Tubular sample mechanical property testing system and method

Abstract

The invention discloses a system and a method for testing mechanical properties of a tubular sample, and relates to the field of stress-strain testing, a tubular sample axial load loading unit is used for providing an axial load for the tubular sample and measuring the axial load of the tubular sample; the tubular sample internal pressure loading unit is used for providing internal pressure for the tubular sample and measuring the internal pressure of the tubular sample; the tubular sample internal pressure loading unit is connected with the tubular sample axial load loading unit; the data acquisition and processing unit is used for acquiring and measuring strain information of the tubular sample in the experiment process and calculating circumferential stress and axial stress according to the axial load, the internal pressure and the strain information; the stress path control unit is used for controlling the tubular sample axial load loading unit and the tubular sample internal pressure loading unit according to the circumferential stress and the axial stress so as to realize a tubular sample stress loading path in a complex stress state. According to the invention, the stress strain of the sample in any stress loading path in a complex stress state is rapidly measured.

Description

Technical Field

[0001] This application relates to the field of stress and strain testing, and particularly to a mechanical property testing system and method for tubular specimens. Background Art

[0002] With the rapid development of the manufacturing industry, the demand for complex-shaped components is increasing day by day, and the requirements for product quality are also constantly improving. These demands have put forward higher requirements for the accuracy of numerical simulation technology for forming. In this context, the material plastic forming analysis technology based on the finite element method and computer technology has become an important means to evaluate the forming performance of complex thin-walled metal components and optimize the die process. At present, uniaxial tensile tests are usually used to measure the stress-strain information of materials for finite element software to simulate the forming process. However, in the actual forming process, the material is usually in a complex stress state, and only using uniaxial tensile tests is not sufficient to accurately describe its deformation process. To achieve simulation results closer to the real deformation behavior, it is necessary to obtain the mechanical property data of the original blank under complex stress states. Summary of the Invention

[0003] The purpose of this application is to provide a mechanical property testing system and method for tubular specimens, which can accurately and quickly measure the stress and strain of specimens under any stress loading path in a complex stress state.

[0004] To achieve the above purpose, this application provides the following solutions:

[0005] In a first aspect, this application provides a mechanical property testing system for tubular specimens, including:

[0006] An axial load loading unit for tubular specimens, an internal pressure loading unit for tubular specimens, a data acquisition and processing unit, and a stress path control unit;

[0007] The axial load loading unit for tubular specimens is used to provide an axial load to the tubular specimen and measure the axial load of the tubular specimen; the internal pressure loading unit for tubular specimens is used to provide an internal pressure to the tubular specimen and measure the internal pressure of the tubular specimen; the internal pressure loading unit for tubular specimens is connected to the axial load loading unit for tubular specimens; the data acquisition and processing unit is respectively connected to the axial load loading unit for tubular specimens, the internal pressure loading unit for tubular specimens, and the stress path control unit; the data acquisition and processing unit is used to collect the strain information of the tubular specimen during the measurement experiment and calculate the circumferential stress and axial stress according to the axial load, the internal pressure, and the strain information; the stress path control unit is used to control the axial load loading unit for tubular specimens and the internal pressure loading unit for tubular specimens according to the circumferential stress and the axial stress to achieve the stress loading path of the tubular specimen under a complex stress state.

[0008] In one embodiment, the axial load loading unit of the tubular specimen includes: a test bench, a movable platform, a force sensor, a tubular specimen clamp, and a servo motor; the tubular specimen clamp includes an upper clamp for the tubular specimen and a lower clamp for the tubular specimen;

[0009] The force sensor is arranged between the movable platform and the upper clamp for the tubular specimen; the force sensor is used for measuring the axial load of the tubular specimen and sending the axial load to the data acquisition and processing unit; the lower clamp for the tubular specimen is installed on the test bench; the upper clamp for the tubular specimen and the lower clamp for the tubular specimen are used for clamping the tubular specimen; both the upper clamp for the tubular specimen and the lower clamp for the tubular specimen are connected to the internal pressure loading unit of the tubular specimen; the servo motor is respectively connected to the test bench, the movable platform, and the stress path control unit; the servo motor is used for controlling the movable platform to provide the axial load.

[0010] In one embodiment, the axial load loading unit of the tubular specimen further includes a laser measurement system; the laser measurement system includes a laser emitter, a laser receiver, and a position sensor;

[0011] Both the laser emitter and the laser receiver are arranged at the central position of the tubular specimen clamp; the position sensor is arranged on the laser receiver; the position sensor is used for detecting the offset of the laser beam between the upper clamp for the tubular specimen and the lower clamp for the tubular specimen so as to make the centers of the tubular specimen, the upper clamp for the tubular specimen, and the lower clamp for the tubular specimen on the same straight line.

