CN104237031A - Synchronous measurement method of split Hopkinson pressure bar experiment based on digital images - Google Patents
Synchronous measurement method of split Hopkinson pressure bar experiment based on digital images Download PDFInfo
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- CN104237031A CN104237031A CN201410476610.9A CN201410476610A CN104237031A CN 104237031 A CN104237031 A CN 104237031A CN 201410476610 A CN201410476610 A CN 201410476610A CN 104237031 A CN104237031 A CN 104237031A
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Abstract
The invention discloses a synchronous measurement method of a split Hopkinson pressure bar experiment based on digital images. The method comprises the steps as follows: before the experiment, mark areas are made on the outer surface of one end where an incident bar and a tested piece are contacted as well as the outer surface of one end where a transmission bar and the tested piece are contacted; in the experiment process, moving images of the tested piece and the mark areas in the impact experiment process are obtained by a high-speed camera; through trace analysis of deformation of the mark area, strain of the tested piece as well as the incident bar and the transmission bar at the two ends of the tested piece is further obtained; and according to the principle of the Hopkinson pressure bar experiment, , stress of the two ends of the tested piece is calculated based on strain of the two bars; and further, through the novel experimental technology based on the digital images, the strain of a test piece and the stress of two ends of the test piece can be obtained synchronously.
Description
Technical field
The present invention relates to split hopkinson press bar experiment, be specifically related to the method for synchronously measuring that a kind of split hopkinson press bar based on digital picture is tested.
Background technology
Split hopkinson press bar technology is a kind of experimental technique of test material dynamic mechanical, is developed so far and is widely used in the Mechanics Performance Testing of construction material under high strain-rate.First traditional split hopkinson press bar experimental technique sticks foil gauge on incident bar and transmission bar, and the signal that then experimentally foil gauge gathers in process converts and obtains the stress-strain data of test specimen.Owing to being recorded into ejected wave, reflection wave is often not identical with the time of transmitted wave, so the start time of these three waveforms is artificial selections in data handling, if the inconsistent error that will cause stress-strain data of the start time chosen, especially test reach the chronic material of stress equilibrium (as soft material etc.) needed for some time, the start time choosing transmitted wave and reflection wave becomes comparatively difficulty, the synchronism of waveform cannot be ensured, also just really cannot realize the synchro measure to test specimen strain and two ends stress thereof.Also have scholar to propose to embed quartz piezoelectric wafer to obtain test specimen two ends stress in incident, transmission bar end, although achieve the synchro measure of two ends stress like this, strain data is still gathered by foil gauge, and its synchronism does not improve.
Summary of the invention
In order to overcome shortcoming that prior art exists with not enough, the invention provides the method for synchronously measuring that the split hopkinson press bar based on digital picture is tested.
The present invention adopts following technical scheme:
Based on the method for synchronously measuring that the split hopkinson press bar of digital picture is tested, comprise
Before experiment, to contact the outside surface of one end with test specimen at incident bar and make marked region at transmission bar to contact one end outside surface with test specimen;
In experimentation, comprised the moving image of test specimen and marked region by high-speed camera acquisition impact experiment process;
By the distortion of trace analysis marked region, obtain test specimen and incident bar, the strain of transmission bar at test specimen two ends further;
According to the principle of Hopkinson pressure bar experiment, by the strain of two bars, calculate the stress at test specimen two ends.
Describedly obtain the distortion of marked region according to graphical analysis, obtain test specimen and incident bar, transmission bar further in the strain at test specimen two ends, be specially:
At the marked region of incident bar, select A, B 2 point, select C, D 2 point at the marked region of transmission bar, wherein B, C are two points close to test specimen, are wherein two points away from test specimen between A, D;
Obtaining the increment of C, D 2 distances by analyzing the marked region moving image of transmission bar, then obtaining divided by the initial distance between C, D transmission bar to contact one end strain with test specimen with increment at 2;
Obtained the increment of A, B 2 distances by the moving image analyzing incident bar marked region, then obtain divided by the initial distance between A, B incident bar to contact one end strain with test specimen with this increment at 2;
Due to B, C point all from test specimen very close to, the increment that graphical analysis obtains these 2 distances is similar to regards the length increment of test specimen along impact direction as, just releases the strain of test specimen with it divided by test specimen original length.
