Static piezoelectric constant d of PVDF piezoelectric film 31 Measuring device and measuring method thereof

Abstract

Static piezoelectric constant d of PVDF piezoelectric film 31 The invention relates to a measuring device and a measuring method thereof, and relates to the technical field of piezoelectric constant measurement of piezoelectric films, and in particular to a PVDF piezoelectric film static method piezoelectric constant d 31 The measuring device and the measuring method thereof. It comprises a base, a fixed end chuck, a movable end chuck, a force sensor, a transmission part, and a charge measuring part. The base comprises a bottom plate and a fixed plate. The fixed plate is fixed to the bottom plate, and the fixed plate is provided with a fixed end chuck; the bottom plate is provided with a transmission part; the force sensor is provided with a movable end chuck; the threaded rod of the transmission part is provided on the fixed plate and the transmission device; the sliding rod is provided on the fixed plate and the transmission device; the integrated controller controls the connection between the force sensor and the transmission device; the charge amplifier is connected to the PVDF piezoelectric film, and the charge amplifier is connected to the voltmeter. The present invention has the function of measuring the transverse piezoelectric constant d of the PVDF piezoelectric film. 31 , convenient measurement, accurate and reliable positive effect.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric constant measurement of piezoelectric films, in particular to a PVDF piezoelectric film static piezoelectric constant d 31 Measuring device and measuring method thereof. Background Art

[0002] Piezoelectric films are widely used in many fields such as acoustics, medicine, and transportation. In the process of using piezoelectric films, it is often necessary to measure the piezoelectric constant d 33 and d 31 For measurement, quasi-static d 33 The measuring instrument measures the piezoelectric constant d 33 . At present, the invention patent with application number 2021101187867 discloses a measuring fixture for measuring the transverse piezoelectric constant of piezoelectric materials, and the utility model patent with application number 2019205506427 discloses a special measuring fixture for measuring the transverse piezoelectric constant of piezoelectric materials. Most of the test methods are aimed at regular rectangular blocks or cylinders, and have certain requirements on the shape of the tested samples. However, since the PVDF piezoelectric film is a soft thin sheet, it is impossible to apply pressure in the tensile direction and the perpendicular direction of the PVDF piezoelectric film as in the existing technology. Therefore, it is impossible to effectively measure the transverse piezoelectric constant d of the PVDF piezoelectric film. 31 . Summary of the invention

[0003] The purpose of the present invention is to provide a PVDF piezoelectric film static piezoelectric constant d 31 A measuring device and a measuring method thereof are provided to measure the transverse piezoelectric constant d of a PVDF piezoelectric film. 31 , convenient measurement, accurate and reliable.

[0004] The static piezoelectric constant d of the PVDF piezoelectric film provided by the present invention is 31The measuring device comprises a base, a fixed end chuck, a movable end chuck, a force sensor, a transmission part and a charge measuring part, wherein the base comprises a bottom plate and a fixed plate, wherein the fixed plate is fixed to one end of the bottom plate, and the fixed end chuck is arranged on the fixed plate; the transmission part is arranged on the bottom plate; the force sensor is arranged with a movable end chuck corresponding to the fixed end chuck; the transmission part comprises a slider, a slide rod, a threaded rod, a transmission device and an integrated controller, wherein one end of the threaded rod is arranged on the fixed plate through a bearing, and the other end of the threaded rod passes through the slider and is arranged on the housing of the transmission device through a bearing; one end of the slide rod is arranged on the fixed plate, and the other end of the slide rod passes through the slider and is arranged on the housing of the transmission device; the slider is provided with a thread matching the threaded rod, and a force sensor is arranged on the left side of the slider; the integrated controller controls the connection between the force sensor and the transmission device; the charge measuring part comprises a charge amplifier and a voltmeter, wherein the input end of the charge amplifier is connected to the PVDF piezoelectric film, and the output end of the charge amplifier is connected to the voltmeter.

[0005] Furthermore, the fixed end clamp includes a first connecting column, a fixed end front clamping plate, a fixed end rear clamping plate and a first control valve, one end of the first connecting column is fixed on the fixed plate, the other end of the first connecting column is movably provided with a fixed end front clamping plate on the front side, and the other end of the first connecting column is provided with a fixed end rear clamping plate; a first control valve is provided on the front side of the fixed end front clamping plate, and the first control valve controls the connection of the fixed end front clamping plate.

