CN102004819B - Method for determining constitutive parameters of butt welded pipe welding seam in biaxial stress state - Google Patents

Abstract

The invention relates to a method for determining constitutive parameters of a butt welded pipe welding seam in the biaxial stress state, which comprises the following steps of: determining the constitutive parameters of the parent metal in the uniaxial stress state, thereby determining the range of the parent metal strength factor K<sim> in the perforated sample tensile finite element analogy, and the range of the hardening index n<sim>; and by determining the variation ranges of the strength factor and the hardening index, obtaining the relationship between different constitutive parameter combinations (K<sim>, n<sim>) and the combinations (F<sim>, Delta l<sim>) of tensile force and gauge length elongation, and establishing a recessive mapping relationship between the combination (F, Delta l) of tensile force and gauge length elongation and the constitutive parameter combination (K, n), thereby obtaining the constitutive parameters of the welding seam in the biaxial stress state. The method induces the planar biaxial tension stress state, which is more approximate to the true stress state of pipe deformation, in the uniaxial tension process of a perforated sample, can be used for accurately and efficiently determining the constitutive parameters of the welding seam ductility of a butt welded pipe, and is beneficial to enhancing the forming quality and the forming limit of the welded pipe.

Description

The method of straight welded pipe welding-seam constitutive parameter under a kind of definite two-dimensional state of stress

Technical field

The present invention relates to ERW Plastic Forming field, specifically is the method for straight welded pipe welding-seam constitutive parameter under a kind of definite two-dimensional state of stress, and this technology also can be extended to confirming of welding plate welding seams constitutive parameter.

Background technology

Because ERW bool has characteristics such as low cost, short period, Strengthening and Toughening, in auto industry, has obtained widespread use.The main difference of welded tube and solid drawn tube is the significant difference of weld seam and mother metal performance; There are significant difference in the strength factor K and the hardenability value n that then mainly are reflected in for the Plastic Forming Effect on Performance in the constitutive parameter of weld seam and mother metal; Be much bigger than mother metal of the strength factor K of weld seam, its hardenability value n is much little than mother metal then.Because ERW mainly presents two-dimensional state of stress in BENDING PROCESS, confirm that therefore the constitutive parameter K of welded tube weld material under the two-dimensional state of stress and n are the bases of research welded tube bending ductility deformational behavior, raising welded tube bending forming quality and forming limit.

Through to literature searches such as existing domestic and international patented technology, standards, do not see the related patent U.S. Patent No. bibliographical information of confirming weld seam constitutive parameter K and n method under the two-dimensional state of stress at present as yet.

Consult relevant both at home and abroad periodical literature, finding that existing method about the weld seam constitutive parameter K that confirms to weld plate and welded tube and n all is based on carries out under the uniaxial stressed state.These methods comprise three kinds of unilateral stretching experimental method, composite material stretching experiment method and microhardness experimental methods.Wherein, the unilateral stretching experimental method is standard or the non-standard tensile sample that directly direct intercepting only comprises weld material on welded tube, carries out the unilateral stretching experiment then.Strength factor K value and the hardenability value n value that the stress-strain diagram match that obtains obtains reflecting the weld material characteristic tested in unilateral stretching.This method mainly is applicable to wide weld seam welded tube, and for the bead weld welded tube, directly intercepting only contains the tensile sample difficulty of weld seam, because the width of sample is very big to the measurement result influence, thereby causes determined Weld Performance parameter fluctuation property big, inaccurate.To the deficiency that is difficult to prepare pure weld seam tensile sample in the weld material stretching experiment; Composite material stretching experiment method is that intercepting comprises that weld seam and material around make the composite material tensile sample near weld seam; Carry out the unilateral stretching experiment; Go out the flow stress of weld seam again based on mixing rule " extraction " from test figure, and then match obtains the constitutive parameter K and the n value of weld material.But, perhaps be regarded as mother metal because this method will or be regarded as weld material between the heat-affected zone material between weld seam and mother metal.Specimen width is different, just means that also heat-affected zone proportion in sample is different, thereby the precision of the weld material constitutive parameter that obtained is had very big influence.And the microhardness experimental method through weld seam and experiment of mother metal microhardness and mother metal unilateral stretching experiment, obtains the flow stress of weld seam then based on hardness-stress direct ratio formula, and then match obtains the constitutive parameter K and the n of weld material.Because the microhardness experimental method is simple, thereby has obtained widespread use.

For the solid drawn tube bending forming, Yan Jing etc. have proposed the method for solid drawn tube constitutive parameter K and n under a kind of definite two-dimensional state of stress.This method has at first designed the porose tensile sample that two-dimensional state of stress under unilateral stretching, can occur; Adopt porose sample unilateral stretching experiment then, obtained the constitutive parameter K and the n of solid drawn tube under the two-dimensional state of stress in conjunction with finite element analogy and artificial neural network.This method is applicable to seamless tubular goods, can be the constitutive parameter K and the n that confirm ERW mother metal under the two-dimensional state of stress reference is provided.

