CN117871287A - Microscale material torsion testing device and method based on feedback tracking - Google Patents
Microscale material torsion testing device and method based on feedback tracking Download PDFInfo
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Abstract
The invention provides a micro-scale material torsion testing device and method based on feedback tracking, wherein the testing device comprises a data acquisition and control unit, a frame, a torque measuring mechanism and a driving and torsion angle measuring mechanism; the torque measuring mechanism is used for measuring the torque loaded on the sample to be measured and comprises an upper suspension assembly, a lower suspension assembly, an electromagnetic induction assembly and a measuring assembly, wherein the upper suspension assembly is installed on the upper part of the frame in a matching way; the driving and torsion angle measuring mechanism is arranged in the middle of the frame in a matched manner; the sample to be measured is matched and clamped between the driving and torsion angle measuring mechanism and the measuring assembly; the data acquisition and control unit is respectively and electrically connected with the electromagnetic induction assembly, the measuring assembly and the driving and torsion angle measuring mechanism. The invention has reasonable conception, can realize 360-degree full-angle measurement and frictionless feedback tracking, and is suitable for popularization and application.
Description
Technical Field
The invention belongs to the field of torsion mechanical property testing of microscale materials, and particularly relates to a device and a method for torsion testing of microscale materials based on feedback tracking.
Background
With the application of micro-nano materials in the key technical fields of biomedical science, electronic information, environment, energy and the like, the requirements for mechanical property testing of micro-scale materials are also increasing. On a macro scale, the mechanical property test of the material can depend on a commercial material testing machine; on the micro-nano scale, the micro-scale one-dimensional material torsion test faces the problem of accurate measurement of micro torque, electromagnetic driving and torque measurement are good methods, but torsion angle measuring range is limited by the fact that a coil structure cannot break through 180 degrees, and the application range of the technology is limited.
Disclosure of Invention
Aiming at the technical problems in the background technology, the invention provides a microscale material torsion testing device and method based on feedback tracking, which have reasonable conception, can realize 360-degree full-angle measurement and friction-free feedback tracking, and can effectively obtain the real torque loaded on a sample.
In order to solve the technical problems, the invention provides a microscale material torsion testing device based on feedback tracking, which comprises a data acquisition and control unit, a rack, a torque measuring mechanism and a driving and torsion angle measuring mechanism, wherein the torque measuring mechanism and the driving and torsion angle measuring mechanism are arranged on the rack in a matching way;
The torque measuring mechanism is used for measuring the torque loaded on the sample to be measured and comprises an upper suspension assembly, a lower suspension assembly, an electromagnetic induction assembly and a measuring assembly, wherein the upper suspension assembly is installed on the upper part of the frame in a matching way; the driving and torsion angle measuring mechanism is arranged in the middle of the frame in a matched mode; the sample to be measured is matched and clamped between the driving and torsion angle measuring mechanism and the measuring assembly; the data acquisition and control unit is respectively and electrically connected with the electromagnetic induction assembly, the measuring assembly and the driving and torsion angle measuring mechanism.
The microscale material torsion testing device based on feedback tracking, wherein the upper suspension assembly comprises an upper moving platform, an upper fixing frame, an upper suspension and a rectangular suspension; the upper moving platform is fixed on the upper part of the frame in a matching way and has the functions of adjusting the X direction and the Y direction; the upper fixing frame is arranged on the upper moving platform in a matching way in a threaded connection way, and the upper fixing frame can be displaced up and down along Z by adjusting threads; the upper suspension is a metal wire with certain rigidity, and the upper end of the upper suspension penetrates into the upper fixing frame and is clamped and fixed through a screw; the rectangular hanging part is connected with the lower end of the upper hanging part in a matching way, and is rigidly connected with the upper hanging part.
The microscale material torsion testing device based on feedback tracking, wherein the lower suspension assembly comprises a lower moving platform, a lower fixing frame, a lower suspension, a cavity horse riding screw, a ball head and a nut; the lower moving platform is fixed at the lower part of the frame in a matching way and has the functions of adjusting in the X direction and the Y direction; the lower fixing frame is matched and detachably arranged on the lower moving platform, and the lower fixing frame can be vertically displaced along Z through adjusting threads; the lower suspension is a metal wire with certain rigidity, and the lower end of the lower suspension penetrates into the lower fixing frame and is clamped and fixed through a screw; the cavity horse riding screw is profiled on the saddle, the bottom of the saddle is sealed, the center of the saddle is a cavity, and the bottom of the cavity is hemispherical; the ball head is a smooth solid ball body which is placed in the groove of the electromagnetic coil; the ball head is naturally positioned at the bottom center of the groove of the electromagnetic wire frame under the action of gravity and is in point contact with the electromagnetic wire frame; the cavity horse riding screw is matched with the upper end of the ball head and is contacted with the ball head point, and the contact point of the cavity horse riding screw and the ball head is the hemispherical top point of the cavity horse riding screw; the nut is connected with the cavity saddle screw in a threaded matching way.
The micro-scale material torsion testing device based on feedback tracking comprises an electromagnetic induction assembly, a control unit and a control unit, wherein the electromagnetic induction assembly comprises a magnetic group and an electromagnetic wire frameThe method comprises the steps of carrying out a first treatment on the surface of the The magnetic group is fixed in the middle of the rack in a matching way, and provides a uniform and stable magnetic field for the testing device; the electromagnetic wire frame is wound with a wire and is suspended in the magnetic group; the electromagnetic wire frame is of a bag-shaped structure; the length of the parallel edge of the electromagnetic wire frame in the magnetic field is L d According to ampere's law, the ampere force calculation formula generated by the cutting magnetic field of the electrified coil is as follows:
F 0 ＝nBIL d (1)；
in the above formula (1), n is the number of turns of the coil, B is the strength of the uniform magnetic field, I is the energizing current in the coil, L d For the length of the energized coil subjected to ampere force in the magnetic field, ampere force is generated for two sides of the energized coil opposite to each other, and the torque formed by a pair of ampere forces can be expressed as T:
in the above formula (2), L a Is the coil width; the torque output by the coil, the number of turns n of the coil, the magnetic field intensity B, the power supply voltage U and the resistance R of the electrified coil can be obtained according to the formula (2) 0 Coil size L a /L d Correlation; number of turns n, magnetic field strength B, coil size L a /L d Resistance R of energizing coil 0 Are all determined constants; the torque output by the energized coil is positively correlated with the supply voltage, and its magnitude can be expressed as:
T＝K×U (3)；
In the above formula (3), the size of K is obtained by a calibrated method.
