, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of the subject matter:
MULTIMODE ANTI-BUCKLING DEVICE FOR EVALUATING BAUSCHINGER PARAMETER FOR TENSION-COMPRESSION CYCLIC TEST

Name and address of the Applicant:
TATA STEEL LIMITED, of Jamshedpur, Jharkhand, India 831001

Nationality: IN

The following specification describes the subject matter and the manner in which it is to be performed.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
[001] The present application does not claim priority from any patent application.
TECHNICAL FIELD
[002] The present disclosure in general relates to the field of material testing devices and more specifically to the anti-buckling devices (or fixtures) of a tensile-compression cyclic test set up.
BACKGROUND
[003] Generally Various material tests are performed to derive the mechanical behavior under various loading conditions and to determine the failure limits. Fatigue tests are used to determine the low cycle fatigue and high cycle fatigue behavior of the materials and the few phenomena like Bauschinger effect. During the tests, the test sample undergoes tension as well as compression during the load reversals, and the thin specimens are very sensitive to buckle without any special arrangement. There are several designs available to avoid the buckling during such tests.
[004] Zhang Mingwei] developed a device for seismic electromagnetic effect of standard coal rock sample (Ref. Figure 1). Zhang Jianjun et al developed an ‘I’ shaped buckling splint as shown in Error! Reference source not found.. Liu et al invented double-shear clamp for testing shearing strength of material (Ref. Figure 3). C.H. Pham investigated the monotonic and reversed shear tests on a pure copper sheet with a thickness of 0.1 mm with the help of (Ref. Figure 4). Fred invented an anti-buckling device shown in Error! Reference source not found.5, holding a metal specimen which is subjected to compression and to rapid cyclical heating and cooling while permitting visual observation. However, for simple tensile and compression test, the design proves to be complicated.
[005] However, these designs lack the features to monitor the gauge section during the tensile test using an external scanner or through video extensometer or extensometer or are complicated in design.
OBJECT OF INVENTION:
[006] The principle object of the present disclosure is to provide an anti-buckling device to prevent buckling of the thin sheet sample during the compression stage of a tension compression cyclic test.
[007] Another object of the present disclosure is to provide an anti-buckling device to prevent buckling of the thin sheet sample during the compression stage of a tension compression cyclic test wherein the sheet sample is visible and accessible for measurement purposes through scanning the gauge length or capturing the strains through video extensometer or by placing extensometer.

[008] Yet another object of the present disclosure is to provide an anti-buckling device which protects the sample throughout the length of the test duration.

[009] Another object of the present disclosure is to avoid the buckling of the sample between the grips and anti-buckling device by eliminating the gap between grip and the anti-buckling device.

[0010] Another object of the present disclosure is to provide an anti-buckling device to avoid any interference with the existing testing procedure by introduction of addition load, heat etc.

[0011] Yet another object of the present disclosure is to provide an anti-buckling which will prevent the thin sample from damage while assembled with the anti-buckling device.

[0012] Another object of the present disclosure is to provide an anti-buckling device which can be disengaged and can be reused for repeated tests.

[0013] Yet another object of the present disclosure is to provide an anti-buckling which achieves compressive strains of more than 5% and with deformation of only gauge area.

[0014] Another object of the present disclosure is to provide an anti-buckling device to make universal anti-buckling device with the help of key and slot mechanism.

[0015] Yet another object of the present disclosure is to provide an anti-buckling wherein key and slot shape, size and movement depend upon the gauge area dimensions and strain direction.

