• Smart Structures and Systems
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• 제11권3호
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• pp.299-314
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• 2013

This paper presents a nonlinear time series analysis technique for evaluating machine defect severity, based on the Recurrence Plot (RP) entropy. The RP entropy is calculated from the probability distribution of the diagonal line length in the recurrence plot, which graphically depicts a system's dynamics and provides a global picture of the autocorrelation in a time series over all available time-scales. Results of experimental studies conducted on a spindle-bearing test bed have demonstrated that, as the working condition of the bearing deteriorates due to the initiation and/or progression of structural damages, the frequency information contained in the vibration signal becomes increasingly complex, leading to the increase of the RP entropy. As a result, RP entropy can serve as an effective indicator for defect severity assessment of rolling bearings.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.305-306
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• 2002

In this paper, the endurance life of the rolling bearings with defective balls and their failure (flaking) phenomena are presented. It was found that the lives of ball bearings with defective balls were shorter than that of calculated L10 life as well as that of normal bearings in spite of the using standard bearing components. Although the bearings were assembled with defective balls, whereas the other parts were qualified new ones, the main failures were occurred on the inner ring raceways. Moreover, the failures were on the center of the groove curvature and the severity of failure is similar to the order of initial defect depth of the balls. These shows that the defects on the bearings can affect the life of tribologically contacted mating parts.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1076-1077
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• 2007

CMS(Condition Monitoring System) is a useful tool to predict the defect of machine condition, for example, Motor, Bearing, Gear, Fan, etc. And, recently CMS is very important on plant. In this paper, describe the bearing electric arcing with example.

• 산업기술연구
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• 제35권
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• pp.3-8
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• 2015

A study has been made on defects which are formed in manufacturing processes of engine bearing and also on fatigue crack growth behavior in each step of bearing metal manufacturing. After the first step(sinter brass powder on steel plate ; Series A) many voids are made on brass surface and its size is decreased by the second step(rolling process of sintered plate ; Series B). After the third step(re-sintering step of brass powder and rolling ; Series C) the number of voids is decreased and its type shows line. The time of fatigue crack initiation and the growth rate of fatigue crack are in order of Series A, Series B, Series C. These reasons are that void fosters the crack initiation and growth, and residual stress made by rolling process effects on the crack growth rate in Series B, C. In forming and machining processes by use of final bearing metal, crack was observed at internal corner of flange and peeling off was observed at junction between steel and brass. Owing to the above crack and peeling off, it is considered that there is a possibility of fatigue fracture during the application time.

• Archives of Reconstructive Microsurgery
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• 제11권2호
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• pp.153-161
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• 2002

Purpose : Plantar surfaces, calcaneal area, and region of Achilles insertion, which are extremely related with weight-bearing area and shoes application, must be reconstructed with glabrous and strong fibrous skin. Numerous methods of reconstructing defects of these regions have been advocated, but the transfer of similar local tissue as a cutaneous flap with preservation of sensory potential would best serve the functional needs of the weight-bearing and non-weight-bearing surfaces of this region. Therefore it is recommended to use the limited skin of medial surface of foot that is similar to plantar region and non-weight-bearing area. In this paper we performed the medial plantar flap transfered as a fasciocutaneous island as one alterative for moderate-sized defects of the plantar forefoot, plantar heel, and area around the ankle in 25 cases and report the result, availability and problem of medial plantar flap. Materials and methods : We performed proximally based medial plantar flap in 22 cases and reverse flow island flap in 3 cases. Average age was $36.5(4{\sim}70)$ years and female was 3 cases. The causes of soft tissue defect were crushing injury on foot 4 cases, small bony exposure at lower leg 1 case, posterior heel defect with exposure of calcaneus 8 cases, severe sore at heel 2 cases, skin necrosis after trauma on posterior foot 4 cases, and defect on insertion area of Achilles tendon 6cases. Average follow up duration was 1.8(7 months-9.5 years) years. Results: Medial plantar flaps was successful in 22 patients. 18 patients preserved cutaneous branches of medial plantar nerve had sensation on transfered flap but diminished sensation or dysesthesia. At the follow up, we found there were no skin ulceration, recurrence of defect or skin breakdown in all 18 patients. But there was one case which occurred skin ulceration postoperatively among another 4 cases not contained medial plantar nerve. At the last follow up, all patients complained diminished sensation and paresthesia at medial plantar area distally to donor site, expecially with 4 patients having severe pain and discomfort during long-time walking. Conclusion : Medial plantar island flap based on medial plantar neurovascualr pedicle have low failure rate with strong fibrous skin and preserve sensibility of flap, so that it is useful method to reconstruct the skin and soft tissue defect of foot. But it should be emphasized that there are some complications such like pain and paresthesia by neuropraxia or injury of medial plantar nerve at more distal area than donor site. We may consider that medial plantar flap have limited flap size and small arc of rotation, and require skin graft closure of the donor defect and must chose this flap deliberately.