[0006] Furthermore, the movable end chuck includes a second connecting column, a movable end front plate, a movable end rear plate, and a second control valve, one end of the second connecting column is fixed on the force sensor, the other end of the second connecting column is movably provided with a movable end front plate on the front side, and the other end of the second connecting column is provided with a movable end rear plate on the rear side; a second control valve is provided on the front side of the movable end front plate, and the second control valve controls the connection of the movable end front plate.

[0007] Furthermore, the PVDF piezoelectric film is printed with conductive ink or copper foil is pasted to form a first electrode and a second electrode of the PVDF piezoelectric film, and a charge amplifier is connected to the first electrode and the second electrode.

[0008] Furthermore, the fixed end front clamping plate, the fixed end rear clamping plate, the movable end front clamping plate and the movable end rear clamping plate are all provided with insulating rubber.

[0009] The static piezoelectric constant d of the PVDF piezoelectric film provided by the present invention is 31 The measurement method comprises the following steps:

[0010] Step 1, cutting the PVDF piezoelectric film to be tested into small pieces, and printing conductive ink or affixing copper foil on them to form the first electrode and the second electrode of the PVDF piezoelectric film, making the PVDF piezoelectric film sample to be tested, and calculating the charge collection area area A of the PVDF piezoelectric film sample to be tested and the effective cross-sectional area area S of the PVDF piezoelectric film;

[0011] Step 2, fixing the two ends of the PVDF piezoelectric film sample to be tested in step 1 by using a fixed end chuck and a movable end chuck respectively; connecting the first electrode and the second electrode through a charge amplifier;

[0012] Step 3, set the force value F on the integrated controller, press the start button, the force sensor and the actuator start working, and the slider moves the movable end chuck away from the fixed end chuck under the action of the slide rod and the threaded rod; when the force value measured by the force sensor reaches the set value, the actuator stops working;

[0013] Step 4, manually close the second control valve switch, at which time the second control valve stops working, so that the PVDF piezoelectric film sample to be tested is separated from the moving end chuck; at this time, the voltmeter will display the voltage signal generated by the sudden disappearance of F. When F disappears, the voltage signal on the voltmeter is valid, and the charge Q displayed by the charge amplifier is recorded;

[0014] Step 5, by formula d 31 =(Q / A) / (F / S) to get d 31 ,

[0015] Wherein, Q is the charge amount; A is the charge collection area of ​​the PVDF film; F is the applied force; and S is the effective cross-sectional area of ​​the PVDF film.

[0016] Further, in the step 2, the first control valve switch is started, the first control valve opens the fixed end front clamp, and the left end of the PVDF piezoelectric film in step 1 is fixed between the fixed end front clamp and the fixed end rear clamp, and the first control valve switch is closed, the first control valve causes the fixed end front clamp and the fixed end rear clamp to clamp the left end of the PVDF piezoelectric film sample to be tested; the second control valve switch is started, the second control valve opens the movable end front clamp, and the integrated controller is started, and the movable end chuck is moved by the manual advance and manual retreat buttons on the integrated controller, and the relative position of the movable end chuck and the right end of the PVDF piezoelectric film sample to be tested is adjusted so that the movable end chuck can properly clamp the right end of the PVDF piezoelectric film sample to be tested, and the second control valve switch is closed, the second control valve causes the movable end front clamp and the movable end rear clamp to clamp the right end of the PVDF piezoelectric film sample to be tested; the right end of the PVDF piezoelectric film in step 1 is fixed between the movable end front clamp 32 and the movable end rear clamp 33.

[0017] Further, in step 3, the movable end chuck is moved by the manual advance and manual retreat buttons on the integrated controller so that the fixed end chuck and the movable end chuck fix the PVDF piezoelectric film sample to be tested; then, the force value F is set on the integrated controller, and the start button is pressed, and the movable end chuck moves in a direction away from the fixed end chuck.

[0018] Furthermore, the stretching direction of the PVDF piezoelectric film is usually recorded as direction 1, the direction perpendicular to direction 1 in the piezoelectric film surface is direction 2, and the thickness direction of the piezoelectric film is direction 3; the piezoelectric constant d 31 It is the ratio of the change in the electric displacement component D3 caused by the change in the stress component XI in the piezoelectric material when the electric field strength is 0 or constant to the change in the stress component XI.