SUMMARY
[0016] The present invention discloses a design for anti-buckling device which can prevent the thin sheet from buckling during the tension compression test as well as allows to get strains measured using extensometer or other means, which can be further used to evaluate the Bauschinger parameter and endurance limit. It allows for larger strains due to key and slot movement.
[0017] Accordingly, the present subject matter discloses an anti-buckling device for tension-compression tests of thin sheet comprising first set of plates, second set of plates and one thin sheet configured to be sandwiched between first set of plates and second set of plates for testing. The first set of plates and second set of plates are configured with plurality of through holes to match each other to form an assembly by fastening means. The first set of plates are mirror image to each other, and second set of plates are mirror image to each other. The first set of plates has protruding key and at least one second set of plates has corresponding slot to form a sliding assembly. In one embodiment, the width of the said slot and width of key in each anti-buckling plate is configured to be less than the width of the thin sheet to prevent the thin sheet from buckling during testing and to make some portion of the thin sheet accessible for strain gauge for measuring strain. The key is configured in such a way that marks on the gauge section of the thin sheet to get sensed or scanned or detected by the video extensometer or measured by placing other type of extensometers. The sides of the two sets of plates facing grips are designed in such way that gap between the grips and these plates is eliminated to avoid any buckling of sample in this reason.
[0018] The first set of plates and at least one second set of plates are configured with two or more through holes each, to clamp one plate over the other with bolt nut and a spring to maintain a balance in the forces acting on the thin sheet sample, through the plates . The plates of anti-buckling device are configured with the higher strength than the thin sheet tested to avoid any deformation of the anti-buckling plates. the other way around is to maintain higher stiffness (or section modulus) by varying the thickness of the plates. The first set of plates and at least one second set of plates are configured to have an identical profile to superimposed over each other for matching and mounting to form an assembly of anti-buckling device. The thin sheet is clamped in the anti-buckling device and the protruding ends of the thin sheet are gripped in grips of a testing machine for testing. In an embodiment, through slot and corresponding key for the gauge length region of plates are configured to be designed as an independent attachment.

BRIEF DESCRIPTION OF DRAWINGS
[0019] The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present subject matter, an example of construction of the present subject matter is provided as figures; however, the present subject matter is not limited to the specific as disclosed in the document and the figures.
[0020] The present subject matter is described in detail with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer various features of the present subject matter.
[0021] Figure 1 illustrates a synchronous monitoring device (Prior Art)
[0022] Figure 2 illustrates an exploded view of a “I” shaped anti buckling splint (Prior Art).
[0023] Figure 3 illustrates a side view of a Double-shear clamp for shear strength test (Prior Art).
[0024] Figure 4 illustrates a side view of an anti-buckling device holding a metal specimen (Prior Art).
[0025] Figure 5 illustrates a side view of an anti-buckling device holding a metal specimen as per present invention.
[0026] Figure 6 illustrates an isometric view of an anti-buckling device holding a metal specimen as per present invention
[0027] Figure 7 illustrates an exploded view of an anti-buckling device holding a metal specimen as per present invention
[0028] Figure 8 illustrates an exploded view of an anti-buckling device holding a metal specimen as per present invention

[0029] REFERRAL NUMERALS:
Element Description Reference Numeral
Thin sheet sample 1
Left top plate 2
Right top plate 3
Extensometer Positioning edge point 4
Bolt 5
Left bottom plate 6
Right bottom plate 7
Bottom Plate 8
Slot 9
Key 10
Through Hole 11
Nut 12
Spring 13
Grip 14

