JP2018040662A - Material testing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material testing machine capable of efficiently executing a test for strain aging and easily obtaining a display showing the test result. SOLUTION: A first test force applying step of applying a first test force at which the test piece exceeds the yield point to the test piece, a test force releasing step of releasing the test force for the test piece, and a test piece On the other hand, the control unit 50 that sequentially executes the second test force applying step of applying the second test force that exceeds the yield point after strain aging of the test piece, the first test force applying step, the test force releasing step, and The storage unit 52 that stores the relationship between the test force applied to the test piece and the displacement of the test piece in the second test force application step, and the test force applied to the test piece stored in the storage unit 52 and the test piece An image processing unit 53 that causes the display unit 51 to display a graph showing the relationship with the displacement. [Selection diagram]

Description

  The present invention relates to a material testing machine that performs a strain aging test by applying a test force to a test piece.

  After giving a plastic deformation exceeding the yield point by applying a load to the test piece, removing the load, performing low temperature annealing, or leaving it for a certain period of time and then applying a load again, the yield point is again It is known that a phenomenon called strain aging occurs.

  FIG. 8 is a graph for explaining the strain aging. In the graph shown in FIG. 8, the horizontal axis represents the displacement strain generated in the test piece, and the vertical axis represents the stress applied to the test piece.

  As shown in FIG. 8A, when a load is applied to a test piece that has undergone plastic deformation beyond the yield point Y1 by applying a load, the yield point appears when the load is applied immediately. Absent. On the other hand, as shown in FIG. 8B, the test piece that has undergone plastic deformation beyond the yield point Y1 by applying a load is subjected to low-temperature annealing after removing the load, or constant. If the load is applied again after being left for a period of time, the yield point Y2 occurs again. This is a phenomenon called strain aging.

  Patent Document 1 discloses that the embrittlement state of a duplex stainless steel member is nondestructive by utilizing the fact that, when thermal aging is applied to a duplex stainless steel, it becomes brittle and changes the Charpy impact value at room temperature. Discloses a method for estimating the thermal aging embrittlement of a duplex stainless steel that can be accurately estimated.

Japanese Patent No. 2744704

  In order to perform such a strain aging test, in a conventional material testing machine, hold both ends of the test piece with a gripping tool until the test piece exceeds the yield point with respect to the test piece. After applying the test force and performing the first test, load the test force once, remove the test piece from the gripper, perform low-temperature annealing etc. on the test piece, and then attach both ends of the test piece. The operator manually performed the operation of holding the grip by the gripper and executing a second test in which a test force was applied to the test piece until the test piece broke. For this reason, the strain aging test has been complicated.

  Moreover, in the conventional material testing machine, after applying the test force to the test piece until the test piece exceeds the yield point, the material test is handled as having been completed once the test force is unloaded. Therefore, the measurement data cannot be shared as a series in the first test and the second test described above, and it is necessary to perform comparison of the data using another application. It was.

  The present invention has been made to solve the above-described problems, and is a material testing machine capable of efficiently executing a test for strain aging and easily obtaining a display showing the test result. The purpose is to provide.

  The invention according to claim 1 is a material testing machine for performing a strain aging test by applying a test force to a test piece, wherein the test piece exceeds the yield point of the first test piece. A first test force applying step for applying a test force; a test force releasing step for releasing a test force for the test piece; and a second test in which the test piece exceeds a yield point after strain aging with respect to the test piece. A control unit for sequentially executing a second test force applying step for applying force, and a test force applied to the test piece and the test piece in the first test force applying step and the second test force applying step. A storage unit that stores the relationship between the displacement of the test piece and an image processing unit that displays on the display unit a display that indicates the relationship between the test force stored in the storage unit and the displacement of the test piece And.

  According to a second aspect of the present invention, in the material testing machine according to the first aspect, the image processing unit includes a test force applied to the test piece and a displacement of the test piece in the first test force applying step. Is displayed as a first graph, and the relationship between the test force applied to the test piece and the displacement of the test piece in the second test force applying step is displayed as a second graph.

  According to a third aspect of the present invention, in the material testing machine according to the second aspect, the image processing unit displays the first graph and the second graph in a superimposed manner.

