Nanoindentation loading device with adjustable indentation head posture and adjusting method of nanoindentation loading device

Abstract

The invention relates to a nanoindentation loading device with an adjustable pressure head posture and an adjusting method of the nanoindentation loading device, and belongs to the field of precision machinery and instruments. The device mainly comprises a base, a fixed platform, a three-axis parallel loading unit, a movable platform, a pressure head and an x-y moving platform. Wherein the three-axis parallel loading unit is formed by three groups of flexible driving mechanisms which are symmetrically distributed at an interval of 120 degrees by taking the center of the fixed platform as an axis, the movable platform is arranged below the three-axis parallel loading unit, and the pressure head is arranged at the lower end of the movable platform. When the output displacements of the three groups of flexible driving mechanisms are equal, the pressure head can realize vertical loading along the negative z direction; and when the three groups of output displacements are different, the angle deflection of the pressure head can be realized. The device has the advantages that through the three groups of flexible driving mechanisms which are connected in parallel, the active adjustment of the pressing angle of the pressing head is realized, the test error caused by the inclined installation of the pressing head during the nanoindentation test can be effectively improved, and meanwhile, the diversity of the nanoindentation device in micro-nano structure array processing is enhanced.

Description

Technical Field

[0001] The present invention relates to a nano-indentation loading device with adjustable indenter posture and an adjustment method thereof, and belongs to the field of precision machinery and instruments. The present invention solves the problem that the verticality of the indenter installation in the existing nano-indentation device is too dependent on the processing and assembly accuracy, and enhances the adaptability of the nano-indentation device to the working environment and the compatibility with the sample to be tested. At the same time, by adjusting the indenter's indentation angle, a residual indentation with controllable morphology can be obtained on the surface of the specimen, thereby improving the application value of the indentation device in the field of creating array-type micro-nano structures on the surface of materials. Background Art

[0002] The mechanical properties of materials at the micro-nano scale are important criteria for judging their service life. The "Medium- and Long-Term Plan for the Construction of National Major Science and Technology Infrastructure (2012-2030)" also points out that the focus of material science will be on material characterization and regulation, and experimental research on engineering materials. Among the many material mechanical property testing methods, nanoindentation testing has developed rapidly in recent years because it does not require separate sample preparation, has less damage to the material surface, and has a high test resolution. In nanoindentation testing, it is necessary to ensure that the indenter is vertically pressed into and out of the sample being tested. The tilt of the indenter will cause errors between the measured indentation hardness and elastic modulus and the true values. The connecting parts of the indenter inevitably have errors during processing, which makes it difficult to achieve vertical assembly of the indenter and over-rely on processing and experience compensation. To this end, based on a three-axis parallel loading unit, a nanoindentation loading device with adjustable indenter posture and its adjustment method are proposed. Through the coordinated control of three flexible drive units, the vertical indentation and deflection movements around the x-axis and y-axis of the indenter are realized. Furthermore, the combination of control signals can realize the pressing action of the indenter in various postures, thereby quantitatively compensating the assembly error of the nanoindentation device and enhancing its application value in the processing of surface micro-nanostructure arrays. Summary of the invention

[0003] In order to improve the adaptability of the nano-indentation device to the working environment, reduce the dependence on its processing and assembly accuracy, and realize the active adjustment of the indentation angle of the indenter, the present invention discloses a nano-indentation loading device with adjustable indenter posture and an adjustment method thereof.

