CN102841141A - Novel material dynamic mechanics performance testing method and device thereof - Google Patents

Abstract

The invention discloses a method for measuring the dynamic mechanical properties of a material, which includes: 1) sending a stress pulse wave with a certain stress to the sample, when the stress wave propagates inside the sample, due to the lateral expansion and lateral inertia effect, the particle of the sample is generated The radial velocity v _R of the particle along the direction perpendicular to the propagation direction of the stress wave is measured by a _velocimeter , and the stress wave passing through the sample is measured by a pressure sensor; 2) The collected radial motion velocity v _R measured by the velocimeter and the pressure measured by the pressure sensor are calculated to obtain the radial and longitudinal strain relationship of the material sample. The invention also discloses a device for measuring dynamic mechanical properties of materials. The present invention combines particle velocity measurement and pressure measurement to directly obtain the stress-strain relationship of the sample, reducing errors caused by time translation. At the same time, the measuring system can be made more compact.

Description

A new method and device for testing dynamic mechanical properties of materials

technical field

The invention relates to a new method and device for testing dynamic mechanical properties of materials.

Background technique

The dynamic mechanical behavior of materials is extremely important for the research on the performance of structures such as penetration resistance and impact collision. The traditional Slip Hopkinson Pressure Bar (SHPB) technique is an effective experimental method for measuring the stress-strain relationship of materials under high strain rate conditions, and has been widely used in the dynamic mechanical behavior of materials under uniaxial impact loads. Research. Its prototype comes from a device for testing transient impulse stress invented by Hopkinson in 1914. Later, Kolsky, David and Hunter made substantial improvements to this device. Stress pulses are produced by impact or detonation of explosives.

Modern SHPBs are all developed on the basis of Kolsky's work. The SHPB system is mainly composed of an incident bullet, an input rod and an output rod. The material sample is placed coaxially between the input and output rods. When an incident bullet hits the input rod with velocity v a stress pulse (incident wave) is generated and starts propagating in the input rod. When encountering a material sample, due to the mismatch in shape and impedance, part of the stress wave is reflected back to the input rod (reflected wave), and the other part is transmitted through the sample to the output rod (transmitted wave). With this setup, the stress-strain relationship of the material under this impact load can be measured by measuring the incident and reflected wave strains on the input rod and the transmitted wave strain on the output rod.

The experimental approach of SHPB is based on the following two assumptions:

(1) One-dimensional stress condition. This requires that the diameter of the rod is much smaller than the wavelength, ignoring the lateral inertia effect of the sample;

(2) The stress and strain distribution of the sample is uniform, and the fluctuation effect of the sample and the friction effect of the end surface are ignored.

应变ε(t)和应力σ(t)历程，Let the incident wave and reflected wave strains in the incident rod be ε _I (t) and ε _R (t) respectively, and the transmitted wave strain in the transmission rod be ε _T (t). According to the one-dimensional stress wave theory, it can be calculated simultaneously The stress and velocity at the two end faces of the sample can be used to obtain the strain rate during the deformation process of the sample

Strain ε(t) and stress σ(t) histories,

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; L</span>}}{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; ,</span>$

$\mathrm{<span\; class="notranslate">\; \&sigma;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; AE</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; .</span>$

Among them, C ₀ , L, A and A ₀ are respectively the elastic wave velocity of the rod, the original length of the sample, the cross-sectional area of the rod and the cross-sectional area of the sample. From this, the dynamic stress, strain rate and strain time history of the sample can be obtained, and the corresponding relationship between the three can be directly obtained by using time as a parameter.

The principle of SHPB experiment is based on the assumption of one-dimensional stress, and the experimental system is relatively complicated. The stress, strain and strain rate of the specimen are obtained by measuring the incident, reflected and transmitted strain waveforms. During data processing, the measured three strain waveforms need to be shifted in time to ensure that they have the same time starting point. However, it is usually difficult to ensure that the measured strain waveforms have the same starting point in time. In addition, due to the influence of the lateral dimension of the rod, the dispersion effect of the wave during propagation will cause changes in the waveform and also cause errors in data processing.

