1 Introduction

Couplings, as critical components connecting two rotating shafts in mechanical transmission systems, perform the essential functions of transmitting torque, compensating for misalignment, and damping vibrations. Among the various types of couplings, the diaphragm coupling has evolved since the mid-20th century into a core component of high-speed, heavy-duty transmission systems, owing to its exceptional performance and reliable stability. The keyway-diaphragm coupling is an important category within diaphragm couplings. It achieves circumferential fixation between the shaft and the coupling through a keyway structure, while compensating for various relative displacements between shaft systems via the elastic deformation of metallic diaphragm packs. This configuration creates a high-performance transmission device that combines the high transmission accuracy of rigid couplings with the misalignment compensation capabilities of flexible couplings.

With the ever-increasing demands on transmission systems in modern industry, research and technical application of keyway-diaphragm couplings have become increasingly intensive. Industry reports show that in critical sectors such as metallurgy, mining, marine, and aerospace, keyway-diaphragm couplings are progressively replacing traditional gear couplings as the preferred solution for high-speed, heavy-duty transmission systems. This trend is primarily driven by their unique structural advantages: the absence of relative sliding friction eliminates the need for lubrication and seals, their modular design facilitates easier installation and maintenance, and the use of metallic diaphragms enables stable operation in harsh environments such as high temperatures and corrosive conditions.

This paper, from an engineering application perspective and based on the fundamentals of transmission system theory, provides a comprehensive analysis of the technical characteristics and development status of keyway-diaphragm couplings. Through a systematic examination of their structural principles, mechanical performance, material technology, and application cases, it aims to provide engineers involved in mechanical transmission design and research with in-depth and comprehensive technical reference, promoting the scientific application and technological innovation of this high-performance coupling in a broader range of fields.

2 Structure and Working Principle of the Keyway-Diaphragm Coupling

2.1 Basic Structural Components

As a flexible coupling with metallic elastic elements, the typical structure of a keyway-diaphragm coupling consists of core elements: the diaphragm pack(s), half-hubs, connecting bolts, and keyway connection components. The diaphragm pack, serving as the elastic compensating element of the coupling, is composed of multiple, very thin metallic diaphragms (typically stainless steel) laminated together, forming a polygonal or circular ring structure. These diaphragms are regularly arranged with bolt holes around their circumference and are alternately connected to the two half-hubs via high-strength ground fitting bolts. This design cleverly divides the arc segments on the elastic element into two sets: one subjected to compression and the other to tension, with the tension-bearing part undertaking the primary torque transmission function.

The keyway connection structure is the critical interface for achieving torque input and output in this type of coupling. Depending on the design, keyway connections can be categorized into single keyway, double keyway, and multiple keyway configurations. The double keyway structure, featuring two keyways evenly distributed on the bore, effectively enhances torque transmission capacity and connection reliability. Patent CN102184176A describes an innovative double-key connecting unidirectional diaphragm flexible coupling. It features two threaded through-holes radially arranged on the connecting plate, each communicating with the bottom of a keyway, with a pressing screw installed in each threaded hole. This design significantly enhances the fastening of the key within the slot, addressing technical challenges like stress concentration and susceptibility to loosening found in traditional single-key connections.

Keyway-diaphragm couplings are available in several structural configurations, each with distinct characteristics. The JM standard type typically uses single or A/B type keyways and a diaphragm pack with four, six, or eight connecting rod forms. It offers a large load capacity, wide applicability, and long service life, covering a torque range from 25 to 1,000,000 N·m. The JMJ type with an intermediate shaft often employs a symmetrical double keyway distribution and an integral diaphragm structure, making it suitable for long-span transmissions with high compensation capability. The DJM single diaphragm type may offer optional single or double keyways and a compact single diaphragm pack structure, ideal for high-speed, light-load applications (10-8,100,000 N·m). Finally, the SJM double diaphragm type typically uses multiple evenly distributed keyways and a double diaphragm pack structure, providing superior compensation capability, especially for complex misalignment conditions.

