• 구강회복응용과학지
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• 제25권4호
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• pp.391-401
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• 2009

임플란트의 성공은 식립 후의 초기 안정성 (Initial stability)의 결과가 중요한 영향을 준다. 이 연구의 목적은 연질 골에서 두 종류의 테이퍼 형태 임플란트가 임플란트의 디자인과 self-tapping blade의 유무에 따라서 초기 안정성에 주는 영향을 알아보는 것이다. Self-tapping blade를 가지고 있는 것과 가지고 있지 않은 두 종류의 테이퍼 형태 임플란트가 사용되었다. Solid Rigid Polyurethane Form으로 연질 골 상태인 D4 골 모형을 재현하였다. 임플란트 고정체를 식립하면서 초기 안정성 값을 기록하고, 식립 직후 implant stability quotient (ISQ)을 측정하여 Resonance frequency Analysis (RFA)를 평가하였다. 마지막으로 임플란트가 식립된 모형골을 만능 시험기에 부착하여 장축 방향으로의 pull-out force를 측정하였다. 초기 안정성 값과 최대 pull-out torque 값은 non self-tapping implants가 self-tapping group에 비하여 통계학적으로 유의하게 큰 평균값을 나타냈다 (P = 0.008). 공진 주파수 분석 결과인 ISQ 값은 거의 비슷한 평균값을 보였으면 통계학적으로 차이가 없었다. 각 임플란트 시스템에서 식립 토크와 pull-out 최대 토크 그리고 공진 주파수 간에는 상관관계를 나타내지 않았다. Non self-tapping 임플란트의 높은 식립 토크는 임상적으로 우수한 초기 안정성을 의미한다. 결론적으로 연질 골에서 self-tapping blade가 없는 임플란트가 있는 것 보다 더 우수한 초기 안정성을 보였다.

• Composites Research
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• 제17권1호
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• pp.1-9
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• 2004

본 연구에서는 타격음을 이용한 비파괴 검사법을 제안하였다. 제안된 방법(tapping sound analysis)은 건강한 구조물과 손상된 구조물의 타격음의 차이를 분석하여 구조물의 손상 유무를 판단하는 방법이다. 타격음의 직접적인 비교는 비효율적이므로 타격음으로부터 특성을 추출하기 위해 wavelet packet transform에 기반한 특성추출법을 제안하였다. 또한 추출된 특성 자료를 바탕으로 손상의 유무를 판단하는 지표로서 특성 지수를 정의하였다. 제안된 방법의 타당성을 밝히기 위해 실험적인 검증을 수행하였다. 복합재료를 이용하여 건강한 구조물과 손상된 구조물을 제작하고 타격음을 측정하였다. 제안된 손상 판단 기법을 이용한 결과로부터 특성 지수에 의한 손상 판단의 타당성을 밝혔다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.538-541
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• 2005

In tapping mode atomic force microscopy(TM-AFM). the vibro-contact response of a resonating tip is used to measure the nanoscale topology and other properties of a sample surface. However, the nonlinear tip-surface interact ions can affect the tip response and destabilize the tapping mode control. Especially it is difficult to obtain a good scanned image of high adhesion surfaces such as polymers and biomoleculars using conventional tapping mode control. In this study, theoretical and experimental investigations are made on the nonlinear dynamics and control of TM-AFM. To analyze the complex dynamics and control of the tapping tip, the classical contact models are adopted due to the surface adhesion. Also we report the surface adhesion is an additional important parameter to determine the control stability of TM-AFM. In addition, we prove that it is more adequate to use Johnson-Kendall-Roberts (JKR) contact model to obtain a reasonable tapping response in AFM for the soft and high adhesion samples.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.660-663
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• 1996

There has been many activity to increase accuracy in machining center by reducing tracking error. The tracking error can cause bad effect in high speed rigid tapping in which syncronization servo motor with spindle is relatively important. To reduce tracking error, feed forward control has been used, but no method is provided knowing motor dynamics, force variation, etc. In this paper, we observe that, despite of tracking error of relevant axis, high speed tapping could be possible by reducing contour error of axis to be syncronized. We present the method to increase accuracy in high speed tapping to minimize contour error by automatically fitting gains of servo and spindle.

