CN105806709A - Pipe property testing method and pipe property testing equipment - Google Patents

Abstract

The invention discloses a pipe property testing method and pipe property testing equipment. During the test, displacement and thrust at two ends of a pipe are controlled, and liquid pressure is applied to the interior of the pipe. In the expanding process, a strain state of the pipe is monitored in real time by utilizing a digital speckle metrology technique, and the thrust or displacement is adjusted. When equivalent strain reaches a certain value or the pipe is broken, the test is stopped. In the test process, liquid filling pressure in the pipe and expanding height around the highest pipe expansion point are recorded, and the stress-strain curve and forming limit of the pipe are calculated by combining real-time strain measurement data. A pipe test piece is clamped and sealed in a triangular chuck and bushing manner, and convenient test piece installation is realized.

Description

A kind of pipe performance method of testing and equipment

Technical field

The invention belongs to material properties test technical field, particularly relate to test method and the equipment of a kind of pipe material performance test.

Background technology

Tubing part is widely used in the industry such as Aero-Space, automobile making due to the feature that its stock utilization is high, production cost is low.Along with the development of Technology, traditional tensile test method can not meet the requirement of complicated analysis of forming technique.For the weak point that pipe material performance test methods exists, the present invention proposes a kind of material parameter being combined based on the real-time strain measurement of pipe liquid filled bulging and digital speckle and forming limit measuring method and equipment.The method can be passed through to design different load paths, material parameter is verified disease and draws forming limit diagram (FLD) and stress shaping and line chart (FLSD).

Summary of the invention

It is an object of the invention to provide the test method of a kind of pipe material performance test being combined based on the real-time strain measurement of pipe liquid filled bulging and digital speckle and equipment, obtain reliable pipe material parameter, stress-strain diagram and forming limit diagram etc., provide reliable reference frame for technological design.

The present invention provides a kind of pipe material method of testing and equipment, it is characterised in that: use the method for topping up bulging to make tubing dilatancy.In deformation process, use 3-dimensional digital speckle measurement technique that the strained situation in tube bulge process is carried out real-time measurement.Meanwhile, the deformation using the three foot displacement chis peak place to expanding carries out subsidiary and feeds back deformation information.Pressure transducer records pressure change procedure in pipe liquid filled Bulging Process.Control system is passed through the real-time measurements to deformation process and is regulated the amount of feeding of bulging pressure and both sides according to the stress of experimental design or strain index.Realize drafting and the deformation process analysis of pipe material stress-strain relation, forming limit diagram and shaping limiting range of stress figure.More complete description pipe material performance.

Accompanying drawing explanation

Fig. 1 clamping parts

1-transfer panel, 2-tri-foot chuck, 3-supports axle center, 4-gathering sill

Fig. 2 thruster cylinder part

1-cylinder putter, 2-oil drain out, 3-displacement transducer, 4-cylinder block

Fig. 3 tri-foot displacement chi

1-displacement chi, 2-inner sleeve, 3-outer sleeve, 4-installs bolt

Fig. 4 three dimensional strain measures parts

1-video camera, 2-LED light source, 3-spider

Fig. 5 Bulging Process

T-peak thickness, ρ_z-axial outer wall radius of curvature, ρ_θ-peripheral outer wall radius of curvature, ρ₀-initial inwall radius of curvature

Fig. 6 peak stress state

σ_z-axial stress, σ_θ-circumferential stress

The curved swollen performance test of Fig. 7

1-guide rail axis of rotation, hole, 2-angle location

Fig. 8 peak strain regime

ε_z-axial strain, ε_θ-circumferential strain, ε_t-thick in strain

Specific embodiments

The present invention can complete tubing stock performance test, it is possible to bending tube bulge performance is tested.

Stock performance test uses straight tube bulging to test.First tubing is carried out pretreatment.Spraying white, black paint successively to the zone line of tubing test specimen, manufacture of intraocular speckle field, in order to the three-dimensional speckle strain measurement of the overall situation.

Adjustment Tests machine, clamping test specimen.Thruster oil cylinder is connected with clamping parts by transfer panel, and by guide rails assembling to guide plate, ensures the thrust conllinear at tubing two ends.Tubing test specimen one end is installed by the triangle chuck in clamping parts and is clamped.Controlled the thruster oil cylinder of opposite side by control software design, near test specimen, pipe end is pressed in support mandrel and clamps.The thruster oil cylinder of synchronization control both sides, makes tubing test specimen be centrally located at the middle chi of three foot displacement chis once.Adjust the height of displacement chi, after making displacement chi contact with test specimen, to its zeros data.

Three-dimensional speckle strain measurement system is installed.Ensure horizontal line and the test specimen centrage less parallel of measurement system.Scaling board () is placed and near test specimen, carries out stereo calibration to measuring system camera.

Obtain pipe material stress strain curve.As shown in Figure 8, the circumferential strain of test specimen bulging peak can be expressed as:

${\mathrm{\ϵ}}_{\mathrm{\θ}}=\ln \frac{h+{\mathrm{\ρ}}_0}{{\mathrm{\ρ}}_0}$

Axial strain can be expressed as:

${\mathrm{\ϵ}}_z=\ln \frac{l}{l_0}$

Principle according to plastic deformation constancy of volume, equivalent strain can be expressed as:

$\stackrel{\‾}{\mathrm{\ϵ}}=\frac{\sqrt{2}}{3}\sqrt{{{\mathrm{\ϵ}}_{\mathrm{\θ}}}^2+{{\mathrm{\ϵ}}_z}^2+{\mathrm{\ϵ}}_z{\mathrm{\ϵ}}_{\mathrm{\θ}}}$

Meanwhile, the thickness of peak can be expressed as:

