CN111157329B

CN111157329B - Low-temperature CTOD testing device and method

Info

Publication number: CN111157329B
Application number: CN202010089011.7A
Authority: CN
Inventors: 沐卫东; 蔡艳; 王博士; 郭伟; 李芳�; 华学明
Original assignee: Shanghai Jiao Tong University
Current assignee: Shanghai Jiao Tong University
Priority date: 2020-02-12
Filing date: 2020-02-12
Publication date: 2021-11-23
Anticipated expiration: 2040-02-12
Also published as: CN111157329A

Abstract

The invention discloses a low-temperature CTOD test device, which is characterized by the centering adjustment during the clamping process of the sample, and can still ensure the centering accuracy when the clamp is thermally expanded and contracted, and specifically includes a vertical correction system and a horizontal centering system. and front and rear centering systems; the vertical correction system includes a base and a pressure roller, the horizontal centering system includes a span plate and an adapter plate, and the front and rear centering system includes a centering adjustment module and a calibration block; the horizontal The centering system is located on the upper edge of the side surface of the base, and the front and rear centering systems are located above the base. The invention also discloses a use method of the low-temperature CTOD test device. The low-temperature CTOD test device and method provided by the invention can effectively ensure the neutrality and span consistency in the test process, improve the stability and consistency of test results; at the same time, it is convenient for low-temperature sample change, improves the continuous low-temperature test efficiency, and saves energy ; This device is suitable for both low temperature and room temperature, and can be widely used.

Description

Low-temperature CTOD testing device and method

Technical Field

The invention relates to the technical field of fatigue fracture research, in particular to a low-temperature CTOD testing device and method.

Background

The CTOD test, one of the commonly used methods for measuring fracture toughness of materials, has high requirements on devices, especially on neutrality during the test. The discreteness of the neutrality on the data test results is greatly influenced. In the low-temperature CTOD test process, a low-temperature environment box is generally used, so that the difficulty in sample changing or centering adjustment in the low-temperature test process is greatly increased, and the test efficiency is also influenced.

At present, the clamps in the CTOD testing process mainly comprise the following parts:

one, in the CTOD test procedure, mostly use traditional three point bending anchor clamps, but when sample thickness direction adjustment centering adjustment sample centering, often stop the range of eyeballing, measure the distance of two end interface distance anchor clamps one side with the ruler, this kind of centering procedure time is very long usually, and efficiency is very low. At room temperature, the method can be used at room temperature, but the method has difficulty and long time in the low-temperature test process, especially in the ultralow-temperature environment, and also has the risk of frostbite.

Although most three-point bending clamps have the designed span-adjustable function, due to the fact that the span fixing device can generate gaps and is relatively loose due to expansion caused by heat and contraction caused by cold of materials in a low-temperature environment, the span can fluctuate in the testing process, and the testing result can be influenced.

And thirdly, due to the difficulty in sample change and centering adjustment at ultralow temperature, most of the existing ultralow temperature CTOD tests cannot well test continuous tests. In many tests, samples are changed only when the samples are restored to be close to room temperature, so that the test efficiency is greatly reduced, and energy is wasted.

Therefore, most of the existing clamps and methods for testing the low-temperature CTOD mostly stay in the traditional methods, and the testing process is complex and inefficient. The low temperature test process does not allow for continuous testing. Symmetry in the test process is difficult to guarantee, and data dispersion is great.

Accordingly, those skilled in the art have endeavored to develop a highly centering, simple and efficient ultra-low temperature CTOD device and test method.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide an apparatus and a method for performing CTOD testing at low temperature with high efficiency.

In order to achieve the aim, the invention provides a low-temperature CTOD testing device which is characterized by comprising a vertical correcting system, a horizontal centering system and a front and back centering system; the vertical correcting system comprises a base and a press roller, wherein the length direction of the base is vertical to the axial direction of the press roller; the horizontal centering system comprises a span plate and an adapter plate, and the span plate is vertical to the length direction of the base; the front and rear centering system comprises a centering adjusting module and a calibration block, and the width direction of the centering adjusting module is vertical to the length direction of the base; the horizontal centering system is positioned on the upper edge of the side surface of the base, and the front and rear centering systems are positioned above the base.

Furthermore, the base center part adopts the design of V type groove, the base surface adopts level and smooth design.

Further, the surface roughness of the press roll and the support roll was 0.8.

Furthermore, the pressure head adopts circular recess design, and pressure head internal surface roughness 0.8 is convenient for fix through fixed spring and compression roller, automatic centering. A total of 6 stainless steel fixation springs are required.

Further, the span plate is of an integrally machined symmetrical structure, and the span of the span plate is constant.

Further, the low-temperature CTOD testing device is made of 9Ni steel.

The invention also provides a use method based on the low-temperature CTOD testing device, which comprises the following steps:

the method comprises the following steps:

(1) assembling: selecting the span plate, the supporting roller and the compression roller according to the style size and standard, and fixing the base and the pressure head on a fatigue machine;

(2) calibration: lifting one side of the horizontal centering adjustment module, then slowly pressing down by using displacement control, and changing into a micro-force control mode when the compression roller is close to the side surface of the V-shaped groove so as to enable the compression roller to be vertical to the clamp;

(3) and (3) testing: and adjusting the centering adjustment module by using the calibration block, and placing a sample for testing.

