JPH0357902A - Apparatus for measuring apparent strain due to temperature of high temperature strain cauge - Google Patents

Abstract

PURPOSE:To correctly measure the apparent strain while holding a high temperature strain gauge under the same conditions as in the actual use by making a coefficient of linear expansion of a tightening bolt smaller than that of at least a sphere and a block. CONSTITUTION:One surfaces of flange portions 6a, 6b of a high temperature strain gauge G are in pressed contact with the front and rear surfaces of a substrate 12 which is made of a material having a coefficient of linear expansion approximately equal to that of an object 7 to be measured, respectively. Moreover, a retaining plate 13 made of the same material as the substrate 12 butts against the other surface of each flange portion 6a,6b. A sphere 14 made of a material having a large coefficient of linear expansion such as stainless steel presses the flange portions 6a,6b uniformly, and a block 15 made of stainless steel holds the sphere 14 at the bottom surface of a recessed groove 15a. A tightening bolt 16 having a smaller coefficient of linear expansion than the sphere 14 and block 15 is screwed to a nut 17, so that flange portions 6a,6b are pressed between the substrate 12 and retaining plate 13. Accordingly, the bolt 16 expands larger at high temperatures that the sphere 14 and block 15, and the tension by the bolt 16 can be surely maintained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a temperature-dependent apparent strain measurement device for a high-temperature strain gauge, and more specifically, to a device that outputs an electric signal corresponding to the strain when it receives strain. The temperature of the high-temperature strain gauge is such that the detection part is provided with a flange section for fixing to the object to be measured, for example, by spot welding, and the strain occurring in the object to be measured under high temperature is detected via the flange section. This is related to apparent strain measurement equipment. [Prior art] High-temperature strain gauges are used at high temperatures (for example, 100 to 650°C).
It detects the strain (or stress, the same applies hereinafter) that occurs in the object under measurement. Recently, research on high-temperature conditions in high-pressure vessels, gas turbines, rockets, missiles, nuclear reactors, etc. has become active, and the need for high-temperature strain gauges is increasing, as is the demand for improved strain detection accuracy. ing. In order to ensure detection accuracy, it is necessary to take various measures against temperature.

For example, when fixing a high-temperature strain gauge to an object to be measured, it is not possible to use organic adhesives, which deteriorate due to heat and reduce adhesive strength and insulation resistance. An inorganic adhesive is used. However, this inorganic adhesive cannot completely eliminate the influence of temperature. As a high-temperature strain gauge developed to solve these problems with adhesive-type high-temperature strain gauges, a flange is formed around the periphery of the strain detection part, and this flange is fixed to the object to be measured by spot welding. There is something called a welded high temperature strain gauge.

By the way, as factors for the influence of temperature on the detection output of a high temperature strain gauge, apart from the influence of the adhesive, there are mainly the following four factors.

The first factor is the resistance temperature coefficient of the gauge element that detects strain, the second factor is the strain sensitivity (gauge factor) of the gauge element, and the third factor is the linear expansion coefficient of the gauge element.
The fourth factor is the linear expansion coefficient of the object to be measured. And, due to the influence of these factors, high temperature strain gauges
In addition to the strain that occurs in the object to be measured, apparent strain due to temperature is also detected. This apparent distortion is
Even when a high-temperature strain gauge is fixed to an object to be measured and no strain is applied, its resistance value changes due to temperature changes. Therefore, in order to accurately measure the strain that occurs in the object to be measured, it is necessary to know the exact apparent strain. Conventionally, in order to measure this apparent strain, a method has been adopted in which a high-temperature strain gauge is heated in a high-temperature test furnace and the appearance of the high-temperature strain gauge at a predetermined temperature is measured.

One way to measure this apparent strain is to, for example, bundle up about 20 individual high-temperature strain gauges and place them in a high-temperature test furnace without fixing them to the object to be measured.
A method has been adopted in which apparent strain is measured by measuring the output of a high temperature strain gauge at each predetermined temperature.

However, in the case of this measurement method, since the object to be measured is not fixed to the same material as the actual object to be measured, the flange etc. may be deformed during heating, and the apparent strain and However, this method could not be used for strain measurements that require extremely high accuracy.

In addition, as another conventional measurement method, about 20 high-temperature strain gauges are extracted from a lot manufactured at the same time, about 10 of them are heated individually in a high-temperature test furnace, and some of the remaining ones are used to measure the object to be measured. There is also a method in which the specimen is fixed by spot welding on a test piece made of the same material as the object, and the apparent strain is measured by heating at the same time, and this measured value is estimated as the representative value of the apparent strain of other high-temperature strain gauges that were heated at the same time. He had been hired.