2.2 Working Principle and Mechanical Characteristics

The working principle of the keyway-diaphragm coupling is based on the theory of elastic deformation of metallic diaphragms. When deviations in the form of axial, radial, and angular displacement occur during the operation of a mechanical transmission system, the metallic diaphragms undergo wavelike elastic deformation, thereby absorbing and compensating for these misalignments. Specifically, during torque transmission, the driving shaft transmits torque to the half-hub via the keyway, which then passes through the bolt group to the diaphragm pack, and finally through the opposite bolt group and half-hub to the driven shaft. In this process, the diaphragm pack not only transmits torque but also compensates for relative displacements between the shaft systems through its flexible properties.

In terms of mechanical characteristics, diaphragm couplings exhibit notable features of high torque rigidity and zero rotational backlash. When angular misalignment is present, the diaphragms experience alternating bending stress; with axial displacement, they endure tensile or compressive stress; and under parallel misalignment, they are subjected to shear stress and additional bending stress. These complex stress states place the diaphragms in a multi-axial stress condition during operation, imposing extremely high demands on their fatigue life.

It is worth noting that there is a significant difference in compensation capability between double diaphragm couplings and single diaphragm couplings. Single diaphragm couplings, requiring the diaphragm to bend complexly, are less adaptable to significant parallel misalignment. In contrast, double diaphragm couplings can curve in different directions simultaneously, enabling more effective compensation for parallel misalignment. This structural difference makes double diaphragm couplings clearly superior in misalignment compensation capability, particularly suitable for shaft drive applications with lower installation alignment accuracy or significant operational deformation.

3 Critical Component Design and Material Selection

3.1 Diaphragm Component Design and Material

The diaphragm, as the core elastic element of the coupling, directly determines the overall performance and service life of the unit. Diaphragms are typically manufactured from high-strength stainless steel sheet, with thicknesses generally ranging from 0.2 to 0.5 mm. Multiple sheets are laminated to form a diaphragm pack, enhancing the elastic compensation capacity. Common diaphragm shapes include polygonal (hexagonal, octagonal), circular ring, and link-rod types. Polygonal diaphragm designs facilitate uniform torque transmission and rational stress distribution, while link-rod type diaphragms perform exceptionally well in high-torque transmission applications.

Regarding material selection, diaphragms must possess high strength, high fatigue resistance, good corrosion resistance, and stable elastic properties. Commonly used stainless steels include Grade 304, 316/316L, and 1Cr18Ni9Ti. Among these, 316L stainless steel is often the preferred choice for demanding conditions like high-speed or corrosive environments due to its excellent corrosion resistance and good mechanical properties. For special applications, such as in aerospace, titanium alloys or high-strength aluminum alloys may be employed for lightweight design.

Determining the diaphragm thickness requires comprehensive consideration of multiple requirements, including torque capacity, compensation capability, and fatigue life. Increasing the diaphragm thickness improves the torque carrying capacity of the coupling but reduces its compensation flexibility. Conversely, reducing the thickness enhances compensation capability but may impair torque transmission. Therefore, in practical design, laminating multiple thin diaphragms is commonly adopted to ensure sufficient flexibility while increasing the overall load-bearing capacity. Patent documentation indicates that an improved diaphragm coupling's elastic diaphragm pack may consist of 10-15 laminated 0.3mm thick stainless steel sheets, clamped together via a clamping pin and ring, forming a flexible yet robust elastic assembly.

3.2 Keyway Connection Structure Design

The keyway connection, as the critical interface for torque transmission, directly influences the coupling's reliability and lifespan. Traditional single keyway structures are prone to stress concentration, particularly at the keyway root where fatigue cracks can easily initiate. To address this issue, new-generation keyway-diaphragm couplings incorporate various innovative designs: the symmetrically distributed double keyway structure effectively reduces the stress level on a single keyway by distributing the load evenly; optimized keyway root fillet design mitigates stress concentration by increasing the transition radius; and axially tapered keyway design optimizes stress distribution through a smooth transition in keyway depth.

Notably, the double-key connecting unidirectional diaphragm flexible coupling features radial threaded through-holes at the keyway bottom equipped with pressing screws. This innovative structure utilizes bolt preload to ensure tight contact between the key and the keyway side, significantly enhancing the connection's firmness and transmission accuracy. This design not only solves the problem of easy loosening under reversing loads in traditional key connections but also greatly improves the keyway's resistance to fretting wear, making it particularly suitable for transmission systems with frequent start-stop cycles or reversing operations.