The micro-scale material torsion testing device based on feedback tracking, wherein the measuring component comprises a laser displacement sensor and a lower clamp; the laser displacement sensor is arranged in the middle of the frame in a matching way, and the laser emission port faces to the X negative direction; the lower clamp is cylindrical as a whole, the lower part of the lower clamp is provided with a groove and is positioned in the electromagnetic wire frame, and the upper part of the lower clamp is positioned at the outer side of the electromagnetic wire frame; the upper part and the lower part of the lower clamp are installed in a threaded fit manner and are fixed across the electromagnetic wire frame.
The microscale material torsion testing device based on feedback tracking, wherein the axis of the lower clamp is coaxial with the rotation center of the electromagnetic wire frame and can not move or rotate relative to the electromagnetic wire frame; the top end face of the lower clamp is provided with a groove for clamping a sample to be tested;
one part of the side wall of the lower clamp is a plane, the other part of the side wall is an arc surface, and the whole cross section of the lower clamp is of a D-shaped structure; the side wall plane of the lower clamp is used for reflecting laser emitted by the laser displacement sensor; the laser displacement sensor irradiates the X point of the side wall plane of the lower clamp, and the measuring distance is L s The method comprises the steps of carrying out a first treatment on the surface of the The axial line distance between the laser displacement sensor and the lower clamp is L 0 The method comprises the steps of carrying out a first treatment on the surface of the The radius of the arc surface of the lower clamp is R, the minimum distance between the side wall plane of the lower clamp and the axis is M, and the distance between the side wall plane of the lower clamp and the axis is R; the angle between OM and OX is α, then α can be expressed as follows:
when the lower clamp rotates to two different angles, the laser displacement sensors respectively irradiate X of the lower clamp 1 、X 2 At the positions with the measuring distances of L respectively s1 、L s2 The calculation formula of the small included angle delta alpha of the rotation of the lower clamp is as follows:
the micro-scale material torsion testing device based on feedback tracking, wherein the driving and torsion angle measuring mechanism is positioned above the measuring assembly and comprises a driving motor, an angle sensor and an upper clamp; the driving motor is used for providing power required by torsion of the sample to be tested and is fixed in the middle of the frame in a matching manner; the angle sensor is a hollow sensor, can measure 360-degree full-angle range, and the main body part is fixed in the middle of the frame; the power output shaft of the driving motor penetrates through the inside of the rotating shaft of the angle sensor and is fixed through a screw; the angle of the rotation shaft of the angle sensor relative to the main body part is a measurement angle, namely the torsion angle of the driving motor; the upper clamp is arranged on the power output shaft of the driving motor in a matching way, and the upper clamp and the power output shaft are in threaded fit connection; the sample to be tested is vertically clamped between the lower clamp and the upper clamp.
The micro-scale material torsion testing device based on feedback tracking, wherein the data acquisition and control unit comprises a computer and a controller; the computer and the controller are communicated through a USB protocol; the controller is respectively and electrically connected with the laser displacement sensor, the angle sensor, the electromagnetic wire frame and the driving motor through an I/O interface;
the I/O interface comprises an I1 interface, an I2 interface, an I3 interface, an O1 interface, an O2 interface and an O3 interface; the I1 interface, the I2 interface and the I3 interface are data acquisition ports and are respectively used for high-frequency acquisition of signals of the three channels of the laser displacement sensor, the angle sensor and the electromagnetic wire frame; the O1 interface, the O2 interface and the O3 interface are voltage signal output ports; the O1 interface is used for supplying power to the electromagnetic wire frame; the O2 interface is used for supplying power to the angle sensor; the O3 interface is used for supplying power to the driving motor, and an external power supply is adopted for supplying power to the driving motor;
the controller measures the voltage loaded on the electromagnetic wire frame through the I3 interface, and the torque loaded on the sample to be measured can be obtained according to the formula (5) by matching with the torque measuring mechanism.
A micro-scale material torsion testing method based on feedback tracking is based on the micro-scale material torsion testing device based on feedback tracking; the method comprises the following steps: firstly, the change of the rotation angle delta alpha of the lower clamp is controlled to be at an angle alpha by the cooperation of a data acquisition and control unit and a laser displacement sensor 0 Inside, angle alpha 0 Is 1% of the torsion angle to be measured, exceeds the angle alpha 0 The voltage of the electrified coil is increased, the lower end of the sample to be tested is guaranteed to be in a static state, and the rotating angle of the lower clamp is calculated through a calculation formula of a small included angle of the rotation of the lower clamp, namely a formula (5), so that the current in the electromagnetic wire frame is controlled;
then the upper end of the sample to be tested is fixed on the upper clamp and twisted along with the driving motor, the lower end of the sample to be tested is arranged on the lower clamp, the lower clamp does not rotate along with the sample to be tested, and the rotation included angle delta alpha of the lower clamp is ensured to be at an angle alpha 0 Inside, angle alpha 0 The torque of the to-be-measured torsion angle is 1%, namely the to-be-measured sample is in dynamic stress balance, the torque loaded on the to-be-measured sample is equal to the torque output by the driving motor to the upper end of the to-be-measured sample, at the moment, the lower clamp transmits the torque to the electromagnetic wire frame, the upper suspension assembly and the lower suspension assembly, and the torque generated on the electromagnetic wire frame is indirectly represented by the voltage U measured by the I3 interface of the controller according to the formula (3), namely T=K×U;
The lower clamp is controlled within a range of a slight angle delta alpha, and at this time, the upper suspension assembly and the lower suspension assembly deflect by a slight angle delta alpha, and the torsional rigidity of the upper suspension assembly and the lower suspension assembly is considered to be a fixed value K g Torque T borne by the upper and lower suspension assemblies g Torque T borne by electromagnetic wire frame and true torque T loaded on sample r Balance, namely:
T r ＝T+T g (6)；
T g ＝K g (G g ，D g ，l g )×△α (7)；
in the above formulae (6) to (7), G g 、D g 、l g Respectively the shear modulus, diameter, length, K of the materials used for the suspension system g Is with G g 、D g 、l g A function of the three variable correlations; after the upper suspension and the lower suspension are determined in terms of material and size, K g The size can be calibrated byThe method comprises the following specific calibration steps:
according to the size of a sample to be tested, adjusting the suspension length, assembling a micro-scale material torsion testing device based on feedback tracking, and powering off an electromagnetic wire frame; applying a micro force F on the lower clamp g ，F g The acting plane is perpendicular to the gravity direction, the acting point is arranged on the lower clamp and is at a distance L from the rotation center of the lower clamp g ，F g The magnitude of (2) is measured by a precision instrument and the torque applied to the lower clamp can be expressed as:
T g ＝F g ×l g (8)；
in synchronization, the rotation angle Δα of the lower clamp is measured by the laser displacement sensor, and the torsional rigidity of the upper suspension assembly and the lower suspension assembly is obtained according to the above formulas (7) - (8) as follows:
When the size of the suspension is changed or the material of the suspension is changed, the suspension should be re-treated with K g Calibrating;
the actual torque loaded on the sample to be tested is calculated according to the formulas (6) and (7), namely:
T r ＝T+K g ×△α (10)；
the resulting true twist angle theta on the test specimen r The difference between the torque theta measured by the angle sensor and the torsion angle delta alpha measured by the laser displacement sensor is that:
θ r ＝θ-△α (11)。
the feedback tracking-based micro-scale material torsion testing method comprises the following steps of: after the I3 interface of the controller receives the displacement signal of the laser displacement sensor, carrying out logic operation according to a calculation formula of a small included angle of the rotation of the lower clamp, namely formula (5)Calculating, obtaining the angle difference between two adjacent sampling points, namely delta alpha value, and judging whether the angle difference between two adjacent sampling points is at a fixed angle alpha 0 In the range, the power supply of the electromagnetic wire frame is regulated and controlled, and the closed-loop control of the torque is realized.