According to the principle of Hopkinson pressure bar experiment, by the strain of two bars, calculate the stress at test specimen two ends, be specially:
One-dimensional stress is utilized to suppose, the elastic modulus strain of transmission bar or incident bar being multiplied by transmission bar or incident bar obtains the stress of transmission bar or incident bar marked region, then the product of the cross-sectional area of they and transmission bar or incident bar is obtained the stress at test specimen two ends divided by the cross-sectional area of test specimen.
Described marked region comprises gauge point or speckle.
Beneficial effect of the present invention:
Compared with traditional split hopkinson press bar experimental technique, the new experimental technique based on digital picture proposed by the invention can synchronously obtain the strain of test specimen and the stress at two ends thereof.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of the method for synchronously measuring that a kind of split hopkinson press bar based on digital picture of the present invention is tested;
Fig. 2 is the high-speed camera shooting area schematic diagram in the embodiment of the present invention.
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.
Embodiment
The present embodiment selects the length of incident bar 1 to be 320cm, the length of transmission bar 2 is 200cm, the cross section of incident bar and transmission bar is circular, its diameter is 74mm, is all steel poles, and high-speed camera adopts Phantomv1610 system, test specimen 3 is the cylinder type steel fiber concretes living through repeat impact, its diameter is 70.2mm, is highly the shooting area that 4 in 31.6mm, Fig. 1 represents high-speed camera.
Based on the method for synchronously measuring that the split hopkinson press bar of digital picture is tested, comprise
As shown in Figure 1, before experiment, contact the outside surface of one end at incident bar 1 with test specimen 3 in advance, and make marked region at transmission bar 2 to contact one end outside surface with test specimen 3, marked region is made up of speckle, and speckle particle size is determined by graphical analysis precision.The process of concrete setting marked region is: on incident bar and transmission bar, be about 5cm from end face before experiment and carry out mark line at a distance, then by clean for the rod member surface cleaning from mark line to end face part, coated matte dirty oil paint is as speckle, and the height of speckle regions is about 2cm.
The concrete width of speckle regions can not be too large or too little, and too conference causes the strain to this regional analysis obtains can not be similar to the strain regarding rod end regional area as, too little, and error may be caused excessive.If what analyze is gauge point, every root bar have two gauge points at least, wherein have at least one be with test specimen closely, another be also from test specimen can not too close to or too far away, the strain to this regional analysis obtains too far can be caused can not to be similar to the strain regarding rod end regional area as, too closely error then may to be caused excessive.
In experimentation, bullet is with the velocity shock incident bar of 13m/s, obtain in impact experiment process by high-speed camera, comprise the moving image of test specimen and marked region, described high-speed camera is arranged on just to the dead ahead of test specimen, can know and photograph test specimen and marked region, the shooting area 4 of Fig. 1 high speed video camera.
By the distortion of trace analysis marked region, obtain test specimen and incident bar, the strain of transmission bar at test specimen two ends further;
As shown in Figure 2, at the marked region of incident bar, select A, B 2 point, select C, D 2 point at the marked region of transmission bar, wherein B, C are two points close to test specimen, and A, D are then from the point of two away from test specimen, in the present embodiment, AB distance is about 2cm, and CD distance is about 1.3cm, and B point and C point respectively distance test specimen end face are about 2mm.
Obtaining the increment of C, D 2 distances by analyzing the marked region moving image of transmission bar, then obtaining divided by the initial distance between C, D transmission bar to contact one end strain with test specimen with increment at 2;
Obtained the increment of A, B 2 distances by the moving image analyzing incident bar marked region, then obtain divided by the initial distance between A, B incident bar to contact one end strain with test specimen with this increment at 2;
Due to B, C point all from test specimen very close to, the increment that graphical analysis obtains these 2 distances is similar to regards the length increment of test specimen along impact direction as, just releases the strain of test specimen with it divided by test specimen original length.
One-dimensional stress is utilized to suppose, the elastic modulus being multiplied by transmission bar or incident bar near the strain of test specimen one end is obtained the stress of transmission bar or incident bar marked region, then the product of the cross-sectional area of they and transmission bar or incident bar is obtained the stress at test specimen two ends divided by the cross-sectional area of test specimen.
