CN102944474B - High-speed one-way tensile test method - Google Patents

Abstract

The invention discloses a high-speed one-way tensile test device and method, relates to a one-way tensile test device and method and aims to solve the problems of expensive test equipment and difficulty in obtaining a stress-strain relation curve in research on the constitutive relation of a metal material under the condition of high-speed elongation strain by using a hopkinson bar test. A coil is fixed in a coil supporting sleeve; two pull rods are connected with a bottom plate; the pull rods are detachably connected with the coil supporting sleeve and a sample fixing plate; a rigid coil limiting ring, an insulating partition plate and the coil supporting sleeve are detachably connected; and a drawing die comprises a base and a drawing rod, wherein the drawing rod is fixedly connected with the base, the drawing rod sequentially penetrates out of the coil limiting ring, the insulating partition plate, the coil framework and the coil supporting sleeve, a driving plate is arranged between the base and the rigid coil limiting ring and detachably connected with the base, and leading wires at two ends of the coil are connected with a capacitor bank which is controlled by a high-voltage switch to discharge. The high-speed one-way tensile test device and method are used for carrying out high-speed one-way tensile test on a standard tensile sample.

Description

A kind of two-forty one directional tensile test method

Technical field

The present invention relates to a kind of one directional tensile test method.

Background technology

The stress-strain curve of material is to weigh directly perceived, the most the most frequently used method of material mechanical performance.Material in routine the mechanical property under stressed or plastic yield conventionally weigh with quasi-static tensile stress-strain curve.But along with the needs of modern industry and scientific technological advance, the mechanical property performance under the working conditions such as temporary impact load, shock of metal material, building materials, superconductor, compound substance is particularly important with evaluation, more and more attracts people's attention.Strengthen outside the evaluation on bearing capacity under impact condition as the building materials such as the performance of structural integrity shape, reinforcing bar of sheet steel automobile panel under instantaneous shock condition, especially in two-forty forming process, the resistance of deformation of metal material and deformability relation are the difficult problems that scientific research and production application face.

Be configured as example with sheet metal two-forty, under the constitutive relation of material in two-forty deformation process and conventional molding condition, be essentially different, therefore can not weigh with the stress-strain curve under quasi-static tensile the performance of material.At present, the common method of the constitutive relation of research metal material under two-forty elongation strain condition is the experiment of Hopkinson separate type pull bar.The principle of Hopkinson pull bar experiment is: sample is fixed between moving lever and fixed bar, drive sample to realize high-speed stretch by the high-speed motion of moving lever, stress and strain in instrument record material deformation process in device, thus the curves of stress-strain relationship of test material under high strain rate obtained.For certain concrete two-forty manufacturing process, so far, the stress-strain curve of metal material obtains indirectly by the experiment of Hopkinson pull bar conventionally, although reacted to a certain extent the impact of two-forty deformation process on material load-bearing capacity, flow stress, can not directly provide the constitutive relation of material in concrete forming process.Hopkinson pull bar experimental facilities costliness in addition, engineering application is not general at home, implements more difficultly, is difficult to obtain curves of stress-strain relationship.

Summary of the invention

The object of this invention is to provide a kind of two-forty one directional tensile test method, adopt the constitutive relation of Hopkinson pull bar experimental study metal material under two-forty elongation strain condition to exist with solution and can not directly provide the constitutive relation of material in concrete forming process, and Hopkinson pull bar experimental facilities costliness, the very difficult problem that obtains curves of stress-strain relationship.

In order to realize foregoing invention object, the technical scheme that the present invention takes is:

A kind of two-forty one directional tensile test device of the present invention, described device comprises base plate, driving chip, coil, rigidity coil spacing ring, insulating barrier, coil rack, drawing die, coil support cover, sample fixed head and two pull bars;

The center of coil support cover is provided with the interior shoulder hole and the through hole that communicate from the bottom to top, coil is fixed in the interior shoulder hole of coil support cover, sample fixed head be arranged on coil support cover directly over, base plate be arranged on coil support cover under, two pull bars are symmetrical arranged with respect to the vertical center line of base, the lower end of two pull bars is connected with base plate, pull bar and coil support cover and sample fixed head removably connect, the lower end of coil support cover is provided with rigidity coil spacing ring, between coil support cover and rigidity coil spacing ring, be provided with insulating barrier, insulating barrier is annular, rigidity coil spacing ring, insulating barrier and coil support cover three removably connect, drawing die comprises base and stretching bar, stretching bar is fixedly connected with the center of base, stretching bar passes coil spacing ring successively, insulating barrier, coil rack and coil support cover, driving chip is arranged between base and rigidity coil spacing ring, driving chip and base removably connect, coil two ends lead-in wire is connected with capacitor group, discharged by high-voltage switch gear control capacitor group, guarantee assembling after driving chip be close on insulating barrier.