Summary of the invention

For overcoming the difficult problem that prior art can't obtain welded tube weld seam constitutive parameter under the two-dimensional state of stress, the present invention proposes the method for straight welded pipe welding-seam constitutive parameter under a kind of definite two-dimensional state of stress.

The method of straight welded pipe welding-seam constitutive parameter comprises the steps: under definite two-dimensional state of stress that the present invention proposes

Step 1; Carry out mother metal unilateral stretching experiment, confirm constitutive parameter

and of mother metal under uniaxial stressed state

The specimen types of using according to tubing among the GB/T 228-2002 appendix D, from the mother metal position of the weld seam symmetry vertical standard arc tensile sample of intercepting total wall thickness vertically, wherein scale-up factor gets 5.65.

Adopt cupping machine that this sample is carried out the unilateral stretching experiment; Obtain the flow stress-strain data of mother metal in the drawing process, adopt formula (1), formula (2) to obtain constitutive parameter

and

of mother metal under uniaxial stressed state then

$n_{\mathrm{uni}}^b=\frac{N\&CenterDot;\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\&CenterDot;\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\mathrm{uni},j}^b\right)-\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\&CenterDot;\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\mathrm{uni},j}^b\right)}{N\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}{\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)}^2-{\left[\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\right]}^2}---\left(1\right)$

$K_{\mathrm{uni}}^b=\exp \left[\frac{\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\mathrm{uni},j}^b\right)-n_{\mathrm{uni}}^b\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)}{N}\right]---\left(2\right)$

In formula (1), (2);

is the flow stress under the mother metal uniaxial stressed state; ε is the logarithmic strain under the mother metal uniaxial stressed state; N is the flow stress-strain data group number under the mother metal uniaxial stressed state that obtains in the stretching experiment;

is the strength factor under the mother metal uniaxial stressed state, and

is the hardenability value under the mother metal uniaxial stressed state.

Step 2 is confirmed the quadrature arranging scheme of the porose sample stretching of mother metal sunykatuib analysis

Strength factor according to mother metal under the uniaxial stressed state that obtains in the step 1

And hardenability value

Confirm the strength of parent COEFFICIENT K in the porose sample stretching finite element analogy _SimScope do

Hardenability value n _SimScope do

And the variation range of strength factor and hardenability value two factors is subdivided into 3～4 levels, corresponding factor level table is seen table 1, table 2.Corresponding to the factor level number is that 3 and 4 orthogonal table is confirmed as L respectively ₉(3 ⁴) and L ₁₆(4 ⁵).Certain that then strength factor and hardenability value two factors is put into selected orthogonal table two lists, thereby obtains the orthogonal experiment arranging scheme of porose sample stretching sunykatuib analysis.

Table 1: the factor level table when strength factor and hardenability value are got 3 levels

Table 2: the factor level table when strength factor and hardenability value are got 4 levels

Step 3 obtains different constitutive parameter combination (K _Sim, n _Sim) make up (F with tensile force and elongation between gages amount _Sim, Δ l _Sim) corresponding relation

Set up the porose sample unilateral stretching of mother metal finite element model.The porose specimen configuration size wherein and the physical dimension of the vertical standard arc tensile sample of total wall thickness are identical, and beat the through hole of Φ 5mm along thickness direction at the sample center, and draw speed is 3mm/min.Adopt the porose sample stretch finite element model of being set up of mother metal,, simulate different constitutive parameter combination (K according to the quadrature arranging scheme that step 2 is confirmed _Sim, n _Sim) under porose sample unilateral stretching process.Obtain maximum stretching force and corresponding sample marking distance elongation in the simulation process.5s extracts 5 tensile forces and corresponding sample marking distance elongation data equably in the time before this maximum stretching force occurs then, and back 4s extracts 4 tensile forces and correspondence equably in the time sample marking distance elongation data occur at this maximum stretching force.Thereby obtain every group of constitutive parameter combination (K _Sim, n _Sim) with 10 groups of tensile forces and sample marking distance elongation (F _Sim, Δ l _Sim) corresponding relation.

Step 4 is set up the combination of the combination of tensile force and elongation between gages amount (F, Δ l) and constitutive parameter (K, the recessive mapping relations between n)

Structure comprises the error back propagation artificial neural network of three layers of input layers, latent layer, output layer.Wherein, the node number of input layer, latent layer, output layer is respectively 20,8 and 2; And the training function of network using is the Levenberg-Marquardt function; The transport function of input layer-latent interlayer is Tangent sigmoid, and the transport function between latent layer-output layer is the linear function.With tensile force that obtains in the step 3 and elongation between gages amount combination (F _Sim, Δ l _Sim) as the input vector of artificial neural network, constitutive parameter makes up (K _Sim, n _Sim) as output vector, this artificial neural network is trained, set up the combination of the combination of tensile force and elongation between gages amount (F, Δ l) and constitutive parameter (K, the recessive mapping relations between n).

