CN104237031B - The method for synchronously measuring of split hopkinson press bar based on digital picture experiment - Google Patents
The method for synchronously measuring of split hopkinson press bar based on digital picture experiment Download PDFInfo
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- CN104237031B CN104237031B CN201410476610.9A CN201410476610A CN104237031B CN 104237031 B CN104237031 B CN 104237031B CN 201410476610 A CN201410476610 A CN 201410476610A CN 104237031 B CN104237031 B CN 104237031B
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Abstract
The invention discloses the method for synchronously measuring of split hopkinson press bar based on digital picture experiment, before experiment, contact the outer surface of one end with test specimen at incident bar and contact the outer surface making marked region of one end at transmission bar with test specimen；In experimentation, during obtaining impact experiment by high-speed camera, include the moving image of test specimen and marked region；By the deformation of trace analysis marked region, obtain test specimen and incident bar, the transmission bar strain at test specimen two ends further；According to the principle of Hopkinson pressure bar experiment, by the strain of two bars, it is calculated the stress at test specimen two ends.Based on digital picture new experimental technique proposed by the invention can synchronize the stress at strain and the two ends thereof obtaining test specimen.
Description
Technical field
The present invention relates to split hopkinson press bar experiment, be specifically related to a kind of separation based on digital picture
The method for synchronously measuring of formula Hopkinson pressure bar experiment.
Background technology
Split hopkinson press bar technology is a kind of experimental technique testing material dynamic mechanical performance, development
It is widely used in engineering material Mechanics Performance Testing under high strain-rate.Traditional separate type is suddenly
First Pu Jinsen depression bar experimental technique sticks foil gauge, then according to experimentation on incident bar and transmission bar
The signal conversion that middle foil gauge is gathered obtains the stress-strain data of test specimen.Owing to being recorded into ejected wave, reflection
The time of ripple and transmitted wave often differs, so the start time of these three waveform is people in data handling
For select, if the inconsistent error that may result in stress-strain data of the start time chosen, especially
When reaching stress non-uniform time the longest material (such as soft material etc.) needed for testing some, choose transmitted wave
More difficulty is become, it is impossible to ensure the synchronicity of waveform with the start time of echo, the most just cannot be really real
Now to test specimen strain and the synchro measure of two ends stress thereof.Also have scholar propose incident, transmission bar end is embedding
Enter quartz piezoelectric wafer to obtain test specimen two ends stress, although so achieving the synchro measure of two ends stress,
But strain data is still gathered by foil gauge, its synchronicity is improved.
Summary of the invention
In order to overcome shortcoming that prior art exists with not enough, the present invention provides separate type based on digital picture
The method for synchronously measuring of Hopkinson pressure bar experiment.
The present invention adopts the following technical scheme that
A kind of method for synchronously measuring of split hopkinson press bar based on digital picture experiment, including
Before experiment, contact the outer surface of one end with test specimen at incident bar and connect with test specimen at transmission bar
The outer surface touching one end makes marked region；
In experimentation, during obtaining impact experiment by high-speed camera, include test specimen and mark zone
The moving image in territory；
By the deformation of trace analysis marked region, obtain test specimen and incident bar further, transmission bar exists
The strain at test specimen two ends；
According to the principle of Hopkinson pressure bar experiment, by the strain of two bars, it is calculated test specimen two ends
Stress.
The described deformation obtaining marked region according to graphical analysis, obtain further test specimen and incident bar,
Transmission bar in the strain at test specimen two ends, particularly as follows:
At the marked region of incident bar, selecting A, B 2 point, the marked region at transmission bar selects C, D two
Point, wherein B, C are two points close to test specimen, are wherein two away from test specimen between A, D
Individual point；
The increment of 2 distances of C, D is obtained, then with increasing by analyzing the marked region moving image of transmission bar
Amount obtains transmission bar divided by the initial distance between C, D at 2 and contacts the strain of one end with test specimen；
Obtain the increment of 2 distances of A, B by analyzing the moving image of incident bar marked region, then use this
Individual increment obtains incident bar divided by the initial distance between A, B at 2 and contacts the strain of one end with test specimen；
Owing to B, C point is all close from test specimen, graphical analysis obtains the increment approximation of these 2 distances and regards test specimen as
Along the length increment of impact direction, just release the strain of test specimen divided by test specimen original length with it.
