• 한국기계가공학회지
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• 제21권2호
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• pp.64-72
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• 2022

Gear designers need to select the proper tolerances for deviations in both the center distance and parallelism of axes because these deviations cause high stresses and lead to fatigue breakage of the teeth. In this study, a three-dimensional finite element analysis model was developed for a helical gear used in metro vehicles, and a bending stress analysis method for gear pairs was established according to the contact position change. Using this model, the effect of shaft misalignment due to the center distance and shaft parallelism deviations on the bending stress of the gear was analyzed. As a result, the magnitude of the bending stress changed nearly linearly with the change in the center distance deviation. The tooth contact of the helical gear is biased toward the end of the tooth width when the parallelism deviations of the shaft occur, and the tooth root bending stress increases.

• 한국정밀공학회지
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• 제25권5호
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• pp.132-139
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• 2008

To meet demand of big capacity and high speed rotation for washing machine, more stress from bending and twisting are complexly loaded onto the shaft supporting the horizontal drum, causing problems in fracture strength and fatigue life. Also, Vibration occurs due to the frequency of the rotating parts. But, shaft has various design factors such as diameter and distance between bearings according to configuration of shaft, the optimal values can't be easily determined. Using a design of experiment (DOE) based on the FEM (Finite Element Method), which has several advantages such as less computing, high accuracy performance and usefulness, this study was performed investigating the interaction effect between the various design factor as well as the main effect of the each design factor under bending, twist and vibration and proposed optimum design using center composition method among response surface derived from regression equation of simulation-based DOE.

• 한국기계가공학회지
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• 제18권6호
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• pp.9-18
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• 2019

This study derives load characteristics and analyzes the safety of plowshares operating in dry fields. We mounted a three-blade, reversible plow on a 23.7 kW tractor and measured the plow's tractive force as well as the torque from the engine output shaft on the rear axle under various working speeds (L4, M1, M2, M3). We chose a Korean test site of Seomyeon, Chuncheon with sandy soil texture, as determined using the USDA method. We constructed the load spectrum for torque and tractive force using measured data and derived the fatigue life of the plowshare from a stress-cycle (S-N) curve of the plow material. Our results show that the M3 gear maximizes the driving shaft torque loads and, applying the tractive force load spectrum, creates a cumulative damage sum of $4.14{\times}10^{-5}$. Considering sampling time, we estimate a fatigue life of 805 hours while using the M3 gear. When using the other working speeds, however, all of the stress levels fell within the endurance limits and, therefore, our model predicts infinite plowshare lifetimes. For this analysis, we used a yield strength of 1,079 MPa for the plowshare and static safety factors, analyzed using the maximum stress, between 6.83 and 8.63 under each working speed.

• 한국소음진동공학회논문집
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• 제18권9호
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• pp.937-942
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• 2008

이 논문은 건설이 완료된 700MW급 발전소의 시운전 기간 중 주 급수펌프 임펠러에서 반복적으로 발생된 웨어링 이탈 및 고착, 슈라우드 손상 그리고 축 절단 등의 절손이 부분부하 조건에서 증폭되는 압력맥동과 연관이 있는 것으로 규명되었다.

• 대한기계학회논문집A
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• 제26권2호
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• pp.308-313
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• 2002

It is known that the composite material shafts using on small boats have various advantages comparing to forged steel shafts, fur examples, specific strength, fatigue strength, corrosion, etc. The analysis of the stresses and strains in the composite material shafts made by filament winding method is presented in this paper. The classical laminated plate theory is applied on the patch cut from the composite material hollow shafts. It is verified that the composite material hollow shafts of diameter 40 mm is the most optimum when the ratio of the inner diameter to the outer is 0.4 and winding angle is 45$^{\circ}$. It is also proven that the shear strain does not change seriously between 30$^{\circ}$and 60$^{\circ}$of winding angles. It is dangerous when the winding angle is over 75$^{\circ}$because the values of shear strain and stress produced on the shaft are too high so it must be avoided to wind the filament by the angle over 75$^{\circ}$.

• Composites Research
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• 제34권6호
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• pp.380-386
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• 2021

본 연구에서는 탄소섬유 강화 복합재료를 적용하여 PTO 샤프트의 임계 속도를 향상시키는 연구를 진행하였다. 탄소섬유 강화 복합재료의 경우 전단 강도가 낮은 단점이 있어, 이를 보완하기 위해 티타늄-탄소섬유 강화 복합재료 하이브리드 구조로 설계하는 것을 제안하였다. PTO 샤프트에서 요구하는 최대 허용 토크, 임계 속도, 비틀림 고유진동수 기준을 충족시키는 최적의 구조를 설계하고 제작하였다. 제작한 PTO 샤프트의 성능 평가를 위해 진동 시험, 정적 비틀림 시험, 비틀림 내구성 시험이 수행되었고, 진동 시험에서 PTO 샤프트의 임계 속도는 20570 rpm로 티타늄 샤프트 대비하여 7.5% 향상된 것을 확인하였다. 또한 정적 비틀림 시험을 통해 PTO 샤프트의 최대 허용 토크가 2300 N·m로 해당 기준을 충족시키는 것을 확인하였다. 최종적으로 11.3~113 N·m 범위의 하중을 반복하는 비틀림 내구성 시험에서도 10⁶ 사이클 동안 피로파괴가 발생하지 않는 것으로 평가되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.376-381
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• 2009