Step 5 is carried out the porose sample unilateral stretching experiment of mother metal, obtains the tensile force F in the experiment _ExpWith elongation between gages amount Δ l _Exp

With the mother metal zone of weld seam symmetry, measure-alike punching sample in intercepting and the step 2 adopts cupping machine that sample is carried out the unilateral stretching experiment of 3mm/min, the sample marking distance elongation of maximum stretching force in obtaining testing and correspondence.5s extracts 5 tensile forces and corresponding sample marking distance elongation data equably in the time before this maximum stretching force occurs then, and back 4s extracts 4 tensile forces and correspondence equably in the time sample marking distance elongation data occur at this maximum stretching force.Thereby obtain 10 groups of tensile forces and sample marking distance elongation (F _Exp, Δ l _Exp) data are right.

Step 6, constitutive parameter

and of mother metal under the acquisition two-dimensional state of stress

10 groups of tensile forces that step 5 is obtained and elongation between gages amount (F _Exp, Δ l _Exp) data make up with elongation between gages amount combination (F, Δ l) and constitutive parameter in step 4, set up tensile force as input vector input that (K in the artificial neural network of the recessive mapping relations between n), obtains the constitutive parameter of mother metal under two-dimensional state of stress

With

Step 7 is set up the relation between the mother metal flow stress under the single, double stress state

Given strain value variation range ε=[0,0.5], and adopt formula (3) that it is separated into 100 sections.Obtained according to step a base material in the uniaxial stress state constitutive parameters and

using the formula

get the base material in uniaxial stress state flow stress According to the base material obtained in Step 6 biaxial stress state in the constitutive parameters

and

using formula

get the base material in the biaxial stress state flow stress

using regression analysis to establish the base material under biaxial stress state flow stress

and the base material under uniaxial stress state flow stress

functional relationship between the two (4)

ε _j＝0.5/100×(j-1)(j＝1，…，101) (3)

${\mathrm{\&sigma;}}_{\mathrm{bi}}^b=f\left({\mathrm{\&sigma;}}_{\mathrm{uni}}^b\right)---\left(4\right)$

In formula (3), j is with one of them discrete point after being separated into 100 sections between strain regions, ε _jIt is the corresponding strain value of j discrete point.In formula (4);

is the flow stress of mother metal under uniaxial stressed state;

is the flow stress of mother metal under two-dimensional state of stress, and f is the funtcional relationship of the two.

Step 8 is carried out the microhardness experiment, confirms weld hardness HV _wAnd mother metal hardness HV _b

After with sand paper welded tube surface finish to be measured being polished; Along circumferentially pasting a slice coordinate paper, clip pipe fitting on the pipe surface, be put on the testing table with anchor clamps; Begin to measure hardness from the weld seam center; Then pipe is rotated 1mm (the 1mm mesh lines through alignment coordinate paper is realized), clamp pipe once more, measure once more.So repeat, obtain the hardness HV of weld seam _wAnd the hardness HV of mother metal _b

Step 9 is confirmed the flow stress

of weld seam under uniaxial stressed state

Flow stress with mother metal under the uniaxial stressed state in [0,0.5] between the given strain regions of step 7 acquisition

The weld seam and the mother metal hardness HV that obtain with step 8 _w, HV _bSubstitution formula (5), the flow stress of weld seam under the acquisition uniaxial stressed state

${\mathrm{\&sigma;}}_{\mathrm{uni},j}^w=\frac{{\mathrm{HV}}_w}{{\mathrm{HV}}_b}{\mathrm{\&sigma;}}_{\mathrm{uni},j}^b,(j=1,\&CenterDot;\&CenterDot;\&CenterDot;,101)---\left(5\right)$

In the formula (5), HV _w, HV _bBe respectively weld seam and mother metal hardness, j is with one of them discrete point after being separated into 100 sections between strain regions,

Be respectively weld seam and the mother metal flow stress under uniaxial stressed state.

