CN109186526B

CN109186526B - Surface roughness characterization method

Info

Publication number: CN109186526B
Application number: CN201810989389.5A
Authority: CN
Inventors: 张士军; 张胜豪
Original assignee: Shandong Jianzhu University
Current assignee: Shandong Jianzhu University
Priority date: 2018-08-28
Filing date: 2018-08-28
Publication date: 2020-09-25
Anticipated expiration: 2038-08-28
Also published as: CN109186526A

Abstract

The existing traditional surface roughness evaluation parameters such as Ra, Rq, Rz and the like cannot provide characteristic information of the regular shape of the surface. The invention provides a surface roughness characterization method, which can make up the defect that the traditional roughness characterization method cannot describe the uniformity of the microscopic unevenness of the surface of a workpiece. The technical scheme of the invention is that the mean value of the measured data in the height direction of the microscopic profile on the surface of the workpiece is calculated to distinguish the peak value and the valley value; setting a threshold value of the peak value, calculating the ratio of the mean value of all the measurement data larger than the threshold value to the mean value of the peak value, and judging the uniformity of the surface appearance of the workpiece according to the ratio, wherein the larger the ratio is, the more uneven the microscopic profile of the surface of the workpiece is; and calculating the maximum value and the minimum value in all the measurement data, solving the mean value of the absolute values of the maximum value and the minimum value, and further judging the uniform surface topography condition of the workpiece by using the ratio of the mean value to the mean value absolute value of all the measurement data.

Description

Surface roughness characterization method

Technical Field

The invention belongs to the technical field of machining, and particularly relates to a surface roughness characterization method.

Background

Parts to be mounted in mechanical devices, which are usually machined before assembly, are referred to as workpieces during machining, and the microscopic geometric features of the surfaces of the workpieces have a great influence on the wear resistance, sealing, fit, corrosion resistance, friction, heat conduction, adherence, and conductive lamp performance of the workpieces. Meanwhile, the microscopic geometric shape of the workpiece has close relation with the running stability, running precision, working reliability, vibration and noise of the whole equipment. Therefore, it is very important in mechanical equipment to be able to clearly describe the micro-geometric characteristics of the workpiece surface.

The micro-geometric characteristics of the workpiece surface are generally composed of three components, roughness, waviness and surface shape errors. Surface roughness is the most common parameter in machining that describes the micro-geometry of the machined surface, which reflects the micro-geometry characteristics of the fine texture of the surface of the mechanical part. Some machined surfaces have random microscopic geometries, while other machined surfaces have regular characteristics, but the conventional surface roughness evaluation parameters such as Ra, Rq, Rz and the like cannot provide characteristic information of surface regular shapes. Therefore, a need exists for a method that can better characterize the uniformity of the micro-asperities of the surface of the workpiece being processed, so as to more effectively characterize the micro-topography.

Disclosure of Invention

The purpose of the invention is: the method can make up the defect that the traditional roughness characterization mode cannot describe the uniformity of the microscopic unevenness of the surface of the workpiece.

In order to achieve the purpose, the technical scheme of the invention is as follows: calculating the mean value of the measurement data in the height direction of the microscopic profile on the surface of the workpiece; setting a threshold value of the peak value, calculating the ratio of the mean value of all the measurement data larger than the threshold value to the mean value of the peak value, and judging the uniformity of the surface appearance of the workpiece according to the ratio, wherein the larger the ratio is, the more uneven the microscopic profile of the surface of the workpiece is; calculating the maximum value and the minimum value in all the measurement data, calculating the mean value of the absolute values of the maximum value and the minimum value, and further judging the uniform surface topography of the workpiece by using the ratio of the mean value to the absolute value of the mean value of all the measurement data, wherein the operation method comprises the following steps:

1. measuring the surface of the processed workpiece by using a roughness measuring instrument to obtain N continuous measurement data a in the height direction of the microscopic profile in a sampling interval of the processed surface_iI =1, 2, 3, … …, N;

2. calculating the measurement data a_iAnd drawing an M mean line;

3. a greater than the mean value M_iCalled peak value, a smaller than mean value M_iCalled valley value, calculating peak value mean value Fmean;

4. calculating a threshold value Fy for the peak value, said threshold value Fy being equal to the peak mean value Fmean multiplied by a threshold coefficient Xf, i.e.: fy = Fmean Xf, the threshold coefficient Xf being greater than or equal to 1;

6. Calculating the distance Dfmax from the maximum peak point to the M mean line and the distance Dfmin from the minimum peak point to the M mean line;

7. calculating the distance Dgmax from the minimum valley point to the M mean line and the distance Dgmin from the maximum valley point to the M mean line;

8. calculating a maximum coefficient Sfg which is equal to the ratio of the sum of Dfmax and Dgmax to the sum of Dfmin and Dgmin, namely Sfg = (Dfmax + Dgmax)/(Dfmin + Dgmin);

9. and judging the uniformity of the micro-morphology of the surface of the workpiece according to the values of the relative coefficient Sf and the maximum coefficient Sfg, wherein the closer the value of Sf or Sfg is to 1, the more uniform the micro-geometry of the machined surface is, and the larger the value of Sf or Sfg is, the more non-uniform the micro-geometry of the machined surface is.

