ASME B / ANSI/ASME B – Surface Texture and Gaging for Screw Threads Package ASME B and ANSI/ASME B The ASME B46 1 ANSI ASME. Find the most up-to-date version of ANSI B at Engineering The American Standard for Surface Texture in ANSI B gives Ra as the standard surface finish designation. In most applications where RMS is called.

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All six parameters are defined from the surface bearing area ratio curve shown in the figures below. The line having the angle, awith the highest amplitude sum, Amaxis the dominating direction in the Fourier transformed image and is perpendicular to the texture direction on the image.

The calculated RMS roughness between cursors corresponds to the square b461. of the sum of all annsi in the 2D Power Spectrum Image between two concentric circles each with the radius of the inverse wavelength of the cursors in the IAPSD graph.

The Projected Area, S2Aexpresses the area of the flat x,y plane as given in the denominator of R The Radial WavelengthSrwis the dominating wavelength found in the radial spectrum. Dominant Radial Wave Length. The Core Roughness Depth, Skis the height difference between the intersection points of the found least mean square line.

For an anisotropic surface the correlation length is in the direction perpendicular to the surface lay. The first parameter is calculated directly from the image, while the remaining are based on the Fourier spectrum.

Here, a local minimum is defined as a pixel where all eight neighboring pixels are higher and a local maximum as a pixel where b46. eight neighboring pixels are lower.


The angular spectrum is calculated by the following formula:. The Mean Summit Curvature, S scis the average of the principal curvature of the local maximums on the surface, and is defined as:. Three parameters are calculated ansl on this figure. If there is a very dominating wavelength, Srwi is close to 0, and if there is no dominating wavelength, it is close to 1.


The radial spectrum is calculated by the following formula:. Root Mean Square Gradient. The Cross Hatch AngleSch is the found angle of a cross hatch pattern typically created in seen in cylinder liners h46.1 created by a honing process used to ensure proper lubrication.

The Ten Point Height, S10 zis defined as the average height of the five highest local maximums plus the average height of the five lowest local minimums:. The amplitude sum, b ralong a semicircle with the radius, ris.

ANSI-ASME B46.1-1985.pdf

The advantage of this is that deviations from the bearing plane can be quantified better when setting the bearing plane to zero see how this is done in the Plane Correction Dialog section.

The angle measured, is the angle difference between the two most dominant angles found in the image by analyzing its autocorrelation function. Surfaces with very dominant directions will have Stdi values close to zero and if the amplitude qnsi of all direction are similar, Stdi is close b46.1 1. The Fractal Dimension, Sfd is calculated b4.1 the different angles by analyzing the Fourier amplitude spectrum; for different angles the amplitude Fourier profile is extracted and the logarithm of the nasi and amplitude coordinates calculated.

Large S bi indicates a good bearing property. The Area Root Mean Square Slope, S dq6is similar to the Sdq but includes more neighbor pixels in the calculation of the slope for each pixel. All the parameters are based on two-dimensional standards that are extended to three dimensions. The spatial properties are described by five parameters.

The Surface Area, S3Aexpresses the area of the surface area taking the z height into account as given in the numerator of R There are three hybrid parameters. If the angle of the ridges is turned clockwise, the ansu is positive and if the angle of the ridges is turned anti-clockwise, the angle becomes negative. Large values of S ci indicate that the void volume in the core zone is large.


For a Gaussian height distribution S vi approaches 0.

If the surface is fractal the Log Log graph should be highly linear, with at negative slope. It is therefore important to include the measurement conditions when reporting roughness data. The amplitude sum, A aat a line with the angle, ais defined as:. Maximum Peak Height Sp: The result is called the angular spectrum. Parameters associated with the two-dimensional DIN standard are also calculated based on the bearing area ratio curve.

Each point in the graph corresponds to the normalized power in a circle one frequency pixel wide in the squared FFT image the Znsi Spectrum Image.

ASME B / ANSI/ASME B – Surface Texture and Gaging for Screw Threads Package

For a Gaussian height distribution S ci approaches 1. Note, that since SPIP version 4. Values numerically greater than 1. The Reduced Summit Height, Spkis the height of the upper left triangle.

The Mean Half Wavelength, Shwis based on the integrated radial spectrum:. The Texture Aspect Ratio Parameters, Str20 and Str37are 4b6.1 to identify texture strength uniformity of texture aspect. The surface bearing area ratio curve, which is also called the Abbott curve, is calculated by accumulation of the height distribution histogram and subsequent inversion.

Mean HeightS mean is the mathematical mean height of all pixels.

The Texture Direction b466.1, Stdis defined as the angle of the dominating texture in the image. As there are no pixels absi the borders of the image there are no local minimums or local maximums on the borders. For all surfaces S vi is between 0 and 0. Note, also that roughness values depends strongly on measurement conditions especially scan range and sample density.

The reported fractal dimension is the average for all directions.