Step 10 is confirmed the flow stress

of weld seam under two-dimensional state of stress

Between the given strain regions that step 9 is obtained [0; 0.5] in

substitution formula (4) in the scope, obtain the flow stress between this strain regions of weld seam under the two-dimensional state of stress

Step 11 is confirmed constitutive parameter

and

of weld seam under two-dimensional state of stress

Flow stress according to weld seam under the two-dimensional state of stress in [0,0.5] scope between the strain regions of step 10 acquisition

With strain stress _jData, employing formula (6), formula (7) obtain the constitutive parameter of weld seam under two-dimensional state of stress With

$n_{\mathrm{bi}}^w=\frac{101\&CenterDot;\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\&CenterDot;\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\mathrm{bi},j}^w\right)-\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\&CenterDot;\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&sigma;}}_{\mathrm{bi},j}^w\right)}{101\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}{\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)}^2-{\left[\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\right]}^2}---\left(6\right)$

$K_{\mathrm{bi}}^w=\exp \left[\frac{\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&sigma;}}_{\mathrm{bi},j}^w\right)-n_{\mathrm{bi}}^w\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)}{101}\right]---\left(7\right)$

In formula (6), (7),

is the flow stress of weld material under two-dimensional state of stress;

is the strength factor of weld material under two-dimensional state of stress;

is the hardenability value of weld material under two-dimensional state of stress; ε is strain.

The invention has the beneficial effects as follows: the method for straight welded pipe welding-seam constitutive parameter under a kind of definite two-dimensional state of stress that the present invention proposes; Only need carry out simple standard and singly draw experiment, porose sample stretching experiment and micro-hardness testing experiment; In conjunction with finite element numerical simulation and neural network prediction method, can obtain the constitutive parameter of welded tube weld seam.The experimental implementation that this method relates to is simple; Induced the two-way tensile stress state in plane of the true stress state that more approaches the tubing distortion in the sample unilateral stretching process of in addition punching, and the method that the artificial neural network that is adopted, finite element analogy and experiment combine has been proved to be the method that a kind of high precision obtains the solid drawn tube plasticity constitutive parameter under two-dimensional state of stress and the large deformation condition.Therefore the present invention can be used for confirming accurately and efficiently straight welded pipe welding-seam plasticity constitutive parameter; Plastic yield behavior for research welded tube BENDING PROCESS; Shaping law and parameter optimization and the assessment of welded tube forming property provide important method and basis; Help improving welded tube forming quality and forming limit, promote further developing of the advanced theory and technology of welded tube bending and Plastic Forming.

Four, description of drawings

Fig. 1 is for confirming the process flow diagram of straight welded pipe welding-seam constitutive parameter under the two-dimensional state of stress;

Fig. 2 is porose sample stretch finite element model.

Five, embodiment

Embodiment one:

Present embodiment is to confirm that specification is the weld seam constitutive parameter of ERW under the QSTE340 two-dimensional state of stress of 78 * 2.7mm, and it confirms that specifically step is following:

The specimen types of using according to tubing among the GB/T 228-2002 appendix D, from the mother metal position of the weld seam symmetry vertical standard arc tensile sample of intercepting total wall thickness vertically, wherein scale-up factor gets 5.65.Adopt cupping machine that this sample is carried out the unilateral stretching experiment; Obtain the flow stress-strain data of mother metal in the drawing process, adopt formula (1), formula (2) to obtain the constitutive parameter

of mother metal under uniaxial stressed state then

$n_{\mathrm{uni}}^b=\frac{N\&CenterDot;\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\&CenterDot;\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\mathrm{uni},j}^b\right)-\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\&CenterDot;\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\mathrm{uni},j}^b\right)}{N\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}{\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)}^2-{\left[\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\right]}^2}---\left(1\right)$

$K_{\mathrm{uni}}^b=\exp \left[\frac{\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\mathrm{uni},j}^b\right)-n_{\mathrm{uni}}^b\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)}{N}\right]---\left(2\right)$

In formula (1), (2);

is the flow stress under the mother metal uniaxial stressed state; ε is the logarithmic strain under the mother metal uniaxial stressed state; N is the flow stress under the mother metal uniaxial stressed state-strain data group number;

is the strength factor under the mother metal uniaxial stressed state, and

is the hardenability value under the mother metal uniaxial stressed state.

Step 2 is confirmed the quadrature arranging scheme of the porose sample stretching of mother metal sunykatuib analysis

Strength factor according to mother metal under the uniaxial stressed state that obtains in the step 1

And hardenability value

Confirm the strength of parent COEFFICIENT K in the porose sample stretching finite element analogy _SimScope be (449,1249), hardenability value n _SimScope be (0.177,0.267), and the variation range of strength factor and hardenability value two factors is subdivided into 3 levels, corresponding factor level table is seen table 3.And adopt orthogonal table L in view of the above ₉(3 ⁴).Certain that then strength factor and hardenability value two factors is put into selected orthogonal table two lists, thereby confirms to obtain the quadrature arranging scheme of porose sample stretching sunykatuib analysis, and is as shown in table 4.