3.3 Design and Material Selection for Other Components

Besides the diaphragms and keyways, other components of the coupling also require careful design and material selection. Half-hubs are typically manufactured from high-strength alloy steels such as 40Cr or 35CrMo, undergoing quenching and tempering to achieve good comprehensive mechanical properties. For weight-sensitive applications, high-strength aluminum alloys may be used to reduce weight. Connecting bolts, as critical fasteners, must be made from high-strength alloy steel, typically meeting Grade 8.8 or 10.9 strength classes, with surface anti-corrosion treatments applied to suit harsh environments.

Material selection is tailored for each component based on application requirements. Diaphragms primarily use 304/316 stainless steel or 1Cr18Ni9Ti, often solution treated and passivated. For special conditions like high corrosion or extreme temperatures, titanium alloys or nickel-based alloys are alternatives. Half-hubs commonly utilize 45# steel, 40Cr, or 35CrMo, subjected to quenching and tempering to HRC28-32 and surface treatments like bluing or galvanizing. In weight-critical applications, high-strength aluminum alloy is an option. Connecting bolts are made from 35CrMo or 40Cr, hardened and tempered to HRC34-38, with surfaces treated using Dacromet or nickel plating for corrosion protection; stainless steel grades A2-70/A4-80 serve as corrosion-resistant alternatives. Keys are typically 45# steel or 40Cr, quenching and tempered to HRC28-32 and blued, with stainless steel used where corrosion resistance is needed.

4 Manufacturing Processes and Balancing Treatment

4.1 Diaphragm Manufacturing Technology

The manufacturing process for diaphragms involves multiple steps such as precision stamping, heat treatment, and surface treatment. Given the extremely thin gauge and high dimensional accuracy requirements, precision progressive dies are typically used for stamping to ensure bolt hole positional accuracy and edge quality. After stamping, diaphragms undergo stress relief annealing to eliminate cold working effects and restore the material's elastic properties. For high-speed applications, diaphragm surfaces may undergo shot peening to improve fatigue strength or PVD coating to enhance wear resistance.

The assembly process of the diaphragm pack is particularly critical, requiring assurance that the parallelism and coaxiality between individual diaphragms meet design specifications. During assembly, bolts should be tightened diagonally in sequence using a torque wrench according to the manufacturer's specified sequence and torque values, ensuring uniform stress distribution within the diaphragm pack. Incorrect bolt preload leads to uneven stress distribution in the diaphragms, significantly reducing the coupling's service life. Practice has proven that using hydraulic torque wrenches or electronic torque wrenches can significantly improve preload accuracy, ensuring stable coupling performance.

4.2 Keyway Machining Process

The machining quality of the keyway directly affects the transmission accuracy and reliability of the coupling. High-precision keyways are typically manufactured using broaching or wire-cut electrical discharge machining (EDM) processes to ensure keyway side surface roughness of Ra1.6 or better and dimensional accuracy of IT7 grade. The fit between the keyway and the key requires precise calculation, generally employing a transition fit or light interference fit to balance assembly convenience and transmission accuracy.

For double keyway structures, controlling the symmetry of the two keyways is crucial, typically requiring symmetry error not to exceed 0.02mm. This necessitates the use of CNC indexing devices or specialized fixtures. The root fillet area of the keyway requires special treatment, usually employing radius end mills or electrochemical polishing to avoid stress concentration.

4.3 Dynamic Balancing Treatment

For high-speed operation of keyway-diaphragm couplings, dynamic balancing correction is an indispensable process step. According to API standards, couplings for high-speed applications must undergo dynamic balancing to G6.3 grade or higher. Balance correction is typically performed using the weight removal or weight addition method on specialized dynamic balancing machines. Properly balanced couplings can significantly reduce vibration and noise during operation, extending the service life of bearings and seals.

In practical applications, the balancing grade of the coupling should be determined based on the operating speed: G6.3 can be selected for speeds below 3000 rpm; G2.5 should be used for speeds between 3000-5000 rpm; and G1.0 balancing accuracy is required for speeds exceeding 5000 rpm. Correct balancing treatment ensures smooth operation of the coupling at high speeds, avoiding equipment vibration and premature failure caused by unbalance forces.