One of the present invention realizes two-forty one directional tensile test method, and described method comprises the steps:

Step 1: first standard tensile specimen surface is printed to grid, then the lower end of standard tensile sample is fixed on the first pin on the stretching bar of drawing die, the upper end of standard tensile sample is fixed on sample fixed head with the second pin, standard tensile sample side is fixed with mesh standard piece, by high-speed camera alignment criteria tensile test specimen scale distance district;

Step 2: by the charge/discharge of high-voltage switch gear control capacitor group; First make the charging of capacitor group complete, connect afterwards high-voltage switch gear, making intensity is that the moment heavy current of 20KA～200KA is passed through coil, make high-speed camera work simultaneously, sample is realized at a high speed and being stretched downwards under moment electromagnetic force, rate of extension is between 10m/s～300m/s, until break, high-speed camera records the elongation strain in each moment of sample drawing process;

Step 3: test figure is processed; The flow stress of sample in drawing process calculates by theory, and the photo analysis that the strain in each moment is recorded by high-speed camera and sample stretches obtains; Specific analytical method is as follows:

1). sample drawing process strain stress; By high-speed camera record, measure by ASAME strain grid measuring system; The high-speed camera time shutter is t, and the i starting after distortion opens photo, strain stress when deformation time is ti _ibe the strain that i that ASAME strain grid measuring system measures opens photo;

2). sample drawing process flow stress σ calculates;

The suffered power of sample is obtained by equilibrium of forces equation:

F+G=F _i+ F _fformula one

Wherein: F is electromagnetic pulse power; G is gravity, G=mg; F _ifor inertial force, F _i=ma; F _f=σ S, wherein σ is flow stress; S is the cross-sectional area in sample deformation process;

The calculating of sample acceleration a:

If the high-speed camera time shutter is t, take continuously three photo i, i+1, i+2, measures the strain stress of every photo _i, ε _i+1, ε _i+2;

: a=(ε _i+2+ ε _i+1-2 ε _i)/t ²formula two

Electromagnetic pulse power F on driving chip 3 is calculated as follows:

$F=\underset{z_2}{\overset{z_1}{\∫}}f\left(z\right)\mathrm{dz}=\frac{1}{2}\mathrm{\μ}(H_{z_1}^2-H_{z_2}^2)=\frac{1}{2\mathrm{\μ}}(B_{z_1}^2-B_{z_2}^2)$ Formula three

Wherein: for driving chip upper surface magnetic induction density; for driving chip lower surface magnetic induction density; , and obtain by magnetic induction density signal testing; F (z) is for to act on driving chip upper volume magnetic field force density along axis direction, the magnetic permeability that μ is medium; for driving chip upper surface magnetic field intensity; for driving chip lower surface magnetic field intensity;

Can obtain thus:

σ=(F+G-ma)/S formula four

Wherein S is the cross-sectional area in sample deformation process, and when cross-section variation is little, available original area replaces;

Step 4: by above-mentioned flow stress σ and the strain stress obtaining under the distortion of test specimen high speed, make stress-strain curve, i.e. σ-ε curve.

The invention has the beneficial effects as follows: one, the present invention is applied to electromagnetic forming technique in the drawing process of sample, by electromagnetic force, driving chip (copper plate) is driven, by realizing straight line unilateral stretching with the rigidly connected drawing die traction of driving chip sample.The driving force of sample drawing process is calculated by theory and the method for field signal test obtains; The deformation process computational analysis that the strain of sample is taken by high-speed camera obtains.Two, apparatus of the present invention are simple, cost is low, can fast, accurately obtain the stress-strain curve of material in two-forty deformation process.Three, the present invention is for the experiment of Hopkinson pull bar, have directly, flexibly, the advantage such as convenient and experiment condition is few, the stress-strain curve of the sample that can easily obtain multiple material, various shape in two-forty unilateral stretching process, mechanical property when also can be used for detecting and assessing material and being subject to shock load simultaneously.Four, the present invention can, to the metal blank below 2mm thickness, obtain curves of stress-strain relationship.

