Stick-slip algorithm in a tangential contact force model for multi-body system dynamics

차호영,Juhwan Choi,류한식,최진환 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.7

Contact force of Multi-body dynamics (MBD) system can be classified two parts. First is a normal force and the other is a tangential force called friction force. And the friction force can be represented by two states such as stick and slip. The stick-slip phenomenon is simply described as a simple contact model which is a rigid body contacted on a sloped surface. If the calculated friction coefficient between the body and sloped surface is less than the static friction coefficient, the body should be stuck. If the calculated friction coefficient is greater than the static friction coefficient, the body will be sliding along the surface. The phenomenon is called as stick and slip state of friction, respectively. Usually many researchers and commercial MBD software used a coulomb friction force model which is defined with an only function of relative velocity. This kind of friction force model will be called a conventional friction force model in this paper. A big problem of the conventional model can not describe a stick state of friction phenomenon. In the case of conventional friction force model, the body will be sliding even though friction state is stick. Because, the relative velocity must have a non-zero value in order to generate the friction force. To solve this kind of problem, we propose a stick-slip friction force model including a spring like force. In the case of stick-slip friction force model, the body can be stuck on the sloped surface because the friction force will be a non-zero value,even though the relative velocity approaches zero. We defined a relative displacement variable called stiction deformation. In this paper,the stick-slip friction model is proposed and applied in the contact algorithm of MBD system. And then two friction models are compared with numerical examples. With the proposed stick-slip friction model, more realistic results are achieved.

CMP에서의 스틱-슬립 마찰특성에 관한 연구

이현섭,박범영,서헌덕,박기현,정해도,Lee, Hyunseop,Park, Boumyoung,Seo, Heondeok,Park, Kihyun,Jeong, Haedo 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.4

Stick-slip friction is one of the material removal mechanisms in tribology. It occurs when the static friction force is larger than the dynamic friction force, and make the friction curve fluctuated. In the friction monitoring of chemical mechanical polishing(CMP), the friction force also vibrates just as stick-slip friction. In this paper, an attempt to show the similarity between stick-slip friction and the friction of CMP was conducted. The prepared hard pa(IC1000/Suba400 stacked/sup TM/) and soft pad(Suba400/sup TM/) were tested with SiO₂ slurry. The friction force was measured by piezoelectric sensor. According to this experiment, it was shown that as the head and table velocity became faster, the stick-slip time shortened because of the change of real contact area. And, the gradient of stick-slip period as a function of head and table speed in soft pad was more precipitous than that of hard one. From these results, it seems that the fluctuating friction force in CMP is stick-slip friction caused by viscoelastic behavior of the pad and the change of real contact area.

Tooth friction force and transmission error of spur gears due to sliding friction

박찬일 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3

This study investigated the tooth friction force and transmission error (TE) of spur gears due to sliding friction under quasi-static condition. The sliding velocity and friction force of spur gears and mesh compliance during meshing were calculated. The load–deformation relations between the tooth normal load, tooth errors, and mesh compliance, and moment equilibrium equation, including friction force, were derived. The friction force, tooth load, and TE of unmodified and linear tip-relief modified spur gears were analyzed by using the derived equations. Results indicated that the friction force, tooth load, and TE increased during approach and decreased in recess regardless of tooth modification, particularly in the single-mesh region. Friction caused larger peak-to-peak change of TE than that without friction. Xu’s friction coefficient generated smooth TE and tooth load transitions near the pitch point, and BK’s friction coefficient remained approximately constant, except for the sharp increase in tooth load and TE near the pitch point.