5 Performance Characteristics and Advantage Analysis

5.1 Technical Performance Advantages

Keyway-diaphragm couplings demonstrate multiple technical advantages in the field of mechanical transmission due to their unique structural design:

High Torque Stiffness and Zero Backlash: Utilizing metallic diaphragms as elastic elements, diaphragm couplings exhibit minimal torsional deformation during torque transmission, maintaining extremely high torsional rigidity while ensuring zero rotational backlash. This characteristic is particularly suitable for precision transmission systems and servo control systems. Compared to traditional flexible couplings, diaphragm couplings can increase torsional stiffness by over 30% and positioning accuracy by more than 50%.

Ability to Compensate for Complex Misalignments: The diaphragm pack possesses good flexibility, enabling simultaneous compensation for axial displacement, radial displacement, and angular displacement, as well as the complex combined misalignments formed by these basic displacements. Research shows that high-quality diaphragm couplings can withstand angular misalignments up to 1.5 degrees and radial displacements up to 0.5mm. This multi-directional compensation capability makes them perform exceptionally well under complex conditions such as uneven thermal expansion, foundation settlement, or equipment deformation.

No Lubrication and Maintenance-Free: Unlike gear couplings, diaphragm couplings have no relative sliding parts, requiring no lubricants or sealing devices, achieving lifelong lubrication-free maintenance. This not only reduces operating costs but also avoids the risk of lubricant leakage contaminating the environment, making them particularly suitable for industries with high cleanliness requirements like food and pharmaceuticals.

Fatigue Resistance and Long Service Life: Metallic diaphragms, through optimized design and precision manufacturing, exhibit extremely high fatigue life. Under normal operating conditions, the design life of diaphragm couplings can exceed 10^8 cycles, often surpassing the equipment's overhaul cycle in practical applications. Furthermore, diaphragm couplings feature a modular design, allowing for replacement of only the diaphragm pack when needed without replacing the entire coupling, significantly reducing maintenance costs and downtime.

5.2 Comparative Analysis with Traditional Couplings

Compared to traditional gear couplings and elastic sleeve pin couplings, keyway-diaphragm couplings show clear advantages in multiple performance indicators:

In terms of transmission efficiency, diaphragm couplings achieve over 99.5% due to the absence of relative sliding parts and metallic rigid transmission, significantly higher than gear couplings (98.5%-99.2%) and elastic sleeve pin couplings (98%-99%). Their compensation capability is particularly outstanding, enabling simultaneous compensation for axial, radial, and angular composite displacements, while gear couplings primarily compensate for angular displacement, and elastic pin couplings struggle with effective axial displacement compensation.

Regarding maintenance requirements, diaphragm couplings are completely maintenance-free due to the absence of lubrication points, whereas gear couplings require regular lubricant replacement and seal inspection, incurring higher maintenance costs. Diaphragm couplings operate silently, unlike gear couplings which generate noise due to meshing gear sliding. In allowable speed, diaphragm couplings can exceed 20,000 rpm thanks to precision dynamic balancing, far surpassing elastic pin couplings. Their service life is significantly extended due to the high fatigue resistance of metallic diaphragms, while the non-metallic elastic elements of flexible couplings are prone to aging.

Furthermore, diaphragm couplings demonstrate exceptional environmental adaptability, withstanding harsh conditions like high temperatures and corrosive media. Gear coupling lubricants can fail at high temperatures, and elastic couplings' non-metallic elements are sensitive to oils and temperature. However, diaphragm couplings also have limitations: their vibration damping capacity primarily targets high-frequency vibrations, and they are less effective at isolating low-frequency torsional vibrations compared to specially designed rubber flexible couplings. Installation requires higher alignment accuracy, necessitating strict control of shaft misalignment to avoid additional loads. Therefore, diaphragm couplings are superior for applications requiring high precision, high speed, heavy loads, or corrosive environments, while other flexible coupling types might be considered for applications requiring high low-frequency vibration isolation or having lower installation accuracy.

6 Application Fields and Selection Guidance

6.1 Typical Application Scenarios

Leveraging their exceptional performance and wide adaptability, keyway-diaphragm couplings have been successfully applied in numerous industrial fields:

High-Speed Power Transmission Systems: In high-speed power equipment such as generator sets, steam turbines, and gas turbines, diaphragm couplings reliably transmit high torque while compensating for shaft misalignments caused by thermal expansion. Precisely balanced diaphragm couplings can operate at speeds exceeding 10,000 rpm, with some special designs reaching 30,000 rpm. In such applications, the coupling must not only meet strength requirements but also possess excellent dynamic balance and fatigue resistance.