According to the principle of Hopkinson pressure bar experiment, by the strain of two bars, it is calculated test specimen two ends
Stress, particularly as follows:
Utilize one-dimensional stress it is assumed that the strain of transmission bar or incident bar to be multiplied by the elasticity of transmission bar or incident bar
Modulus obtains transmission bar or the stress of incident bar marked region, then by them with transmission bar or incident bar transversal
The product of area obtains the stress at test specimen two ends divided by the cross-sectional area of test specimen.
Described marked region includes labelling point or speckle.
Beneficial effects of the present invention:
Compared with traditional split hopkinson press bar experimental technique, proposed by the invention based on digitized map
The new experimental technique of picture can synchronize the stress at strain and the two ends thereof obtaining test specimen.
Accompanying drawing explanation
Fig. 1 is the synchro measure side of a kind of split hopkinson press bar based on digital picture of present invention test
The schematic diagram of method；
Fig. 2 is the high-speed camera shooting area schematic diagram in the embodiment of the present invention.
Detailed description of the invention
Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but the enforcement of the present invention
Mode is not limited to this.
Embodiment
The present embodiment selects a length of 320cm of incident bar 1, a length of 200cm of transmission bar 2, incident bar
And the cross section of transmission bar is circular, its diameter is 74mm, is all steel pole, and high-speed camera uses Phantom
V1610 system, test specimen 3 is the cylinder type steel fiber concrete living through repeat impact, and it is a diameter of
70.2mm, height is 31.6mm, the shooting area of 4 expression high-speed motion picture cameras in Fig. 1.
A kind of method for synchronously measuring of split hopkinson press bar based on digital picture experiment, including
As it is shown in figure 1, before Shi Yan, contact the outer surface of one end at incident bar 1 with test specimen 3 in advance,
And contact the outer surface of one end with test specimen 3 at transmission bar 2 and make marked region, marked region is by speckle
Constitute, depending on speckle particle size is by graphical analysis precision.The concrete process setting marked region as: test
Before on incident bar and transmission bar, at a distance carry out mark line from end face about 5cm, then will be from mark line to end face
The rod member surface cleaning of part is clean, and coated matte dirty oil paint is as speckle, the height of speckle regions about 2cm.
The concrete width of speckle regions can not be the biggest or the least, and too conference causes obtain this regional analysis to answer
Change can not approximate the strain regarding rod end regional area as, the least, and error may be caused excessive.If analyzed
It is labelling point, at least two labelling points on every bar, at least one of which is with test specimen closely,
Another be also from test specimen can not too close to or too remote, the farthest can cause the strain that this regional analysis is obtained can not
Approximation regards the strain of rod end regional area as, too closely error then may be caused excessive.
In experimentation, bullet, with the velocity shock incident bar of 13m/s, obtains impact by high-speed camera real
During testing, including test specimen and the moving image of marked region, it is the most right that described high-speed camera is arranged on
The dead ahead of test specimen, can clearly photograph test specimen and marked region, Fig. 1 high speed video camera
Shooting area 4.
By the deformation of trace analysis marked region, obtain test specimen and incident bar further, transmission bar exists
The strain at test specimen two ends；
As in figure 2 it is shown, at the marked region of incident bar, select A, B 2 point, at the marked region of transmission bar
Selecting C, D 2 point, wherein B, C are two points close to test specimen, and A, D are then from test specimen
Two points farther out, in the present embodiment, AB distance about 2cm, CD distance about 1.3cm, B point and C point
Distance test specimen end face about 2mm respectively.
The increment of 2 distances of C, D is obtained, then with increasing by analyzing the marked region moving image of transmission bar
Amount obtains transmission bar divided by the initial distance between C, D at 2 and contacts the strain of one end with test specimen；
Obtain the increment of 2 distances of A, B by analyzing the moving image of incident bar marked region, then use this
Individual increment obtains incident bar divided by the initial distance between A, B at 2 and contacts the strain of one end with test specimen；
Owing to B, C point is all close from test specimen, graphical analysis obtains the increment approximation of these 2 distances and regards test specimen as
Along the length increment of impact direction, just release the strain of test specimen divided by test specimen original length with it.
Utilize one-dimensional stress it is assumed that the springform of transmission bar or incident bar is multiplied by the strain that will be close to test specimen one end
Measure transmission bar or the stress of incident bar marked region, then by them and transmission bar or the cross section of incident bar
Long-pending product obtains the stress at test specimen two ends divided by the cross-sectional area of test specimen.