Table 3: the factor level table when the sharp hardenability value of strength factor is got 3 levels in the instance 1

Table 4: the quadrature arranging scheme of instance 1

Step 3 obtains different constitutive parameter combination (K _Sim, n _Sim) make up (F with tensile force and elongation between gages amount _Sim, Δ l _Sim) corresponding relation

Set up the porose sample unilateral stretching of mother metal finite element model.Wherein the physical dimension of the vertical standard arc tensile sample of the physical dimension of porose sample and total wall thickness is identical, and beats the through hole of Φ 5mm along thickness direction at the sample center, and draw speed is 3mm/min.Porose sample unilateral stretching finite element model parameter comprises: sample adopts the S4R mesh discretization, and the size of mesh opening of bare terminal end is that size of mesh opening is that 0.8mm, remainder size of mesh opening are 1.5mm around 2mm, the hole.Adopt this finite element model,, simulate different constitutive parameter combination (K according to the quadrature arranging scheme that step 2 is confirmed _Sim, n _Sim) under porose sample unilateral stretching process.Obtain maximum stretching force and corresponding sample marking distance elongation in the simulation process.5s extracts 5 tensile forces and corresponding sample marking distance elongation data equably in the time before this maximum stretching force occurs then, and back 4s extracts 4 tensile forces and correspondence equably in the time sample marking distance elongation data occur at this maximum stretching force.Thereby obtain every group of constitutive parameter combination (K _Sim, n _Sim) with 10 groups of tensile forces and sample marking distance elongation (F _Sim, Δ l _Sim) corresponding relation.The tensile force F that simulation obtains _SimSample marking distance elongation Δ l with correspondence _SimData are as shown in table 5.

Table 5: the quadrature collocation analog result of instance 1

Step 4 is set up the combination of the combination of tensile force and elongation between gages amount (F, Δ l) and constitutive parameter (K, the recessive mapping relations between n)

Structure comprises the error back propagation artificial neural network of three layers of input layers, latent layer, output layer.Wherein, the node number of input layer, latent layer, output layer is respectively 20,8 and 2; And the training function of network using is the Levenberg-Marquardt function; The transport function of input layer-latent interlayer is Tangent sigmoid, and the transport function between latent layer-output layer is the linear function.With tensile force that obtains in the step 4 and elongation between gages amount combination (F _Sim, Δ l _Sim) as the input vector of artificial neural network, constitutive parameter makes up (K _Sim, n _Sim) as output vector, this artificial neural network is trained, set up the combination of the combination of tensile force and elongation between gages amount (F, Δ l) and constitutive parameter (K, the recessive mapping relations between n).

Step 5 is carried out the porose sample unilateral stretching experiment of mother metal, obtains the tensile force F in the experiment _ExpWith elongation between gages amount Δ l _Exp

With the mother metal zone of weld seam symmetry, measure-alike punching sample in intercepting and the step 2 adopts cupping machine that sample is carried out the unilateral stretching experiment of 3mm/min, the sample marking distance elongation of maximum stretching force in obtaining testing and correspondence.5s extracts 5 tensile forces and corresponding sample marking distance elongation data equably in the time before this maximum stretching force occurs then, and back 4s extracts 4 tensile forces and correspondence equably in the time sample marking distance elongation data occur at this maximum stretching force.Thereby obtain 10 groups of tensile forces and sample marking distance elongation (F _Exp, Δ l _Exp) data are right, see table 6.

Table 6: the experimental result of instance 1

Step 6, constitutive parameter

and

of mother metal under the acquisition two-dimensional state of stress

With 10 groups of tensile forces that obtain in step 5 experiment and elongation between gages amount (F _Exp, Δ l _Exp) data are to as input vector, input has been set up tensile force and has been made up with elongation between gages amount combination (F, Δ l) and constitutive parameter that (K in the artificial neural network of the recessive mapping relations between n), obtains the constitutive parameter of mother metal under two-dimensional state of stress in step 4

Be 615MPa,

Be 0.1.

Step 7 is set up the relation between the mother metal flow stress under the single, double stress state

Given strain value variation range ε=[0,0.5], and adopt formula (3) that it is separated into 100 sections.Obtained according to step a base material in the uniaxial stress state constitutive parameters

and

using the formula

get the base material in uniaxial stress state flow stress

According to the base material obtained in Step 6 biaxial stress state in the constitutive parameters

and

using formula

get the base material in the biaxial stress state flow stress

using regression analysis to establish the base material under biaxial stress state flow stress and the base material under uniaxial stress state flow stress

functional relationship between the two (4)

ε _j＝0.5/100×(j-1)(j＝1，…，101) (3)

${\mathrm{\&sigma;}}_{\mathrm{bi}}^b=f\left({\mathrm{\&sigma;}}_{\mathrm{uni}}^b\right)---\left(4\right)$

In formula (3), j is with one of them discrete point after being separated into 100 sections between strain regions, ε _jIt is the corresponding strain value of j discrete point.In formula (4); is the flow stress of mother metal under uniaxial stressed state;

is the flow stress of mother metal under two-dimensional state of stress, and f is the funtcional relationship of the two.In the present embodiment, obtain ${\mathrm{\&sigma;}}_{\mathrm{Bi}}^b={1.19\mathrm{\&sigma;}}_{\mathrm{Uni}}^b-78.75.$