Brief description of the drawings

Fig. 1 is the front view of two-forty one directional tensile test device of the present invention, and Fig. 2 is sample force analysis figure.

Embodiment

Embodiment one: in conjunction with Fig. 1 and Fig. 2 explanation, a kind of two-forty one directional tensile test device, described device comprises base plate 1, driving chip 3, coil 4, rigidity coil spacing ring 6, insulating barrier 7, drawing die 9, coil support cover 10, sample fixed head 16 and two pull bars 12;

The center of coil support cover 10 is provided with the interior shoulder hole and the through hole that communicate from the bottom to top, coil 4 is fixed in the interior shoulder hole of coil support cover 10, sample fixed head 16 be arranged on coil support cover 10 directly over, base plate 1 be arranged on coil support cover 10 under, two pull bars 12 are symmetrical arranged with respect to the vertical center line of base 1, the lower end of two pull bars 12 is connected with base plate 1, pull bar 12 removably connects with coil support cover 10 and sample fixed head 16, the lower end of coil support cover 10 is provided with rigidity coil spacing ring 6, between coil support cover 10 and rigidity coil spacing ring 6, be provided with insulating barrier 7, insulating barrier 7 is annular, rigidity coil spacing ring 6, insulating barrier 7 and coil support are overlapped 10 threes and are removably connected, drawing die 9 comprises base 9-1 and stretching bar 9-2, stretching bar 9-2 is fixedly connected with the center of base 9-1, stretching bar 9-2 passes coil spacing ring 6 successively, insulating barrier 7, coil rack 8 and coil support cover 10, driving chip 3 is arranged between base 9-1 and rigidity coil spacing ring 6, driving chip 3 and base 9-1 removably connect (by the first screw 2), in the time that standard tensile sample 14 is carried out to one directional tensile test, the lower end of standard tensile sample 14 is fixed on the first pin 13 on the stretching bar 9-2 of drawing die 9, standard tensile sample 14 can move downward with driving chip 3, the upper end of standard tensile sample 14 is fixed on sample fixed head 16 and is kept transfixion with the second pin 15, coil 4 two ends lead-in wires are connected with capacitor group C, and by high-voltage switch gear K control capacitor group, C discharges, and guarantees that the driving chip 3 after assembling is close on insulating barrier 7.

Embodiment two: in conjunction with Fig. 1 explanation, described in present embodiment, coil 4 is plate coil, and the wire of coil 4 is copper conductor, and the xsect of copper conductor is rectangle, between adjacent two copper conductors, leave gap, between copper conductor and copper conductor, separate with high voltage insulating materials is coated.In present embodiment, undocumented technical characterictic is identical with embodiment one.

Embodiment three: in conjunction with Fig. 1 explanation, driving chip 3 is the copper plate of thickness 5～8mm described in present embodiment.In present embodiment, undocumented technical characterictic is identical with embodiment one.

Embodiment four: in conjunction with Fig. 1 explanation, described in present embodiment, on sample fixed head 16 and coil support cover 10, be respectively equipped with through hole with pull bar 12 opposite position places, the upper end of pull bar 12 passes respectively the through hole on coil support cover 10 and sample fixed head 16, sample fixed head 16 is fixed on pull bar 12 by the first nut 17, and coil support cover 10 is fixed on pull bar 12 by the second nut 11.In present embodiment, undocumented technical characterictic is identical with embodiment one.

Embodiment five: in conjunction with Fig. 1 explanation, rigidity coil spacing ring 6, insulating barrier 7 and coil support are overlapped 10 threes and removably connected by the second screw 5 described in present embodiment.In present embodiment, undocumented technical characterictic is identical with embodiment one.

