Shape-Memory Alloys—Application in Shrink-Fit Joints †
Abstract
:1. Introduction
2. Theoretical Framework
2.1. Interference Connection: Friction Forces
- The friction force is proportional to the normal pressure, and the coefficient of friction μ is constant within a certain range of relative velocities and loads.
- Friction depends on the materials and the condition of the contacting surfaces.
- Friction forces always have a direction opposite to the respective relative velocity.
- Static friction forces are greater than kinetic friction forces.
- Friction increases with an increase in the contact time between the surfaces.
2.2. Shape-Memory Alloys
3. Purpose of the Measurements
- Substrate diameter, which together with the recovered diameter of the rings defines the amount of interference.
- Surface roughness (Ra) of the part of the shaft where the metal ring is assembled.
4. Conducting the Measurements
4.1. UniLok-Type Heat-Shrinkable Ring Used to Create a Shrink-Fit Connection
4.2. Description of the Experimental Setup and Conducting of Measurements
- The rings were mounted on the lower clamps (Figure 5).
- The lower clamps together with the rings were placed in a heating module (Figure 6). The operating temperature was adjusted to 165 °C and the heating module was switched on. The temperature was controlled with a mercury thermometer. Once the operating temperature was reached, it was held for 30 min and the heating module was switched off. After reaching room temperature, the lower clamps together with the rings were removed from the heating module.
- The lower clamp, together with the ring pressed against it, was mounted in the transition clamp of the device. The lower clamp was screwed onto the machine’s mobile gripper.
- The upper clamp of the device was mounted on the fixed grip of the machine.
- The transition clamp was lifted and rotated so that the connection holes of the transition and upper clamps stood on the same axis. The pin was then inserted (Figure 7).
- The whole device was subjected to pure tension—the force increased smoothly at a rate of 100 kg/min. If the ring slipped, the test was stopped, and the gripper was unloaded. The force F1 was then recorded.
- Step 6 was repeated consecutively three more times and the axial forces F2, F3, and F4 at which the slip occurred were recorded. At the last load, the ring was removed from the lower clamp.
- Steps 3, 4, 5, 6, and 7 were then repeated.
5. Measurement Results
6. Conclusions
- The substrate diameter influenced the friction force. This influence is explained by the specific properties of the shape-memory alloy, which define the stress increase during the recovery phase.
- The axial force F1 in eleven out of twelve cases was higher than F2, F3, F4. This can be explained by the fact that friction increases with an increase in the contact time between the surfaces.
- In the classic press-fit joint, achieving the desired interference is associated with additional processing of the surfaces and, hence, with an increase in the cost of the product. The press-fit joint, which includes elements produced from shape-memory alloys, has the advantage of being less sensitive to the quality of the machined surface.
- Concerning the axial force, the limited number of samples does not allow for a general conclusion about the impact of each parameter (substrate diameter and surface roughness) considered in the experiments.
- Rings made of shape-memory alloy can be used for the axial fixation of rotating machine parts. When the parts are assembled, a joint is obtained which has the character of a shrink-fit joint. The resulting clamping force generates the friction force required for the axial fixation of the elements. The use of an SMA facilitates the assembly of the fixing elements. It also leads to a reduction in human error, a factor that is increasingly being investigated and plays a role in the overall risk assessment when developing a new product.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
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Product Description | D Minimum Supplied mm | D Maximum Recovered mm | T Supplied mm | L Supplied mm | Min. Substrate Diameter mm | Nominal Clamping Force N |
---|---|---|---|---|---|---|
AHM1925-0328-0209 | 19.25 | 18.34 | 3.12/3.43 | 1.98/2.19 | 18.67 | 7120 |
Number | Substrate Diameter mm | Roughness (Ra) μm | Axial Force, F1 N | Axial Force, F2 N | Axial Force, F3 N | Axial Force, F4 N |
---|---|---|---|---|---|---|
1 | 19.18 | 6.60 | 2355 | 1613 | 1580 | 1602 |
2 | 19.13 | 2.00 | 1315 | 1143 | 1053 | 1322 |
3 | 18.80 | 7.70 | 1491 | 1172 | 1136 | 1167 |
4 | 18.79 | 1.40 | 1226 | 942 | 938 | 943 |
5 | 19.15 | 6.95 | 2091 | 1670 | 1639 | 1487 |
6 | 19.14 | 2.50 | 1760 | 1276 | 1242 | 1359 |
7 | 19.16 | 1.00 | 1627 | 1239 | 1215 | 1249 |
8 | 19.15 | 7.40 | 2359 | 1585 | 1624 | 1560 |
9 | 18.79 | 2.50 | 1055 | 927 | 841 | 870 |
10 | 18.81 | 7.50 | 1941 | 1151 | 1200 | 1186 |
11 | 18.77 | 8.05 | 1364 | 1273 | 1023 | 1109 |
12 | 18.81 | 1.50 | 838 | 975 | 1001 | 1076 |
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Tomova-Damyanova, E.; Ivanov, V.; Tonkov, G.; Tsonev, V.; Kuzmanov, N. Shape-Memory Alloys—Application in Shrink-Fit Joints. Eng. Proc. 2024, 70, 10. https://doi.org/10.3390/engproc2024070010
Tomova-Damyanova E, Ivanov V, Tonkov G, Tsonev V, Kuzmanov N. Shape-Memory Alloys—Application in Shrink-Fit Joints. Engineering Proceedings. 2024; 70(1):10. https://doi.org/10.3390/engproc2024070010
Chicago/Turabian StyleTomova-Damyanova, Elitsa, Vladislav Ivanov, Georgi Tonkov, Veselin Tsonev, and Nikola Kuzmanov. 2024. "Shape-Memory Alloys—Application in Shrink-Fit Joints" Engineering Proceedings 70, no. 1: 10. https://doi.org/10.3390/engproc2024070010
APA StyleTomova-Damyanova, E., Ivanov, V., Tonkov, G., Tsonev, V., & Kuzmanov, N. (2024). Shape-Memory Alloys—Application in Shrink-Fit Joints. Engineering Proceedings, 70(1), 10. https://doi.org/10.3390/engproc2024070010