PERFORMANCE EVALUATION OF OVERLOAD ABSORBING GEAR COUPLINGS

International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 12, December 2018, pp. 1240 1255, Article ID: IJMET_09_12_126 Available online at http://www.ia aeme.com/ijmet/issues.asp?jtype=ijmet&vtype= =9&IType=12 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 IAEME Publication Scopus Indexed PERFORMANCE EVALUATION OF OVERLOAD ABSORBING GEAR COUPLINGS JunWoo Bae, JongSigKwon, JinHoSeo JAC Coupling Co., Ltd., South Korea HyoungWoo Lee Department of Aero Mechanical Engineering, Jungwon University, South Korea KeunHyo Lee, Sookeun Park Korea Institute of Industrial Technology, South Korea ABSTRACT Most existing gear couplings either lack the function to cut off power transmission in the event of an overload, or are equipped with a shear pin-type power cut-off system. A structure without a power cut-off function is high risk, because an overload of the system may lead to damage of the components connected to the coupling, thus jeopardizing the safety of the overall system, and adding to the maintenance costs incurred from the corresponding production suspension. In the present study, an overload absorbing gear coupling was designed, and fatigue tests and analyses were conducted. It was confirmed that the system s parts did not exhibit any deformation or abnormal behavior, i.e., slip. Also, modal testing was carried out on the coupling developed in the present study, and no resonance was observed, given that the first natural frequency was determined to be 1,170 Hz, and the operation speed was 33.3Hz (2,000 rpm). To further confirm the reliability of the findings, various tests were conducted on the overload absorbing gear coupling specimens, including an axial displacement test, angular displacement test, maximum torque test, sliding torque test, and sliding life test. Keywords: Gear coupling, Taper shrink, Slip pad, Excess load absorption, Performance evaluation. Cite this Article: JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park, Performance Evaluation of Overload Absorbing Gear Couplings, International Journal of Mechanical Engineering and Technology, 9(12), 2018, pp. 1240 1255. http://www.iaeme.com/ijme et/issues.asp?jtype=ijmet&vtype=9&itype e=12 http://www.iaeme.com/ IJMET/index.asp 1240 editor@iaeme.com

JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park 1. INTRODUCTION The main function of a gear coupling is to connect the drive shaft and the driven shaft of a system and thus enable power transmission. In mechanical devices in industrial facilities, the gear coupling connecting the two shafts is typically subjected to a supporting load, which can vary depending on the setup conditions of the devices, thermal expansion, supports surrounding the devices, and other various factors. To minimize this supporting load, a coupling used as a connecting medium needs to provide excellent displacement (alignment) adjustment, while allowing power transmission from the drive to the driven shaft with minimum power loss. Notably, the gear couplings used in steel mills, power plants, and shipbuilding yards must be able to transmit tremendous power while being subjected to highspeed rotation, and even in the event of an overload, it must protect surrounding facilities such as gearboxes and motors from damage. Overloads are known to reduce the life of such surrounding devices, or cause them to fail. This can lead to increased facility maintenance costs as well as increased production costs, due to suspended facility operations [1-3]. Among various coupling types, the gear coupling has advantages in that its compact size and light weight allows it to fit in any narrow space, and it is capable of transmitting relatively larger power for its size, when compared to other types. Most existing gear couplings either lack the function to cut off power transmission in the case of an overload, or are equipped with a shear pin-type power cut-off system. A structure without a power cut-off function is inherently risky because a system overload may damage the components connected to the coupling, thus jeopardizing the safety of the entire system [4-7]. The present study aims to develop an overload absorbing gear coupling, designed to minimize the suspension of operation and damage to its components, and further prevent the generation of vibration and noise. To this end, fatigue analyses and full-scale vehicle modal testing were conducted on overload absorbing gear coupling specimens. To further investigate the reliability of the findings of the present study, various tests were conducted, including an axial displacement test, angular displacement test, maximum torque test, sliding torque test, and sliding life test. 2. FATIGUE ANALYSIS AND STABILITY ASSESSMENT OF OVERLOAD ABSORBING GEAR COUPLINGS 2.1. Fatigue Analysis of Overload Absorbing Gear Couplings Here, the fatigue life is determined using the Damage Model based on the Palgrem Miner Rule. = < 1 (1) Here, D = Damage Value ni = Available number of Grade I load cycles Ni = Allowable number of Grade I load cycles When determining damage accumulation,, which represents the entire stress range available under a given operating load, is typically used along with the corresponding respective number of load cycles,. In the meantime, the fatigue life was calculated with reference to the gear sleeve component, which normally has the lowest safety factor. http://www.iaeme.com/ IJMET/index.asp 1241 editor@iaeme.com

