by同音词表面光洁度表示符号（Surface finish is the symbol）Surface finish is the old standard of surface roughness; Their correspondence:
Surface finish level 14 = Ra 0.012
Surface finish level 13 = Ra 0.025
Surface finish level 12 = Ra 0.050
Surface finish level 11 = Ra 0.1
梦见吃地瓜Surface finish level 10 = Ra 0.2
Surface finish level 9 = Ra 0.4
Surface finish level 8 = Ra 0.8
Surface finish level 7 = Ra 1.6四国条约
Surface finish level 6 = Ra 3.2
Surface finish level 5 = Ra 6.3
Surface finish 4 = Ra 12.5
Surface finish level 3 = Ra 25
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Surface finish level 2 = Ra 50
qq在线状态Surface finish level 1 = Ra 100
Surface roughness units above is mu m, namely the micron = 10 ^ 6 meters.
Surface roughness refers to the small spacing of the machining surface and the unflatness of small peaks and valleys. The distance between the two peaks or the trough (the wave length) is small (below 1mm) and is indistinguishable from the naked eye, so it is a microscopic geometry error. The smaller the surface roughness, the smoother the surface. The size of surface roughness has a great effect on the performance of mechanical parts, mainly in the following aspects:
1) surface roughness affects wear resistance of parts. The rougher the surface, the smaller the effective contact area between the surface, the greater the pressure, the faster the wear.
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2) the surface roughness affects the stability of the matching property. The rougher the surface, the
more likely it is to wear out, increasing the gap in the working process. In the ca of overturning, the joint strength is reduced by squeezing the micro-convex peak and reducing the actual effective overgain.
3) the surface roughness affects the fatigue strength of the parts. The surface of rough parts has large trough, they are like sharp Angle gap and crack, they are nsitive to stress concentration, thus affecting the fatigue strength of the parts.
4) surface roughness affects the corrosion resistance of parts.
A rough surface that allows corrosive gas or fluids to penetrate into the metal inner layer through the surface of the microcove, causing surface corrosion.
5) surface roughness affects the aling of parts. The rough surface cannot be cloly attached, and the gas or liquid leaks through the cracks between the contacts.
Surface roughness affects the contact stiffness of the parts. The contact stiffness is the ability to resist contact deformation under external forces. The stiffness of the machine depends greatly on the contact stiffness between the parts.
7) influence the measurement accuracy of the parts. The surface roughness of the surface and measurement tools of the parts is directly affected by the accuracy of the measurement, especially in precision measurement.
In addition, the surface roughness of the parts plating coating, thermal conductivity and contact resistance, reflection and radiation performance, liquid and gas flow, the resistance of the conductor surface current flow will have varying degrees of impact.
2. The relevant evaluation is bad on baline 1, and the sampling length l is ud to determine the length of a reference line with the characteristic of surface roughness (e figure 4-1). The sampling length should be bad on the actual surface formation and texture characteristics of the parts, and the length of the length that can reflect the characteristics of测绘工程专业
surface roughness is lected.
The sampling length should be taken according to the general trend of the actual surface profile. FIG. 4-1 the sampling length and the evaluation length can be en from FIG. 4-1, the contour and shape error of the contour line are prent, and the height value of the sampling length not obtained at the same time is different. The rule and lection of sampling length is to limit and reduce the effe
ct of surface waviness on the measurement of surface roughness. The length of a length that Gp is required to asss the length of the outline, which may include one or veral sample lengths. Becau the surface of each part surface roughness is not necessarily very even, on a sampling length often cannot reasonably reflect the characteristics of a surface roughness, so need to take a few sample length on the surface to surface roughness, generally take 2, '= Slo (3) line To asss the surface roughness parameters for a given line, the surface roughness is
two-dimensional evaluation benchmark. Contour line has the following two kinds: (1) the line of least squares: has the geometry shape and contour line, divided into various points within the sampling length makes the contour line of contour offt for the minimum square sum of (e figure 4-2) o (2) the outline of arithmetic average line: has the geometry shape within the sampling length and the ba line of contour line. The contour of the line is divided by the line in the sample length, so that the area of the upper and lower sides is equal (e figure 4-3). F, ten F: + F3 +... 10 people = F,} + Fz '10... + only, '. Theoretically the least squares line is the only ideal baline, but in practice it is difficult to obtain, so generally substitute the arithmetic average line of contour,
and a position available approximate linear measurement. Figure 4-2 contour line of least squares figure 4-3 outline the arithmetic average of line 4 unimodal and Outlines of unimodal ChanGu contou
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r refers to the outline of the part between two adjacent contour low '(e figure 4-4). The outline of a single valley refers to the contour of the highest point between two adjacent contours (e figure 4-5). Single - peak and adjacent single - valley make up a microcosmic degree of unflatness. Outline of unimodal ChanGu figure 4-4 Outlines of unimodal figure 4-5 outline ChanGu 5. Outline of the peak and valley Profile peak is refers to the contour intercting line within the sampling length, between two adjacent interctions to out the outline of the part (e figure 4-6) o profile peak was part of the contour in the midline _ Bi. Contour valley refers to within the sampling length, contour line interction, a connection to the contours of the two adjacent interctions (e figure 4 to 7) <, contour valley was part of the outline below the center line, contour peak valley and contour formed within the sampling length this ction contour of micro roughness.
The surface roughness of the workpiece is the smaller the number and the smoother the surface
The unit of the number is um, and the following parameters can be ud to know that the surface of the smaller workpiece is smoother
There are three surface roughness parameters, namely, Ra Rz Ry
Ra is the arithmetic mean of the absolute value of the absolute
