• 한국철도학회논문집
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• 제10권5호
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• pp.546-553
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• 2007

본 연구는 압입축에 프레팅이 발생할 경우 프레팅 마모에 의한 접촉형상의 변화가 접촉응력의 분포, 균열발생 위치에 미치는 영향을 분석하고자 하였다. 압입축의 프레팅 피로실험시 측정한 접촉면의 프로파일을 이용하여 유한요소 해석을 수행하고 피로 사이클별 마모형상 변화에 따른 접촉면의 응력 변화를 분석하였다. 접촉면의 응력 해석결과를 이용하여 프레팅 피로손상 파라미터와 다축 피로이론를 적용하여 마모에 따른 균열발생위치의 변화를 해석하고 실험과 비교, 분석하였다. 프레팅 마모에 의해 접촉 끝단의 응력집중은 초기에 급격하게 감소하며, 마모가 진행될수록 응력집중의 위치는 접촉끝단에서 안쪽으로 이동한다. 따라서 프레팅 마모에 의한 접촉응력의 변화가 균열발생 위치의 변차와 다중균열발생의 주요원인임을 명확히 하였다.

• 한국기계가공학회지
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• 제14권3호
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• pp.85-91
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• 2015

The press-fit shaft is an important part used in automobiles, vessels, and trains. This study proposes an optimized design method to reduce damage that may occur in the press-fitted shaft by modifying the shape of the boss step of the press-fitted shaft. To reduce the time and cost of running the optimized design method, an approximate design optimization is applied and an optimized algorithm is generated using a genetic algorithm that is widely used in engineering fields and an approximate model using a response surface method. The planned experiments for the data that are needed to generate the approximate model use a central composite design (CCD) and Latin hypercube sampling (LHS), and the results of the approximate optimization using the above two design of experiments are to be compared.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.648-652
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• 1994

Lower Arm은 전차축식 현가장치에 사용되는 자동차부품으로 바퀴에서 발생되는 제동력이나 코너링력 등을 지탱하는 장치이다. V형의 상하 2개의 서스펜션암의 축에 의해 츠레임에 장착되고 좌우에 있는 Lower Arm끝부분은 볼조인트 및 부싱에 의해 스티어링 너클에 부착된다. 압입부품들은 자동차의 주행중 발생하는 외력에 의하여 이탈될 수 있는 위험성에 항상 노출되어 있어 자동차에 사용하는 압입부품들의 이탈력은 매우 중요하지만 한번 이탈시킨 Lower Arm은 이탈력이 현저히 저하되기 때문에 이탈력 측정에 의한 품질관리는 전량검사가 불가능하게 된다. 본 연구는 Lower Arm에 압입되는 볼조인트의 압입력을 압입거리에 따라 측정하여 Lower Arm에 뚫어진 볼조인트 압입구멍의 크기와 압입력의 상관관계를 실험적으로 구할수 있는 크기와 압입력의 상관관계를 실험적으로 구할 수 있는 모니터링 시스템을 개발하고자 한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.1097-1098
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• 2009

• 한국정밀공학회지
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• 제33권7호
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• pp.559-564
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• 2016

The objectives of this paper are to develop a finite element analysis model to analyze press-fitted and bending load conditions in a press-fitted assembly, and propose a hub shape optimization method to minimize contact pressure near the shaft contact edge. Numerical asymmetric-axisymmetric finite element models have been developed to predict contact stress on press-fitted shafts. The global optimization method, genetic algorithm, local optimization method, and sequential quadratic programming were applied to a press-fitted assembly to optimize the hub contact edge geometry. The results showed that the maximum contact pressure with the optimized hub shape decreased more than 60 % compared to conventional hubs and the maximum contact stress affecting fatigue life was reduced about 47 %. Hub shape optimization can be useful to increase the load capability of press fits in terms of wear and fatigue behavior.

• 대한기계학회논문집A
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• 제33권10호
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• pp.1091-1098
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• 2009

In this paper, the procedure to estimate fatigue crack initiation life has been established by considering fretting wear and multiaxial stress states on the contact surface of press-fitted shafts. And a method to calculate the local friction coefficient during the running-in period of fretting wear process has been proposed. The predicted result of worn surface profile in the press-fitted shaft with non-linear local friction coefficient can avoid excessive wear depth estimation compared with that for the case of constant local friction coefficient. Furthermore, the predicted fatigue crack initiation lives based on Smith-Watson-Topper model considering the fretting wear are in good agreement with the experimental data. Consequently, the present method is valid not only for predicting worn surface profile, but also for assessing fatigue crack initiation lives considering the fretting wear during the running-in period in press fits.

