JP2014016200A - Multiaxial stress application testing device and prediction method of stress corrosion cracking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial stress application testing device which achieves the improvement in reliability of a result of a test at a multiaxial stress field, and a prediction method of stress corrosion cracking.SOLUTION: A multiaxial stress application testing device includes: an annular member 5 made of a material having flexibility; a test piece 6 including a body piece 11 arranged at the diametrical center of the annular member 5, and a plurality of arm pieces 12 which are arranged at intervals in a circumferential direction and which extend from the body piece 11 toward the outside of the annular member 5 in a radial direction; and nut members 14 which are externally engaged with each of the arm pieces 12 and which fix the arm pieces 12 to the annular member 5 while pressing the annular member 5 in the radial direction.

Description

  The present invention relates to a multiaxial stress application test apparatus applied to a test for stress corrosion cracks occurring in a metal material, and a method for predicting stress corrosion cracks using the same.

  For example, in a metal member used for equipment for power generation facilities, etc., the three conditions of the surrounding environment to which the metal member is exposed, the material of the metal member, and the stress applied to the metal member overlap, and stress corrosion cracking (SCC: Stress Corrosion Cracking) Is known to occur.

  Here, it has been reported that in a multiaxial stress field, there is a possibility that a grain boundary progress type stress corrosion cracking in which a crack propagates along a crystal grain boundary is more likely to occur than a uniaxial stress field. Therefore, it seems that there is an increasing need to predict stress corrosion cracking by conducting tests in a multiaxial stress field, but there are not many tests in a multiaxial stress field because the test is not easy. It is the current situation that is not done.

  By the way, as an example of such a test in a multiaxial stress field, Patent Document 1 discloses a test apparatus in which a test piece is sandwiched between a first test jig and a second test jig and the test piece is tightened with a bolt. Has been. In this apparatus, a multiaxial stress test can be performed by applying stress from the ZX plane and the ZY plane with bolts.

JP 2002-296161 A

  However, in the test apparatus disclosed in Patent Document 1, since the stress is adjusted by the bolt, it may be difficult to accurately manage the stress level in the test section. Further, since the test is performed in a state where the test piece is sandwiched between the jigs, the visibility is poor, and it is not easy to accurately grasp the occurrence of the crack. Furthermore, during a test at a high temperature, there is a possibility that relaxation may occur due to relaxation of the stress of the test piece due to thermal deformation of the bolt.

  The present invention has been made in view of such circumstances, and provides a multiaxial stress application test apparatus for improving the reliability of test results in a multiaxial stress field and a method for predicting stress corrosion cracking. Objective.

In order to solve the above problems, the present invention employs the following means.
That is, the multiaxial stress application test apparatus according to the present invention includes an annular member made of a flexible material, a main body piece arranged radially inside the annular member, and a plurality of pieces spaced apart in the circumferential direction. A test piece provided with an arm piece provided and extending radially outward of the annular member from the body piece;
A nut member that is externally fitted to each of the arm pieces and that fixes the arm piece while pressing the ring member in a radial direction.

According to such a multiaxial stress test apparatus, when the nut member is tightened, a tensile force and a compressive force can be applied to the main body piece via the arm piece. At this time, it is possible to adjust the tensile force and the compressive force only by adjusting the nut member to generate an arbitrary multiaxial stress on the test piece.
In addition, since the annular member has flexibility, for example, when a thermal deformation or the like occurs in the test piece during the test, the annular member is elastically deformed so as to counter the thermal deformation, thereby generating relaxation. Can be prevented.

  Further, a spring member that applies a biasing force to the annular member so as to resist deformation in the radial direction of the annular member may be further provided between the annular member and the nut member.

  With such a spring member, for example, when a thermal deformation or the like occurs in a test piece during a test, the annular member can counter this thermal stress and can also counter this spring member, and further relaxation occurs. Prevention can be achieved.

  Furthermore, the method for predicting stress corrosion cracking according to the present invention includes an annular member made of a flexible material, a main body piece arranged radially inside the annular member, and a plurality of pieces spaced apart in the circumferential direction. A test piece having an arm piece that is provided and extends radially outward of the annular member from the main body piece, while being externally fitted to the arm piece and pressing the annular member in the radial direction A method for predicting stress corrosion cracking using a multiaxial stress load test apparatus comprising a nut member for fixing the arm piece, wherein the stress corrosion cracking test is performed in a multiaxial stress field and test data is acquired. Compare the test data of the first process with the test data of the first process and the test data of the second process by preparing the test data of the stress corrosion cracking in one process and the uniaxial stress field, and calculate the correlation And a third process To.