[0012] In one embodiment, the axial load loading unit of the tubular specimen further includes a lead screw pair;

[0013] The lead screw pair is fixed at the output end of the servo motor; the lead screw pair is further connected to the movable platform.

[0014] In one embodiment, the internal pressure loading unit of the tubular specimen includes a digital hydraulic booster unit, a pressure relief module, and a pressure sensor;

[0015] The outlet of the digital hydraulic booster unit is respectively connected to the axial load loading unit of the tubular specimen and the pressure sensor; the digital hydraulic booster unit is further connected to the stress path control unit; the digital hydraulic booster unit is used for providing internal pressure to the tubular specimen; the pressure sensor is used for measuring the internal pressure of the tubular specimen;

[0016] The pressure relief module is respectively connected to the axial load loading unit of the tubular specimen and the stress path control unit; the pressure relief module is used for relieving the pressure inside the tubular specimen.

[0017] In one embodiment, the internal pressure loading unit of the tubular specimen further includes a pressure medium container, a filtration system, and a flow valve;

[0018] The flow valve is connected to the inlet of the digital hydraulic booster unit; the flow valve is also connected to the filtration system; the filtration system is also connected to the pressure medium container; the pressure medium container is also connected to the outlet of the pressure relief module.

[0019] In one embodiment, the data acquisition and processing unit includes a data processing unit and a strain data acquisition unit connected to the data processing unit;

[0020] The strain data acquisition unit is used to acquire the strain information of the tubular specimen during the measurement experiment; the data processing unit is also respectively connected to the axial load loading unit of the tubular specimen and the internal pressure loading unit of the tubular specimen.

[0021] In one embodiment, the stress path control unit includes a programmable logic controller and a motion controller connected to the programmable logic controller;

[0022] The motion controller is also respectively connected to the axial load loading unit of the tubular specimen and the internal pressure loading unit of the tubular specimen.

[0023] In one embodiment, the mechanical property testing system of the tubular specimen further includes a human-machine interaction unit; the human-machine interaction unit includes a display and an operation unit connected to the display;

[0024] The operation unit is also connected to the stress path control unit; the display is also connected to the data acquisition and processing unit.

[0025] In a second aspect, the present application provides a method for testing the mechanical properties of a tubular specimen. The method for testing the mechanical properties of the tubular specimen is applied to the mechanical property testing system of the tubular specimen, and the method for testing the mechanical properties of the tubular specimen includes:

[0026] Obtain a set stress path;

[0027] Determine a control mode according to the set stress path;

[0028] Control the axial load loading unit and the internal pressure loading unit of the tubular specimen according to the control mode and obtain the axial load, internal pressure and strain information until the tubular specimen fails.

[0029] According to the specific embodiments provided by the present application, the following technical effects are disclosed in the present application:

[0030] The present application provides a mechanical property testing system and method for tubular specimens. The axial load loading unit for tubular specimens is used to apply an axial load to the tubular specimens and measure the axial load of the tubular specimens; the internal pressure loading unit for tubular specimens is used to apply an internal pressure to the tubular specimens and measure the internal pressure of the tubular specimens; the internal pressure loading unit for tubular specimens is connected to the axial load loading unit for tubular specimens; the data acquisition and processing unit is respectively connected to the axial load loading unit for tubular specimens, the internal pressure loading unit for tubular specimens and the stress path control unit; the data acquisition and processing unit is used to acquire the strain information of the tubular specimens during the measurement experiment and calculate the circumferential stress and axial stress according to the axial load, the internal pressure and the strain information; the stress path control unit is used to control the axial load loading unit for tubular specimens and the internal pressure loading unit for tubular specimens according to the circumferential stress and the axial stress so as to realize the stress loading path of the tubular specimens under complex stress states. By applying an axial load and an internal pressure to the tubular specimens through the axial load loading unit for tubular specimens and the internal pressure loading unit for tubular specimens, and the stress path control unit controls the axial load loading unit for tubular specimens and the internal pressure loading unit for tubular specimens according to the circumferential stress and the axial stress, a control closed loop for the stress loading path is realized, thereby accurately and quickly measuring the stress-strain of the specimens under any stress loading path in complex stress states. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 Schematic diagram of the mechanical property testing system for tubular specimens;

[0033] Figure 2 Schematic diagram of the axial load loading unit for tubular specimens;

[0034] Figure 3 Schematic diagram of the internal pressure loading unit for tubular specimens;

[0035] Figure 4 Schematic diagram of the laser measurement system;

[0036] Figure 5 Schematic diagram of the data acquisition and processing unit;

[0037] Figure 6 Schematic diagram of the stress path control unit;

[0038] Figure 7 Flow chart of stress path control mode 1;

[0039] Figure 8 It is a flowchart of stress path control mode II;

[0040] Figure 9 It is a schematic diagram of the human - machine interaction unit.