[0004] The technical solution adopted by the present invention to achieve the above-mentioned purpose is as follows: a nano-indentation loading device with adjustable indenter posture, characterized in that it includes a base, a fixed platform, a three-axis parallel loading unit, a moving platform, an indenter and an xy moving platform, and the fixed platform, the three-axis parallel loading unit, the moving platform, the indenter and the xy moving platform are sequentially distributed between the bases along the negative z-axis direction in the order of the fixed platform, the three-axis parallel loading unit, the moving platform, the indenter and the xy moving platform, wherein the fixed platform and the xy moving platform are respectively fixedly mounted on the upper and lower ends of the base; the fixed platform and the moving platform are concentrically arranged; the three-axis parallel loading unit includes a compliant drive mechanism I, a compliant drive mechanism II, and a compliant drive mechanism III, which are sequentially distributed in the counterclockwise direction starting from the positive x-axis direction, and the central axis of the fixed platform and the moving platform is used as the rotation axis. The center of symmetry is rotationally symmetrical with a spacing angle of 120°; the compliant drive mechanism I includes a connecting plate I, a compliant mechanism I, a pre-tightening screw I, a piezoelectric stack I, a cushion block I, and a ball hinge I, wherein the planar rotating hinge in the connecting plate I is used to connect the compliant drive mechanism I to the fixed platform and provide one rotational degree of freedom; the ball hinge I is used to connect the compliant drive mechanism I to the moving platform and provide three rotational degrees of freedom; the piezoelectric stack I is embedded in the compliant mechanism I through the cushion block I in an interference fit manner, and the pre-tightening state is further adjusted by the pre-tightening screw I; the compliant drive mechanism II and the compliant drive mechanism III have the same structure and connection method as the compliant drive mechanism I; the pressure head is coaxially installed at the lower end of the moving platform along the normal direction.

[0005] Another object of the present invention is to provide a method for adjusting a nanoindentation loading device with an adjustable indenter posture, comprising the following steps:

[0006] ① In the calibration stage, the piezoelectric stack I is embedded in the compliance mechanism I through the spacer I in an interference fit manner, the connection end of the compliance mechanism I is fixed, and driving signals of different voltages are input to the piezoelectric stack I. The elongation displacement of its output end is measured by the displacement sensor to obtain the linear correspondence between the input voltage and the output displacement of the compliance drive mechanism I; the compliance drive mechanism II and the compliance drive mechanism III are installed and tested by the same method, and the pre-tightening screws of the two are adjusted to change the pre-tightening state of the piezoelectric stack until the two can output completely consistent displacement with the compliance drive mechanism I under the same voltage excitation;

[0007] ② In the preparation stage, all components of the device are installed according to the structural relationship, the specimen is fixed on the xy moving platform with paraffin, and the xy moving platform is adjusted so that the center of the specimen is directly below the pressure head;

[0008] ③Vertical loading movement, three trapezoidal signals with the same voltage amplitude are applied to the three-axis parallel loading unit, that is, the input voltage amplitude U1 of the compliant drive mechanism I = the input voltage amplitude U2 of the compliant drive mechanism II = the input voltage amplitude U3 of the compliant drive mechanism III; when the voltage rises slowly, the three compliant drive mechanisms all slowly extend, and after debugging and calibration, the output components of the three in the xoy plane can offset each other, and only the output components along the negative z-axis direction are retained. The moving platform moves along the negative z-axis direction under the drive of the three-axis parallel loading unit, and the pressure head is vertically pressed into the surface of the specimen; then, the input voltage remains unchanged, the three-axis parallel loading unit remains stationary, and the pressure head is in a load-holding state; finally, the voltage drops slowly, the three-axis parallel loading unit and the moving platform slowly return to the initial state, and the pressure head slowly withdraws vertically from the surface of the specimen;

[0009] ④ Deflection movement around the x-axis, applying two trapezoidal signals with different voltage amplitudes to the three-axis parallel loading unit, satisfying 2U1=U 2, U3=0; when the voltage rises slowly, the compliant drive mechanism I and the compliant drive mechanism II slowly extend at different strain rates, and the output components of the two along the x-axis direction in the xoy plane can be offset in real time, and only the output components along the positive y-axis direction are retained, so the moving platform and the pressure head produce deflection motion around the x-axis under the drive of the three-axis parallel loading unit; then, the voltage remains unchanged, and the moving platform and the pressure head remain stationary; finally, the voltage slowly decreases, and the three-axis parallel loading unit, the moving platform and the pressure head slowly return to their initial state;