$t=t_0{e}^{-{\mathrm{\ϵ}}_z-{\mathrm{\ϵ}}_{\mathrm{\θ}}}$

Therefore peak axial stress can be obtained according to axial equilibrium equation:

${\mathrm{\σ}}_z=\frac{p\·s-F}{2\mathrm{\π}(h+{\mathrm{\ρ}}_0)t}$

In test, servo-control system ensures p s-F=0.With reference to the accompanying drawings 6, circumferential stress can be in the hope of:

${\mathrm{\σ}}_{\mathrm{\θ}}=(\frac{p}{t}-\frac{{\mathrm{\σ}}_z}{{\mathrm{\ρ}}_z})\×{\mathrm{\ρ}}_{\mathrm{\θ}}$

According to thin-walled theory, test specimen normal stress can be ignored, and therefore can obtain Mises stress:

$\stackrel{\‾}{\mathrm{\σ}}-\sqrt{{{\mathrm{\σ}}_{\mathrm{\θ}}}^2+{{\mathrm{\σ}}_z}^2-{\mathrm{\σ}}_{\mathrm{\θ}}{\mathrm{\σ}}_z}$

In deformation process, real-time monitor stress strain, by organize more stress-strain to and select suitable material model can set up pipe material stress strain curve.Simultaneously being obtained corresponding equivalent strain by three-dimensional speckle strain measurement system can strain variation process in deformation process in proof procedure.The advantage of three-dimensional speckle strain measurement system is in that can the stably multi-direction strain in measurement of full field deformation process, it is to avoid impact, in mechanical measurement, the error caused.

Forming limit diagram is with principal strain ε in face₁, ε₂For axle in length and breadth in order to judge the index of the maximum compressive yield strength of material.The invention provides a kind of method that multiple spot sets up forming limit diagram.According to tube outer diameter d, set the ratio respectively 8: 1 of test piece deformation section length l and d, 6: 1,5: 1,4: 1,3: 1 bulging tests being fixed two sections, owing to the peak axial strain of fixing end bulging test and the ratio of circumferential strain are similar to constant, therefore 5 forming limit points are obtained, thus drawing forming limit diagram.

Research finds, forming limit diagram is inaccurate for the fracturing shape in nonlinear strain path, and the method shaping limiting range of stress figure is developed.The invention provides the method for testing shaping the limiting range of stress.Owing to axial stress is directly determined by side-thrust F, therefore the ratio by adjustment F and p s is 0.8,0.9,1.0,1.1,1.2 five group of test, draws biaxial stress change procedure in forming process identified sign forming limit.

A kind of method that present invention also offers bending pipe fitting bulging limit.As attempted 7, Adjustment Tests machine guide rail is identical with the angle of test specimen after bending.By CNC tube bending machine, three groups of tubing test specimens are curved, make weld seam be respectively in curved outside, bending and survey and vertical and plane of bending.The clamping parts at tubing two ends keep fixing, and three groups of test specimens are carried out free bulge test.Use three-dimensional speckle strain measurement system to measure the deformation process of test specimen in real time, analyze weld seam and the impact bent bulging.

Claims (1)

1. it is an object of the invention to provide one utilizes topping up expanding method that pipe material performance carries out test equipment and method.The material property of straight tube Yu prebuckling tubing can be tested by the method, obtain pipe liquid filled shaping overall process stress-strain relation, and obtain shape strain limit and shape the limiting range of stress.

Technical scheme is as follows:

1. the equipment of pipe liquid filled bulging material properties test: it is characterized in that: this equipment includes three-dimensional speckle strain testing equipment (4) for recording and analyze Bulging Process, the hydraulic-pressure control apparatus (2) of pipe liquid filled bulging, for promoting the thruster equipment (2) of test specimen tubing two ends axial shrinkage, pipe end apparatus for fastening (1) suitable in multiple diameter, for the real-time bulging height measuring equipment (5) of straight tube performance test, tubing is for the scalable pipe guide (7) of adaptive testing test specimen angle of bend.

Assembly 1: end clamping parts, is made up of connecting plate, three foot chucks, support plug and guide-track groove.Connecting plate is connected with assembly 2 lateral thruster.Three foot chucks step up tubing test specimen jointly with supporting plug.Guide rail is connected with group valency 5 guide rail platform and can at slide on rails.

Assembly 2: hydraulic-pressure control apparatus and lateral thruster, is made up of servo valve, hydraulic cylinder, hydraulic push rod and control system.Two kinds of control models, force control mode and speed control mode are provided.Under force control mode, hydraulic system is provided as the side-thrust that testing machine provides both sides identical or different as requested；Under speed control mode, hydraulic system provides the thruster speed that both sides are identical or different as requested.

Assembly 3: three foot displacement chi.It is connected with assembly 5 guide rail platform, it is possible to regulate height.For recording the height of peak periphery during straight line tubing test piece deformation.

Assembly 4: three-dimensional speckle strain testing equipment, is made up of three-dimensional speckle deformation process record camera and dedicated analysis software.Wherein two cameras can be fixed on moveable triangle foot or be fixed on the portal frame of testing machine.

Assembly 5: guide rail platform.On guide rail platform with around central rotation device and utilize location hole determine components above position.And lateral thruster setting angle can be adjusted according to test piece angle.

2. the method for pipe liquid filled bulging material properties test, its special type is in that the method comprises the following steps:

First, guide rail platform angle is adjusted according to test piece angle.Adjust hydraulic pressure and lateral thruster clamping test specimen.

Adjust three-dimensional speckle strain testing equipment to optimum field scope.For straight line tubing test specimen, adjust three foot displacement chis to contact test specimen and by numerical value clearing.

Adopt Bit andits control or side-thrust control method that test specimen is loaded according to requirement of experiment.And record measurement data.Stress-strain diagram and forming limit is calculated according to computing formula.