GB2101337A - Clamping device for a machine for testing materials - Google Patents
Clamping device for a machine for testing materials Download PDFInfo
- Publication number
- GB2101337A GB2101337A GB08217535A GB8217535A GB2101337A GB 2101337 A GB2101337 A GB 2101337A GB 08217535 A GB08217535 A GB 08217535A GB 8217535 A GB8217535 A GB 8217535A GB 2101337 A GB2101337 A GB 2101337A
- Authority
- GB
- United Kingdom
- Prior art keywords
- clamping
- clamping device
- load
- test piece
- spring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/04—Chucks
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/0202—Control of the test
- G01N2203/0208—Specific programs of loading, e.g. incremental loading or pre-loading
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
- G01N2203/0222—Temperature
- G01N2203/0226—High temperature; Heating means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/04—Chucks, fixtures, jaws, holders or anvils
- G01N2203/0423—Chucks, fixtures, jaws, holders or anvils using screws
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/04—Chucks, fixtures, jaws, holders or anvils
- G01N2203/0458—Chucks, fixtures, jaws, holders or anvils characterised by their material
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
In a clamping device for machines for carrying out alternating stress and alternating elongation tests at high temperatures on materials, the clamped ends of the material test piece in each case are tensioned in a clamping element with a loading element. The tensioning must be adapted at high temperatures to the lessening strength of the clamping element. For the automatic adaptation of the tensioning, the loading element (7) consists of a compression- resistant material, which has a lower coefficient of expansion than the material of the clamping elements (6) for the test piece (3). In addition, spring means with a degressive characteristic curve (Fig. 2 not shown) is provided for producing the initial stress on the loading element. Through making use of the differing linear expansion behaviours of the loading element (7) and of the clamping element (6) in connection with a spring (9) with a degressive characteristic curve an automatic adaptation of the expansion force Fv to the strength of the clamping element (6) at high temperature is possible. <IMAGE>
Description
SPECIFICATION
Clamping device for a machine for testing materials
This invention relates to a clamping device for a machine for testing materials, in particular for a machine for carrying out alternating stress and alternating elongation tests at high temperatures.
Clamping devices for this purpose have been proposed comprising holding or clamping units arranged on a testing machine, with clamping elements for a testpiece or suchlike of material to be tested, two load punches acting one upon each of the clamped ends of the test piece for tensioning these ends with respect to the clamping elements, whereby the initial stressing of the load punch, necessary for the required tensioning, can be adapted to the temperature of the test piece or of the clamping elements.
In such clamping devices, the test piece of material to be tested must be held in the clamping elements such that, with all the test conditions which occur, no play arises in the clamping. For this purpose the test piece is formed with clamping heads which are tensioned or prestressed in the clamping elements. The initial stressing is selected such that with alternating directions of force and with varying temperatures, freedom from play during testing is ensured.
The clamping elements directly connected with the test piece consist of high-grade material with good high-temperature characteristics. Their strength, like the strength of other metallic materials, is highly temperature responsive at high temperatures. The initial stressing force or the restraining force between the clamping head of the test piece and the clamping element must therefore be adapted at high temperatures to the altered, i.e. reduced strengths, and must be reduced accordingly.
In order to apply the pre-stressing, each clamping head of the test piece is acted upon by a load punch. The load punch, which is passed through the clamping element, and acts on the frontal area of the clamping head, braces the clamping head against the clamping element. The test piece may, for example, have threaded clamping heads, and be screwed into sleeveshaped clamping elements. A shoulder-headclamping or another suitable clamping may also be provided for the test piece.
The load punch is pre-stressed mechanically or hydraulically in the previous proposed devices. For the mechanical pre-stressing, suitable spring arrangements, which are adjustable by hand are used, so that varying initial stressing forces or restraining forces may be applied between the clamping head of the test piece and the clamping element. If hydraulic arrangements are used to produce the initial stressing, the load punch is connected with an operating cylinder or operating piston, which is acted upon by a pressure medium.
