A plate and pipe compression performance testing device and method

Abstract

The present invention relates to a plate and pipe compression performance testing device and method, belonging to the technical field of testing devices. It includes a compression die and a strain sensor; the compression die includes a lower die and an upper die, the profile of the lower die is a concave 1 / 4 elliptical cylinder, and a stopper is provided along the lower edge of the concave elliptical cylinder; the profile of the upper die is a concave 1 / 4 elliptical cylinder, and a stopper is provided along the upper edge of the concave elliptical cylinder; the upper die and the lower die are connected by a guide positioning mechanism, and the upper die can slide relative to the lower die; the upper die is provided with a force sensor; the strain sensor is a contact strain gauge or a non-contact strain gauge, which is used to detect the compression performance of the sample to be tested. The present invention also relates to a method for testing the compression performance of pipes / plates using a testing device. The present invention adopts the currently common universal testing machine for testing, and the equipment is mature and stable; the testing device is simple and easy to operate, low in cost, and has good versatility.

Description

Technical Field

[0001] The invention belongs to the technical field of testing devices, and in particular relates to a device and method for testing the compression performance of plates and pipes. Background Art

[0002] Common sheet metal forming processes such as stamping and deep drawing are tensile deformations, and the material deforms under tensile stress. With the development of process technology, the evaluation of the tensile properties of metal materials has become extremely comprehensive, such as room temperature stretching, high temperature stretching, FLC testing, high-speed stretching testing, etc. As for the compression properties of materials, there is currently only compression performance testing of bar materials.

[0003] In recent years, a new forming process has emerged - pipe pressure upsetting, which is an obvious compression deformation. The material is deformed by three-dimensional compressive stress. Plates and pipes are very likely to become unstable and wrinkled when under pressure, making it impossible to test the compression performance of plates / pipes. Therefore, tensile performance parameters are used to estimate the process parameters of pressure upsetting. However, the tensile and compressive properties of metal materials are not consistent, so engineers cannot accurately judge the process parameters. Summary of the invention

[0004] In view of the problem that the compression performance of plates / tubes cannot be tested in the prior art, the present invention provides a plate and tube compression performance testing device and method. The plate / tube compression performance testing device and method of the present invention are based on the compression principle. The device is simple, low-cost, and has a simple operation process, and has a very high application prospect.

[0005] The technical solution of the present invention is as follows:

[0006] A plate and pipe compression performance testing device, comprising a compression die and a strain sensor; the compression die comprises an upper die and a lower die opposite to each other; the profile of the upper die is a concave 1 / 4 elliptical cylinder, and a stopper is provided along the upper edge of the concave elliptical cylinder; the profile of the lower die comprises a concave 1 / 4 elliptical cylinder and a vertical surface located above the elliptical cylinder, and a stopper is provided along the lower edge of the concave elliptical cylinder; the upper die and the lower die are connected by a guide positioning mechanism, and the upper die can slide relative to the lower die; the upper die is provided with a force sensor;

[0007] The strain sensor is a contact strain gauge or a non-contact strain gauge, and is used to detect the compression performance of the sample to be tested.

[0008] Preferably, the contact strain gauge uses a strain gauge, which is vertically attached to the middle part of the inner surface of the sample to be tested when in use; the non-contact strain gauge uses a DIC system, and the inner surface of the sample to be tested is sprayed with speckles when in use.

[0009] The sample to be tested is a semicircular plate or a U-shaped plate, the outer surface of which is polished and coated with a lubricating medium.

[0010] The plate and pipe compression performance testing device of the present invention is installed on a universal testing machine for use.

[0011] The method for testing pipes using the above compression performance testing device is as follows:

[0012] (1) Select a test device of appropriate specifications, where the width of the upper die and the lower die is W;

[0013] (2) Cut a section of round tube with a length of w, w≤W, cut it along the diameter of the tube, take a section of semicircular tube, polish the outer surface, and apply lubricating medium;

[0014] (3) The upper die of the test device is pressed down without load, and the friction force of the compression device itself is measured as F0;

[0015] (4) Place the semicircular tube between the upper die and the lower die, and move the upper die downward until the outer surface of the semicircular tube is completely fitted with the die to form a U-shaped plate. The pressure at this time is recorded as F1;

[0016] (5) The test begins. The upper pressure block continues to move downward, and the pressure F and vertical compressive strain ε are collected at the same time. y , the true strain is ε=ln(1+ε y ), the true stress is σ=(F-F1) / (wt(1-ε y )), the two correspond to obtain the true stress-strain curve, where t is the thickness of the pipe.

