Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Patent
1994-06-14
1995-10-31
Williams, Hezron E.
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
425406, 100258R, 72389, A01J 2100
Patent
active
054619289
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a compressing device ensuring a pure compression of a sample or specimen having two parallel faces between which it is compressed without any prior regulating operation of the press being necessary, even at high temperatures and for high loads.
BACKGROUND ART
Conventional mechanical testing machines used for such tests normally require difficult settings in order to obtain a strictly uniaxial stress, i.e. a pure and uniform compression on the specimen. They are generally constituted by two facing parts (by planar faces) and wherein one is a fixed support and the other a mobile piston. The sample is compressed by the advance of the piston, but long and difficult operations are necessary in order to reestablish a correct alignment of the two parts.
DISCLOSURE OF THE INVENTION
A satisfactory solution to this problem is offered by the invention, which is characterized in that the support and the piston are in each case constituted by two parts joined by a respective swivel joint, the parts which carry the planar faces being constructed so as to slide in one another.
Therefore said parts form an assembly which can be looked upon as a one-piece assembly, except in the testpiece compression direction. The double link by a swivel joint makes it possible to only transmit, in combination with the sliding bar adjustment, compressive stresses, despite all the deformations which may be caused by heat on the device.
The independence of the device with respect to the mechanical testing machine offers other advantages. It is easy to insert the device carrying the planar faces into a heating enclosure. These parts and the specimen are then heated to the desired test temperature, whereas the other parts which transmit the compressive force remain relatively cold.
The compression device is made from graphite with a low ash level (in order to prevent degassing at high temperature), because said material has good mechanical properties, which improve at high temperatures. However, the planar faces can advantageously belong to ceramic anvils, e.g. made from zirconia, in order to ensure a good mechanical strength at high temperatures.
BRIEF DESCRIPTION OF THE DRAWING
The single drawing illustrates an embodiment of the invention in a purely illustrative manner.
BEST MODE FOR CARRYING OUT THE INVENTION
The test machine comprises a furnace enclosure 1 formed from two cylindrical half-shells which close on one another and whereof only one is shown here. This half-shell has two diametrically opposite openings 2 and 3. A piston rod 4 fixed to a stationary frame 6 passes through one and a fixed support rod 5 through the other. The latter is fixed to a mobile jack 7 dependent on an electronic control system in order to compress a sample or specimen E. The piston 4 extends up to an end 8, whose free end face is in the form of a concave spherical cap 9. The support rod 5 also has an end 10 terminated by a free end face in the form of a concave spherical cap 11.
The support of the compressing device 12 is placed, without any prior setting, on the concave spherical cap 11 by a surface in the form of a convex spherical cap, which therefore forms a swivel joint with the spherical cap 11. It carries at its other end a bore 13 having a circular section in which slides the piston end 14 of the compression device, which has the same section and whose upper end is terminated by a convex spherical cap, which is partly fitted into the concave spherical cap 9 so as to form another swivel joint. There is only a very small clearance between the end of the piston 14 and the bore 13. An alignment error between the piston 14 and the fixed support rod 5 consequently leads to a different position of the support 12 and the end of the piston 14, but the force transmitted between these two parts remains parallel to the axis of the end of the piston 14.
The specimen support 12 is hollowed out to form a transverse depression 16 into which issues the bore 13. Into depression 16 it is introduced the specimen E.
REFERENCES:
patent: 2864253 (1958-12-01), Lenton
patent: 3545263 (1970-12-01), Hadley et al.
patent: 3975950 (1976-08-01), Erdei
patent: 4599215 (1986-07-01), Smarsly et al.
patent: 5272904 (1993-12-01), Krumholz
Azzolini Raymond
Rochard Pierre
Commissariat a l''Energie Atomique
Moller Richard A.
Williams Hezron E.
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