[0041] Reference numerals:

[0042] Test bench - 1, lead screw pair - 2, movable platform - 3, force sensor - 4, upper chuck for tubular specimen - 5, lower chuck for tubular specimen - 6, servo motor - 7, laser measurement system - 8, laser emitter - 9, laser receiver - 10, position sensor - 11, pressure medium container - 12, filtration system - 13, flow valve - 14, digital hydraulic boosting unit - 15, pressure relief module - 16, pressure sensor - 17, tubular specimen - 18. Detailed implementation manners

[0043] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0044] Existing methods can obtain the stress - strain information of the biaxial stress state of a tubular specimen at a specific path by fixing the stress loading state. However, usually, multiple repeated experiments are required to obtain the global stress - strain information of the specimen, and the control method is single, the system response is slow, the stress - strain measurement error is large, and the human - machine interaction ability is weak. Therefore, there is an urgent need to establish a stress - strain test system and method for tubular specimens that can not only accurately, quickly, and directly measure but also achieve global stress path control, so as to realize the accurate, quick, and direct determination of the stress - strain of thin - walled metal tubes / sheets under any stress loading path in a complex stress state.

[0045] To make the above - mentioned objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0046] The purpose of the present application is to provide a system and method for accurately, quickly, and directly determining the stress - strain information of a tubular specimen under any stress loading path in a complex stress state. As Figure 1 shown, the present application provides a mechanical property test system for a tubular specimen. The specimen mechanical property test system includes: an axial load loading unit for the tubular specimen, an internal pressure loading unit for the tubular specimen, a data acquisition and processing unit, and a stress path control unit.

[0047] The axial load loading unit of the tubular specimen is used to provide an axial load to the tubular specimen 18 and measure the axial load of the tubular specimen 18; the internal pressure loading unit of the tubular specimen is used to provide an internal pressure to the tubular specimen 18 and measure the internal pressure of the tubular specimen 18; the internal pressure loading unit of the tubular specimen is connected to the axial load loading unit of the tubular specimen; the data acquisition and processing unit is respectively connected to the axial load loading unit of the tubular specimen, the internal pressure loading unit of the tubular specimen and the stress path control unit; the data acquisition and processing unit is used to collect the strain information of the tubular specimen 18 during the measurement experiment and calculate the circumferential stress and axial stress according to the axial load, the internal pressure and the strain information; the stress path control unit is used to control the axial load loading unit of the tubular specimen and the internal pressure loading unit of the tubular specimen according to the circumferential stress and the axial stress to realize the stress loading path of the tubular specimen 18 under a complex stress state.

[0048] An axial load and an internal pressure are applied to the tubular specimen 18 through the axial load loading unit of the tubular specimen and the internal pressure loading unit of the tubular specimen. The stress path control unit controls the axial load loading unit of the tubular specimen and the internal pressure loading unit of the tubular specimen according to the circumferential stress and the axial stress, realizing a closed-loop control of the stress loading path, so as to accurately and quickly measure the stress and strain of the specimen under any stress loading path in a complex stress state.

[0049] In an exemplary embodiment, as Figure 2 shown, the axial load loading unit of the tubular specimen includes: a test bench 1, a movable platform 3, a force sensor 4, a tubular specimen fixture and a servo motor 7; the tubular specimen fixture includes an upper chuck 5 for the tubular specimen and a lower chuck 6 for the tubular specimen.

[0050] The force sensor 4 is arranged between the movable platform 3 and the upper chuck 5 for the tubular specimen; the force sensor 4 is used to measure the axial load of the tubular specimen 18 and send the axial load to the data acquisition and processing unit; the lower chuck 6 for the tubular specimen is installed on the test bench 1; the upper chuck 5 for the tubular specimen and the lower chuck 6 for the tubular specimen are used to clamp the tubular specimen 18; both the upper chuck 5 for the tubular specimen and the lower chuck 6 for the tubular specimen are connected to the internal pressure loading unit of the tubular specimen; the servo motor 7 is respectively connected to the test bench 1, the movable platform 3 and the stress path control unit; the servo motor 7 is used to control the movable platform 3 to provide an axial load.