  According to such a stress corrosion cracking prediction method, from the test data in the uniaxial stress field prepared in the second process and the correlation in the third process, without performing many tests in the multiaxial stress field. It becomes possible to obtain data on multiaxial stress under various conditions. Since uniaxial stress field tests have been carried out many times and there is abundant test data, it is possible to obtain reliable data by effectively using these abundant test data, and to predict stress corrosion cracking. Is possible.

  According to the multiaxial stress application test apparatus and the stress corrosion cracking prediction method of the present invention, the arm piece is fixed to the annular member by the nut member, thereby improving the reliability of the test result in the multiaxial stress field. It becomes possible to plan.

1 is an overall view of a multiaxial stress load test apparatus according to an embodiment of the present invention, and shows a case where tensile stress is generated on a test piece. 1 is an overall view of a multiaxial stress load test apparatus according to an embodiment of the present invention, and shows an arrow A in FIG. 1 is an overall view of a multiaxial stress load test apparatus according to an embodiment of the present invention, and shows a case where compressive stress is generated on a test piece. It is a general view of the multiaxial stress load testing apparatus which concerns on the 1st modification of embodiment of this invention. It is a general view of the multiaxial stress load testing apparatus which concerns on the 2nd modification of embodiment of this invention. It is a general view of the multiaxial stress load testing apparatus which concerns on the 3rd modification of embodiment of this invention. It is a general view of the multiaxial stress load testing apparatus which concerns on the 4th modification of embodiment of this invention. It is a whole figure of the cyclic | annular member of the multiaxial stress load testing apparatus which concerns on the 5th modification of embodiment of this invention, Comprising: (a) is the figure seen from the axial direction, (b) is BB of (a). A cross section is shown. It is a whole figure of the cyclic | annular member of the multiaxial stress load testing apparatus which concerns on the 6th modification of embodiment of this invention, Comprising: (a) is the figure seen from the axial direction, (b) is CC of (a). A cross section is shown. It is a general view of the cyclic | annular member of the multiaxial stress load testing apparatus which concerns on the 7th modification of embodiment of this invention, Comprising: (a) is the figure seen from the axial direction, (b) is DD of (a). A cross section is shown. It is a general view of the cyclic | annular member of the multiaxial stress load testing apparatus which concerns on the 8th modification of embodiment of this invention, Comprising: (a) is the figure seen from the axial direction, (b) is EE of (a). A cross section is shown. It is a whole figure of the cyclic | annular member of the multiaxial stress load testing apparatus which concerns on the 9th modification of embodiment of this invention, (a) is the figure seen from the axial direction, (b) is FF of (a). A cross section is shown. It is a graph which shows the relationship between the stress (sigma) in a uniaxial stress field and a multiaxial stress field, and the stress corrosion crack generation time t regarding the multiaxial stress load test apparatus which concerns on embodiment of this invention.

Hereinafter, the multiaxial stress load testing apparatus 1 according to the first embodiment of the present invention will be described.
The multiaxial stress load test apparatus 1 is an apparatus for testing stress corrosion cracking by installing it in a high-temperature environment or under water with two or more axes applied to the test piece 6 at the same time.

  As shown in FIGS. 1 and 2, the multiaxial stress load test apparatus 1 includes an annular member 5 having an annular shape around an axis P, a test piece 6 supported by the annular member 5, and an annular test piece 6. A nut member 14 fixed to the member 5 and a spring member 15 provided between the nut member 14 and the annular member 5 are provided.

  The annular member 5 is made of a flexible material. For example, a metal such as stainless steel or nickel alloy, a flexible resin, or the like is used. In addition to these materials, various materials can be used as long as they are elastically deformable so as to resist the thermal expansion / contraction of the test piece 6.

  As shown in FIG. 2, the annular member 5 is formed with through holes 5a penetrating in the radial direction at intervals in the circumferential direction when viewed from the radial direction.

  The test piece 6 includes a main body piece 11 disposed on the radially inner side of the annular member 5 and a plurality of arm pieces 12 extending radially outward from the main body piece 11.

