Bolt torque coefficient accurate measurement tool and method

Abstract

The application discloses a kind of bolt torque coefficient accurate measurement tool and method, the tool includes first component, second component, third component and bolt test piece, each component and bolt test piece are respectively with the product parts same material, same processing technology, bolt test piece is product same batch qualified piece and quantity is not less than 8 pieces;First, second component is provided with through hole, third component is provided with threaded hole, three can be used alone or in combination according to bolt test piece specification, respectively used for measuring stud or bolt.The method is based on the tool, through four steps of early preparation, fastening and synchronous measurement, measurement system analysis optimization, batch retest, combined with double method detection and system calibration, realize torque coefficient accurate measurement.The application restores actual working condition, strong universality, high measurement precision, can be directly used for product production assembly, guarantee bolt connection quality and equipment operation reliability.

Description

Technical Field

[0001] This invention belongs to the field of bolt fastening technology, and particularly relates to a tooling and method for accurately measuring bolt torque coefficient. Background Technology

[0002] Bolted connections are a core method of assembling mechanical products, and their connection quality depends on the accuracy of the bolt torque coefficient. Traditional measurements are performed under standard conditions, but the materials, processes, surface roughness of the connected parts, fastener batches, and lubrication methods differ significantly from actual working conditions. This results in large dispersion and insufficient accuracy of the torque coefficient, making it unsuitable for direct use in production and prone to bolt loosening, breakage, and equipment failure. Furthermore, traditional tooling structures are fixed, making it difficult to adapt to testing multiple bolt specifications, leading to low efficiency. This invention aims to overcome these shortcomings and provide a highly accurate, adaptable, and precise measurement solution. Summary of the Invention

[0003] To at least partially solve the technical problems existing in the prior art, the present invention provides a tooling and method for accurately measuring the bolt torque coefficient.

[0004] The bolt torque coefficient precision measurement fixture of the present invention includes a first component, a second component, a third component, and a bolt test piece. The first component, the second component, and the third component are manufactured using the same material and processing technology as the product parts to which the bolt test piece is applied. Their surface roughness, dimensional accuracy, and part clamping length are consistent with the product. The bolt test piece is a qualified product from the same batch as the fasteners used in the product, and the number is not less than 8 pieces. It is used to identify the dispersion of fasteners and to perform measurement system analysis. Both the first and second components are provided with through holes, and the third component is provided with threaded holes. The first, second, and third components can be used individually or assembled according to the specifications and types of the bolt test specimens to meet the torque coefficient measurement requirements of bolt test specimens of different specifications.

[0005] Furthermore, in the aforementioned bolt torque coefficient precision measurement fixture, the inner diameter of the through hole is matched with the nominal diameter of the bolt test piece, ensuring that the bolt test piece can smoothly pass through the through holes of the first and second components, and there is no obvious gap after assembly. The specifications of the threaded hole match the thread specifications of the bolt test piece, enabling the bolt test piece to be reliably connected to the third component via threads.

[0006] Furthermore, in the aforementioned tooling for accurately measuring the bolt torque coefficient, the bolt test piece is a hexagonal head bolt or a double-ended bolt; The hexagonal head bolt includes a bolt, a washer, and a nut; The double-ended bolt includes a stud, a washer, and a nut.