[0019] Right now

[0020] where d 31 is the piezoelectric constant; D is the electric displacement; X is the stress; E is the electric field intensity; the superscript 1 is the 1st direction, and the superscript 3 is the 3rd direction.

[0021] Formula (1) can be further simplified to obtain:

[0022]

[0023] Wherein, Q is the charge amount; A is the charge collection area of ​​the PVDF film; F is the applied force; and S is the effective cross-sectional area of ​​the PVDF film.

[0024] Further, the static piezoelectric constant d of the PVDF piezoelectric film is 31 The measuring device is placed in a constant temperature and humidity chamber for measurement, and the piezoelectric constant d under a specific ambient temperature and humidity can be obtained. 31 .

[0025] The static piezoelectric constant d of the PVDF piezoelectric film provided by the present invention is 31 The measuring device and measuring method thereof are as follows: the PVDF piezoelectric film to be tested is printed with conductive ink or copper foil to form the first electrode and the second electrode of the PVDF piezoelectric film, and the charge collection area A of the PVDF piezoelectric film sample to be tested and the effective cross-sectional area S of the PVDF piezoelectric film are calculated. The PVDF piezoelectric film sample to be tested is fixed with a fixed end chuck and a movable end chuck, and after the charge amplifier is connected to the first electrode and the second electrode, the force value F is set on the integrated controller, and the charge amount Q displayed by the charge amplifier is recorded. The formula d 31 =(Q / A) / (F / S) to get d 31 The static method can be used to measure the transverse piezoelectric constant d of relatively soft PVDF piezoelectric films. 31Therefore, the present invention has the ability to measure the transverse piezoelectric constant d of PVDF piezoelectric film. 31 , convenient measurement, accurate and reliable positive effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings partially disclose specific embodiments of the present invention, wherein:

[0027] Figure 1 It is a schematic diagram of the structure of the present invention;

[0028] Figure 2 It is a structural schematic diagram of the slider of the present invention;

[0029] Figure 3 It is a schematic diagram of the connection between the charge measurement unit and the PVDF piezoelectric film of the present invention;

[0030] Figure 4 is a tensile direction diagram of the PVDF piezoelectric film of the present invention;

[0031] Figure 5 It is a usage state diagram of the present invention;

[0032] Figure numerals: 1. base; 11. bottom plate; 12. fixed plate; 2. fixed end chuck; 21. first connecting column; 22. fixed end front clamp; 23. fixed end rear clamp; 24. first control valve; 25. first control valve switch; 3. movable end chuck; 31. second connecting column; 32. movable end front clamp; 33. movable end rear clamp; 34. second control valve; 35. second control valve switch; 4. force sensor; 5. transmission part; 51. slider; 52. slide rod; 53. threaded rod; 54. transmission; 55. integrated controller; 56. bearing; 6. charge measurement part; 61. charge amplifier; 62. voltmeter; 7. PVDF piezoelectric film; 71. first electrode; 72. second electrode. DETAILED DESCRIPTION

[0033] like Figure 1-4 As shown, the static piezoelectric constant d of the PVDF piezoelectric film provided by the present invention is 31The measuring device comprises a base 1, a fixed end chuck 2, a movable end chuck 3, a force sensor 4, a transmission part 5, and a charge measuring part 6. The base 1 comprises a bottom plate 11 and a fixed plate 12. The fixed plate 12 is fixed to one end of the bottom plate 11, and the fixed end chuck 2 is arranged on the fixed plate 12; the transmission part 5 is arranged on the bottom plate 11; the force sensor 4 is provided with a movable end chuck 3 corresponding to the fixed end chuck 2; the transmission part 5 comprises a slider 51, a slide rod 52, a threaded rod 53, a transmission device 54 and an integrated controller 55. One end of the threaded rod 53 is arranged on the fixed plate 12 through a bearing 56. 3 passes through the slider 51 and is arranged on the housing of the transmission device 54 through the bearing 56; one end of the slide bar 52 is arranged on the fixed plate 12, and the other end of the slide bar 52 passes through the slider 51 and is arranged on the housing of the transmission device 54; the slider 51 is provided with a thread matched with the threaded rod 53, and a force sensor 4 is arranged on the left side of the slider 51; the integrated controller 55 controls the connection between the force sensor 4 and the transmission device 54; the charge measurement unit 6 includes a charge amplifier 61 and a voltmeter 62, the input end of the charge amplifier 61 is connected to the PVDF piezoelectric film 7, and the output end of the charge amplifier 61 is connected to the voltmeter 62.