Process Industry Equipment: In pumps, compressors, fans, and other equipment in industries like petrochemicals, metallurgy, mining, and power utilities, diaphragm couplings demonstrate significant advantages in corrosion resistance and maintenance-free operation. Particularly in high-power chemical pump applications, they effectively cope with shaft misalignments caused by foundation settlement or thermal deformation, ensuring safe and stable continuous production.

Special Vehicles and Marine Vessels: In tracked vehicles, heavy off-road vehicles, and naval propulsion systems, diaphragm couplings adapt to the stringent requirements of complex load conditions and limited installation space. Typical application scenarios include diesel engine transmission systems, propulsion transmission systems, and auxiliary power systems.

Precision Machinery and Servo Systems: In equipment requiring high positioning accuracy, such as CNC machine tools, printing machinery, and textile machinery, the zero backlash and high torsional rigidity of diaphragm couplings ensure transmission precision. In recent years, new structures like the ZMJM miniature diaphragm coupling and TJM external clamp-type coupling have been widely used in stepper/servo systems and lead screw spindle drives.

6.2 Selection Considerations

Correct selection is key to ensuring optimal performance of keyway-diaphragm couplings. The following factors must be comprehensively considered during the selection process:

Torque Characteristic Analysis: The system's rated torque, peak torque, and starting torque must be calculated, considering impact load factors. The coupling's rated torque should exceed the system's maximum operating torque, and its maximum torque capacity should be higher than the potential peak torque. Generally, selection should ensure the coupling's nominal torque is at least 1.5-2 times the system's maximum working torque.

Shaft Misalignment Assessment: Accurately measure or predict the system's axial, radial, and angular misalignments, ensuring the selected coupling's compensation capability meets requirements. Note that when multiple misalignments coexist, the coupling's allowable compensation values should be correspondingly reduced. Typically, it is recommended to keep actual misalignment within one-third of the coupling's allowable value to extend service life.

Environmental Condition Considerations: Include special conditions such as ambient temperature, corrosive media, humidity, and explosion-proof requirements. Diaphragm couplings can operate stably within a temperature range of -40°C to +250°C, with special designs extending this to -196°C to +350°C. In corrosive environments, stainless steel diaphragms and appropriately surface-treated metal components should be prioritized.

Speed Characteristics and Balance Grade: Determine the balance grade requirement based on the operating speed. High-speed applications should select high-precision balance grades like G2.5 or G1.0. Simultaneously, the centrifugal stress on the coupling hub material must be checked to ensure safety and reliability at the maximum operating speed.

6.3 Installation and Maintenance Key Points

Correct installation and maintenance are crucial measures for ensuring the long-term reliable operation of keyway-diaphragm couplings:

Installation Alignment Adjustment is a key step for ensuring proper coupling operation. Although diaphragm couplings can compensate for misalignment, precise alignment significantly reduces additional loads and extends service life. Using the dial indicator method is recommended for alignment measurement, ensuring axial displacement ≤ 0.05mm, angular misalignment ≤ 0.05°, and parallel misalignment ≤ 0.1mm. Avoid violent assembly methods like hammering during installation; thermal expansion or hydraulic nuts are recommended for hub assembly.

Bolt Tightening Procedure directly affects the coupling's service life. The connecting bolts of the diaphragm coupling must be tightened in a diagonal sequence in steps, reaching the final specified torque value. Typically, bolt tightening involves three steps: pre-tightening to 30% of the design torque, then increasing to 60%, and finally reaching 100% of the design torque. Using a calibrated torque wrench is necessary to ensure tightening accuracy.

Regular Inspection is an effective measure for preventing unexpected failures. During equipment operation, periodically check the coupling's vibration level, noise changes, and bolt tightness. Using a strobe light allows inspection of the diaphragms during operation, enabling timely detection of abnormal deformation or cracks. During shutdown maintenance, carefully inspect the diaphragm surfaces for micro-cracks, corrosion marks, or plastic deformation, replacing the diaphragm pack promptly if necessary.

