JPH0616006B2 - Material testing machine load-elongation recorder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a recording device for a load-elongation curve of an object to be tested in a material testing machine.

<Prior Art> In a material test, and sometimes a tensile test, the characteristics of the material are generally analyzed from the load-elongation curve of the DUT, but in the analysis, the part until the elongation reaches a predetermined value is particularly important. Becomes Therefore, attach two extensometers with different sensitivities to the DUT, and collect the data from the high-sensitivity extensometer until the elongation reaches the specified value, and the data from the low-sensitivity extensometer if the specified value is exceeded. It has been conventionally practiced to record a load-elongation curve with a plotter based on the data from the load detector.

The recording of the load-elongation curve by the plotter is conventionally executed by the procedure shown in the flowchart of FIG. That is, first, the counter values Pc and Pc ′ of the axes corresponding to the elongation and load of the plotter (hereinafter referred to as the elongation axis and the load axis) are set to 0. Then, every time the elongation and load data Ei and Li are sampled, the position of each axis is moved and plotted. The method is, for example, with respect to elongation, the sampling data Ei and the measurement range full-scale value fs of the extensometer used. , And the value FS at the full scale position of the expansion axis position counter of the plotter, a value of Dc = (Ei / fs) × Fs (1) (hereinafter, referred to as a data count value) is calculated. Then, this Dc is compared with the current value Pc of the stretch axis counter, and the position of the stretch axis is moved by the difference ΔPc. The same applies to the load axis.

<Problems to be Solved by the Invention> When the extensometer is switched from the high-sensitivity one to the low-sensitivity one as described above in the test process in the above conventional recording method, the recording result is shown in FIG. As shown in FIG. 3, the curves may be interrupted and the curves before and after the switching may overlap, which causes a problem of difficulty in reading.

This phenomenon occurs when h is the measurement range full scale value of a high-sensitivity extensometer and l is that of a low-sensitivity extensometer.
Since it is 1, the Dc values obtained by the equation (1) are different for both extensometers. As a result, as shown in Fig. 6, if the elongation is changed to Ev, the plot position of the elongation axis is changed. Is to move from point A to point B.

An object of the present invention is to provide a recording apparatus that can obtain a continuous load-elongation curve even if the extensometer is switched to one having a different sensitivity during the test.

<Means for Solving Problems> The configuration of the present invention will be described based on the basic conceptual diagram shown in FIG.

A plurality of extensometers 1 and 2 having different sensitivities are attached to the test object W. Of these extensometers, the output of one extensometer, which is sequentially selected as the test progresses, and the output of the load detector 3, the extension axis of the plotter 4 and the position of the load axis are set in advance. Based on the output value-plotter axis positional relationship, it is determined by the extension axis position determining means a and the load axis position determining means b, and the load-elongation curve of the test object W is recorded. At the time of switching the extensometer to be used by selection, the setting changing means c determines the position of the elongation axis of the plotter 4 based on the output value of the extensometer used from that time point, that is, the position of the elongation axis at that time point, that is, the time point. The setting of the extension axis position determining means a is changed so as to match the extension axis position based on the output value of the extensometer used up to that point.

<Operation> At the time of switching the extensometer to be used, by automatically resetting the relationship between the extension axis position of the plotter 4 and the output value, a continuous load-elongation curve can be obtained even if the extensometer sensitivity changes. Can be obtained.

<Examples> Examples of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention.

A tensile load is applied to the DUT W while being gripped by the grips 9a and 9b of the material testing machine. A high-sensitivity extensometer 1 and a low-sensitivity extensometer 2 are attached to the device under test W, and the outputs of these are obtained by the amplifiers 11 and 21 of the respective extensometers, the changeover switch 8, and the AD converter 6. It is taken into the control unit 5 via the. Further, the output of the load detection unit 3 is taken into the control unit 5 via the load amplifier 31 and the AD converter 7.