Through control or regulation of the pressure in the operating cylinder, the pre-stressing of the load punch can be adjusted. With mechanical prestressing devices, adjustment of the initial stress by hand is complicated. Hydraulic pre-stressing arrangements require a not inconsiderable expense.
It is an object of the present invention to improve and simplify the known clamping device.
It is also an object of the invention to enable an automatic adjustment of the initial stress acting upon the clamping heads of the test piece to be made in dependence upon the temperature. The initial stress should be adaptable to the strength of the material of the clamping elements at varying temperatures, in particular to the decrease in strength at high temperature, so that an adjustment by hand or a corresponding control or regulating device can be eliminated.
According to the present invention there is provided a clamping device for a machine for carrying out alternating stress and alternating elongation tests at high temperatures on materials, wherein mounting or clamping units are provided for mounting on the testing machine, the clamping units including clamping elements for holding a test piece or suchlike of the material to be tested, there being two load punches arranged to act one on each of the clamped ends of the test piece, when present, to tension these ends with respect to the clamping elements, and wherein the load punch consists of a material which has a lower coefficient of expansion than the material of which the clamping elements are made and which is pressure-resistant over the range of temperature at which the material is to be tested, there being spring means with a degressive characteristic curve for acting on the load punches to produce an initial stress whereby the initial stress of the load punch, necessary for the tensioning, is adaptable to the temperature of the test piece or of the clamping elements.
The use of a spring with a diminishing characteristic curve in connection with a load punch, the material of which has a lower coefficient of expansion than the material of the clamping elements, enables the initial stress on the clamping point of the test piece to be adapted automatically to the decrease in strength of the clamping elements. The diminishing part of the spring characteristic curve is selected such that the elastic force alters with the spring deflection as little as possible. Through coordination of the spring characteristic curve with the expansion behaviour of the load punch and of the clamping element, it is achieved that even at high temperature the pre-stressing on the clamping point of the test piece always lies below the permissible strength factor for the clamping element.
The load punch is preferably produced from a ceramic material, and the spray means is advantageously in the form of plate springs, which make it possible, in a simple manner, to produce a diminishing spring characteristic curve. The maximum spring deflection of the spring may be adjustable and the spring itself may be interchangeably mounted so that it can be interchanged with similar springs of differing degressive characteristics appropriate to a selected range of temperatures at which testing is to take place.
In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings, which illustrate diagrammatically and by way of example an embodiment thereof, and in which: Figure 1 is a schematic view of a clamping device according to the invention with a spring
loaded load punch acting upon a clamping head of
a test-piece,
Figure 2 is a graph showing a diminishing
spring characteristic curve, and
Figure 3 is a graph showing the strength
pattern of a material highly resistant to elevated
temperatures.
Referring now to Figure 1 of the drawings,
there is shown a clamping device having clamping
units 1, 1' attached in a suitable manner to a
testing machine 2, 2' represented by way of
indication. The clamping unit 1' may, for example,
be built on to a fixed part 2' of the machine, e.g. to
a cross-head, and the clamping unit 1 may be fixed to a movable piston rod 2 of the loading
device of the testing machine. The two units 1 and
1' are substantially similar in design. In the
drawing, therefore, only clamping unit 1 is shown
in detail.
A test-piece 3 is arranged between the two clamping units 1, 1'. The test-piece is formed with threaded clamping heads 3' and is connected with the clamping units 1, 1'. To carry out the temperature tests, an oven or heating installation 4 is provided, which surrounds the test-piece 3 and the ends of the clamping units.
The clamping unit 1 consists of a base member 5 and a clamping element 6. The base member 5 is yoke-shaped or cylinder-shaped, and is fixed with its open end facing the testing machine or
piston rod 2. The clamping element 6 is connected on a cross-piece or cover of the base member 5, in a suitable manner, e.g. through a screw
connection. The clamping element 6 is designed in the form of a sleeve and is formed on the end
intended to receive the test-piece with an internal thread to receive the threaded clamping head 3' of the test-piece 3. In place of the threaded clamping, also another type of clamping, e.g. a shoulder head clamping, can be provided for the test-piece.The clamping element 6 consists of
material highly resistant to elevated temperatures, whilst the base member 5 may be made of conventional materials since during testing the base member is practically not heated or may be cooled if required.