[0051] In practical applications, as Figure 4 shown, the axial load loading unit of the tubular specimen further includes a laser measurement system 8; the laser measurement system 8 includes a laser emitter 9, a laser receiver 10 and a position sensor 11.

[0052] The laser emitter 9 and the laser receiver 10 are both arranged at the central position of the tubular specimen fixture; the position sensor 11 is arranged on the laser receiver 10; the position sensor 11 is used to detect the offset of the laser beam between the upper chuck 5 and the lower chuck 6 of the tubular specimen so as to make the centers of the tubular specimen 18, the upper chuck 5 of the tubular specimen and the lower chuck 6 of the tubular specimen on the same straight line.

[0053] In practical applications, the axial load loading unit of the tubular specimen further includes a lead screw pair 2; the lead screw pair 2 is fixed to the output end of the servo motor 7; the lead screw pair 2 is also connected to the movable platform 3.

[0054] In practical applications, the specific connections and effects of the components in the axial load loading unit of the tubular specimen are as follows: the axial load loading unit of the tubular specimen provides a stable and accurate axial load for the tubular specimen 18 to be tested. Among them, the test bench 1 is a fixed platform, and the lower chuck 6 of the tubular specimen is installed on the fixed platform. The lower chuck 6 of the tubular specimen is used to clamp the tubular specimen 18. The servo motor 7 provides an accurate axial load output. The axis of the servo motor 7 is vertically arranged, and the lead screw pair 2 is fixed to the motor output end. The movable platform 3 is placed horizontally and is connected to the lead screw pair 2. A force sensor 4 is installed below the movable platform 3 to accurately measure the axial load. The upper chuck 5 of the tubular specimen is used to clamp the tubular specimen 18. The laser measurement system 8 includes a laser emitter 9, a laser receiver 10, and a position sensor 11. The laser emitter 9 and the receiver are installed at the central positions of the upper and lower chucks. The position sensor 11 is installed on the laser receiver 10 to detect the offset of the laser beam and feed the data back to the control system, which can dynamically adjust the installation position of the tubular specimen 18 to ensure that the center of the tubular specimen 18 and the axial load loading unit of the tubular specimen are on the same axis before and after installation, so that the load applied by the axial load loading unit of the tubular specimen is on the same straight line as the axis of the tubular specimen, reducing the installation error and improving the reliability of the test data.

[0055] In an exemplary embodiment, as Figure 3 shown, the internal pressure loading unit of the tubular specimen includes a digital hydraulic booster unit 15, a pressure relief module 16, and a pressure sensor 17.

[0056] The outlet of the digital hydraulic booster unit 15 is respectively connected to the axial load loading unit of the tubular specimen and the pressure sensor 17; the digital hydraulic booster unit 15 is also connected to the stress path control unit; the digital hydraulic booster unit 15 is used to provide internal pressure for the tubular specimen 18; the pressure sensor 17 is used to measure the internal pressure of the tubular specimen 18.

[0057] The pressure relief module 16 is respectively connected to the axial load loading unit of the tubular specimen and the stress path control unit; the pressure relief module 16 is used to relieve the pressure inside the tubular specimen 18.

[0058] In practical applications, the internal pressure loading unit of the tubular specimen further includes a pressure medium container 12, a filtration system 13, and a flow valve 14; the flow valve 14 is connected to the inlet of the digital hydraulic booster unit 15; the flow valve 14 is also connected to the filtration system 13; the filtration system 13 is also connected to the pressure medium container 12; the pressure medium container 12 is also connected to the outlet of the pressure relief module 16.

