WO2016120629A1 - Adaptateur, dispositif de test de contrainte modifié et procédé de réalisation d'un test de contrainte multi-axiale - Google Patents

Adaptateur, dispositif de test de contrainte modifié et procédé de réalisation d'un test de contrainte multi-axiale Download PDF

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Publication number
WO2016120629A1
WO2016120629A1 PCT/GB2016/050196 GB2016050196W WO2016120629A1 WO 2016120629 A1 WO2016120629 A1 WO 2016120629A1 GB 2016050196 W GB2016050196 W GB 2016050196W WO 2016120629 A1 WO2016120629 A1 WO 2016120629A1
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WO
WIPO (PCT)
Prior art keywords
adaptor
sample
connectors
pivot points
axis
Prior art date
Application number
PCT/GB2016/050196
Other languages
English (en)
Inventor
Davide DE FOCATIIS
Samuel Kelly
Original Assignee
The University Of Nottingham
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by The University Of Nottingham filed Critical The University Of Nottingham
Publication of WO2016120629A1 publication Critical patent/WO2016120629A1/fr

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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
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • 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
    • G01N2203/025—Geometry of the test
    • G01N2203/0254—Biaxial, the forces being applied along two normal axes of the specimen
    • 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
    • G01N2203/026—Specifications of the specimen
    • G01N2203/0262—Shape of the specimen
    • G01N2203/0278—Thin specimens
    • G01N2203/0282—Two dimensional, e.g. tapes, webs, sheets, strips, disks or membranes
    • 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
    • G01N2203/0435—Chucks, fixtures, jaws, holders or anvils modifying the type of the force applied, e.g. the chuck transforms a compressive machine for applying a bending test

Definitions

  • This invention relates to an adaptor, a modified stress testing device and a method of performing a multi-axial stress test.
  • Stress tests performed on samples of a material include uniaxial stress tests and multi- axial stress tests.
  • a uniaxial stress test a sample is deformed along a single axis, leading to a uniaxial stress state in the sample.
  • a multi-axial stress test a sample is deformed along at least two axes, leading to a biaxial or triaxial stress state in the sample.
  • a biaxial stress test may be performed, in which deformations acting in two axes are applied to the sample.
  • a uniaxial stress testing device which has two opposing clamps which are arranged to move relative to each other along a single axis .
  • the relative movement of the opposing clamps (which are attached to the sample) impose a kinematic state (e.g. a deformation) on the sample.
  • a state of stress is thus generated by the imposed deformation, which can be measured by measuring one or more forces experienced by the sample.
  • a biaxial stress testing device may be used, which provides two pairs of clamps, each pair driven independently, such that they move relative to each other in two different axes of motion.
  • Such biaxial stress testing devices require complex drive systems in order to impose controlled deformations along two axes, and are therefore complicated to manufacture and use.
  • An adaptor (which may be referred to in the art as a fixture) may be provided to adapt a uniaxial stress testing device such that a biaxial state of deformation can be applied to a sample.
  • Such an adaptor is arranged to translate a uniaxial deformation applied by a uniaxial stress testing device into a biaxial deformation that can be applied to the sample.
  • a known adaptor 100 for a uniaxial stress testing machine is shown in Figure 1.
  • This known adaptor 100 is arranged to convert a uniaxial driving deformation acting in the direction of arrows A and B, into a biaxial deformation acting in the direction of arrows C, D, E, and F.
  • the uniaxial deformation may be supplied by attaching the adaptor 100 to a uniaxial stress testing machine (not shown in Figure 1) via adaptor clamps 102a, 102b.
  • the adaptor 100 is arranged to hold a cruciform shaped sample 104 in a set of four sample clamps 106a, 106b, 106c, 106d.
  • the adaptor further comprises four pairs of pivotally connected bars which are connected between the sample clamps and the adaptor clamps as shown in Figure 1.
  • the adaptor 100 therefore translates a uniaxial driving deformation into a biaxial deformation which is applied to the sample 104.
  • This known adaptor 100 has a number of drawbacks.
  • the arrangement of bars required to generate a biaxial deformation limits the access available to the sample.
  • the pivotally connecting bars surround the sample and so make it difficult to find access for a camera used to monitor the sample during testing. Therefore it is known to mount a camera on moving parts of the adaptor, for example, a camera may be mounted to one of the adaptor clamps 102a, 102b. As the adaptor clamps 102a, 102b move with respect to the sample 104, the camera will also move with respect to the sample .
  • a transformable adaptor for a uniaxial stress testing device the adaptor arranged to move between a contracted and an expanded configuration, and being connectable to the stress testing device via two adaptor connectors such that the adaptor connectors undergo uniaxial displacement relative to each other along a driving axis as the transformable adaptor moves between the contracted and expanded configurations, wherein the adaptor is connectable to the sample via at least three sample connectors, and wherein the adaptor is arranged to translate the uniaxial displacement into a first test displacement of a first pair of the sample connectors relative to each other along a first test displacement axis, and a second test displacement of a second pair of the sample connectors relative to each other along a second test displacement axis, wherein the first test displacement axis and the second test displacement axis define an adaptor plane, the adaptor plane being parallel to the driving axis.