[0034] Embodiment 1:

[0035] like Figure 5 As shown, when the present invention is used, first, the PVDF piezoelectric film 7 to be tested is cut into small pieces, and conductive ink is printed or copper foil is pasted on it to form the first electrode 71 and the second electrode 72 of the PVDF piezoelectric film, and the PVDF piezoelectric film sample to be tested is made, and the PVDF piezoelectric film charge collection area A and the effective cross-sectional area S of the PVDF piezoelectric film sample to be tested are calculated. Then, the two ends of the PVDF piezoelectric film sample to be tested are fixed by the fixed end chuck 2 and the movable end chuck 3 respectively; the charge amplifier 61 is connected to the first electrode 71 and the second electrode 72. After that, the force value F is set on the integrated controller, and the start button is pressed, the force sensor 4 and the actuator 54 start to work, and the slider 51 moves the movable end chuck 3 away from the fixed end chuck 2 under the action of the slide rod 52 and the threaded rod 53; when the force value measured by the force sensor 4 reaches the set value, the actuator 54 stops working. Then, manually close the second control valve switch 35, at which time the second control valve 34 stops working, so that the PVDF piezoelectric film sample to be tested is separated from the movable end clamp 3; at this time, the voltmeter 62 will display the voltage signal generated by the sudden disappearance of F. When F disappears, if no voltage signal appears, it is invalid; when F disappears, if a voltage signal appears on the voltmeter, it is valid, and the charge amount Q displayed by the charge amplifier 61 is recorded; finally, through the formula d 31 =(Q / A) / (F / S) to get d 31, where Q is the charge; A is the charge collection area of ​​the PVDF film; F is the applied force; S is the effective cross-sectional area of ​​the PVDF film. Multiple measurements can be taken to obtain the average value to improve the piezoelectric constant d of the PVDF piezoelectric film. 31 measurement accuracy.

[0036] The fixed end clamp 2 comprises a first connection column 21, a fixed end front clamp plate 22, a fixed end rear clamp plate 23 and a first control valve 24. One end of the first connection column 21 is fixed on the fixed plate 12, and the fixed end front clamp plate 22 is movably arranged at the front side of the other end of the first connection column 21. The fixed end rear clamp plate 23 is arranged at the other end of the first connection column 21. The first control valve 24 is arranged at the front side of the fixed end front clamp plate 22, and the first control valve 24 controls the connection of the fixed end front clamp plate 22. Start the first control valve switch 25, the first control valve 24 opens the fixed end front clamp plate 22, and fixes the left end of the PVDF piezoelectric film in step 1 between the fixed end front clamp plate 22 and the fixed end rear clamp plate 23.

[0037] The above-mentioned mobile end clamp 3 includes a second connecting column 31, a mobile end front clamp 32, a mobile end rear clamp 33, and a second control valve 34. One end of the second connecting column 31 is fixed on the force sensor 4, and the front side of the other end of the second connecting column 31 is movably provided with the mobile end front clamp 32, and the rear side of the other end of the second connecting column 31 is provided with the mobile end rear clamp 33; the front side of the mobile end front clamp 32 is provided with a second control valve 34, and the second control valve 34 controls the connection of the mobile end front clamp 32. Start the second control valve switch 35, the second control valve 34 opens the mobile end front clamp 32, and fixes the right end of the PVDF piezoelectric film in step 1 between the mobile end front clamp 32 and the mobile end rear clamp 33.

[0038] The fixed end front clamping plate 22, the fixed end rear clamping plate 23, the movable end front clamping plate 32 and the movable end rear clamping plate 33 are all provided with insulating rubber to avoid measurement errors and improve measurement accuracy.

[0039] Embodiment 2:

[0040] like Figure 3As shown, the PVDF piezoelectric film 7 is printed with conductive ink or copper foil is pasted to form the first electrode 71 and the second electrode 72 of the PVDF piezoelectric film, and the charge amplifier 61 is connected to the first electrode 71 and the second electrode 72. The input end of the charge amplifier 61 is connected to the PVDF piezoelectric film 7, and the output end of the charge amplifier 61 is connected to the voltmeter 62. The PVDF piezoelectric film 7 to be tested is cut into small pieces. Conductive ink is printed or copper foil is pasted on both sides of the PVDF piezoelectric film 7 to form the first electrode 71 and the second electrode 72 of the PVDF piezoelectric film. The first electrode 71 and the second electrode 72 of the PVDF piezoelectric film are formed to be of the same size, and are relatively pasted or printed on both sides of the PVDF piezoelectric film, and the lead-out direction of the electrode connector connected to the external circuit is consistent with the 2 directions of the PVDF piezoelectric film to make the PVDF piezoelectric film sample to be tested. Calculate the charge collection area A of the PVDF piezoelectric film sample to be tested and the effective cross-sectional area S of the PVDF piezoelectric film.

