CN1945266A - Double shaft force electric coupling loading driving and charge detecting device - Google Patents

Abstract

A biaxial electromechanical coupling loading transmission and charge measuring device relates to a electromechanical coupling loading and measuring system for applying electric loading and bidirectional force loading to piezoelectric ferroelectric materials. The present invention adopts a double-axis self-adjusting force transmission shaft including a fixed loading shaft and a self-adjusting spherical hinge loading shaft, a sealing device and a charge measuring instrument matched therewith, which can simultaneously load in the horizontal direction and the vertical direction respectively, and utilize self-adjusting The self-adjusting function of the spherical hinge loading shaft ensures the synchronization and self-adjusting centering of the axial pressure, which improves the loading accuracy; through the design of the sealing device, the insulation system is guaranteed to be loaded without friction The silicone oil medium will not leak; the charge measuring instrument made of parallel protection diodes, signal amplifiers and output regulators is integrated in the measuring circuit to improve the measurement accuracy and realize the overvoltage protection function of the system at the same time. The invention has the characteristics of miniaturization, simple and convenient processing, high precision and easy realization.

Description

A dual-axis electromechanical coupling loading transmission and charge measurement device

technical field

The invention relates to an experimental device, in particular to a electromechanical coupling loading and measuring system for applying electric loading and bidirectional force loading to piezoelectric ferroelectric materials, and belongs to the technical fields of engineering materials, physical properties, structural deformation and mechanical experiments.

Background technique

For anisotropic materials, the general unidirectional tensile test can no longer truly reflect the physical and mechanical properties of the material. It is necessary to study the mechanical behavior of the material when it is subjected to a load field in two directions perpendicular to each other. For piezoelectric ferroelectric For smart materials, it is necessary to study their material behavior under electromechanical coupling loading, which is of great significance for the application of materials and the development of new materials.

However, the current biaxial testing machine, such as the vertical biaxial four-cylinder electro-hydraulic servo testing machine (application number: 200610012089.9), can complete the biaxial mechanical behavior of anisotropic materials, but for the electromechanical coupling of piezoelectric ferroelectric materials However, there are problems of accuracy and safety in performance research. In addition, the research on electromechanical coupling of piezoelectric ferroelectric materials is limited to electrical loading and uniaxial compressive stress loading. Li Changqing (Experimental research on constitutive behavior and electrical fatigue of ferroelectric materials .[Master's Degree Thesis of Tsinghua University], Beijing: Department of Engineering Mechanics, Tsinghua University, 1998) designed a single-axis loading device through a guide frame to keep the compression bar perpendicular to the specimen. This method is relatively simple, but because it does not have the function of automatic adjustment, it cannot accurately guarantee the pure compression state of the specimen, which is particularly important in pure compression experiments, especially bidirectional stress field experiments. In addition, because the experiment needs to be loaded with electric load, in order to avoid the discharge of the charge to the air under the high-voltage electric field, the experiment should be carried out in silicone oil, but in Li Changqing's paper, only one oil tank can meet the requirements, and in the biaxial experiment. The sealing of the silicone oil needs to be considered to avoid excessive silicone oil flowing out and high voltage discharge during the loading process. Thirdly, in order to avoid the damage caused by the collision of the testing machine when the specimen is damaged during biaxial loading, the testing machine must adopt the displacement control loading method, and the deformation of the piezoelectric ferroelectric material is still small under a large stress load, which makes The accuracy of displacement-controlled loading is difficult to guarantee. So it is necessary to avoid this loading method of directly loading the material.

The traditional Sawyer-Tower loop is generally used in the charge measurement system on the surface of the specimen. Since the current data are collected by data acquisition cards or low-voltage precision instruments, once the test piece is broken down during the experiment, a momentary high voltage will be generated in the measurement system circuit, which will inevitably damage the precision instruments of the measurement system. Therefore, overvoltage protection measures must be designed in the measurement circuit to ensure the safety of the acquisition instrument.

Contents of the invention

The purpose of the present invention is to provide a biaxial electromechanical coupling loading transmission and charge measuring device, which uses a biaxial self-adjusting transmission device to realize biaxial electromechanical coupling loading on ferroelectric ceramics by a biaxial self-adjusting transmission device, ensuring biaxial force synchronization and self-adjusting neutrality.