  • the adaptor By providing an adaptor that translates the uniaxial driving displacement of the adaptor connectors into multi-axial displacements of the sample connectors that are in a plane parallel to the driving axis, the adaptor does not obscure the view of (or other access to) the sample. This is advantageous over known adaptors, such as that shown in Figure 1 , in which the view of the sample is obstructed by the components of the adaptor required to translate the uniaxial displacement into biaxial deformations experienced by the sample.
  • the adaptor is a planar adaptor. This means that the adaptor will generally be in the adaptor plane such that it does not obscure the view of the sample. Contrary to this, the known adaptors of the type shown in Figure 1 have parts that extend significantly out of the adaptor plane which will obscure the view of the sample during testing.
  • the adaptor may be arranged to move between the contracted position and the expanded position such that the sample connectors move in known configurations when displaced along the first test displacement axis and the second test displacement axis. This means that the deformation applied to the sample has a known relationship with the uniaxial displacement such that the deformation applied to the sample can be related to the displacement along the driving axis.
  • the known configurations comprise a series of ellipses or circles.
  • a circular known configuration means that the displacement of the connectors along the first test displacement axis is equal to the displacement of the connectors along the second test displacement axis.
  • the known configurations may comprise a series of ellipses of different eccentricity, in which the test displacements are greater in one direction compared to another.
  • the adaptor may comprise an adaptor portion which comprises a plurality of adaptor members, and a sample portion arranged to receive the sample.
  • the sample portion may be an empty space within the adaptor which is arranged to receive the sample.
  • the adaptor members may be pivotally connected to each other. This allows the adaptor to move between the contracted position and the expanded position.
  • each adaptor member may comprise at least two pivot points. This allows the adaptor members to move with respect to each other such that the adaptor can move between the contracted position and the expanded position.
  • the adaptor members may be arranged to move in the adaptor plane . This means that as the adaptor moves between the contracted and expanded positions, the adaptor members do not obscure the view to the sample from a point perpendicular to the adaptor plane.
  • each sample connector may be connected to (e.g. positioned at, or located at) one of the pivot points.
  • the pivot points may be arranged in the known configuration and provide a suitable place from which to attach the sample .
  • each adaptor connector may be connected to (e.g. positioned at, or located at) one of the pivot points.
  • the pivot points may comprise a first set of pivot points and a second set of pivot points, wherein the first set of pivot points is nearer to the sample portion than the second set of pivot points.
  • the adaptor portion surrounds the sample portion.
  • each sample connector may be connected to (e.g. positioned at, or located at) one of the first set of pivot points.
  • first set of pivot points By connecting the sample connectors to the first set of pivot points a greater range of deformation applied to the sample may be achieved.
  • each adaptor connector may be connected to (e.g. positioned at, or located at) one of the first set of pivot points.
  • first set of pivot points By connecting both the adaptor connectors and the sample connectors to the same first set of pivot points, the magnitude of the displacement of the adaptor connectors is replicated at the sample connectors.
  • the adaptor members are substantially identical in shape and size. This means that adaptor members are arranged to move symmetrically with respect to each other to provide equal test displacements (e.g. for equibiaxial testing). This also means that the adaptor is more easily manufactured and assembled. In other embodiments, for example where equal displacements are not required, the adaptor members may not be identical, i.e. some or all of the adaptor members may be different sizes or shapes.
  • ⁇ ⁇ (1— 2/n)
  • any one or more of the sample connectors may comprise a sensor arranged to measure the force experienced by the sample via that sample connector. This allows the stress state of the sample to be measured.
  • the invention provides a modified stress testing device comprising an adaptor according to any preceding claim.
  • a multi-axial stress test may be performed without requiring a multi-axial stress testing device.
  • the modified stress testing device may further comprise a camera arranged to monitor the sample during application of the test force, wherein the camera is directed along a camera axis perpendicular to the adaptor plane (or along a camera axis that is angled such that it is not parallel to the adaptor plane or not along the driving axis.
  • the camera axis may be angled at 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° to the adaptor plane, or any range between any two of these values).
  • the combination of the planar nature of the adaptor and the position of the camera means that the view of the camera is not obstructed when the adaptor moves between the contracted and expanded positions.
  • the camera may be mounted to be stationary relative to the sample. This means that the image recorded by a stationary camera will vary only according to the changing size of the sample, not because of the relative distance between the camera and the sample.
  • the invention provides a method of performing a multi- axial stress test, the method comprising: connecting an adaptor to a uniaxial stress testing device via two adaptor connectors; connecting a sample to be tested to the adaptor via at least three sample connectors; and driving the adaptor such that the adaptor connectors undergo uniaxial displacement relative to each other along a driving axis and such that the uniaxial displacement is translated by the adaptor into a first test displacement of a first pair of the sample connectors relative to each other along a first test displacement axis, and a second test displacement of a second pair of the sample connectors relative to each other along a second test displacement axis, , wherein the first test displacement axis and the second displacement axis define an adaptor plane, the adaptor plane being parallel to the driving axis.
  • a uniaxial stress testing device to perform a multi-axial stress test by using the adaptor of this invention to transform the uniaxial driving displacement into a multi-axial test displacement.
  • the skilled person in this field will understand how to configure the multiple sample connectors. For example, when there are eight sample connectors and biaxial testing is required, then there may be four sample connectors facilitating displacement along a first test displacement axis and four sample connectors facilitating displacement along a second test displacement axis.
  • sample connectors facilitating displacement along a first test displacement axis and six sample connectors facilitating displacement along a second test displacement axis.
