Email this article Non-destructive testing of the condition of a helical coil spring
- Authors: Pavlyuk R.1, Zakharin A.V.1, Lebedev P.A.1
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Affiliations:
- FSBEI HE «Stavropol State Agrarian University»
- Section: New machines and equipment
- Submitted: 20.05.2024
- Accepted: 22.03.2025
- Published: 12.04.2025
- URL: https://journals.eco-vector.com/0321-4443/article/view/632289
- DOI: https://doi.org/10.17816/0321-4443-632289
- ID: 632289
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Abstract
BACKGROUND: When springs are used, a cyclic load of “compression - decompression” occurs, which results in a gradual decrease in its elastic properties, performance, microcracks and destruction. Moreover, if these are the springs of the valve mechanism of the internal combustion engine, then they are subject to heating, which intensifies the processes of loss of elasticity and destruction. In practice, spring control often comes down to its external inspection, assessment of geometric parameters and dynamic testing. The latter requires expensive equipment and a long time for the test itself.
AIM: improvement of the non-destructive testing method for determining the state of a coil spring through a new technical solution at the level of patentability.
METHODS: The presence of microcracks and their growth during cyclic loading leads to a change in the microshape of the cross-section of the spring coil, which affects the electrical properties, in particular, its electrical resistance. Therefore, determining the performance of a spring comes down to determining the number and volume of microcracks. Measuring the microgeometry of the spring can be achieved using a highly sensitive microohmmeter with a division value of at least 10-6 ohms. Only in the middle part of the spring do the greatest tangential stresses arise during its work in compression or tension during the relative movement of the coils. Accordingly, the middle part is more susceptible to the formation of microcracks.
RESULTS: To implement the proposed non-destructive testing of the condition of a helical coil spring, a device is required, including a microohmmeter-meter and a mechanical type power structure for its tension and compression. The tension and compression of the spring is monitored with a dynamometer. The terminals from the microohmmeter for measuring resistance are fixed on the spring coils under test. By establishing the resistance value of a new spring and subsequent monitoring during operation, it will be possible to identify the faulty element at an earlier stage and the feasibility of its restoration.
CONCLUSIONS: The proposed technical solution simplifies the assessment of the condition of the entire spring without destroying it, reduces the time for assessing its condition as a whole, and reduces the energy intensity of this process.
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BACKGROUND:
In modern mechanical engineering, various components and mechanisms in which the working element is a coil spring are widely developed. These are basically coil compression springs.
When using these springs, a cyclic load of “compression - decompression” occurs, which results in a gradual decrease in its elastic properties, performance, microcracks and destruction [1, 2, 3, 4, 5]. Moreover, if these are the springs of the valve mechanism of the internal combustion engine, then they are subject to heating, which intensifies the processes of loss of elasticity and destruction.
That is, after a certain number of cycles, the spring must be checked for its elastic properties, performance and the presence of dangerous microcracks.
In practice, spring control often comes down to its external inspection, assessment of geometric parameters and dynamic testing. The latter requires expensive equipment and a long time for the test itself.
There are two main signs of loss of spring performance - destruction of one of the turns and deformation (sediment) [6, 7]. Detection of the first sign occurs mainly visually and further operation of the spring is impossible. The second symptom occurs due to plastic deformations and the presence of microcracks in the spring body and requires specialized equipment to identify it. A spring with this defect can be restored for a certain period of time through contact bonding [8, 9, 10], if the number of microcracks is small.
AIM: improvement of the non-destructive testing method for determining the state of a coil spring through a new technical solution at the level of patentability.
METHODS:
The presence of microcracks and their growth during cyclic loading leads to a change in the microshape of the cross-section of the spring coil, which affects the electrical properties, in particular, its electrical resistance.
Therefore, determining the performance of a spring comes down to determining the number and volume of microcracks.
Measuring the microgeometry of the spring can be achieved using a highly sensitive microohmmeter with a division value of at least 10-6 ohms.
The spring consists of three parts - the upper and lower end, fixed parts and the middle, working, movable parts. The end parts are made of a wedge-shaped coil with a smaller or zero pitch for better contact of the spring with the working flat part of the support. Therefore, mainly local contact stresses arise in the end part of the spring, i.e. this part practically does not work and can be excluded from studies on changes in resistance.
Only in the middle part of the spring do the greatest tangential stresses arise during its work in compression or tension during the relative movement of the coils. Accordingly, the middle part is more susceptible to the formation of microcracks and needs to be examined in more detail.
So, if during the settling of the spring the number of microcracks is minimal, then a change in resistance along the coils will not be detected and it is advisable to restore it using various technologies and use it further in work. If a significant change in the resistance of the turns is detected, one can judge the presence of a large number of microcracks and its restoration will not be rational even with minimal settlement and visual integrity of the turns [11].
To achieve this method, it is necessary to measure the electrical resistance of the new spring on the working coils of the middle part in an unstressed state, under tension and compression. During the measurements, the resistance value of the spring is established, and it must be constant under all force influences. This indicates the integrity of the spring coils and the absence of microcracks in them. Then the worn spring is measured and the obtained values are compared, by which one can judge its performance and further restoration. Also, a change in the resistance values of a worn spring in an unloaded state and during tension and compression directly indicates its wear, i.e. thereby being a method of integral non-destructive monitoring of the technical condition of the spring. To more accurately determine the values, the spring resistance should be measured three times. An analysis of the state of the spring can be done as a whole or for each coil separately, which will allow one to differentiate their values and find out the location of the concentration of microcrack development.
About the authors
Roman Pavlyuk
FSBEI HE «Stavropol State Agrarian University»
Author for correspondence.
Email: roman_pavlyuk_v@mail.ru
ORCID iD: 0000-0002-2739-0200
SPIN-code: 5892-3171
Scopus Author ID: 57188724550
ResearcherId: N-71 80-2016
Candidate of Technical Sciences, Associate Professor
Russian Federation, 355017, Russia, Stavropol, lane. Zootechnical 12Anton Viktorovich Zakharin
FSBEI HE «Stavropol State Agrarian University»
Email: anton-zaharin@mail.ru
ORCID iD: 0000-0002-4128-9846
SPIN-code: 2191-4350
Scopus Author ID: 57188716848
ResearcherId: ABH-7186-2020
Associate Professor, Associate Professor of the Department of "Technical Service, Standardization and Metrology"
Russian Federation, 355017, Russia, Stavropol, lane Zootechnical 12Pavel Anatolyevich Lebedev
FSBEI HE «Stavropol State Agrarian University»
Email: zoya_lebedeva@mail.ru
ORCID iD: 0000-0003-0662-8694
SPIN-code: 8271-5431
Scopus Author ID: 56583970600
ResearcherId: N-8599-2016
Associate Professor, Associate Professor of the Department of "Technical Service, Standardization and Metrology"
Russian Federation, 355017, Russia, Stavropol, lane Zootechnical 12References
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СМИ зарегистрировано Федеральной службой по надзору в сфере связи, информационных технологий и массовых коммуникаций (Роскомнадзор).