JP2006300740A - Material testing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material testing machine capable of applying a load which is approximately matched with a target value of a monitor object amount, on a device under test from the beginning of conducting its test, when controlling of driving a load mechanism for the device under test whose property is unknown and using an amount differing from the monitor object amount as its control object amount. <P>SOLUTION: While applying the load on the device under test W based on a selected control object amount under such a condition that a low-speed ramp wave is used as the target value, a detection value of the monitor object amount is taken in, and a relationship between both values is automatically measured, prior to the test. Then, the target value corresponding to the control object amount during the test is automatically determined based on the measurement results, whereby the load intended for the device under test W can be applied thereon from the beginning of conducting the test. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a material testing machine, and more particularly, to a material testing machine suitable for performing a test for controlling a load mechanism using a detection value different from the detected value as a control amount so that the monitoring target amount matches the target value.

  In fatigue tests, durability tests, and the like, in general, a structure in which a hydraulic cylinder, a pneumatic cylinder, or a direct acting actuator such as an electromagnetic type is used as an actuator of a load mechanism and the actuator is feedback-controlled (for example, Patent Document 1).

That is, for example, one of a pair of gripping tools is attached to a piston rod of a hydraulic cylinder, and the other gripping tool is fixed to a crosshead or the like so as to hold the both ends of the device under test. By driving the hydraulic cylinder, a load is applied to the device under test. Further, the test force acting on the device under test and the stroke of the hydraulic cylinder are detected. Control of a load mechanism such as a hydraulic cylinder feeds back a detection value of an amount selected as a control target amount (control amount) among these test force or displacement detection values to a preset target value waveform. As a result, a load according to the target value waveform is applied to the device under test.
JP 2002-340763 A

  By the way, using the material testing machine as described above, there is a case in which a test different from the control target amount is set as the monitoring target amount and the load mechanism is controlled so that the monitoring target amount matches the target value. .

  That is, for example, as shown in the external view of the main part in FIG. 5, for example, the member Wa is repeatedly displaced in the direction indicated by the arrow in the drawing in order to perform a fatigue test, a durability test, etc. When this is done, the relationship between the displacement and the test force acting on the DUT W is as illustrated in FIG. When such a test is performed such that the upper and lower ultimate target test forces Ft and Fp as shown in the figure are applied to the test object W, the test force does not continuously change with respect to the displacement of the load mechanism. In addition, the load mechanism cannot be controlled using the test force as the control target amount.

  Therefore, conventionally, the displacement target value is such that the upper and lower ultimate target test forces Ft and Fp repeatedly act on the DUT W with the test force as the monitoring target amount while driving and controlling the load mechanism with the control target amount as the displacement. It is set. When the load mechanism is driven and controlled using a displacement that is different from the test force that is the monitoring target amount as the control target amount, a test that acts on the test subject unless the test subject is actually loaded It is unclear what value the force will be. Therefore, conventionally, based on experience, the amplitude of the target value of the control target amount is set so that the monitoring target amount becomes a target value.

  By the way, when performing the above-described test on the DUT having unknown characteristics, the test is performed by appropriately setting the amplitude of the target value of the control target amount. If it is set excessively, an overload is applied to the device under test and the test results are affected. Conversely, if the amplitude of the target value is set too small, the upper and lower limit values of the monitoring target amount will not be reached, and even if correction processing is performed after that, until the test that reaches the upper and lower limit values of the monitoring target amount can be performed There was a problem that it took time.

  The present invention has been made in view of such circumstances, and the test is started when the load mechanism is controlled to be controlled with an amount different from the monitoring target amount for the DUT having unknown characteristics. An object of the present invention is to provide a material testing machine that can apply a load that substantially matches the target amount to be monitored to the DUT from the beginning.