Further, in the step (2), after the vertical correction system is calibrated, the pressure head is lifted by 100 mm.

Further, in the step (3), the sample adjusts the horizontal centering system and the front and rear centering systems by using the calibration block.

Compared with the prior art, the CTOD test fixture and the method have at least the following beneficial technical effects:

1. the centering performance in the test process is effectively guaranteed, and the consistency of the span is guaranteed.

2. Meanwhile, low-temperature sample changing is facilitated, continuous low-temperature testing is facilitated, the stability of data results is guaranteed, the low-temperature testing efficiency is greatly improved, and energy is saved.

3. The device is suitable for low temperature and room temperature simultaneously, and has wide application range.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a block diagram of an apparatus according to a preferred embodiment of the present invention;

FIG. 2 is a diagram of the base structure of a preferred embodiment of the present invention;

FIG. 3 is a ram block diagram of a preferred embodiment of the present invention;

FIG. 4 is a block diagram of a centering module in accordance with a preferred embodiment of the present invention;

FIG. 5 is a cross-deck block diagram of a preferred embodiment of the present invention;

FIG. 6 is a block diagram of an adapter plate in accordance with a preferred embodiment of the present invention;

FIG. 7 is a comparison of the CTOD test results at low temperature of a conventional device and the present device in accordance with a preferred embodiment of the present invention;

FIG. 8 is a comparison of the CTOD test results at room temperature between a conventional device and the present device in accordance with a preferred embodiment of the present invention;

the test device comprises a base 1, a transfer plate 2, a span plate 3, a centering adjusting module 4, a support roller 5, a press roller 6, a pressure head 7, a test sample 8 and a fixed spring 9.

Detailed Description

The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views. The size and thickness of each component shown in the drawings are arbitrarily illustrated, and the present invention is not limited to the size and thickness of each component. The thickness of the components may be exaggerated where appropriate in the figures to improve clarity.

As shown in FIG. 1, the device comprises a vertical correction system, a horizontal centering system and a front and back centering system. The vertical correction system is characterized in that the vertical correction is automatically performed by designing the base 1 part and combining a micro-force control mode of a machine, so that the axial direction of the compression roller 6 is ensured to be vertical to the length direction of the base 1. The horizontal centering system ensures that the span is unchanged and the centering in the horizontal direction is also ensured by designing the span plate 3 with fixed span. The front and back centering system is characterized in that a single adjusting system is designed, the front and back distance is calculated according to the size of the sample 8, and a fixed baffle is adjusted by utilizing a calibration block and the front and back centering adjusting system. Ensuring that the sample 8 is centered in the front-to-back direction.

In a specific embodiment, the device is used according to the following steps:

(1) firstly, selecting a proper span plate 3, a proper support roller 5 and a proper compression roller 6 according to the size and the standard of a sample 8, respectively fixing the support roller and the compression roller on a base and a pressure head by using a fixed spring 9, and finally assembling a corresponding module. The base 1 and the ram 7 are fixed to the fatigue machine, respectively.

(2) One side of the horizontal centering adjustment module 4 is lifted up, then the horizontal centering adjustment module is slowly pressed down by using displacement control, when the compression roller 6 is close to the side surface of the V-shaped groove, the mode is changed into a micro-force control mode (0.1-0.3KN), and the equipment can automatically correct the compression roller 6 to be vertical to the clamp by using small load pressing. Finally, the ram is raised by about 100 mm. And finally, the horizontal centering adjustment module 4 is put down and fixed.

(3) And the front and back modules and the horizontal centering module are adjusted by the calibration block, so that the test sample 8 can be placed for starting testing. When placing the sample 8, the surface of the sample 8 is only required to be aligned with the side face of the baffle of the front and rear centering adjustment modules 4. The horizontal direction only needs to align the center of the notch with the line marking line in the centering adjustment module 4. The test centering precision and the test efficiency are greatly improved.

As shown in figure 2, the base 1 is a symmetrical joint, a V-shaped groove is designed in the center of the base 1, and the length direction of the V-shaped groove is strictly parallel to the thickness direction of the base 1. This is used for adjusting the verticality, and the supporting roller 5 is contacted with the V-shaped groove by pressing the compression roller 6, so that the alignment between the base 1 and the compression roller 6 is automatically corrected.

As shown in fig. 3, the lower end of the press head is designed with a circular groove, and the circular radius is larger than the diameter of the press roll. The compression roller and the pressure head are connected by using the fixed spring, and the compression roller and the circular groove of the pressure head are automatically centered under the action of the spring.

As shown in fig. 4, the centering adjustment module 4 is also of a symmetrical structure. The front and back centering of the sample 8 can be adjusted by adjusting the front and back movement distance of the two sides of the baffle through a threaded structure. The adjusting mode can eliminate the problem of inconsistent gaps on two sides in the assembling process of the structure. The stainless steel spring is arranged on one side of the screw rod, so that the problem of looseness of the baffle caused by material shrinkage at low temperature can be solved. The centering adjustment module 4 is simple and effective in structure.