A load punch 7 of a suitable pressure-resistant ceramic material is mounted in the clamping element 6, the material of which the punch is made having a lower coefficient of thermal expansion than the material of which the clamping element 6 is made. The load punch 7 is connected with a plate 8 which is acted upon by plate springs 9. The plate springs can be supported on the loading apparatus 2 or on the base member 5, if this is designed accordingly. Through the plate springs 9, via the plate 8 and the load punch 7, an initial stressing force F, is applied onto the threaded clamping head 3' of the test-piece 3, by which force the clamping head is tensioned against the clamping element 6.In this way the freedom from play of the clamping is ensured in alternating stress and alternating elongation tests and as a consequence, the testing force on the test piece cannot exceed the initial stressing force of the plate springs.
In place of the plate springs, other springs or spring arrangements with degressive characteristic curve may be used to produce the initial stress. The base member 5 can be designed such that the plate springs may be easily exchanged, and that their maximum initial stressing force is adjustable at ambient temperature.
Since the strength of the clamping element 6 decreases sharply at high temperatures, an initial stressing force which is harmless at ambient temperature can damage the clamping element at high temperature. Until now, this was prevented through adjustment of the initial stressing force by hand or through hydraulic regulation of the initial stressing force for the respective test case.
Through the arrangement according to the invention, an automatic adaptation of the initial stressing force F, to the temperature prevailing at the test piece or at the clamping point of the test piece, and hence to the resistance to heat of the clamping element 6, takes place.
In order to produce the initial stressing force, plate springs with a degressive or diminishing characteristic curve are used. With these springs, the spring tension increases at the beginning of the spring deflection firstly in an approximately linear manner. As the spring deflection increases, the increase in tension becomes less until the spring tension finally remains constant or even decreases again towards the end of the spring deflection. The qualitative progress of the spring tension F over the spring deflection s is represented in Figure 2 for such a spring with degressive characteristic curve. For the present arrangement, the plate springs are selected such that the spring tension remains as constant as possible in the end region of the spring deflection (A to B in Figure 2) and in the initial region (B to C) rises approximately uniformly.
The strength of the clamping element 6 remains approximately the same up to a certain temperature in the range of approximately 500 to 6000 C. Thereafter it falls in an approximately linear manner with the temperature. A typical strength curve or curve of the permissible stress crz related to the temperature t for a heat-resistant material of which the clamping elements are made, is represented in Figure 3.
The different expansion behaviours of the clamping element 6 and of the load punch 7 have the result that with increasing temperature on the clamping device, the clamping element 6 and the load punch 7 expand to an unequal extent, whereby the clamping element expands more than the load punch owing to the higher coefficient of expansion. The difference of the deformations in extension can be determined with a given length of the two parts for a given temperature difference. The difference between the deformation in extension of the load punch 7 compared with that of the clamping elements 6 is used as a basis for establishing the spring characteristic curve of the plate springs.The spring deflection and the spring tension of the plate springs 9, i.e. the characteristic curve of the plate springs, is thereby adjusted to the expansion behaviour of the load punch 7 and of the clamping element 6 over the temperature range such that the initial stress F, at the clamping point of the test piece automatically adapts itself to the alteration in strength of the clamping element 6.
In this connection, the initial stress of the plate springs at ambient temperature is selected in accordance with the desired initial stress at the clamping point. With this initial stress, the plate springs are pressed together in an effectively integral state, and exert via the load punch 7 the desired initial stress F, at the clamping point of the test piece. This state corresponds to Point A in
Figures 2 and 3.
When the clamping element 6 and the load punch 7 warm up, the load punch must be reset in the clamping element 6 owing to its lower degree of linear expansion. This takes place through the expansion of the plate springs. The latter act firstly in the constant region of the spring characteristic curve, i.e. alterations to the spring deflection produce only slight, or no alterations to the spring tension. This state corresponds to the region A to
B in Figures 2 and 3.