Embodiment six: in conjunction with Fig. 1 and Fig. 2 explanation, the two-forty one directional tensile test method of present embodiment, described method comprises the steps:

Step 1: first grid is printed in standard tensile sample 14 surfaces, then the lower end of standard tensile sample 14 is fixed on the first pin 13 on the stretching bar of drawing die 9, the upper end of standard tensile sample 14 is fixed on sample fixed head 16 with the second pin 15, standard tensile sample 14 sides are fixed with mesh standard piece, by high-speed camera alignment criteria tensile sample 14 gauge length districts (being the section of standard tensile sample 14 xsect minimums);

Step 2: by the charge/discharge of high-voltage switch gear K control capacitor group C; First make capacitor group C charging complete, connect afterwards high-voltage switch gear K, making intensity is that the moment heavy current of 20KA～200KA is passed through coil, make high-speed camera work simultaneously, sample is realized at a high speed and being stretched downwards under moment electromagnetic force, rate of extension is between 10m/s～300m/s, until break, high-speed camera records the elongation strain in each moment of sample drawing process;

The driving force that sample is realized distortion is at a high speed electromagnetic force, electric current (strength of current is between 20KA～200KA) by moment by coil produces, the feature of electromagnetic pulse power is large (5MPa～350MPa), action time short (250us) of pressure, can make sample moment accelerate, thereby realize distortion (10m/s～100m/s) at a high speed;

Step 3: test figure is processed; The flow stress of sample in drawing process calculates by theory, and the photo analysis that the strain in each moment is recorded by high-speed camera and sample stretches obtains; Specific analytical method is as follows:

1). sample drawing process strain stress; By high-speed camera record, measure by ASAME strain grid measuring system; The high-speed camera time shutter is t, and the i starting after distortion opens photo, strain stress when deformation time is ti _ibe the strain that i that ASAME strain grid measuring system measures opens photo;

2). sample drawing process flow stress σ calculates;

The suffered power of sample is obtained by equilibrium of forces equation:

F+G=F _i+ F _fformula one

Wherein: F is electromagnetic pulse power; G is gravity, G=mg; F _ifor inertial force, F _i=ma; F _f=σ S, wherein σ is flow stress; S is the cross-sectional area in sample deformation process;

The calculating of sample acceleration a:

If the high-speed camera time shutter is t, take continuously three photo i, i+1, i+2, measures the strain stress of every photo _i, ε _i+1, ε _i+2;

: a=(ε _i+2+ ε _i+1-2 ε _i)/t ²formula two

Electromagnetic pulse power F on driving chip 3 is calculated as follows:

$F=\underset{z_2}{\overset{z_1}{\∫}}f\left(z\right)\mathrm{dz}=\frac{1}{2}\mathrm{\μ}(H_{z_1}^2-H_{z_2}^2)=\frac{1}{2\mathrm{\μ}}(B_{z_1}^2-B_{z_2}^2)$ Formula three

Wherein: for driving chip upper surface magnetic induction density; for driving chip lower surface magnetic induction density; and obtain by magnetic induction density signal testing; F (z) is for to act on driving chip upper volume magnetic field force density along axis direction, the magnetic permeability that μ is medium; for driving chip upper surface magnetic field intensity; for driving chip lower surface magnetic field intensity;

Can obtain thus:

σ=(F+G-ma)/S formula four

Wherein S is the cross-sectional area in sample deformation process, and when cross-section variation is little, available original area replaces;

Step 4: by above-mentioned flow stress σ and the strain stress obtaining under the distortion of test specimen high speed, make stress-strain curve, i.e. σ-ε curve.The device adopting in present embodiment is identical with embodiment one, two, three, four or five.

Capacitor group C obtains the mode of energy: first connect charging circuit, low-voltage AC (220V) boosts (can regulate) through transformer, and alternating current, through high voltage silicon rectifier stack rectification, becomes direct current, direct current charges to capacitor group C, until disconnect charging circuit after being full of again.Like this, capacitor group C just has certain energy, and energy can be provided in discharge circuit.

The present invention's material, shape used do not limited by above-mentioned example, all within the protection domain of this patent.The present invention's coil used is not limited by above-mentioned plate coil, all within this patent protection domain.Device characteristic of the present invention is not subject to the restriction of above-mentioned example, all within this patent protection domain.Other force mechanisms, if high-speed hydraulic, air pressure driving etc. are all within the protection domain of this patent.