[0017] Preferably, the length w satisfies the following conditions: <w<200mm。

[0018] Preferably, when the outer radius of the measured circular tube is R, the major axis a of the ellipse of the compression mold is selected to satisfy R≤a≤1.2R, and the minor axis b of the ellipse satisfies:

[0019] The method for testing the plate using the above compression performance testing device is as follows:

[0020] (1) Select a compression mold of appropriate specifications, where the major axis of the ellipse of the compression mold is a, the minor axis is b, and the width is W;

[0021] (2) A bending die of corresponding size is selected, wherein the bending die comprises a lower die and an upper die. The major axis of the elliptical part of the lower die is a, the minor axis is b, the length of the straight section at the bottom is c, and a tangent line is made at the vertex of the minor axis of the ellipse, with a length of d; the upper die matches the lower die, and the dimensional parameters are: at, bt, c, d, t is the thickness of the plate to be measured; the length of the straight section c satisfies:

[0022]

[0023] (3) Sample the plate with a width of w, w≤W, and a length of L, satisfying:

[0024]

[0025] The two long sides of the sampling plate are polished and flat, and placed in the middle of the lower die of the pressing die. The upper die is pressed down to press the flat plate into a U-shaped plate, and the part above the elliptical minor axis of the U-shaped plate is cut off;

[0026] (4) The upper die of the test device is pressed down without load, and the friction force of the compression device itself is measured as F0;

[0027] (5) polishing the outer surface of the U-shaped plate pressed in step (3), applying a lubricating medium, placing it between the upper die and the lower die, and adjusting the position of the upper die so that the molding surface fits the outer surface of the test plate;

[0028] (6) The test begins. The upper die starts to move downward, and the pressure F and vertical compressive strain ε are collected at the same time. y , then the true strain is ε=ln(1+ε y ), the true stress is σ=(F-F0) / (wt(1-ε y )), the two correspond to obtain the true stress-strain curve.

[0029] Preferably, the material of the sample to be tested includes metal and non-metal.

[0030] The beneficial effects of the present invention are:

[0031] The present invention adopts the currently common universal testing machine for testing, and the equipment is mature and stable; the testing device is simple and easy to operate, low in cost and good in versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 This is a three-dimensional schematic diagram of the testing device of Example 2 of the present invention.

[0034] Figure 2 It is a schematic longitudinal section diagram of the initial state of the testing device of Example 2 of the present invention.

[0035] Figure 3 This is a schematic longitudinal section diagram of the test device of Example 2 of the present invention at the start of testing.

[0036] Figure 4 This is a schematic longitudinal section diagram of the test device in Example 2 of the present invention at the end of the test state.

[0037] Figure 5 This is a schematic diagram of the structure of the pressing mold required for the plate testing of the testing device of Example 3 of the present invention.

[0038] Figure 6 This is the compression test result of the pipe in Example 2 of the present invention.

[0039] Figure 7 This is the compression test result of the plate material of Example 3 of the present invention.

[0040] In the figure, 1-lower pressing die, 2-upper pressing die, 3-guiding and positioning mechanism, 4-force sensor, 5-sample to be tested, 6-lower pressing die, 7-upper pressing die. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0042] Example 1

[0043] A plate and pipe compression performance testing device comprises a compression die and a strain sensor; the compression die comprises an upper die 1 and a lower die 2 which are opposite to each other; the profile of the upper die 2 is a concave 1 / 4 elliptical cylinder, and a stopper is provided along the upper edge line of the concave elliptical cylinder; the profile of the lower die 1 comprises a concave 1 / 4 elliptical cylinder and a vertical surface located above the elliptical cylinder, and a stopper is provided along the lower edge line of the concave elliptical cylinder; the upper die 2 and the lower die 1 are connected by a guiding and positioning mechanism 3, and the upper die 2 can slide relative to the lower die 1; the upper die 2 is provided with a force sensor 4; and the strain sensor is a non-contact DIC strain measurement system.

[0044] Example 2

[0045] Using the test device of Example 1, a compression performance test was performed on a pipe made of 22MnB5 (original state), with a pipe diameter of 53 mm and a wall thickness of 1.5. The test process is as follows:

[0046] (1) Cut the pipe, take a semicircular pipe with a width of 20 mm after cutting, polish the outer surface, and apply grease; spray the inner surface with speckle. The length of the test device is 100 mm, and the elliptical surface parameters of the upper die and the lower die are a = 26.5 mm, b = 22 mm.

[0047] (2) Clamp the test device on the universal testing machine and press it down three times. Take the average of the device’s own friction force F0 = 630N.

[0048] (3) Place the test sample 5 into the compression mold, adjust the position of the upper compression mold so that the outer surface of the test sample fits the mold surface, and record F1 = 3978.4N at this time.

[0049] (4) Calibrate the DIC speckle measurement system and connect it to the testing machine. Set the testing machine to compression mode and select a loading rate of 1 mm / min.

[0050] (5) Start the compression test, stop the test after the mold is closed, and export the data.

[0051] Figure 6 is the true stress-strain curve obtained after processing.

[0052] Example 3

[0053] Using the test device of Example 1, a compression performance test was performed on a plate made of DP780 with a wall thickness of 1.5. The test process is as follows:

[0054] (1) Sampling: the sampling rectangle is 20 mm wide and 100 mm long.