Another object of the present invention is to design a set of insulating device matched with the biaxial self-adjusting transmission device, so that the experiment can be carried out in silicone oil, avoiding high-voltage discharge and electric charge loss.

Another object of the present invention is to connect a set of overvoltage protection and charge error compensation components in parallel in the charge measurement circuit, and integrate them into a charge measurement instrument to realize the accuracy of charge measurement, real-time monitoring and safety after electric field overload.

Technical scheme of the present invention is as follows:

A biaxial force-electric coupling loading transmission and charge measurement device, comprising a biaxial force loading transmission device and a charge measurement device, characterized in that: the biaxial force loading transmission device adopts a biaxial self-adjusting transmission shaft, and the described The two-axis self-adjusting transmission shaft includes a set of fixed transmission shafts and a set of self-adjusting spherical hinge transmission shafts in the horizontal and vertical directions; the fixed transmission shaft includes sequentially connected insulating blocks, fixed trapezoidal pressure heads, and fixed connecting rods and a fixed transfer rod connected with the biaxial loading testing machine fixture; the self-adjusting spherical hinge drive shaft includes an insulating block, adjusting trapezoidal indenter, adjusting steel ball, connecting spring, adjusting connecting rod and biaxial loading testing machine fixture Connected adjustment adapter rod; one end of the adjustment trapezoidal indenter is matched with the adjustment connecting rod through the adjustment steel ball, and is movably connected through the connection spring, the other end of the adjustment trapezoidal indenter is connected with the insulating block, and one end of the adjustment transfer rod It is flexibly connected with the adjusting connecting rod, and the other end is connected with the fixture of the biaxial loading testing machine.

Another technical feature of the present invention is: the device also includes an insulating device matched with the biaxial self-adjusting transmission shaft, the insulating device includes a loading oil tank and a follower oil tank arranged outside the loading oil tank, in the loading oil tank A frictionless sealing device is provided between the fixed transmission shaft in the horizontal direction and the spherical hinge transmission shaft, and sealing plugs are respectively provided between the loading oil tank and the follower oil tank and the fixed transmission shaft in the vertical direction.

On the basis of the above solution, the preferred solution of the present invention is: the frictionless sealing device includes an insulating compression ring, an annular flexible oil-proof layer sandwiched between the insulating compression ring and the oil loading groove, and an insulating compression nut.

The technical feature of the present invention is also that: described electric charge measuring device comprises electric charge measuring instrument and A/D data acquisition device, and described electric charge measuring instrument comprises protection diode, signal amplifier and is connected at the signal amplifier output end to measure electric charge error. Compensation for output regulation and LCD display for monitoring the output signal.

Compared with the prior art, the present invention has the following advantages and outstanding effects: the present invention adopts a biaxial self-adjusting transmission shaft, which ensures the real-time self-adjusting centering of biaxial force loading; according to the large deformation characteristics of the steel transmission shaft Realized the force loading of the large load testing machine for the displacement control of small pieces of ceramics; designed a set of insulation devices that cooperate with the biaxial self-adjusting transmission shaft, and realized that the horizontal transmission device and the sample were completely immersed in the insulating silicone oil in the high-voltage electric field loading experiment. experiment, thereby avoiding the phenomenon of high voltage discharge due to the outflow of too much silicone oil during the loading process; at the same time, the accuracy of biaxial force loading in the experiment is guaranteed by the frictionless sealing device; another advantage of the present invention is that it improves the traditional The unique Sawyer-Tower charge measurement circuit can avoid damage to the measurement and data acquisition instruments due to electrical overload in the experiment, and can compensate for the error of the charge measurement result, and has real-time monitoring.

Description of drawings

Fig. 1 is a schematic structural diagram of a biaxial electromechanical coupling loading transmission and charge measuring device provided by the present invention.

Fig. 2 is a schematic diagram of a self-adjusting spherical hinge drive shaft.

Figure 3 is a schematic diagram of the frictionless sealing device designed in the experiment.

Figure 4 is a schematic diagram of the charge measurement circuit.

