Characterization On Wear Surface Topography Of Cylinder Liner Based On Fractal Theory

As the core power source of ships,modern transportation equipment and energy equipment,more attention has been paid to the internal combustion engines(ICEs)by the military,transportation,and energy power departments of various countries in the world.The internal combustion engine is developing towards high speed,high pressure,high efficiency and high service reliability,as the key component of the internal combustion engine,the tribological properties and surface topography of cylinder liner-piston ring are directly related to the operation performance and life of the internal combustion engine.This thesis focuses on the quantitative description and characterization on the field of view of the machine vision perception of the surface topography of the cylinder liner,the two-dimensional contour and the three-dimensional topography of the worn surface.The single-fractal and multi-fractal theories are used to analyze the changes of characteristic parameters and the relationship between surface topography and wear performance.The friction and wear characteristics of the piston rings-cylinder liner system of internal combustion engine power equipment are described,the nonlinear fractal theory is used to quantitatively characterize the characteristic changes of the cylinder liner-piston ring wear.The main works are as follows:(1)To obtain gray images by large field images based on machine vision perception,Harris corner detection algorithm is used to obtain image feature points,then an adaptive suppression extreme value method is used to filter the feature points,and the random sampling consensus algorithm is used to match the key points of the images and fuse the images.The feasibility of the large field of view splicing algorithm is validated by splicing the images.(2)On the basis of image fusion,the fractal dimension of the worn surface is analyzed,and the W-M fractal models of the two-dimensional contour and three-dimensional topography under different fractal parameters are established.Therefore,the relationships of topography complexity and the fractal dimension D and the characteristic scale coefficient G are obtained respectively.The results show that when the feature scale factor G is constant,the larger the fractal dimension D,the more complex of two-dimensional contour.When the fractal dimension D is constant,the larger the feature scale factor G,the larger of the surface contour,and the rougher of the surface contour.(3)Based on the UMT-2 friction and wear machine,the worn samples of the cylinder liner are obtained under different conditions,the two-dimensional contour and three-dimensional topography of the samples are acquired by using the three-dimensional confocal microscope.The structure function method and the power spectral density method are used to calculate the fractal dimension D of the two-dimensional contour and three-dimensional topography under different load and lubrication,and then the quantitative characterization can be implemented.The results show that the two-dimensional contour of the worn surface of the cylinder liner becomes smoother with the increase of the load,the roughness indexes of Ra changes irregularly,and the fractal dimension D continues to increase,D of the surface of the friction pair with the starvation lubrication is smaller than that in the stable wear test,and the surface of the friction pair is more rougher.(4)According to the two-dimensional contour and three-dimensional topography of cylinder liner samples under different wear conditions,the box dimension method is used to calculate the multifractal spectrum and parameters under different loads and the starvation lubrication,and then the worn surface topography and the corresponding height uniformity are described quantitatively.The results show that the width of the multifractal spectrum decreases with the increase of the load,and the fluctuation of the surface topography decreases,the surface gradually becomes smooth,and the spectrum width suddenly increases and the profile height changes greatly from anti-scuffing to scuffing of cylinder liner,which indicates that the surface is severely worn.