  • the method may further comprise monitoring the sample during application of the test forces, wherein the monitoring is carried out by a camera acting along an axis perpendicular to the adaptor plane (and therefore perpendicular to the driving axis). This allows the sample to be monitor by the camera such that the adaptor does not obscure the view of the sample .
  • Figure 1 shows a prior art adaptor for a uniaxial stress testing device
  • Figures 2a and 2b show a schematic perspective view of an adaptor according to an embodiment of the invention
  • Figure 2c shows a side view of the adaptor shown in Figures 2a and 2b;
  • Figures 3a, 3b and 3c show a detailed view of an adaptor according to an embodiment of the invention
  • Figure 3d shows a close up view of an adaptor member of the adaptor shown in Figure 3a, 3b and 3c;
  • FIGS. 4a and 4b show an adaptor according to another embodiment of the invention.
  • FIGS 5a and 5b show an adaptor according to another embodiment of the invention.
  • Figures 6a and 6b show a modified stress testing device according to an embodiment of the invention.
  • Figure 7a shows an end view of an adaptor connector suitable for use with the adaptor of the invention;
  • Figure 7b shows a top view of an adaptor connector suitable for use with the adaptor of the invention;
  • Figure 7c shows a first side view of an adaptor connector suitable for use with the adaptor of the invention.
  • Figure 7d shows a second side view of an adaptor connector suitable for use with the adaptor of the invention.
  • FIG. 2a and 2b An adaptor 200 according to an embodiment of the invention is shown schematically in Figures 2a and 2b.
  • the adaptor is arranged to move between a contracted and an expanded configuration, the contracted configuration being shown in Figure 2a and the expanded configuration being shown in Figure 2b .
  • the adaptor 200 can be connected to a uniaxial stress testing device (not shown in Figures 2a and 2b) via two adaptor connectors such that it is driven by a uniaxial driving displacement.
  • the uniaxial driving displacement acts along a driving axis 202.
  • the adaptor connectors undergo uniaxial displacement relative to each other along the driving axis 202 which moves the adaptor between the contracted and expanded configurations.
  • the adaptor 200 is connectable to a sample 204 via at least three sample connectors, but in the example shown schematically in Figure 2a and 2b, there are four sample connectors.
  • the sample is connected such that there is no relative movement (or substantially no relative movement) between the sample and the sample connectors.
  • the adaptor is arranged to translate the uniaxial displacement into a first test displacement of a first pair of the sample connectors relative to each other along a first test displacement axis 206a, and a second test displacement of a second pair of the sample connectors relative to each other along a second test displacement axis 206b.
  • the first and second test force axes 206a, 206b define an adaptor plane 208.
  • the first and second test displacements are perpendicular to each other, but in other embodiments, there may be more than two pairs of sample connectors whose test displacement axes may have different relative angles, as will be described later.
  • any reference to the application of separate test displacements (or deformations) to the sample could also be interpreted as a single state of deformation acting on the sample, but having displacement (or deformation) components acting along different axes.
  • the adaptor could equally be considered to be arranged to transform the driving displacement into a state of deformation to be applied to the sample, the deformation having components acting along at least two axes.
  • the adaptor is arranged to translate the uniaxial driving displacement such that the adaptor plane 208 is parallel to the driving axis 202.
  • the adaptor plane 208 and the driving axis 202 may not be exactly parallel.
  • the adaptor plane 208 may be arranged such that it is angled with respect to the driving axis 202 by an angle of less than: 5 °, 10°, 25°, 30°, 40° 50°, 60°, or any range of angles defined between these values.
  • the adaptor plane is arranged such that it is not perpendicular to the driving axis. In all of these embodiments, the adaptor provides improved access to the sample during the testing process from a view point perpendicular to the adaptor plane relative to known adaptors.
  • the adaptor plane 204 is spaced apart from the driving axis 202 (e.g. the driving axis is not in the adaptor plane 202 - the driving axis is spaced apart from the adaptor plane 202).
  • the driving axis 202 may lie within the adaptor plane 208 (e.g. the adaptor plane may overlap the driving plane 203).
  • the sample is attached to the outside of the body of the adaptor and so is not in precisely the same plane as the point at which the driving displacement is applied to the adaptor (e.g. the driving axis).
  • Figure 2c shows a side view of the adaptor 200. This shows the sample 204 connected so that it rests on the outside of the adaptor body and so is not in precisely the same plane as the adaptor connectors 212a, 212b.
  • the sample may be spaced apart from the adaptor body.
  • the sample may be positioned within the adaptor body such that it is in line with the adaptor connectors which are displaced when the adaptor is driven by the uniaxial stress testing device.
  • the driving axis 202 and adaptor plane 208 will overlap.
  • the adaptor can provide improved access to the sample 204. This is because the access for a camera view (i.e. the line of sight for a camera), or any other type of access, is left relatively unimpeded compared to a known adaptor that has components that are displaced in a non-parallel plane and thereby obstruct access to a sample.
  • the adaptor 200 is a planar adaptor i.e. it is generally disposed along or within the adaptor plane 208.
  • the body of the adaptor is therefore generally planar in shape, and does not extended significantly out of the adaptor plane 208.
  • the adaptor body does not extend out of the adaptor plane 208 in the region surrounding the sample 204.
  • the device may be another type of monitoring device or a device that is arranged to affect the sample in some way, e.g. it may apply heat during stretching.
