JPH0736268Y2 - Young's modulus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a strain gauge for determining the Young's modulus of a material that hardens with time, such as concrete or mortar.

(B) Conventional technology Generally, in order to measure the Young's modulus of a material that has been cured with time, a test piece can be manufactured by removing the material when it is not cured during casting, or by core boring after curing to obtain a test piece. Although it is performed by certifying, it is a method that is obtained in a test room based on specific conditions. In addition to this, there is a Young's modulus meter that can be embedded in a time-curable material and can be measured outside at any time. An example of this type is that of Japanese Patent Publication No. 55-17933 previously provided by us.

(C) Problems to be solved by the invention The method for testing the test piece in (b) above is performed by partially destructing and collecting the structure, so there is a slight difference compared to the original value. In addition to the above, there was a practical problem that the Young's modulus could not be obtained immediately. Further, the embedded Young's modulus meter proposed in Japanese Patent Publication No. 55-17933 mentioned above, since only the strain tube made of vinyl chloride and the reference material are configured in the axial direction, when used for concrete, for example, The concrete that has flowed into the strain-flexing cylinder causes self-growth during hardening, and these press the reference material, causing strain in the reference material. Since this crevice is an error in the calculation of the Young's modulus, there was a problem when the self-growth value was relatively large.

(D) Means for Solving the Problem A case having a pipe shape and inner and outer surfaces formed of expandable and contractible walls, respectively, and a first chamber and a second chamber in which hollow portions of the case are arranged in the axial direction are arranged. A chamber, and strain detecting means for measuring the strain in both chambers in the axial direction, respectively.
Alternatively, a columnar reference member made of a material having a known Young's modulus is provided in one chamber of the second chamber along the axial direction and a columnar auxiliary reference member provided in the other chamber. The strain detecting means is provided on the reference member, the strain detecting means of the other chamber is provided on the auxiliary reference member, and the spatial sectional areas where the strain detecting means of both chambers are located are formed to be equal.

Further, it is preferable to use a member having an extremely low Young's modulus as the auxiliary reference member in order to obtain an accurate Young's modulus.

(E) Action The case is embedded in the time-curable material that is the object to be measured, and the first and second chambers forming the hollow portion of the case are embedded so that the time-curable material is filled. Then, after the time-curable material is hardened, when an external force in the axial direction acts on the first and second chambers from the outside, the first and second chambers are respectively deformed in the axial direction. The total deformation length of the first and second chambers is the same as the deformation length of the surrounding time-hardening material (concrete). At this time, the deformation length of each chamber is distributed in inverse proportion to the apparent Young's modulus of each chamber. That is, deformation occurs according to the equivalent cross-sectional area of both chambers, and strain is generated. Both strains are measured by the strain detecting means. Then, the detected bilateral corner value is calculated as a Young's modulus by a predetermined calculation formula.

(F) Embodiment An embodiment of the present invention will be described below with reference to the drawings. First
In FIG. 2, FIG. 2 and FIG. 3, reference numeral 1 denotes a case having, for example, a straight pipe shape with both ends opened. The case 1 is provided with an expandable and contractible wall portion such as a rubber wall 3 and a paper wall 4 attached to an outer surface and an inner surface of the resin pipe 2 based on the resin pipe 2. A first chamber 5 and a second chamber 6 are continuously formed in the upper portion and the lower portion of the hollow portion of the case 1, and the reference member 7 is provided in the first chamber 5 and the second chamber 6 is provided in the second chamber 6. The auxiliary reference member 8 is continuously arranged in the axial direction and is loosely fitted to the chamber wall apart from the chamber wall.

The reference member 7 is made of a material having a known Young's modulus, for example, made of iron and has a pipe shape, and the auxiliary reference member 8 is made of synthetic resin having a very low Young's modulus and a linear expansion coefficient, and has a pipe shape (long pillar shape) (second). The two-dot chain line in the figure indicates the boundary between the reference member 7 and the auxiliary reference member 8). The reference member 7 and the auxiliary reference member 8 have the same outer diameter at the portions where the later-described strain gauges 9 and 10 are attached. This is to equalize the spatial sectional areas of the first chamber 5 and the second chamber 6 at the strain detection positions. On the peripheral wall of the reference member 7, a plurality (two in this embodiment) of engaging portions 11, ..., 12, ... Are provided in a protruding manner, and on the peripheral wall of the auxiliary reference member 8, engaging portions 13 are provided. A plurality (two in this embodiment) are provided in a protruding manner.

Reference numeral 14 denotes a leg portion, which is formed by radially providing a plurality (two in this embodiment) from the reference member 7, and is a leg portion for positioning the reference member 7 and the auxiliary reference member 8 substantially at the axial center. Strain detecting means such as strain gauges 9 and 10 are attached to the intermediate peripheral wall of the reference member 7 and the intermediate peripheral wall of the auxiliary reference member 8, respectively.

Reference numeral 15 is a protective material provided on the surfaces of these strain gauges 9 and 10. Lead wires (not shown) drawn out from the strain gauges 9 and 10 are introduced into the reference member 7 and the auxiliary reference member 8 and connected to the cable 16 taken out from the upper end of the reference member 7.