By adopting the technical scheme, the invention has the following beneficial effects:
the invention has 360-degree full-angle measurement range and friction-free feedback tracking, and in structural design, a fixed cross beam is not used from a torque output end to a region between torsion angle measurement and upper and lower clamp measurement, so that a sample can rotate in a full-angle and barrier-free manner, the small change of the rotation angle of the lower clamp is monitored by a non-contact measurement method (without influencing the measurement of the torque), and the torsion angle is measured by a hollow angle sensor, so that the full-angle measurement is realized.
The electromagnetic wire frame part is tensioned and fixed in a hanging mode, so that the influence of friction force caused by the traditional fixing modes such as a bearing, a center and the like is avoided. Meanwhile, the electromagnetic wire frame is of a bag-shaped structure, neutral is mainly considered, the original rectangular wire frame does not form a natural lowest point or highest point after being hung, the bag-shaped structure wire frame is designed with an arc shape, two arc tops are naturally positioned at the center position of the highest point and the lowest point after being hung, and the rotating center of the electromagnetic coil is ensured to be in the vertical direction.
The invention uses logic operation (namely formula (5) and figure 8) to carry out feedback tracking, and the lower clamp is kept in a micro rotation range by controlling the power supply of the controllable power supply on the coil, so that the clamping section at the lower end of the sample is ensured to be in a quasi-static state, and the sample is in a stress balance state.
According to the invention, through a calibration method, the overall rigidity of the suspension system is obtained, and the real torque loaded on the sample is obtained.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings which are required in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are some embodiments of the invention and that other drawings may be obtained from these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of the overall structure of a micro-scale material torsion testing device based on feedback tracking;
FIG. 2 is a schematic diagram showing a connection part between a lower suspension assembly and an electromagnetic wire frame of the micro-scale material torsion testing device based on feedback tracking;
FIG. 3 is a schematic diagram of the angle measurement (cross-sectional profile of the lower fixture) involved in the micro-scale material torsion testing apparatus based on feedback tracking of the present invention;
FIG. 4 is a schematic diagram of the data acquisition and control unit of the micro-scale material torsion testing device based on feedback tracking according to the present invention;
FIG. 5 is a schematic diagram of the installation of the upper and lower clamps and the test sample of the micro-scale material torsion testing device based on feedback tracking;
FIG. 6 is a schematic diagram of the original signals collected by the non-contact laser displacement sensor of the micro-scale material torsion testing device based on feedback tracking;
FIG. 7 is a diagram of the definition of the dimensions of the energized coils inside the magnet assembly involved in the microscale material-torsion testing apparatus based on feedback tracking of the present invention;
FIG. 8 is a schematic diagram of the logic operation process of the clamp changing in a small angle under the control of the micro-scale material torsion testing device based on feedback tracking.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention is further illustrated with reference to specific embodiments.
As shown in fig. 1-2, the micro-scale material torsion testing device based on feedback tracking provided in this embodiment includes a frame 1, a torque measuring mechanism 2, a driving and torsion angle measuring mechanism 3, and a data acquisition and control unit 4.
The frame 1 is a main body supporting portion including a bottom plate 11, a column 12, and a fixing plate 13.
The bottom plate 11 is a rectangular plate structure which is horizontally arranged, a pair of threaded holes are formed in the two ends of the bottom plate in a matched mode along the vertical direction, a plurality of threaded holes are formed in the middle of the bottom plate in a matched mode along the vertical direction, and support is provided for all parts of the testing machine.
The upright post 12 is provided with a pair of threaded holes which are respectively and vertically arranged at two ends of the bottom plate 11 in a matching manner; wherein each upright 12 is formed by connecting a lower upright 121, a middle upright 122 and an upper upright 123 from bottom to top end. The lower end of the lower upright post 121 is externally provided with external threads and is in matched connection with the threaded hole of the bottom plate 11 through the external threads, and the lower upright post 121 is provided with an internal threaded hole in an axial matched manner from the center of the end part of the upper end. The lower end of the middle upright post 122 is provided with external threads in a matching manner and is connected with an internal threaded hole at the upper end of the lower upright post 121 in a matching manner through the external threads, and the middle upright post 122 is provided with an internal threaded hole in a matching manner along the axial direction from the center of the end part of the upper end. The lower end of the upper upright post 123 is provided with external threads and is connected with an internal threaded hole at the upper end of the middle upright post 122 in a matched manner through the external threads, and the upper upright post 123 is provided with an internal threaded hole along the axial direction from the center of the end part of the upper end.
The fixing plate 13 is mounted on the middle section and the top end of the upright 12 in a matching manner, and comprises a first fixing plate 131, a second fixing plate 132 and a third fixing plate 133. The first fixing plate 131 is installed in the middle section of the upright post 12 in a matching manner, and two ends of the first fixing plate are provided with a pair of first installation holes in a matching manner along the vertical direction; the two ends of the first fixing plate 131 are fitted over the upper end of the center pillar 122 through the first mounting holes and are pressed and fixed between the lower end of the center pillar 122 and the upper end of the lower pillar 121. The second fixing plate 132 is also installed on the middle section of the upright 12 in a matching manner and is located above the first fixing plate 131; two ends of the second fixing plate 132 are provided with a pair of second mounting holes along the vertical direction in a matching manner; the two ends of the second fixing plate 132 are fitted over the upper end of the center pillar 122 through the second mounting holes and are pressed and fixed between the upper end of the center pillar 122 and the lower end of the upper pillar 123. The third fixing plate 133 is mounted on the top end of the upright post 12 in a matching manner, and a pair of third mounting holes are formed at two ends of the third fixing plate in a matching manner along the vertical direction; the two ends of the third fixing plate 133 are matched and sleeved at the upper end of the upper upright post 123 through a pair of third mounting holes, and are locked and fixed by mounting the fastening screw 14 into the inner screw hole at the upper end of the upper upright post 123. Meanwhile, the middle sections of the first fixing plate 131, the second fixing plate 132 and the third fixing plate 133 are provided with assembly holes for fixing other accessories of the testing device in a matching manner.