  According to a fourth aspect of the present invention, in the material testing machine according to the third aspect, the image processing unit superimposes the first graph and the second graph in a state where their elongation origins coincide with each other. Display together.

  According to the first aspect of the present invention, after the first test force application step, the test force release step, and the second test force application step are sequentially performed, the test force applied to the test piece and the test piece It is possible to display a display showing the relationship with the displacement on the display unit. For this reason, the test about strain aging can be performed efficiently.

  According to the second aspect of the present invention, the relationship between the test force applied to the test piece and the displacement of the test piece can be displayed in association as the first and second graphs.

  According to the third aspect of the present invention, it is possible to easily compare the test results by displaying the first graph and the second graph in an overlapping manner.

  According to the invention described in claim 4, the first graph and the second graph are displayed so as to overlap each other in a state where the elongation origins coincide with each other, thereby easily comparing the test results with respect to the elongation origin. Is possible.

1 is a schematic diagram of a material testing machine according to the present invention. It is a block diagram which shows the control system of the material testing machine which concerns on this invention. It is a flowchart which shows the test process which performs the test of a strain aging with the material testing machine which concerns on this invention. It is a graph which shows the relationship between the test force and time in a 1st test force provision process. It is a graph which shows the relationship between the test force and time in a 2nd test force provision process. 5 is a graph showing the relationship between the test force applied to the test piece 100 displayed on the display unit 51 and time. 5 is a graph showing the relationship between the test force applied to the test piece 100 displayed on the display unit 51 and time. It is a graph for demonstrating strain aging.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a material testing machine according to the present invention.

  This material testing machine is provided with a pair of left and right screw rods 12 erected so as to be rotatable between a base 11 and a cross yoke 15. The screw rod 12 is composed of a ball screw. The material testing machine also includes a crosshead 14. In the vicinity of both ends of the cross head 14, a ball screw nut 13 to be screwed with the screw rod 12 is incorporated.

  The material testing machine also includes a servo motor 23 and an encoder 24 that acquires rotation information of the servo motor 23. The rotational force of the servo motor 23 is transmitted to the rotary shaft 26 via the synchronous pulley 25, the synchronous belt 28, and the synchronous pulley 27 disposed on the rotary shaft of the servo motor 23. A gear box 21 having a plurality of gears is disposed at both ends of the rotating shaft 26, and the rotating force of the rotating shaft 26 is converted into the rotating force of the pair of screw rods 12, and the pair of screw rods 12 are synchronized. Rotate. Then, the cross head 14 moves up and down by the pair of screw rods 12 rotating synchronously.

  An upper grip 31 is supported on the cross head 14 via the load cell 16. Further, a lower grip 32 is supported on the base 11. The test piece 100 is gripped at both ends by the upper gripping tool 31 and the lower gripping tool 32. In this state, when the cross head 14 is raised, a tensile test force is applied to the test piece 100, and a tensile test as a material test is executed. The displacement generated in the test piece 100 at this time is measured by the displacement meter 18. Note that the compression test can be performed on the test piece by changing the upper gripper 31 and the lower gripper 32 to a platen or the like.

  FIG. 2 is a block diagram showing a control system of the material testing machine according to the present invention.

  This material testing machine stores a CPU as a processor for executing logical operations, a RAM in which data and the like are temporarily stored during control, a ROM in which operation programs necessary for controlling the apparatus are stored, and various data A control unit 50 having a hard disk or the like and controlling the entire apparatus is provided. The control unit 50 is connected to the load cell 16, the displacement meter 18, the encoder 24, and the servo motor 23 described above. The control unit 50 includes a liquid crystal display panel and the like, and is connected to a display unit 51 that performs various displays. As will be described later, the control unit 50 stores a relationship between the test force applied to the test piece 100 and the displacement of the test piece 100, and the test force applied to the test piece 100 and the test piece 100. An image processing unit 53 that causes the display unit 51 to display a display showing a relationship with the displacement of the image.

  Next, a test process for performing a strain aging test using the material testing machine according to the present invention will be described. FIG. 3 is a flowchart showing a test process for performing a strain aging test by the material testing machine according to the present invention.