Contents of the invention

In view of the problems existing in the prior art, the purpose of the present invention is to provide a method and device for measuring the dynamic mechanical properties of materials, which can directly obtain the stress-strain relationship of the sample, reduce the error caused by time translation, and at the same time make the measurement The system is more compact.

A kind of material dynamic mechanical property measuring method of the present invention comprises:

1) Send a stress pulse wave with a certain stress to the sample. When the stress wave propagates inside the sample, due to the effect of lateral expansion and lateral inertia, the particle of the sample will move along the radial direction perpendicular to the propagation direction of the stress wave. Velocity v _R , the radial motion velocity v _R of the particle is measured by a velocimeter, and the stress wave passing through the sample is measured by a pressure sensor;

2) The collected radial motion velocity v _R measured by the velocimeter and the pressure measured by the pressure sensor are calculated to obtain the radial and longitudinal strain relationship of the material sample:

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; wxya</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; -</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; t</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}\mathrm{<span\; class="notranslate">\; dt</span>}$

ε _l is the value measured by the pressure sensor;

Among them, ε _l (t) is the radial strain, ε _l is the longitudinal strain, t _C is the moment when the sample begins to enter the plastic deformation stage, v is Poisson's ratio, R is the radius of the sample, and R _t is the test time at time t. sample radius.

A kind of material dynamic mechanical property measuring device of the present invention comprises:

The stress pulse generating unit generates stress pulses with predetermined intensity and pulse width, and sends them to the sample to be tested;

A pressure measurement unit for measuring stress waves passing through the sample;

a velocity measuring unit, used to measure the radial movement velocity v _R generated by the sample particle along the direction perpendicular to the propagation direction of the stress wave;

a data collection unit, configured to collect information collected by the pressure measurement unit and the speed measurement unit;

The data processing unit obtains the radial strain and longitudinal strain of the sample according to the radial and longitudinal strain relationship of the sample:

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; wxya</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; -</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; t</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}\mathrm{<span\; class="notranslate">\; dt</span>}$

ε _l is the value measured by the pressure sensor;

Among them, ε _l (t) is the radial strain, ε _l is the longitudinal strain, t _C is the moment when the sample begins to enter the plastic deformation stage, v is Poisson's ratio, R is the radius of the sample, and R _t is the test time at time t. sample radius.

Preferably, the pressure measurement unit is a pressure sensor.

Preferably, the speed measurement unit is a speedometer.

The present invention combines particle velocity measurement and pressure measurement to directly obtain the stress-strain relationship of the sample, reducing errors caused by time translation. At the same time, the measuring system can be made more compact.

Description of drawings

Fig. 1 is the structural representation of the embodiment of the present invention;

Fig. 2 is a comparative diagram of the dynamic stress-strain relationship of samples measured by the present invention and the traditional SHPB method.

Detailed ways

The experimental principle of the present invention is: when the stress wave propagates inside the sample, due to the lateral expansion and lateral inertia effect, the radial motion velocity v _R of the particle will be generated. The particle velocity is measured by a high-precision velocimeter, and through The stress waveform of the passing sample is measured by a high-sensitivity pressure sensor. The stress-strain relationship of the sample is obtained by processing the data.

As shown in FIG. 1 , the present invention includes: a stress pulse generation unit 1 , a pressure measurement unit 2 , a velocity measurement unit 3 , a data collection unit 4 , a data processing unit 5 and a stress wave absorption unit 7 .

The stress pulse generation unit 1 is used to generate a stress pulse with predetermined intensity and pulse width, and send it to the sample 6 to be tested.

The pressure measurement unit 2 is used to measure the stress wave passing through the sample 6 .

The velocity measurement unit 3 is used to measure the radial movement velocity v _R generated by the mass point of the sample 6 along the direction perpendicular to the propagation direction of the stress wave.

The data collection unit 4 is used to collect the information collected by the pressure measurement unit 2 and the speed measurement unit 3 .