The torque measuring mechanism 2 is designed based on electromagnetic principles for measuring the torque loaded on the test specimen 5, and comprises an upper suspension assembly 21, a lower suspension assembly 22, an electromagnetic induction assembly 23 and a measuring assembly 24.
The upper suspension assembly 21 is matingly installed at the lower center of the third fixing plate 133 of the fixing plate 13 of the frame 1, and includes an upper moving platform 211, an upper fixing frame 212, an upper suspension 213, and a rectangular suspension 214. Wherein, the upper moving platform 211 is matingly fixed to the lower center of the third fixing plate 133, which has the X-direction and Y-direction adjusting functions. The upper fixing frame 212 is arranged on the upper moving platform 211 in a matching way in a threaded connection way, and the upper fixing frame 212 can move up and down in the Z direction through adjusting threads; and the side wall of the upper fixing frame 212 is provided with an upper threaded hole along the horizontal direction. The upper hanger 213 is a wire with a certain rigidity, and the upper end of the upper hanger penetrates into the upper fixing frame 212 and is fastened and fixed by an upper threaded hole and a screw. The rectangular suspension 214 is connected to the lower end of the upper suspension 213 in a matching manner, and is rigidly connected with the upper suspension 213 by welding, screw clamping, etc.
The lower suspension assembly 22 is matingly mounted to the upper center of the bottom plate 11 of the frame 1, and includes a lower moving platform 221, a lower fixing frame 222, a lower suspension 223, a cavity riding screw 224, a ball 225, and a nut 226. Wherein, the lower moving platform 221 is fixedly matched with the upper center of the bottom plate 11, and has the functions of adjusting the X direction and the Y direction. The lower fixing frame 222 is arranged on the lower moving platform 221 in a matching way in a threaded connection way, and the lower fixing frame 222 can move up and down in the Z direction by adjusting threads; the side wall of the lower fixing frame 222 is provided with a lower threaded hole along the horizontal direction. The lower hanger 223 is a wire having a certain rigidity, and its lower end is penetrated into the lower fixing frame 222 and fastened by a screw through a lower screw hole. The cavity saddle screw 224 is U-shaped and profiling saddle, the bottom of the saddle is sealed, the center is a cavity, and the bottom of the cavity is hemispherical; the cavity saddle screw 224 is matched with the upper end of the ball head 225 and is in point contact with the ball head 225, the cavity saddle screw 224 is provided with an external thread structure, and the contact point of the cavity saddle screw 224 and the ball head 225 is positioned at the hemispherical top point of the inner cavity of the cavity saddle screw 224. The ball 225 is a smooth solid sphere that is placed in a recess of the electromagnetic coil 232 of the electromagnetic induction assembly 23; the ball 225 is naturally located at the bottom center of the groove of the magnet wire frame 232 under the action of gravity and is in point contact with the magnet wire frame 232. The nut 226 is of an internal thread structure and is connected with the cavity saddle screw 224 through threads; after the nut 226 is fastened with the cavity saddle screw 224; the electromagnetic wire frame 232, the cavity at least screw 224, the ball 225 and the nut 226 are completely restrained, i.e. relative movement or rotation can not occur between the two.
The electromagnetic induction assembly 23 is matingly installed at the lower center of the first fixing plate 131 of the fixing plate 13 of the housing 1, and includes a magnet group 231 and an electromagnetic wire frame 232. The magnetic set 231 is fixed at the center of the lower part of the first fixing plate 131 of the rack 1 in a matching manner, and provides a uniform and stable magnetic field for the testing device. The electromagnetic wire frame 232 is a bag-shaped structure wire frame, and the bag-shaped structure wire frame is designed with an arc shape in consideration of the requirement on neutrality, and two arc tops are naturally positioned at the center position of the highest point and the lowest point after being hung, so that the rotating center of the electromagnetic coil is ensured to be in the vertical direction; the frame of the electromagnetic wire frame 232 is wound with a certain number of turns of wires and is suspended in the magnetic group 231; the length of the parallel sides of the magnet wire frame 232 in the magnetic field is L d The amperage generated by the energized coil cutting field is calculated according to ampere's law as follows:
F 0 ＝nBIL d (1)；
wherein in the above formula (1), n is the number of turns of the coil, B is the strength of the uniform magnetic field, I is the energizing current in the coil, L d For the length of the energized coil subjected to ampere force in the magnetic field, ampere force is generated for two sides of the energized coil opposite to each other, and the torque formed by a pair of ampere forces can be expressed as T:
wherein in the above formula (2), L a Is the coil width; according to the formula (2), the torque output by the coil, the number of turns n of the coil, the magnetic field intensity B, the power supply voltage U and the resistance R of the electrified coil can be seen 0 Coil size L a /L d Correlation; for a particular configuration, the number of turns n, the magnetic field strength B, and the coil size L a /L d Resistance R of energizing coil 0 Are all constant values. Therefore, the torque output through the energizing coil is positively correlated with the power supply voltage, and therefore, the magnitude of the torque T can be expressed as:
T＝K×U (3)；
wherein in the above formula (3), the size of K is obtained by a calibration method.
The measuring assembly 24 is fitted to the upper center of the first fixing plate 131 of the fixing plate 13 of the frame 1, and includes a laser displacement sensor 241 and a lower jig 242.
The laser displacement sensor 241 is installed on an upper portion of one side of the first fixing plate 131 in a matching manner; wherein the laser emission port of the laser displacement sensor 241 is directed toward the center of the first fixing plate 131 in the X negative direction.
