JPS61219850A - Method for measuring elongation strain - Google Patents

Abstract

PURPOSE:To calculate an elongation strain value excellently even if elongation exceeding a measuring range is generated, by performing the elongation of a test piece by a second elongation detecting means having a large measuring range when the elongation exceeding the measuring range of an elongation detecting apparatus was generated. CONSTITUTION:When tensile load is applied to a test piece 7, said test piece 7 begins to elongate, and the detected result of elongation by an extensiometer 10 and the change in the distance between both grasping jig 3, 5 as the movement amount of a crosshead 2 are respectively supplied to a data processor 15 as electric signals and processed therein to be outputted to a recorder 17. In this case, the calculation of elongation strain is performed on the basis of the extensiometer 10 in the measuring range of said extensiometer 10. In the range exceeding the measuring range of the extensiometer 10, the calculation of elongation strain is performed on the basis of the data of the movement amount of the crosshead 2 showing the change in the distance between both grasping jigs 3, 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for measuring elongation strain in material testing.

(Prior Art) The elongation of a test piece in a tensile test is often measured by attaching an elongation detection device to the test piece.

The elongation strain value of the test piece is determined by the data processing device for the material testing machine from the elongation value detected by the elongation detection device and the test length of the detection device.

(Problems to be Solved by the Invention) However, in the conventional method described above, when elongation exceeds the measurement range of the elongation detection device, data processing cannot be performed and elongation measurement becomes impossible. There was a point.

(Means for Solving the Problems) The present invention solves the above problems by providing, in addition to the conventional elongation detection device, a second detection means capable of detecting elongation over a larger measurement range. It is something to be solved.

That is, the elongation strain measurement method according to the present invention includes an elongation detection device that detects elongation in a predetermined test length, and a second detection means that can detect elongation in a larger elongation measurement range than the detection device. The elongation detection device is installed in parallel, and within this measurement range, the elongation strain is determined from the elongation detected by the detection device and its test length. However, when elongation exceeds the measurement range of the detection device, the second It is characterized by determining the elongation strain from the elongation detected by the detection means and the test length.

(Function) In a range where the elongation is not very large, the elongation detection device performs highly accurate elongation detection, and when measuring in a large elongation range that exceeds the measurement range of the elongation detection device, a second elongation detection device with a large measurement range is used. Do it by means.

(Example) Figure 1 shows an example of the present invention.Material test! Upper grip 3 attached to the crosshead 2 of 11.1 and lower grip 5 attached to the table 4
The test piece 7 is held in a vertical position. At the upper and lower gauge points A and H provided in the middle of the test piece 7, there are elongation detection devices (hereinafter referred to as "extensometers") 10 are the upper and lower arms l.
It is attached by oa, 10b. Extensometer 10
For example, a differential transformer extensometer or a known strain gauge extensometer can be used.

There is a load detector (load cell) on the top of Crossherad 2.
11 is attached. The load cell 11 is electrically connected to a load amplifier 13 , and the extensometer 10 is electrically connected to an elongation amplifier 14 , and the load amplifier 13 and elongation amplifier 14 are connected to a data processing device 15 . The position and amount of movement of the cross head 2 detected by the cross head movement detection device 1B are similarly input to the data processing device 15 through the cable 16. The crosshead movement detection device 18 serves as a second detection means for detecting a change in the distance between both grips 3.5. Test length L+ of extensometer 10 and both upper and lower grips 3.
5 (second test length) and the measurement range of the extensometer 10 are registered in advance in the data processing device N15.

When a tensile load is applied to the test piece 7 in this state.

Test piece 7 begins to stretch. The elongation detection result by the extensometer 10 and the distance change between both grips 3.5 as the amount of movement of the crosshead 2 are each supplied as electric signals to the data processing device 15, and processed by the data processing device 15. and output to the recorder 17 or the like. In this case, in the measurement range of the extensometer 10, elongation strain is calculated based on the data from the extensometer 10.
In a range beyond the measurement range of , the elongation strain is calculated based on data on the amount of movement of the crosshead 2, which accounts for the change in distance between the two grips 3 and 5. That is, this data processing device 15 uses the extensometer 1 registered in advance.
It is equipped with a selection mechanism that selectively switches the data to be adopted with the upper limit of the measurement range of 0 as the boundary. Based on the output from the data processing device 15, the recorder 17 draws a load-elongation curve as shown in FIG. The right side is the range determined by the distance change between the grips 3 and 5. The elongation strain (is the value obtained by dividing the elongation depth by the original test length.) For example, the elongation strain values εm,@n at points m and n in FIG. 2 are determined by the following equation.

J! n εn=--X100(%) (Formula 2)
Instead of providing the recorder 17, for example, a display device for digitally displaying the calculated elongation strain value may be provided.

In this elongation strain measurement method, when the elongation is within a predetermined range, the elongation strain value is obtained using the detection data of an extensometer with high detection accuracy, and when the elongation is large outside the measurement range of the extensometer, Since the elongation strain value is determined using data detected by the second detection means having different sensitivities, it is possible to measure elongation over a wide range at once.

In the above explanation, the crossherad 2 is used as the second detection means for detecting elongation outside the measurement range of the extensometer
However, another extensometer with a different elongation measurement range and test length (that is, with a different sensitivity) may be provided as the second detection means.

(Effects of the Invention) As explained above, the elongation strain measuring method according to the present invention can successfully determine the elongation strain value even when elongation exceeds the measurement range of one extensometer. It turned out to be excellent.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention. FIG. 2 is a graph showing the load-elongation curve. 1... Material testing machine 2... Crosshead 3° 5... Grip 7... Test piece lO... Extensometer 11... Load cell 15... Data processing device patent applicant Co., Ltd. Shimadzu Corporation Representative Patent Attorney Hiroshi Sugawara Figure 1

Claims (1)

[Claims] (1) A method for measuring the elongation strain of a test piece, which includes an elongation detection device that detects elongation at a predetermined test length, and a second elongation detection device that can detect elongation in a larger elongation measurement range than the elongation detection device. The elongation strain is determined from the elongation detected by the elongation detection device and its test length within the measurement range of the elongation detection device, but when elongation exceeds the measurement range of the elongation detection device, . A method for measuring elongation strain, characterized in that the elongation strain is determined from the elongation detected by the second detection means and the test length.