As shown in fig. 5, the span plate 3 is easy to process and convenient to replace. The high-precision high-pair-weight span plates 3 can be obtained through wire cutting, the span plates 3 with different specifications can be machined in advance, and the test can be conveniently performed directly. The proper span plate 3 is selected according to the size of the sample 8, and the problem that the span is changed due to expansion with heat and contraction with cold in the process of ultralow temperature test is solved. The span consistency in the ultralow temperature continuous test process is ensured.

As shown in fig. 6, the span plate 3 and the centering adjustment module 4 are assembled on the base 1 via the adapter plate 2. The center lines of the span plate 3 and the adapter plate 2 are provided with marking lines which are strictly aligned when being assembled. Meanwhile, the height of the span plate 3 and the height of the adapter plate 2 are strictly required to be lower than that of the base 1, so that the span plate 3 and the adapter plate 2 are not stressed and are not damaged in the test process. The press roll 6 and the support roll 5 are both cylinders and their dimensions are chosen according to the standard. They are respectively connected with the span plate 3 and the pressure head 7 through springs, thereby ensuring the span and simultaneously ensuring the centering of the press roller 6 and the pressure head 7.

As shown in FIGS. 7 and 8, FIG. 7 shows the results of the CTOD test at a low temperature (-193.5 ℃ C.) using the conventional apparatus and the present apparatus. Fig. 8 is a test result of CTOD at room temperature using the conventional device and the present device. The material of sample 8 is 9Ni steel. The dimensions of sample 8 were 18mm by 82.8mm, using the BS7448 standard. When the device and the method are used for low-temperature testing, the test sample 8 can be continuously clamped and replaced without waiting to the room temperature. When the traditional device is used for low-temperature test, the sample can be changed and clamped only when the temperature is recovered to the room temperature. When testing at room temperature, the sample 8 can be replaced more quickly and conveniently. As can be seen from comparison of the test results of FIG. 6 and FIG. 7, the device and the method have the advantages of high efficiency of low-temperature and room-temperature tests, low dispersion of the test results, and obvious beneficial effects.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. a low-temperature CTOD testing device, is characterized in that, comprises vertical correction system, horizontal alignment system and front and rear alignment system; Described vertical correction system comprises base, pressure head and pressure roller, and the length direction of described base and all The axial direction of the pressing roller is vertical; the horizontal centering system includes a span plate, an adapter plate and a support roller, and the thickness direction and height direction of the span plate are both perpendicular to the length direction of the base; the front and rear The centering system includes a centering adjustment module and a calibration block, the width direction of the centering adjustment module is perpendicular to the length direction of the base; the horizontal centering system is located on the upper edge of the side surface of the base, and the front and rear centering systems are located at the base. above the base;

The base adopts a symmetrical overall structure, and a V-shaped groove is arranged under the middle of the base. The opening angle of the V-shaped groove is 90°, and the distance of the groove opening is greater than the diameter of the pressing roller. The lower part of the V-shaped groove needs to be rounded. ;

The centering adjustment module is a symmetrical structure, including a screw rod, a stainless steel spring and a baffle, and the front and rear distance of the baffle is adjusted by a knob to ensure that the sample is centered in the front and rear directions;

The stainless steel spring is arranged on one side of the screw rod, and the centering adjustment module can be opened on one side.

2. The low-temperature CTOD test device according to claim 1, characterized in that, further comprising a fixed spring, and the pressure roller and the support roller are respectively connected to the pressure head and the span plate by using the fixed spring. connect.

3 . The low-temperature CTOD testing device according to claim 2 , wherein a circular groove is designed in the center of the bottom of the indenter, and the radius of the circular groove is larger than the radius of the pressing roller. 4 .

4. The low-temperature CTOD test device according to claim 1, wherein the span plate is a symmetrical structure processed as a whole, the machining dimension deviation of the span plate is less than 0.05mm, and there is no assembly inside the span plate gap.

5. the using method of low temperature CTOD testing device as claimed in claim 1, is characterized in that, comprises the steps:

(1) Assembly: According to the size and standard of the sample, select the span plate, the support roller and the pressing roller, and fix the base and the indenter to the fatigue machine;

(2) Calibration: lift one side of the centering adjustment module, and then use the displacement control to slowly press it down. When the pressing roller is close to the side of the V-shaped groove, change to the micro-force control mode, so that the pressing The roller and the fixture are vertical;

(3) Test: Use the calibration block to adjust the centering adjustment module, and place the sample for testing.

6 . The method of using a low-temperature CTOD test device according to claim 5 , wherein in the step (2), the vertical correction system is calibrated and then the indenter is raised by 100 mm. 7 .

7 . The method for using a low-temperature CTOD testing device according to claim 5 , wherein in the step (3), the calibration block is used to adjust the leveling system and the horizontal alignment system before placing the sample. 8 . Front and rear centering system.