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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The table lists the roughness parameters by their symbol, name, corresponding 2D standard and unit. The Cross Hatch AngleSch is the found angle of a cross hatch pattern typically created in seen in cylinder liners and created by a honing process used to ensure proper lubrication. The Texture Direction IndexStdiis a measure of how dominant the dominating direction is, and is defined as the average amplitude sum divided by the amplitude sum of the dominating direction:. The radial spectrum is calculated by the following formula:.

In principle, the texture aspect ratio has a value between 0 and 1. For a Gaussian height distribution S bi approaches 0.

Smaller values indicate broader height distributions and visa versa for values greater than 3. Root Mean Square Gradient.

This parameter is only meaningful if there is a dominating direction on the sample. The Fractal Dimension, Sfd is calculated for the different angles by analyzing the Fourier amplitude spectrum; for different angles the amplitude Fourier profile is extracted and the logarithm of the frequency and amplitude coordinates calculated.

The Mean Half Wavelength, Shwis based on the asi radial spectrum:.

The angular spectrum is calculated by the following formula:. The amplitude sum, b ralong a semicircle with the radius, ris. For all surfaces S vi is between 0 and 0. The Core Roughness Depth, Skis the height difference between v46.1 intersection points of the found least mean square line. 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.

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

Large values of S ci indicate that the void volume in the core zone is large. Large anssi of S vi indicate large void volumes in the valley zone.

The hybrid parameters can be described graphically by the above figure. With this definition the Stdi value is always between 0 and 1.

We calculate Std from the Fourier spectrum. Surfaces with very dominant directions will have Stdi values close to zero and if the amplitude sum of all direction are similar, Stdi is close to 1.

Ansj, that since SPIP version 4. Note, also that roughness values depends strongly on measurement conditions especially scan range and sample density. The Ten Point Height, S10 zis defined as the ajsi height of the five highest local maximums plus the average height of the five lowest local minimums:.

The Mean Summit Curvature, S scis the average of the principal curvature of the local maximums on the surface, and is defined as:. 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.

### Roughness Parameters

Some of the parameters depend on the definition of a local minimum and a local maximum. All the parameters are based on two-dimensional standards that are extended to three dimensions.

B46.11 parameters are calculated based on this figure. If the surface is fractal the Log Log graph should be highly linear, with at negative slope.

## ANSI-ASME B46.1-1985.pdf

Having found r 0. The Density of SummitsSdsis the number of local maximums per area:. When there are less than five valid maximums or five valid minimums, the parameter is not defined.

The Surface Skewness, S skdescribes the asymmetry anxi the height distribution histogram, and is defined as:. Mean HeightS mean is the mathematical mean height of all pixels.

All six parameters are defined from the surface bearing area ratio curve shown asni the figures below.