Step 8 is carried out the microhardness experiment, confirms weld hardness HV _wAnd mother metal hardness HV _b

After with sand paper welded tube surface finish to be measured being polished; Along circumferentially pasting a slice coordinate paper, clip pipe fitting on the pipe surface, be put on the testing table with anchor clamps; Begin to measure hardness from the weld seam center; Then pipe is rotated 1mm (the 1mm mesh lines through alignment coordinate paper is realized), clamp pipe once more, measure once more.So repeat, realize the test of butt welded seam and mother metal microhardness.Average again at last, obtain weld hardness HV _wBe 206HV, mother metal hardness HV _bBe 159HV.

Step 9 is confirmed the flow stress of weld seam under uniaxial stressed state

Flow stress with mother metal under the uniaxial stressed state in [0,0.5] between the given strain regions of step 7 acquisition The weld seam and the mother metal hardness HV that obtain with step 8 _w, HV _bSubstitution formula (5), the flow stress of weld seam under the acquisition uniaxial stressed state

${\mathrm{\&sigma;}}_{\mathrm{uni},j}^w=\frac{{\mathrm{HV}}_w}{{\mathrm{HV}}_b}{\mathrm{\&sigma;}}_{\mathrm{uni},j}^b,(j=1,\&CenterDot;\&CenterDot;\&CenterDot;,101)---\left(5\right)$

In the formula (5), HV _w, HV _bBe respectively weld seam and mother metal hardness, j is with one of them discrete point after being separated into 100 sections between strain regions,

Be respectively weld seam and the mother metal flow stress under uniaxial stressed state.

Step 10 is confirmed the flow stress

of weld seam under two-dimensional state of stress

Between the given strain regions that step 9 is obtained [0; 0.5] in

substitution formula (6) in the scope, obtain the flow stress

between this strain regions of weld seam under the two-dimensional state of stress

Step 11 is confirmed constitutive parameter

and

of weld seam under two-dimensional state of stress

Flow stress according to weld seam under the two-dimensional state of stress in [0,0.5] scope between the strain regions of step 10 acquisition

With strain stress _jData, employing formula (6), formula (7) obtain the strength factor of the weld seam of weld seam under two-dimensional state of stress

Be 820MPa, hardenability value Be 0.0964.

$n_{\mathrm{bi}}^w=\frac{101\&CenterDot;\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\&CenterDot;\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\mathrm{bi},j}^w\right)-\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\&CenterDot;\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&sigma;}}_{\mathrm{bi},j}^w\right)}{101\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}{\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)}^2-{\left[\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)\right]}^2}---\left(6\right)$

$K_{\mathrm{bi}}^w=\exp \left[\frac{\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&sigma;}}_{\mathrm{bi},j}^w\right)-n_{\mathrm{bi}}^w\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_j\right)}{101}\right]---\left(7\right)$

In formula (6), (7),

is the flow stress of weld material under two-dimensional state of stress; is the strength factor of weld material under two-dimensional state of stress;

is the hardenability value of weld material under two-dimensional state of stress; ε is strain.

Claims (2)

1. the method for straight welded pipe welding-seam constitutive parameter under the definite two-dimensional state of stress is characterized in that the detailed process of straight welded pipe welding-seam constitutive parameter is following under described definite two-dimensional state of stress:

Step 1; Carry out mother metal unilateral stretching experiment, confirm constitutive parameter

and of mother metal under uniaxial stressed state

From with the mother metal position of the weld seam symmetry vertical standard arc tensile sample of intercepting total wall thickness vertically, wherein scale-up factor gets 5.65; This sample is carried out the unilateral stretching experiment; Obtain the flow stress-logarithmic strain data of mother metal in the drawing process, employing formula (1), formula (2) obtain constitutive parameter and of mother metal under uniaxial stressed state

$n_{\mathrm{uni}}^b=\frac{N\&CenterDot;\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&epsiv;}}_j\right)\&CenterDot;\left(\lg {\mathrm{\&sigma;}}_{\mathrm{uni},j}^b\right)-\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&epsiv;}}_j\right)\&CenterDot;\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&sigma;}}_{\mathrm{uni},j}^b\right)}{N\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}{\left(\lg {\mathrm{\&epsiv;}}_j\right)}^2-{\left[\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&epsiv;}}_j\right)\right]}^2}---\left(1\right)$

$K_{\mathrm{uni}}^b=\exp [\frac{\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&sigma;}}_{\mathrm{uni},j}^b\right)-n_{\mathrm{uni}}^b\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&epsiv;}}_j\right)}{N}---\left(2\right)$