[0059] In practical applications, the internal pressure loading unit of the tubular specimen provides a stable and accurate internal pressure for the tubular specimen 18 to be tested. The pressure medium container 12 is used to store and recycle the pressure medium used during the experiment. The outlet of the pressure medium container 12 is connected to the inlet of the filtration system 13 through a pipeline. The filtration system 13 ensures the smoothness of the pipeline of the entire internal pressure loading unit of the tubular specimen and the safety of the experiment. The flow valve 14 is connected to the outlet of the filtration system 13 and is used to control the flow rate of the pressure medium, accurately adjust, stabilize or limit the flow rate of the pressure medium in the pipeline, and at the same time ensure that there is no backflow phenomenon. The digital hydraulic booster unit 15 includes three-level regulation: a coarse adjustment level (which can be realized by a variable frequency screw pump), a fine adjustment level (which can be realized by a piezoelectric microvalve array), and a dynamic balance level (which can be realized by a magnetorheological damper). The inlet of the digital hydraulic booster unit 15 is connected to the flow valve 14, the outlet is connected to the lower chuck 6 of the tubular specimen, and is also connected to the pressure sensor 17. The digital hydraulic booster unit 15 provides an internal pressure for the tubular specimen 18 and evacuates the air inside the tubular specimen 18, while ensuring that there is no backflow phenomenon and ensuring the stability of the internal pressure of the tubular specimen 18, improving the safety of the test. The upper chuck 5 of the tubular specimen is connected to the pressure relief module 16 and is used to control the internal pressure of the tubular specimen 18. When the internal pressure is too high, the pressure relief module 16 is activated to relieve a certain amount of pressure to ensure the accuracy of the test data. At the same time, the outlet of the pressure relief module 16 is connected to the pressure medium container 12, and the discharged pressure medium returns to the pressure medium container 12, realizing the recycling of the pressure medium and improving the economy of the test. This unit accurately controls the output volume of the pressure medium through the digital hydraulic booster unit 15 and the pressure relief module 16, with higher output accuracy and higher test safety than traditional boosters.

[0060] The pressure medium can be pure water, emulsion, or hydraulic oil.

[0061] Specifically, after the experiment starts, the digital hydraulic booster unit 15 determines the current working level according to the preset stress path: when the circumferential stress is lower than 30% of the preset value, the coarse adjustment level is used, and the variable frequency screw pump receives the pressure set value and outputs quickly to establish the basic pressure; when the circumferential stress reaches within ±5% of the preset value, it switches to the piezoelectric stack-driven microvalve array (response time ≤ 1 ms, flow resolution 0.01 mL / s), and realizes the adjustment accuracy of ±0.1 MPa through micro-flow compensation; when the circumferential pressure needs to be maintained, due to the change of the axial load, pressure pulsation may occur, and the magnetorheological fluid damper stabilizer is enabled, combined with the closed-loop feedback of the pressure sensor 17 (control period 10 ms), to suppress the pulsation amplitude within ±0.05 MPa.

[0062] In an exemplary embodiment, as Figure 5 shown, the data acquisition and processing unit includes a data processing unit and a strain data acquisition unit connected to the data processing unit; the strain data acquisition unit is used to acquire the strain information of the tubular specimen 18 during the measurement experiment; the data processing unit is also respectively connected to the axial load loading unit of the tubular specimen and the internal pressure loading unit of the tubular specimen.

[0063] In practical applications, the strain data acquisition unit can measure the strain information of the tubular specimen 18 during the experiment in real time. The data processing unit processes the strain information of the tubular specimen 18 obtained by the strain data acquisition unit, the axial load information measured by the force sensor 4, and the internal pressure information measured by the pressure sensor 17 to obtain the circumferential stress and axial stress information of the tubular specimen 18 in real time. The data acquisition and processing unit provides stress path control input information (including the circumferential stress and axial stress of the tubular specimen 18) for the stress path control unit, providing data support for accurately controlling the complex stress loading path. The data acquisition and processing unit provides visual display information for the human-machine interaction unit, including real-time strain information, axial load, internal pressure, axial stress, and circumferential stress. The strain data acquisition unit can measure the strain data of the tubular specimen 18 by using the laser speckle interferometry method, DIC optical measurement, or by pasting strain gauges on the tubular specimen. Specifically, the strain data acquisition unit can be a strain gauge measurement system, a laser speckle interferometry system, or an optical speckle measurement system to obtain accurate axial and circumferential strain information of the tubular specimen 18 to be measured.

[0064] In an exemplary embodiment, as Figure 6 shown, the stress path control unit includes a programmable logic controller and a motion controller connected to the programmable logic controller; the motion controller is also respectively connected to the axial load loading unit of the tubular specimen and the internal pressure loading unit of the tubular specimen.

[0065] In practical applications, the stress path control unit realizes the stress loading path of the tubular specimen 18 under complex stress states required by users by controlling the axial load loading unit and the internal pressure loading unit of the tubular specimen. The programmable logic controller allocates control resources and performs control logic processing; the motion controller controls the servo motor 7, the pressure relief module 16, and the digital hydraulic booster unit 15 to achieve high-precision motion control; the programmable logic controller realizes the complex stress loading path given by the user through the motion controller.