The invention has the advantages that: according to the invention, the relative coefficient and the maximum coefficient are obtained by calculating the peak value mean condition that the measurement data of the microscopic profile in the sampling length exceeds the peak value threshold value and the maximum value and minimum value conditions in all the measurement data, and the relative coefficient and the maximum coefficient can reflect the peak value distribution condition in the microscopic profile and can also reflect the size of the maximum measurement value and the minimum measurement value, so that the roughness of the microscopic profile on the surface of the workpiece can be described by using the method, and the uniformity degree of the microscopic profile can be accurately represented.

Drawings

FIG. 1 is a sample surface micro-topography of a machined workpiece A.

FIG. 2 is a sample surface micro-topography of workpiece A with the addition of a collinearity.

In the figure, 1, peak, 2, valley, 3, M mean line.

Detailed Description

The invention is described in further detail below with reference to the figures and specific embodiments.

The surface roughness characterization method comprises the following specific processes:

s1, measuring the surface of the processed workpiece A by using a roughness measuring instrument to obtain 31 continuous measurement data a in the height direction of the microscopic contour in the surface sampling interval of the processed workpiece A₁=20，a₂=5，a₃=30，a₄=5，a₅=15，a₆=3，a₇=30，a₈=5，a₉=25，a₁₀=5，a₁₁=30，a₁₂=3，a₁₃=20，a₁₄=5，a₁₅=20，a₁₆=2，a₁₇=28，a₁₈=5，a₁₉=20，a₂₀=10，a₂₁=20，a₂₂=5，a₂₃=20，a₂₄=5，a₂₅=30，a₂₆=5，a₂₇=20，a₂₈=5，a₂₉=20，a₃₀=5，a₃₁=25；

S2, calculating the measurement data a_iM =14.39 and draws a line of the M means, as in fig. 2;

s3, a > mean M =14.39_iCalled peak, a less than mean M =14.39_iCalled valley, the peak mean Fmean =23.31 is calculated;

s4, calculating a threshold Fy for the peak value, the threshold Fy being equal to the peak mean value Fmean multiplied by a threshold coefficient Xf, the threshold Xf being taken to be 1.2, then Fy =23.31 x 1.2= 27.97;

s5, calculating a relative coefficient Sf, wherein Sf is equal to all the a larger than Fy_iAbsolute value | a of the mean of_imeanThe ratio of | =29.6 to the absolute value of the peak mean | Fmean | =23.31, i.e. Sf =29.6/23.31= 1.27;

s6, calculating distance Dfmax =30-14.39=15.61 from the maximum peak point to the M-means line, and distance Dfmin =15-14.39=0.61 from the minimum peak point to the M-means line;

s7, calculating the distance Dgmax =14.39-2=12.39 from the minimum valley point to the M-means line, and the distance Dgmin =14.39-5=9.39 from the maximum valley point to the M-means line;

s8, calculating a maximum coefficient Sfg, where Sfg is equal to the ratio of the sum of Dfmax and Dgmax to the sum of Dfmin and Dgmin, i.e., Sfg = (Dfmax + Dgmax)/(Dfmin + Dgmin) = (15.61 + 12.30)/(0.61 + 9.39) = 2.79;

and S9, judging the uniformity of the micro-topography of the workpiece surface according to the values of the relative coefficient Sf and the maximum coefficient Sfg, wherein the values of Sf =1.27 and Sfg =2.79 are both greater than 1, which indicates that the micro-topography of the processed surface A is in an uneven state.

It should also be noted that the above example is only one specific embodiment of the present invention. It is obvious that the invention is not limited solely to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the invention should be considered as within the scope of the invention.

Claims

1. A surface roughness characterization method is characterized by comprising the following steps:

step 1, measuring the surface of a machined workpiece by using a roughness measuring instrument to obtain N continuous measurement data a in the height direction of a microscopic contour in a machined surface sampling interval_iI =1, 2, 3, … …, N;

step 2, calculating the measurement data a_iAnd drawing an M mean line;

step 3, a is larger than the average value M_iCalled peak value, a smaller than mean value M_iCalled valley value, calculating peak value mean value Fmean;

step 4, calculating a threshold Fy of the peak value, wherein the threshold Fy is equal to the peak value mean value Fmean multiplied by a threshold coefficient Xf, namely: fy = Fmean Xf, the threshold coefficient Xf being greater than or equal to 1;

Step 6, calculating the distance Dfmax from the maximum peak point to the M mean line and the distance Dfmin from the minimum peak point to the M mean line;

step 7, calculating the distance Dgmax from the minimum valley point to the M mean line and the distance Dgmin from the maximum valley point to the M mean line;

step 8, calculating a maximum coefficient Sfg which is equal to the ratio of the sum of Dfmax and Dgmax to the sum of Dfmin and Dgmin, namely Sfg = (Dfmax + Dgmax)/(Dfmin + Dgmin);

and 9, judging the uniformity of the micro-morphology of the surface of the workpiece according to the values of the relative coefficient Sf and the maximum coefficient Sfg, wherein the closer the value of Sf or Sfg is to 1, the more uniform the micro-geometry of the processed surface is, and the larger the value of Sf or Sfg is, the more non-uniform the micro-geometry of the processed surface is.