• 대한기계학회논문집A
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• 제32권1호
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• pp.54-62
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• 2008

In this paper the fretting wear of press-fitted specimens subjected to a cyclic bending load was simulated using finite element analysis and numerical method. The amount of microslip and contact variable at press-fitted and bending load condition in a press-fitted shaft was analysed by applying finite element method. With the finite element analysis result, a numerical approach was applied to predict fretting wear based on modified Archard's equation and updating the change of contact pressure caused by local wear with influence function method. The predicted wear profiles of press-fitted specimens at the contact edge were compared with the experimental results obtained by rotating bending fatigue tests. It is shown that the depth of fretting wear by repeated slip between shaft and boss reaches the maximum value at the contact edge. The initial surface profile is continuously changed by the wear at the contact edge, and then the corresponding contact variables are redistributed. The work establishes a basis for numerical simulation of fretting wear on press fits.

• 대한기계학회논문집A
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• 제31권6호
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• pp.701-709
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• 2007

To clarify the characteristics of surface damage due to fretting in press-fitted shaft, experimental methods were applied to small scale specimen with different bending load condition. Fatigue tests and interrupted fatigue tests of press-fitted specimen were carried out by rotate bending fatigue test. Macroscopic and microscopic characteristics were examined using scanning electron microscope (SEM), optical microscope or profilometer. It is found that small fatigue cracks are nucleated early in life regardless of bending stress, and thus the most portion of fatigue life on press fits can be considered to be crack propagation process. Most of surface cracks are initiated near the contact edge, and multiple cracks are nucleated and interconnected. Furthermore, the fretting wear rates at the contact edge are increased rapidly at the initial stage of total fatigue life. It is thus suggested that the fatigue crack nucleation and propagation process is strongly related to the evolution of surface profile by fretting wear in press fits.

• 한국기계가공학회지
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• 제20권5호
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• pp.128-134
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• 2021

A press-fitted shaft is an essential part used in industrial machines, and it is generally used to transmit large quantities of power. Very high contact pressure occurs at the end parts of the contact between the shaft and boss, which are press-fitted shaft components. Such contact pressure not only damages the contact surface of a press-fitted shaft but also reduces its fatigue strength. To improve a press-fitted shaft's fatigue strength, the contact pressure on the contact surface, which directly affects the fatigue strength, should be minimized. Thus, in this study, the design configuration optimization of the end part of the boss was based on the approximate optimization method and was aimed at minimizing the contact pressure at the end of a press-fitted shaft. Comparison of the contact pressure and the contact stress of a conventional press-fitted shaft with those of the optimized press-fitted shaft showed that the boss design of the optimized press-fitted shaft effectively improved the fatigue life.

• 비파괴검사학회지
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• 제33권2호
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• pp.129-137
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• 2013

나노압입시험기의 힘교정과 압입자에 대한 3차원 형상 관찰 및 분석이 본 연구에서 진행되었다. 표준분동으로 교정한 마이크로밸런스로 나노압입시험기에서 발생시킨 하중을 측정하여 측정치와 발생치의 비로 압입하중을 교정하였고, 나노압입시험의 시작점인 초기 접촉 하중도 확인할 수 있었다. 삼각뿔 압입자를 원자현미경으로 관찰하여 분석한 결과 비교적 사용이력이 없는 압입자 A와 마모된 압입자 B의 첨단곡률반경은 각각 $19.71{\pm}3.03$ nm와 $1043.94{\pm}50.91$ nm로 결정되었다. 완벽한 삼각뿔 압입자 형상과 중첩하여 압입자 A와 B의 첨단무딘깊이(bluntness depth)를 1.22 nm와 64.56 nm로 결정하였고, 용해실리카 기준시편에 수행한 나노압입시험 결과를 살펴본 결과 두 압입자의 압입하중-변위곡선들이 무딘깊이 차이만큼 수평축으로 서로 어긋나 있음을 확인할 수 있었다. 수평 이동을 통해 보정된 압입곡선의 분석을 통해 개별 압입자 면적함수에 대한 고려없이 1.11 % 이내에서 동일한 용해실리카의 나노경도를 결정할 수 있었다.