[0066] The stress path control unit has two control modes:

[0067] As Figure 7 shown, Control Mode 1: Circumferential stress tracking mode. Set the required stress path, the axial load increment ΔF, and the circumferential stress control accuracy ΔB (ΔB > 0); start the experiment, increase the axial load by ΔF, the data acquisition and processing unit receives the force information F, the internal pressure information p, and the strain information ε, and calculates the real-time axial stress A and circumferential stress B of the tubular specimen 18; the stress path control unit reads the preset stress path and calculates the preset value B of the circumferential stress corresponding to the real-time axial stress A. p When B < B p - ΔB, the digital hydraulic booster unit 15 accelerates, the internal pressure of the tubular specimen 18 increases, and then reads the current real-time axial and circumferential stress values until the control accuracy B ∈ [B p - ΔB, B p + ΔB]; when B > B p + ΔB, the pressure relief module 16 is opened, the internal pressure of the tubular specimen 18 decreases, and then reads the current real-time axial and circumferential stress values until the control accuracy B ∈ [B p - ΔB, B p + ΔB]; when the control accuracy B ∈ [B p - ΔB, B p + ΔB] is satisfied, the axial load is increased by an increment ΔF to complete the stress path loading required by the user until the tubular specimen 18 ruptures and the experiment ends.

[0068] As Figure 8 shown, Control Mode 2: Axial stress tracking mode. Set the required stress path, the internal pressure increment Δp (Δp > 0), and the circumferential stress control accuracy ΔA (ΔA > 0); start the experiment, increase the internal pressure by Δp, the data acquisition and processing unit receives the force information F, the internal pressure information p, and the strain information ε, and calculates the real-time axial stress A and circumferential stress B of the tubular specimen 18; the stress path control unit reads the preset stress path and calculates the preset value A of the axial stress corresponding to the real-time circumferential stress B. p When A < A p-ΔA, the servo motor 7 accelerates, the axial load of the tubular specimen increases, and the current real-time axial and circumferential stress values are read until the control accuracy A ∈ [A p -ΔA,A p +ΔA]; when A > A p -ΔA, the servo motor 7 decelerates, the axial load of the tubular specimen decreases, and the current real-time axial and circumferential stress values are read until the control accuracy A ∈ [A p -ΔA,A p +ΔA]; when the control accuracy A ∈ [A p -ΔA,A p +ΔA] is satisfied, the internal pressure increases by an increment Δp, and the stress path loading required by the user is completed until the tubular specimen 18 ruptures and the experiment ends.

[0069] In an exemplary embodiment, as Figure 9 shown, the mechanical property testing system of the tubular specimen further includes a human-computer interaction unit; the human-computer interaction unit includes a display and an operation unit connected to the display; the operation unit is also connected to the stress path control unit; the display is also connected to the data acquisition and processing unit.

[0070] In practical applications, the human-computer interaction unit can intuitively display real-time strain information, axial load, internal pressure, axial stress, and circumferential stress, and provide a control operation interface. Users can conveniently and quickly operate each loading unit, view real-time calculated values, and set the required stress loading path. The human-computer interaction unit can visually display the stress loading path and the stress-strain results of complex stress states in the form of graphs and tables.

[0071] In practical applications, the tubular specimen 18 can be a hot-rolled, cold-rolled, or extruded thin-walled tube, or a seam-welded tube, or can also be formed by rolling and welding thin-walled plates into the tubular specimen 18.

[0072] In an exemplary embodiment, there is a preset stress path in the stress path control unit. The preset stress path is a preset function or a fixed value, and there is also an actual loaded stress path. By controlling the axial load and internal pressure in a closed loop, the actual stress path of the specimen is loaded according to the set stress path.

[0073] The present application has the following beneficial effects:

[0074] (1) It can quickly and accurately measure the axial load and internal pressure, and quickly feedback to the stress path control unit. Through the precise control structure with fast response, the real-time coupling and linkage closed-loop feedback control of the stress path, axial load, and internal pressure is realized, so as to realize the real-time, accurate, fast, and direct measurement of the stress-strain of any stress loading path of the tubular specimen under complex stress states.

[0075] (2) The precision electro-hydraulic flow valve and the digital hydraulic booster unit can accurately control the volume of the pressure medium inside the tubular specimen, realizing accurate control of the internal pressure of the medium.

[0076] (3) The laser measurement system can ensure that during the experiment, the direction of the axial loading force is always in a straight line with the axis direction of the tubular specimen, avoiding experimental errors caused by non-alignment and improving the reliability of the experimental data.

