• 제목/요약/키워드: wear and friction

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AC8A-T6 알루미늄 합금재의 절삭가공 특성에 관한 연구 (A Study on the Characteristics of Machining for AC8A-T6 Aluminum Alloy)

  • 최현민;김경우;김우순;김용환;김동현;채왕석
    • 한국공작기계학회:학술대회논문집
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    • 한국공작기계학회 2002년도 추계학술대회 논문집
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    • pp.192-197
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    • 2002
  • In this study, examined the cutting characteristics of alumuminum alloy AC8A-T6 that is used to present car piston materials. And in been holding materials machining empirically escape as result that experiment comparison changing the cutting speed and feed on various condition to choose efficient machining condition. The following results can be summarized from this research. 1. As the cutting speed decreased, principal cutting force and thrust cutting force is increased, and reason that cutting force interacts greatly in the low cutting speed is thought by result by BUE's stabilization. 2. The feed speed and cutting speed increase, friction factor is decrescent and the cause appeared the thrust cutting force is fallen than cutting force relatively because chip flow according to increase of the feed rate is constraint. 3. Though specific cutting resistance grows cutting area and the feed rate are few, the cause was expose that shear angle decreases by rake face of tool gets into negative angle remarkably as wear of a cutting tool or defect part of workpiece is cut. 4. Cutting speed do greatly depth of cut is slow, surface roughness examined closely through an experiment that becomes bad, and know that it can get good surface that process cutting speed because do feed rate by 0.1mm/rev low more than 250m/min to get good surface roughness can.

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염소가스 반응시간에 따른 TiC표면 탄소막의 Tribology 특성 (Dependence of $Cl_2$ Gas Reaction Time on Tribological Properties of TiC Derived Carbon Layer)

  • 임대순;배흥택;정지훈;나병철
    • Tribology and Lubricants
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    • 제25권1호
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    • pp.20-24
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    • 2009
  • TiC-derived carbon coatings have been synthesized at $600^{\circ}C$ temperature treatment with $H_2/Cl_2$ mixture gases. From Raman spectroscopy measurements, the modified layer was covered with carbon and the thick-ness of the layer was increased with increasing reaction time. And $I_D/I_G$ ratio was decreased with increasing reaction time. The superior tribological property was obtained from TiC reacted with $Cl_2$ gas for 2 hrs. And the tribological property measurements indicate that TiC-derived carbon layer has $0.9{\times}10_{-6}mm^3/Nm$ in wear coefficient and 0.13 in friction coefficient.

회전 핀의 종동 하중에 따른 박판 스프링의 대변형에 대한 연구 (A Study on the Large Deflection of Flat Spring Subjected to Follower Load by a Rotating Pin)

  • 정일섭
    • 대한기계학회논문집A
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    • 제28권9호
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    • pp.1352-1358
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    • 2004
  • The mechanical spring is one of widely used machine elements. Among various kinds, flat-type spring loaded by a rotating pin was studied. A flat spring was simplified to a cantilever beam, and numerical analysis was attempted. Since the loading pin rotates about a separate axis from the fixed spring or vice versa, the location, direction, and magnitude of the contact force including normal contact and friction loads vary accordingly. Meanwhile, the spring is deformed substantially as the relative motion progresses. Therefore, this problem needs to be formulated taking the follower loading characteristics and geometrical non-linearity into account. Derived nonlinear differential equation was solved to yield the spring deflection, contact force and the torque to rotate the pin, and the result was compared with a finite element solution. Also, the influences of principal design parameters were studied. The proposed methodology is expected to be useful for the design of pin-loaded flat spring and the prevention of mechanical failures in the form of yielding or fatigue failure of spring or severe wear of the components.

