JPS60195434A - Stress measuring method of object by stress releasing method - Google Patents

Abstract

PURPOSE:To measure exactly a stress of an object by forming slits of one pair or more on the surface of the object, and estimating a stress state from a correlation of a depth of the slit and a release distortion. CONSTITUTION:On the surface of an object 1, slits 2, 2 are formed at a prescribed interval, and formed by increasing a depth of the slits 2, 2 successively to about 1:0.4 against an interval between the slits. Also, a strain gauge 3 is stuck to the surface of a concrete block 1 placed between the slits 2, 2. In this state, pressure is applied in advance by a pressure device 8, the slits 2, 2 are deepened successively from a condition of depth ''0'' of the slits 2, 2, and on all such occasions, a distortion is measured by the strain gauge 3, and also a stress state which exists already in the object 1 is estimated from a correlation of a depth of the slits 2, 2 of this time and a release distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring stress in objects such as structures using a stress release method.

In general, the hole bottom strain method and the strain gauge embedding method are known as methods for subtracting the primary stress of rock.

The hole bottom crack method forms a poling hole in the rock.

This method involves attaching a strain gauge to the bottom of the hole and then performing overcoring to release the primary stress in the rock mass.The primary stress is then calculated backwards from the resulting strain.

In addition, in the strain gauge embedding method, the strain gauge is buried in the poling hole with cement mortar, etc., and then overcoring is performed in the same way to release the primary stress in the rock, and the primary stress is back calculated from the IT 611 value of the strain due to compression method is adopted.

In addition to these methods, there is also a method to measure the stress that exists on the surface of the bedrock or on the edges of concrete structures by attaching a strain gauge to the surface of the structure, etc. After forming a deep slit at 128 and releasing the stress at the edge, the strain value ft1t1' was measured.
Estimating the stress existing at the edge from this strain value has also been experimentally conducted.

In the hole bottom strain method and the strain gauge embedding method, overcoring is used to completely release the strain by removing the core from Motowaka, etc., so the measurement process is troublesome, and the measurement process is troublesome. damage property; However, since all the elastic components of the strain due to the -order stress are released, there is no problem with the stress release method.

This 1. On the other hand, the strain gauge t attached to the surface of the object
In the method of forming a slit with it + and releasing stress, a deep slit is created at once, and the slit is not separated from the surrounding tn:q stress release part from the object such as the base, but only the surface part is left as one piece. Since the method was used to release the stress, a deep slit was required to ensure stress release, and the influence of the connection part of the base on the measured value of released stress was evaluated. It was also difficult. Therefore, even if it is established as a measurement method in principle, there are problems in practical application, and the value of the FFI 6111 method has not yet been recognized. The process of forming slits on the surface of the target object is similar to the existing method, but it is possible to create a slit in the target object by creating a slit in the process of releasing stress. It is an object of the present invention to provide a method for primary 16-point measurement of an object, which is characterized in that it is configured in such a way that it is possible to reliably determine the stress state.

In the present invention, in order to achieve the target (r) of the base, one pair of two slits are made in the object at a predetermined distance +w e apart, one pair of slits are made in the shape of a pair of casings, one cross-shaped, etc. (a pair of slits that face each other as they form) (5 criteria: groove depth relative to the slit spacing; A method of estimating the stress profile of an object from correlations is used.

Below are the IIP details of the method of the present invention along with the drawings. We will explain the case of forming one pair of two slits as an example.The problem when releasing stress by forming slits in a target object is as follows.In other words, the spacing between the slits and the The first point is how the depth of the slit is related to the release of stress at the edges.The other problem is that when the slit is shaped, there is no structure in Motowaka'1. Stress concentration occurs near the bottom of the slit due to the primary stress present in the object, such as an object, but at this time, the stress concentration area at the bottom of the slit does not remain elastic, but sometimes plastic behavior occurs. Although these behaviors are local, the problem is that the compression is accompanied by a large strain, and how this strain affects the release strain between the slits.

For the Jth problem, we conducted an experiment in the elastic range such as photoelastic damage kA regarding the spacing and depth of slits, and found that the ratio d/B of the slit depth d and the pure slit spacing B was 0.3 to 0. 0.4
By forming a slit to a depth of (5) and performing measurements, it became clear that the same conditions could be created by completely releasing the stress on the edge.