The lower clamp 242 is cylindrical in shape, has a groove at its lower part and is located in the electromagnetic wire frame 232 of the electromagnetic induction assembly 23, and has an upper part located outside the electromagnetic wire frame 232 of the electromagnetic induction assembly 23; the lower clamp 242 is mounted by a threaded fit between the upper and lower portions and is secured across the magnet wire frame 232. Wherein the axis of the lower clamp 242 is coaxial with the rotation center of the magnet wire frame 232 and is not movable or rotatable relative to the magnet wire frame 232 Moving; the top end face of the lower clamp 242 is provided with a groove for clamping the bottom of the sample 5 to be tested. As shown in fig. 3, a part of the side walls of the lower clamp 242 are plane, the rest of the side walls are arc surfaces, and the whole lower clamp is D-shaped when seen from the cross section; the side wall plane of the lower jig 242 is used for reflecting the laser light emitted from the laser displacement sensor 241, and the laser displacement sensor 241 irradiates the X point of the side wall plane of the lower jig 242 with a measurement distance L s The axial line distance between the laser displacement sensor 241 and the lower clamp 242 is L 0 The method comprises the steps of carrying out a first treatment on the surface of the The radius of the arc surface of the lower clamp 242 is R, the minimum distance between the side wall plane of the lower clamp 242 and the axis is M, and the distance between the side wall plane of the lower clamp 242 and the axis is R; the angle between OM and OX is α, then α can be expressed as follows:
when the lower jig 242 is rotated to two different angles, the laser displacement sensors 241 respectively irradiate the X of the lower jig 242 1 、X 2 At the positions with the measuring distances of L respectively s1 、L s2 The small angle at which the lower clamp 242 rotates can be noted as:
the drive and torsion angle measuring mechanism 3 is mounted on a second fixing plate 132 of the fixing plate 13 of the frame 1, which includes a drive motor 31, an angle sensor 32, and an upper jig 33.
The driving motor 31 is used for providing power required by torsion of the sample 5 to be tested, and is matched and fixed at the upper center of the second fixing plate 132, and the power output shaft downwards passes through the second fixing plate 132.
The angle sensor 32 is a hollow sensor, and can measure 360 degrees of full angle range, and the main body part is fixed on the second fixing plate 132; the power output shaft of the driving motor 31 penetrates through the inside of the rotating shaft of the angle sensor 32 and is fixed by a screw, the power output shaft of the driving motor 31 and the rotating shaft of the angle sensor 32 can not rotate relatively, and the angle of the rotating shaft of the angle sensor 32 and the main body thereof rotating relatively is a measuring angle, namely the torsion angle of the driving motor 31.
The upper clamp 33 is used for clamping the sample 5 to be tested, and is matched with and installed on the power output shaft of the driving motor 31, and the upper clamp and the power output shaft are in threaded fit connection; the power output shaft of the driving motor 31 is an elongated shaft, which can also adjust the relative position between the upper clamp 33 and the driving motor 31 in the vertical direction by driving the upper clamp 33. The test specimen 5 is vertically held between the lower jig 242 and the upper jig 33. The upper end of the sample 5 naturally sags after being clamped on the upper suspension assembly 21, and the rotation axis is in the vertical direction; when the upper suspension assembly 21 and the lower suspension assembly 22 are tensioned, the rotation centers of the upper suspension assembly 21 and the lower suspension assembly 22 are also vertical, the central axis of the electromagnetic coil 232 is vertical, and the structure ensures that the torsion axis of the sample 5, the central axis of the electromagnetic coil 232 and the rotation center lines of the suspension assembly 21 and the lower suspension assembly 22 are coaxial.
As shown in fig. 4, the data acquisition and control unit 4 includes a computer 41 and a controller 42. The computer 41 is provided with control software and communicates with the controller 42 via a USB protocol. The controller 42 is integrated with hardware such as an acquisition card, a controllable direct current power supply, an I/O interface and the like; the controller 42 is electrically connected to the driving motor 31; the controller 42 is connected with the laser displacement sensor 241, the angle sensor 32 and the electromagnetic wire frame 232 through the I/O interface; the interfaces I1, I2 and I3 of the controller 42 are data collection ports, and are respectively used for high-frequency collection of signals of three channels of the laser displacement sensor 241, the angle sensor 32 and the electromagnetic wire frame 232; the O1 interface, the O2 interface and the O3 interface of the controller 42 are voltage signal output ports, wherein the O1 interface is used for supplying power to the electromagnetic wire frame 232, the O2 interface is used for supplying power to the angle sensor 32, and the O3 interface is used for supplying power to the driving motor 31; the driving motor 31 is powered by an external power source. The controller 42 measures the voltage applied to the magnet wire frame 232 via the I3 interface, and in conjunction with the torque measuring mechanism 2, can be used to meter the torque applied to the test sample 5 according to equation (5).
The invention relates to a micro-scale material torsion testing method based on feedback tracking, which is based on a micro-scale material torsion testing device based on feedback tracking, and specifically comprises the following steps:
In terms of measuring torque, the data acquisition and control unit 4 cooperates with the laser displacement sensor 241 to control the variation of the rotation angle Δα of the lower clamp 242 to a small angle α according to a certain operation logic (i.e., as shown in fig. 8 0 Within, alpha 0 The size of (a) is generally taken to be 1% of the torsion angle to be measured, exceeding this angle alpha 0 The voltage of the energizing coil is increased, and the coil is circularly reciprocated in this way, so as to ensure that the lower end of the sample 5 to be tested is in a static state, the rotating angle of the lower clamp 242 is calculated by the formula (5) to control the magnitude of the current in the electromagnetic wire frame 232, and the rotating angle delta alpha of the lower clamp 242 is ensured to be a tiny angle alpha 0 The lower clamp 242 does not rotate along with the sample 5 to be tested, i.e. the sample 5 to be tested is in a dynamic stress balance, and at this time, the lower clamp 242 transmits torque to the electromagnetic wire frame 232 and the upper and lower suspension assemblies 21 and 22, and the magnitude of the torque generated on the electromagnetic coil 232 is indirectly represented by the voltage U measured by the I3 interface of the controller 42 according to the formula (3).
The principle of ensuring Δα floating in a small range is as follows: after receiving the displacement signal of the laser displacement sensor 241, the I3 interface of the controller 42 performs a logic operation according to formula (5) to obtain an angle difference between two adjacent sampling points, i.e. a Δα value, by determining whether the angle difference between two adjacent sampling points is at a fixed angle α 0 In the range, the power supply of the electromagnetic wire frame 232 is regulated and controlled, and the closed-loop control of the torque is realized.
As shown in fig. 6-8, the control logic of the controller 42 is as follows:
in actual operation, considering the influence of noise level in the signal acquisition process, when the angle difference between two adjacent sampling points is carried out, the current moment is defined as T 0 By T 0 Tracing forward based on time of day, T -N -T 0 Average value of n+1 sampling points in period as L s2 Is used for calculating an input value; will T -2N -T -N Within a period of timeAverage value of n+1 sampling points as L s1 N is a natural number greater than or equal to 0, and in actual use, the size of N needs to be adjusted according to the noise level of the device.
