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 radial spectrum is calculated by the following formula:. For all surfaces S vi is between 0 and 0. The first parameter is calculated directly from the image, while the remaining are based on the Fourier spectrum. For non-integer values of andthe value of F u pv q is found by linear interpolation between the values of F u pv q in the 2×2 neighboring pixels. For images consisting of parallel ridges, the texture direction is parallel to the direction of the ridges.
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.
Parameters associated with the two-dimensional DIN standard are also calculated based on the bearing area ratio curve. The Roughness Average, S ais defined as:. The Radial WavelengthSrwis the dominating wavelength found in the radial spectrum.
Each point in the graph corresponds to the normalized power in a circle one frequency pixel wide in the squared FFT image the Power B461.
Image. The result is called the angular spectrum.
ASME B / ANSI/ASME B – Surface Texture and Gaging for Screw Threads Package
Note, that since SPIP version 4. The Mean Half Wavelength, Shwis based on the integrated radial spectrum:. All the parameters are based on two-dimensional standards that are extended to three dimensions. Mean HeightS mean is the mathematical mean height of all pixels.
The line having the angle, awith the highest amplitude sum, Amaxis the dominating direction in wnsi Fourier transformed image and is perpendicular to the texture direction on the image. 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 fractal dimension, D, for each direction is then calculated as. For a Gaussian height distribution S bi approaches 0.
The angle measured, is the angle difference between the two most dominant angles found in the image by analyzing its autocorrelation function.
The Fractal Dimension, Sfd is calculated for the different angles by analyzing the Fourier amplitude spectrum; for b4.1 angles the amplitude Fourier profile is extracted and the logarithm of the frequency and amplitude coordinates calculated. Note,that negative peak artifacts may cause this parameter to be underestimated and in such cases it might be appropriate to perform some noise filtering. Large values of S ci indicate that the void volume in the core zone is large.
For all surfaces S ci is b466.1 0 and 0. The angular spectrum is calculated by the following formula:. The spatial properties are described by five parameters. Some of the parameters depend on the definition of a local minimum and a local maximum.
For a Gaussian height distribution S ci approaches 1.
Maximum Valley Depth Sv: The amplitude sum, b ralong a semicircle with the radius, ris. For a surface with a dominant lay, the parameters will tend towards 0.
The Reduced Summit Height, Spkis the height of the upper left triangle. The reported fractal dimension is the average for all directions. Values numerically greater than 1. For a Gaussian height distribution S vi approaches 0.
These parameters reflect slope gradients and their calculations are based on local z-slopes. The Mean Summit Curvature, S scis the average of the principal curvature of the local maximums on the surface, and is defined as:. For Gaussian height distributions S ku approaches 3.