  In order to solve the above problems, a material testing machine according to the present invention includes a load mechanism that applies a load to a device under test, a force detection means that detects a test force acting on the device under test, and a displacement of the load mechanism. A detection value selected as a control target amount is set in advance among a plurality of detection values including a displacement detection unit that performs detection, and at least a test force detection value and a displacement detection value obtained by the force detection unit and the displacement detection unit. In a material testing machine equipped with a control device that controls the load mechanism so as to match the target value, the monitoring target amount is set separately with a detection value that is different from the selected control target amount as the monitoring target amount. In performing a test for controlling the load mechanism so as to coincide with the monitored target amount target value, the load mechanism is selected based on the selected control target amount with a low-speed ramp wave as the target value prior to the test. DUT characteristic measurement means for automatically obtaining the relationship between the monitoring target amount and the control target amount by taking the detected value of the monitoring target amount while applying a load to the DUT while driving and controlling, Further, the present invention is characterized by comprising target value determining means for automatically determining a target value for the control target amount at the time of testing based on the characteristics of the device under test.

  Here, in the present invention, the target value to be monitored is a target value that repeats an upper limit value and a lower limit value, and the device under test characteristic measurement unit drives and controls the load mechanism using the low-speed ramp wave as a target value. Meanwhile, the value of the control target amount when the monitoring target amount reaches the upper limit value and the lower limit value is stored, and the target value determining means calculates the average value and the amplitude value of the target value for the control target from these values. It can be constituted to require (claim 2).

  The present invention automatically measures the characteristics of the DUT prior to the test in the test for controlling the load mechanism based on the control target amount different from the monitoring target amount, and controls the control target amount based on the result. The problem is solved by automatically obtaining the target value.

  That is, in the present invention, prior to the test, the amount to be monitored is loaded while the test object is loaded with the target value as a low-speed ramp wave that does not easily affect the object to be tested, under the selected control object amount. Is detected, and the characteristic of the device under test, that is, for example, the relationship between the displacement as the control target amount and the test force as the monitoring target amount is automatically measured. Based on the measurement result, the target value of the control target amount is automatically obtained so that the monitoring target amount matches the target value set for the monitoring target amount. Even for the device under test, it is possible to perform a test in which the monitoring target amount is almost equal to the target value from the beginning of the test.

  Then, when the monitoring target value is a target value that repeatedly loads the upper limit value and the lower limit value of the monitoring target amount on the DUT, the low-speed ramp wave is targeted as in the invention according to claim 2. By storing the detected value of the control target amount corresponding to the upper limit value and the lower limit value of the monitoring target amount with the load as a value, the average value and the amplitude of the target value of the control target amount can be easily obtained.

  According to the present invention, when performing a test in which the control target amount and the monitoring target amount are different, even if the characteristics of the test object are unknown, the monitoring target targeted for the test object from the beginning of the test A large amount of load can be applied, and a safe and accurate test can always be performed without relying on the intuition of the operator. In addition, since the load with the low-speed ramp wave as the target value is added to the measurement of the characteristics of the DUT, it is only necessary to apply a load of one cycle, and the characteristics can be measured in a short time. The influence on the DUT can be almost ignored.

  In addition, when the target value of the monitoring target amount repeats the upper limit value and the lower limit value, as in the invention according to claim 2, the upper limit value of the monitoring target amount at the time of loading with the low-speed ramp wave as the target value. The target value of the control target amount can be calculated by simple calculation only by storing the value of the control target amount corresponding to the lower limit value.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic diagram showing a mechanical configuration and a block diagram showing a system configuration.

  In the testing machine main body 1, a cross head 13 is supported on a table 11 via a plurality of support columns 12, and a hydraulic cylinder 14 for loading is fixed to the table 11, and a piston rod 14a of the hydraulic cylinder 14 is fixed. A lower gripping tool 15 a is attached to the upper end portion, and an upper gripping tool 15 b is attached to the lower surface of the crosshead 13 via a load cell 16.

