磨合是各运动副在投入运行前为获得好的配合性、提高承载能力所必须经历的过程，表面形貌的明显变化是磨合过程中表现出的重要特征。本文引入分形理论，用分形参数表征磨合表面的形貌变化。研究表明，磨合表面变化的分形参数表征是简单有效的。

The fractal dimension and scale coefficient of surface profiles were calculated using the structure function method. Studies show that fractal dimension or scale coefficient is not optimum in characterizing rough surfaces. In consideration of this case, a fractal parameter called the characteristic roughness is put forward by combining the profile fractal dimension and the scale coefficient. Its definition and calculation expression are given. Running-in wear tests were conducted by using a thrustwasher type tester, and surface topographies were measured in the same area of the test specimens at different wear times. Experimental results show that the characteristic roughness parameter is not only more objective but also more sensitive to characterize wear surfaces during the running-in process than fractal dimension or scale coefficient.

To find a more accurate method characterizing wear particles, fractal geometry is applied in this paper describing wear particle accumulation. The wear experiments are carried out on a pin-on-disc test rig under dry friction conditions for a copper alloy pin and a steel disk. The results demonstrate that the logarithm of wear particle accumulation shows good linearity with the logarithm of the measured particle size. The relation between the accumulation of wear particles and the particle size presents a strong bi-fractal behavior. In addition, it is discovered that the fractal dimension of wear particle accumulation changes in different wear stages. The changes of the transition points of the bi-fractals correspond to the wear state variations.

Fractal geometry is applied to the characterization of rough surfaces. The variation law of surface topography during running-in period is studied with scale-independent fractal parameters. The theoretical relation of real contact area between rough surfaces to profile fractal parameters, material properties and load, etc. is obtained. Using the relation and Rowe’s modified adhesion theory, a fractal model of running-in wear is developed. Theoretical analysis and experimental researches show that the result calculated by this wear models are consistent with the experiments. q1999 Elsevier Science S.A. All rights reserved.

Taking the chock shield supports as the object of study, methods for measuring and calculating the external load of powered supports were discussed. Selecting the angle parameters as variables, the simple formulae of interactive computation with respect to the work angles of a powered support were deduced and verified by an example. Furthermore, the formulae determining the magnitude, direction and action point of the external load were put forward. The investigation results have provided a sound basis for the software design of the intelligent instrument for load measuring of powered supports.