Claims (1)

1. a two-forty one directional tensile test method, described method utilizes two-forty one directional tensile test device to realize, and described two-forty one directional tensile test device comprises base plate (1), driving chip (3), coil (4), rigidity coil spacing ring (6), insulating barrier (7), coil rack (8), drawing die (9), coil support cover (10), sample fixed head (16) and two pull bars (12), the center of coil support cover (10) is provided with the interior shoulder hole and the through hole that communicate from the bottom to top, coil (4) is fixed in the interior shoulder hole of coil support cover (10), sample fixed head (16) be arranged on coil support cover (10) directly over, base plate (1) be arranged on coil support cover (10) under, two pull bars (12) are symmetrical arranged with respect to the vertical center line of base (1), the lower end of two pull bars (12) is connected with base plate (1), pull bar (12) removably connects with coil support cover (10) and sample fixed head (16), the lower end of coil support cover (10) is provided with rigidity coil spacing ring (6), between coil support cover (10) and rigidity coil spacing ring (6), be provided with insulating barrier (7), insulating barrier (7) is annular, rigidity coil spacing ring (6), insulating barrier (7) and coil support cover (10) three removably connect, drawing die (9) comprises base (9-1) and stretching bar (9-2), stretching bar (9-2) is fixedly connected with the center of base (9-1), stretching bar (9-2) passes coil spacing ring (6) successively, insulating barrier (7), coil rack (8) and coil support cover (10), driving chip (3) is arranged between base (9-1) and rigidity coil spacing ring (6), driving chip (3) removably connects with base (9-1), coil (4) two ends lead-in wire is connected with capacitor group (C), discharged by high-voltage switch gear (K) control capacitor group (C), guarantee assembling after driving chip (3) be close on insulating barrier (7),

It is characterized in that: described method comprises the steps:

Step 1: first grid is printed in standard tensile sample (14) surface, then first pin for lower end (13) of standard tensile sample (14) is fixed on the stretching bar of drawing die (9), second pin for upper end (15) of standard tensile sample (14) is fixed on sample fixed head (16), standard tensile sample (14) side is fixed with mesh standard piece, by high-speed camera alignment criteria tensile sample (14) gauge length district;

Step 2: by the charge/discharge of high-voltage switch gear (K) control capacitor group (C); First make capacitor group (C) charge complete, connect afterwards high-voltage switch gear (K), making intensity is that the moment heavy current of 20KA～200KA is passed through coil, make high-speed camera work simultaneously, sample is realized at a high speed and being stretched downwards under moment electromagnetic force, rate of extension is between 10m/s～300m/s, until break, high-speed camera records the elongation strain in each moment of sample drawing process;

Step 3: test figure is processed; The flow stress of sample in drawing process calculates by theory, and the photo analysis that the strain in each moment is recorded by high-speed camera and sample stretches obtains; Specific analytical method is as follows:

1). sample drawing process strain stress; By high-speed camera record, measure by ASAME strain grid measuring system; The high-speed camera time shutter is t, and the i starting after distortion opens photo, strain stress when deformation time is ti _ibe the strain that i that ASAME strain grid measuring system measures opens photo;

2). sample drawing process flow stress σ calculates;

The suffered power of sample is obtained by equilibrium of forces equation:

F+G=F _i+ F _fformula one

Wherein: F is electromagnetic pulse power; G is gravity, G=mg; F _ifor inertial force, F _i=ma; F _f=σ S, wherein σ is flow stress; S is the cross-sectional area in sample deformation process;

The calculating of sample acceleration a:

If the high-speed camera time shutter is t, take continuously three photo i, i+1, i+2, measures the strain stress of every photo _i, ε _i+1, ε _i+2;

: a=(ε _i+2+ ε _i+1-2 ε _i)/t ²formula two

Electromagnetic pulse power F on driving chip (3) is calculated as follows:

$F=\underset{z_2}{\overset{z_1}{\∫}}f\left(z\right)\mathrm{dz}=\frac{1}{2}\mathrm{\μ}(H_{z_1}^2-H_{z_2}^2)=\frac{1}{2\mathrm{\μ}}(B_{z_1}^2-B_{z_2}^2)$ Formula three

Wherein: for driving chip upper surface magnetic induction density; for driving chip lower surface magnetic induction density; and obtain by magnetic induction density signal testing; F (z) is for to act on driving chip upper volume magnetic field force density along axis direction, the magnetic permeability that μ is medium; for driving chip upper surface magnetic field intensity; for driving chip lower surface magnetic field intensity;

Can obtain thus:

σ=(F+G-ma)/S formula four

Wherein S is the cross-sectional area in sample deformation process, when cross-section variation is little, replaces by original area;

Step 4: by above-mentioned flow stress σ and the strain stress obtaining under the distortion of test specimen high speed, make stress-strain curve, i.e. σ-ε curve.