CN109870354A - Round metal bars sample is uniaxially stretched elongation after fracture method for automatic measurement - Google Patents
Round metal bars sample is uniaxially stretched elongation after fracture method for automatic measurement Download PDFInfo
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Abstract
The invention discloses the method for automatic measurement that a kind of round metal bars sample is uniaxially stretched elongation after fracture, belong to metal material mechanics technical field of performance test, this method is under the premise of known materials elasticity modulus and Poisson's ratio, only need to measure and record the elongation between gages amount and load value at pole sample tension failure moment, pole sample outer profile curve of having no progeny is acquired using optical means simultaneously, pole sample is obtained by flexible deformation analytical calculation and is uniaxially stretched elongation after fracture.This method accurately deducts elastic part, and fracture position automatic implementation shifts method within the scope of gauge length without identifying, to accurately obtain elongation after fracture.Compared with existing manual measurement technology, scribing line and the fixed cumbersome measurement links such as sample of having no progeny is saved, and improve measurement accuracy, be of great significance for metal material mechanics performance test.
Description
Technical field
The present invention relates to metal material mechanics performance tests, and in particular to round metal bars sample is uniaxially stretched elongation after fracture
Method for automatic measurement.
Background technique
In metal material mechanics performance, elongation after fracture is an important indicator for reflecting metal material plasticity, number
Value is bigger, indicates that the plasticity of metal material is better.The measurement of elongation after fracture mainly has craft and automatic measurement two ways.
GB/T228.1-2010 defines the measuring method of elongation after fracture, and manual measurement method is: by tensile sample rupture portion
It carefully with being connected together, is in axis on same straight line, and ensures to measure sample after sample fracture part suitably contacts
Have no progeny gauge length lu, will have no progeny gauge length luWith original gauge length l0It substitutes into following formula and elongation after fracture A is calculated,
A=(lu-l0)/l0× 100%
For hand dipping, the measurement of the label of original gauge length and gauge length of having no progeny is particularly important.People is used under normal conditions
The method of work delineation label, the method working efficiency is low, and there are different degrees of error, direct shadows in personnel's operating process
Ring the measurement result of elongation after fracture.Measurement have no progeny gauge length when tensile sample fracture need to be docked, due to fracture will appear it is scaling-off,
Phenomena such as chip off-falling, therefore it is very difficult that fracture, which is accurately docked,.Even if follow American Standard ASTME8-16a given docking
Compression force request, measurement error is still difficult to avoid that.If fracture position not in sample marking distance middle position, will also use displacement
Method measurement, operates more troublesome.
Automatic measurement is equal to the original gauge length of sample using extensometer gage length, and extensometer automatically determines sample in breaking point
General extension deducts elastic part and obtains to have no progeny and extend Δ l, i.e. (lu-l0), and then acquire elongation after fracture A.Automatic measurement side
Method simple possible, but extensometer cannot automatically identify the fracture position of sample.And during actual tests, sample fracture
The position overwhelming majority is not in extensometer gage length leMiddle position, in this case automatic measurement without the image of Buddha hand dipping when use
Displacement method is modified, and the measured elongation Δ l come out will be less than hand dipping.Simultaneously as sample constriction when fracture
Seriously, if calculating flexible deformation according further to homogeneous deformation when deducting elastic part, the elastic part of deduction is inaccuracy
's.In view of two above reason, automatic measurement elongation after fracture has biggish error although simple possible at present, real
It is in the application of border or in the majority with hand dipping.
Summary of the invention
Elongation after fracture method for automatic measurement two above problem, mesh of the invention are uniaxially stretched for current pole sample
Be to establish a kind of pole sample to be uniaxially stretched elongation after fracture method for automatic measurement, can accurately deduct elastic part, and
Without identifying, fracture position automatic implementation shifts method within the scope of gauge length, to obtain the exact value of elongation after fracture.The present invention exists
Under the premise of known materials elasticity modulus and Poisson's ratio, it is only necessary to the elongation between gages of measurement and record pole sample tension failure moment
Amount and load value, while pole sample outer profile curve of having no progeny is acquired using optical means, it is obtained by flexible deformation analytical calculation
It obtains pole sample and is uniaxially stretched elongation after fracture.
Specific step is as follows for the technical solution adopted in the present invention:
(1) round metal bars sample uniaxial tensile test is carried out, original gauge length is l0, original gauge length radius is a0, measurement
And it records and starts tension failure moment load FNWith elongation between gages amount dlN, and optically acquire longer half coupon of having no progeny
Outer profile information in the axial direction obtains each point coordinate G of outer profile curve by image procossingk(xk,yk), wherein k=0
~M, 0 respectively corresponds sample necking rupture point and certain point in parallel length range close to arc transition minute with M, breaking point
Determination is with ykSubject to value minimum, to correspond to the axis coordinate of necking rupture point as coordinate origin, i.e. x0=0；
(2) Resilient adjustment is carried out to sample outer profile curvilinear coordinate of having no progeny, it is known that metal material elastic modulus E and Poisson's ratio
λ, then each point coordinate after correctingIt is expressed as
WhereinRetain allPoint (quantity T+1), and willIt is modified to (l0+dlN)/
2, then correspond to the coordinate of fracture moment gauge length pointIt is represented by
(3) formula (1) and (2) are based on, acquire each point comprising elastic part by solving equationsWithValue.It is corresponding
Deduct the x of elastic partTValue can be calculate by the following formula
Symmetry distribution in view of displacement method based on sample elongation centered on fracture position, sample pole sample are uniaxial
Stretching is had no progeny gauge length lu=2xT, finally calculate according to the following formula and obtain round metal bars sample elongation after fracture.