Owing to the stress of test specimen strain and two ends is all to analyze to obtain from the image of same high-speed photography,
Therefore they are to synchronize.
Test result indicate that, test specimen strain and two in split hopkinson press bar based on digital picture experiment
The synchronous measurement technique of end stress can preferably obtain test specimen and transmission bar, incident bar answering near test specimen region
Become waveform, compared with traditional SHPB experimental technique based on foil gauge signal, main advantage is that without
The post processing of foil gauge signal considers the synchronicity of time, and test specimen two ends stress equilibrium situation can be realized
Assessment.
Above-described embodiment is the present invention preferably embodiment, but embodiments of the present invention are not by described reality
Execute the restriction of example, the change made under other any spirit without departing from the present invention and principle, modification,
Substitute, combine, simplify, all should be the substitute mode of equivalence, within being included in protection scope of the present invention.
Claims (2)
1. the method for synchronously measuring of split hopkinson press bar based on a digital picture experiment, it is characterised in that include
Before experiment, contact the outer surface of one end with test specimen at incident bar and contact the outer surface of one end with test specimen at transmission bar and make marked region；
In experimentation, during obtaining impact experiment by high-speed camera, include the moving image of test specimen and marked region；
By the deformation of trace analysis marked region, obtain test specimen and incident bar, the transmission bar strain at test specimen two ends further；
According to the principle of Hopkinson pressure bar experiment, by the strain of two bars, it is calculated the stress at test specimen two ends；
The described deformation by trace analysis marked region, obtains test specimen and incident bar, the transmission bar strain at test specimen two ends further, particularly as follows:
At the marked region of incident bar, selecting A, B 2 point, the marked region at transmission bar selects C, D 2 point, and wherein B, C are two points close to test specimen, and wherein A, D are two points away from test specimen；
Obtain the increment of 2 distances of C, D by analyzing the marked region moving image of transmission bar, then obtain transmission bar with increment divided by the initial distance between C, D at 2 and contact the strain of one end with test specimen；
Obtain the increment of 2 distances of A, B by analyzing the moving image of incident bar marked region, then obtain incident bar with this increment divided by the initial distance between A, B at 2 and contact the strain of one end with test specimen；
Owing to B, C point is all close from test specimen, graphical analysis obtains the increment approximation of these 2 distances and regards the test specimen length increment along impact direction as, just releases the strain of test specimen divided by test specimen original length with it；
According to the principle of Hopkinson pressure bar experiment, by the strain of two bars, it is calculated the stress at test specimen two ends, particularly as follows:
One-dimensional stress is utilized to assume, the strain of transmission bar or incident bar is multiplied by the elastic modelling quantity of transmission bar or incident bar and obtains transmission bar or the stress of incident bar marked region, then they products with transmission bar or the cross-sectional area of incident bar are obtained divided by the cross-sectional area of test specimen the stress at test specimen two ends.
Method the most according to claim 1, it is characterised in that described marked region includes labelling point or speckle.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106442111B (en) * | 2016-10-14 | 2021-02-09 | 安徽理工大学 | Hopkinson bar multistage bullet launching device |
| CN108344649B (en) * | 2018-02-07 | 2020-11-20 | 西北工业大学 | Dynamic biaxial tension loading device and experimental method |
| CN110501218A (en) * | 2019-09-27 | 2019-11-26 | 天津大学 | For measuring the Hopkinson pressure bar system of strain rate constitutive relation in ultra-soft material |
| CN111855343B (en) * | 2020-06-28 | 2023-01-17 | 东南大学 | Rock joint dynamic mechanical property and wave propagation rule indoor experimental device and method |
| CN113533047B (en) * | 2021-07-15 | 2022-09-30 | 天津大学 | Method for obtaining dynamic tensile stress-strain curve of rock |
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2014
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| EP1065492A2 (en) * | 1999-07-02 | 2001-01-03 | Sumitomo Rubber Industries Ltd. | Split Hopkinson bar testing apparatus and method |
| CN101430251A (en) * | 2008-12-25 | 2009-05-13 | 中南大学 | Vehicle component real object collision test method and tester |
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| CN102135480A (en) * | 2010-12-17 | 2011-07-27 | 北京理工大学 | System and method for performing impact loading on micro test piece and measuring dynamic mechanical property |
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