[0010] ⑤ Deflection movement around the y-axis, apply two trapezoidal signals with the same voltage amplitude to the three-axis parallel loading unit, satisfying U2=U 3, U1=0; when the voltage rises slowly, the compliant drive mechanism I and the compliant drive mechanism II slowly extend at the same strain rate, and the output components of the two along the y-axis direction in the xoy plane can be offset in real time, and only the output components along the positive x-axis direction are retained, so the moving platform and the pressure head produce deflection motion around the y-axis under the drive of the three-axis parallel loading unit; then, the voltage remains unchanged, and the moving platform and the pressure head remain stationary; finally, the voltage slowly decreases, and the three-axis parallel loading unit, the moving platform and the pressure head slowly return to their initial state;

[0011] ⑥ By combining the control signals in steps ③, ④, and ⑤, the loading action of the pressure head with different deflection postures can be realized.

[0012] The beneficial effect of the present invention is that the active adjustment of the indenter posture can be achieved through the control of the three-axis parallel loading unit, which is used to compensate for the installation error of the indenter during the assembly process of the nanoindentation device, thereby reducing the dependence on the vertical installation of the indenter. In addition, the various indentation postures of the indenter also give the nanoindentation device a broad application value in the field of micro-nano structure creation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings described herein are used to provide further understanding of the present invention and constitute a part of this application. The illustrative examples of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0014] Figure 1 It is a structural schematic diagram of a nano-indentation loading device with adjustable indenter posture according to the present invention;

[0015] Figure 2 is a top view of the three-axis parallel loading unit of the present invention;

[0016] Figure 3 is a schematic structural diagram of the compliant drive mechanism 1 of the present invention;

[0017] Figure 4 It is a schematic diagram of control signals and output forms for realizing vertical loading motion, deflection motion around the x-axis and deflection motion around the y-axis in the present invention;

[0018] Figure 5 This is one of the application cases of the present invention, but does not constitute an improper limitation of the present invention.

[0019] In the figure: 1. base; 2. fixed platform; 3. three-axis parallel loading unit; 3.1. compliant drive mechanism I; 3.1.1. connecting plate I; 3.1.2. compliant mechanism I; 3.1.3. pre-tightening screw I; 3.1.4. piezoelectric stack I; 3.1.5. pad I; 3.1.6. ball hinge I; 3.2. compliant drive mechanism II; 3.3. compliant drive mechanism III; 4. moving platform; 5. pressure head; 6. xy moving platform. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings in the examples.

[0021] See also Figures 1 to 3A nano-indentation loading device with adjustable indenter posture, characterized in that it comprises a base (1), a fixed platform (2), a three-axis parallel loading unit (3), a moving platform (4), an indenter (5) and an xy moving platform (6), and the fixed platform (2), the three-axis parallel loading unit (3), the moving platform (4), the indenter (5) and the xy moving platform (6) are sequentially distributed between the base (1) along the negative z-axis direction in the order of the fixed platform (2), the three-axis parallel loading unit (3), the moving platform (4), the indenter (5) and the xy moving platform (6), wherein the fixed platform (2) and the xy moving platform (6) are respectively fixedly mounted on the base ( 1); the fixed platform (2) and the moving platform (4) are arranged concentrically; the three-axis parallel loading unit (3) comprises a compliant drive mechanism I (3.1), a compliant drive mechanism II (3.2), and a compliant drive mechanism III (3.3), which are sequentially arranged in a counterclockwise direction starting from the positive x-axis direction, and are rotationally symmetrically arranged with a spacing angle of 120° with the central axis of the fixed platform (2) and the moving platform (4) as the rotational symmetry center; the compliant drive mechanism I (3.1), the compliant drive mechanism II (3.2), and the compliant drive mechanism III (3.3), which are arranged counterclockwise starting from the positive x-axis direction, and are rotationally symmetrically arranged with a spacing angle of 120° with the central axis of the fixed platform (2) and the moving platform (4) as the rotational symmetry center; the compliant drive mechanism I (3.3) 1) includes a connecting plate I (3.1.1), a compliant mechanism I (3.1.2), a pre-tightening screw I (3.1.3), a piezoelectric stack I (3.1.4), a pad I (3.1.5), and a ball hinge I (3.1.6), wherein the plane rotation hinge in the connecting plate I (3.1.1) is used to connect the compliant drive mechanism I (3.1) to the fixed platform (2) and provide a rotational freedom; the ball hinge I (3.1.6) is used to connect the compliant drive mechanism I (3.1) to the moving platform (4) connected and provide three rotational degrees of freedom; the piezoelectric stack I (3.1.4) is embedded in the compliance mechanism I (3.1.3) by means of interference fit through the spacer I (3.1.5), and the pre-tightening state is further adjusted by the pre-tightening screw I (3.1.3); the said compliance drive mechanism II (3.2) and the said compliance drive mechanism III (3.3) have the same structure and connection method as the said compliance drive mechanism I (3.1); the said pressure head (5) is coaxially installed on the lower end of the moving platform (4) along the normal direction.