7 Innovation and Development Trends

With the continuous increase in demands on modern industrial transmission systems, keyway-diaphragm couplings are rapidly developing towards higher performance, intelligence, and specialization:

7.1 Structural Innovation and Performance Optimization

In recent years, numerous innovations have emerged in coupling structural design. Tapered interference fit connection technology transmits torque through friction generated by bolt preload, effectively eliminating stress concentration at the keyway area. Finite element analysis shows this structure can reduce the stress concentration factor by over 30%, making it particularly suitable for frequent reversing and variable load conditions. Additionally, composite diaphragm structures, combining diaphragms of different thicknesses, optimize the distribution of rigid and flexible zones, giving the coupling superior displacement compensation capability while maintaining high torque stiffness.

Innovative intermediate shaft structure designs address specific problems in long-distance transmission. The JMJ type integral spacer-type diaphragm coupling enables axial assembly and disassembly without significant axial movement through a rational layout, greatly facilitating maintenance. Such couplings offer significant advantages in large units and complex transmission systems, becoming an important choice for modern industrial transmission systems.

7.2 Material Innovation and Process Breakthroughs

The application of new materials opens new avenues for improving diaphragm coupling performance. Nanocoating technology applied to diaphragm surfaces significantly enhances wear resistance and anti-fretting fatigue capability. Experimental data show that diaphragms with diamond-like carbon nanocoatings can increase fatigue life by 2-3 times. The development of metal matrix composites provides solutions for special conditions. For example, carbon fiber-reinforced aluminum matrix composites reduce weight by over 35% while maintaining high strength, making them particularly suitable for weight-sensitive applications like aerospace.

Advances in manufacturing processes are equally remarkable. The application of laser welding technology in diaphragm pack connections addresses stress concentration issues in traditional bolted connections. Additive manufacturing enables optimized internal coupling structures, generating biomimetic structures through topological optimization that minimize weight and distribute stress evenly while ensuring strength.

7.3 Condition Monitoring and Intelligent Maintenance

With the advancement of Industry 4.0 and smart manufacturing, keyway-diaphragm couplings are also moving towards intelligent development. Smart couplings integrated with sensor technology can monitor operating parameters like torque, temperature, and vibration in real-time, providing data support for predictive maintenance. Torque monitoring systems based on strain gauge technology accurately measure load conditions in transmission systems, while embedded temperature sensors detect abnormal temperature rises promptly, preventing excessive wear.

The application of digital twin technology in coupling lifecycle management is another important trend. By establishing a digital counterpart of the coupling, its stress state and remaining life can be simulated in real-time, achieving a shift from preventive maintenance to predictive maintenance. This intelligent management approach can significantly reduce the risk of unexpected downtime and improve overall equipment utilization.

8 Conclusion

The keyway-diaphragm coupling, as a high-performance transmission component, compensates for shaft misalignments through the elastic deformation of metallic diaphragms. With its excellent characteristics such as high torque stiffness, zero rotational backlash, and maintenance-free operation, it has become an important choice for modern industrial transmission systems. This paper systematically analyzes the structural characteristics, working principles, material selection, manufacturing processes, and application fields of keyway-diaphragm couplings, leading to the following conclusions:

The core technical advantages of the keyway-diaphragm coupling lie in its multi-directional compensation capability and high reliability. It can simultaneously compensate for axial, radial, and angular displacements, adapting to complex shaft misalignment conditions; using metallic diaphragms as elastic elements eliminates aging issues and requires no lubrication maintenance, resulting in a long service life. These characteristics make it irreplaceable in high-speed, heavy-duty, and harsh operating conditions.

Material selection and manufacturing processes are crucial for coupling performance. High-strength stainless steel diaphragms, high-quality alloy steel structural components, and appropriate heat treatment processes form the foundation for ensuring coupling performance; precision machining technology and strict dynamic balancing treatment are key to achieving high-speed stable operation. With the continuous emergence of new materials and processes, the performance boundaries of couplings are constantly expanding.

Correct selection, installation, and maintenance are essential for realizing the coupling's optimal performance. Selection requires comprehensive consideration of torque characteristics, shaft misalignment, environmental conditions, and other factors; installation must ensure alignment accuracy and correct bolt tightening procedures; operational status should be regularly inspected during operation to detect and address abnormalities promptly. These measures can effectively extend the coupling's service life and improve equipment operational reliability.

In the future, with structural innovation, material breakthroughs, and the development of intelligent technology, keyway-diaphragm couplings will continuously progress towards higher performance, longer life, and more intelligent monitoring, providing more comprehensive solutions for modern industrial transmission systems.