중·고등학생의 마찰력 개념 이해의 어려움 분석과 한 가지 지도전략의 제안

김영민,안민영 한국물리학회 2013 새물리 Vol.63 No.10

The concepts of the frictional force held by many Korean students are, `the frictional force on a static object is bigger than the external force, and `When a person walks, the direction of the frictional force on his/her foot is opposite the direction of his/her motion.' Almost all secondary science textbooks explain that the magnitude of the frictional force is proportional to normal force. The direction of the frictional force is generally explained in the textbooks as being `opposite the moving direction.' According to an investigation of science teachers' concepts on frictional force, some of them have non-scientific concepts such as `When a car is moving on a road under its own power, a frictional force is acting on the car in the opposite direction of its motion.' A teaching strategy based on the research results was developed by us and was applied to pre-service science teachers to decrease their misconceptions. 중고등학교 학생들이 마찰력에 대해 가지는 오개념 유형은,`정지해 있는 물체에 수평으로 힘을 가해 움직이지 않으면 가한 힘보다마찰력이 더 크다.', `사람이 걸을 때 발이 지면을 미는 방향과 반대방향이 아니라, 사람의 진행방향의 반대 방향으로 발에 마찰력이작용한다.'라고 생각하는 것 등이다. 그리고 중학교의 과학 교과서와고등학교 물리에서의 마찰력에 대한 설명을 보면 크기에 대한 설명에서는대부분 수직항력과 표면의 거칠기에 비례하는 것으로 설명하고 있으며,방향에 대한 설명은 일반적으로 `물체의 운동 반대 방향으로 지면과의마찰력이 작용한다.'라고 설명하고 있다. 그리고 중등학교 과학 교사들의상당수가 `사람이 걸을 때 사람의 진행 반대 방향으로 발에 마찰력이작용한다.'라고 생각하는 것으로 조사되었다. 본 연구에서는 예비 과학교사들을 대상으로 마찰 면에서의 물체의 상대운동을 강조한 수업 전략을사용하였을 때 마찰력에 대한 오개념을 줄일 수 있었고, 마찰력 개념에대한 이해를 높일 수 있었다.

Lateral force microscopy in low normal force limit

이현수,이내성,서용호 한국물리학회 2010 Current Applied Physics Vol.10 No.1

We have studied frictional force between SiN tip and Si surface by using lateral force microscopy. The cantilever we have used has very low stiffness of 0.006 N/m, and the normal force acting on the surface was much lower than the attractive force such as van der Waals force. In this low normal force limit, it was found that the frictional force did not depend on the normal force. We suggest a calibration method to estimate the attractive force from the lateral force data in this limit. The estimated attractive force between Si sample and SiN tip with radius of 10 nm was 0.4 nN in flat region and 0.65 nN at the corner of a rectangular hole.

Lateral force microscopy in low normal force limit

Lee, H.,Lee, N.,Seo, Y. Elsevier 2010 Current Applied Physics Vol.10 No.1

We have studied frictional force between SiN tip and Si surface by using lateral force microscopy. The cantilever we have used has very low stiffness of 0.006N/m, and the normal force acting on the surface was much lower than the attractive force such as van der Waals force. In this low normal force limit, it was found that the frictional force did not depend on the normal force. We suggest a calibration method to estimate the attractive force from the lateral force data in this limit. The estimated attractive force between Si sample and SiN tip with radius of 10nm was 0.4nN in flat region and 0.65nN at the corner of a rectangular hole.

마찰저항이 연속누출과 순간누출을 가지는 액체 풀의 확산에미치는 영향에 대한 해석적 연구

김태훈,최병일,김명배,도규형,한용식 한국수소및신에너지학회 2013 한국수소 및 신에너지학회논문집 Vol.24 No.6

In this study, solutions for a liquid pool spreading model with continuous and instantaneous release are discussed based on the model used in the FERC's report. The effects of the release time on the liquid pool volume and radius are investigated for the continuous release. For the continuous release with the frictional resistance force in the liquid pool spreading model, the vaporization time decreases as the release time increases. On the other hand, for the continuous release without the frictional resistance force in the liquid pool spreading model, the vaporization time increases as the release time increases. These phenomena are deeply related to the pool radius. In addition, the effects of the initial pool radius for the instantaneous release in the liquid pool spreading model are discussed. For the case with the frictional resistance force in the liquid pool spreading model, as reducing release time in the model with the frictional resistance force for the continuous release, the solution for a continuous release approaches to that for an instantaneous release. On the contrary to this, the pool volume and radius for the instantaneous release without the frictional resistance force are totally different from those for the continuous release without the frictional resistance force.