  • the adaptor 200 comprises four sample connectors 210a, 210b, 210c, 210d arranged to connect the sample 204 to the adaptor 200.
  • sample connectors 210a, 210b, 210c, 210d arranged to connect the sample 204 to the adaptor 200.
  • at least three sample connectors are required.
  • two sample connectors may be provided to apply a uniaxial deformation, which may be in a different direction to the driving axis 202.
  • more than four sample connectors may be provided to apply test deformations that act along more than two axes. This applies a more uniform state of deformation to the sample and means that a circular shaped sample may be used rather than a cruciform sample.
  • the sample connectors may comprise any means suitable to connect the sample to the adaptor, and may in particular comprise clamps arranged to grip the sample 204 in some examples.
  • the sample connectors may comprise for example, screw-action grips, self-locking wedge grips, pneumatically actuated grips and the like.
  • one or more of the sample connectors may comprise a sensor (e.g. a load cell) arranged to measure the force applied to the sample at that sample connector.
  • a sensor arranged to measure the load applied to the adaptor may be provided as part of the uniaxial testing device, or at one or more of the adaptor connectors.
  • the adaptor 200 further comprises two adaptor connectors 212a, 212b (only one of which is visible in Figures 2a and 2b) arranged to connect the adaptor 200 to the uniaxial stress testing device . This allows the sample connectors to be displaced relative to each other along the driving axis such that the adaptor is moved between the contracted and expanded configurations.
  • the adaptor connectors 212a, 212b may comprise any mechanism suitable for connecting the adaptor to the uniaxial stress testing machine, and in particular may comprise clamps arranged to grip points on the adaptor body.
  • the adaptor connectors may comprise pivot pins extending through the body of the adaptor.
  • the adaptor connectors 212a, 212b are shown connected to a top and bottom edge or surface of the adaptor body. In other embodiments, the adaptor connectors may be connected to any part of the adaptor body.
  • the uniaxial stress testing machine is arranged to pull the adaptor connectors 212a, 212b apart along the first axis 202 in the direction indicated by arrows A and B in Figures 2a and 2b.
  • the adaptor connectors 212a, 212b When being pulled apart, only one of the adaptor connectors may move, while the other remains stationary, such that the distance between them increases. Displacement is therefore applied to the adaptor 200, which is then translated into displacements in the directions indicated by arrows C, D, E and F.
  • Such displacements may be required, for example, if the sample comprises a flexible material which is to be tested under biaxial tension.
  • the uniaxial stress testing machine may move the adaptor connectors 212a, 212b towards each other along the first axis 202 in directions opposite to arrows A and B .
  • This provides a state of uniaxial compressive deformation to the adaptor 200, which is then translated into a state of biaxial compressive deformation in the opposite direction to arrows C, D, E and F.
  • a modified adaptor connector may be required to maintain the orientation of the adaptor connector during compression of the sample.
  • the modified adaptor connector of such an example may comprise a slider to maintain the orientation of the grip during the compression.
  • the adaptor 200 is arranged to move between a contracted position, as shown in Figure 2a, and an expanded position as shown in Figure 2b.
  • the sample connectors 210a, 210b, 210c, 210d move in a known configuration to deform the sample.
  • a known test displacement of the sample connectors is provided.
  • the known configuration comprises a series of circles, one of which is shown in Figure 2a and a second of which is shown in Figure 2b.
  • the sample connectors are arranged in a series of circles of differing diameters which progressively increase in size when the adaptor 200 moves from the contracted to the expanded position.
  • the known configuration may comprise a series of ellipses of different eccentricity. This allows non-uniform deformations to be applied to the sample along the first and second test displacement axes 206a, 206b.
  • the deformation applied along one of the first and second test displacement axes may, for example be 2, 3, 4 or more times greater than the deformation along the other.
  • the deformation along one axis may remain constant while the deformation is applied along the other axis.
  • the known configuration may be a complex shape arranged to provide test deformations which are tailored for any particular testing requirement.
  • FIG. 3a, 3b and 3c A specific example of an adaptor 300 according to an embodiment of the invention is shown in schematically in Figures 3a, 3b and 3c. This is only one example embodiment of such an adaptor, and demonstrates one of a number of suitable embodiments as will be described later.
  • the adaptor 300 comprises an adaptor portion 302 and a sample portion 304 which is arranged to receive a sample 306 of material which is under test.
  • the sample shown in Figures 3a, 3b and 3c is circular, the sample could be any other shape, such as cruciform for example (for example by connecting the sample via only four of the available sample connectors).
  • the sample 304 may be a flexible material, or may in other embodiments be a rigid material, and may be generally of any size and shape, but may preferably be a sheet of flexible material.
  • the adaptor portion 302 comprises a plurality of adaptor members 308. In the embodiment shown in Figures 3a, 3b and 3c, the adaptor members 308 are arranged to surround the sample portion 304 such that the sample portion is generally at the centre of the adaptor 304. In this embodiment, the sample portion 304 comprises an empty area which is surrounded by the adaptor members 308. The sample may be received in the sample portion 304 and attached to the adaptor. In this embodiment, the adaptor plane and the first axis overlap as the sample can be positioned in line (e.g.
  • the sample portion may also comprise adaptor members such that the area of the sample portion is also filled or partly filled with adaptor members 308.