[0007] The method for accurately measuring the bolt torque coefficient of the present invention includes the following steps: Step 1: Preliminary preparation. Use an ultrasonic bolt axial force tester to measure the original axial force of the bolts or studs in the bolt test piece to eliminate the influence of the original axial force on the final axial force and torque coefficient. Grind the bolts or studs in the test piece, attach strain gauges, and insulate the strain gauges and wires. Collect the factory torque coefficients of the bolts or studs in the test piece, and calculate the tightening torque of the bolts or studs in the test piece using the minimum value among the factory torque coefficients. Assemble the bolt test piece on the first, second, and third components, using the same lubricant and bolt tightening process as the product during assembly. Step 2: Tightening and Synchronous Measurement. Using metrologically calibrated tightening tools, tighten the nuts in the bolt test pieces. Record the tightening torque T after each tightening. i Simultaneously, ultrasonic bolt axial force testing and strain axial force testing methods were used to measure the axial force F of the bolt or stud, respectively. cj and F yj According to the formula K=T i / (F×d), where d is the nominal diameter of the bolt or stud and F is the axial force, and the comprehensive torque coefficient K is calculated separately. cj ′ and K yj ′; Step 3: Measurement System Analysis and Optimization. Measurement system analysis (MSA) is performed on both the ultrasonic axial force detection method and the strain axial force detection method. Based on the analysis results, the systems are improved, and K is compared. cj ′ and K yj The difference between the two is used to establish a correspondence; a measurement system that meets the accuracy requirements is determined, with priority given to the ultrasonic bolt axial force detection method, or the torque coefficient of the strain method can be calculated from the ultrasonic detection results based on the aforementioned correspondence. Step 4: Batch retesting and torque coefficient determination. Replace the bolt test pieces with those from the same batch and repeat steps 1 to 3 to measure the torque coefficient K′ multiple times. Statistically analyze the results of multiple measurements to ensure that the standard deviation of the torque coefficient corresponding to the bolt test pieces from the same batch does not exceed the set threshold A. Use the average of the multiple measurements as the accurate torque coefficient of the bolts in this batch for product manufacturing.

[0008] The tooling and method for accurately measuring the bolt torque coefficient of the present invention have the following advantages and beneficial effects: The tooling and products of this invention are made of the same material and are manufactured using the same process. The bolt test pieces are a complete set of connection pairs from the same batch, which reproduces the real friction and stress state and eliminates systematic errors from the root. The first, second, and third components can be used independently or in combination, and are compatible with hexagonal head and double-head bolts of various specifications. One set of tooling meets all scenarios of testing, reducing costs and improving efficiency. Simultaneous measurement and calibration using both ultrasonic and strain methods, combined with prior original axial force elimination technology, significantly improves the accuracy of torque coefficient calculation; Using no fewer than 8 sets of large-sample tests and MSA analysis from the same batch, the inherent dispersion of fasteners is effectively identified and controlled, ensuring stable and reliable measurement results. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for further understanding of the embodiments of the present invention and constitute a part of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a top view of the prior art bolt torque coefficient accurate measurement tooling of the present invention; Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of AA.

[0010] Explanation of reference numerals in the attached figures: 1: First component; 2: Second component; 3: Third component; 4: Bolt test piece; 5: Through hole; 6: Threaded hole. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0012] like Figures 1 to 2 As shown, the bolt torque coefficient precision measurement fixture of the present invention includes a first component 1, a second component 2, a third component 3, and a bolt test piece 4. The first component 1, the second component 2, and the third component 3 are manufactured using the same materials and processing technology as the product parts to which the bolt test piece 4 is applied. Their surface roughness, dimensional accuracy, and part clamping length are consistent with the product, thereby minimizing the difference between the test conditions and the actual working conditions and laying the foundation for the precise measurement of the torque coefficient. The bolt test piece 4 is a qualified product from the same batch as the fasteners used in the product, and the number is not less than 8 pieces. It is used to identify the dispersion of fasteners and to perform measurement system analysis, thereby ensuring the reliability of the measurement results. The first component 1 and the second component 2 are both provided with through holes 5, and the third component 3 is provided with threaded holes 6. The first component 1, the second component 2, and the third component 3 can be used individually or assembled according to the specifications and types of the bolt test piece 4, adapting to the torque coefficient measurement requirements of bolt test pieces 4 of different specifications, greatly improving the versatility and practicality of the tooling, eliminating the need to design tooling separately for bolt test pieces 4 of different specifications, reducing testing costs and improving testing efficiency. Specifically, the through holes and threaded holes can be designed according to the different specifications of the bolt test piece. For example, through holes 5 and threaded holes 6 with specifications of M20 are set around the outermost ring of the end faces of the first component 1, the second component 2 and the third component 3, respectively, and through holes 5 and threaded holes 6 with specifications of M36 are set in the inner ring, etc.

