JPS62121334A - Elongation measuring instrument for test piece of material fatigue testing machine - Google Patents

Abstract

PURPOSE:To measure with the high accuracy the elongation by a high cycle, by correcting the measured value of a piston stroke by the elongation of a machine body derived in advance at the time of measuring the elongation of a test piece for executing a fatigue test by giving a repeated load at high speed. CONSTITUTION:On the machine body 1, a support 1b is provided, and a crosshead 1d is attached. Also, on the crosshead 1d, a load cell 6 and a chuck tool 5a are provided, and the test piece T is held by the chuck tool 5a and a chuck tool 5b. Also, a piston stroke detector 9 is provided under the chuck tool 5b, and by giving a repeated load, the elongation is measured by the load cell 6 and the detector 9. Moreover, an elongation of the machine body 1 is derived in advance by attaching a dummy test piece T in advance. Subsequently, the elongation measured by the normal test piece T is corrected by the elongation of the machine body 1. Accordingly, since the elongation measured by giving the repeated load is corrected by the elongation of the machine body, therefore, the elongation of the test piece of the material fatigue test can be derived exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION 2;-5-1 \ri The present invention relates to a test piece elongation measuring device for a material fatigue testing machine that performs high-speed cyclic loading.

Law j do■ This type of material fatigue testing machine is shown in Figure 2.

In this figure, a crosshead 1d is provided on a pair of left and right columns 1b, 1b provided on a pedestal 1a of a fuselage 1 so as to be able to move up and down. Further, a winding drum 2 is provided at the measuring section of the pedestal 1a, and the wire rope 3 let out from the winding drum 2 passes through the yoke 1c for connecting between the columns.
The center part of the crosshead 1d is suspended. An upper test piece gripper 5a is supported at the lower center of the crosshead 1d via a load cell 6, and a lower test piece gripper 5b is attached to a piston rod 7a of an actuator 7 provided on a pedestal 1a. .

In such a testing machine, when performing an elongation test on the test piece T, an extensometer 30 using a strain gauge or the like is attached between the test piece T or both grips 5a and 5b.

However, in the above testing machine, the cycle of repeated loading is fl
At high cycles of 10llz or more, the extensometer 30 resonates and cannot accurately measure the elongation of the test piece T.

In addition, as shown by the imaginary line in FIG. 2, when a water tank 31 is attached and a material test is performed in a liquid such as water in the water tank 31, the resistance of the liquid to the extensometer 30 is large. It could only be measured at low cycles. Furthermore, when a gas container is attached in place of the water tank 31 and an elongation test is performed in a corrosive gas, there is a problem in that the extensometer 31 is damaged by the corrosive gas.

The present invention has been made in view of these circumstances, and is a material fatigue testing machine that can measure elongation of a test piece under various conditions such as liquids and corrosive gases, and is capable of measuring elongation at high cycles without being affected by these conditions. The purpose is to provide equipment.

To achieve the above object, the present invention provides a piston stroke detector that detects the piston stroke of an actuator, a load cell that measures repeated loads, and a multiplier that measures the elongation of the aircraft body. Its gist is that it is equipped with a subtractor for determining the elongation of the test piece.

First, the elongation of the airframe is determined by multiplying the pre-measured compliance of the airframe by the load measured by the load cell using a multiplier.

Next, the elongation of the test piece is obtained by subtracting the elongation of the fuselage obtained by the multiplier from the piston stroke measured by the piston stroke detector using a subtracter.

J and FIG. 1(a) are schematic front views of a material fatigue testing machine according to an embodiment of the present invention.