[0022] See also Figure 4 , which is a method for adjusting a nano-indentation loading device with an adjustable indenter posture proposed by the present invention, and is characterized by comprising the following steps:

[0023] ① During the calibration phase, the piezoelectric stack I (3.1.5) is embedded in the compliance mechanism I (3.1.3) by means of interference fit through the spacer I (3.1.6), the connection end of the compliance mechanism I (3.1.3) is fixed, driving signals of different voltages are input to the piezoelectric stack I (3.1.5), and the elongation displacement at its output end is measured by the displacement sensor to obtain the linear correspondence between the input voltage and the output displacement of the compliance drive mechanism I (3.1); the compliance drive mechanism II (3.2) and the compliance drive mechanism III (3.3) are installed and tested by the same method, and the pre-tightening screws of the two are adjusted to change the pre-tightening state of the piezoelectric stack until, under the same voltage excitation, the two can output a displacement that is completely consistent with the output of the compliance drive mechanism I (3.1);

[0024] ② Preparation stage: All components of the device are installed according to the structural relationship, the test piece is fixed on the xy moving platform (6) by paraffin, and the xy moving platform (6) is adjusted until the center of the test piece is located directly below the pressure head (5);

[0025] ③ Vertical loading movement, three trapezoidal signals with the same voltage amplitude are applied to the three-axis parallel loading unit (3), that is, the input voltage amplitude U1 of the compliant driving mechanism I (3.1) = the input voltage amplitude U2 of the compliant driving mechanism II (3.2) = the input voltage amplitude U3 of the compliant driving mechanism III (3.3); when the voltage rises slowly, the three compliant driving mechanisms all slowly extend, and after debugging and calibration, the output components of the three in the xoy plane can offset each other, and only the output components along the negative z-axis direction are retained. The moving platform (4) moves along the negative z-axis direction under the drive of the three-axis parallel loading unit (3), and the pressure head (5) is vertically pressed into the surface of the specimen; then, the input voltage remains unchanged, the three-axis parallel loading unit (3) remains stationary, and the pressure head (5) is in a load-holding state; finally, the voltage drops slowly, the three-axis parallel loading unit (3) and the moving platform (4) slowly return to the initial state, and the pressure head (5) slowly withdraws vertically from the surface of the specimen;

[0026] ④ Deflection movement around the x-axis, applying two trapezoidal signals with different voltage amplitudes to the three-axis parallel loading unit (3), satisfying 2U1=U 2, U3=0; when the voltage rises slowly, the compliant drive mechanism I (3.1) and the compliant drive mechanism II (3.2) slowly extend at different strain rates, and the output components of the two along the x-axis direction in the xoy plane can be offset in real time, and only the output components along the positive y-axis direction are retained, so the moving platform (4) and the pressure head (5) generate deflection motion around the x-axis under the drive of the three-axis parallel loading unit (3); then, the voltage remains unchanged, and the moving platform (4) and the pressure head (5) remain stationary; finally, the voltage slowly decreases, and the three-axis parallel loading unit (3), the moving platform (4) and the pressure head (5) all slowly return to their initial state;