  • the sample is attached to the outside of the adaptor (e.g. such that it is on top of the adaptor body or on the surface of the adaptor body, as shown schematically Figure 2c) such that the adaptor plane and the first axis are spaced apart as shown in the embodiment of Figures 2a, 2b and 2c.
  • the adaptor portion comprises 16 adaptor members 308 (only one of which is labelled in the figures). This is however only one example of such an adaptor, and in other embodiments the adaptor may comprise 8, 10, 12, 14, 18, 20 or more adaptor members as will be described later.
  • Each adaptor member 308 comprises an element as shown in Figure 3d.
  • the adaptor members may comprise straight or angled members as described later.
  • the adaptor members are pivotally connected to each other so that they may move with respect to each other. This allows the adaptor 300 to change in shape when it moves between the contracted and the expanded positions as shown by the sequence of Figures 3a, 3b and 3c. As the adaptor 300 changes in shape, a sample rigidly attached to the adaptor will experience a deformation.
  • the adaptor members are preferably rigid so that they do not significantly deform under the action of the driving deformation applied to the adaptor.
  • the adaptor members are substantially identical in shape and size. This allows the adaptor 300 to move in a symmetrical configuration, and also means that the adaptor members 308 are more easily manufactured.
  • the adaptor members may all be of different sizes or shapes, or some may be a first size or shape, and others may be a second size or shape . This allows the adaptor to move in an asymmetric configuration to apply an inhomogeneous test displacement to the sample.
  • the adaptor members may be shaped such that the known configuration is elliptical rather than circular.
  • each adaptor member 308 is interconnected by a plurality of pivots points.
  • each adaptor member 308 comprises four pivot points - a first pivot point 3 10a, a second pivot point 3 10b, a third pivot point 3 10c and a fourth pivot point 3 10d.
  • each adaptor member may comprise three pivot points (as shown in the embodiment of Figures 5a and 5b, and discussed later), or two, or five or more pivot points.
  • each adaptor member 308 are spaced along the length of the respective adaptor member 308 such that the first pivot point 3 10a is generally at a first distal end of the adaptor member, whilst the fourth pivot point 3 10d is generally at a second distal end of the adaptor member 308.
  • the pivot points of each adaptor member 308 are equally spaced along its length. In other embodiments, the pivot points may be unequally spaced along the length of each adaptor member.
  • the adaptor members 308 are interconnected such that the first pivot point 3 10a of each adaptor member is pivotally connected to the first pivot point 3 10a of another, neighbouring adaptor member.
  • each of the adaptor members is pivotally connected to the second pivot point of another, neighbouring, adaptor member.
  • the third 3 10c and fourth 3 10d pivot points are similarly connected.
  • the pivot points may be connected by pivot pins (e.g. may be pin-joints) or any other suitable connection means such as rotary bearings, flexible joints, or the like.
  • Each adaptor member 308 may comprise a number of angulated portions.
  • each adaptor member 308 comprises four such angulated portions 3 12a, 3 12b, 3 12c as shown in Figure 3d.
  • each adaptor member may be straight, or comprise two or more angulated portions. The angulated portions are separated by the pivot points disposed along the length of each adaptor member as shown in Figure 3d.
  • the inside angle between each angulated portion 3 12a, 3 12b, 3 12c, labelled ⁇ in Figure 3d is preferably equal such that the adaptor member is symmetrical in shape.
  • the inside angles of each adaptor member may not be identical in other examples.
  • the combination of the shape of the adaptor members 308 and the position of the pivot points allows the adaptor members 308 to move with respect to each other such that they remain in the adaptor plane.
  • the adaptor 300 is generally planar in shape and has no significant part of its body extending out of the adaptor plane . This improves the access to the sample 306 during testing as none of the adaptor members are arranged to move out of the adaptor plane and block the view of the sample from a viewing direction substantially perpendicular to the sample.
  • the adaptor members 308 are arranged such that they extend generally radially out from the sample region 304.
  • the pivot points thus form a first, second, third and fourth set of pivot points (which are connected by the concentric broken circles in Figures 3a, 3b and 3c), with the distance from the adaptor region 304 increasing between each set.
  • the first set of pivot points comprises the first pivot point 3 10a of each adaptor member
  • the second set of pivot points comprises the second pivot point 3 10b of each adaptor member
  • the third set of pivot points comprises the third pivot point 3 10c of each adaptor member
  • the fourth set of pivot points comprises the fourth pivot point 3 10d of each adaptor member.
  • the first set of pivot points is nearest to the sample portion 304, and in the described embodiment is therefore nearest to the centre of the adaptor 300.
  • the fourth set of pivot points is furthest from the sample region, and therefore the furthest from the centre of the adaptor.
  • the sample portion 304 may not be at the centre of the adaptor, and so the first set of pivot points may not be closest to the centre of the adaptor.
  • each set moves in a known configuration when the adaptor moves between its contracted and expanded configurations.
  • the known configuration comprises points on a circle.
  • these circular known configurations expand in size .
  • a sample 306 connected to the pivot points is therefore stretched as the adaptor moves from the contracted to the expanded position.
  • the adaptor further comprises sample connectors 3 14 (only one of which is labelled in Figures 3a, 3b and 3c).
  • the sample connectors may comprise a body which comprises a connection to the sample and a connection to the adaptor, such that the test forces are transferred from the adaptor 300 to the sample 306.
  • the sample connectors 3 14 may comprise any mechanism suitable for attaching the sample to a point on the adaptor.