[0077] (4) The pipeline is pre-filled with the pressure medium and the gas in the whole pipeline is emptied, effectively preventing the metal peeling caused by the bursting of the bubbles in the pressure medium under high pressure, thus damaging the formed part; when the tubular specimen ruptures, there will be no air leakage noise of high-pressure gas and splashing of the pressure medium, improving the safety of the experiment.

[0078] (5) Its closed pipeline design enables the pressure medium to meet the standard of recycling after passing through the filtration system, solving the problem of pressure medium discharge, making the test economical, environmentally friendly and safe.

[0079] (6) The control mode can effectively avoid the impact load applied to the axis of the tubular specimen caused by the repeated start and stop of the servo motor, improving the reliability of the experimental data.

[0080] (7) The human-computer interaction unit is easy to operate, which can not only realize the intuitive display of real-time stress-strain information and process control information, but also conveniently set control parameters, measurement parameters and stress paths.

[0081] (8) It can not only be directly used for the mechanical property test of pipes under complex stress states, but also realize the accurate determination of the stress-strain curve in a large strain range under biaxial stress states of thin-walled plates by rolling and welding the thin-walled plates into tubular specimens, thus providing reliable experimental data support for the establishment of constitutive relations of anisotropic materials under biaxial loading conditions.

[0082] Based on the same inventive concept, the embodiment of the present application also provides a tubular specimen mechanical property test device for realizing the tubular specimen mechanical property test method involved above. The implementation solutions provided by this device to solve problems are similar to those recorded in the above method. Therefore, the specific limitations in one or more embodiments of the tubular specimen mechanical property test device provided below can refer to the limitations on the tubular specimen mechanical property test method in the above text and will not be elaborated here.

[0083] In an exemplary embodiment, a tubular specimen mechanical property test method is provided. The tubular specimen mechanical property test method is applied to the tubular specimen mechanical property test system, and the tubular specimen mechanical property test method includes:

[0084] Obtain the set stress path.

[0085] Determine the control mode according to the set stress path.

[0086] Control the axial load loading unit and the internal pressure loading unit of the tubular specimen according to the control mode, and obtain the axial load, internal pressure and strain information until the tubular specimen fails.

[0087] In practical applications, the present application also provides a method for testing the mechanical properties of a tubular specimen, and the specific steps are as follows:

[0088] Step 1: Prepare a tubular specimen to be tested with an appropriate length according to the test requirements.

[0089] Step 2: Select appropriate upper and lower chucks according to the inner diameter of the tubular specimen, connect the tubular specimen with the upper and lower chucks, and ensure its sealing performance. Install it on the axial load loading unit of the tubular specimen. After installation, the laser measurement system calibrates whether the centers of the tubular specimen and the axial load loading unit of the tubular specimen are on the same axis, and adjusts the tubular specimen to the optimal position.

[0090] Step 3: The man-machine interaction unit controls the pressure relief module to open, first fills the inside of the tubular specimen with a liquid pressure medium, closes the pressure relief module, inputs the required stress path, and selects an appropriate control mode.

[0091] Step 4: Start the experiment through the man-machine interaction unit. The experiment is automatically carried out. As the axial load and internal pressure increase, the bulging amount of the tubular specimen gradually increases. The data acquisition and processing unit automatically processes the experimental process data in real time, and the man-machine interaction unit displays the measurement results and process control information in real time.

[0092] Step 5: Until the tubular specimen ruptures, automatically store the experimental data of the whole process, disassemble the tubular specimen to be tested, clean the experimental site, and observe and analyze the experimental results.

[0093] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0094] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A tubular specimen mechanical properties testing system, characterized in that: The sample mechanical property testing system comprises: a tubular sample axial load loading unit, a tubular sample internal pressure loading unit, a data acquisition and processing unit, and a stress path control unit; The tubular specimen axial load loading unit is used to provide an axial load to the tubular specimen and measure the axial load of the tubular specimen; the tubular specimen internal pressure loading unit is used to provide an internal pressure to the tubular specimen and measure the internal pressure of the tubular specimen; the tubular specimen internal pressure loading unit is connected to the tubular specimen axial load loading unit; the data acquisition and processing unit is respectively connected to the tubular specimen axial load loading unit, the tubular specimen internal pressure loading unit and the stress path control unit; the data acquisition and processing unit is used to collect strain information of the tubular specimen during the experiment and calculate the annular stress and axial stress according to the axial load, the internal pressure and the strain information; the stress path control unit is used to control the tubular specimen axial load loading unit and the tubular specimen internal pressure loading unit according to the annular stress and the axial stress to realize the stress loading path of the tubular specimen under a complex stress state.