DETAILED DESCRIPTION
[0030] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any anti-buckling device for tension-compression cyclic test and, similar or equivalent to those described herein may be used in the practice or testing of embodiments of the present disclosure, the exemplary, anti-buckling device for tension-compression cyclic test and are now described.
[0031] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments described, but is to be accorded the widest scope consist in this regard, in a generic sense.
[0032] The Anti-Buckling Device consists of one set of identical plates, 2 & 3, and another set of plates, 6 & 7 (mirror image to each other). First set of plates 2 & 3 has protruding key and second set of plates 6 & 7 has corresponding slot. All four anti-buckling device plates, 2, 3, 6 & 7, have three through holes each, 11, to clamp one over the other to exactly match each other with the help of bolt, 5, and nut or any other suitable clamping mechanism, 12. The bolt, 5, can be either of Allen head or normal such that it can just pass through the hole, 11. The bolt, 5, and nut, 12, assembly also contains a spring, 13, to maintain a balance in the forces acting on the thin sheet sample, 1, through the plates, 2, 3, 6 & 7.
[0033] In one embodiment, one set of anti-buckling device plate, 2 & 6, is shown in Error! Reference source not found.. The minimum width of the slot, WSL, (9 in figure 5) width of key WK, (10 in Figure-5), in each anti-buckling plate, 2 & 6, is less than the width of the sample, WSA, this prevents the sample from buckling during testing. If width of the sample is less, it could be adjusted such that some portion of it is accessible for strain gauge (if strain measured by extensometer or strain gauge).
[0034] At the time tension-compression cyclic test for evaluating the Bauschinger parameter (or endurance limit) of thin sheet sample, 1, when the load is compressive, the sample tends to buckle. This very buckling of thin sheet is overcome by the Anti-Buckling Device. The Key, 10, in the plate, 2, as shown in Error! Reference source not found., whose overlap width is smaller than the width of the sample, prevents the sample from buckling and going out of plane. Even if key width is higher than sample width, position is adjusted to decrease the overlap with sample. Since each anti-buckling device plate, 2 & 6, is present on either side of the thin sheet sample, 1, the buckling is prevented from both the sides of the specimen, 1.
[0035] In one embodiment of the invention, the sample width is lesser than the width of the slot or the key or both.
[0036] The thin sheet sample, 1, to be tested is sandwiched between two anti-bucking device plates, 2 & 6, as shown in Error! Reference source not found.. The plates, 2 & 6, are kept in such a way that their identical profile gets superimposed or matches over each other. The plates are fastened with the help of bolt, 5, and nut, 12, (or any suitable fasteners) in such a way that they can be easily unclamped through hand without using any tool. The plates, 2, should not be fastened loose or tight. Proper fastening of plate is very essential for proper experimental result.
[0037] The key, 10, present on the plate, 2, facilitates the marks, on the gauge section of the sample, get sensed or scanned or detected by the video extensometer or measured by placing other type of extensometers. As the sample is tested, the marks, on the sample move away from each other during tensile mode of testing and they (marks) come closer to each other during compression mode of testing. The change in the distance between the marks, during testing is captured by the video extensometer or any other sensor, thereby capturing the strain on the sample. This helps in getting the stress strain curve during tensile and compression mode of testing which eventually is used to evaluate Bauschinger parameter of the sample.
[0038] Grip, 14, of the testing machine grips the sample at the end of the anti-buckling device. The advantage of the present invention is to eliminate gap between ABD and grip of the machine at both ends thus speeding up the sample fixing to the grips. Test is carried out in stress or strain control mode, oscillating between tension and compression modes. For example: Tensile load is subjected to the sample, up to a pre-determined strain through the grips, 14, of the machine then compression load is subjected to the sample till the pre-determined strain. The stress strain data thus captured by the machine through video extensometer (or any other physical measurement) and load cell helps in evaluating Bauschinger parameter of the sample. During the compression mode, ABD prevents the sample from buckling as the width of the obround slot, WD, in the ABD device is smaller than the width of the sample, WSA, thereby preventing the gauge section of the sample to go out of plane or buckle, eliminating the possibility of buckling of the sample, 1. Even during the deformation, since the width of the sample, WSA, decreases, the overlap width of the obround slot, WSL, is lesser than the minimum sample width during the entire test. Sample is tightly held with the help of bolt and nuts thus leaving any scope of deformation in the region which allows the deformation only in the gauge portion.
[0039] The material of construction of ABD should have higher strength than the sample to be tested (or lower strength material with higher stiffness by changing section modulus). The material of ABD should be strong enough (and/or stiff enough) to overcome the force exerted by the sample on the plate of ABD, as shown in Error! Reference source not found., during compression load mode or buckling action to prevent buckling of the experimental sample.
[0040] One point to be noted is that during the experiment it is mandatory to put marks, on the gauge section of the sample if strain is sensed by the video extensometer to get the experimental data.
[0041] This unique design of Anti-buckling device prevents buckling of thin sheet samples during tension compression cyclic test for evaluating the Bauschinger parameter for thin sheets and facilitates the marks on the gauge section of the sample get scanned or sensed through video (or any other physical) extensometer to get the data from the sample.
[0042] Accordingly, the present subject matter discloses an Anti-Buckling Device for tension-compression tests of thin sheet comprising first set of plates (2, 3) and second set of plates (6, 7), one thin sheet (1) configured to be sandwiched between first set of plates (2, 3) and second set of plates (6, 7) for testing. The first set of plates (2, 3) and second set of plates (6, 7), are configured with plurality of through holes (11) to match each other to form an assembly by fastening means. The first set of plates (2, 3) are mirror image to each other and second set of plates (6, 7) are mirror image to each other. The first set of plates (2, 3) has protruding key (10) and at least one second set of plates (6, 7) has corresponding slot (9) to to allow the sliding of one set of plates with other.. A friction reducing element/Teflon tape is configured over the protruding key (10) to allow smooth navigation of thin sheets during tension and compression.The overlapping width of the said slot (9) and width of key (10) in each anti-buckling plate (2, 6) is configured to be less than the width of the thin sheet (1) to prevent the thin sheet (1) from buckling during testing and to make some portion of the thin sheet (1) accessible for strain gauge for measuring strain. The key (10) is configured with marks on the gauge section of the thin sheet (1) to get sensed or scanned or detected by the video extensometer or measured by placing other type of extensometers. The sides of the two sets of plates (2,3) and (6,7) facing grips (not shown) are designed in such way that gap between the grips and these plates is eliminated to avoid any buckling of sample in this region.
[0043] The first set of plates (2, 3) and at least one second set of plates (6, 7), are configured with three through holes (11) each, to clamp one plate over the other with bolt (5), nut (12) and a spring (13) to maintain a balance in the forces acting on the thin sheet sample, (1) through the plates (2, 3, 6, 7). The plates (2, 3, 6, 7) of anti-buckling device are configured with the higher strength than the thin sheet (1) tested to avoid any deformation of the anti-buckling plates (2, 3, 6, 7). The first set of plates (2, 3) and at least one second set of plates (6, 7) are configured to have an identical profile to superimposed over each other for matching and mounting to form an assembly of anti-buckling device. The thin sheet (1) is clamped in the anti-buckling device and the protruding ends of the thin sheet (1) are gripped in grips (14) of a testing machine for testing. In an embodiment, through slot and corresponding key for the gauge length region of plates (2, 3) are configured to be designed as an independent attachment. The anti-buckling device is configured for the testing of thin sheet (1) of 1.2 mm (and less) thickness sheets without any buckling.