  When a strain aging test is performed, first, the test piece 100 is mounted on the upper gripping tool 31 and the lower gripping tool 32, and then the test piece 100 is controlled with respect to the test piece 100 by the control of the control unit 50. Executes a first test force application step of applying a first test force exceeding the yield point (step S1). The first test force applied to the test piece 100 in the first test force application step is set in advance as a magnitude at which the test piece 100 is expected to exceed the yield point. The test force at this time is set in advance as, for example, a magnitude at which the strain generated in the test piece 100 becomes 10%. The test force at this time may be set as the magnitude of the test force, or may be set as a ratio to the rating of the material testing machine. Then, when the test force exceeds the set value (step S2), the test force is released under the control of the control unit 50 (step S3).

  Note that it is determined from the relationship between the magnitude of the test force measured by the load cell 16 and the displacement measured by the displacement meter 18 that the test piece 100 has exceeded the yield point, and the test force at the stage beyond the yield point is determined as the first test force. By handling as a test force, it may be determined that the test force applied to the test piece 100 has exceeded the set value, and the test force may be released at this stage.

  FIG. 4 is a graph showing the relationship between test force and time in the first test force application step. In this figure, the vertical axis represents the test force applied to the test piece 100, and the horizontal axis represents the time after the start of the test (the elapsed time since the motor started rotating to move the crosshead 14). ing.

  In the first stage where the test force is applied, there is a region where the test force gradually increases with the passage of time due to the effects of backlash in the gearbox 21 and the gaps between the various parts of the apparatus. As the time passes and the cross head 14 moves, the test force applied to the test piece 100 increases and becomes the upper yield point Y1 of the test piece 100. This upper yield point Y1 is also called initial yield. After the upper yield point Y1 occurs, as shown in FIG. 4, the test force once decreases and then increases again as time passes. When the upper yield point Y1 is exceeded, the test force on the test piece 100 is released. The relationship between the test force applied to the test piece 100 at this time and measured by the load cell 16 and the displacement of the test piece 100 measured by the displacement meter 18 is stored in the storage unit 52 of the control unit 50.

  In addition, the code | symbol P in FIG. 4 shows an elongation origin. This elongation origin is also referred to as a “regression point”, and is an intersection of a linear portion within the elastic modulus measurement range and a displacement axis (horizontal axis indicating displacement strain).

  Next, low temperature annealing is performed with respect to the test piece 100 (step S4). At this time, the operator removes the test piece 100 from the upper gripping tool 31 and the lower gripping tool 32, and performs low-temperature annealing on the test specimen 100. Instead of performing low temperature annealing, the test piece 100 may be left at room temperature for a certain time. Thereafter, the operator attaches the test piece 100 to the upper grip 31 and the lower grip 32.

  Next, under the control of the control unit 50, a second test force application process is performed on the test piece 100, in which the test piece 100 applies a second test force that exceeds the yield point Y2 after strain aging (step). S5). In this embodiment, after the yield point Y2 after strain aging is exceeded in the second test force application step, the test force is applied until the test piece 100 breaks.

  FIG. 5 is a graph showing the relationship between test force and time in the second test force application step. In this figure, the vertical axis represents the test force applied to the test piece 100, and the horizontal axis represents the time after the start of the test (the elapsed time since the motor started rotating to move the crosshead 14). ing.

  As shown in this figure, the test piece 100 that has undergone plastic deformation beyond the upper yield point Y1 by applying a load is subjected to low temperature annealing after being removed, or after being left for a certain period of time, When the load is applied again, the upper yield point Y2 is generated again. This is a phenomenon called strain aging. At this upper yield point Y2, the yield stress increases compared to the initial upper yield point Y1, and the strength of the test piece 100 is increased. Also in this figure, the symbol P indicates the stretch origin.

  When the test force is applied to the test piece 100 even after the upper yield point Y2 is exceeded, the test piece 100 breaks. The control unit 50 detects the breakage of the test piece 100 due to a rapid decrease in the measured value of the test force by the load cell 16 (step S6), and stops the test (step S7). Note that the relationship between the test force applied to the test piece 100 at this time and the displacement of the test piece 100 is stored in the storage unit 52 of the control unit 50.

