CN103048203A - Wall thickness linear model-based pipe mechanical property hydro-bugling testing method - Google Patents

Abstract

The invention discloses a wall thickness linear model-based pipe mechanical property hydro-bugling testing method, to solve the problems that the conventional pipe mechanical property hydro-bugling testing method is difficult to measure pipe wall thickness and discontinuous in experiment. The method comprises the following steps of: firstly, testing the initial wall thickness, the outer radius and the bulging area length of the pipe to be tested; secondly, putting the pipe to be tested between an upper die and a lower die, and sealing two ends of the pipe to be tested; thirdly, filling a high-pressure liquid medium into the pipe to be tested; fourthly, recording the pressure and the bulging height of the high-pressure liquid medium in the bulging process of the pipe to be tested in real time till the pipe to be tested is cracked; fifthly, measuring the wall thickness of a crack point of the pipe to be tested, and calculating and obtaining the wall thickness of each moment in the bulging process according to the wall thickness linear model; and sixthly, calculating and obtaining an equivalent stress stain curve of the pipe. The method is applied to pipe mechanical property hydro-bugling testing.

Description

Mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model

Technical field

The present invention relates to a kind of mechanical properties of tubular goods hydraulic expanding-forming method of testing.

Background technology

The accurate test of material mechanical performance is the mechanical characteristic of reasonable exosyndrome material, realizes the definite important foundation that reaches numerical simulation analysis of technological parameter in the material forming process.One way tensile test is one of main method of test material mechanical property.For sheet material, when along the mechanical property of different directions in the board plane not simultaneously, can be along the intercepting of the different directions on flat board sample, by the stress-strain diagram of one way tensile test test sheet material respective direction.For tubing, there is equally the difference of mechanical property along axial and hoop.At this moment, the axial mechanical property of tubing still can be tested by one way tensile test, but for hoop or other directions, because tubing is curve form, if carry out again unilateral stretching behind the sample flattening with intercepting, the work hardening that then flattens process must make the performance of sample change, and the less impact of pipe diameter is larger, thereby can't obtain accurately mechanical properties of tubular goods.In order to test more accurately the mechanical property of tubing, can test by Tube Hydroforming.During the bulging experiment, by measuring bulging pressure, the bulging height of tubing and the data such as wall thickness of tubing of tubing inside, can calculate the mechanical performance indexs such as stress-strain diagram, hardenability value n value and yield strength of tubing by certain theoretical formula.Because destruction tubing is not dissectd in the bulging experiment, so can obtain comparatively accurately mechanical property result.At present, there is the Tube Hydroforming experiment of various ways.The main difference of these experimental techniques is determining of centre position, tube bulge district wall thickness data in the Bulging Process.One class methods can be described as " interrupt experiments method ", and namely (bulging height) interrupt experiments after a certain amount of bulging distortion occurs tubing utilizes custom-designed device that the wall thickness of tubing is measured.After the measurement, with tubing reseal, bulging, and then interrupt experiments is carried out the measurement of wall thickness.So repeatedly, until tubing breaks, experiment finishes.Utilize the method, though can obtain the wall thickness of different bulging stage tubing, but because the process that tubing has experienced loading repeatedly, unloaded, reloads, the mechanical property of tubing changes, so acquired results and unreliable.And this experimental implementation is loaded down with trivial details, and efficient is very low.Another kind of method can be described as " a plurality of SAMPLE METHOD ", namely carries out bulging with a plurality of tubular product samples and stop experiment under different pressure or bulging height, measures respectively the wall thickness of each tubular product sample and bulging height and as the wall thickness in the continuous Bulging Process of tubing.Although the method has been avoided repeated load, uninstall process, owing to having adopted a plurality of samples to test, the original thickness of each sample and performance etc. have certain difference, and its deformational behavior also will have obvious difference.Therefore, utilize the method also can not accurately obtain the performance of the tubing of testing.

Summary of the invention

The present invention exists tube wall thickness to measure difficulty and the discontinuous problem of experiment for solving existing mechanical properties of tubular goods hydraulic expanding-forming method of testing, and then a kind of mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model is provided.

Mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model of the present invention realizes according to the following steps:

The initial wall thickness t of step 1, measurement tubing to be tested ₀, tubing to be tested external radius R ₀With bulging section length L ₀

Step 2, tubing to be tested is placed between mold and the bed die, and seals by the two ends that left sealing punch and right sealing punch are treated test tubing;

Step 3, be filled with high-pressure liquid medium in tubing to be tested, the pressure of high-pressure liquid medium is 15～300MPa;

Pressure and the bulging height h of the high-pressure liquid medium 8 in step 4, the real time record tube bulge process to be tested are until tubing to be tested breaks;

The wall thickness of step 5, measurement tubing breakdown point to be tested:

Obtain each wall thickness t constantly in the Bulging Process according to the wall thickness linear model by calculating:

T=t ₀-bh, wherein t is each wall thickness constantly, t ₀Be the initial wall thickness of tubing, h is the bulging height of tubing, and b is constant; Wall thickness t when bulging is finished _EndWith bulging height h _EndSubstitution formula t=t ₀-bh can try to achieve the b value;

Step 6, by calculate obtaining the equivalent stress strain curve of tubing;

Equivalent stress is ${\mathrm{\σ}}_i=\sqrt{{\mathrm{\σ}}_{\mathrm{\θ}}^2-{\mathrm{\σ}}_{\mathrm{\θ}}{\mathrm{\σ}}_z+{\mathrm{\σ}}_z^2}$

σ wherein _θBe circumference stress; σ _zBe axial stress;

${\mathrm{\σ}}_{\mathrm{\θ}}=\frac{p({\mathrm{\ρ}}_{\mathrm{\θ}}-t)}{2t({\mathrm{\ρ}}_z-t/2)}(2{\mathrm{\ρ}}_z-{\mathrm{\ρ}}_{\mathrm{\θ}}-t)---\left(1\right)$

${\mathrm{\σ}}_z=\frac{p{({\mathrm{\ρ}}_{\mathrm{\θ}}-t)}^2}{2t({\mathrm{\ρ}}_{\mathrm{\θ}}-t/2)}---\left(2\right)$

ρ in the formula _θHoop radius-of-curvature for bulging district analysis site; ρ _zAxial curvature radius for bulging district analysis site;

Equivalent strain is ${\mathrm{\ϵ}}_i=2\sqrt{{\mathrm{\ϵ}}_{\mathrm{\θ}}^2+{\mathrm{\ϵ}}_{\mathrm{\θ}}{\mathrm{\ϵ}}_t+{\mathrm{\ϵ}}_t^2}/\sqrt{3}$

ε wherein _θBe hoop strain; ε _tFor thick to strain;

${\mathrm{\&epsiv;}}_{\mathrm{\&theta;}}=\ln \left(\frac{R_0+h-t/2}{R_0-{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="HDA00002769687200012.png"\; state="\{\{state\}\}">t</figure-callout>}}_0/2}\right)---\left(3\right)$

${\mathrm{\&epsiv;}}_t=\ln \left(\frac{t}{t_0}\right)---\left(4\right)$

Step 7, according to the equivalent stress strain curve, determine K value, n value and the tensile strength of pipe material to be tested.

The invention has the beneficial effects as follows:

Mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model of the present invention only needs before bulging begins and bulging finishes the rear analysis site wall thickness of measuring tubing, compare with existing mechanical properties of tubular goods hydraulic expanding-forming method of testing, only need measure twice wall thickness, the wall thickness of any time obtains by theoretical calculating in the Bulging Process, whole Bulging Process carries out continuously, the critical datas such as pressure, bulging height can be measured and record uninterruptedly, test easyly, greatly improved testing efficiency; Whole Bulging Process carries out continuously, and the mechanical property of tubing is not installed and loading or a plurality of sample performance is inconsistent affects the material property reliable results repeatedly; Experimentation need not to dissect tubing, utilizes a sample can directly obtain the mechanical property of tubing.

Description of drawings

Fig. 1 is the principle of work schematic diagram of mechanical properties of tubular goods hydraulic expanding-forming method of testing of the present invention, and Fig. 2 is the analytical calculation schematic diagram of mechanical properties of tubular goods hydraulic expanding-forming method of testing of the present invention.

Embodiment

Embodiment one: shown in Fig. 1～2, the mechanical properties of tubular goods hydraulic expanding-forming method of testing step based on the wall thickness linear model of present embodiment is as follows:

The initial wall thickness t of step 1, measurement tubing 1 to be tested ₀, tubing 1 to be tested external radius R ₀With bulging section length L ₀

Step 2, tubing 1 to be tested is placed between mold 2 and the bed die 3, and seals by the two ends that left sealing punch 4 and right sealing punch 5 are treated test tubing 1;

Step 3, be filled with high-pressure liquid medium 8 in tubing 1 to be tested, the pressure of high-pressure liquid medium 8 is 15～300MPa;

Pressure and the bulging height h of the high-pressure liquid medium 8 in step 4, real time record tubing 1 Bulging Process to be tested are until tubing to be tested 1 breaks;