A=(lu-l0)/l0× 100% (4)
Beneficial effects of the present invention:
1) the solution of the present invention is used, it is only necessary to measurement and record pole sample fracture moment elongation between gages amount and load
Value, and extract coupon outer profile curve of having no progeny, so that it may elongation after fracture is calculated automatically, and deducts the elasticity of sample inhomogeneous deformation
Part, and without judging that fracture position just reaches the identical effect of displacement method.Compared with existing manual measurement technology, scribing line is saved
With the fixed cumbersome measurement links such as sample of having no progeny, time of measuring and measurement cost are saved；
2) present invention avoids excessive manual measurement error, computational accuracy due to the data using extensometer and optical measurement
Height, and calculating process is easily achieved sequencing, has operability.
Detailed description of the invention
Fig. 1 is to be uniaxially stretched have no progeny photo and outer profile curvilinear coordinate information.
Fig. 2 is pole sample elongation after fracture computation model.
Specific embodiment
Below with reference to specific example and attached drawing, the invention will be further described.
(1) mild steel pole sample uniaxial tensile test is carried out, original gauge length is l0=50mm, original gauge length radius
For a0=5mm is measured and recorded and is started tension failure moment load FN=25320N and elongation between gages amount dlN=6.125mm, and
Optically acquisition have no progeny longer half coupon in the axial direction on outer profile information, as shown in Figure 1, by image
Reason obtains each point coordinate G of outer profile curvek(xk,yk), wherein k=0~M, 0 and M respectively correspond sample necking rupture point peace
Close to certain point of arc transition point in row length range, the determination of breaking point is with ykIt is disconnected to correspond to constriction subject to value minimum
The axis coordinate of knick point is coordinate origin, i.e. x0=0；
(2) as shown in Fig. 2, the sample outer profile curvilinear coordinate to elastic unloading of having no progeny carries out Resilient adjustment, it is known that metal
Elasticity modulus of materials E and Poisson's ratio λ, then each point coordinate after correctingIt is expressed as
WhereinRetain allPoint (quantity T+1), and willIt is modified to (l0+dlN)/
2, then correspond to the coordinate of fracture moment gauge length pointIt is represented by
(3) formula (1) and (2) are based on, acquire each point comprising elastic part by solving equationsWithValue.It is corresponding
Deduct the x of elastic partTValue can be calculate by the following formula
It is computed, xT=29.253mm.Symmetry in view of displacement method based on sample elongation centered on fracture position
Distribution, pole sample are uniaxially stretched the gauge length l that has no progenyu=2xT=58.506mm ≈ 58.5mm, finally according to the following formula
A=(lu-l0)/l0× 100% (4)
It calculates and obtains round metal bars sample elongation after fracture A=17.0%.
Claims (1)
1. the method for automatic measurement of round metal bars sample uniaxial tensile test elongation after fracture, which is characterized in that the measurement method
Specific step is as follows:
(1) round metal bars sample uniaxial tensile test is carried out, original gauge length is l0, original gauge length radius is a0, measure and remember
Record starts tension failure moment load FNWith elongation between gages amount dlN, and optically acquisition has no progeny longer half coupon along axis
The outer profile information in line direction obtains each point coordinate G of outer profile curve by image procossingk(xk,yk), wherein k=0~M, 0
Sample necking rupture point and certain point in parallel length range close to arc transition minute, the determination of breaking point are respectively corresponded with M
It is with ykSubject to value minimum, to correspond to the axis coordinate of necking rupture point as coordinate origin, i.e. x0=0；
(2) Resilient adjustment is carried out to sample outer profile curvilinear coordinate of having no progeny, it is known that metal material elastic modulus E and Poisson's ratio λ, then
Each point coordinate after amendmentIt is expressed as
WhereinRetain allPoint (quantity T+1), and willIt is modified to (l0+dlN)/2, then
The coordinate of corresponding fracture moment gauge length pointIt is represented by
Based on formula (1) and (2), each point comprising elastic part is acquired by solving equationsWithValue；
The corresponding x for deducting elastic partTValue can be calculate by the following formula
Symmetry distribution in view of displacement method based on sample elongation centered on fracture position, sample pole sample are uniaxially stretched
Gauge length of having no progeny lu=2xT；
It finally calculates according to the following formula and obtains round metal bars sample elongation after fracture:
A=(lu-l0)/l0× 100%.
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Cited By (2)
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| CN111157338A (en) * | 2020-01-08 | 2020-05-15 | 吉林大学 | Method for measuring large-strain-range compression hardening curve of metal dumbbell type sample |
| CN113310437A (en) * | 2021-05-28 | 2021-08-27 | 广东韶钢松山股份有限公司 | Method and device for automatically measuring wire section shrinkage |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111157338B (en) * | 2020-01-08 | 2021-09-17 | 吉林大学 | Method for measuring large-strain-range compression hardening curve of metal dumbbell type sample |
| CN113310437A (en) * | 2021-05-28 | 2021-08-27 | 广东韶钢松山股份有限公司 | Method and device for automatically measuring wire section shrinkage |
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