However, in the case of this measurement method, the high-temperature strain gauge used for measurement is spot-welded, so it is not practical to remove the high-temperature strain gauge from the test piece and re-weld it on the actual object to be measured. It is extremely difficult or impossible to remove it, and even if it were possible to remove it, there was a problem in that characteristics such as sensitivity and fatigue life would be significantly impaired.

In view of the above points, a strain gauge temperature characteristic measuring device capable of measuring apparent strain due to temperature in a reusable state has been proposed, for example, in Japanese Patent Laid-Open No. 6↓-280505.

FIG. 6 shows a cross-sectional view of the strain gauge temperature characteristic measuring device, and shows a base material 20 made of the same material as the material to be measured.
and a pair of presser plates 21.21 made of the same material as the material to be measured, the base material 20 and the presser plate 21.2.
1 and the flange portions 22 of the two strain gauges 22.22 without pressing the detection portions of the strain gauges 22.22.
a, and tighten the presser plate 21.21 against the base material 20 with at least two through bolts 23.23, so that the pair of strain gauges 22.22 are brought into pressure contact with both the front and back surfaces of the base material 20. ing.

[Problem to be solved by the invention]

In the case of the device described in the above publication, when the entire device is heated to a predetermined temperature (for example, 550° C.), in order for the elongation of the strain gauges 22 and 22 to be the same as the elongation of the base material 20, the strain The product of the friction coefficient of the gauge 22 and the base material 20 and the force pressing them together (i.e., the frictional force) is the strain gauge 2
The force must be equal to or larger than the force for making the elongation of the base material 20 equal to the elongation of the base material 20. At this time, if the tension of the through bolt 23.23 decreases due to the temperature rise,
Strain gauge 22 by base material 20 and presser plate 21.21.
22 is reduced or lost. here,
Factors that reduce the tension of the through bolts 23.23 due to temperature rise include the contact state of the threads of the through bolts 23.23 and the contact state of the through bolts 23, 23 and nuts 24.24 with the holding plates 21, 21. It is thought that applying heat may cause it to become loose. However, no consideration has been given to this point in the past, and no consideration has been given to whether the tensile force of the bolt maintains the necessary tightening force even at high temperatures. Therefore, it was not possible to accurately measure the apparent strain due to temperature using the high-temperature strain gauge. This invention was made to solve the above-mentioned problems, and it is possible to reliably maintain the clamping force of the clamping member at high temperatures. An object of the present invention is to provide a temperature-based apparent strain measurement device for a high-temperature strain gauge that can accurately measure apparent strain while holding the strain gauge under the same conditions as when the strain gauge is fixed.

[Means to solve the problem]

The temperature-based apparent strain measurement Ml of the high-temperature strain gauge according to the present invention is provided with a flange portion for fixing to the object to be measured on the detection portion that outputs an electric signal according to the strain when it receives strain, and is used under high temperature conditions. A temperature-based apparent strain measuring device for a high-temperature strain gauge is configured to detect strain occurring in the object to be measured via the flange portion, and is made of a material having at least a coefficient of linear expansion comparable to that of the object to be measured. A substrate member, on which one surface of the flange portion abuts, is made of a material having at least the same coefficient of linear expansion as the object to be measured, and the substrate member abuts the other surface of the flange portion in a state where the detection portion is not pressed. a presser member that is in contact with the substrate member and clamps and fixes the flange portion in cooperation with the substrate member;
A block member incorporated through a sphere disposed on the back surface of the presser member in order to evenly press the presser member against the flange portion, and a linear expansion coefficient of the substrate member whose coefficient of linear expansion is at least smaller than that of the sphere and the block member. and a clamping member for clamping the flange portion between the base plate member and the press member by clamping the block member, and the high-temperature strain gauge is pressed against the base member by the sphere, the press member, and the block member. These are housed in a heating furnace in a state where they are clamped and fixed, and the temperature of the heating furnace is changed to a predetermined temperature, and the output from the detection section of each of the high temperature strain gauges is obtained at each predetermined temperature, and the high temperature strain gauges are heated. The device is characterized in that it is configured to be able to measure apparent strain due to temperature.