[0027] ⑤ Deflection movement around the y-axis, applying two trapezoidal signals with the same voltage amplitude to the three-axis parallel loading unit (3), satisfying U2 = U 3, U1=0; when the voltage rises slowly, the compliant drive mechanism I (3.1) and the compliant drive mechanism II (3.2) slowly extend at the same strain rate, and the output components of the two along the y-axis direction in the xoy plane can be offset in real time, and only the output components along the positive x-axis direction are retained, so the moving platform (4) and the pressure head (5) generate deflection motion around the y-axis under the drive of the three-axis parallel loading unit (3); then, the voltage remains unchanged, and the moving platform (4) and the pressure head (5) remain stationary; finally, the voltage slowly decreases, and the three-axis parallel loading unit (3), the moving platform (4) and the pressure head (5) all slowly return to their initial state;

[0028] ⑥ By combining the control signals in steps ③, ④ and ⑤, the loading action of the pressure head (5) with different deflection postures can be realized.

[0029] Figure 5 This is one of the application cases of the present invention. On the basis of the nanoindentation loading device proposed in the present invention, a force sensor and a displacement sensor can be integrated to measure the load and depth information during the indentation process, thereby realizing a quantitative nanoindentation test function.

[0030] The above content does not impose any formal limitation on the structure and shape of the present invention. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A nanoindentation loading device with adjustable indenter posture, characterized in that: The invention comprises a base (1), a fixed platform (2), a three-axis parallel loading unit (3), a moving platform (4), a pressure head (5) and an xy moving platform (6), and the fixed platform (2), the three-axis parallel loading unit (3), the moving platform (4), the pressure head (5) and the xy moving platform (6) are sequentially distributed on the base (1) along the negative z-axis direction in the order of the fixed platform (2), the three-axis parallel loading unit (3), the moving platform (4), the pressure head (5) and the xy moving platform (6), wherein the fixed platform (2) and the xy moving platform (6) are respectively fixedly mounted on the upper end and the lower end of the base (1); the fixed platform (2) and the xy moving platform (6) are respectively fixedly mounted on the upper end and the lower end of the base (1); The moving platform (4) is arranged concentrically; the three-axis parallel loading unit (3) comprises a compliant drive mechanism I (3.1), a compliant drive mechanism II (3.2), and a compliant drive mechanism III (3.3), which are sequentially arranged in a counterclockwise direction starting from the positive x-axis direction, and are rotationally symmetrically arranged with a spacing angle of 120° with the central axis of the fixed platform (2) and the moving platform (4) as the rotational symmetry center; the compliant drive mechanism I (3.1) comprises a connecting plate I (3.

1. 1), a compliant mechanism I (3.1.2), a pre-tightening screw I (3.1.3), a piezoelectric stack I (3.1.4), a spacer I (3.1.5), and a ball hinge I (3.1.6), wherein the plane rotation hinge in the connecting plate I (3.1.1) is used to connect the compliant drive mechanism I (3.1) to the fixed platform (2) and provide one degree of rotational freedom; the ball hinge I (3.1.6) is used to connect the compliant drive mechanism I (3.1) to the moving platform (4) and provide three degrees of freedom. The piezoelectric stack I (3.1.4) is embedded in the compliance mechanism I (3.1.3) by means of interference fit through a spacer block I (3.1.5), and the pre-tightening state is further adjusted by means of a pre-tightening screw I (3.1.3); the said compliance drive mechanism II (3.2) and the said compliance drive mechanism III (3.3) have the same structure and connection method as the said compliance drive mechanism I (3.1); the said pressure head (5) is coaxially mounted on the lower end of the moving platform (4) along the normal direction.

