Papers by Keyword: Stick-Slip

Abstract: The uncertainty of mechanical system performance is strongly influenced by the properties of system components such as mass, stiffness-damping coefficient, and friction coefficient. Based on computational simulations, the system performance under uncertainty conditions can be estimated. However, the nonlinear dynamic behavior of friction is difficult to simulate in numerical simulations, this research is therefore employed a smooth stick-slip friction force model instead of the Coulomb friction force model. Monte Carlo simulation (MCS) combined with multibody dynamic (MBD) simulation is proposed to evaluate the uncertainty characteristics of the system components and stick-slip friction force between two contacting bodies. Numerical simulations applied the proposed method were performed to consider the effects of uncertainty of friction coefficient on the machining accuracy of a three axes CNC (Computer Numerical Control) machine tool.

Abstract: This paper examines the characteristics of stick-slip phenomena between the glass plate and Magneto-Rheological Elastomer (MRE) surface. Stick-slip phenomena are the spontaneous jerking motion that occurs while two objects are sliding over each other, usually accompanied by noise. Stick-slip is generated when it involves discontinuous frictional degradation when moving from static friction to dynamic friction. The phenomena can lead to uneven wear patterns, vibration and squeal noise which cause a shorter lifespan for the corresponding mechanical elements. MREs are kind of function materials to consist of a polymeric matrix with embedded ferromagnetic particles. Mechanical properties of the MREs can be controlled by the application of magnetic fields. The magnetic field-based controllability can be applied to the control of stick-slip phenomena. The friction experiment is conducted with the Reciprocating Friction Tester (RFT). The sliding speed of the RFT should be in low-speed conditions in order to make the stick-slips relatively easy to occur. A uniform magnetic field and a weight load are applied to the MRE sample to observe the effect of various experimental parameters on the movement of the stick-slip. In addition, frictional sounds due to the stick-slip phenomenon under different loads and magnetic field strength are measured and analyzed. The results of this experiment show that as the strength of the magnetic field increases, the difference in stiffness between the wipers-glass decreases, mitigating fricatives. The result is expected to be well applied to low-noise automotive wipers based on the controllability of friction behavior and squeal noise.

Abstract: A common problem in the petroleum drilling process is the torsional oscillation generated by the friction present during the cutting process. Torsional oscillations in drill string are particularly difficult to control because the drill string is an underactuated system, it has a very small diameter to length ratio and it is driven at top end with the cutting process at the other end. These factors make the drill string prone to self-excited torsional vibrations caused by the stick-slip of the cutting bit. The system is modeled as a torsional pendulum with two degrees of freedom, where the upper inertia models the top drive and also part of the drilling pipes. The bottom inertia models the bottom hole assembly (BHA). The drill is considered to be a massless torsional spring-damper. The drill string is subjected to friction, which is formulated using a dry friction model. The friction model takes into account Coulomb friction, stiction and Stribeck effect. The latter friction component is the main nonlinear phenomenon that introduces negative damping at the bit; it leads to self-enforcing stick-slip torsional oscillations.In the approach of this work, for the attenuation of these self-excited oscillations a recursive backstepping control strategy is used and it is carried out in continuous time. The main contribution of this work, which is different from the backstepping approaches reported in the literature, is to use a nonlinear/artificial damping as virtual control input. The stability of the system has been proven in the sense of Lyapunov. The goal of the proposed algorithm is to deal the underactuation of the system and to provide a good response for different operating points. The effectiveness and robustness of the controller has been tested in simulations.

Abstract: The use of high power railway vehicles requires enhanced control of wheel-rail adherence. When setting the train in motion, driving axles can exhibit torsional vibrations resulting in poor adherence and even axle damage. A significant number of railway authorities safety warnings and accident reports were issued related to the above phenomena. Adhesion saturation and negative slope are the characteristics which lead to self-sustained axial vibration. The aim of the present work is to prove the appropriateness of non-smooth models in the study of the axle torsional stick-slip vibrations which may occur when traction vehicles are set into motion. The model is simple, observes the main friction characteristics and provides the basis for efficient dynamics simulation. An experimental setup comprising a reduced scale wheel set is analyzed in order to validate the model proposed. The friction parameters are then identified using the proposed force-creepage relationship. Validation and verification is further carried out in frequency domain using both steady state and transient manoeuvres. Specific phenomena like discontinuities in the time-history friction force values occur. Validation and verification is carried out in frequency domain using both steady state and transient manoeuvres. From the comparison between the numerical and experimental results, it can be concluded that the setup is modeled accurately. Related problems may be solved using the present method, as it is pointed out in the article.