In addition, in this case, the %Iσ of the slit material itself can be set arbitrarily. From this *experiment, we found that it is not necessary to simply increase the depth of the slit, and the slit width can also be narrow. The second problem is that if the stress concentration at the bottom of the slit is elastic, d/)3 l-lo, 3 should be released under conditions where the stress is concentrated at the edge. Experiments have revealed that due to the influence of C, even the release stress of opposite sign can be measured. This fact tells us that the effect of stress concentration at the bottom of the slit due to the -order stress exists at each step of gargling the slit, so in order to eliminate that shadow 91, it is necessary to increase the depth of the slit and release the stress at the edge. The increment of edge strain related to fc must be offset from the relationship with the decrement.

In other words, if we consider that the influence of stress (6) concentration will be the same even if the depth of the slit is slightly different, then the increase or decrease will be only the component corresponding to the change in the depth of the slit. By applying this means, it is possible to extract the elastic strain in response to the edge stress existing at the edge as the release strain.

In the above explanation of the problem, we have dealt with the case where there is no plastic behavior in the stress region near the bottom of the slit, but since the release strain is limited to the elastic component, the result is 1wl even when there is a plastic region. It is clear that this is the case.

In addition, by using the relationship between the depth of the slit and the increase/decrease of the release strain as a measurement method, the deep filtration of the slit to be formed can be made shallow, reducing the loss of vortices on the object and creating a non-destructive state. The #1 measurement process can also be simplified, making it more economical.

Next, the stress measurement method will be explained using a specific example.

Figure 1 shows an example of the method of measuring the e-4 river according to the present invention, which was also used in the development of the method. 71. The slits 2.2 are formed successively from depth 0 at predetermined intervals. Ru.

These slits 2 and 2 are shown as being parallel, but it is not necessarily necessary that they be @half-line. And this slit 2
A strain gauge 3 is affixed to the surface of the concrete block 1 which has been constructed and sandwiched between the concrete blocks 1 and 2.

A support plate 4.5 is formed on II'OIII of the concrete block j in the cap direction.A number of rods 6 are formed between the two.
1 is connected to n.

A pressurizer (jacket) 8 is placed between one support 8!4 and the edge of the concrete glock l with a contact plate 7 interposed therebetween.

In the above-mentioned state, apply the pressure to the pressurizer 8 in advance and slit sequentially from the condition of A and the slit depth of 0)
Th depth, and each time the strain is controlled by the strain gauge 3. In Figure 2, add one foot of output and create the measurement state shown in Figure 1 after π. /B, Figure 3 t'J, tl141
Figures 2 and 3 show the relationship between the edge stress between slits 2 and 2 and σB when a constant load 1 is applied to a two-dimensional photoelastic model with circular slits in the state shown in the figure. It is clear from the figure that d/B = ΩΩ nor 0. The state of release strain is the same between 2 and 2, changing linearly with Ii. This is to teach that in this part, the rate of change in release strain with respect to the depth of the slit can be considered to be approximately constant. On the other hand, as shown in FIG. 3, which is the result of a photoelastic experiment, the fringe order corresponding to the total release strain is d/B = O, a coefficient indicating the maximum slope of the curve in the range of 1 to 0.3. You can also see that it is difficult to raise the number to the 25Bk power. Although this fL is a fact based on experimental results, the validity of the processing is determined by the following consideration.

In the third factor, the one-dot chain line indicates the maximum slope, but we considered that under a nearly constant slope, a large slope correctly represents the free shadow q1, and also when the slit depth is 0.
．． Since it is thought that the surface strain between the slits (9) will definitely be released at about 25B,
If these are combined n, the total release strain can be estimated by multiplying the maximum gradient to the 0.251 power. Incidentally, since the slope and the length are complementary, use the uniform slope of 20.1 to 0.3 as the slope.1- f+, ge, the length to be multiplied is Naturally, it is different from 0.25B, such as 0.275B. However, the maximum slope and 0.25H of the third (2)
It is clear that it is possible to estimate all the primary stress that exists in advance due to the combination of . In Fig. 2, as in Fig. 3, the operating knob n is a turn (as shown in Fig. 2,
It can be seen that the strain corresponding to the added π pressure (-th order stress) in the l□□□-th can be correctly estimated.