In the figure: 1-fixed drive shaft; 2-self-adjusting spherical hinge drive shaft; 3-frictionless sealing device; 4-loading oil tank; 5-sealing plug; 6-following oil tank; 7-fixed connecting rod; 8-fixed Adapter rod; 9-adjusting trapezoidal pressure head; 10-adjusting connecting rod; 11-adjusting connecting rod; 12-adjusting steel ball; 13-connecting spring; 14-through groove; 15-screw hole; Annular flexible oil-proof layer; 18-compression screw; 19-insulation pressure ring; 20-insulation compression nut; 21-insulation block; 22-connecting rod thread; 23-protection diode; 24-signal amplifier; 25-output adjustment; 26-fixed trapezoidal indenter; 27-charge measuring instrument; 28-high voltage input.

Detailed ways

Principle of the present invention, concrete structure and working process are further described below in conjunction with accompanying drawing:

Fig. 1 is a schematic structural diagram of a biaxial electromechanical coupling loading transmission and charge measuring device provided by the present invention. Contains a biaxial force-loaded transmission device, a high-voltage input 28 and a charge measuring instrument 27; the biaxial force-loaded transmission device includes a biaxial self-adjusting transmission shaft and a set of insulating devices matched therewith. The two-axis self-adjusting power transmission shaft includes a set of fixed transmission shaft 1 and a set of self-adjusting spherical hinge transmission shaft 2 in the horizontal and vertical directions; the fixed transmission shaft 1 includes an insulating block 21, a fixed trapezoidal pressure Head 26, threaded fixed connecting rod 7 and fixed adapter rod 8; the fixed transmission shaft adopts high-precision machining, and the non-loading end of the fixed trapezoidal pressure head 26 is connected with the cylindrical fixed connecting rod 7; the fixed connecting rod 7 and The cylindrical fixed adapter rod 8 cooperates with the thread 16, so that the two axial directions of the whole set of loading transmission shafts have a fixed and centered transmission shaft respectively, and at the same time, it can be conveniently loaded and unloaded on the insulating device of the experiment. Fig. 2 is a schematic diagram of a self-adjusting spherical hinge transmission shaft, including an insulating block 21, an adjusting trapezoidal pressure head 9, an adjusting steel ball 12, a connecting spring 13 and an adjusting connecting rod 10; The adjustment adapter rod 11 is relatively compressed and connected by the compression screw 18; the other end of the adjustment connecting rod 10 and one end of the adjustment trapezoidal indenter 9 are respectively processed with conical grooves of the same size, and the four adjustment springs 13 are respectively fixed by small screws Around the cylindrical adjusting connecting rod 11 and adjusting trapezoidal pressing head 9, the adjusting connecting rod 11 and adjusting trapezoidal pressing head 9 are movably connected together by adjusting steel ball 12 and four connecting springs 13 . When the axial pressure is loaded, the adjusting steel ball 12 is in smooth contact with the conical groove of the adjusting trapezoidal indenter 9. Due to the scalability of the connecting spring, the adjusting trapezoidal indenter and the adjusting connecting rod can be relatively freely rotated, while the connecting spring 13 The connection also makes the adjustment trapezoidal pressure head 9 and the adjustment connecting rod 10 not disengage simultaneously. The other end of the adjusting connecting rod 10 is connected with the rectangular toothless fixture of the testing machine through the rectangular adjusting connecting rod 11 to realize the dynamic self-adjusting function, which not only ensures the self-adjusting function but also makes it easy to install and disassemble when connecting with the insulating device . In the biaxial electromechanical coupling constitutive experiment, the adjusting connecting rod 10 and the adjusting connecting rod 11 are movably connected through the rectangular through-slot 14 on the adjusting connecting rod, so that there is no restriction on the direction of rotation or it can be Disassembly becomes easy. The main purpose of this part is to ensure a certain degree of freedom of rotation when the force of the adjustment adapter rod 11 is applied to the adjustment connecting rod 10. It can also be designed as other free connections, such as hinge connections, but it is more cumbersome in terms of loading and unloading. Regardless of the fixed transmission shaft or the self-adjusting spherical hinge transmission shaft, the indenter of the loading sample is designed with a trapezoidal head. Shaft processing and assembly is convenient. The insulating block 21 and the solid insulating patches (about 2 mm in thickness) outside the surfaces of the trapezoidal indenters not shown in the figure are all designed for the insulation requirements in the experiment. The insulating block 21 at the top of the indenter is made of aluminum oxide material with a certain thickness that is highly resistant to voltage and highly insulating. Because alumina is very hard and difficult to process, an insulating material that is easy to process is selected on the sides of the fixed trapezoidal indenter 26 and the adjustable trapezoidal indenter 9 that do not require pressure. For sample connections with electrodes, the distance between the exposed copper sheet and the metal transmission shaft cannot be guaranteed to be large enough, and discharge may occur even in silicone oil, so it is necessary to paste easy-to-process PTFE stickers on the sides of the four trapezoidal metal indenters. sheet as a solid insulating patch. Each solid insulating block is bonded with the fixed trapezoidal indenter 26 and the adjustable trapezoidal indenter 9 by insulating glue.