Because the stress at test specimen strain and two ends is all obtain from the image analysis of same high-speed photography, therefore they are synchronous.
Experimental result shows, test specimen and transmission bar, the strain waveform of incident bar near test specimen region can be obtained preferably based on the synchronous measurement technique of test specimen strain and two ends stress in the split hopkinson press bar experiment of digital picture, compared with the traditional SHPB experimental technique based on foil gauge signal, main advantage is the synchronism without the need to considering the time in the aftertreatment of foil gauge signal, and can realize the assessment of test specimen two ends stress equilibrium situation.
Above-described embodiment is the present invention's preferably embodiment; but embodiments of the present invention are not limited by the examples; change, the modification done under other any does not deviate from Spirit Essence of the present invention and principle, substitute, combine, simplify; all should be the substitute mode of equivalence, be included within protection scope of the present invention.
Claims (4)
1., based on the method for synchronously measuring that the split hopkinson press bar of digital picture is tested, it is characterized in that, comprise
Before experiment, to contact the outside surface of one end with test specimen at incident bar and make marked region at transmission bar to contact one end outside surface with test specimen;
In experimentation, comprised the moving image of test specimen and marked region by high-speed camera acquisition impact experiment process;
By the distortion of trace analysis marked region, obtain test specimen and incident bar, the strain of transmission bar at test specimen two ends further;
According to the principle of Hopkinson pressure bar experiment, by the strain of two bars, calculate the stress at test specimen two ends.
2. method according to claim 1, is characterized in that, describedly obtains the distortion of marked region according to graphical analysis, obtains test specimen and incident bar, transmission bar further in the strain at test specimen two ends, is specially:
At the marked region of incident bar, select A, B 2 point, select C, D 2 point at the marked region of transmission bar, wherein B, C are two points close to test specimen, are wherein two points away from test specimen between A, D;
Obtaining the increment of C, D 2 distances by analyzing the marked region moving image of transmission bar, then obtaining divided by the initial distance between C, D transmission bar to contact one end strain with test specimen with increment at 2;
Obtained the increment of A, B 2 distances by the moving image analyzing incident bar marked region, then obtain divided by the initial distance between A, B incident bar to contact one end strain with test specimen with this increment at 2;
Due to B, C point all from test specimen very close to, the increment that graphical analysis obtains these 2 distances is similar to regards the length increment of test specimen along impact direction as, just releases the strain of test specimen with it divided by test specimen original length.
3. method according to claim 2, is characterized in that, according to the principle of Hopkinson pressure bar experiment, by the strain of two bars, calculates the stress at test specimen two ends, is specially:
One-dimensional stress is utilized to suppose, the elastic modulus strain of transmission bar or incident bar being multiplied by transmission bar or incident bar obtains the stress of transmission bar or incident bar marked region, then the product of the cross-sectional area of they and transmission bar or incident bar is obtained the stress at test specimen two ends divided by the cross-sectional area of test specimen.
4. method according to claim 1, is characterized in that, described marked region comprises gauge point or speckle.
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Cited By (5)
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| CN106442111A (en) * | 2016-10-14 | 2017-02-22 | 安徽理工大学 | Multistage bullet firing device of Hopkinson pressure bar |
| CN108344649A (en) * | 2018-02-07 | 2018-07-31 | 西北工业大学 | A kind of dynamic double-shaft two-way tensile 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 |
| CN111855343A (en) * | 2020-06-28 | 2020-10-30 | 东南大学 | Rock joint dynamic mechanical property and wave propagation rule indoor experimental device and method |
| CN113533047A (en) * | 2021-07-15 | 2021-10-22 | 天津大学 | Method for obtaining dynamic tensile stress-strain curve of rock |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108344649A (en) * | 2018-02-07 | 2018-07-31 | 西北工业大学 | A kind of dynamic double-shaft two-way tensile loading device and experimental method |
| 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 |
| CN111855343A (en) * | 2020-06-28 | 2020-10-30 | 东南大学 | Rock joint dynamic mechanical property and wave propagation rule indoor experimental device and method |
| CN113533047A (en) * | 2021-07-15 | 2021-10-22 | 天津大学 | Method for obtaining dynamic tensile stress-strain curve of rock |
| 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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