Measuring and testing – Hardness – By penetrator or indentor
Patent
1983-09-23
1986-03-25
Ruehl, Charles A.
Measuring and testing
Hardness
By penetrator or indentor
G01N 342
Patent
active
045774935
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The current invention refers to a device for performing micromechanical measurements on materials.
It is known that the simplest procedure for determining the behaviour and the physical constants of metallic and non-metallic materials in a micromechanical manner is to measure on the surface of a test object, the penetration depth y of a weighted indentor, such as a pyramid tip, a ball or a conical tip, while varying the force F imparted by the indentor, and to determine a characteristic of the surface layer of the test object from the quotient F/y.
In order to eliminate the inherent disadvantages of this known procedure, i.e. the dependence of the progression of the curve on the penetration depth y influenced by the force or load F and the application time, on the shape and surface consistency of the indentor, as well as, in the case of thin coatings and paint, on the layer thickness, an improved procedure for determining the infinitesimal hardness behaviour (IHV--infinitesimales Harteverhaiten) has been known since 1968. In this known procedure the quotient of the force F and the penetration depth y is plotted over the force F. However, the resulting curve is also dependent on the parameters stated. However, its point of intersection with the Y-axis forms a limiting value the IHV value, is a significant, well defined material value which is changed in a characteristic manner by the condition of and slightest changes to the material by external, often targeted, influences. Extensive tests and theoretical research have shown that the following is applicable: IHV.about.C .sqroot.E, whereby C is a practically constant value for certain classes of materials and E the elastic modulus of the test object material.
In the IHV procedure, known since 1968, the registration of the value pairs F, y and of the quotients F/y, the calculation of the quotients F/y, as well as the determination of the functional dependence of the penetration depth y on the force F and of the IHV value are done essentially manually, whereby it is natural to use the usual instruments for measuring hardness. The determination of individual IHV values, and even more so the determination of a series of IHV values, take a long time.
A procedure for the determination of the infinitesimal hardness behaviour (IHV) of materials, which can be done many times faster and more accurately, is known from DE-PS No. 23 57 755. In this procedure, also known as IMD (Infinitesimal Module Determination), the surface of the test object is continuously weighted and is subject to individual weighting which changes continuously in the same manner. At time intervals the instantaneous force F and the thus attained value y of the penetration depth are determined and stored for digital registration. The stored value pairs F/y, F are processed to determine the function F/y=F/y(F), and subsequently a digital IHV value is calculated and displayed by the machine by the previously stated limit formation.
The disadvantage of all previously known methods for micromechanical measurements was that only small and very small objects, measuring, e.g. from a few millimeters to a maximum of 4 cm lateral length, could be set up for measurement in stationary machine, placed in a vibrationless manner.
SUMMARY OF THE INVENTION
It is the task of the present invention to make possible micromechanical measurements, especially according to the IHV or IMD procedure, also on large objects.
With the invention it becomes possible to execute micromechanical measurements without the need of a small surface test object. IHV or IMD measurements of the type known from DE-PS No. 23 57 755 may be directly performed on large objects such as machines, vehicles, facades etc. in a rapid and reliable manner.
Instead of aiming for the desired precision in the usual manner by using smaller and smaller weight weighting objects, it is possible with the current invention to use large measuring units which register well and accurately to automatically determine the regularity of t
REFERENCES:
patent: 3877297 (1975-04-01), Oesterle
patent: 4159640 (1979-07-01), Leveque et al.
patent: 4245496 (1981-01-01), Napetschnig
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