Performance Evaluation of Overload Absorbing Gear Couplings Figure 1S-N Curve for Notched and Un-notched Base Metal Figure 2 S45C S-N curve Table 1Based on 7.1(3) in EN1993-1:9 Strength Cycle Reference Strength 340 MPa 5 x 10 5 Cut off Limit 187 MPa 1 x 10 8 = 5 10 with m = 5for 5 10 10 Under the maximum torque of 111 knm, the load analysis result showed that the gear sleeve component incurred the highest stress at 445 MPa. Next, the stress can be calculated using the equation shown below, which relates the maximum torque and the maximum stress given. = ""#[%&'] ()),!!! http://www.iaeme.com/ IJMET/index.asp 1242 editor@iaeme.com

JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park Torque [Nm] Figure 3 Stress Analysis Result of Gear Sleeve Component (445 MPa) Cycle Table 2 Palgrem-Miner Damage Value Equivalent Stress [MPa] Allowable No. of Cycles Fatigue Damage Damage Percentage 55,500 1E+06 300.38 1.97.E+6 5.074E-01 100% Accumlated Damage 0.507 100% Accumulated damage was calculated based on the rated torque of 55.5 knm / 1,000,000 Cycles, i.e., the standard reference value for fatigue and durability testing. As a result, the accumulated damage was determined to be 0.507, less than 1.0, meaning that the given system can be considered safe. 2.2. Abrasion Test Using Overload Absorbing Friction Plates The life of an overload absorbing gear coupling has a close relationship with its wear coefficient. More specifically, an overload absorption system based on slide control loses its ability to transmit power when the corresponding surface pressure is reduced by abrasion, and this reduces the set overload value to a level equivalent to or below the operating torque. Accordingly, in the present study, the wear coefficient of the overload absorbing gear couplings was determined using abrasion tests, and their service life was calculated using relevant equations. Subsequently these results were verified based on the results of fatigue and durability testing. Once the friction coefficient is obtained by abrasion testing, relevant stress equations and the boundary conditions for finite element analysis can be determined. The abrasion test specimens and the abrasion tester used in the present study are shown in Fig. 4 and Fig. 5, respectively. Figure 4 Abrasion Test Specimens http://www.iaeme.com/ IJMET/index.asp 1243 editor@iaeme.com

Performance Evaluation of Overload Absorbing Gear Couplings Figure 5 Ball on Disc Abrasion Tester Here, the parameters related to the amount of abrasion include the following: 1.0 N of load, 100.0 mm/s of sliding speed, 1,000 m distance, 75 kg/mm2 hardness, the nature of the movement, lubrication conditions on the sliding surface, and the material type and surface roughness of the counterpart material. The abrasion equation was determined, as below. * = +&, -. Here, W is the amount of abrasion (mm), K is the wear coefficient, P is the load per unit area (kg/mm2) where the specimen and its counterpart are in contact with each other, V is the sliding speed (mm/sec), and H is the hardness. The results of the abrasion testing are shown in Fig. 6 and Table 3. (-) Figure 6 Graph of Abrasion Test Results Table 3Abrasion Test Results Friction Coefficient 0.296 Wear amount 0.0058g Wear Coefficient 7.85E-04 http://www.iaeme.com/ IJMET/index.asp 1244 editor@iaeme.com

JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park 2.3. Fatigue Test of Overload Absorbing Gear Couplings Fatigue testing was conducted on two specimens of the overload absorbing gear coupling parts under the same axial and angular displacement conditions (where the displacement was set to zero) and up to 1,000,000 cycles each, and the results are shown below. Fig. 7 shows the fatigue life and FD-T curve at the initial condition while Figs. 8, 9, and 10 show the fatigue life and FD-T curves after 300,000 cycles, 500,000 cycles, and 700,000 cycles, respectively. Figure 11 shows the final results after 1,000,000 cycles. These results confirmed that these specimens did not exhibit any deformation or abnormal behavior, i.e., slip. Figure 7 Fatigue Life and FD-T Curve at the Initial Condition Figure 8 Fatigue Life and FD-T Curve after 300,000 Cycles Figure 9 Fatigue Life and FD-T Curve after 500,000 Cycles http://www.iaeme.com/ IJMET/index.asp 1245 editor@iaeme.com