  In the present embodiment, four arm pieces 12 are provided on the outer periphery of the main body piece 11 at intervals of 90 degrees in the circumferential direction. The radially outer end has a rod shape and is a male screw portion 12a having a male screw formed on the outer peripheral surface. The end portion on the radially outer side which is the male screw portion 12 a is inserted into the through hole 5 a of the annular member 5.

The main body piece 11 has a substantially rhombus shape, and is arranged at the central portion on the radially inner side of the annular member 5, and the arm pieces 12 are coupled to the outer periphery. In the present embodiment, the thickness dimension in the direction of the axis P of the annular member 5 is smaller than that of the arm piece 12 so as to make it easier to generate stress in the main body piece 11.
Note that the thickness dimension of the main body piece 11 is not necessarily smaller than the thickness dimension of the arm piece 12.

  The nut member 14 is provided on each arm piece 12 from the outer side in the radial direction of the annular member 5, and is screwed into a male screw portion 12 a of the arm piece 12 inserted into the through hole 5 a of the annular member 5. It is fixed to the annular member 5. By tightening the nut member 14, the annular member 5 is pressed through the spring member 15, and a tensile force is applied to the arm piece 12 toward the radially outer side.

  The spring member 15 is a coil spring that is fitted into each arm piece 12 from the outer peripheral side between the nut member 14 and the annular member 5 to urge the annular member 5 in the radial direction.

  In such a multiaxial stress load test apparatus, the arm piece 12 can be pulled radially outward with respect to the annular member 5 by tightening the nut member 14. More specifically, when the male screw portion 12a and the nut member 14 are right-hand screws, the nut member 14 is rotated clockwise as viewed from the outside in the radial direction. In this way, a tensile force can be applied to the test piece 6 via the arm piece 12.

  At this time, the tensile force applied to the test piece 6 can be adjusted by the tightening amount of the nut member 14. That is, it is possible to adjust the tensile force only by adjusting the nut member 14 and to generate an arbitrary multiaxial (biaxial in this embodiment) tensile stress on the test piece 6.

  Here, for example, before performing the test, a strain gauge is installed on the test piece 6, and the relationship between the tightening amount of the nut and the strain generated on the test piece 6 is acquired in advance to create a calibration curve. May be. By doing in this way, it becomes unnecessary to install a strain gauge at the time of testing and perform stress management, and the efficiency of testing work can be improved.

  Furthermore, since the tensile force can be adjusted for each arm piece 12, the stress condition can be easily changed, and the test conditions for various multiaxial stress fields can be accommodated.

  In addition, for example, when a test is performed in an autoclave, thermal deformation of the test piece 6 is assumed during a test under severe temperature conditions. In this respect, since the annular member 5 has flexibility, the thermal deformation of the test piece 6 can be suppressed by the restoring force due to the elasticity of the annular member 5, that is, the annular member 5 resists the thermal deformation of the test piece 6. Thereby, the relaxation which arises in the test piece 6 can be prevented.

  Further, for example, when thermal deformation or the like occurs in the test piece 6 during the test, it can be countered by the annular member 5 and also by the spring member 15, thereby further preventing the occurrence of relaxation. be able to.

  Here, as shown in FIG. 3, the nut member 14 is fastened to the male screw portion 12 a of the arm piece 12 from the radially inner side of the annular member 5, thereby compressing the arm piece 12 toward the radially inner side. it can. More specifically, when the male screw portion 12a and the nut member 14 are right-hand screws, the nut member 14 is rotated clockwise as viewed from the inside in the radial direction. In this way, a compressive force can be applied to the test piece 6 via the arm piece 12.

  Then, similarly to the case where the tensile force is applied to the test piece 6, the compression force can be adjusted by the tightening amount of the nut member 14, and the fastening position of the nut member 14 is made different for each arm piece 12, thereby pulling the tensile force. And the compressive force can be applied to the test piece 6 at the same time.

  Furthermore, when a tensile force and a compressive force are applied to the test piece 6, the stress is adjusted by tightening the nut member 14, so that a large-scale device is unnecessary. As a result, the entire apparatus including the test piece 6 can be made compact, and the cost can be suppressed. Therefore, many test pieces 6 can be created and many stress corrosion cracking tests can be performed at once, and a lot of test data can be acquired at one time.

  According to the multiaxial stress load test apparatus of the present embodiment, the test piece 6 is fixed and held on the annular member 5 using the nut member 14, thereby causing the test piece 6 to generate multiaxial stress under various conditions. The occurrence of relaxation can be prevented, and the reliability of the test results can be improved.