The microscale torsion experiment technology has certain difficulty in measuring the real torque Tr loaded on the sample 5 to be tested, and the real torque loaded on the sample is expressed more accurately by carrying out suspension type structural design on the testing device and combining a mechanical model analysis method.
Specifically, according to the foregoing control method, during the torsion test, the lower clamp 242 is controlled to be within the range of the minute angle Δα, and at this time, the upper suspension member 21 and the lower suspension member 22 are deflected by a minute angle Δα, taking into account that the torsional rigidity of the upper suspension member 21 and the lower suspension member 22 is a fixed value K g Torque T borne by upper suspension assembly 21 and lower suspension assembly 22 g Torque T borne by the magnet wire frame 232 and true torque T applied to the test specimen r Balance, namely:
T r ＝T+T g (6)；
T g ＝K g (G g ，D g ，l g )×△α (7)；
wherein G in the above formulae (6) to (7) g 、D g 、l g Respectively the shear modulus, diameter, length, K of the materials used for the suspension system g Is with G g 、D g 、l g The function of these three variables, K, is determined after the upper 213 and lower 223 suspensions are made and sized g The size can be obtained by a calibration method, and the specific calibration method comprises the following steps:
the suspension length is adjusted according to the sample size and the torque measuring mechanism 2, the upper suspension assembly 21, the lower suspension assembly 22, the lower clamp 242, the laser displacement sensor 241, and the like of the test device are assembled, and the electromagnetic wire frame 232 is powered off. Applying a slight force F on lower clamp 242 g ，F g The plane of action is the direction perpendicular to the upper and lower suspension assemblies 21, 22 (i.e., perpendicular to the direction of gravity), whichThe action point is on the lower clamp 242 and is at a distance L from the rotation center of the lower clamp 242 g ，F g Can be measured by a micro force sensor; or by adding special tools, measuring by using precision instruments such as an electronic balance and the like; the torque applied to the lower clamp 242 may be expressed as:
T g ＝F g ×l g (8)；
in synchronization, the rotation angle Δα of the lower clamp 242 is measured by the laser displacement sensor 241, and then the torsional rigidity of the upper suspension assembly 21 and the lower suspension assembly 22 is obtained by the calibration method according to formulas (7) and (8) as follows:
When the size of the suspension is changed or the material of the suspension is changed, the suspension should be re-treated with K g And (5) calibrating.
The following describes an embodiment of the present invention with reference to the drawings, using 200 μm metallic glass fiber as a test sample 5.
A metallic glass fiber is installed at the position of the test specimen 5 in fig. 1, wherein the upper end of the metallic glass fiber is placed on the upper jig 33, and the fastening screw on the upper jig 33 is screwed.
The holding stage needs to adjust the position of the sample 5 to be measured, and is divided into two adaptive adjustment aspects of height and angle of the sample 5 to be measured. In the aspect of height adjustment, the lower ends of the metal glass fibers are firstly placed in the lower clamp 242, the upper moving platform 211 and the lower moving platform 221 are finely adjusted, the sample 5 to be measured is ensured to be positioned on the rotation center of the lower clamp 242, and the upper suspension 213 and the lower suspension 223 are ensured to be in a vertical state. If the lengths of the samples are different, the relative distances of the upper fixing frame 212, the lower fixing frame 222 and the upper clamp 33 can be adjusted under the condition that the length change is not large; if the difference in length of the test specimen 5 is extremely large, it is necessary to select a center pillar 122 that is more suitable in the length direction while adjusting the length of the rectangular suspension 214. In terms of angle adjustment, it is necessary to find the position of the lower jig 242 based on the laser signal emitted from the laser displacement sensor 241, and when the laser displacement sensor 241 is not irradiated on the AB surface shown in fig. 3, it is necessary to rotate the upper jig 33 and the lower jig 242 at the same time.
Adjusting the position of the laser displacement sensor 241 to ensure the distance L between the laser displacement sensor and the lower clamp 242 s Within the measurement range of the laser displacement sensor 241. The controller 42 is turned on, the data acquisition software in the control computer 41 is started, the electromagnetic wire frame 232 is sequentially started to supply power, the laser displacement sensor 241 is powered, and the angle sensor 32 is powered. After checking that the acquisition signal is normal, the driving motor 31 is started to set the loading process to rotate according to the torsion angle of a certain speed, as shown in fig. 5. The driving motor 31 rotates counterclockwise as shown in the drawing, and the upper clamping end of the metal glass fiber rotates along with the upper clamp 33; the lower clamp 242 receives a torque T (clockwise in this case) opposite to the rotation direction of the driving motor 31 by the electromagnetic wire frame 232, the lower clamp 242 maintains a quasi-stationary state, and the metallic glass fiber lower clamping end maintains a quasi-stationary state along with the lower clamp 242, and the test sample 5 to be tested is in a balanced state. And finally, stopping the experiment according to the damage condition of the sample 5 to be tested.
The controller 42 collects signals of the angle sensor 32, the laser displacement sensor 241 and the electromagnetic wire frame 232 in the whole process. The torsion angle measured by the angle sensor 32 is the sum of the torsion angle loaded on the sample 5 to be tested and the rotation angle of the suspension system; the displacement signal measured by the laser displacement sensor 241 is used for feedback tracking of the system, and the voltage U output loaded on the electromagnetic wire frame 232 is controlled.
The torque produced by the magnet wire frame 232 is calculated according to equation (3), i.e., t=k×u; the actual torque loaded on the test sample 5 is calculated according to formulas (6) and (7), namely:
T r ＝T+K g ×△α (10)；
the resulting true torsion angle theta on the test specimen 5 r The difference between the torque θ measured by the angle sensor 32 and the torsion angle Δα measured by the laser displacement sensor 241 is:
θ r ＝θ-△α (11)。
the invention has reasonable conception, can realize 360-degree full-angle measurement and frictionless feedback tracking, and is suitable for popularization and application.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (10)
1. The micro-scale material torsion testing device based on feedback tracking is characterized by comprising a data acquisition and control unit (4), a rack (1), a torque measuring mechanism (2) and a driving and torsion angle measuring mechanism (3) which are arranged on the rack (1) in a matching manner;
The torque measuring mechanism (2) is used for measuring the torque loaded on a sample to be measured and comprises an upper suspension assembly (21) which is matched and installed on the upper part of the frame (1), a lower suspension assembly (22) which is matched and installed on the lower part of the frame (1), and an electromagnetic induction assembly (23) and a measuring assembly (24) which are matched and installed on the middle part of the frame (1);
the driving and torsion angle measuring mechanism (3) is arranged in the middle of the frame (1) in a matching way; the sample (5) to be measured is clamped between the driving and torsion angle measuring mechanism (3) and the measuring assembly (24) in a matching way;
the data acquisition and control unit (4) is respectively and electrically connected with the electromagnetic induction assembly (23), the measurement assembly (24) and the driving and torsion angle measurement mechanism (3).