The wall thickness of step 5, measurement tubing 1 breakdown point to be tested:

Obtain each wall thickness t constantly in the Bulging Process according to the wall thickness linear model by calculating:

T=t ₀-bh, wherein t is each wall thickness constantly, t ₀Be the initial wall thickness of tubing, h is the bulging height of tubing, and b is constant; Wall thickness t when bulging is finished _EndWith bulging height h _EndSubstitution formula t=t ₀-bh can try to achieve the b value;

Step 6, by calculate obtaining the equivalent stress strain curve of tubing;

Equivalent stress is ${\mathrm{\&sigma;}}_i=\sqrt{{\mathrm{\&sigma;}}_{\mathrm{\&theta;}}^2-{\mathrm{\&sigma;}}_{\mathrm{\&theta;}}{\mathrm{\&sigma;}}_z+{\mathrm{\&sigma;}}_z^2}$

σ wherein _θBe circumference stress; σ _zBe axial stress;

${\mathrm{\&sigma;}}_{\mathrm{\&theta;}}=\frac{p({\mathrm{\&rho;}}_{\mathrm{\&theta;}}-t)}{2t({\mathrm{\&rho;}}_z-t/2)}(2{\mathrm{\&rho;}}_z-{\mathrm{\&rho;}}_{\mathrm{\&theta;}}-t)---\left(1\right)$

${\mathrm{\&sigma;}}_z=\frac{p{({\mathrm{\&rho;}}_{\mathrm{\&theta;}}-t)}^2}{2t({\mathrm{\&rho;}}_{\mathrm{\&theta;}}-t/2)}---\left(2\right)$

ρ in the formula _θHoop radius-of-curvature for bulging district analysis site; ρ _zAxial curvature radius for bulging district analysis site;

Equivalent strain is ${\mathrm{\&epsiv;}}_i=2\sqrt{{\mathrm{\&epsiv;}}_{\mathrm{\&theta;}}^2+{\mathrm{\&epsiv;}}_{\mathrm{\&theta;}}{\mathrm{\&epsiv;}}_t+{\mathrm{\&epsiv;}}_t^2}/\sqrt{3}$

ε wherein _θBe hoop strain; ε _tFor thick to strain;

${\mathrm{\&epsiv;}}_{\mathrm{\&theta;}}=\ln \left(\frac{R_0+h-t/2}{R_0-{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="HDA00002769687200012.png"\; state="\{\{state\}\}">t</figure-callout>}}_0/2}\right)---\left(3\right)$

${\mathrm{\&epsiv;}}_t=\ln \left(\frac{t}{t_0}\right)---\left(4\right)$

Step 7, according to the equivalent stress strain curve, determine K value, n value and the tensile strength of tubing 1 material to be tested.In the present embodiment, the sealing at tubing two ends is to adopt to be pressed into the drift of the conical surface in the step 2

Tubing to be tested 1 two ends make it that enlarging occur and realize; Tubing initial wall thickness 0.5～2.5mm that experiment is tested, external diameter 25～100mm, length 100～360mm; When the K value of calculating tubing and n value, the stress-strain diagram of tubing adopts σ _i=K ε _i ⁿModel.

Embodiment two: as shown in Figure 1, the pressure that is filled with high-pressure liquid medium 8 in the step 3 in the tubing 1 to be tested is 30～200MPa.Other is identical with embodiment one.

Embodiment three: as shown in Figure 1, adopt supersonic thickness meter to measure the wall thickness of tubing 1 to be tested in step 1 and the step 5, the range ability of supersonic thickness meter is 0～20mm, and measuring accuracy is 0.01mm.Other is identical with embodiment one or two.

Embodiment four: as shown in Figure 1, in step 1, adopt the initial wall thickness of miking tubing; In step 5, the rupture location of tubing is cut the rear wall thickness that adopts miking tubing 1 to be tested.Other is identical with embodiment one or two.

Embodiment five: as shown in Figure 1, adopt tangent displacement sensor to measure the bulging height h of tubing 1 to be tested in the Bulging Process in step 4, the range ability of tangent displacement sensor is 0～50mm, and measuring accuracy is 0.05mm.Other is identical with embodiment one or two.

Embodiment six: as shown in Figure 1, in step 4, adopt laser displacement sensor to measure the bulging height h of tubing 1 to be tested in the Bulging Process, the range ability of laser displacement sensor is 0～50mm, and measuring accuracy is 0.01mm.Other is identical with embodiment one or two.

