An analytical model of the contact vibration of sliders was developed in order to determine the optimum specifications for minimizing the fluctuations of flying height. In this model, the motion of the slider is expressed with two degree-of-freedom in the translation and pitching directions. The air film and suspension are modeled as a two-degree-of-freedom mass-damper-spring vibration system; the contact force between the slider and the disk is modeled by integrating the contact area when the slider is in contact with the media at a certain pitching angle. The degree of interference when the slider is in contact with the media is modeled in terms of the interference height. The developed analytical model shows that the contact vibration of the slider has a divergent mode or a convergent mode depending on the magnitude of the coefficient of friction. These numerical results agree with our qualitative measurements of vibration.

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This paper describes a nonlinear vibration analysis of angular contact ball bearing of a rigid rotor considering waviness of ball and races. Five degrees of freedom dynamic model of the rotor-bearing system has been analyzed using Runge?Kutta algorithm and MATLAB software. Comparisons of peak amplitudes of the vibrations due to different defects are presented for the lubricated condition of the bearing. Based on the computed results, it has been observed that in the presence of lubricant film at the contacts of balls and races, vibrations reduce significantly. However, large amplitudes of waviness and increase in spindle mass enhance the vibrations.

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Addition of excess antishudder additive to transmission oil results in a decrease of the friction coefficient to a level below which the transmission torque capacity becomes unsatisfactory. However, very low concentrations of antishudder additive can result in unsatisfactory antishudder performance and durability. To obtain the optimal balance between antishudder performance and torque capacity, a specific alkenylsuccinimide has been developed. The relationship between the antishudder performance and torque capacity was investigated by performing a series of low-velocity friction apparatus (LVFA) rig tests as well as statistical analysis using the quantitative structure-property relationship (QSPR) method that related the structure and physical properties of the molecule to the measured frictional properties.

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Diamond-like carbon (DLC) is used as a superior material in various fields because of its several excellent properties, such as high hardness, low friction coefficient and so on. DLC coating has good lubricity without lubricant, but it could show better lubricity by using lubricant. Therefore, we investigated an effect of the oiliness agent on the friction properties of the DLC coating. The friction tests were carried out by using a reciprocating ball-on-disk wear tester. Lubricant is composed of 10 mass% oiliness agent and 90mass% hydrocarbon oil. The friction coefficient of the DLC coating was decreased by using lubricant. And the oiliness agents were classified into three groups by friction properties. Glycerin monooleate (GMO) showed the lowest friction coefficient of all oiliness agents at all temperatures in this experiment. It was considered that GMO was adsorbed on the DLC surface stronger than the other oiliness agents. It was estimated that alcohol part in ester effects on adsorption of these oiliness agents.

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Diamond-like carbon (DLC) is being advanced as an excellent surface modification technology for a growing number of applications because of its low friction coefficient and excellent wear resistance. Due to the excellent characteristics of certain mechanical elements, such as a bearing, high levels of functionality are expected. Unfortunately, it is difficult to take full advantage of such high functionality because of insufficient endurance under high-pressure operating conditions. In order to make use of DLC as a bearing surface coating, the mechanism of DLC delamination under high-pressure conditions needs to be clarified. This paper discusses the mechanism of delamination of the intermediate layer of a DLC coating on a bearing in a test rig and by numerical simulation using FEM analysis. Test results revealed that the smaller the Young's modulus value of the intermediate layer (a factor affecting durability) of the DLC coating, the greater the resistance to delamination.

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This paper presents the effect of load carrying (position and weight of load) on the maximum peak values of traction coefficient between shoe sole and floor during walking on level walkway. Gait experiments were conducted by five healthy male adult participants walking on the force plates with carrying the loads. Each subject was tested at step length of 0.75 m and at walking speed of 1.4 m/s. They were instructed to carry the loads by three different ways; a 2-handed load carrying, a back-pack load carrying, and a waist level front load carrying. Weight of load was 49, 98, 147 or 196 N for each way of load carrying. For a waist level front load carrying, the maximum peak traction coefficient at heel strike period |F_h/F_n|_h statistically significantly (p < 0.01) decreased with increasing of weight of load. On the other hand for other ways of load carrying, |F_h/F_n|_h was not affected significantly (p > 0.05) by weight of load. For each way of load carrying, the maximum peak value of traction coefficient at toe-off period |F_h/F_n|_t had tendency to increase with increase of weight of load. The relationship between the slip potential and the COM position change by load carrying were also discussed.

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