2. The feedback tracking based micro-scale material torsion testing device according to claim 1, wherein the upper suspension assembly (21) comprises an upper moving platform (211), an upper mount (212), an upper suspension (213) and a rectangular suspension (214); the upper moving platform (211) is fixedly matched with the upper part of the frame (1) and has the functions of adjusting in the X direction and the Y direction; the upper fixing frame (212) is arranged on the upper moving platform (211) in a matching way in a threaded connection mode, and the upper fixing frame (212) can be displaced upwards and downwards along Z by adjusting threads; the upper suspension (213) is a metal wire with certain rigidity, and the upper end of the upper suspension penetrates into the upper fixing frame (212) and is clamped and fixed by a screw; the rectangular suspension (214) is connected to the lower end of the upper suspension (213) in a matching manner, and is rigidly connected with the upper suspension (213).
3. The feedback tracking-based micro-scale material torsion testing device according to claim 1, wherein the lower suspension assembly (22) comprises a lower moving platform (221), a lower fixed frame (222), a lower suspension (223), a cavity saddle screw (224), a ball head (225) and a nut (226);
the lower moving platform (221) is fixed at the lower part of the frame in a matching way and has the functions of adjusting the X direction and the Y direction;
the lower fixing frame (222) is detachably arranged on the lower moving platform (221) in a matching way, and the lower fixing frame (222) can be vertically displaced along Z through adjusting threads;
the lower suspension (223) is a metal wire with certain rigidity, and the lower end of the lower suspension penetrates into the lower fixing frame (222) and is clamped and fixed by a screw;
the cavity horse riding screw (224) is profiled on the saddle, the bottom of the saddle is sealed, the center of the saddle is a cavity, and the bottom of the cavity is hemispherical;
the ball head (225) is a smooth solid ball which is placed in a groove of the electromagnetic coil (232); the ball head (225) is naturally positioned at the bottom center of the groove of the electromagnetic wire frame (232) under the action of gravity and is in point contact with the electromagnetic wire frame (232);
the cavity horse riding screw (224) is sleeved at the upper end of the ball head (225) in a matching way and is in point contact with the ball head (225), and the contact point of the cavity horse riding screw (224) and the ball head (225) is the hemispherical top point of the cavity horse riding screw (224);
The nut (226) is connected with the cavity saddle screw (224) in a threaded matching way.
4. The micro-scale material torsion testing device based on feedback tracking according to claim 1, wherein the electromagnetic induction assembly (23) comprises a magnet group (231) and an electromagnetic wire frame (232); the magnetic group (231) is matched and fixed in the middle of the rack (1) to provide a uniform and stable magnetic field for the testing device; the electromagnetic wire frame (232) is wound with a wire and is suspended in the magnetic group (231); the electromagnetic wire frame (232) is a bag-shaped structure wire frame; the length of the parallel side of the electromagnetic wire frame (232) positioned in the magnetic field is L d According to ampere's law, the ampere force calculation formula generated by the cutting magnetic field of the electrified coil is as follows:
F 0 ＝nBIL d (1)；
in the above formula (1), n is the number of turns of the coil, B is the strength of the uniform magnetic field, I is the energizing current in the coil, L d For the length of the energized coil subjected to ampere force in the magnetic field, ampere force is generated for two sides of the energized coil opposite to each other, and the torque formed by a pair of ampere forces can be expressed as T:
in the above formula (2), L a Is the coil width; the torque output by the coil, the number of turns n of the coil, the magnetic field intensity B, the power supply voltage U and the resistance R of the electrified coil can be obtained according to the formula (2) 0 Coil size L a /L d Correlation; number of turns n, magnetic field strength B, coil size L a /L d Resistance R of energizing coil 0 Are all determined constants; the torque output by the energized coil is positively correlated with the supply voltage, and its magnitude can be expressed as:
T＝K×U (3)；
in the above formula (3), the size of K is obtained by a calibrated method.
5. The feedback tracking based micro-scale material torsion testing device according to claim 4, wherein the measurement assembly (24) comprises a laser displacement sensor (241) and a lower clamp (242); the laser displacement sensor (241) is arranged in the middle of the frame (1) in a matching way, and a laser emission port faces to the X negative direction; the lower clamp (242) is integrally cylindrical, the lower part of the lower clamp is provided with a groove and is positioned in the electromagnetic wire frame (232), and the upper part of the lower clamp is positioned outside the electromagnetic wire frame (232); the upper part and the lower part of the lower clamp (242) are mounted through threaded fit and are fixed across the electromagnetic wire frame (232).
6. The micro-scale material torsion testing device based on feedback tracking according to claim 5, wherein the axis of the lower clamp (242) is coaxial with the rotation center of the electromagnetic wire frame (232) and is not movable or rotatable relative to the electromagnetic wire frame (232); the top end surface of the lower clamp (242) is provided with a groove for clamping a sample (5) to be tested;
One part of the side walls of the lower clamp (242) are plane, the other part of the side walls are arc surfaces, and the whole cross section of the lower clamp is of a D-shaped structure; the side wall plane of the lower clamp (242) is used for reflecting laser emitted by the laser displacement sensor (241); the laser displacement sensor (241) irradiates the X point of the side wall plane of the lower clamp (242) with a measuring distance L s The method comprises the steps of carrying out a first treatment on the surface of the The axial line distance between the laser displacement sensor (241) and the lower clamp (242) is L 0 The method comprises the steps of carrying out a first treatment on the surface of the The radius of the arc surface of the lower clamp (242) is R, the minimum distance between the side wall plane of the lower clamp (242) and the axis is M, and the distance between the side wall plane of the lower clamp (242) and the axis is R; the angle between OM and OX is α, then α can be expressed as follows:
when the lower clamp (242) rotates to two different angles, the laser displacement sensors (241) respectively irradiateX incident on the lower clamp (242) 1 、X 2 At the positions with the measuring distances of L respectively s1 、L s2 The calculation formula of the small included angle delta alpha of the rotation of the lower clamp (242) is as follows:
7. the feedback tracking based micro-scale material torsion testing device according to claim 6, wherein the drive and torsion angle measurement mechanism (3) is located above the measurement assembly (24) and comprises a drive motor (31), an angle sensor (32) and an upper clamp (33);
The driving motor (31) is used for providing power required by torsion of the sample (5) to be tested and is matched and fixed in the middle of the frame (1); the angle sensor (32) is a hollow sensor, can measure 360-degree full-angle range, and the main body part is fixed in the middle of the frame (1);
the power output shaft of the driving motor (31) penetrates through the inside of the rotating shaft of the angle sensor (32) and is fixed through a screw; the angle of the rotation axis of the angle sensor (32) relative to the main body part thereof is a measurement angle, that is, the angle of torsion of the driving motor (31);
the upper clamp (33) is matched with a power output shaft of the driving motor (31) and is in threaded fit connection with the power output shaft; a sample (5) to be measured is vertically held between the lower holder (242) and the upper holder (33).
