CN203672533U - PVDF based drop hammer tester impact force measuring device - Google Patents

Abstract

The utility model discloses a PVDF based drop hammer tester impact force measuring device, which comprises a PVDF piezoelectric film, metal base plates and a dynamic data acquisition instrument, wherein a hammer of the drop hammer tester is provided with a cavity, two metal base plates are horizontally stacked and compressed in the cavity of the hammer, the PVDF piezoelectric film is arranged between the two metal base plates and separates the upper metal base plate from the lower metal base plate completely, the PVDF piezoelectric film and the metal base plates are arranged in a mode of being insulated from the hammer, the side surface of the hammer is provided with wiring holes, each of the two metal base plates introduces a wire from the wiring hole and is electrically connected with the dynamic data acquisition instrument through a discharge resistor. According to the utility model, the PVDF piezoelectric film is clamped between the two metal base plates and acts as an impact force test sensing element for the drop hammer tester, and the PVDF based drop hammer tester impact force measuring device is simple in structure, stable, reliable and high in measurement precision.

Description

A kind of drop hammer tester impact force measurements device based on PVDF

Technical field

The utility model belongs to impact force measurements technical field, is specifically related to a kind of drop hammer tester impact force measurements device based on PVDF.

Background technology

Impacting load test often needs, according to different loading velocity scopes, to select corresponding load mode.In the time that high speed impact loads, adopt split hopkinson press bar test unit, Taylor's bar impulse test, or light-gas gun loads, but for the shock problem often occurring in Practical Project, all belong to the category of low velocity impact, while research for this class problem, falling weight impact test is more simple and reliable, reproducible, be usually used to rate of strain 10 ^-5/ s～10 ¹within the scope of/s, apply impact load.Drop hammer tester is the device that carries out specially drop-weight test, owing to can controlling easily the size of impact energy, is widely used in the fields such as ballistics research and production quality control.

Drop hammer tester is generally made up of parts such as mass, tup, guide rail, lifting motor, tup releasing means, impulse test pedestals, mass is installed on tup, when tup rises to after specified altitude assignment, discharge tup, tup and mass vertically fall along guide rail, apply impulsive force on test specimen, thereby complete impact loading procedure.The impulsive force applying catches by the sensor being arranged on tup often, such as power sensor, or acceleration transducer, in test process, equipment needed thereby is more, and cost of testing system is higher.Specifically: for power sensor, when test, need to, by the output terminal access dynamic strain indicator of power sensor, then dynamic strain indicator be accessed to Dynamic Data Acquiring instrument; For acceleration transducer, the output terminal access charge amplifier of degree of will speed up sensor, then charge amplifier is accessed to Dynamic Data Acquiring instrument, finally according to Newton second law, degree of will speed up value is multiplied by tup quality and obtains tup and be applied to the impulsive force on test specimen.

Utility model content

It is simple and reliable that technical purpose of the present utility model is to provide a kind of test macro, drop hammer tester impact force measurements device with low cost, to solve existing drop hammer tester impact force measurements device, impulsive force test macro complexity, the testing tool needing is more, the problem that cost is higher.

The utility model utilizes PVDF(Kynoar) piezoelectric effect of material, a kind of drop hammer tester impact force measurements device based on PVDF is provided.The utility model adopts following technical scheme: a kind of drop hammer tester impact force measurements device based on PVDF, comprises PVDF piezoelectric membrane 12, metal caul 10 and Dynamic Data Acquiring instrument 8; The tup 1 of described drop hammer tester is provided with inner chamber, two metal cauls 10 stack up and down and are pressed among the inner chamber of described tup 1, described PVDF piezoelectric membrane 12 is arranged between two metal cauls 10 upper and lower two metal cauls is separated completely, described PVDF piezoelectric membrane 12 and metal caul arrange with tup 1 insulation respectively, described tup side is provided with wiring hole 15, two metal cauls 10 are drawn wire from described wiring hole 15, and are electrically connected with described Dynamic Data Acquiring instrument 8 by discharge resistance.

The inner chamber of described tup 1 can mill out along the axis of tup upper surface, and the upper surface of tup 1 is connected metal caul and PVDF piezoelectric membrane are compressed by tup gib screw 6, the upper end quality of connection piece 3 of described tup joint flange 2 with tup joint flange 2.Wherein, described tup joint flange 2 upper ends are provided with mass cushion cap 4, and described mass 3 is bolted and is installed on described mass cushion cap 4, and the mass that capable of regulating arranges varying number is realized the adjustment of tup weight.

As preferred version, described PVDF piezoelectric membrane 12 two sides are silver-plated.

Further, the one side that described metal caul 10 contacts with PVDF piezoelectric membrane is smeared the electric conductivity of conducting resinl increase and PVDF piezoelectric membrane, and the another side contacting with tup arranges insulation film 11.

The preferred Kapton of described insulation film 11.