Performance Evaluation of Overload Absorbing Gear Couplings Figure 10 Fatigue Life and FD-T Curve after 700,000 Cycles Figure 11 FatigueLife after 1,000,000 Cycles (Final Result) 2.4. Measurement of Natural Frequency Modal testing was carried out on the products developed in the present study in efforts to ensure the stiffness of these products, assess the stiffness of their core components, and further assess the likelihood of resonance in them. Vibration measurement was performed using a B&K Pulse 3560C FFT, a frequency analyzer; B&K 8206-002, an impact hammer; and B&K 4507B006, an accelerometer. To be more specific, each overload absorbing gear coupling product was equipped with a sensor, as shown in Fig. 12, and the upper part of each product was excited using the impulse hammer. The resulting responses were analyzed using relevant software and controllers to obtain frequency response values. Also, Product 1, 2, and 3 were separately prepared, and each of them was equipped with sensors on four different points, and the testing was conducted in the same manner described above. As shown in Fig. 13, it was concluded that there was no resonance occurring in these products given the observation that the first natural frequency was determined to be 1,170 Hz, and the operation speed was 33.3Hz (2,000 rpm). Figure 12 Measurement of Natural Frequency using an Impulse Hammer http://www.iaeme.com/ IJMET/index.asp 1246 editor@iaeme.com

JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park Figure 13 Results of Natural Frequency Measurement 3. PERFORMANCE EVALUATION OF OVERLOAD ABSORBING GEAR COUPLINGS 3.1. Manufacturing of Measuring Instruments for Performance Testing A fixed and reactive measuring instrument was designed and manufactured to conduct performance testing on the final prototypes of the proposed overload absorbing gear couplings, as shown in Fig. 14. The developed instrument allows the intended displacement of specimens to reproduce an experimental environment where axial and angular alignment errors exist during displacement testing. Also, the instrument was designed and fabricated to have sufficient strength to withstand maximum torque tests, sliding life tests, and fatigue and durability tests. Figure 14 Fixed and Reactive Measuring Instrument for Performance Testing of Prototypes 3.2. Axial Displacement Test of Overload Absorbing Gear Couplings Axial displacement testing was conducted on five specimens of the proposed overload absorbing gear couplings, as shown in Fig. 15, and the result was 112 KN. There was no deformation or abnormal behavior observed during the test. Figure 15 Images before and after the application of the axial displacement http://www.iaeme.com/ IJMET/index.asp 1247 editor@iaeme.com

Performance Evaluation of Overload Absorbing Gear Couplings SPL#1 (9.4mm @112.1kN) SPL#2 (8.8mm @112.2kN) SPL#3 (8.7mm @112.1kN) SPL#4 (8.73mm @112kN) SPL#5 (8.7mm @112kN) Figure 16 F-D Curves from axial displacement test results http://www.iaeme.com/ IJMET/index.asp 1248 editor@iaeme.com

JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park 3.3. Angular Displacement Test of Overload Absorbing Gear Couplings Angular displacement testing was conducted on five specimens of the proposed overload absorbing gear couplings, as shown in Fig. 17, and the result was 112 KN. There was no deformation or abnormal behavior observed during the test. Figure 17 Images before and after the application of axial displacement: 1.5 Degrees were converted into 13.72mm SPL#1 (8.8mm @112.2kN) SPL#2 (8.5mm @112.2kN) SPL#3 (8.6mm @112kN) http://www.iaeme.com/ IJMET/index.asp 1249 editor@iaeme.com

Performance Evaluation of Overload Absorbing Gear Couplings SPL#4 (8.6mm @112.1kN) SPL#5 (8.6mm @112.3kN) Figure 18 F-D curves of angular displacement test results 3.4. Maximum Torque Test of Overload Absorbing Gear Couplings Maximum torque testing was conducted under the same axial and angular displacement conditions (where the displacement was set to zero) on five specimens of the proposed overload absorbing gear couplings, as shown in Fig. 19. The result was 122 KN. There was no deformation or abnormal behavior observed during the test. Figure 19 Experimental setup for maximum torque test SPL#1 (21.7mm @122.1kN) http://www.iaeme.com/ IJMET/index.asp 1250 editor@iaeme.com

JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park SPL#2 (17.1mm @122.1kN) SPL#3 (17mm @122.1kN) SPL#4 (17mm @122.2kN) SPL#5 (16.9mm @122.1kN) Figure 20 F-D curves of maximum torque test results 3.5. Sliding Torque Test of Overload Absorbing Gear Couplings Sliding torque testing was conducted under the same axial and angular displacement conditions (where the displacement was set to zero) on five specimens of the proposed overload absorbing gear couplings, as shown in Fig. 21, and it was confirmed that slip occurred when the torque ranged from 130 to 136 knm. http://www.iaeme.com/ IJMET/index.asp 1251 editor@iaeme.com

Performance Evaluation of Overload Absorbing Gear Couplings Figure 21Experimental setup for sliding torque test SPL#1 (23.2mm @135.5kN) SPL#2 (18.8mm @133kN) SPL#3 (18.7mm @130.5kN) http://www.iaeme.com/ IJMET/index.asp 1252 editor@iaeme.com

JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park SPL#4 (18.6mm @132.5kN) SPL#5 (19.3mm @133.5kN) Figure 22. F-D curves of sliding torque test results 3.6. Sliding Life Test of Overload Absorbing Gear Couplings The sliding life testing was conducted under the same experimental setup as the sliding torque test on two specimens of the proposed overload absorbing gear couplings,and up to 100 cycles for each specimen. The results are shown in Figs. 23 and 24, and it was confirmed that slip occurred for each specimen at torques between 60 to 80 knm. There was no deformation or abnormal behavior observed after the test. Figure 23. SPL#1 sliding life test (peak to peak signal) http://www.iaeme.com/ IJMET/index.asp 1253 editor@iaeme.com

Performance Evaluation of Overload Absorbing Gear Couplings Figure 24. SPL#2 sliding life test (peak to peak signal) 4. CONCLUSIONS The present study aimed to develop an overload absorbing gear coupling designed to minimize damage to its components, avoid suspension of operation and also prevent the generation of vibration and noise. To verify the design, fatigue analyses and performance tests were carried out, and the major findings are as follows. For the proposed overload absorbing gear couplings, accumulated damage was calculated based on the rated torque of 55.5 knm / 1,000,000 Cycles, i.e., the standard reference value for fatigue and durability testing. As a result, the accumulated damage was determined to be 0.507, less than 1.0, demonstrating that the given system can be considered safe. Fatigue testing was conducted under the same axial and angular displacement conditions (where the displacement was set to zero) on two specimens of the proposed overload absorbing gear couplings, and it was confirmed that these specimens did not exhibit any deformation or abnormal behavior, i.e., slip. Modal testing was carried out on the products developed in the present study, and it was concluded that no resonance was observed in these products, since the first natural frequency was determined to be 1,170 Hz, and the operation speed was 33.3Hz (2,000 rpm). To further confirm the reliability of the findings, various additional tests were conducted, including an axial displacement test, angular displacement test, maximum torque test, sliding torque test, and sliding life test. ACKNOWLEDGEMENT This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No.20183010025210). http://www.iaeme.com/ IJMET/index.asp 1254 editor@iaeme.com

JunWoo Bae, JongSigKwon, JinHoSeo, HyoungWoo Lee, KeunHyo Lee and Sookeun Park REFERENCES [1] J. Piotrowski, 1995, "Shaft Alignment Handbook", Marcel Dekker. New York, pp. 90~94. [2] P.C Renzo, 1968, "Gear Coupling", J. Eng. Indust., Trans. ASME, Vol. 90, No. 3, pp. 467~474. [3] J.R. Mancuso, 1986, "Coupling and Joints", Marcel Dekker. New York, pp. 234~318. [4] B.O Kim, C.G. Park and Y.C. Kim, 1999, "A Study on the Dynamic Characteristics of a Rotor System with a Misaligned Gear Coupling", Journal of Korea Society of Mechanical Engineers, Vol. A 23, No. 8, pp. 1399 ~1406. [5] D.L Dewell and L.D. Michell, 1984, "Detection of a misaligned disk coupling using spectrum analysis", Journal of Vibration, Acoustics, Stress, and Reliability in Design, Vol. 106, pp. 9 ~16. [6] M. Xu and R.D. Marangoni, 1991, "Flexible Couplings: study and application ", Shock and Vibration Digest, Vol. 22, No. 9, pp. 3 ~ 11. [7] Neale, M. Needham and R. Horrell, 1991, " Couplings and Shaft Alignment ", Mechanical Engineering Publications. http://www.iaeme.com/ IJMET/index.asp 1255 editor@iaeme.com