[For production]

In this invention, the coefficient of linear expansion of the tightening member is made smaller than that of the sphere and block member, so that the elongation rate due to expansion of the sphere and block member is greater than the rate of expansion of the tightening member at high temperatures. This ensures that the tension created by the tightening member is maintained. As a result, the flange portion of the high temperature strain gauge can be stably and reliably clamped against the substrate member by the initial pressure contact force using the sphere and the holding member. Moreover, after measuring the apparent strain, the high temperature strain gauge can be removed from the device and used for actual operation. It is possible to measure the strain of the object to be measured by fixing it to the object to be measured. [Example] Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 4 is an enlarged view of a welded-type high-temperature strain gauge (hereinafter simply referred to as "high-temperature gauge"), which is an example of a high-temperature strain gauge that is attached to the temperature-based apparent strain measurement device according to the present invention and is used for apparent strain measurement. FIG.

In the figure, 1 is a tube made of stainless steel, etc., and in the center of this tube 1, an active element 2 made of a nickel-chromium wire or the like that is sensitive to strain is arranged bent into an inverted U-shape. ing. Further, a dummy element 3 made of the same material is wound around the active element 2 so as to be insensitive to distortion. In the tube 1 in which these active elements 2 and dummy elements 3 are arranged, powder of magnesium oxide Mg○ is sealed as an insulator. Further, one end of the tube 1 is sealed, and a lead $14, which is an input/output terminal wire connected to the active element 2 and the dummy element 3, is led out from the other end and sealed with a ceramic-based high temperature resistant adhesive 5. There is. 6 is fixed to the sensing part 1a of the tube 1, and the sensing part 1
This is the base for attaching a to the object to be measured.

In addition, the base 6, which is sensitive to the strain generated in the object to be measured,
The tube 1, magnesium oxide MgO, active element 2, etc. are collectively referred to as a detection section, and the whole is referred to as a high temperature gauge G.

FIG. 5 is a plan view showing the high temperature gauge G fixed on the object 7 to be measured. In the figure, the base 6 has flange portions 6a projecting on both sides of the tube l.
, 6b, and marks 8 are marked on these flange portions 6a, 6b to indicate welding locations by spot welding. and. The high temperature gauge G is fixed to the object to be measured 7 by spot welding the mark 8. The output from the high temperature gauge G is connected to a heat-resistant MI cable (Mineral Insulate) from the lead wire 4.
dmetal sheathed cable) 9 to the measurement equipment. Note that the lead wires 4 and M
I cable 9 is connected by welding 10, this connection part is covered with cover 1l, and cover 11 and tube 11 and M
The outer periphery of the I cable 9 is welded and sealed to form a moisture-proof structure. The strain thus generated in the object to be measured 7 is transmitted to the active element 2 via the flanges 6a and 6b, the sensing part 1a of the tube 1, and the magnesium oxide Mg○, and the resistance due to compression or tension of the active element 2 is transmitted to the active element 2. A dummy element 3 is inserted adjacent to the active element 2 on one side of a strain detection circuit (not shown) that has a Wheatstone bridge configuration.The resistance value change due to the temperature of the active element 2 itself is detected as a value change.
is electrically canceled out by the change in resistance value due only to temperature, and the influence of the temperature coefficient of resistance, which is the first factor mentioned above, is compensated for. This strain detection circuit is configured as a Wheatstone bridge in which an active element 2 and a dummy element 3 are connected to two adjacent sides on the input side, and fixed resistors are connected to the other two sides.

1 and 2 show a front view of the apparent strain measuring device according to the present invention and a sectional view taken along the line A--A in FIG. 1.

In both figures, reference numeral 12 denotes a substrate made of a material having a coefficient of linear expansion comparable to that of the object to be measured 7, and a pair of the high temperature gauges are mounted on the front surface (upper surface) and back surface (lower surface) of this substrate 12. One surface of the flange portions 6a and 6b (the fourth
(lower surface in the figure) are in contact with each other.

Reference numeral 13 designates a pair of holding plates as holding members made of a material having a coefficient of linear expansion similar to that of the object to be measured 7, and this holding plate 13 has a groove portion 13a that does not substantially press the detection portion of the high temperature gauge G. The flange portions 6a and 6b are brought into contact with the other surface (upper surface in FIG. 4) of the flange portions 6a and 6b, and cooperate with the substrate 12 to sandwich the flange portions 6a and 6b. 1
Numeral 4 denotes spheres made of stainless steel material having a large coefficient of linear expansion, and in order to press the flanges 6a and 6b evenly, a plurality of spheres 4 are placed at equal intervals as shown in FIG. In the example, 3) are provided.