In formula (1), (2);

is the flow stress under the mother metal uniaxial stressed state; ε is the logarithmic strain under the mother metal uniaxial stressed state; N is the flow stress-logarithmic strain data set number under the mother metal uniaxial stressed state that obtains in the stretching experiment; is the strength factor in the constitutive parameter under the mother metal uniaxial stressed state, and

is the hardenability value in the constitutive parameter under the mother metal uniaxial stressed state;

Step 2 is confirmed the quadrature arranging scheme of the porose sample stretching of mother metal sunykatuib analysis; According to the strength factor in the constitutive parameter of mother metal under the uniaxial stressed state that obtains in the step 1

And hardenability value

Confirm the strength factor K in the mother metal constitutive parameter in the porose sample stretching finite element analogy _SimScope do

Hardenability value n in the mother metal constitutive parameter _SimScope do

And the variation range of strength factor in the mother metal constitutive parameter and hardenability value two factors is divided into 3～4 levels, corresponding factor level table is seen table 1 and table 2:

Table 1: the factor level table when strength factor and hardenability value are got 3 levels

Table 2: the factor level table when strength factor and hardenability value are got 4 levels

Corresponding to the factor level number is that 3 and 4 orthogonal table is confirmed as L respectively ₉(3 ⁴) and L ₁₆(4 ⁵); Certain that then strength factor and hardenability value two factors is put into selected orthogonal table two lists, thereby obtains the orthogonal experiment arranging scheme of porose sample stretching sunykatuib analysis;

Step 3 is confirmed different constitutive parameter combination (K _Sim, n _Sim) and simulate tensile force and the sample marking distance elongation combination (F that obtains _Sim, Δ l _Sim) corresponding relation; Set up the porose sample unilateral stretching of mother metal finite element model; The porose specimen configuration size wherein and the physical dimension of the vertical standard arc tensile sample of total wall thickness are identical, and beat the through hole of Φ 5mm along thickness direction at the sample center, and draw speed is 3mm/min;

According to the quadrature arranging scheme that step 2 is confirmed, simulate different constitutive parameter combination (K _Sim, n _Sim) under porose sample unilateral stretching process, obtain maximum stretching force and corresponding sample marking distance elongation in the simulation process; 5s extracts 5 tensile forces and corresponding sample marking distance elongation data equably in the time before this maximum stretching force occurs; And 4s extracts 4 tensile forces and corresponding sample marking distance elongation data equably in the time after this maximum stretching force occurs, thereby obtains every group of constitutive parameter combination (K _Sim, n _Sim) the 10 groups of tensile forces and the sample marking distance elongation (F that obtain with simulation _Sim, Δ l _Sim) corresponding relation;

Step 4 is set up the combination of the combination of tensile force and sample marking distance elongation (F, Δ l) and constitutive parameter (K, the recessive mapping relations between n); Structure comprises the error back propagation artificial neural network of three layers of input layers, latent layer, output layer; Wherein, the node number of input layer, latent layer, output layer is respectively 20,8 and 2; And the training function of network using is the Levenberg-Marquardt function; The transport function of input layer-latent interlayer is Tangent sigmoid, and the transport function between latent layer-output layer is the linear function; Tensile force and sample marking distance elongation that simulation in the step 3 is obtained make up (F _Sim, Δ l _Sim) as the input vector of artificial neural network, constitutive parameter makes up (K _Sim, n _Sim) as output vector, this artificial neural network is trained, set up the combination of the combination of tensile force and sample marking distance elongation (F, Δ l) and constitutive parameter (K, the recessive mapping relations between n);

Step 5 is carried out the porose sample unilateral stretching experiment of mother metal, obtains the tensile force F in the experiment _ExpWith sample marking distance elongation Δ l _ExpWith the mother metal zone of weld seam symmetry, measure-alike punching sample in intercepting and the step 2 carries out the unilateral stretching experiment of 3mm/min to sample, the sample marking distance elongation of maximum stretching force in obtaining testing and correspondence; 5s is in the time before this maximum stretching force occurs; Extract 5 tensile forces and corresponding sample marking distance elongation data equably; And 4s extracts 4 tensile forces and corresponding sample marking distance elongation data equably in the time after this maximum stretching force occurs, thereby obtains the tensile force and the sample marking distance elongation (F of 10 groups of experiments _Exp, Δ l _Exp) data are right;

Step 6, the constitutive parameter of mother metal under the acquisition two-dimensional state of stress

With

10 groups of tensile forces that step 5 is obtained through experiment and sample marking distance elongation (F _Exp, Δ l _Exp) reflection tensile force and the sample marking distance elongation combination (F of data to having set up in step 4 as input vector input; Δ l) with constitutive parameter combination (K; In the artificial neural network of the recessive mapping relations n), obtain the constitutive parameter of mother metal under two-dimensional state of stress