2. The adjustment method of the nanoindentation loading device with adjustable indenter posture according to claim 1, characterized in that: The following steps are involved: ① During the calibration phase, the piezoelectric stack I (3.1.5) is embedded in the compliance mechanism I (3.1.3) by means of interference fit through the spacer I (3.1.6), the connection end of the compliance mechanism I (3.1.3) is fixed, driving signals of different voltages are input to the piezoelectric stack I (3.1.5), and the elongation displacement at its output end is measured by the displacement sensor to obtain the linear correspondence between the input voltage and the output displacement of the compliance drive mechanism I (3.1); the compliance drive mechanism II (3.2) and the compliance drive mechanism III (3.3) are installed and tested by the same method, and the pre-tightening screws of the two are adjusted to change the pre-tightening state of the piezoelectric stack until, under the same voltage excitation, the two can output a displacement that is completely consistent with the output of the compliance drive mechanism I (3.1); ② Preparation stage: All components of the device are installed according to the structural relationship, the test piece is fixed on the xy moving platform (6) by paraffin, and the xy moving platform (6) is adjusted until the center of the test piece is located directly below the pressure head (5); ③ Vertical loading movement, three trapezoidal signals with the same voltage amplitude are applied to the three-axis parallel loading unit (3), that is, the input voltage amplitude U1 of the compliant drive mechanism I (3.1) = the input voltage amplitude U2 of the compliant drive mechanism II (3.2) = the input voltage amplitude U3 of the compliant drive mechanism III (3.3); when the voltage rises slowly, the three compliant drive mechanisms all slowly extend, and after debugging and calibration, the output components of the three in the xoy plane can offset each other, and only the output components along the negative z-axis direction are retained. The moving platform (4) moves along the negative z-axis direction under the drive of the three-axis parallel loading unit (3), and the pressure head (5) is vertically pressed into the surface of the specimen; then, the input voltage remains unchanged, the three-axis parallel loading unit (3) remains stationary, and the pressure head (5) is in a load-holding state; finally, the voltage slowly decreases, the three-axis parallel loading unit (3) and the moving platform (4) slowly return to the initial state, and the pressure head (5) slowly withdraws vertically from the surface of the specimen; ④ Deflection movement around the x-axis, applying two trapezoidal signals with different voltage amplitudes to the three-axis parallel loading unit (3), satisfying 2U1=U 2, U3=0; when the voltage rises slowly, the compliant drive mechanism I (3.1) and the compliant drive mechanism II (3.2) slowly extend at different strain rates, and the output components of the two along the x-axis direction in the xoy plane can be offset in real time, and only the output components along the positive y-axis direction are retained, so the moving platform (4) and the pressure head (5) generate deflection motion around the x-axis under the drive of the three-axis parallel loading unit (3); then, the voltage remains unchanged, and the moving platform (4) and the pressure head (5) remain stationary; finally, the voltage slowly decreases, and the three-axis parallel loading unit (3), the moving platform (4) and the pressure head (5) all slowly return to their initial state; ⑤ Deflection movement around the y-axis, applying two trapezoidal signals with the same voltage amplitude to the three-axis parallel loading unit (3), satisfying U2 = U 3, U1=0; when the voltage rises slowly, the compliant drive mechanism I (3.1) and the compliant drive mechanism II (3.2) slowly extend at the same strain rate, and the output components of the two along the y-axis direction in the xoy plane can be offset in real time, and only the output components along the positive x-axis direction are retained, so the moving platform (4) and the pressure head (5) generate deflection motion around the y-axis under the drive of the three-axis parallel loading unit (3); then, the voltage remains unchanged, and the moving platform (4) and the pressure head (5) remain stationary; finally, the voltage slowly decreases, and the three-axis parallel loading unit (3), the moving platform (4) and the pressure head (5) all slowly return to their initial state; ⑥ By combining the control signals in steps ③, ④ and ⑤, the loading action of the pressure head (5) with different deflection postures can be realized.

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