The increasing needs for higher cargo capacity in the container vessels' fleet has led to ship builder's demand for higher power output rating engine to meet the propulsion requirement, thus, leading to the development of super large two stroke low speed diesel engines. This large sized bore engines with more than 12 cylinders are capable of delivering power output up to more than 100,000 bhp at maximum continuous rating. The thrust variation force due to axial vibration occurring in propulsion shafting of these ships are transmitted to ship structure via thrust bearing. This force may vibrate the super structure of ship in the fore-aft direction and the fatigue strength of crank shaft can be decreased by additional bending stress increase in crank shaft pin and journal. In this paper, the axial vibration of propulsion shafting system on the 14RT-flex96C super large diesel engine with 14 cylinders is identified by theoretical analysis and vibration measurement.

• Tribology and Lubricants
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• 제24권6호
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• pp.297-301
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• 2008

In many dynamic seals such as lip seal and compression packings, it is well known that wear occur at the surface of heat treated steel shaft as results of the intervened wear particle. It is widely understood that the dominant wear mechanism related in sealing surfaces is abrasive wear. However, little analytical and experimental studies about this problems have been done until now. In this paper, a contact analysis is carried out using MARC to investigate the wear mechanism in contact seal applications considering elastomeric seal, a elastic perfect-plastic micro-spherical particle and steel surface. Deformed seal shapes, contact and von-Mises stress distributions for various particle sizes and interference are showed. The maximum von-Mises stress within steel shaft was exceeded its yield strength and plastic deformation occurred at steel surface. Therefore, the sealing surface can be also worn by sub-surface fatigue due to wear particles together with well known abrasion. The numerical methods and models used in this paper can be applied in design of dynamic sealing systems, and further intensive studies are required.

• 대한치과의사협회지
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• 제57권11호
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• pp.672-678
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• 2019

AIM: The purpose of this study was to evaluate and compare the torsional fracture resistances, cyclic fatigue resistance, and bending stiffness of two nickel-titanium (NiTi) rotary instruments made of different heat-treated alloy: Aurum Blue (heat-treated) and Aurum Pro (conventional). Methods: Forty-five Aurum Blue and Aurum Pro NiTi files were selected for the three mechanical tests (n=15). For the torsional resistance test, 3 mm file tip was fixed and the shaft was driven clockwise at 2 rpm until fracture occurred by using a customized device. Cyclic fatigue resistance was evaluated by rotating instruments in artificial canal with dynamic mode. Bending stiffness was tested by observation of the bending moment on attaining a 45° bend. The results were analyzed by student-t tests at a significance level of 95%. The fractured surface of each groups were examined under a scanning electron microscope (SEM). Results: Aurum Blue showed significantly higher toughness, ultimate strength, distortion angle, and number of cycles to failure than those of Aurum Pro (p < 0.05). However, Aurum Blue and Aurum Pro did not differ significantly in terms of bending stiffness. SEM showed typical topographic appearances of the cyclic fatigue and torsional fracture. Conclusions: Under the limitations of this study, heat-treated instruments showed higher flexibility and fracture resistances than conventional NiTi instruments.

• 한국자동차공학회논문집
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• 제13권5호
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• pp.127-133
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• 2005

Rotary swaging is one of the incremental forming process which is a chipless process using the reduction of cross-sections of bars, tubes and wires. The TDS(Tube Drive Shaft) of monobloc used in automotive has been developed by the rotary swaging process. The mechanical characteristics of swaged parts such as the hardness, thickness and roughness are also estimated to conduct experimental analyses of rotary swaging process with the materials of 34Mn5 Furthermore the change in the vibration mode of TDS due to design parameters, which are the tube length, diameter and thickness, has been investigated and analysed. The weight of the TDS product is smaller by about $12.8\%$ than that of SDS with the same performance. It could be evidently found that the TDS is designed to be much lighter than SDS (Solid Drive Shaft). This advantage might give some possibility to improve the NVH (Noise-Vibration-Harshness) characteristics. A maximum torque and a total number of torsional repetitions for the TDS is checked and measured to know the torsional intensity and fatigue strength through the static torsion test and torsional durability test, respectively. A total number of the torsional repetitions up to the fracture for the TDS is greater than 250,000 times.