Further, between the side of described metal caul 10 and the inner chamber of tup 1, nylon ring 9 is set, described nylon ring 9 is provided with wiring hole 15.

In the utility model, the side of two metal cauls 10 is equipped with screw 14, and described metal caul 10 is drawn wire by terminal screw 13.

Further, described wire adopts twin-core shielded conductor.

In the utility model, described discharge resistance is connected with PVDF piezoelectric membrane, and described Dynamic Data Acquiring instrument 8 is electrically connected with described discharge resistance two ends, measurement be the pressure drop at discharge resistance two ends.

The utlity model has following beneficial effect:

1) PVDF piezoelectric membrane has many superior performances: this material piezoelectric coefficient is high, in the face of under identical stress level effect, higher more than 10 times than piezoelectric ceramics output intensity; Adopt PVDF piezoelectric membrane to have splendid signal to noise ratio (S/N ratio) as the sensor of sensitive element, making can not need noise filtering in actual measurement; This piezoelectric membrane has the response speed of nanosecond, the wide cut pressure measurement scope of 0～20GPa, is applicable to being very much applied to the application of high voltage transient, such as the stress test under blast and percussive action; And PVDF has splendid pliability, can be processed into easily various shapes and thickness, physical strength is high, good endurance, quality is light, with low cost, reusable.The utility model, by described PVDF piezoelectric membrane, is clipped between two described metal cauls, as the impulsive force test sensing element of drop hammer tester, simple in structure, reliable and stable.

2) PVDF piezoelectric membrane is done the used time by the impact load, can be considered the voltage source of the electric capacity of connecting, wherein voltage source V _srepresent PVDF film, the stress that its output valve stands to sensor is directly proportional; And the electric capacity c of PVDF film ₀can be considered as an equivalent capacitive reactance, when measurement and discharge resistance R form bleeder circuit.But c ₀with the same RC oscillatory circuit that forms a single order of R, can be considered as a Hi-pass filter, filter out the low-frequency noise of generation of vibration, farthest reduce the interference in output signal, measuring accuracy is high.

Below in conjunction with the drawings and specific embodiments, the utility model is described further.

Accompanying drawing explanation

Fig. 1 is hammehead structure schematic diagram.

Fig. 2 is the utility model structural representation.

Fig. 3 is the measurement mechanism decomposing schematic representation of tup inside.

Fig. 4 is the test circuit figure of PVDF piezoelectric membrane.

Number in the figure: 1-tup, 2-tup joint flange, 3-mass, 4-mass cushion cap, 5-mass set bolt, 6-tup gib screw, 7-twin-core shielded conductor, 8-Dynamic Data Acquiring instrument, 9-nylon ring, 10-metal caul, 11-insulation film, 12-PVDF piezoelectric membrane, 13-terminal screw, 14-screw, 15-wiring hole.

Embodiment

Embodiment

Referring to Fig. 1 to Fig. 3, the drop hammer tester impact force measurements device based on PVDF that the utility model provides comprises PVDF piezoelectric membrane 12, metal caul 10 and Dynamic Data Acquiring instrument 8; The tup 1 of drop hammer tester is provided with inner chamber, two metal cauls 10 overlay among the inner chamber of tup 1, PVDF piezoelectric membrane 12 is arranged between two metal cauls 10 and contacts with upper and lower two metal cauls respectively, PVDF piezoelectric membrane 12 and metal caul arrange with tup 1 insulation respectively, tup side is provided with wiring hole 15, two metal cauls 10 are drawn wire from wiring hole 15, and are electrically connected with Dynamic Data Acquiring instrument 8 by discharge resistance.

Inner chamber is offered in the upper surface of described tup 1, and the upper surface of tup 1 is connected by tup gib screw 6 with tup joint flange 2, and the upper end of tup joint flange 2 is mass cushion cap 4, on mass cushion cap 4, is fixed and is impacted mass 3 by mass set bolt 5.As preferred version, the present embodiment adopts PVDF piezoelectric membrane as sensitive element, and PVDF piezoelectric membrane is thickness 50 μ m, diameter is the circle of 90mm, two sides is silver-plated, and smears conducting resinl at metal caul 10 and PVDF piezoelectric membrane surface of contact, guarantees good electric conductivity.The another side that metal caul 10 contacts with tup arranges insulation film 11, and what the present embodiment adopted is Kapton.In order to prevent that two metal cauls and tup inside from coming in contact, cause the two sides short circuit of PVDF piezoelectric membrane, the nylon ring 9 of insulation is set between the side of metal caul 10 and the inner chamber of tup 1, on nylon ring 9, be provided with equally wiring hole 15.The side of two metal cauls 10 is equipped with screw 14, and metal caul 10 is drawn wire by terminal screw 13.