Claims (6)

1. mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model is characterized in that mechanical properties of tubular goods hydraulic expanding-forming method of testing step is as follows:

Step 1, measure the initial wall thickness t of tubing to be tested (1) ₀, tubing to be tested (1) external radius R ₀With bulging section length L ₀

Step 2, tubing to be tested (1) is placed between mold (2) and the bed die (3), and seals by the two ends that left sealing punch (4) and right sealing punch (5) are treated test tubing (1);

Step 3, be filled with high-pressure liquid medium (8) in tubing to be tested (1), the pressure of high-pressure liquid medium (8) is 15～300MPa;

Pressure and the bulging height h of the high-pressure liquid medium (8) in step 4, real time record tubing to be tested (1) Bulging Process are until tubing to be tested (1) breaks;

Step 5, measure the wall thickness of tubing to be tested (1) breakdown point:

Obtain each wall thickness t constantly in the Bulging Process according to the wall thickness linear model by calculating:

T=t ₀-bh, wherein t is each wall thickness constantly, t ₀Be the initial wall thickness of tubing, h is the bulging height of tubing, and b is constant; Wall thickness t when bulging is finished _EndWith bulging height h _EndSubstitution formula t=t ₀-bh can try to achieve the b value;

Step 6, by calculate obtaining the equivalent stress strain curve of tubing;

Equivalent stress is ${\mathrm{\&sigma;}}_i=\sqrt{{\mathrm{\&sigma;}}_{\mathrm{\&theta;}}^2-{\mathrm{\&sigma;}}_{\mathrm{\&theta;}}{\mathrm{\&sigma;}}_z+{\mathrm{\&sigma;}}_z^2}$

σ wherein _θBe circumference stress; σ _zBe axial stress;

${\mathrm{\&sigma;}}_{\mathrm{\&theta;}}=\frac{p({\mathrm{\&rho;}}_{\mathrm{\&theta;}}-t)}{2t({\mathrm{\&rho;}}_z-t/2)}(2{\mathrm{\&rho;}}_z-{\mathrm{\&rho;}}_{\mathrm{\&theta;}}-t)---\left(1\right)$

${\mathrm{\&sigma;}}_z=\frac{p{({\mathrm{\&rho;}}_{\mathrm{\&theta;}}-t)}^2}{2t({\mathrm{\&rho;}}_{\mathrm{\&theta;}}-t/2)}---\left(2\right)$

ρ in the formula _θHoop radius-of-curvature for bulging district analysis site; ρ _zAxial curvature radius for bulging district analysis site;

Equivalent strain is ${\mathrm{\&epsiv;}}_i=2\sqrt{{\mathrm{\&epsiv;}}_{\mathrm{\&theta;}}^2+{\mathrm{\&epsiv;}}_{\mathrm{\&theta;}}{\mathrm{\&epsiv;}}_t+{\mathrm{\&epsiv;}}_t^2}/\sqrt{3}$

ε wherein _θBe hoop strain; ε _tFor thick to strain;

${\mathrm{\&epsiv;}}_{\mathrm{\&theta;}}=\ln \left(\frac{R_0+h-t/2}{R_0-t_0/2}\right)---\left(3\right)$

${\mathrm{\&epsiv;}}_t=\ln \left(\frac{t}{t_0}\right)---\left(4\right)$

Step 7, according to the equivalent stress strain curve, determine K value, n value and the tensile strength of tubing 1 material to be tested.

2. the mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model according to claim 1 is characterized in that: the pressure that is filled with high-pressure liquid medium (8) in the step 3 in the tubing to be tested (1) is 30～200MPa.

3. the mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model according to claim 1 and 2, it is characterized in that: adopt supersonic thickness meter to measure the wall thickness of tubing to be tested (1) in step 1 and the step 5, the range ability of supersonic thickness meter is 0～20mm, and measuring accuracy is 0.01mm.

4. the mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model according to claim 1 and 2 is characterized in that: the initial wall thickness that adopts miking tubing in step 1; In step 5, the rupture location of tubing is cut the rear wall thickness that adopts miking tubing to be tested (1).

5. the mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model according to claim 1 and 2, it is characterized in that: in step 4, adopt tangent displacement sensor to measure the bulging height h of tubing to be tested (1) in the Bulging Process, the range ability of tangent displacement sensor is 0～50mm, and measuring accuracy is 0.05mm.

6. the mechanical properties of tubular goods hydraulic expanding-forming method of testing based on the wall thickness linear model according to claim 1 and 2, it is characterized in that: in step 4, adopt laser displacement sensor to measure the bulging height h of tubing to be tested (1) in the Bulging Process, the range ability of laser displacement sensor is 0～50mm, and measuring accuracy is 0.01mm.

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