In this figure, the fuselage 1 consists of a pedestal 1a, a pair of left and right columns 1b erected thereon, a yoke 1c directly connected between the upper ends of both support columns 1b and 1b, and a yoke 1c between both support columns 1b and 1b. It is composed of a crosshead 1d that is attached so that it can be raised and lowered. A winding drum 2 is provided on the side of the frame 1a, and the wire row 13 unwound from the winding drum 2 is
It passes through the yoke 1c and suspends the center portion of the crosshead 1d. The height position of the cross head 1d is adjusted by letting out and winding up the wire rope 3, and after the adjustment, the poles h of the clamps provided at both ends of the cross head 1d are adjusted.
ie, le are tightened. Of the pair of upper and lower test specimen grips 5a and 5b, the upper grip 5a was supported at the center of the crosshead 1d via the load cell 6, and the lower grip 5b was vertically attached to the pedestal 1a. It is supported concentrically by the piston port 2 and door a of the actuator 7. A piston stroke detector 9 consisting of an actuating transformer or the like is provided at the lower end of the actuator tough to detect the piston stroke.

FIG. 1 (bl is a block diagram of a test piece elongation measuring device).

In this figure, 10 is a multiplier, to which the output of the load cell 6 is connected via a load amplifier 11. 1
2 is a subtracter, to which the output of the multiplier 10 is directly connected, and the output of the stroke detector 9 is connected via a stroke amplifier 13. 14 is a load indicator to which the output of the load amplifier 11 is connected; 15 is an extension indicator to which the output of the subtractor 12 is connected; and 16 is a piston stroke indicator to which the output of the stroke amplifier 13 is connected.

Next, a method for measuring specimen elongation will be described.

During the test, a strong dummy test piece T is attached between both grips 5a and 5b, and the dimension between both grips 5a and 5b is measured using a dial gauge or the like. Next, the piston rod 7a of the actuator tough is gently driven downward, that is, a constant tensile load is gently applied to the test piece. Next, the elongation of the body 1 is determined by subtracting the dimension between the grips 5a and 5b before tension from the dimension between the grips 5a and 5b after tension. Then, with the growth of aircraft 1 obtained in this way,
The compliance (reciprocal of the spring constant) of the airframe 1 is determined from the spring constant obtained by dividing the applied load.

During a regular material test, first the upper and lower grips 5a,
A regular test piece T is attached between the test pieces 5b, and then the piston rod 7a of the actuator tough is driven to apply repeated loads in the vertical direction to the test piece T at high cycles. In this case, the following actions take place.

■ The piston stroke of the actuator tough is detected by the piston stroke detector 9, and the load cell 6
The above-mentioned repeated load is measured.

(2) The compliance of the machine body 1 measured in advance is multiplied by the load measured by the load cell 6 in a multiplier 10, and the elongation of the machine body 1 is determined.

(2) The elongation of the specimen T is obtained by subtracting the elongation of the adult specimen 1 obtained by the multiplier 10 from the piston stroke measured by the piston stroke detector 9 using the subtractor 12.

According to the test piece elongation measurement device of the material fatigue testing machine of the present invention, the test piece elongation is determined based on the piston stroke of the actuator that applies repeated loads and the repeated loads detected by the load cell. or corrosive gas, etc.
Test piece elongation at high cycles can be measured under various conditions without being influenced by them.

[Brief explanation of drawings]

FIG. 1(a) is a schematic front view of a material fatigue testing machine according to an embodiment of the present invention, FIG. 1(b) is a block diagram of a test piece elongation measuring device, and FIG. 2 is a conventional material fatigue testing machine. FIG. DESCRIPTION OF SYMBOLS 1... Aircraft, 6... Load cell, 7... Actuator, 7a... Piston rond, 9... Piston stroke detector, 10... Multiplier, 12... Subtractor, T. ··Test pieces. Patent applicant Shimadzu Corporation Representative Patent attorney Takaharu Ohnishi Figure 1 (b) Figure 2

Claims (1)

[Claims] (1) A piston stroke detector that detects the piston stroke of the actuator that repeatedly applies a load to the test piece, a load cell that measures the load, and a device that multiplies the compliance of the machine body measured in advance by the load measured by the load cell. The present invention is characterized by comprising a multiplier for calculating the elongation of the fuselage, and a subtracter for calculating the elongation of the test piece by subtracting the elongation of the fuselage obtained by the multiplier from the piston stroke measured by the stroke detector. Test piece elongation measuring device for material fatigue testing machine.