the surface is reduced after treatment.

[0029] Compared with traditional methods, the deformation of the water-cooled bucket process is reduced by 23%.

[0030] This invention significantly reduces stress deformation during water bucket machining and improves the machining accuracy of impeller water buckets through a two-dimensional partitioned machining sequence optimization strategy. It is particularly suitable for the precision machining of large-size, high-strength alloy water buckets and has significant industrial application value.

[0031] In another embodiment of the present invention, a low-stress machining system for impact turbine water buckets based on machining sequence control is provided, which can be used to implement the above-mentioned low-stress machining method for impact turbine water buckets based on machining sequence control. Specifically, the system includes: The processing area division module is used to divide the processing area of ​​the bucket into high-stress sensitive area, transition area, and low-stress sensitive area based on the geometric characteristics of the bucket of the impulse turbine runner, and to determine the processing sequence priority; according to the stress distribution characteristics of the bucket of the impulse turbine runner, the processing area is divided into high-stress area and low-stress area, and the processing sequence priority is determined. The sequence determination module is used to perform phased machining based on the priority of two determined machining sequences. After each phase of machining is completed, residual stress is detected, and the cutting sequence of the next phase is determined based on the detection results.

[0032] The module division in this embodiment of the invention is illustrative and represents only one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in the various embodiments of the invention can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0033] In another embodiment of the present invention, a computer device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions from the computer storage medium to achieve a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used in the operation of a low-stress machining method for impact-type rotary water buckets based on machining sequence control.

[0034] In another embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the low-stress machining system method for impact-type rotary water buckets based on machining sequence control in the above embodiments.

[0035] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0036] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0037] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0038] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A low-stress machining method for impact-type turbine water buckets based on machining sequence control, characterized in that, include: Based on the geometric characteristics of the impeller bucket of an impulse turbine, the bucket processing area is divided into a high-stress sensitive area, a transition area, and a low-stress sensitive area, and the processing sequence priority is determined. Based on the stress distribution characteristics of the impeller bucket of the impulse turbine, the processing area is divided into high-stress zone and low-stress zone, and the processing sequence priority is determined. Based on the two determined processing sequence priorities, the processing is carried out in stages. After the processing of each stage is completed, residual stress is detected, and the cutting sequence of the next stage is determined according to the detection results. Based on the stress distribution characteristics of the impeller bucket of the impulse turbine, the processing area is divided into a high-stress zone and a low-stress zone, including: Based on the absolute value of residual stress, the processing area is further divided into high-stress and low-stress areas. Within the high / low stress sensitive areas, processing is carried out in the order of high-stress area → low-stress area.

2. The low-stress machining method for impact-type turbine water buckets based on machining sequence control according to claim 1, characterized in that, Based on the geometric characteristics of the impeller bucket of the aforementioned impulse turbine, the bucket machining area is divided into a high-stress-sensitive area, a transition area, and a low-stress-sensitive area, including: The high-stress sensitive area is defined by the connection between the bucket root and the runner body, the transition area of ​​the bucket surface, and the area of ​​sudden change in thickness at the water outlet edge. The low-stress sensitive area is the edge of the bucket; the connection between the two is the transition area.

3. The low-stress machining method for impact-type turbine water buckets based on machining sequence control according to claim 2, characterized in that, The determination of processing order priority includes: Prioritize processing the low-stress-sensitive areas, then process the transition areas and high-stress-sensitive areas in sequence.

4. The low-stress machining method for impact-type turbine water buckets based on machining sequence control according to claim 1, characterized in that, Methods for determining processing sequence priority include: The residual stress distribution of the water bucket was determined using the blind hole method; With the goal of minimizing stress deformation, and based on the initial stress distribution, the sequence optimization is carried out by designing experiments with different processing sequences.

5. The low-stress machining method for impact-type turbine water buckets based on machining sequence control according to claim 1, characterized in that, After each stage of machining is completed, residual stress is detected, and the cutting sequence for the next stage is determined based on the detection results, including: The method for detecting residual stress is the blind hole method.

6. The low-stress machining method for impact-type turbine water buckets based on machining sequence control according to claim 1, characterized in that, After processing, the surface of the water tank is subjected to stress homogenization treatment through a surface heat treatment process, which employs laser cladding.

7. A low-stress machining system for impact-type turbine water buckets based on machining sequence control, characterized in that, include: The processing area division module is used to divide the processing area of ​​the bucket into high-stress sensitive area, transition area, and low-stress sensitive area based on the geometric characteristics of the bucket of the impulse turbine runner, and to determine the processing sequence priority; according to the stress distribution characteristics of the bucket of the impulse turbine runner, the processing area is divided into high-stress area and low-stress area, and the processing sequence priority is determined. The sequence determination module is used to perform phased machining based on the priority of two determined machining sequences. After each phase of machining is completed, residual stress is detected, and the cutting sequence of the next phase is determined based on the detection results. Based on the stress distribution characteristics of the impeller bucket of the impulse turbine, the processing area is divided into a high-stress zone and a low-stress zone, including: Based on the absolute value of residual stress, the processing area is further divided into high-stress and low-stress areas. Within the high / low stress sensitive areas, processing is carried out in the order of high-stress area → low-stress area.

8. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the low-stress machining method for impact-type turbine water buckets based on machining sequence control as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the low-stress machining method for impact-type turbine water buckets based on machining sequence control as described in any one of claims 1 to 6.

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