2. The tubular specimen mechanical properties testing system according to claim 1, characterized in that: The tubular specimen axial load loading unit comprises: a test bench, a movable platform, a force sensor, a tubular specimen fixture and a servo motor; the tubular specimen fixture comprises an upper tubular specimen chuck and a lower tubular specimen chuck; The force sensor is arranged between the movable platform and the upper chuck of the tubular specimen; the force sensor is used to measure the axial load of the tubular specimen and send the axial load to the data acquisition and processing unit; the lower chuck of the tubular specimen is installed on the test bench; the upper chuck of the tubular specimen and the lower chuck of the tubular specimen are used to clamp the tubular specimen; the upper chuck of the tubular specimen and the lower chuck of the tubular specimen are both connected to the tubular specimen internal pressure loading unit; the servo motor is respectively connected to the test bench, the movable platform and the stress path control unit; the servo motor is used to control the movable platform to provide an axial load.

3. The tubular specimen mechanical properties testing system according to claim 2, characterized in that: The tubular specimen axial load loading unit further comprises a laser measurement system; the laser measurement system comprises a laser transmitter, a laser receiver and a position sensor; The laser transmitter and the laser receiver are both arranged at the center position of the tubular sample fixture; the position sensor is arranged on the laser receiver; the position sensor is used to detect the offset of the laser beam between the upper chuck of the tubular sample and the lower chuck of the tubular sample so as to realize that the centers of the tubular sample, the upper chuck of the tubular sample and the lower chuck of the tubular sample are in the same straight line.

4. The tubular specimen mechanical properties testing system according to claim 2, characterized in that: The tubular specimen axial load loading unit also includes a screw pair; The lead screw pair is fixed at the output end of the servo motor; the lead screw pair is also connected to the movable platform.

5. The tubular specimen mechanical properties testing system according to claim 1, characterized in that: The tubular specimen internal pressure loading unit comprises a digital hydraulic booster unit, a pressure relief module and a pressure sensor; The outlet of the digital hydraulic booster unit is connected to the tubular specimen axial load loading unit and the pressure sensor respectively; the digital hydraulic booster unit is also connected to the stress path control unit; the digital hydraulic booster unit is used to provide internal pressure to the tubular specimen; the pressure sensor is used to measure the internal pressure of the tubular specimen; The pressure relief module is connected to the tubular specimen axial load loading unit and the stress path control unit respectively; the pressure relief module is used to relieve the pressure in the tubular specimen.

6. The tubular specimen mechanical properties testing system according to claim 5, characterized in that: The tubular specimen internal pressure loading unit also includes a pressure medium container, a filtering system and a flow valve; The flow valve is connected to the inlet of the digital hydraulic booster unit; the flow valve is also connected to the filter system; the filter system is also connected to the pressure medium container; the pressure medium container is also connected to the outlet of the pressure relief module.

7. The tubular specimen mechanical properties testing system according to claim 1, characterized in that: The data acquisition and processing unit includes a data processing unit and a strain data acquisition unit connected to the data processing unit; The strain data acquisition unit is used to collect strain information of the tubular sample during the measurement experiment; the data processing unit is also connected to the tubular sample axial load loading unit and the tubular sample internal pressure loading unit respectively.

8. The tubular specimen mechanical properties testing system according to claim 1, characterized in that: The stress path control unit includes a programmable logic controller and a motion controller connected to the programmable logic controller; The motion controller is also connected to the tubular specimen axial load loading unit and the tubular specimen internal pressure loading unit respectively.

9. The tubular specimen mechanical properties testing system according to claim 1, characterized in that: The tubular specimen mechanical property testing system further comprises a human-computer interaction unit; the human-computer interaction unit comprises a display and an operating unit connected to the display; The operating unit is also connected to the stress path control unit; the display is also connected to the data acquisition and processing unit.

10. A method for testing mechanical properties of a tubular specimen, characterized in that: The tubular specimen mechanical properties testing method is applied to the tubular specimen mechanical properties testing system according to any one of claims 1 to 9, and the tubular specimen mechanical properties testing method comprises: Get the set stress path; determining a control mode according to the set stress path; According to the control mode, the tubular specimen axial load loading unit and the tubular specimen internal pressure loading unit are controlled to obtain axial load, internal pressure and strain information until the tubular specimen is destroyed.

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