Point B of the spring characteristic curve (Figure 2), at which the decrease in the spring tension begins with decreasing spring deflection, is placed such that it coincides with Point B of the strength curve of the clamping element 6 (Figure 3), from which point the strength of the clamping element decreases with rising temperature.
If the temperature on the clamping device rises beyond Point B further in direction of C (Figure 3), the load punch 7, because of its lesser heat expansion, is constantly reset through the plate springs 9 in the clamping element 6. The further expansion of the plate springs caused through this now leads, however, to the spring tension decreasing in an approximately linear manner with the spring deflection, corresponding to the region
B to C in Figure 2. Corresponding to the fall in strength of the clamping element in the region B to C in Figure 3, caused through the rise in temperature, a reduction in the initial stressing force of the plate springs corresponding to the region B to C in Figure 2 is simultaneously obtained.
The spring characteristic curve of the plate springs 9 and the differing linear expansion behaviour of the clamping element 6 and of the
load punch 7 are therefore adjusted to each other
such that, with rising temperature and the
reduction in strength of the clamping element 6
beginning, the initial stressing force of the plate
springs also decreases. Through this, the
automatic adaptation of the initial stress to the
respective strength of the clamping element 6
results. The initial stressing of the plate springs is
selected such that the permissible stress of the
clamping elements is not exceeded in the entire temperature range of the device. Through
corresponding coordination, a substantial
approximation of the strength characteristic curve
of the clamping elements and of the characteristic
curve of the plate springs can be achieved.
With decreasing temperature, the relationships are reversed; with a temperature decreasing from
C to B or to A, the strength of the clamping element 6 increases again (Figure 3); at the same time the linear expansion of the clamping element 6 and of the load punch 7 are reduced to differing extents. Because of this, the initial stressing force of the springs again rises from value C to value B or A (Figure 2).
Claims (7)
1. A clamping device for a machine for carrying out alternating stress and alternating elongation tests at high temperatures on materials, wherein mounting or clamping units are provided for mounting on the testing machine, the clamping units including clamping elements for holding a test piece or suchlike of the material to be tested, there being two load punches arranged to act one on each of the clamped ends of the test piece, when present, to tension these ends with respect to the clamping elements, and wherein the load punch consists of a material which has a lower coefficient of expansion than the material of which the clamping elements are made and which is
pressure-resistant over the range of temperature
at which the material is to be tested, there being spring means with a degressive characteristic curve for acting on the load punches to produce an initial stress whereby the initial stress of the load punch, necessary for the tensioning, is adaptable to the temperature of the test piece or of the clamping elements.
2. A clamping device as claimed in claim 1, wherein the characteristic curve of the spring means and the expansion behaviour of the load punch and of the clamping element are coordinated with each other such that the tensioning or initial stressing force adapts to the alteration in strength of the clamping element with an alteration in temperature.
3. A clamping device as claimed in Claim 1 or 2, wherein the load punch consists of a ceramic material.
4. A clamping device as claimed in Claim 1, 2 or 3, wherein the spring means is in the form of a plate spring.
5. A clamping device as claimed in any one of the preceding Claims, wherein the maximum spring deflection of the spring means is adjustable.
6. A clamping device as claimed in any one of the preceding Claims, wherein the spring means are interchangeably mounted.