This −order stress is measured and corresponds to the counterstress in the k strain direction.By the way, the results of the photoelastic experiment are shown in Fig. 3 when φ≧0.
With the placement of 3, the release passes through the order number 0 and becomes the reverse sign month and the first order number VC.

(10) This 71 is due to the influence of stress concentration at the bottom of the slit.

The main reason for this is that even if the stress concentration near the bottom of the slit is in the elastic region as shown in Figure 3, or in the plastic region beyond fl, the slit depth 'k O, 313 This shows that the above is not useful for measuring stress release [
,ing.

Therefore, from a safety standpoint, measurements within the range of d/B≦0.4 can be sufficient. This fire has an advantageous effect on slit processing.

On the other hand, when comparing the results in FIG. 2 with those in FIG. 3, there is no difference in the d/B ratio of 0.3. This f'L is 1d42
In the figure, plastic strain occurs due to stress concentration,
It is thought that this is the reason why the release strain exceeded O and the sign did not reverse. However, d/B = 0.1-0.
As pointed out earlier, the primary stress can be estimated by using the maximum gradient between d/B
= 0.3 to 0.4 does not require special consideration. The explanation for 0 or more relates to the case of a pair of slits, but when slits are provided in a parallel grid shape, 1 in the direction of the strain to be measured. - It only affects the measurement result of the component of Poisson's ratio regarding the strain in the intersecting direction.

Therefore, for 1ttdll+, this error can be treated as lj, ge, and a pair of slits, and the process of #-t fsllI can be simplified.

In addition, in concrete, Poisson's ratio is 0, 1 to 0.
．． Since it is about 15, the error due to this can be estimated to be less than 10 inches.

By the way, the measurement of the specific 'Zk, > force on the object is shown in Figure 4 with a bamboo structure formed in the shape of a gate, as shown in Fig. 4. , it is assumed that a load 4w is applied from above. In such a case, 1111 of structure 9
Slits 2.2 are formed on four sides with a predetermined spacing between the top and bottom (7
, it is better to attach the strain gauge 3 between the two and perform the above-mentioned test and claim on the 1+ side of the release stress. o −f fr 2
', 2', 2'', 2'U cross-shaped slits are provided, and the release stress is measured by making them in gauge 3'. It is similar to

As is clear from the above explanation, the present invention provides stress ti
! Form one or more slits at a predetermined interval on the surface of the object on the 1' side.
Measure the release strain while sequentially increasing the strain in the limbs for about 4 degrees.
This is a proposal for a method for estimating the stress state already existing in an object from the correlation between the depth of the slit and the release strain. If the present invention is applied to a scale that can simplify the measurement process by making corrections using the continuous B1 sub-scale, the slit is shallow and does not essentially damage the object. It has the advantage of simplifying the process of

[Brief explanation of the drawing]

The figures are for explaining one embodiment of the present invention, and Fig. 1 is a perspective view of the testing device shown in Fig. 1, and Fig. 2 is a perspective view of the testing device shown in Fig. , (13) A diagram showing the relationship between the 11'5 ratio of the slit depth to the slit spacing and strain, Figure 3 V, f. Figure 4 is a perspective view showing the actual first measurement state. 1... Concrete Glock 2... Slit 3.
...Strain gauge 4.5...Support & (+...Rod 7...Plate 8...Expressor inventor Minoru Sanmizu Inventor 'bai(' Koshibe applicant E Co., Ltd. Sco Applicant Minoru Sanmizu (14) 2nd seal figure 3 d/s

Claims (2)

[Claims] (1) At a predetermined interval t- on the surface of the object whose stress is to be measured.
A pair or more of slits are formed in pairs separated from each other, a strain gauge is pasted on the surface of the object between the slits, and the depth of the slits relative to the distance between the slits is l:o, gradually increasing in the case by about 4. A stress measurement method for an object using the stress release method, which measures the release strain and estimates the stress state of the object from the correlation between the slit depth and the release strain. (2) The depth of the slits relative to the distance between them is 0.
．． Claim 1, characterized in that the stress state of the object is estimated from the relationship between the increment in the depth of the slit and the corresponding increase/decrease in the release strain in a region of 3 degrees or less. A method of measuring stress on an object using the stress release method.