  Next, the first graph shows the relationship between the test force applied to the test piece 100 and the displacement of the test piece 100 in the first test force applying step by the image processing unit 53 in the control unit 50. And the relationship between the test force applied to the test piece 100 and the displacement of the test piece 100 in the second test force applying step is displayed as a second graph (step S8). At this time, AI (Aging Index / Aging Index) and BH (Bake Hardening / Bake Hardenability) are calculated in the control unit 50, and the calculation result is also displayed on the display unit 51.

  6 and 7 are graphs showing the relationship between the test force displayed on the display unit 51 and time. 4 and 5, the vertical axis indicates the test force applied to the test piece 100, and the horizontal axis indicates the time after the start of the test (the motor is used to move the crosshead 14). Elapsed time since the start of rotation). Here, although the horizontal axis of these graphs is time, this is substantially equivalent to the display of the displacement of the test piece 100, and can be said to be a displacement equivalent amount. The horizontal axis of these graphs may be the displacement of the test piece 100 measured by the displacement meter 18. Further, the elongation amount and strain amount of the test piece 100 used as a display of the final result of the material test are calculated in consideration of the deviation amount of the elongation origin from the displacement of the test piece 100 described above. . The “relation between the test force applied to the test piece and the displacement of the test piece” described in this specification may be any as long as it indicates a relationship between a value corresponding to the test force and a value corresponding to the displacement.

  In the graph shown in FIG. 6, the 1st graph which shows the relationship between the test force and time which were provided to the test piece 100 in the 1st test force provision process, and the test piece 100 was provided in the 2nd test force provision process. A second graph showing the relationship between the test force and time is displayed superimposed. On the other hand, in the graph shown in FIG. 7, the first graph and the second graph are displayed so as to overlap each other in a state where their elongation origins coincide. According to the graph shown in FIG. 6, it is possible to easily compare the test results, and according to the graph shown in FIG. 7, it is possible to easily compare the test results on the basis of the elongation origin.

  As described above, according to the material testing machine described above, after the first test force application step, the test force release step, and the second test force application step are sequentially performed, the test applied to the test piece 100 is performed. Two graphs showing the relationship between the force and the displacement of the test piece can be displayed on the display unit 51. For this reason, when performing a test for strain aging, it is not necessary to perform manual operations as in the past, and it is not necessary to manually process the graph of the test results. It becomes possible to do.

  In the above-described embodiment, the cross head 14 is moved up and down by rotating the pair of screw rods 12 by driving the servo motor 23, and the material test for applying a test force to the test piece 100 by moving up and down the cross head 14. Although the case where the present invention is applied to a machine has been described, the present invention is not limited to such a form. For example, the present invention may be applied to a material testing machine that applies a test force to the test piece 100 by driving a hydraulic cylinder.

11 base 12 screw rod 13 nut 14 cross head 15 cross yoke 16 load cell 18 displacement meter 21 gear box 23 servo motor 24 encoder 31 upper grip 32 lower grip 50 control section 51 display section 52 storage section 53 image processing section P stretch Origin Y1 Upper yield point Y2 Upper yield point

Claims (4)

In a material testing machine that tests strain aging by applying a test force to a test piece,
A first test force applying step in which the test piece gives a first test force exceeding a yield point to the test piece, a test force releasing step in which the test force on the test piece is released, and the test piece A second test force applying step in which the test piece applies a second test force exceeding the yield point after strain aging, and a controller that sequentially executes the second test force applying step,
In the first test force application step and the second test force application step, a storage unit that stores the relationship between the test force applied to the test piece and the displacement of the test piece;
An image processing unit for displaying on the display unit a display indicating a relationship between the test force applied to the test piece stored in the storage unit and the displacement of the test piece;
A material testing machine characterized by comprising: The material testing machine according to claim 1,
The image processing unit displays a relationship between the test force applied to the test piece and the displacement of the test piece in the first test force application step as a first graph, and in the second test force application step. A material testing machine that displays a relationship between a test force applied to the test piece and a displacement of the test piece as a second graph. The material testing machine according to claim 2,
The image processing unit is a material testing machine that displays the first graph and the second graph in an overlapping manner. The material testing machine according to claim 3,
The image processing unit is a material testing machine that displays the first graph and the second graph in a state where the elongation origins coincide with each other.

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