• 한국기계가공학회지
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• 제11권3호
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• pp.29-34
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• 2012

This paper reports some experimental results in high speed rigid tapping of magnesium alloy(AZ91D). M3 spiral tap and high speed spindle tapping center of gantry type were used in experiments and thrust forces were measured. The experimental results indicate that the thrust forces are proportional to the spindle speed and depth of cut. The thrust forces increase as the depth of cut increases. M3 Tapping was achieved at the spindle speed of 10,000rpm, depth of cut of 1.5D and total stroke of 32mm.

• 한국정밀공학회지
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• 제17권11호
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• pp.55-62
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• 2000

The poor machinability material such as austenite stainless steel(STS304) is emphasized on the wide use of HSSE for the tapping operation. The difficulty can be entirely to tapping torque due to chip formation through the hole of tap. The object of this study is to investigate tap geometry affecting the tapping torque from a practical point of view. The study shows that the optima tapping torque is affected by the tap geometry and cutting condition for STS304.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.184-187
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• 2000

This paper describes action of synchronous error between z axis and spindle axis on rigid tapping. Because rigid tapping cuts the threads synchronizing the movement of z axis to spindle rotation, synchronous error between z axis and spindle is very important. Increase of synchronous error degrades the accuracy of thread and crushes the tap in worst case. So we developed the realtime measurement system of synchronous error in order to know the action of synchronous error on rigid tapping. In result, we have known that synchronous error was increased according to rise of spindle speed and z axis speed. And because the cutting torque(M3-30Ncm∼M10-300Ncm) on rigid tapping are less than maximum motor torque(3500Ncm), it specially doesn't affect the synchronous error. The most important parameter which has affected the increase of synchronous error was acceleration/deceleration time. On worst case, spindle motor was tripped because of the excess of synchronous error. Because the acceleration/deceleration time ocuupies the most of the total cutting time, in order to move on the high speed rigid tapping, the acceleration/deceleration time of spindle must be remarkably reduced.

• 한국정밀공학회지
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• 제18권11호
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• pp.67-73
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• 2001

This paper aims at developing a torque model for the high-speed tapping with small-diameter taps. As recent industries such as automobile and information technology grows, taps smaller than 5mm in diameter are needed much more. In that occasion, the friction force between a tap surface and a workpiece plays much more important role in the tapping torque than in he larger tapping. Tapping mechanism was analysed based on the tap geometry. It has two steps : one is a forward cutting composed of the chamfered threading and full threading and the other is the backward cutting. The torque by the cutting force in the chamfered threading is calculated using the cutting area and the specific cutting force while the torque by the friction force, which is rather dominant than the cutting force both in the full threading and in the backward cutting, is calculated using the normal force on the threads and the friction coefficient. The experiment has shown that the results by the proposed torque model fit quite well with the acutal measurements within the error of 10%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.304-307
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• 2002

High speed machining was accomplished. through the technological advances which covers the whole field of mechanical industry. But tapping have many troubles because of its complicate cutting mechanism, for example. tool damage, chip elimination and synchronization between spindle rotation and feed motion. But High speed tapping is so important that it marches in step with the flow of the times and make improvement in the productivity. In this paper we analyze mechanism of high speed synchronized tapping with the signal of tapping torque and spindle speed obtained through the newly developed high speed tapping machine(NTT-30B). We made an experiment with this machine on condition of various speed from 1000rpm to 10000rpm. As one complete thread is performed through the whole chamfer cutting, cutting torque increases highly in chamfer cutting, but smoothly in full thread cutting functioning of the threads guide. And the size of cutting torque according to spindle speed(rpm) was not enough of a difference to be conspicuous.

• 한국안전학회지
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• 제25권2호
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• pp.1-6
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• 2010

Flow characteristics of differential pressure flow meters which have a shape of triangular separate bar (TSB) was investigated according to the machining conditions in pressure tapping holes. Diameter of the pressure taping holes is either 1.0 mm or 1.5 mm. Also, number of the pressure tapping holes are drilled either 9 or 17. The mass flow rate of the TSB flow meters are calibrated with a laminar flow meter by connecting them in line. The mass flow rate in the TSB flow meters are plotted with a non-dimensional parameter H which includes the gas temperature, exhaust gas pressure and differential pressure at the flow meters. An empirical correlation between the mass flow rate at the TSB flow meter and the non-dimensional parameter H was obtained. The empirical correlation showed highly linear relationship between the mass flow rate and the non-dimensional parameter H. The hole size of the pressure tapping holes has a bigger effect on the flow rate than the number of the tapping holes.