[0041] Embodiment 3:

[0042] The static piezoelectric constant d of the PVDF piezoelectric film provided by the present invention is 31 The measurement method comprises the following steps:

[0043] Step 1, cut the PVDF piezoelectric film 7 to be tested into small pieces, and print conductive ink or stick copper foil on it to form the first electrode 71 and the second electrode 72 of the PVDF piezoelectric film to make the PVDF piezoelectric film sample to be tested, and calculate the charge collection area area A of the PVDF piezoelectric film sample to be tested and the effective cross-sectional area area S of the PVDF piezoelectric film.

[0044] Step 2, fix the two ends of the PVDF piezoelectric film sample to be tested in step 1 with the fixed end clamp 2 and the movable end clamp 3 respectively. Start the first control valve switch 25, the first control valve 24 opens the fixed end front clamp 22, fix the left end of the PVDF piezoelectric film in step 1 between the fixed end front clamp 22 and the fixed end rear clamp 23, close the first control valve switch 25, the first control valve 24 will make the fixed end front clamp 22 and the fixed end rear clamp 23 clamp the left end of the PVDF piezoelectric film sample to be tested; start the second control valve switch 35, the second control valve 34 opens the movable end front clamp 32, start the integrated controller 55, through the integrated controller 5 5, the manual forward and manual backward buttons on the mobile end clamp 3 are used to move the mobile end clamp 3, and the relative positions of the mobile end clamp 3 and the right end of the PVDF piezoelectric film sample to be tested are adjusted so that the mobile end clamp 3 can properly clamp the right end of the PVDF piezoelectric film sample to be tested, and the second control valve switch 35 is closed, and the second control valve 34 makes the mobile end front clamp 32 and the mobile end rear clamp 33 clamp the right end of the PVDF piezoelectric film sample to be tested; the right end of the PVDF piezoelectric film in step 1 is fixed between the mobile end front clamp 32 and the mobile end rear clamp 33. The charge amplifier 61 is connected to the first electrode 71 and the second electrode 72.

[0045] Step 3, move the movable end chuck 3 through the manual advance and manual retreat buttons on the integrated controller 55, so that the fixed end chuck 2 and the movable end chuck 3 fix the PVDF piezoelectric film sample to be tested; then, set the force value F on the integrated controller, the force sensor 4 and the transmission 54 start working, and the slider 51 moves the movable end chuck 3 away from the fixed end chuck 2 under the action of the slide rod 52 and the threaded rod 53; when the force value measured by the force sensor 4 reaches the set value, the transmission 54 stops working.

[0046] Step 4, manually close the second control valve switch 35, at this time the second control valve stops 34 working, so that the PVDF piezoelectric film sample to be tested is separated from the moving end clamp 3; at this time the voltmeter 62 will display the voltage signal generated by the sudden disappearance of F. When F disappears, if no voltage signal appears at the moment of disappearance, it is invalid; when F disappears, a voltage signal appears on the voltmeter at the moment of disappearance, it is valid, and the charge Q displayed by the charge amplifier 61 is recorded.

[0047] Step 5, by formula d 31 =(Q / A) / (F / S) to get d 31 , where Q is the charge; A is the charge collection area of ​​the PVDF film; F is the applied force; S is the effective cross-sectional area of ​​the PVDF film. Multiple measurements can be taken to obtain the average value to improve the piezoelectric constant d of the PVDF piezoelectric film. 31 measurement accuracy.

[0048] The stretching direction of PVDF piezoelectric film is usually recorded as direction 1, the direction perpendicular to direction 1 in the piezoelectric film surface is direction 2, and the thickness direction of the piezoelectric film is direction 3; the piezoelectric constant d 31 It is the ratio of the change in the electric displacement component D3 caused by the change in the stress component XI in the piezoelectric material when the electric field strength is 0 or constant to the change in the stress component XI.