철도 차축재료의 프레팅 피로거동 평가 (Evaluation of Fretting Fatigue Behavior for Railway Axle Material)

  • 최성종;권종완
    • 한국자동차공학회논문집
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    • 제15권5호
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    • pp.139-145
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    • 2007
  • Fretting is a kind of surface damage mechanism observed in mechanically jointed components and structures. The initial crack under fretting damage occurs at lower stress amplitude and lower cycles of cyclic loading than that under plain fatigue condition. This can be observed in automobile and railway vehicle, fossil and nuclear power plant, aircraft etc. In the present study, railway axle material RSA1 used for evaluation of fretting fatigue life. Plain and fretting fatigue tests were carried out using rotary bending fatigue tester with proving ring and bridge type contact pad. Through these experiments, it is found that the fretting fatigue limit decreased about 37% compared to the plain fatigue limit. In fretting fatigue, the wear debris is observed on the contact surface, and oblique cracks at an earlier stage are initiated in contact area. These results can be used as useful data in a structural integrity evaluation of railway axle.

왕복동식 압축기 피스톤의 역학적 거동특성 (Dynamic Behavior Characteristics of Piston in Reciprocating Compressor)

  • 조인성
    • Tribology and Lubricants
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    • 제29권2호
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    • pp.105-110
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    • 2013
  • Refrigeration and air-conditioning compressors used in home appliances, including refrigerators and air conditioners, are typically hermetic-type reciprocating compressors. Because the shell is sealed by welding, it should be designed to have a semi-permanent life. The energy consumption of a hermetic-type reciprocating compressor is low, but because it operates continuously to maintain a constant temperature inside the refrigerator, it has a certain base load. In this type of compressor, the driving motor operates at a high speed (about 3,000 - 3,600 rpm), which causes valve damage, friction, wear, and high-frequency noise. Many studies have been conducted to solve these problems. To enhance the reliability and efficiency of the reciprocating compressor, the design conditions and operating environment of journal bearings should be considered. Dynamic behavior analysis should be carried out in terms of the discharge pressure. The results showed that the load (discharge pressure) increases in the forward lookup zone and decreases in the backward lookup zone. When the revolution speed is increased, the maximum load decreases in the region where the maximum load operates.

초전도자기베어링을 이용한 플라이휠 에너지 저장장치의 진동특성에 관한 연구 (A Study on Vibration Characteristics of Flywheel Energy Storage System Using Superconducting Magnetic Bearings)

  • 김종수;이수훈
    • 한국정밀공학회지
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    • 제15권2호
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    • pp.170-177
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    • 1998
  • The purpose of superconducting magnetic bearing flywheel energy storage system(SMB-FESS) is to store unused nighttime electricity as kinetic energy and convert it to electricity during daytime. The SMB-FESS is proposed as an efficient energy storage system because there is no mechanical problems, such as friction and wear The flywheel over SMB is rotated at a high speed, 50,000rpm. The major source of energy loss in the SMB-FESS is vibration of flywheel. Therefore, the vibration characteristics of SMB-FESS should be identified. In this study, the axial/radial stiffness and damping coefficient of SMB are measured by a vibration test. Natural frequencies and natural modes of flywheel and magnet are analyzed by a finite element method. The modal analysis of system is performed using the modal parameters of each component and the measured stiffness/damping coefficient. So, natural at frequencies and mode shapes of the joined system can be obtained. According to critical speed analysis, the system has two rigid conical modes in the low speed range. Nevertheless, the system has not been affected by the critical speed in the main operating range.

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내연기관 피스톤 링들 사이 가스압력 변동 (Variation of Inter-Ring Gas Pressure in Internal Combustion Engine)

  • 윤정의
    • 한국자동차공학회논문집
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    • 제3권6호
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    • pp.238-249
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    • 1995
  • The gas pressure acting on the rings in internal combustion engine influences the friction and wear characteristics. Inter-ring pressure variation during engine operation results from cylinder gas flow through a piston-ring pack. The flow passages consist of ring end gaps and clearances between the ring and the piston groove. The gas flow in the clearance between the ring and the groove is directly affected by the axial motion of the ring in the groove. In this paper the asperity contact force is newly considered in the prediction of the clearence between the ring and the groove surface. This term must be taken into account physically in case that the clearance get narrow rather than asperity height between the ring and the groove surface. Finally, comparisons of calculated inter-ring gas pressures based on the analytical method are made with the measured ones. The agereement was found to be good below midium engine speed, 3000rpm. In order to obtain accurate analytical results to the extend of high rpm range, it is recommended to include oil ring motion as well as top and second ring in analytical model.