In the present embodiment, wire adopts twin-core shielded conductor 7, the RC oscillatory circuit of discharge resistance and a PVDF piezoelectric membrane single order in series.Specifically referring to Fig. 4, PVDF piezoelectric membrane 12 is done the used time by the impact load, can be considered the voltage source of the electric capacity of connecting, and wherein voltage source V s represents PVDF piezoelectric membrane, and the stress that its output valve stands to sensor is directly proportional; And the electric capacity c0 of PVDF piezoelectric membrane 12 can be considered as an equivalent capacitive reactance, when measurement and discharge resistance R form bleeder circuit.But the same RC oscillatory circuit that forms a single order of c0 and R can be considered as a Hi-pass filter, filters out the low-frequency noise of generation of vibration, farthest reduces the interference in output signal.Two backing metals are consistent with tup impact force action direction with the installation axis of the core component of PVDF piezoelectric membrane composition, on terminal screw, connect discharge resistance R by twin-core shielded conductor.As shown in Figure 2 and Figure 4, PVDF piezoelectric membrane and discharge resistance R form discharge circuit jointly, record the voltage signal at discharge resistance R two ends by Dynamic Data Acquiring instrument, can convert and obtain the impulsive force signal that tup applies in impact loading procedure, concrete transformational relation is:

$q\left(t\right)=\frac{Q\left(t\right)}{A}=\underset{0}{\overset{t}{\∫}}\frac{U\left(t\right)}{A(R+X_c)}\mathrm{dt}---\left(a\right)$

$\mathrm{\σ}\left(t\right)=\frac{q\left(t\right)}{k}---\left(b\right)$

F(t)＝σ(t)A (c)

Q (t) is the electric density on PVDF piezoelectric membrane, the quantity of electric charge that Q (t) produces due to the variation of stress for PVDF piezoelectric membrane, and A is the area of PVDF piezoelectric membrane, R is the discharge resistance in test circuit, X _cfor the capacitive reactance of PVDF piezoelectric membrane, because tested object is high-frequency signal, size and the signal frequency of capacitive reactance are inversely proportional to, and with respect to the discharge resistance of 100 ohm, capacitive reactance is herein negligible.σ (t) is the stress at PVDF piezoelectric membrane place, the impulsive force that F (t) applies for tup, and k is the piezoelectric modulus of PVDF piezoelectric membrane, for the utility model, piezoelectric modulus is 24pC/N.

Claims (10)

1. the drop hammer tester impact force measurements device based on PVDF, is characterized in that: comprise PVDF piezoelectric membrane (12), metal caul (10) and Dynamic Data Acquiring instrument (8), the tup (1) of described drop hammer tester is provided with inner chamber, two metal cauls (10) stack up and down and are pressed among the inner chamber of described tup (1), described PVDF piezoelectric membrane (12) is arranged between two metal cauls (10) upper and lower two metal cauls is separated completely, described PVDF piezoelectric membrane (12) and metal caul arrange with tup (1) insulation respectively, described tup side is provided with wiring hole (15), two metal cauls (10) are drawn wire from described wiring hole (15), and be electrically connected with described Dynamic Data Acquiring instrument (8) by discharge resistance.

2. a kind of drop hammer tester impact force measurements device based on PVDF according to claim 1, it is characterized in that: inner chamber is offered in the upper surface of described tup (1), the upper surface of tup (1) is connected by tup gib screw (6) with tup joint flange (2), the upper end quality of connection piece (3) of described tup joint flange (2).

3. a kind of drop hammer tester impact force measurements device based on PVDF according to claim 2, it is characterized in that: described tup joint flange (2) upper end is provided with mass cushion cap (4), described mass (3) is bolted and is installed on described mass cushion cap (4).

4. a kind of drop hammer tester impact force measurements device based on PVDF according to claim 1, is characterized in that: described PVDF piezoelectric membrane (12) two sides is silver-plated.

5. a kind of drop hammer tester impact force measurements device based on PVDF according to claim 4, it is characterized in that: described metal caul (10) is smeared conducting resinl with the one side that PVDF piezoelectric membrane contacts, the another side contacting with tup arranges insulation film (11).

6. a kind of drop hammer tester impact force measurements device based on PVDF according to claim 5, is characterized in that: described insulation film (11) is Kapton.

7. a kind of drop hammer tester impact force measurements device based on PVDF according to claim 6, it is characterized in that: between the side of described metal caul (10) and the inner chamber of tup (1), nylon ring (9) is set, described nylon ring (9) is provided with wiring hole (15).

8. a kind of drop hammer tester impact force measurements device based on PVDF according to claim 1, is characterized in that: the side of two metal cauls (10) is equipped with screw (14), and described metal caul (10) is drawn wire by terminal screw (13).

9. a kind of drop hammer tester impact force measurements device based on PVDF according to claim 8, is characterized in that: described wire adopts twin-core shielded conductor.

10. according to a kind of drop hammer tester impact force measurements device based on PVDF described in any one in claim 1-9, it is characterized in that: described discharge resistance is connected with PVDF piezoelectric membrane two ends, described Dynamic Data Acquiring instrument (8) is electrically connected for detection of voltage signal with described discharge resistance two ends.

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