面接触润滑油膜测量系统滑块倾角的快速计算

A Robust Approach to Determining the Slider Inclination in a Slider-on-Disc Conformal-contact Lubricating Film Measurement System

在面接触润滑油膜厚度的光干涉测量中,需要确定滑块和玻璃盘所形成的微小倾角.一般通过目测干涉条纹的数量计算倾角,效率低且误差大.根据滑块表面干涉条纹等距,光强呈周期性变化的特点,对滑块面的干涉光强曲线进行傅里叶变换,综合采用Rife-Jane和重叠FFT相位差法进行频率插值,较好地消除了频谱泄漏,较准确计算干涉条纹数量,从而得到滑块与玻璃盘间的倾角.试验证明:当条纹数量大于5时该方法的测量相对误差在1%以下,具有很强的抗干扰能力.对不同倾角下的油膜厚度进行了测量,得出了润滑油膜的无量纲承载量-滑块收敛比曲线.结果表明:膜厚较高时,无量纲载荷最大值出现在收敛比为1.2左右的位置,但当膜厚较低时,无量纲载荷最大值出现在收敛比大于2的位置,偏离了经典理论.

In the interferometry measurement of lubricating film thickness in a slider-on-glass disc contact, inclination angle of the slider with respect to the disc has to be determined. Usually, the number of fringes is counted artificially to deduce the inclination angles, which is inefficient and leads to large errors. Fringes generated by the slider-on-glass disc contact are of equal distance and the interference intensity varies periodically with film thickness. Therefore, a Fouriertransform-based approach has been proposed to accurately calculate the fringe number, in which a frequency interpolation is used to eliminate frequency leaking by combining the Rife-Jane method and overlapping FFT phase difference method. Experiments show that the relative error of the proposed approach is less than 1% when the fringe number larger than 5. Strong reliability is demonstrated. The film thickness at different inclination angles was measured, and dimensionless capacity vs. convergence ratio was obtained. The results revealed that when the film thickness is high, the maximum load-carrying capacity appears around a convergence ratio of 1.2, which is correlated well to the classical theory. However, when the film thickness gets low, the maximum load-carrying capacity reaches its maximum when the convergence ratio is larger than 2, showing obvious deviation from existing theory.