  The test object W is subjected to a test in a state where both ends are gripped by the upper and lower gripping tools 15a and 15b. Accordingly, a tensile or compressive load is applied to the device under test W by driving the hydraulic cylinder 14, and the test force acting on the device under test W at that time is detected by the load cell 16 every moment. Further, the displacement of the piston rod 14a of the hydraulic cylinder 14, and hence the displacement of the lower gripping tool 15a, is detected momentarily by a stroke sensor 17 provided at the lower end of the piston rod 14a.

  The hydraulic cylinder 14 is supplied with hydraulic oil from a hydraulic pressure source (not shown) via a servo valve 18. The valve opening of the servo valve 18 is controlled by an operation signal supplied from the control device 2, so that the hydraulic cylinder 14 is driven and controlled by an operation signal from the control device 2.

  The output of the load cell 16 is taken into the control device 2 as a detection output of the test force acting on the test object W, and the output of the stroke sensor 17 is also the same as the displacement detection output of the load mechanism (hydraulic cylinder 14). It is taken into the control device 2. During the test, the control device 2 feeds back the detection output selected as the control target amount among these detection outputs to a preset target value signal, and performs a PID calculation or the like on the deviation to perform servo control. The operation signal is supplied to the valve 18. As a result, the hydraulic cylinder 14 is driven and controlled so that a test force according to the target value signal acts on the device under test W or a displacement according to the target value signal is given.

  A personal computer 3 is connected to the control device 2, and the personal computer 3 inputs a test force detection output by the load cell 16 and a displacement detection output by the stroke sensor 17 via the control device 2, and performs various data processing. In addition, by operating the operation unit 4 such as a keyboard and a mouse and giving a command, the target value of the control target amount is automatically set in performing a test in which the monitoring target amount and the control target amount are different by the following operation. A target value automatic setting program is installed to obtain and set automatically.

  FIG. 2 is a flowchart showing the contents of the program. The example of FIG. 2 shows an example in which the target upper limit value and the target lower limit value of the monitoring target amount are repeatedly applied to the test object W as shown in FIG. 5, and the monitoring target amount is tested. The example which made the displacement of piston 14a the force and the amount to be controlled is shown.

  With the device under test W mounted on the pair of grippers 15a and 15b, the target value automatic setting program is selected by operating the operation unit 4, and the monitoring target amount and the control target amount are set to the test force and the displacement, respectively. When the upper limit target value Ft and the lower limit target value Fp of the monitoring target amount are set, first, the hydraulic cylinder 14 is switched to displacement control. Next, a low-speed ramp wave to the tension or compression side, for example, the tension side is generated as a target value. As a result, the piston rod 14a of the hydraulic cylinder 14 starts to descend from the origin position, and as shown in the graph of FIG. 3, the measured displacement value changes according to the low-speed ramp wave that is the target value. Note that the speed of the low-speed ramp wave is set so that it does not go too much even if the test force stops when it reaches the target value. On the other hand, the test force measurement value changes from the time when the displacement becomes large to some extent. During this time, it is determined every moment whether or not the test force measurement value that is the monitoring target amount has reached the target upper limit value Ft, and at that time, the displacement measurement value Dt that is the control target amount at that time is stored, and the hydraulic pressure The piston rod 14a of the cylinder 14 is returned to the origin position.

  Next, a low-speed ramp wave toward the compression side is generated as a target value. As a result, the piston rod 14a starts to rise from the origin position, and as shown in the graph of FIG. 3, when the displacement measurement value changes according to the low-speed ramp wave which is the target value, and the displacement becomes large to some extent, the test force The measured value starts to change. When the test force measurement value eventually reaches the target lower limit value Fp, the displacement measurement value Dp at that time is stored, and the piston rod 14a is returned to the origin.

  Next, a displacement target value to be generated during an actual test is calculated using the displacement measurement values Dt and Dp stored in the above operation. That is, the average value of the displacement measurement value Dt corresponding to the upper limit target value of the test force and the displacement measurement value Dp corresponding to the lower limit target value is calculated as Da, and the difference Dd between these measurement values Dt and Dp is calculated. To do. The displacement target value is a waveform (for example, a sine wave) having an amplitude of Dd and an average value of Da.