The two-axis self-adjusting power transmission shaft is equipped with a set of insulating device, which includes a loading oil tank 4 and a follower oil tank 6 arranged outside the loading oil tank, and the loading oil tank 4 is connected with the fixed connecting rod 7 in the horizontal direction and the adjustment A frictionless sealing device 3 is arranged between the connecting rods 10 , and sealing plugs 5 are respectively arranged between the loading oil groove 4 and the follower oil groove 6 and the fixed transmission shaft in the vertical direction. This set of insulating devices is designed for the loading of the electric field high-voltage input 28 in the electromechanical coupling experiment. The high-voltage input 28 includes a signal generator and a signal amplifier (Trek 20/30), which needs to be loaded by the signal generator. The power signal is fixedly amplified 3000 times by the signal amplifier to form the high-voltage input 28 required for the experiment. In the biaxial electromechanical coupling constitutive experiment, the sine wave with a peak value of ±5V generated by the signal generator is amplified 3000 times by the charge amplifier , the electric field loading in the experiment is ±15000V. The insulating device enables the whole experiment process to be carried out in the medium of colorless and transparent dimethyl silicone oil (silicone oil type: 1000CS) with good insulating properties. Discharging the gear or the air and the loss of charge that needs to be measured. In the experiment, it is necessary to ensure that the whole device does not leak oil during lateral loading, and at the same time, it is necessary to ensure that the force between the horizontal transmission shaft and the oil tank is as small as possible to improve the loading accuracy. The specific structure and connection are shown in Figure 1: the insulating device includes a loading oil tank 4, a follower oil tank 6, a sealing plug 5 and a frictionless sealing device 3. The loading oil tank 4 is an oil tank made of plexiglass with three round holes that is matched with the fixed connecting rod 7 and the adjusting connecting rod 10, and the wall thickness of the oil tank is 3 mm; And the center of the bottom surface is processed with φ=28mm round holes respectively, and 12 small holes with φ=1.5mm are processed around the round holes on each side to cooperate with the frictionless sealing device 3; the bottom of the loading oil tank 4 passes through the sealing plug 5 and vertical axis The fixed connecting rod 7 of the fixed transmission shaft of force loading is connected, and guarantees that can move relatively. The follower oil tank 6 is a plexiglass oil tank with a round hole at the bottom, and the oil tank is fixedly connected with the cylindrical fixed adapter rod 8 at the lower end of the fixed drive shaft through the sealing plug 5; Moves with the adapter rod. Due to the sealing requirements, there needs to be relatively large friction between the fixed connecting rod 7 and the loading sealing plug 5, but we can read the data of the self-adjusting spherical hinge drive shaft 2 above the vertical direction during the loading process. Control the loading force in the vertical direction, because there is no connection force, so the accuracy of loading is guaranteed. The main purpose of the follower oil tank 6 is to avoid contamination of the testing machine due to the leakage of the loading oil tank 4 during the installation, loading, unloading and dismounting of the experiment. Therefore, the size of the follower oil tank 6 is larger than that of the loading oil tank 4 to ensure that all leaked silicone oil is received.