The control unit 5 is composed of a micro computer and has a CPU 5
1, a ROM 52, a RAM 53, an input / output port 54, and the like. The extension and load data from the A / D converters 6 and 7 are taken in, and the plotter 4 for recording a load-elongation curve is described later. A drive command can be given.

Which of the data from the high-sensitivity extensometer 1 and the low-sensitivity extensometer 2 is to be adopted as the elongation data of the load-elongation curve depends on the operation of the changeover switch 8 based on the command from the control unit 5, and the changeover time is set in advance. For example, it is set as the time when the elongation data reaches Ev.

FIG. 3 is a flowchart showing a program written in the ROM 52, and the operation of the embodiment of the present invention will be described with reference to this figure. At the beginning of the test, the data from the high-sensitivity extensometer 1 is used.

First, the extension axis counter value Pc and the load axis counter value Pc ′ of the plotter 4 are set to zero. Then, every time the digital conversion data Ei and Li of elongation and load are sampled, various positions are moved and plotted, but the method of load axis is exactly the same as the conventional method. When the data Ei is collected for the extension axis, the measurement range full scale value of the high-sensitivity extensometer 1 is set to h and the extension axis counter full scale position of the plotter 4 is set to the full scale position until the data Ei reaches the extension point switching point Ev. When the value is FS, the data count value Dc = (Ei / h) × FS (2) is calculated, and the position of the stretch axis is moved by the difference ΔPc between the Dc and the current count value Pc of the stretch axis. . Up to this point, it is the same as the conventional one.

When Ei reaches Ev, the changeover switch 8 is driven, and at the same time, the extension axis counter value Pc is calculated by using the measurement range full scale value 1 of the low sensitivity extensometer 2 as shown in the following equation (3). change.

Pc = (Ev / l) × FS (3) Then, the calculation of the data count value Dc is changed to Dc = (Ei / l) × FS (4) after the switching. Therefore, at the time of Ei = Ev,
From (3) and (4), since Pc = Dc (5), the extension shaft does not move at the time of this switching.

As a result, the obtained load-elongation curve becomes continuous as shown in FIG. In addition, in the load-elongation curve thus obtained, the scale of the elongation axis differs before and after the switching of the extensometer, so the mark indicating this switching point should be automatically attached by the plotter. Is preferred.

In the above embodiments, two extensometers of high sensitivity and low sensitivity are attached, but three or more extensometers with different sensitivities are attached and the extensometers are switched sequentially. It goes without saying that a continuous load-elongation curve can be obtained by similar processing.

<Effect> As described above, according to the present invention, in recording the load-elongation curve by the plotter from the output of one of the extensometers having different sensitivities and the output of the load detector. ,
At the same time as switching the extensometer to be used, the expansion axis position of the plotter is automatically reset so that the position of the expansion axis does not move at the time of switching. It became easier to read.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram showing the configuration of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a flow chart showing a program written in its ROM 52, and FIG. A graph showing an example of the recorded load-elongation curve, FIG. 5 is a flowchart showing a recording procedure of the load-elongation curve in the conventional device, and FIG. 6 is a graph showing an example of the load-elongation curve recorded by the conventional device. Is. 1 ... High-sensitivity extensometer, 2 ... Low-sensitivity extensometer, 3 ... Load detector, 4 ... Plotter, 5 ... Control section, 6, 7 ... AD converter, 8 ... Changeover switch

Claims (1)

[Claims] 1. A plurality of extensometers having different sensitivities are attached to an object to be tested, and the output of a load detector and one of the extensometers selected from the plurality of extensometers sequentially as the test progresses. From the output and the position of the plotter's load-corresponding axis and extension-corresponding axis,
In the device for recording the load-elongation curve of the DUT by determining based on the preset output value-plotter axial positional relationship for each, the elongation used from that time at the time of switching the selection of the extensometer. A means for setting and changing the output value-plotter axis positional relationship for the elongation corresponding axis so that the position of the elongation corresponding axis of the plotter according to the output value at that time of the meter coincides with the position of the elongation corresponding axis at that time. A load-elongation recording device for a material testing machine, characterized by being provided.