With

Step 7, the establishment of a single, double base material stress state the relationship between flow stress; given range value true strain ε = [0,0.5], and using equation (3) to be discretized into 100; obtained according to step 1 The base material in the uniaxial stress state constitutive parameters and

using the formula

get the base material in uniaxial stress state flow stress

according to step 6 base material obtained biaxial stress state in the constitutive parameters

and

using the formula

get parent material biaxial stress state in the flow stress

using regression analytical methods to establish the base material under biaxial stress state flow stress and the base material under uniaxial stress state flow stress

functional relationship between the two (4)

ε _j＝0.5/100×(j-1)(j＝1，…，101) (3)

${\mathrm{\&sigma;}}_{\mathrm{bi}}^b=f\left({\mathrm{\&sigma;}}_{\mathrm{uni}}^b\right)---\left(4\right)$

In formula (3), j is one of them discrete point after the logarithmic strain interval is separated into 100 sections, ε _jIt is the corresponding logarithmic strain value of j discrete point.In formula (4);

is the flow stress of mother metal under uniaxial stressed state; is the flow stress of mother metal under two-dimensional state of stress, and f is the funtcional relationship of the two;

Step 8 is carried out the microhardness experiment, confirms weld hardness HV _wAnd mother metal hardness HV _bAfter with sand paper welded tube surface finish to be measured being polished, along circumferentially pasting a slice coordinate paper, clip pipe fitting, be put on the testing table, begin to measure hardness from the weld seam center with anchor clamps on the pipe surface; Pipe is rotated 1mm, clamp pipe once more, measure once more; So repeat, till pipe rotated for 1 week, obtain the hardness HV of weld seam _wAnd the hardness HV of mother metal _b

Step 9 is confirmed the flow stress of weld seam under uniaxial stressed state Flow stress with mother metal under the uniaxial stressed state in the given logarithmic strain interval [0,0.5] of step 7 acquisition

The weld seam and the mother metal hardness HV that obtain with step 8 _w, HV _bSubstitution formula (5), the flow stress of weld seam under the acquisition uniaxial stressed state

${\mathrm{\&sigma;}}_{\mathrm{uni},j}^w=\frac{{\mathrm{HV}}_w}{{\mathrm{HV}}_b}{\mathrm{\&sigma;}}_{\mathrm{uni},j}^b(j=1,\&CenterDot;\&CenterDot;\&CenterDot;,101)---\left(5\right)$

In the formula (5), HV _w, HV _bBe respectively weld seam and mother metal hardness, j is one of them discrete point after the logarithmic strain interval is separated into 100 sections, Be respectively weld seam and the mother metal flow stress under uniaxial stressed state;

Step 10; Confirm the given logarithmic strain interval [0 that the flow stress

of weld seam under two-dimensional state of stress obtains step 9; 0.5] in

substitution formula (4) in the scope, obtain the flow stress

of weld seam in this logarithmic strain interval under the two-dimensional state of stress

Step 11 is confirmed the constitutive parameter of weld seam under two-dimensional state of stress

With

Flow stress according to weld seam under the two-dimensional state of stress in interval [0, the 0.5] scope of the logarithmic strain of step 10 acquisition

With logarithmic strain ε _jData, employing formula (6), formula (7) obtain the constitutive parameter of weld seam under two-dimensional state of stress With

$n_{\mathrm{bi}}^w=\frac{101\&CenterDot;\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&epsiv;}}_j\right)\&CenterDot;\left(\lg {\mathrm{\&sigma;}}_{\mathrm{bi},j}^w\right)-\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&epsiv;}}_j\right)\&CenterDot;\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&sigma;}}_{\mathrm{bi},j}^w\right)}{101\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}{\left(\lg {\mathrm{\&epsiv;}}_j\right)}^2-{\left[\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&epsiv;}}_j\right)\right]}^2}---\left(6\right)$

$K_{\mathrm{bi}}^w=\exp \left[\frac{\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&sigma;}}_{\mathrm{bi},j}^w\right)-n_{\mathrm{bi}}^w\underset{j=1}{\overset{101}{\mathrm{\&Sigma;}}}\left(\lg {\mathrm{\&epsiv;}}_j\right)}{101}\right]---\left(7\right)$

In formula (6), (7),

is the flow stress of weld material under two-dimensional state of stress; is the strength factor of weld material in the constitutive parameter under the two-dimensional state of stress;

is the hardenability value of weld material in the constitutive parameter under the two-dimensional state of stress; ε is logarithmic strain.

2. the method for straight welded pipe welding-seam constitutive parameter under a kind of according to claim 1 definite two-dimensional state of stress; It is characterized in that; The porose specimen configuration size in the described step 3 and the physical dimension of the vertical standard arc tensile sample of total wall thickness are identical, and beat the through hole of Φ 5mm along thickness direction at the sample center.

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