The data processing unit 5 obtains the radial strain and the longitudinal strain of the sample 6 according to the radial and longitudinal strain relationships of the sample 6:

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; wxya</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; -</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; t</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}\mathrm{<span\; class="notranslate">\; dt</span>}$

ε _l is the value measured by the pressure sensor;

Among them, ε _l (t) is the radial strain, ε _l is the longitudinal strain, t _C is the moment when the sample begins to enter the plastic deformation stage, v is Poisson's ratio, R is the radius of the sample, and R _t is the test time at time t. sample radius.

Finally, the stress wave transmitted through the sample 6 and measured is absorbed by the stress wave absorbing unit 7 .

In the embodiment of the present invention, the pressure measurement unit 2 is a high-sensitivity pressure sensor, the speed measurement unit 3 is a high-precision velocimeter, the data collection unit 4 is a data acquisition card, and the data processing unit 5 is a computer.

In order to make the measurement more accurate, the length-to-diameter ratio of sample 6 should be as large as possible, for example, more than 5/1. In this way, the end surface friction effect of the sample can be ignored, and it can be considered that sample 6 is in a one-dimensional stress state. The wave dispersion effect can be ignored, so it can be considered that the stress waveform measured on the right end surface of sample 6 is the same as the stress waveform at the measurement position of the velocimeter.

The strain rate and strain history of the sample 6 can be obtained through the above method, combined with the measured pressure waveform, the dynamic stress-strain relationship of the sample 6 can be obtained.

As shown in FIG. 2 , it is a comparative diagram of the dynamic stress-strain relationship of sample 6 measured by the present invention and the traditional SHPB method. The aspect ratio of sample 6 is 1:1, and the material of sample 6 is aluminum. It can be seen from the measurement results that the experimental results obtained by this measurement method are consistent with the measurement results of the traditional SHPB method.

Therefore, the present invention provides a new method with simpler structure and more convenient measurement for the measurement of dynamic stress-strain relationship of materials.

Claims (4)

1. A method for measuring dynamic mechanical properties of materials, comprising: 1) Send a stress pulse wave with a certain stress to the sample. When the stress wave propagates inside the sample, due to the effect of lateral expansion and lateral inertia, the particle of the sample will move along the radial direction perpendicular to the propagation direction of the stress wave. Velocity v _R , the radial motion velocity v _R of the particle is measured by a velocimeter, and the stress wave passing through the sample is measured by a pressure sensor; 2) The collected radial motion velocity v _R measured by the velocimeter and the pressure measured by the pressure sensor are calculated to obtain the radial and longitudinal strain relationship of the material sample: ${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; wxya</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; -</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; t</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}\mathrm{<span\; class="notranslate">\; dt</span>}$ ε _l is the value measured by the pressure sensor; Among them, ε _l (t) is the radial strain, ε _l is the longitudinal strain, t _C is the moment when the sample begins to enter the plastic deformation stage, v is Poisson's ratio, R is the radius of the sample, and R _t is the test time at time t. sample radius. 2. A device for measuring dynamic mechanical properties of materials, comprising: A stress pulse generating unit that generates stress pulses of predetermined intensity and pulse width and sends them to the sample to be tested; A pressure measurement unit for measuring stress waves passing through the sample; a velocity measuring unit, used to measure the radial movement velocity v _R generated by the sample particle along the direction perpendicular to the propagation direction of the stress wave; a data collection unit, configured to collect information collected by the pressure measurement unit and the speed measurement unit; The data processing unit obtains the radial strain and the longitudinal strain of the sample according to the radial and longitudinal strain relationships of the sample: ${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; wxya</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; -</span>\underset{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; t</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}\mathrm{<span\; class="notranslate">\; dt</span>}$ ε _l is the value measured by the pressure sensor; Among them, ε _l (t) is the radial strain, ε _l is the longitudinal strain, t _C is the moment when the sample begins to enter the plastic deformation stage, v is Poisson's ratio, R is the radius of the sample, and R _t is the test time at time t. sample radius. 3. The device of claim 2, wherein the pressure measuring unit is a pressure sensor. 4. The device of claim 2, wherein the speed measuring unit is a speedometer.

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