  • the sample connectors may comprise clamps arranged to grip the sample, and may comprise for example, screw-action grips, self-locking wedge grips, pneumatically actuated grips and the like.
  • one or more of the sample connectors may comprise a sensor (such as a load cell) arranged to measure the force generated by the displacement of the sample at that sample connector.
  • the sample connectors are preferably connected to the adaptor 300 at three or more of the pivot points.
  • Each of the sample connectors 3 14 may be pivotally connected to the pivot points, and may for example be connected via the same pivot pin arranged to interconnect the adaptor members 308.
  • the sample connectors 3 14 may be attached to the body of the adaptor members 308, or may be part of the adaptor members themselves.
  • the sample connectors may be attached to the adaptor members 308 between the pivot points rather than at the pivot points.
  • At least three sample connectors 3 14 are required to apply a multi-axial state of deformation to the sample 306, but in some embodiments, more than three sample connectors 3 14 can be provided to connect the adaptor 300 to the sample 306 at more points. This means that the deformation applied to the sample is more uniform (e.g. is more homogeneous). In yet other embodiments, only two sample connectors 3 14 may be provided. In this case, a uniaxial deformation is applied to the sample 3 16, which can be in a different direction to that of driving axis depending on the positioning of the sample connectors 3 14 on the adaptor 300. As the pivot points move in a known configuration, by attaching the sample connectors 3 14 to the pivot points, known test deformations can be applied to the sample 306.
  • the sample connectors 3 14 are preferably connected to the first set of pivot points as shown in Figures 3a, 3b and 3c.
  • the sample 306 may be connected via sample connectors 3 14 attached to all of the first set of pivot points.
  • the sample is therefore connected via eight sample connectors 3 14 which are dispersed evenly around the known circular configuration. This provides an even, homogenous state of deformation to be applied to the sample 306. It also means the sample may be generally circular in shape (where a sheet material is being tested, for example), rather than the cruciform sample shape typically used for biaxial stress testing.
  • the sample may be connected via sample connectors 3 14 attached to some, but not all of, the first set of pivot points. This means that the deformation applied to the sample is less homogenous, but allows samples of different shapes to be tested. In some embodiments, an uneven deformation may be required, in which case the sample can be connected via a number of the sample connectors 3 14 arranged asymmetrically around the circular known configuration. In yet other embodiments, sample connectors may be provided at each of the first set of pivot points, but can be left unconnected to vary the attachment position to the sample 306.
  • the sample connectors may be attached to the second, third or fourth set of pivot points. It yet other embodiments, the sample connectors may be attached to a mixture of pivot points from any number of the first, second, or third or fourth sets of pivot points. This allows a wide range of sample sizes and shapes to be tested.
  • the adaptor 300 further comprises at least two adaptor connectors 3 16a, 3 16b arranged to connect the adaptor 300 to the uniaxial stress testing device. Each of the adaptor members may comprise a rigid body arranged to communicate the driving force from the uniaxial stress testing machine to the adaptor.
  • the adaptor connectors may each comprise a connection mechanism arranged to attach them to the uniaxial stress testing machine at one end, and another connection mechanism arranged to attach them to the adaptor at a second end.
  • two adaptor connectors are provided to drive the adaptor 300 with a uniaxial drive.
  • Each of the adaptor connectors 3 16a, 3 16b may be connected to one of the pivot points. Similarly to the sample connectors 3 14, the adaptor connectors 3 16a, 3 16b may be connected via one of the pivot pins connecting two of the adaptor members 308. In other embodiments, each of the adaptor connectors 3 16a, 3 16b may be attached to the body of one of the adaptor members 308 or be part of one of the adaptor members.
  • the adaptor connectors 3 16a, 3 16b are preferably connected to two of the first set of pivot points as shown in Figures 3a, 3b and 3c. This is advantageous because the movement of the adaptor connectors 3 16, 3 16b is then replicated at the other pivot points of the first set.
  • the body of each of the adaptor connectors may comprise a slot arranged to receive the adaptor such that each of adaptor connectors fits around the outside of the adaptor.
  • the adaptor connectors 3 16a, 3 16b may be provided at two of the second, third or fourth sets of pivot points. In yet other embodiments, they may be connected to pivot points belonging to different sets of pivot points.
  • the adaptor 300 shown in Figures 3a, 3b, 3c and 3d is one example of a number of possible arrangements of adaptor members 308.
  • the number of adaptor members 308, the shape of the adaptor members 308, or the number of pivot points on each adaptor member 308 may be varied.
  • the number of pivot points in the first set of pivot points (i.e. the innermost pivot points closest to the sample region 304) is varied.
  • the number of pivot points to which the sample connectors 3 14 can be attached is increased.
  • the uniformity of the stress state generated in the sample is increased. For the special case in which the sample connectors move in a circular configuration, the force measured along the driving axis is equal to nil times the test force measured at each pair of sample connectors.
  • the test force is 4 times the force between each pair of adaptor connectors.
  • An example embodiment of an adaptor 400 in which there are 24 adaptor members 408 and 12 first pivot points 410a in the first set of pivot points is shown in Figure 4a in the contracted position, and Figure 4b in the extended position.
  • the change in position of the first set of pivot points between the contracted and extended position is shown by the arrows marked A in Figures 4a and 4b .
  • increasing the number of adaptor members increases the homogeneity of the stress state, the complexity of the adaptor also increases .