[0055] (2) The dimensions of the pressing die used are a = 26.5, b = 22 mm, and c = 7 mm. The rectangular plate is pressed into a U-shaped plate, and the portion larger than 26.5 mm is cut off with the bottom of the U-shaped plate as the origin; the outer surface is polished and greased, and the inner surface is sprayed with speckle.

[0056] (3) The length of the test device is 100 mm, and the elliptical surface parameters of the upper die and the lower die are a=26.5 mm, b=22 mm, and c=7 mm.

[0057] (4) The test device is clamped on a universal testing machine and pressed down three times. The average friction force of the device itself is F0 = 595N.

[0058] (5) Place the test sample 5 into the compression mold, adjust the position of the upper mold so that the outer surface of the test sample fits the mold surface; calibrate the DIC speckle measurement system and connect it to the testing machine, set the testing machine to compression mode, and select a loading rate of 1 mm / min.

[0059] (6) Start the compression test, stop the test after the mold is closed, and export the data.

[0060] Figure 7 is the true stress-strain curve obtained after processing.

[0061] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection described in the claims.

Claims

1. A testing method using a compression performance testing device, characterized in that: The sample to be tested is a pipe or a plate; The test methods for pipes are as follows: (1) Select a test device of appropriate specifications, where the width of the upper die and the lower die is W; (2) Cut a section of round tube with a length of w, w≤W, cut it along the diameter of the tube, take a section of semicircular tube, polish the outer surface, and apply lubricating medium; (3) Press the upper die of the test device downward without load, and measure the friction force of the compression device itself as F0; (4) Place the semicircular tube between the upper die and the lower die. Move the upper die downward until the outer surface of the semicircular tube is completely fitted with the die to form a U-shaped plate. The pressure at this time is recorded as F1. (5) The test begins. The upper pressure block continues to move downward, and the pressure F and vertical compressive strain ε are collected at the same time. y , the true strain is ε=ln(1+ε y ), the true stress is σ=(F-F1) / (wt(1-ε y )), the two correspond to obtain the true stress-strain curve, where t is the thickness of the pipe; The test method of the board is as follows: (1) Select a compression mold of appropriate specifications, where the major axis of the ellipse is a, the minor axis is b, and the width is W; (2) Select a bending die of corresponding size, the bending die comprises a lower die and an upper die, the long axis of the elliptical part of the lower die is a, the short axis is b, the length of the straight section at the bottom is c, and a tangent is made at the vertex of the elliptical short axis, the length of which is d; the upper die matches the lower die, and the dimensional parameters are: at, bt, c, d, t is the thickness of the plate to be measured; the length of the straight section c satisfies: (3) Sample the plate with a width of w, w≤W and a length of L, satisfying: The two long sides of the sampling plate are polished and flat, and placed in the middle of the lower die of the pressing die. The upper die is pressed down to press the flat plate into a U-shaped plate, and the part above the elliptical minor axis of the U-shaped plate is cut off; (4) Press the upper die of the test device downward without load, and measure the friction force of the compression device itself as F0; (5) Polish the outer surface of the U-shaped plate pressed in step (3), apply a lubricating medium, place it between the upper die and the lower die, and adjust the position of the upper die so that the molding surface fits the outer surface of the test plate; (6) The test starts, the upper die starts to move downward, and the pressure F and vertical compressive strain ε are collected at the same time. y , then the true strain is ε=ln(1+ε y ), the true stress is σ=(F-F0) / (wt(1-ε y )), the two correspond to obtain the true stress-strain curve; The shrinkage performance testing device comprises a compression die and a strain sensor; the compression die comprises an upper die and a lower die opposite to each other; the profile of the upper die is a concave 1 / 4 elliptical cylinder, and a stopper is arranged along the upper edge line of the concave elliptical cylinder; the profile of the lower die comprises a concave 1 / 4 elliptical cylinder and a vertical surface located above the elliptical cylinder, and a stopper is arranged along the lower edge line of the concave elliptical cylinder; the upper die and the lower die are connected by a guide positioning mechanism, and the upper die can slide relative to the lower die; the upper die is provided with a force sensor; The strain sensor is a contact strain gauge or a non-contact strain gauge, and is used to detect the compression performance of the sample to be tested.

2. The testing method according to claim 1, characterized in that: The contact strain gauge uses a strain gauge, which is vertically attached to the middle part of the inner surface of the sample to be tested when in use; the non-contact strain gauge uses a DIC system, and the inner surface of the sample to be tested is sprayed with speckles when in use.

3. The testing method according to claim 1, characterized in that: The length w satisfies the following conditions: 2 <w<200mm。 4. The testing method according to claim 1, characterized in that: The major axis a of the compression mold ellipse satisfies R≤a≤1.2R, and the minor axis b of the ellipse satisfies, , R is the outer radius of the measured circular tube.

5. The testing method according to claim 1, characterized in that: The materials of the samples to be tested include metal and non-metal.

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