• Tribology and Lubricants
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• 제23권5호
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• pp.195-200
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• 2007

This paper presents the friction induced scuffing and wear defects analysis of a pin bushing bearing based on the chemical composition using a scanning microscopy (SEM) and an energy dispersive X-ray analyzer (EDX). The SEM/EDX system, which may provide good information on the surface thermal defects and chemical compositions, provides impurities such as an aluminum, a silicon, a ferrous component and an oxygen, especially. The EDX measured results show that the oxygen may reduce the strength and a hardness of a pin busing, which may lead to a scuffing and a seizure on the rubbing contact surface. The current technology fabricated by a sintering for a pin bushing bearing should be modified or changed to reduce the oxygen composition and the impurities in pin bushing materials.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.1021-1022
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• 2010

• Structural Engineering and Mechanics
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• 제91권1호
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• pp.49-61
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• 2024

In recent decades, the majority of studies have concentrated on the utilization of Steel Square Hollow Section (SHS) columns, with minimal attention given to reinforcing columns exhibiting inherent defects. This study addresses this gap by introducing initial vertical and horizontal defects at three distinct locations (top, middle, and bottom) and employing Carbon-FRP for reinforcement. The research investigates the dimensional and positional impacts of these defects on the axial behavior of SHS columns. A total of 29 samples, comprising 17 with defects, 11 strengthened, and 1 defect-free control, underwent examination. The study employed ABAQUS modeling and conducted experimental testing. Results revealed that defects located at different positions significantly diminished the load-bearing capacity and initial performance of the steel columns. Axial loading induced local buckling and lateral rupture, particularly at the defect side, in short columns. Notably, horizontal (across the column's width) and vertical (along the column's height) defects in the middle led to the most substantial reduction in strength and load-bearing capacity. The axial compressive failure increased with the length-to-width ratio of the defect. Moreover, the application of four carbon fiber layers to strengthen the steel columns resulted in increased Energy Dissipation and a delayed onset of local buckling in the face of axial ruptures.

• Tribology and Lubricants
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• 제33권4호
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• pp.141-147
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• 2017

The vibration data of bearings are very useful for monitoring and determining the condition of the bearings. The defect frequencies of ball bearings have been used for monitoring there condition. However, it is not easy to verify the defect frequencies as the wear progress. Therefore there is a need for an easy method to monitor the damages of bearings in real-time and to observe the variations in vibration characteristics as the wear progress. In this study, a bearing test equipment is constructed to diagnose the damage of bearings. The friction coefficient and vibration data are measured by using a torque sensor and an acceleration sensor, and the correlation between the measured data is analyzed to diagnose the condition of the bearing. We reached the following conclusions from the results. When the ball surface, inner and outer rings of a ball bearing are damaged, the friction coefficient increases to over 0.02 with an adhesion on the surface. Moreover this damage occurs more quickly with an increase in the number of revolutions. In the vibration characteristics, the amplitude of vibration wave appears high with an increase in the friction coefficient. In the high frequency range between 1000 and 2000 Hz, a wide range of frequency components with high amplitude occurs continuously irrespective of the number of revolutions.

• 대한기계학회논문집A
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• 제37권11호
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• pp.1315-1321
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• 2013

볼 베어링의 손상 상태를 예측하기 위한 방법을 본 논문에서 제시하였다. 손상 진전율을 추정하기 위해 확률적 베어링 피로 결함 진전 모델을 적용하고 잡음이 포함된 가속도 신호의 RMS 데이터를 이용하여 손상 상태와 고장 시간을 계산하였다. 확률적 결함 진전 모델의 파라미터는 볼 베어링에 대한 일련의 Run-to-Failure 시험을 수행하여 결정하였다. 가속도 RMS값으로부터 손상 진전율과 손상 상태를 추정하기 위해 규칙화된 파티클 필터 추정 방법을 적용하였다. 미래 시점에서의 손상 상태는 최근 측정된 데이터와 직전에 추정된 상태값을 이용하여 예측하였다. 예측된 손상 상태와 시험 데이터와 비교하여 개발된 방법의 적절성을 확인하였다.