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위너 필터와 충격 펄스 카운팅을 이용한 저속 기계용 구름 베어링의 결함 검출
박성택(Park, Sung-Taek),원종일(Weon, Jong-Il),박성범(Park, Sung Bum),우흥식(Woo, Heung-Sik) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.12
The low speed machinery faults are usually caused by the bearing failure of the rolling elements. As the life time of the bearing is limited, the condition monitoring of bearing is very important to maintain the continuous operation without failures. A few monitoring techniques using time domain, frequency domain and fuzzy neural network vibration analysis are introduced to detect and diagnose the faults of the low speed machinery. This paper presents a method of fault detection for the rolling element bearing in the low speed machinery using the Wiener filtering and shock pulse counting techniques. Wiener filter is used for noise cancellation and it clearly makes the shock pulse emerge from the time signal with the high level of noise. The shock pulse counting is used to determine the various faults obviously from the shock signal with transient pulses not related with the bearing fault. Machine fault simulator is used for the experimental measurement in order to verify this technique is the powerful tool for the low speed machine compared with the frequency analysis. The test results show that the method proposed is very effective parameter even for the signal with high contaminated noise, speed variation and very low energy. The presented method shows the optimal tool for the condition monitoring purpose to detect the various bearing fault with high accuracy.
슬리브드 폴리머 발사체의 충격시 벌징 거동 패턴에 미치는 코어 재료의 영향
박성택(Sung-Taek Park),정윤철(Yoon-Chul Jung),신형섭(Hyung-Seop Shin) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
In the present study, the deformation behavior of both of metal and polymer combination on impact was investigated. They have showed a different deformation behavior when the co-axially combined projectile was impacted on rigid target. The theory according to Taylor's simplified approach assumes an ideally rigid-plastic material model exhibiting rate-independent behavior and simple one-dimensional wave propagation concepts that neglect radial inertia. In the case of impact with polymeric materials, elastic strain in general are not negligible compared with plastic strain; and the rigid-plastic material behavior assumed by Taylor for metallic materials cannot be applied any more. Since, the sleeve and the core materials have widely different mechanical properties, they will produce a significant difference of mechanical impedance with each other. Therefore these impedance mismatch influences on the deformation behavior sleeved polymer projectile on impact. As a result, sleeved projectiles will generate a very interesting impact behavior. Therefore, the according to sleeved metal material and core polymer material can see expected. The objective of this study was to investigate the factors which influences on deformation behavior pattern of sleeve materials surface.
박성택(Sung-Taek Park),신형섭(Hyung-Seop Shin),박정수(Jung-Soo Park),최준홍(Joon-Hong Choi),김정태(Jeong-Tae Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
The deformation of polymers under high loading-rate conditions will be a governing factor to be considered in their impact-resistant applications such as protective shields and transparent armor. In this paper, the deformation and fracture behaviors of polymeric materials such as PE, PC and PEEK have been investigated by Taylor Impact tests. Taylor cylinder impact tests and high speed photography are introduced to examine the deformation behavior under dynamic loading condition. 20 ㎜ air gun was used to perform the impact experiments. Cylindrical projectiles have been impacted onto a hardened steel anvil at a velocity ranging from 100 to 350 ㎳?¹. Along the barrel line, a photo-sensor which measures the speed of the projectile, four digital cameras which has shutter speed of 1/917,000sec and a rigid anvil were set up. After impact experiments, the shapes of projectiles and images taken using high speed cameras were analysed. Depending on materials adopted, they showed a variety in deformation and fracture behaviors.
Taylor Impact Test시 고속 카메라 영상을 사용한 폴리머 재료의 동적 거동 해석
박성택(Sung-Taek Park),박정수(Jung-Soo Park),신형섭(Hyung-Seop Shin),최준홍(Joon-Hong Choi),김정태(Jeong-Tae Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
To evaluate dynamic material properties of metallic materials at high-strain-rate. several one-dimensional models using recovered projectiles by Taylor Impact tests have been developed. However, for polymeric materials, the models can not be used as developed because polymers show significant elastic and anelastic deformation. This limitation could be released by incorporating the high-speed photography technique with Taylor impact tests in the range of impact velocity from 150 to 350 m/s. A series of photographs made it possible to depict the deformation pattern and to measure instantaneous diameter along the projectile length. In addition, it gave a relationship between the deformation length and the elapsed time which make possible to calculate a strain rate at an instant of deformation. The strain rate dependance of the dynamic yield stress in thermoplastic materials of PE, PC and PEEK can be determined by rod impact test in the strain-rate range of 10³~10⁴ sec?¹.
박성택(Sung-Taek Park),임경훈(Kyung-Hoon Lim),김시조(See-Jo Kim),신형섭(Hyung-Seop Shin) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The objective of this work was to investigate the lateral deformation behavior at impact surface in sleeved polymers during Taylor impact. This test setup has been generally used to determine the dynamic yield stress of cylinder projectile. However, the impact behavior of sleeved projectile is very complex as compared with the one of cylinder projectile. Therefore, this study investigated experimentally the influence of sleeve material and thickness on them. Taylor impact tests of sleeved projectiles were carried out in the velocity range between 100~300 m/s velocity. High-speed photography provided a series of images representing the deformation behavior of projectiles during impact. Experimental data were compared with the data obtained by using the AUTODYN 3D-simulation. The numerical simulation results showed similar behaviors to those obtained by experiments. Through the numerical simulation it to predict the behavior at higher impact velocity. Also, it was possible to understand the dynamic behavior of inner core and outer jacket materials induced during the impact through the comparison of experimental and numerical data.