  In the actual test, as shown in FIG. 4, the target value waveform of the amplitude Dd obtained by the above program is generated following the ramp wave that reaches the average value Da of the displacement target value from the origin position. As a result, the target upper limit value Ft and the target lower limit value Fp as shown in the drawing repeatedly act on the device under test W.

  The point to be particularly noted in the above embodiment is that the operator simply sets the monitoring target amount, the upper and lower limit target values, and the control target amount, and gives a command when the test subject W is mounted. This is the point that automatically measures the characteristics of W and determines the target value of the amount to be controlled based on the result, so that the operator's intuition can be relied upon when testing the test object W whose characteristics are unknown. The intended test can be performed immediately.

  Here, in the above embodiment, a displacement target value of the amplitude Dd obtained by applying a preliminary load to the test object W and measuring its characteristics is immediately generated. When only a load smaller than the upper / lower limit target value of the monitoring target amount can be applied in the characteristic measurement operation, a load of a specified ratio is applied to the upper / lower limit target, and the target value of the control target amount corresponding to that load is calculated. A method of starting the test and gradually increasing the target value of the control target amount so that the monitoring target amount reaches the original upper and lower limit target values may be employed.

  In the above embodiment, an example in which a target value such as a sine wave is generated has been shown. However, an arbitrary repetitive waveform may be generated according to the test purpose, and a target value such as a program wave may be generated. Of course, the present invention can also be applied to the case of generating

In the configuration diagram of the embodiment of the present invention, a schematic diagram showing a mechanical configuration and a block diagram showing a system configuration are shown together. It is a flowchart showing the content of the target value automatic setting program in embodiment of this invention. 4 is a graph showing an example of a displacement applied to a load mechanism during a characteristic measurement operation of a device under test in a target value automatic setting program according to an embodiment of the present invention, and a test force acting on the device under test. It is a graph which shows the example of the test force which acts on the to-be-tested object and the displacement given to a load mechanism at the time of the actual test in embodiment of this invention, respectively. It is a principal part external view of the example of the to-be-tested object which needs to select the control object quantity different from the monitoring object quantity. 6 is a graph showing a relationship between a displacement detection value and a test force detection value when a displacement is repeatedly applied to the test object shown in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test machine main body 11 Table 12 Support | pillar 13 Cross head 14 Hydraulic cylinder 14a Piston rod 15a, 15b Grasp 16 Load cell 17 Stroke sensor 18 Servo valve 2 Personal computer 3 Operation part W Test object

Claims (2)

A load mechanism for applying a load to the device under test; a force detection means for detecting a test force acting on the device under test; a displacement detection means for detecting a displacement of the load mechanism; and at least these force detection means and displacement detection means A control device for controlling the load mechanism so that a detection value selected as a control target amount among a plurality of detection values including a test force detection value and a displacement detection value according to accords with a preset target value In the equipped material testing machine,
When performing a test to control the load mechanism so that the detected value of the amount different from the selected control target amount is the monitoring target amount and the monitoring target amount matches the separately set monitoring target amount target value Prior to this, the low-speed ramp wave is used as a target value, and the load mechanism is driven and controlled based on the selected control target amount to apply a load to the device under test, and the detected value of the monitoring target amount is taken in and monitored. A device characteristic measuring means for automatically determining the relationship between the target amount and the control target amount, and a target for automatically determining a target value for the control target amount at the time of testing based on the determined device characteristic A material testing machine comprising a value determining means.   The monitoring target value is a target value that repeats an upper limit value and a lower limit value, and the DUT characteristic measurement means drives and controls the load mechanism using the low-speed ramp wave as a target value, while the monitoring target amount is the upper limit value. The value of the control target amount at the time of reaching the value and the lower limit value is stored, and the target value determining means obtains an average value and an amplitude value of the target value with respect to the control target amount from these stored values. The material testing machine according to claim 1.

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