  • the inventor has found that 16 adaptor members (as shown in the embodiment of Figures 3a, 3b and 3 c) may provide a balance between these factors, but in other embodiments, there may be other suitable numbers of adaptor members .
  • the size and shape of the adaptor members themselves may also be varied.
  • the angle between the angulated portions, ⁇ may be varied.
  • this angle is therefore 135 ° .
  • ⁇ is 150 ° .
  • the angle between the angulated portions, ⁇ may however have other dependencies on the number of pivot points, with this being only one such example .
  • each adaptor member may also be varied.
  • Each adaptor member may comprise at least two pivot points so that the adaptor members can move relative to each other in some embodiments .
  • Figures 5a and 5b show an embodiment of an adaptor 500 where there are 16 adaptor members 508, each having three pivot points 5 10a, 5 10b, 5 10c.
  • the number of first pivot points 5 10a in the first set of pivot points is therefore unchanged from the embodiment of Figures 3a, 3b and 3c.
  • the embodiment of Figures 5a and 5b is less restricted in its movement by removing the outer layer (e.g. the fourth set) of pivot points .
  • the expanded position shown in Figure 5b
  • it is therefore expanded to a greater size . This greater range of movement is advantageous because it allows a greater deformation to be applied to the sample .
  • this invention provides a modified stress testing device 600 comprising the adaptor of any previously described embodiment.
  • a stress testing device 600 is shown in Figure 6a and 6b .
  • the stress testing device 600 has been modified by attachment of the adaptor 300 of the embodiment shown in Figures 3a, 3b and 3c.
  • the adaptor 300 is in the contracted position, and in Figure 6b it is in the expanded position.
  • the modified stress testing device 600 comprises a frame 602.
  • a first attachment point 604a and a second attachment point 604b are connected to the frame as shown in Figure 6a and 6b.
  • the first attachment point 604a is located on a movable member which is arranged to move with respect to the frame to apply a state of deformation to the sample 306.
  • both of the first and second attachment points may be arranged to move with respect to the frame in order to deform the sample. This may be advantageous if the centre of the specimen is required to remain stationary during the test.
  • the adaptor 300 is attached to the stress testing machine 600 by attaching the first adaptor connector 3 16a to the first attachment point 604a and the second adaptor connector 3 16b to the second attachment point 604b.
  • an existing uniaxial stress testing device such a device can be modified to allow a multi-axial stress test to be carried out. This advantageously allows a uniaxial device, which is less complex and therefore simpler to use and more widely available, to be used to perform a multi-axial stress test.
  • Such a modified stress testing device may further comprise a camera arranged to monitor the sample during application of the test force .
  • the camera may be directed along a camera axis having at least one component perpendicular to the first axis. By positioning the camera in this way, it has a clear, unobstructed view of the sample. As the adaptor of this invention moves in the adaptor plane as described above, it does not move in such a way as to obstruct the view of the sample.
  • the camera may also be mounted such that it remains stationary relative to the sample . This is advantageous because the image recorded by a stationary camera will vary only according to the changing size of the sample, not because of the relative distance between the camera and the sample.
  • the camera may be attached to one of the adaptor clamps 102a, 102b because the pivotally connected bars would otherwise obscure the view of the sample. If the camera is located at one of the adaptor clamps 102a, 102b it will move relative to the sample during testing. It will therefore be difficult to distinguish movement of the camera from changes in the size of the sample during testing.
  • the camera may be replaced by any suitable monitoring equipment such as an X-ray imaging device, spectrometer, infrared camera, neutron beam etc.
  • the camera may be replaced by or supplemented by an instrument arranged to modify the sample, and may for example be a heat source.
  • An external pressure, vacuum, humidity and/or temperature may also be imposed to the sample by, for example, carrying out the test in an atmospheric control chamber.
  • the adaptor of this invention is first connected to a uniaxial stress testing device. As described above, the adaptor is arranged to transform the uniaxial driving displacement provided by the uniaxial stress testing machine into a multi-axial test displacement. Once the adaptor is connected to the uniaxial stress testing device, the sample is connected to the adaptor. This may be done via the sample connectors as described above. Once the sample is connected, the adaptor is driven with a uniaxial driving displacement provided by the uniaxial stress testing device such that multi- axial test displacements are applied to the sample.
  • the sample connector 700 comprises a sample attachment portion 702, a sensor portion 704 and an adaptor attachment portion 706.
  • the sample attachment portion 702 comprises a mechanism with which to attach the sample connector 700 to the sample.
  • the sample attachment portion comprises a pair of opposing grip members 708a, 708b which are arranged to grip the sample such that it is secured to the sample connector.
  • the grip members 708a, 708b may comprise a threaded portion arranged to engage with the body of the sample connector so that when rotated they move with respect to the body of the sample connector 700 in order to grip the sample.
  • the grip members may be biased towards each other by any other suitable mechanism such as a spring, or a pneumatic or hydraulic actuator for example .
  • the sensor portion 704 comprises a sensor (such as a load cell) arranged to measure the force acting between the sample attachment portion and the adaptor attachment portion. This provides an indication of the load applied at the sample via the sample connector 700 and may provide an indication of the stress state experienced by the sample.
  • a sensor such as a load cell
  • the adaptor attachment portion 706 comprises a mechanism arranged to attach the sample connector to the adaptor.