15 is a pair of blocks as block members made of, for example, stainless steel material with a large linear expansion coefficient, and this block 15 is incorporated in the bottom surface of the groove 15a formed therein so as to hold the sphere l4. There is. Reference numeral 16 designates a plurality of tightening bolts as tightening members made of steel, for example, whose coefficient of linear expansion is smaller than that of the sphere 14 and the block 15. Nuts 17 are threaded through the through holes drilled in the flange portion 6 of the high temperature gauge G.
a and 6b are pressed together by the substrate 12 and the holding board 3.

As shown in FIG. 3, two high-temperature strain gauges 18 and 18 having the same accuracy as the high-temperature gauge G are attached to the tightening bolt l6 at positions 180 degrees apart from each other on its side surfaces. The elongation, or tensile force, of the bolt 16 is monitored by the gauge 18.18.

Next, the operation of the temperature-dependent apparent strain measuring device of the high temperature strain gauge according to the present invention will be explained. First, high temperature strain gauge 1 attached to tightening bolt l6
8 to a strain measuring device (not shown) via an MI cable, an electric cable, etc., and on the other hand, screw the nut 17 onto the tightening bolt 16 at room temperature and tighten it to obtain the flange portions 6a, 6b of the high temperature gauge G. The board 12 and the holding plate 1
3 and confirm that the specified tensile force has been achieved using a strain meter, and then stop tightening.

Thus, when the entire device is housed in a heating furnace or the like and the temperature is raised,
Since the linear expansion coefficients of the sphere 14 and the block 15 are larger than the linear expansion coefficient of the tightening bolt l6, a larger tensile force is applied to the tightening bolt 16 than at room temperature. Here, the pressing force in the initial state is W, the coefficient of friction between the high temperature gauge G and the substrate 12 is μ, and the elongation that expands when the high temperature gauge G rises to, for example, 550° C. If a tension is applied and stretched at room temperature by the difference from the elongation when the temperature reaches ℃, the tension F becomes F=μ·W. Furthermore, if W always satisfies the relationship F×μ·W, the high temperature gauge G will be restrained with respect to the substrate processing 2.

High temperature strain gauge 18 attached to the above tightening bolt l6
The elongation of the tightening bolt 16 is measured, and a tensile force is applied to the tightening bolt 16 in advance to determine the relationship between the elongation and the tensile force.

In the above-mentioned apparatus, for example, a steel material with a linear expansion coefficient of l1 x 10"6/℃ is used for the holding plate 3, and its thickness is set to H.
Also, the linear expansion coefficient of the sphere 14 and block 15 is 1.
If a stainless steel material with a size of 6 x 10-''/'C is used and the thickness of the sphere 14 and block 15 is 8H, the length of the tightening bolt 16 will be (H + 8H) x 2 = 18H. The temperature is increased by 1℃!J ( (
Hxl 1xlO-')+(8HX16X10-'))
The elongation is X2=278HX10-'/'C, and on the other hand,
The above tightening bolt 16 is 18HxllxlO-'℃=
The elongation is 198HXlO゜"/℃. As a result,
Bolt 16 has 278HX10-'-198HX1 (I
'=80. Since the flange portion 6a of the high temperature gauge G is subjected to a tensile strain, that is, a tensile force of OH
, 6b can always receive the tightening force from the tightening bolt l6.

According to the temperature-based apparent strain measuring device configured as described above, the following various advantages can be obtained.

First, the high-temperature gauge G is heated while being held between the substrate 12 and the holding plate ↓3, which have the same coefficient of linear expansion as the object to be measured 7, so that it is heated under almost the same conditions as when actually measuring strain. The value measured at this time is an extremely accurate apparent strain due only to the influence of temperature. Therefore, by welding a high-temperature strain gauge G to the object to be measured 7 as shown in Figure 5 to detect the strain, and by correcting the apparent strain measured as described above, the true load strain can be accurately determined. can be detected.

In addition, since it is possible to heat and measure under conditions equivalent to the actual measurement conditions without welding, gauge characteristics such as gauge sensitivity and fatigue life are not impaired, and the measured apparent strain value is accurate. Moreover, the high-temperature gauges used to measure apparent strain can be used as they are for actual measurements without any damage, making them extremely economical.

In addition, since the apparent strain of all high-temperature gauges G is measured while being fixed to the fixed plate 15, each There is no reduction in accuracy due to large variations in apparent strain for each high-temperature gauge G, and the base 6 of the high-temperature gauge G is not deformed by heat and becomes unusable.

Note that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the invention.