Next, a case of measuring the Young's modulus of the time-curing material shown in the drawing, for example, concrete 17, after curing will be described. When pouring concrete 17, for example, position the axial direction up and down,
And the cable 16 is embedded in the concrete 17 so that it can be taken out from above. As a result, concrete 17 flows into and fills the first chamber and the second chambers 5 and 6 from both openings of the case 1. When the concrete 17 hardens,
The reference member 7 is fixed to the first chamber 5 by the locking portions 11 ,.
It becomes an integrated state with concrete 17 of. The auxiliary reference member 8 is also integrated with the concrete 17 of the second chamber 6 by the locking portions 13, .... When a structure is provided on the concrete 17 and an external force in the axial direction acts, the first chamber 5 and the second chamber 6 are respectively in the axial direction and are inversely proportional to the apparent Young's modulus. Change the length. The total length of the deformation of each chamber is the same as the deformation length of the concrete 17 around the case 1 having the length of both chambers. That is, strain is generated in each of the reference member 7 and the auxiliary reference member 8. These strains are detected by strain gauges 9 and 10 and the cable
With a measuring device (not shown) connected to 16 terminals,
It is measured as ε ₁ and ε ₂ . The concrete 17 around the case 1 similarly receives an external force, but since the rubber wall 3 and the paper wall 4 attached to the outer and inner surfaces of the resin pipe 2 are cut off by the elasticity, the case 17 periphery The displacement of the concrete 17 is not transmitted to the case 1. The paper wall 4 has a main function of cutting the edge between the concrete 17 in the case 1 and the inner surface of the case 1 described above.
In addition, since it is made of paper, water penetrates into it, and the function of making the cured state of the concrete 17 inside and outside the case 1 uniform can be obtained. Then, the Young's modulus is obtained from the measured strain values ε ₁ and ε ₂ by the following equation.

However, epsilon _1: strain epsilon ₂ of the reference member _7: Strain E ₃ of the auxiliary reference member 8: Young's modulus of the reference member 7 E _c: Young's modulus of the concrete 17 A _s: cross the strain detecting means of the reference member 7 is positioned Area A _c : Spatial cross-sectional area of the first and second chambers 5 and 6 at the position where strain detecting means is installed (at the time of measurement, the cross-section III-III (Fig. 3) Cross section

The Young's modulus of the auxiliary reference member 8 is extremely low and was ignored in the calculation in this embodiment. However, if it cannot be ignored in the Young's modulus of the material and its cross-sectional area, a correction term should be incorporated in the above equation to be established. become.

By the way, the volume of concrete, mortar and cement generally changes due to the progress of chemical reactions even after hardening. However, in this embodiment, the first chamber 5 and the second chamber 6 forming the hollow portion of the case 1 are configured to penetrate, and the concrete 17 of both chambers 5 and 6 interact with each other, so that strain No output is generated and the calculated Young's modulus value is not affected.

In the above embodiment, the strain detecting means is provided in the first chamber and the second chamber.
Although a strain gauge is used for both the chambers, the present invention is not limited to this, and various types can be adopted as long as the strains in the first chamber and the second chamber can be detected after the filling with the hardening material over time. Further, in this invention, the first and second chambers have the same spatial sectional area where the strain detecting means are located, and when the time-curable material is filled and cured, the strain detecting means It suffices that the equivalent cross-sections located are different. The auxiliary reference member is not only made of different materials and has the same cross-sectional area, and the auxiliary reference member is a space in which a part of the auxiliary reference member is made of the same material as the reference member but has a different cross-sectional area and is combined with another material. You may provide so that sectional area may become the same. In this case, it is necessary to add a correction at the calculation stage. Further, although the reference member is provided in the central portion in the above-mentioned embodiment, it may be provided on the cylindrical wall located around the chamber or may be dispersed in the chamber.

(G) Effect of the Invention According to the present invention, the structure is extremely simple, so that it can be manufactured at low cost. In addition, since the self-growth of the hardened material over time does not pressurize the reference member in one direction and always maintains a balanced force relationship, an error cannot be included in the calculation of the Young's modulus, and the structure is It is possible to measure the accurate Young's modulus promptly without the need to collect it partially, and it has excellent practical effects.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a perspective view, FIG. 2 is a vertical sectional view of a case, and FIG.
FIG. 3 is a sectional view taken along the line III-III in the figure. 1 …… Case 2 …… Wall (rubber wall) 3 …… Wall (paper wall) 5 …… First chamber 6 …… Second chamber 8 …… Reference member 9,10 …… Strain detection Means (strain gauge)

Claims (2)

[Scope of utility model registration request] Claims: 1. A case having a pipe shape, the inner and outer surfaces of which are formed by expandable and contractible walls, respectively, a first chamber and a second chamber in which hollow portions of the case are arranged in an axial direction, and both chambers. Strain detecting means for respectively measuring the axial strain, a columnar reference member made of a known Young's modulus provided in one chamber along the axial direction, and a columnar auxiliary reference member provided in the other chamber And the strain detecting means of one chamber is provided on the reference member, the strain detecting means of the other chamber is provided on the auxiliary reference member, and the spatial sectional areas where the strain detecting means of both chambers are located are formed equal. Young's modulus meter characterized by. 2. A Young's modulus meter according to claim 1, wherein a member having an extremely low Young's modulus is used as an auxiliary reference member.