[0013] Furthermore, in the aforementioned fixture for accurately measuring the bolt torque coefficient, the inner diameter of the through hole 5 is matched with the nominal diameter of the bolt test piece 4, ensuring that the bolt test piece 4 can smoothly pass through the through holes 5 of the first component 1 and the second component 2, and that there is no obvious gap after assembly, thus avoiding shaking during the test and affecting the accuracy of the torque coefficient measurement. The specifications of the threaded hole 6 match the thread specifications of the bolt test piece 4, enabling the bolt test piece 4 to be reliably connected to the third component 3 through threads, simulating the bolt connection state in actual assembly, and providing a stable assembly basis for the accurate measurement of the torque coefficient.

[0014] Furthermore, in the aforementioned tooling for accurately measuring the bolt torque coefficient, the bolt test piece 4 is a hexagonal head bolt or a double-ended bolt; Hex head bolts consist of a bolt, washer, and nut; A double-ended bolt consists of a stud, a washer, and a nut; Specifically, when selecting hexagonal head bolts with nuts as bolt test specimens, the first component 1 and the second component 2 are assembled and applied, so that the hexagonal head bolt passes through the pad, the first component, the second component and the nut in sequence; When selecting hexagonal head bolts without nuts as bolt test specimens, use the first component 1 and the third component 3 to assemble and apply them, so that the hexagonal head bolts pass through the pad, the first component 1 and the third component 3 in sequence and engage with the threaded hole 6. When using a double-ended bolt as the bolt test piece, the first component 1, the second component 2, and the third component 3 are assembled and applied so that one end of the double-ended bolt engages with the threaded hole 6 on the third component 3, and the other end passes through the second component 2, the first component 1, the washer, and the nut in sequence.

[0015] The method for accurately measuring the bolt torque coefficient of the present invention includes the following steps: Step 1: Preliminary preparation. Use an ultrasonic bolt axial force tester to measure the original axial force of the bolts or studs in the bolt test piece to eliminate the influence of the original axial force on the final axial force and torque coefficient, thereby improving measurement accuracy. Grind the bolts or studs in the test piece to remove surface oxide layers, oil stains, and other impurities. Attach strain gauges and insulate the strain gauges and wires to prevent interference with measurement data due to poor insulation during testing, ensuring the accuracy of the strain axial force testing method. Collect the factory torque coefficients of the bolts or studs in the test piece. Calculate the tightening torque of the bolts or studs in the test piece using the minimum value among the factory torque coefficients to avoid insufficient axial force due to insufficient tightening torque or bolt overload due to excessive torque. Assemble the bolt test piece onto the first, second, and third components, using the same lubricant and bolt tightening process as the product during assembly. Step 2: Tightening and Synchronous Measurement. Using metrologically calibrated tightening tools, tighten the nuts in the bolt test pieces to ensure the accuracy of the tightening torque measurement and avoid torque coefficient deviations caused by tightening tool errors. Record the tightening torque T after each tightening. i Simultaneously, ultrasonic bolt axial force testing and strain axial force testing methods were used to measure the axial force F of the bolt or stud, respectively. cj and F yj , where F cj F was measured using the ultrasonic method. yj The strain gauge method was used to measure the strain; according to the formula K=T i / (F×d), where K is the torque coefficient, T i For the tightening torque, d is the nominal diameter of the bolt or stud, and F is the axial force. Calculate the comprehensive torque coefficient K. cj ′ and K yj ′; Step 3: Measurement System Analysis and Optimization. Measurement system analysis (MSA) is performed on both the ultrasonic axial force detection method and the strain axial force detection method. Based on the analysis results, the systems are improved, and K is compared. cj ′ and K yj The difference between the two is used to establish a correspondence; a measurement system that meets the accuracy requirements is determined, with priority given to the ultrasonic bolt axial force detection method, or the torque coefficient of the strain method can be calculated from the ultrasonic detection results based on the aforementioned correspondence. Step 4: Batch retesting and torque coefficient determination. Replace the bolt test pieces with those from the same batch and repeat steps 1 to 3 to measure the torque coefficient K′ multiple times. Statistically analyze the results of multiple measurements to ensure that the standard deviation of the torque coefficient corresponding to the bolt test pieces from the same batch does not exceed the set threshold A. Use the average of the multiple measurements as the accurate torque coefficient of the bolts in this batch for product manufacturing.