[0049] Right now

[0050] where d 31 is the piezoelectric constant; D is the electric displacement; X is the stress; E is the electric field intensity; the superscript 1 is the 1st direction, and the superscript 3 is the 3rd direction.

[0051] Formula 1 can be further simplified to obtain:

[0052]

[0053] Wherein, Q is the charge amount; A is the charge collection area of ​​the PVDF film; F is the applied force; and S is the effective cross-sectional area of ​​the PVDF film.

[0054] The static piezoelectric constant d of the PVDF piezoelectric film 31 The measuring device is placed in a constant temperature and humidity chamber for measurement, and the piezoelectric constant d under a specific ambient temperature and humidity can be obtained. 31 .

Claims

1. Static piezoelectric constant d of a PVDF piezoelectric film 31 Measurement method of PVDF piezoelectric film static piezoelectric constant d 31 The measuring device comprises a base (1), a fixed end chuck (2), a movable end chuck (3), a force sensor (4), a transmission part (5), and a charge measuring part (6). The base (1) comprises a bottom plate (11) and a fixed plate (12), wherein the fixed plate (12) is fixed to one end of the bottom plate (11), and a fixed end clamp (2) is provided on the fixed plate (12); a transmission part (5) is provided on the bottom plate (11); and the force sensor (4) is provided with a movable end clamp (3) corresponding to the fixed end clamp (2); The transmission part (5) comprises a slider (51), a slide rod (52), a threaded rod (53), a transmission device (54) and an integrated controller (55); one end of the threaded rod (53) is arranged on a fixed plate (12) via a bearing (56), and the other end of the threaded rod (53) passes through the slider (51) and is arranged on a housing of the transmission device (54) via a bearing (56); one end of the slide rod (52) is arranged on the fixed plate (12), and the other end of the slide rod (52) passes through the slider (51) and is arranged on a housing of the transmission device (54); the slider (51) is provided with a thread matching the threaded rod (53), and a force sensor (4) is arranged on the left side of the slider (51); the integrated controller (55) controls the connection between the force sensor (4) and the transmission device (54); The charge measurement unit (6) comprises a charge amplifier (61) and a voltmeter (62), wherein the input end of the charge amplifier (61) is connected to the PVDF piezoelectric film (7), and the output end of the charge amplifier (61) is connected to the voltmeter (62); The fixed end clamp (2) comprises a first connecting column (21), a fixed end front clamp (22), a fixed end rear clamp (23) and a first control valve (24); one end of the first connecting column (21) is fixed to the fixed plate (12); the fixed end front clamp (22) is movably provided at the front side of the other end of the first connecting column (21); the fixed end rear clamp (23) is provided at the other end of the first connecting column (21); the first control valve (24) is provided at the front side of the fixed end front clamp (22); the first control valve (24) controls the connection of the fixed end front clamp (22); The movable end clamp (3) comprises a second connecting column (31), a movable end front clamp (32), a movable end rear clamp (33), and a second control valve (34); one end of the second connecting column (31) is fixed to the force sensor (4); the movable end front clamp (32) is movably provided on the front side of the other end of the second connecting column (31); and the movable end rear clamp (33) is provided on the rear side of the other end of the second connecting column (31); a second control valve (34) is provided on the front side of the movable end front clamp (32); and the second control valve (34) controls the connection of the movable end front clamp (32); The PVDF piezoelectric film (7) is printed with conductive ink or affixed with copper foil to form a first electrode (71) and a second electrode (72) of the PVDF piezoelectric film, and the charge amplifier (61) is connected to the first electrode (71) and the second electrode (72); Static piezoelectric constant d of PVDF piezoelectric film 31 A method for measuring , characterized in that The following steps are involved: Step 1, cutting the PVDF piezoelectric film (7) to be tested into small pieces, and printing conductive ink or affixing copper foil thereon to form a first electrode (71) and a second electrode (72) of the PVDF piezoelectric film, to prepare a PVDF piezoelectric film sample to be tested, and calculating the PVDF piezoelectric film charge collection area A and the effective cross-sectional area S of the PVDF piezoelectric film sample to be tested; Step 2, fixing the two ends of the PVDF piezoelectric film sample to be tested in step 1 using a fixed end clamp (2) and a movable end clamp (3) respectively; the charge amplifier (61) is connected to the first electrode (71) and the second electrode (72); Step 3, set the force value F on the integrated controller, press the start button, the force sensor (4) and the transmission (54) start to work, and the slider (51) moves the movable end clamp (3) away from the fixed end clamp (2) under the action of the slide rod (52) and the threaded rod (53); when the force value measured by the force sensor (4) reaches the set value, the transmission (54) stops working; Step 4, manually close the second control valve switch (35), at which time the second control valve (34) stops working, so that the PVDF piezoelectric film sample to be tested is separated from the movable end clamp (3); at this time, the voltmeter (62) will display the voltage signal generated by the sudden disappearance of F. When F disappears, the voltage signal on the voltmeter is valid, and the charge Q displayed by the charge amplifier (61) is recorded; Step 5, by formula d 31 =(Q / A) / (F / S) to get d 31 , Where, Q is the charge; A is the charge collection area of ​​the PVDF film; F is the applied force; S is the effective cross-sectional area of ​​the PVDF film.