  • the adaptor connector may be attached via the pivot points of the adaptor.
  • the adaptor attachment portion 706 may comprise a pair of apertures 710a, 710b (only one of which is visible in Figure 7b) which are arranged to receive a pin connecting two of the adaptor members 308.
  • the sample connectors may comprise, for example, screw-action grips, self-tightening wedge grips, pneumatically actuated grips and the like.
  • the adaptor is a non-powered adaptor - that is, its movement does not need an internal power source. It is powered only by the testing device . This simple construction provides an efficient way of achieving multi-axial testing on a uniaxial testing device . In other embodiments, the adaptor may be powered by an internal power source .

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  • 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

L'invention concerne un adaptateur transformable (200) pour un dispositif de test de contrainte uniaxiale. L'adaptateur (200) est agencé pour se déplacer entre une configuration contractée et une configuration déployée, et peut être relié au dispositif de test de contrainte par l'intermédiaire de deux connecteurs d'adaptateur (212a, 212b) de telle sorte que les connecteurs d'adaptateur subissent un déplacement uniaxial l'un par rapport à l'autre le long d'un axe d'entraînement (202) à mesure que l'adaptateur transformable se déplace entre les configurations contractée et déployée. L'adaptateur peut être relié à l'échantillon par l'intermédiaire d'au moins trois connecteurs d'échantillon (210a; 210b; 210c; 210d). L'adaptateur (200) est agencé pour translater le déplacement uniaxial en un premier déplacement de test d'une première paire des connecteurs d'échantillon (210a; 210b; 210c; 210d) l'un par rapport à l'autre le long d'un premier axe de déplacement de test (206a), et un second déplacement de test d'une deuxième paire des connecteurs d'échantillon (210a; 210b; 210c; 210d) l'un par rapport à l'autre le long d'un second axe de déplacement de test (206b), le premier axe de déplacement de test (206a) et le second axe de déplacement de test (206b) définissant un plan d'adaptateur (208). Le plan d'adaptateur (208) est parallèle à l'axe d'entraînement (202). Un procédé de réalisation d'un test contrainte multi-axiale est également décrit.
PCT/GB2016/050196 2015-01-30 2016-01-29 Adaptateur, dispositif de test de contrainte modifié et procédé de réalisation d'un test de contrainte multi-axiale WO2016120629A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1501599.3 2015-01-30
GBGB1501599.3A GB201501599D0 (en) 2015-01-30 2015-01-30 An adaptor, a modified stress testing device and a method of performing a multi-axial stress test

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WO2016120629A1 true WO2016120629A1 (fr) 2016-08-04

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110325837A (zh) * 2017-02-27 2019-10-11 汤浅系统机器株式会社 变形测试仪
CN114486533A (zh) * 2022-04-18 2022-05-13 天津航天和兴科技有限公司 一种用于导弹适配器的分区式智能测试系统及其测试方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5905205A (en) * 1998-04-06 1999-05-18 The United States Of America As Represented By The Secretary Of The Air Force Biaxial testing apparatus
US6860156B1 (en) * 2004-05-24 2005-03-01 The United States Of America As Represented By The Secretary Of The Navy Combined in-plane shear and multi-axial tension or compression testing apparatus
FR2875907A1 (fr) * 2004-09-28 2006-03-31 Univ Lille Sciences Tech Dispositif de test pour effectuer une traction, afin d'appliquer a une eprouvette un champ de deformation biaxiale
JP2009244183A (ja) * 2008-03-31 2009-10-22 Mitsubishi Materials Corp 二軸引張試験装置
US20110314926A1 (en) * 2009-03-10 2011-12-29 Mitsubishi Materials Corporation Biaxial tensile testing machine
EP2570791A2 (fr) * 2011-09-15 2013-03-20 Bayern-Chemie Gesellschaft für flugchemische Antriebe mbH Dispositif de détermination des valeurs caractéristiques d'extension biaxiales d'un échantillon

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5905205A (en) * 1998-04-06 1999-05-18 The United States Of America As Represented By The Secretary Of The Air Force Biaxial testing apparatus
US6860156B1 (en) * 2004-05-24 2005-03-01 The United States Of America As Represented By The Secretary Of The Navy Combined in-plane shear and multi-axial tension or compression testing apparatus
FR2875907A1 (fr) * 2004-09-28 2006-03-31 Univ Lille Sciences Tech Dispositif de test pour effectuer une traction, afin d'appliquer a une eprouvette un champ de deformation biaxiale
JP2009244183A (ja) * 2008-03-31 2009-10-22 Mitsubishi Materials Corp 二軸引張試験装置
US20110314926A1 (en) * 2009-03-10 2011-12-29 Mitsubishi Materials Corporation Biaxial tensile testing machine
EP2570791A2 (fr) * 2011-09-15 2013-03-20 Bayern-Chemie Gesellschaft für flugchemische Antriebe mbH Dispositif de détermination des valeurs caractéristiques d'extension biaxiales d'un échantillon

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110325837A (zh) * 2017-02-27 2019-10-11 汤浅系统机器株式会社 变形测试仪
CN110325837B (zh) * 2017-02-27 2022-04-01 汤浅系统机器株式会社 变形测试仪
CN114486533A (zh) * 2022-04-18 2022-05-13 天津航天和兴科技有限公司 一种用于导弹适配器的分区式智能测试系统及其测试方法

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