7. A clamping device for a machine for carrying out alternating stress and alternating elongation test at high temperature on materials substantially as hereinbefore described with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19813124877 DE3124877C2 (en) | 1981-06-25 | 1981-06-25 | Clamping device for materials testing machines to carry out alternating stress and alternating expansion tests at high temperatures |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2101337A true GB2101337A (en) | 1983-01-12 |
| GB2101337B GB2101337B (en) | 1985-04-11 |
Family
ID=6135302
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08217535A Expired GB2101337B (en) | 1981-06-25 | 1982-06-17 | Clamping device for a machine for testing materials |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS586440A (en) |
| CH (1) | CH656006A5 (en) |
| DE (1) | DE3124877C2 (en) |
| GB (1) | GB2101337B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2143044A (en) * | 1983-06-28 | 1985-01-30 | Heldenbrand W C | Pipe testing apparatus |
| WO2014039344A1 (en) * | 2012-09-05 | 2014-03-13 | Vetco Gray Inc. | Valve actuator with degressive characteristic spring |
| EP3144661A4 (en) * | 2014-05-14 | 2017-11-08 | Shimadzu Corporation | Material testing machine |
| CN117054229A (en) * | 2023-10-12 | 2023-11-14 | 中海油田服务股份有限公司 | Fixing device and method for testing reliability of circuit board of logging while drilling instrument |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3872962D1 (en) * | 1987-06-19 | 1992-08-27 | Schenck Ag Carl | SAMPLE CLAMPING DEVICE FOR TESTING MACHINES. |
| DE4101321A1 (en) * | 1991-01-18 | 1992-07-23 | Messerschmitt Boelkow Blohm | HIGH TEMPERATURE PRESSURE STRENGTH TEST |
| JP5366230B2 (en) * | 2010-04-26 | 2013-12-11 | 日本電気株式会社 | Fixing jig for fatigue test specimen and fatigue test equipment |
| JP6049378B2 (en) * | 2012-09-26 | 2016-12-21 | 三菱重工業株式会社 | Fatigue testing equipment |
| CN103884588B (en) * | 2014-04-16 | 2017-05-24 | 四川材料与工艺研究所 | Curved surface sample tensile property test fixture |
| CN107421807B (en) * | 2017-08-31 | 2020-09-15 | 西安热工研究院有限公司 | Compression clamp and method for measuring high-temperature compression yield strength of small-size plastic material |
| CN112504825A (en) * | 2020-11-11 | 2021-03-16 | 中国原子能科学研究院 | Test fixture capable of measuring temperature of test sample with fracture toughness |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2653544C3 (en) * | 1976-11-25 | 1979-08-30 | Carl Schenck Ag, 6100 Darmstadt | Clamp connection for test devices |
| DE2819902C2 (en) * | 1978-05-06 | 1980-08-07 | Carl Schenck Ag, 6100 Darmstadt | Mechanical clamping device for testing machines |
-
1981
- 1981-06-25 DE DE19813124877 patent/DE3124877C2/en not_active Expired
-
1982
- 1982-01-14 JP JP350882A patent/JPS586440A/en active Granted
- 1982-06-17 GB GB08217535A patent/GB2101337B/en not_active Expired
- 1982-06-23 CH CH384982A patent/CH656006A5/en not_active IP Right Cessation
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2143044A (en) * | 1983-06-28 | 1985-01-30 | Heldenbrand W C | Pipe testing apparatus |
| WO2014039344A1 (en) * | 2012-09-05 | 2014-03-13 | Vetco Gray Inc. | Valve actuator with degressive characteristic spring |
| EP3144661A4 (en) * | 2014-05-14 | 2017-11-08 | Shimadzu Corporation | Material testing machine |
| US9995664B2 (en) | 2014-05-14 | 2018-06-12 | Shimadzu Corporation | Material testing machine that properly performs a tensile test on a test piece |
| CN117054229A (en) * | 2023-10-12 | 2023-11-14 | 中海油田服务股份有限公司 | Fixing device and method for testing reliability of circuit board of logging while drilling instrument |
| CN117054229B (en) * | 2023-10-12 | 2023-12-19 | 中海油田服务股份有限公司 | Fixing device and method for testing reliability of circuit board of logging while drilling instrument |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6336452B2 (en) | 1988-07-20 |
| DE3124877C2 (en) | 1985-07-25 |
| JPS586440A (en) | 1983-01-14 |
| GB2101337B (en) | 1985-04-11 |
| CH656006A5 (en) | 1986-05-30 |
| DE3124877A1 (en) | 1983-01-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930617 |