8. The micro-scale material torsion testing device based on feedback tracking according to claim 7, wherein the data acquisition and control unit (4) comprises a computer (41) and a controller (42); the computer (41) and the controller (42) are communicated through a USB protocol; the controller (42) is respectively and electrically connected with the laser displacement sensor (241), the angle sensor (32), the electromagnetic wire frame (232) and the driving motor (31) through an I/O interface;
The I/O interface comprises an I1 interface, an I2 interface, an I3 interface, an O1 interface, an O2 interface and an O3 interface; the I1 interface, the I2 interface and the I3 interface are data acquisition ports and are respectively used for high-frequency acquisition of signals of the three channels of the laser displacement sensor (241), the angle sensor (32) and the electromagnetic wire frame (232); the O1 interface, the O2 interface and the O3 interface are voltage signal output ports; the O1 interface is used for supplying power to the electromagnetic wire frame (232); the O2 interface is used for supplying power to the angle sensor (32); the O3 interface is used for supplying power to the driving motor (31), and an external power supply is adopted for supplying power to the driving motor (31);
the controller (42) measures the voltage loaded on the electromagnetic wire frame (232) through the I3 interface, and is matched with the torque measuring mechanism (2), so that the torque loaded on the sample (5) to be measured can be obtained according to the formula (5).
9. A method for testing torsion of a microscale material based on feedback tracking, based on the microscale material torsion testing device according to any one of claims 1 to 8; the method is characterized in that: first, the change of the rotation angle delta alpha of the lower clamp (242) is controlled to be an angle alpha by the cooperation of the data acquisition and control unit (4) and the laser displacement sensor (241) 0 Inside, angle alpha 0 Is 1% of the torsion angle to be measured, exceeds the angle alpha 0 The voltage of the electrified coil is increased, and the current is circularly reciprocated in such a way that the lower end of the sample (5) to be tested is in a static state, and the rotating angle of the lower clamp (242) is calculated through a calculation formula of a small rotating included angle of the lower clamp (242), namely, a formula (5), so as to control the current in the electromagnetic wire frame (232);
then the upper end of the sample (5) to be tested is fixed on the upper clamp (33) and is twisted along with the driving motor (31), the lower end of the sample (5) to be tested is arranged on the lower clamp (242), the lower clamp (242) does not rotate along with the sample (5) to be tested, and the rotation included angle delta alpha of the lower clamp (242) is ensured to be at an angle alpha 0 Inside, angle alpha 0 Is 1% of the torsion angle to be measured, i.e. the test specimen (5) is in a dynamic stress balance, the torque applied to the test specimen (5) is equal to the driving powerThe machine (31) outputs torque to the upper end of the sample (5) to be tested, at the moment, the lower clamp (242) transmits the torque to the electromagnetic wire frame (232), the upper suspension assembly (21) and the lower suspension assembly (22), and the torque generated on the electromagnetic coil (232) is indirectly represented by the voltage U measured by the I3 interface of the controller (42) according to the formula (3), namely T=KXU;
the lower clamp (242) is controlled within a range of a slight angle delta alpha, at which time the upper suspension assembly (21) and the lower suspension assembly (22) deflect by a slight angle delta alpha, taking into account that the torsional stiffness of the upper suspension assembly (21) and the lower suspension assembly (22) is a fixed value K g The torque T borne by the upper suspension assembly (21) and the lower suspension assembly (22) g Torque T borne by the electromagnetic wire frame (232) and true torque T loaded on the sample r Balance, namely:
T r ＝T+T g (6)；
T g ＝K g (G g ，D g ，l g )×△α (7)；
in the above formulae (6) to (7), G g 、D g 、l g Respectively the shear modulus, diameter, length, K of the materials used for the suspension system g Is with G g 、D g 、l g A function of the three variable correlations; after the materials and the sizes of the upper suspension (213) and the lower suspension (223) are determined, K g The size can be obtained by a calibration method, and the specific calibration method comprises the following steps:
according to the size of a sample (5) to be tested, adjusting the suspension length, assembling a microscale material torsion testing device based on feedback tracking, and powering off an electromagnetic wire frame (232); applying a micro force F on the lower clamp (242) g ，F g The acting plane is perpendicular to the gravity direction, and the acting point is arranged on the lower clamp (242) and is at a distance L from the rotation center of the lower clamp (242) g ，F g The magnitude of (a) is measured by a precision instrument and the torque applied to the lower clamp (242) can be expressed as:
T g ＝F g ×l g (8)；
in synchronism, the angle Δα of rotation of the lower jig (242) is measured by the laser displacement sensor (241), and the torsional rigidity of the upper suspension assembly (21) and the lower suspension assembly (22) is obtained according to the above formulas (7) - (8) as follows:
when the size of the suspension is changed or the material of the suspension is changed, the suspension should be re-treated with K g Calibrating;
the actual torque loaded on the sample (5) to be tested is calculated according to the formulas (6) and (7), namely:
T r ＝T+K g ×△α (10)；
the resulting true torsion angle theta on the test specimen (5) r The difference between the torque θ measured by the angle sensor (32) and the torsion angle Δα measured by the laser displacement sensor (241), namely:
θ r ＝θ-△α (11)。
10. the feedback tracking-based micro-scale material torsion testing method according to claim 9, wherein the principle of ensuring Δα to float in a micro range is as follows: after the I3 interface of the controller (42) receives the displacement signal of the laser displacement sensor (241), logic operation is carried out according to a calculation formula of a tiny included angle rotated by the lower clamp (242), namely formula (5), so as to obtain an angle difference between two adjacent sampling points, namely delta alpha value, and whether the angle difference between the two adjacent sampling points is at a fixed angle alpha is judged 0 In the range, the power supply of the electromagnetic wire frame (232) is regulated and controlled, and the closed-loop control of the torque is realized.
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