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분말붕소법을 이용한 오스테나이트계 스테인리스 316L강의 기계적 특성 향상을 위한 연구 (Characteristics of Boronized 316L Austenitic Stainless Steel by Powder Boronizing)

  • 차병철;방현배;조형호;정우창
    • 한국표면공학회지
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    • 제44권2호
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    • pp.55-59
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    • 2011
  • In this study, the mechanical properties of boronized 316L austenitic stainless steel have been investigated. Boronizing was carried out in solid medium consisting of Ekabor powder at $900^{\circ}C$ and $1000^{\circ}C$ for 2, 4 and 8 hours, respectively. The properties of sample were analyzed by field emission scanning electron microscope, X-ray diffractometer, Glow discharge spectrometer, micro-hardness tester and ball-on-disk wear tester. Increasing the boronizing time and temperature, the hardness of boronized samples were shown over Hv 2000 and the thickness of boride layers were also increased linearly. XRD patterns of samples were revealed the presence of borides such as FeB, $Fe_2B$, CrB, $Cr_2B$ and $Ni_3B$. Friction coefficient of boronized STS 316L was shown the low value at $900^{\circ}C$ for 8 hours and $1000^{\circ}C$ for 4 hours, respectively.

Tribological performance of the laser surface treated CrZrSiN thin films

  • Kim, DongJun;La, JoungHyun;Lee, SangYul
    • 한국표면공학회:학술대회논문집
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    • 한국표면공학회 2012년도 춘계학술발표회 논문집
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    • pp.141-142
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    • 2012
  • Recently, surface texturing by atmospheric laser processing has been received lots of attention to improve the tribological performance of various surfaces and this laser texturing of surfaces could be considered in a large extent to improve tribological performance of PVD coated surface. Surface texturing could be performed by various manufacturing techniques such as indentation with hard materials, ion etching, abrasive jet machining, lithography, and Laser Surface Texturing (LST). Out of all these techniques, however it is generally accepted that laser surface texturing (LST) by atmospheric laser processing offers the most promising process as LST is very fast, environmentally-friendly, easy to control the shape and size of the microdimples. In this work various preliminary experimental results from the laser texturing on the PVD-coated steel substrate will be presented. Our results indicated that laser texturing definitely affect the tribological performance of the surfaces and the size as well as pattern type of laser texturing are one of the key factors. From the wear tests against an alumina counterpart ball at room temperature under oil-lubricated condition, laser surface texturing on the CrZrSiN films reduced the friction coefficients by approximately more than 5 times in the case of narrow patterned surfaces.

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니들 롤러 베어링의 피로 수명 향상에 대한 연구 (Improvement in Fatigue Life of Needle Roller Bearing)

  • 다리스렝 스르멩닥와;아마노프 아웨즈한;편영식
    • Tribology and Lubricants
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    • 제35권4호
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    • pp.237-243
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    • 2019
  • Through this study, we investigate the effects of ultrasonic nanocrystal surface modification (UNSM) technology on the fatigue life of needle roller bearings. The fatigue life of untreated and UNSM-treated needle roller bearings is evaluated using a roller fatigue tester at various contact stress levels under oil-lubricated conditions. We can ascertain that the fatigue life of an UNSM-treated needle roller bearing was extended by approximately 34.3% in comparison with an untreated one, where the effectiveness of UNSM technology diminishes with increasing contact stress. The surface roughness and surface hardness of needle roller bearings before and after being treated by UNSM technology are compared and discussed to understand the role of UNSM technology in improving the fatigue life of needle roller bearings. In addition, a fractograph of the damaged bearings is observed using a scanning electron microscopy to shed light on the fracture mechanisms of bearings under different contact stress levels. We can therefore conclude that the application of UNSM technology to the needle roller bearings improves the fatigue life by reducing the friction coefficient and increasing the wear resistance; this may be attributed to a reduction in surface roughness from 0.5 to $0.149{\mu}m$ and an increase in surface hardness from 58 to 62 HRc.