Measuring and testing – Hardness – By penetrator or indentor
Patent
1995-08-21
1999-11-30
Raevis, Robert
Measuring and testing
Hardness
By penetrator or indentor
G01N 348
Patent
active
059922249
DESCRIPTION:
BRIEF SUMMARY
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a computer automated and controlled method for determining the deformability of the surface of a test specimen. The invention consists of firstly scanning three times along a chosen line on the specimen's surface with a suitable stylus; once with the stylus lightly loaded giving the original surface texture, once with the stylus loaded giving the deformed surface profile and then again with the stylus lightly loaded giving the new surface texture, and secondly calculating the two differences in the resulting deformation depths between the first and third scans and between the second and third scans. The former difference gives the permanent deformation remaining after the loaded scan, the latter difference gives the elastic deformation partly recovered after the loaded scan. Knowing the stylus' scan load and geometry, the invention offers not only significant advances in continuous hardness testing but also yields information relating to the mechanical scratch and wear properties of material surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates the first scan, from left to right, of the test specimen's (1) surface texture (3) with the lightly loaded stylus (2).
FIG. 2 illustrates the second scan, from left to right, of the test specimen (1) with a load (4) on the stylus (2) producing the deformed surface profile(5).
FIG. 3 illustrates the third scan, from left to right, of the test specimen (1) again with the lightly loaded stylus (2) giving the new surface profile (6) partly recovered from the deformed surface profile (5).
FIGS. 4 and 5 illustrate the graphic representation of the elastic (7) and permanent (8) parts of the deformation calculated by forming the differences between profiles (6) and (5) and between profiles (3) and (6) respectively.
DESCRIPTION AND BACKGROUND OF THE INVENTION
The invention concerns a method for determining the deformability of the surface of a test specimen. Firstly, by scanning along a line on the surface with a lightly loaded stylus, the surface texture of the specimen is measured. Secondly, the same line is traversed with the now loaded stylus such that the surface of the specimen is penetrated. Finally, the same line is traversed again with the lightly loaded stylus to record the new surface texture.
Different methods are known with which the hardness and other mechanical properties, i.e. Young's modulus, near the surface of the test specimen are determined.
A closely related method is described in DE-G.M. 71 40 841: Here, the surface of the test specimen is firstly scanned with a lightly loaded stylus to record its texture. After the same line has been traversed with a loaded indenter, the surface texture is again recorded. Apart from the possible inaccuracies in the measurements, which are dependent on the different dimensions of stylus and indenter, such that the recorded surface texture does not necessarily correspond to that of the indenter's path, a further disadvantage is that it is only possible to determine the plastic component, i.e. the irreversible part of the test specimen's deformation.
In DE-OS 39 26 676 it is suggested that the stylus' indentation depth, measured as a function of applied force, is utilised for hardness testing. In addition to this, the stylus can be traversed over the test specimen's surface producing a scratch. However, since only the position of the loaded stylus is measured, this method allows only the total deformation, i.e., the sum of the elastic and plastic components of the deformation, to be recorded.
Consequently, the known methods for determining the mechanical properties of a test specimen's surface are regarded as disadvantageous, since either only the plastic component or the sum of the elastic and plastic components of the deformation can be detected. A method for measuring the elastic deformation is not known. Moreover, there is no possibility of gaining information about the form and amount of energy involved in the deformation process; for ex
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Patent Abstracts of Japan, vol. 9, No. 236 (P-390) (1959)21/09/95.
Mesures, vol. 57, nr. 646, Jun. 1992, Paris FR, pp. 66-67, J --P Piantino: "La durete accede au temps reel".
Gabriel Elmar
Weinhold Wolfgang P.
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