원격조작에 의한 작업대상물 강성과 마찰 특성의 동정

권혁조,전지명,김진옥,문일동,오재윤 전북대학교 공학연구원 ( 구 전북대학교 공업기술연구소 ) 2002 工學硏究 Vol.33 No.-

This study performs a workpiece stiffness and frictional characteristic identification experiments by teleoperation. Experiments are performed using a bilateral force feedback teleoperation system. It is composed of a master manipulator, the slave manipulator equipped with a force/torque sensor, and a real-time control system. To control the teleoperation system, a position-force controller is developed. The slave manipulator is controlled by the master manipulator's position command and the master manipulator is controlled by the force information from the slave manipulator. This study presents a method to find the slave manipulator's stiffness. And, this study presents a method to compute the workpiece stiffness based on the measured pressing force and deflection at the slave manipulator. Also, this study performs a workpiece frictional characteristic identification experiments. In the experiments, the slave manipulator rubs a workpiece with an arbitrary pressing force. While the slave manipulator rubs a workpiece, a vertical force and a frictional force are measured and the ratio of a frictional force to a vertical force is considered as a frictional characteristic.

MEASUREMENT OF THE DISC-PAD FRICTION COEFFICIENT FOR MECHANICAL BRAKES USING DIRECT AND INDIRECT METHODS

김영국,김석원,박찬경,박태원,김영모 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.1

It is necessary to guarantee the proper brake force to stop a train safely in a limited distance and o adjust its speed. Currently, most trains are run by electrical power and have a combined electrical and mechanical (friction) braking system. The mechanical brake force is determined by many parameters, such as the friction coefficient of the brake disc and pad, the pressure in the brake cylinder, the brake cylinder’s cross sectional area and the brake linkage ratio. In general, the friction coefficient data of the brake disc and pad have been taken through a dynamo-test in a laboratory, but these data might not be well matched with real data under operating conditions because of the difference in data acquisition conditions. The present study examined two methodologies that can measure the friction coefficient of the brake pad and disc based on a train’s real operating conditions. The first method was the direct method, which measured the brake force and clamping force applied on the mechanical brake by using strain gauges installed on the brake to calculate the friction coefficient. The second was an indirect method that obtained the friction coefficient by using the weight of the train and the equivalent brake force. Those variables were calculated from the longitudinal dynamic characteristics, such as resistance to motion, gradient resistance and curved resistance. These two methodologies were used to obtain the disc-pad friction coefficient for the mechanical brakes of a Korean high-speed train (HSR350x).

현장시험을 통한 기초 말뚝 부마찰력의 특성과 시공관리

홍석우 한국도로학회 2012 한국도로학회논문집 Vol.14 No.3

In this study the negative skin friction test of foundation pile was performed in order to monitor the negative skin frictional force acting on the steel pipe pile installed in soft soil. The monitored frictional stresses obtained from the long-term loading test. Through the long-term frictional stress monitoring test, the economical period for the construction of the superstructure was determined. The following conclusion were derived from this study: (1) In soft soil, negative skin friction increases with the increase in the rate of settlement. (2) In the friction relationship graph, the period where there is no frictional strain increase is verified and the time for the construction of the superstructure is determined. (3) The pile loading test was performed and the negative skin friction was compared with the test results. It was determined that the negative skin friction after driving was larger than the negative skin friction obtained from the loading test. 15 days after the construction, the monitored value was similar with the theoretical data. (4) It was determined that even during the occurrence of negative skin friction an economical construction management can be performed using the long-term monitoring method of negative skin friction. 본 연구에서는 교량기초 말뚝의 부주면마찰력 시험을 통하여 연약지반에 타설된 강관말뚝의 부주면마찰력을 측정하였으며장기적인 마찰응력의 관측시험을 통하여 경제적인 상부구조물 시공시기를 판단하였다. 본 연구의 결론은 다음과 같다. (1) 연약지반에서 부마착력의 크기는 침하속도가 클수록 크게 나타났다. (2) 마찰력의 관계 그래프에서 마찰응력의 증감이 없는 시기를확인하여 상부구조물 시공시기를 판단할 수 있었다. (3) 말뚝정재하시험결과와 부주면마찰력 시험결과를 비교해 본 결과 항타직후의 부주면마찰력은 재하시험 시의 마찰응력보다 크게 나오는 것으로 판단되며 15일 경과후의 측정값은 비슷하게 나오는것으로 판단되었고, 이론식에 의한 결과와도 비슷하였다. (4) 부주면마찰력의 장기관측기법을 사용하면 부주면마찰력이 발생하고 있는 중이라도 적절한 상부구조물의 시공시기를 파악할 수 있어 경제적인 시공관리가 가능한 것으로 판단된다.