[0016] It should be noted that, unless otherwise expressly specified and limited, the term "connection" or its synonyms should be interpreted broadly in this document. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, expressions such as "first" and "second" are merely used to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Meanwhile, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. In addition, the terms "front," "rear," "left," "right," "upper," and "lower" in this document refer to the placement states shown in the accompanying drawings.

[0017] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A tooling for accurately measuring the bolt torque coefficient, characterized in that, The bolt torque coefficient precision measurement fixture includes a first component, a second component, a third component, and a bolt test piece. The first component, the second component, and the third component are manufactured using the same materials and processing technology as the product parts to which the bolt test piece is applied. Their surface roughness, dimensional accuracy, and part clamping length are consistent with the product. The bolt test piece is a qualified product from the same batch as the fasteners used in the product, and the number is not less than 8 pieces. It is used to identify the fastener dispersion and to perform measurement system analysis. Both the first and second components are provided with through holes, and the third component is provided with threaded holes. The first, second, and third components can be used individually or assembled according to the specifications and types of the bolt test specimens to meet the torque coefficient measurement requirements of bolt test specimens of different specifications.

2. The bolt torque coefficient precision measuring fixture according to claim 1, characterized in that, The inner diameter of the through hole is matched with the nominal diameter of the bolt test piece, ensuring that the bolt test piece can pass smoothly through the through holes of the first and second components without any obvious gaps after assembly. The specifications of the threaded hole match the thread specifications of the bolt test piece, enabling the bolt test piece to be reliably connected to the third component via threads.

3. The bolt torque coefficient precision measuring fixture according to claim 1, characterized in that, The bolt test specimen is a hexagonal head bolt or a double-ended bolt; The hexagonal head bolt includes a bolt, a washer, and a nut; The double-ended bolt includes a stud, a washer, and a nut.

4. A method for accurately measuring the bolt torque coefficient using a bolt torque coefficient precision measuring fixture according to any one of claims 1 to 3, characterized in that, The method for accurately measuring the bolt torque coefficient includes the following steps: Step 1: Preliminary preparation. Use an ultrasonic bolt axial force tester to measure the original axial force of the bolts or studs in the bolt test piece to eliminate the influence of the original axial force on the final axial force and torque coefficient. Grind the bolts or studs in the test piece, attach strain gauges, and insulate the strain gauges and wires. Collect the factory torque coefficients of the bolts or studs in the test piece, and calculate the tightening torque of the bolts or studs in the test piece using the minimum value among the factory torque coefficients. Assemble the bolt test piece on the first, second, and third components, using the same lubricant and bolt tightening process as the product during assembly. Step 2: Tightening and Synchronous Measurement. Using metrologically calibrated tightening tools, tighten the nuts in the bolt test pieces. Record the tightening torque T after each tightening. i Simultaneously, ultrasonic bolt axial force testing and strain axial force testing methods were used to measure the axial force F of the bolt or stud, respectively. cj and F yj According to the formula K=T i / (F×d), where d is the nominal diameter of the bolt or stud and F is the axial force, and the comprehensive torque coefficient K is calculated separately. cj ′ and K yj ′; Step 3: Measurement System Analysis and Optimization. Measurement system analysis (MSA) is performed on both the ultrasonic axial force detection method and the strain axial force detection method. Based on the analysis results, the systems are improved, and K is compared. cj ′ and K yj The difference between the two is used to establish a correspondence; a measurement system that meets the accuracy requirements is determined, with priority given to the ultrasonic bolt axial force detection method, or the torque coefficient of the strain method can be calculated from the ultrasonic detection results based on the aforementioned correspondence. Step 4: Batch retesting and torque coefficient determination. Replace the bolt test pieces with those from the same batch and repeat steps 1 to 3 to measure the torque coefficient K′ multiple times. Statistically analyze the results of multiple measurements to ensure that the standard deviation of the torque coefficient corresponding to the bolt test pieces from the same batch does not exceed the set threshold A. Use the average of the multiple measurements as the accurate torque coefficient of the bolts in this batch for product manufacturing.

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