For example, in the embodiment, an example has been described in which the apparent strain measuring device of the high temperature gauge G can be installed symmetrically on the front and back sides of the substrate 12. By configuring it in this way, the device can be simplified. Further, although an example is shown in which stainless steel, which is a material with a larger coefficient of linear expansion than steel, is used as the sphere 14 and the block 15, other materials may be used as long as they have a larger coefficient of linear expansion.

Furthermore, in order to monitor the tensile force of the tightening bolt 16, a high temperature strain gauge 18 is installed opposite to the side peripheral surface of the tightening bolt 16, but the relationship between the tightening torque and the tensile force of the tightening bolt 16 is measured in advance. If this is done, it is not necessarily necessary to attach the high-temperature strain gauge 18 to the tightening bolt l6, and it is sufficient to simply tighten the bolt 16 with a tightening torque based on the measured value before heating.

Further, in the above embodiment, the groove portion 13a serves as a relief for the detection portion.
Although a groove is formed on the holding plate ■3, a groove may also be formed on the substrate 12 side. In addition, the high temperature gauge that is the subject of apparent strain measurement is
Not limited to welded type, as long as it has a flange-like part,
It may also be something like an adhesive type. [Effects of the Invention] As detailed above, according to the present invention, the tension of the clamping member does not decrease at high temperatures, and the flange portion of the high-temperature strain gauge is strongly pressed against the substrate member by the holding member, the sphere, and the block member. With this configuration, the apparent strain due to temperature can be measured under the same conditions as when a high temperature gauge is actually attached to the object to be measured, and since the high temperature strain gauge is not welded to the substrate member, it can be easily removed. I can do it,
There is no problem in adhering to the object to be measured.
Furthermore, it is possible to provide a temperature-based apparent strain measuring device that does not impair gauge characteristics such as gauge sensitivity and fatigue life.

[Brief explanation of drawings]

Fig. 2 is a front view of a temperature-dependent apparent strain measuring device for a high temperature strain gauge according to an embodiment of the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. l, and Fig. 3 is a FIG. 4 is a front view showing a state in which a high temperature strain gauge is attached to the side circumferential surface of a tightening bolt as a component of the present invention in order to measure the tensile force of the bolt. An enlarged cross-sectional view, FIG. 5 is a plan view showing the state in which the high temperature strain gauge is attached to the object to be measured, and FIG.
FIG. 2 is a cross-sectional view of a conventional strain gauge temperature characteristic measuring device. G...High temperature strain gauge, 1...Tube, 6...
Base, 6a, 6b...flange part, 7...
...Object to be measured, 12...Substrate,
13... Pressing plate, 13a...
・Groove portion, 14... Sphere, 15.
...Block, 15a ... Concave groove, 16 ... Tightening bolt, l7 ...
・Nut, 18...High temperature strain gauge. Figure 1 Figure 3 Figure 4? Figure 5 Figure 0 Figure 6

Claims (3)

[Claims] (1) A flange part for fixing to the object to be measured is provided on the detection part that outputs an electric signal according to the strain when it receives strain, and the flange part is used to absorb the strain that occurs in the object to be measured under high temperature. In the temperature-based apparent strain measurement device of a high-temperature strain gauge, the substrate is made of a material having at least a coefficient of linear expansion comparable to that of the object to be measured, and one surface of the flange portion is in contact with the substrate. The member is made of a material having a coefficient of linear expansion at least similar to that of the object to be measured, and is brought into contact with the other surface of the flange portion without pressing the detection portion, so that the flange portion cooperates with the substrate member. a presser member that is clamped and fixed by the presser member, a block member that is assembled via a sphere provided on the back surface of the presser member in order to press the presser member evenly against the flange portion, and at least the sphere and the block member. a tightening member for tightening the substrate member and the block member to a value smaller than the coefficient of linear expansion so as to press the flange portion between the substrate member and the holding member; The high-temperature strain gauges are clamped and fixed by block members and housed in a heating furnace, and the heating furnace is changed to a predetermined temperature, and the detection portion of each high-temperature strain gauge is detected at each predetermined temperature. A temperature-dependent apparent strain measuring device for a high-temperature strain gauge, characterized in that it is configured to obtain an output and measure the temperature-dependent apparent strain of the high-temperature strain gauge. (2) The temperature of the high-temperature strain gauge according to claim 1, characterized in that the high-temperature strain gauges are installed on the side peripheral surface of the clamping member at a distance of 180° to monitor the tensile force of the clamping member. apparent strain measuring device. (3) Apparent strain due to temperature of the high-temperature strain gauge according to claim 1, characterized in that a pair of presser members, spheres, and block members are symmetrically arranged on both the front and back surfaces of the substrate member. measuring device.