The main principle of the frictionless sealing device 3 is to make the transmission shaft and the loading oil groove 4 directly have no mutual frictional resistance on the basis of sealing, thereby reducing the error of force loading. On the basis of the above-mentioned scheme, the preferred scheme of the present invention adopts the design as shown in Fig. 3: described frictionless sealing device 3 comprises insulating pressure ring 19, annular flexible oil-proof layer 17 and insulating compression nut 20 that organic glass is made; Like this The role of the connecting device is to ensure the sealing of the connection between the loading oil tank and the loading transmission shaft in the experiment, and to avoid the decline in loading accuracy due to connection resistance. The threaded grooved cylindrical connecting rod 10 or the fixed trapezoidal pressure rod 7 pass through the middle hole of the annular flexible oil-proof layer 17 made of plexiglass material, and the inner edge of the annular flexible oil-proof layer 17 is clamped by two insulating compression nuts 20 Tight, the outer edge of the annular flexible oil-proof layer 17 is fixed by 12 small screws with the insulating pressure ring 19 made of plexiglass with 12 small holes and the loading oil groove 4. Due to the tightness of both ends, the silicone oil will not leak out, and the annular flexible oil-proof layer 17 with a certain margin in the middle allows the transmission rod and the oil groove to move freely within a certain displacement, and this displacement is sufficient. Experimental requirements. The sealing plug 5 is made of insulating rubber with neutral rigidity, the inner edge is processed into a circular through hole of suitable size, and the outer edge is processed into a circular step shape, which is connected with the loading oil tank 4 and the follower oil tank 6 .

The biaxial self-adjusting transmission shaft connects the biaxial testing machine and the loading sample. Through its self-adjusting function, the biaxial force loading can ensure real-time neutrality. The insulation device ensures the safety of the high-voltage electric field loading in the experiment in silicone oil.

In the biaxial electromechanical coupling constitutive experiment, the mechanical loading device is a vertical biaxial electro-hydraulic servo testing machine. The force output end of the testing machine includes two cylindrical toothless fixtures and two rectangular toothless fixtures. Therefore, the fixed adapter rod 8 of the fixed transmission shaft 1 is processed into a cylindrical shape matched with the cylindrical toothless fixture of the testing machine, so as to be closely connected with the testing machine to ensure fixed axial loading in the horizontal or vertical direction. The two-axis four-cylinder electro-hydraulic servo testing machine (application number: 200610012089.9) includes a vertical host, a hydraulic source and a control system. The host includes a vertical frame, and the horizontal and vertical loading transmission systems. The experimental machine can carry out force loading through displacement control, and the maximum loading force is 1×10 ⁵ N. Since the pure pressure loading is carried out on the ceramic specimen, in order to avoid the collision damage of the testing machine caused by the ceramic damage under high pressure, the displacement control force loading should be carried out on the specimen. However, for a ceramic sample of a corresponding size, the maximum loading force in the experiment does not exceed 1×10 ⁴ N, and the characteristic of ceramic materials is that the deformation is still small under the condition of a large loading force, which gives the displacement control dual The axial force brings difficulties to the loading of ceramic specimens. For the above problems, in the experimental design, the entire set of loading transmission shafts is made of No. 45 steel material. While ensuring the stiffness required for loading, a large part of the displacement in the entire loading process is consumed by the deformation of the steel loading transmission shaft. , and then through the force feedback data, the ceramic can be loaded with more accurate force. In the experiment, if the testing machine is loaded in a step-by-step manner of 0.1mm/min, the force loading rate of the ceramic sample can be controlled at 100N/min, which achieves the accuracy required by the experiment and is very convenient to control.