Abstract: This paper discusses the occurrence and non occurrence of low-frequency stick-slip motion on a simple caliper-slider experimental model. The analysis focused on the relationship between stiffness, i.e. contact stiffness and structure’s stiffness, and the generation of stick-slip motion. The occurrence of stick-slip motion is determined by analyzing the frequency characteristic of resulted vibration acceleration at the beginning of sliding which is resulted from a simultaneous application of force in tangential direction and slow release of force in normal direction. The results show that the occurrence and non occurrence of stick-slip motion can be classified into three regions according to the parameter of stiffness ratio, i.e. non occurrence region, mixed region, and occurrence region. The stiffness ratio S_r, the ratio of contact stiffness K_c to structure’s stiffness K_s, of 40 is found to be critical for the low-frequency stick-slip generation in this experimental model.

Abstract: The article deals with the problem of transition quasi-static contact in global slip under cyclic tangential load. The state of stress in partial contact, the laws of friction and scenarios of transition to slip of metal surface was determined. Partial slip is defined by the existence of stick and slip zones within the contact area. Currently, there are two basic concepts concerning surface damage processes: one connected with surface activation, which involves an increase in free energy in a tribological system, and the other connected with surface passivity, when free energy decreases. Experimental and theoretical studies were conducted to determine the contact between a sphere and a plane, which is the most suitable system for simulating small-amplitude fretting (~ 0–3 microns).

Abstract: This paper presents a numerical model to calculate wear during rolling contact due to micro-slip. Having as initial condition a corrugated rail it is shown the influence of the corrugation wavelength and the dynamic effects of the normal force on the wear creation. Experimental results are presented in order to reveal the influence of roughness when studying the stick-slip phenomenon.

Abstract: Micro-nanopositioning platform is a core component for micro-nanooperation. The static and dynamic characteristics of platform will determine its precision level. This paper presented a new 2-D micro-nanoplatform based on stick-slip driving. By using static structural module and modal analysis module of ANSYS software, the stress and natural frequency of pedestal were analyzed. The driving frequency of piezoelectric ceramic was selected far away from the natural frequency to avoid resonance. Dynamic performance of pedestal was also analyzed with ANSYS transient module. Simulation results show that the presented platform has excellent static and dynamic performance.

Abstract: In this paper, the relationship of the driving parameters and the movement of stick-slip driving was studied. Firstly, the research status and the principle of stick-slip driving was introduced. Secondly, the math model of the every step displacement and velocity of stick-slip driving was built. By using mathematical models, the relationship curve of the every step displacement and the step time was received through the simulation in Matlab software. Furthermore, in corroboration of the math model, the prototype was designed and the experiment system was built. From the testing of stick-slip prototype, the step displacement in every step time was tested 20 times and the relationship curve of the average every step displacement and step time was obtained. The simulation results are validated by the testing results and the method of reducing the time step to adjust the stick-slip driving step displacement and velocity were proved. In the future, a greater drive power should be researched for improving the movement performance of the stick-slip driving.

Abstract: Understanding the frictional behavior between glass and metals at elevated temperatures is necessary for accurate modeling and simulation of the precision glass molding (PGM) process, and can help in determining the required geometry of molds, inserts, and dies to produce various optical components. In this research, the frictional behavior of N-BK7, an oxide glass, at elevated temperatures in contact with plain steel has been studied. The results show two important phenomena related to temperature. First, the stick-slip phenomenon is more pronounced at higher temperatures close to the glass transition temperature. This is expected since relaxation and creep of glass occur by molecular diffusion, which becomes more rapid as temperature increases. Second, when the temperature is above the glass transition temperature and the glass begins to behave viscoelastically, the stick-slip friction behavior shows an exponential increase in friction force prior to the onset of sliding that is characterized by a jump in the position data on the order of several micrometers, and is consistent with the response of a viscoelastic material to applied load.