Occurrence Of Stick-slip Motion Research Articles

Tribological performance of novel nickel-based composite coatings with lubricant particles

The present study is focused on the evaluation of the tribological performance of novel Ni/hBN and Ni/WS2 composite coatings electrodeposited from an additive-free Watts bath with the assistance of ultrasound. Lubricated and non-lubricated scratch tests were performed on both novel composite coatings and on standard Ni deposits used as a benchmark coating to have an initial idea of the effect of the presence of particles within the Ni matrix. Under lubricated conditions, the performance of the Ni/hBN composite coating was very similar to the benchmark Ni coating, whereas the Ni/WS2 behaved quite differently, as the latter did not only show a lower coefficient of friction, but also prevented the occurrence of stick-slip motion that was clearly observed in the other coatings. Under non-lubricated conditions, whereas the tribological performance of the Ni/hBN composite coating was again very similar to that of the benchmark Ni coating, the Ni/WS2 composite coatings again showed a remarkable enhancement, as the incorporation of the WS2 particles into the Ni coating not only resulted in a lower coefficient of friction, but also in the prevention of coating failure.

Stiffness Effect on Low-Frequency Stick-Slip Motion Generated on a Simple Caliper-Slider Experimental Model

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 Sr, the ratio of contact stiffness Kc to structure’s stiffness Ks, of 40 is found to be critical for the low-frequency stick-slip generation in this experimental model.

Studies on Friction and Formation of Transfer Layer in HCP Metals

Surface texture plays an important role in the frictional behavior and transfer layer formation of contacting surfaces. In the present investigation, basic experiments were conducted using an inclined pin-on-plate sliding apparatus to better understand the role of surface texture on the coefficient of friction and the formation of a transfer layer. In the experiments, soft HCP materials such as pure Mg and pure Zn were used for the pins and a hardened 080 M40 steel was used for the plate. Two surface parameters of the steel plates—roughness and texture—were varied in tests that were conducted at a sliding speed of 2 mm/s in ambient conditions under both dry and lubricated conditions. The morphologies of the worn surfaces of the pins and the formation of the transfer layer on the counter surfaces were observed using a scanning electron microscope. In the experiments, the occurrence of stick-slip motion, the formation of a transfer layer, and the value of friction were recorded. With respect to the friction, both adhesion and plowing components were analyzed. Based on the experimental results, the effect of surface texture on the friction was attributed to differences in the amount of plowing. Both the plowing component of friction and the amplitude of stick-slip motion were determined to increase surface textures that promote plane strain conditions and decrease the textures that favor plane stress conditions.

Role of surface texture and roughness parameters in friction and transfer layer formation under dry and lubricated sliding conditions

Abstract Surface texture influences friction and transfer layer formation during sliding. In the present paper three well-defined surface textures, namely unidirectional, 8-ground, and random, were employed on steel plates. Experiments were conducted on a tribological couple – zinc pin against steel plate – using an inclined pin-on-plate sliding tester. It was observed that the occurrence of stick-slip motion, the transfer layer formation and the value of coefficient of friction as well as its two components, namely adhesion and plowing, depend primarily on surface texture. The effect of surface texture on coefficient of friction was attributed to the variation of the plowing component of friction for different surfaces. The plowing component of friction was highest for the surface texture that promotes plane strain conditions while it was lowest for the texture that favors plane stress conditions at the interface. Dimensionless quantifiable roughness parameters were formulated to describe the degree of plowing and hence the plane strain/stress type deformations taking place at the asperity level.

STICK-SLIP MOTION IN PNEUMATIC CYLINDERS DRIVEN BY METER-OUT CIRCUIT

Pneumatic cylinders may not achieve steady motion in applications where low velocities are required because of the stick-slip effect. However, an effective means to assess the possibility of stick-slip occurrence in pneumatic cylinders has not been reported. Despite friction force is an important parameter on stick-slip motion, there are only few studies on friction force at low velocities and stick-slip motion. In this paper, stick-slip motion in pneumatic cylinders is studied. Friction force is measured and stick-slip motion is simulated. The occurrence conditions of stick-slip are studied analytically using non-dimensional parameters. The inFLuence of each variable on the occurrence of stick-slip motion is clarified.