2. The static piezoelectric constant d of the PVDF piezoelectric film according to claim 1 31 A method for measuring, characterized in that The fixed end front clamping plate (22), the fixed end rear clamping plate (23), the movable end front clamping plate (32) and the movable end rear clamping plate (33) are all provided with insulating rubber.

3. The static piezoelectric constant d of the PVDF piezoelectric film according to claim 1 31 A method for measuring , characterized in that In the step 2, the first control valve switch (25) is started, the first control valve (24) opens the fixed end front clamping plate (22), and the left end of the PVDF piezoelectric film in step 1 is fixed between the fixed end front clamping plate (22) and the fixed end rear clamping plate (23); the first control valve switch (25) is closed, and the first control valve (24) causes the fixed end front clamping plate (22) and the fixed end rear clamping plate (23) to clamp the left end of the PVDF piezoelectric film sample to be tested; the second control valve switch (35) is started, the second control valve (34) opens the movable end front clamping plate (32), and the integrated controller (55) is started, and the Move the movable end chuck (3) by pressing the manual advance and manual retreat buttons on the integrated controller (55), adjust the relative positions of the movable end chuck (3) and the right end of the PVDF piezoelectric film sample to be tested, so that the movable end chuck (3) properly clamps the right end of the PVDF piezoelectric film sample to be tested, close the second control valve switch (35), and the second control valve (34) will cause the movable end front clamping plate (32) and the movable end rear clamping plate (33) to clamp the right end of the PVDF piezoelectric film sample to be tested; fix the right end of the PVDF piezoelectric film in step 1 between the movable end front clamping plate (32) and the movable end rear clamping plate (33).

4. The static piezoelectric constant d of the PVDF piezoelectric film according to claim 1 31 A method for measuring , characterized in that In step 3, the movable end chuck (3) is moved by the manual advance and manual retreat buttons on the integrated controller (55), so that the fixed end chuck (2) and the movable end chuck (3) fix the PVDF piezoelectric film sample to be tested; then, the force value F is set on the integrated controller, and the start button is pressed, so that the movable end chuck (3) moves in a direction away from the fixed end chuck (2).

5. The static piezoelectric constant d of the PVDF piezoelectric film according to claim 1 31 A method for measuring , characterized in that The stretching direction of the PVDF piezoelectric film is usually recorded as direction 1, the direction perpendicular to direction 1 in the piezoelectric film surface is direction 2, and the thickness direction of the piezoelectric film is direction 3; the piezoelectric constant d 31 It is the ratio of the change in the electric displacement component D3 caused by the change in the stress component Χ1 in the piezoelectric material when the electric field intensity is 0 or constant to the change in the stress component Χ1; Right now , where d 31 is the piezoelectric constant; D is the electric displacement; X is the stress; E is the electric field intensity; the superscript 1 is the 1st direction, and the superscript 3 is the 3rd direction; Formula (1) can be further simplified to obtain: , where Q is the charge; A is the charge collection area of ​​the PVDF film; F is the applied force; and S is the effective cross-sectional area of ​​the PVDF film.

6. The static piezoelectric constant d of the PVDF piezoelectric film according to claim 1 31 A method for measuring , characterized in that The static piezoelectric constant d of the PVDF piezoelectric film 31 The measuring device is placed in a constant temperature and humidity chamber for measurement, and the piezoelectric constant d under ambient temperature and humidity can be obtained. 31 .

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