Figure 4 shows a schematic diagram of the charge measurement circuit. Described electric charge measurement device contains electric charge measuring instrument 27 and A/D data acquisition device, and described electric charge measuring instrument 27 comprises protection diode 23 and signal amplifier 24 and is connected in the output regulation that the measurement electric charge error is compensated at the signal amplifier output terminal 25 and a small liquid crystal display for monitoring the output signal. The above-mentioned measuring elements are integrated into a charge measuring instrument 27; the charge data is collected by an A/D acquisition card and input into a computer. The basic measurement principle of the charge measurement circuit still adopts the traditional Sawyer-Tower circuit. Due to the relatively large size of the experimental sample, the electric field strength required to be loaded in the experiment will also be greatly increased, and the discharge phenomenon caused by various reasons cannot be achieved. Avoid, once the whole device is discharged, there will be a transient high voltage phenomenon. In the state of transient high voltage generation, it is necessary to ensure that the input signal of the computer acquisition card does not exceed 10V. In order to avoid overload damage to valuable acquisition instruments, based on the traditional Sawyer-Tower circuit measurement principle, the charge measuring instrument 27 integrates an improved measurement circuit with overvoltage protection and charge compensation and a liquid crystal display, including the capacitance C ₀ The protective diode 23 connected in parallel in the measurement circuit, as well as the signal amplifier 24 and the output regulator 25. When the electric field is overloaded, if the voltage across _C0 is higher than 10V, the protection diode 23 will be turned on and play a protective role. The signal amplifier 24 and the output adjustment 25 components can make the collected data adjustable, and the output adjustment 25 adjusts the error caused by the loss of charge in the measurement so as to improve the accuracy of the measurement result. Connect a small liquid crystal display to the output terminal of the data, so that the output signal can be monitored in real time during the experiment. In addition, for the pulse signal that the diode cannot stop, a pulse stabilization element should be connected in parallel to the input terminal of the acquisition card to stabilize the high-frequency pulse signal.

Claims (4)

1. A biaxial force-electric coupling loading transmission and charge measurement device, comprising a biaxial force loading transmission and a charge measurement device, characterized in that: the biaxial force loading transmission adopts a biaxial self-adjusting transmission shaft, so The two-axis self-adjusting transmission shaft includes a set of fixed transmission shafts (1) and a set of self-adjusting spherical hinge transmission shafts (2) in both horizontal and vertical directions; the fixed transmission shaft (1) includes sequentially connected An insulating block (21), a fixed trapezoidal indenter (26), a fixed connecting rod (7) and a fixed transfer rod (8) connected to the biaxial loading tester fixture; the self-adjusting spherical hinge transmission shaft (2) Including insulating block (21), adjusting trapezoidal indenter (9), adjusting steel ball (12), connecting spring (13), adjusting connecting rod (10) and adjusting connecting rod (11) connected with biaxial loading testing machine fixture ; One end of the adjustable trapezoidal pressure head (9) is matched with the adjustment connecting rod (10) through the adjustment steel ball (12), and is flexibly connected by the connection spring (13), and the other end of the adjustment trapezoidal pressure head is connected with the insulating block (21 ) connection, one end of the adjustment transfer rod (11) is flexibly connected with the adjustment connecting rod (10), and the other end is connected with the fixture of the biaxial loading testing machine. 2. The dual-axis force-electric coupling loading transmission and charge measurement device according to claim 1, characterized in that: the device also includes an insulating device matched with the dual-axis self-adjusting transmission shaft, and the insulating device includes a loading oil tank ( 4) and a follower oil tank (6) arranged outside the loading oil tank, and a frictionless sealing device (3) is arranged between the loading oil tank and the fixed connecting rod (7) and the adjusting connecting rod (10) in the horizontal direction respectively, Sealing plugs (5) are respectively provided between the loading oil tank (4) and the follower oil tank (6) and the fixed transmission shaft in the vertical direction. 3. The dual-axis force-electric coupling loading transmission and charge measurement device according to claim 2, characterized in that: the frictionless sealing device (3) includes an insulating compression ring (19), clamped on the insulating compression ring (19) ) and the annular flexible oil-proof layer (17) and insulating compression nut (20) between the loading oil tank (4). 4. According to claim 1, 2 or 3, the biaxial electromechanical coupling loading transmission and charge measuring device is characterized in that: said charge measuring device comprises a charge measuring instrument (27) and an A/D data acquisition device, The charge measuring instrument includes a protection diode (23), a signal amplifier (24), an output regulator (25) connected to the output terminal of the signal amplifier to compensate the error of the measured charge and a liquid crystal display for monitoring the output signal.

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