Claims:I/WE CLAIM:
1. An Anti-Buckling Device for tension-compression tests of thin sheet comprising
at least one first set of plates (2, 3);
at least one second set of plates (6, 7);
at least one thin sheet (1) configured to be sandwiched between said at least one first set of plates (2, 3) and at least one second set of plates (6, 7);
wherein each of said at least one first set of plates (2, 3) and said at least one second set of plates (6, 7), are configured with plurality of through holes (11) to match each other to form an assembly by fastening means.

2. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 1, wherein said at least one first set of plates (2, 3) are configured to be mirror image to each other and at least one second set of plates (6, 7) are configured to be mirror image to each other.

3. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 1, wherein said at least one first set of plates (2, 3) has a protruding key (10) and at least one second set of plates (6, 7) has corresponding slot (9) to allow the sliding of one set of plates with other.

4. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 3, wherein a friction reducing element is configured over the protruding key (10) to allow smooth navigation of thin sheets during tension and compression.
5. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 3, wherein width of the said slot (9) and width of key (10) in each anti-buckling plate (2, 6) is configured to be less than the width of the thin sheet (1) to prevent the thin sheet (1) from buckling during testing and to make some portion of the thin sheet (1) accessible for strain gauge for measuring strain.

6. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 3, wherein the key (10) is configured with marks on the gauge section of the thin sheet (1) to get sensed or scanned or detected by the video extensometer or measured by placing other type of extensometers.

7. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 1, wherein said at least one first set of plates (2, 3) and at least one second set of plates (6, 7), are configured with three through holes (11) each, to clamp one plate over the other with bolt (5), nut (12) and a spring (13) to maintain a balance in the forces acting on the thin sheet sample, (1) through the plates (2, 3, 6, 7).

8. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 1, wherein said plates (2, 3, 6, 7) of anti-buckling device are configured with the higher strength than the thin sheet (1) tested to avoid any deformation of the anti-buckling plates (2, 3, 6, 7).

9. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 1, wherein said first set of plates (2, 3) and at least one second set of plates (6, 7) are configured to have an identical profile to superimposed over each other for matching and mounting to form an assembly of anti-buckling device.

10. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 1, wherein said thin sheet (1) is clamped in the anti-buckling device and the protruding ends of the thin sheet (1) are gripped in grips (14) of a testing machine for testing.

11. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 1, wherein said anti-buckling device is configured for the testing of thin sheet (1) of 1.2 mm (and less) thickness sheets without any buckling.

12. The Anti-Buckling Device for tension-compression tests of thin sheets as claimed in claim 1, wherein in an embodiment, through slot and corresponding key for the gauge length region of plates (2, 3) are configured to be designed as an independent attachment.
Dated 24th day of March 2020