  The spring member 15 is not necessarily provided. In this case, the nut member 14 is provided in contact with the annular member 5, and the reaction force from the test piece 6 is received only by the annular member 5.

  Moreover, the through-hole 5a formed in the annular member 5 should just be able to penetrate at least the arm piece 12, and the opening dimension of the circumferential direction is not limited to the above-mentioned embodiment. For example, the opening dimension may be larger in the circumferential direction than the male threaded portion 12a of the arm piece 12.

  Further, as shown in FIGS. 4 and 5, the annular members 20 and 30 are not limited to an annular shape, and the outer shape may be a polygonal shape such as a quadrangle and a triangle, for example. In this case, it is preferable that the arm pieces 22 and 32 of the test pieces 21 and 31 are fixed by the nut member 14 at the center of each side of the annular members 20 and 30, that is, fixed at the position where the bending is most easy. It is preferable that In addition, it is also possible to fix the arm pieces 22 and 32 to each vertex of the annular members 20 and 30.

  Further, as shown in FIGS. 6 and 7, the arm pieces 42 and 52 of the test pieces 41 and 51 do not necessarily have to be provided at an interval of 90 degrees in the circumferential direction, and the arm pieces 42 according to the test conditions. , 52 and the interval between the arm pieces 42, 52 in the circumferential direction can be appropriately changed.

  Further, as shown in FIG. 8, the annular member 60 may be divided into two in the direction of the axis P and may be constituted by a first member 61 and a second member 62. In this case, instead of the through hole 5a (see FIG. 1), the first member 61 and the second member 62 are provided with recesses 61a and 62a that are recessed from the surface in the direction of the axis P, and the recesses 61a and 62a are connected to each other. The arm piece 12 of the test piece 6 is sandwiched and fixed so as to be positioned in the recesses 61a and 62a. By doing in this way, it can make it easier to install the test piece 6 in the annular member 60, and it becomes possible to perform a test easily.

  As shown in FIG. 9, the annular member 70 includes a first member 71 and a second member 72, and the recess 72 a may be provided only in the second member 72. And the shape of this recessed part 72a should just be able to insert the arm piece 12, for example, can also be made into the semicircle shape shown in FIG.

  The first members 61 and 71 and the second members 62 and 72 are fixed to each other by bolts 65, nuts 66, and the like. Here, as in the annular member 80 shown in FIG. 10, for example, a protrusion 81 b is provided on the surface of the first member 81 facing the axis P direction, and the second member 82 is recessed in the axis P direction from the surface facing the axis P direction. The groove 82b may be provided so that the protrusion 81b can be fitted.

  By doing in this way, position alignment with the 1st member 81 and the 2nd member 82 and position alignment with the recessed part 81a and the recessed part 82a are attained more reliably, and the test piece 6 can be pinched | interposed reliably and fixed. . In addition, this protrusion part 81b and the groove part 82b are not limited to when provided over the whole circumferential direction, You may be provided in a part of said surface of the 1st member 81 and the 2nd member 82. FIG. And if the projection part 81b can be fitted in the groove part 82b, the shape of these projection part 81b and the groove part 82b can be selected suitably.

  Further, as shown in FIG. 11, the annular member 90 is formed in a columnar shape by connecting a plurality of members 91, 92, 93, 94 with bolts 95, nuts 66, etc. in the direction of the axis P. Also good. With such an annular member 90, a plurality of test pieces 6 can be fixed simultaneously, and different tensile and compressive forces can be applied to each test piece 6. In addition, by appropriately selecting the shape of the recesses 91a, 92a, 92b, 93a, 93b, and 94a, it is possible to set a test piece 6 having a different shape on the annular member 90 and perform a test at the same time. . That is, the test can be performed under more complicated conditions.

  Further, as shown in FIG. 12, in the annular member 100, in place of the through hole 5a (see FIG. 1), concave portions 100a and 100b that are recessed from the surface facing the axis P direction of the annular member 100 toward the axis P direction. It may be provided and the arm piece 12 of the test piece 6 may be fitted and fixed to the recesses 100a and 100b.

  Specifically, when the number of the arm pieces 12 is four as in the present embodiment, the two concave portions 100a into which the two arm pieces 12 adjacent in the circumferential direction are fitted have one of the axis P directions. It is preferable that the remaining two concave portions 100b are provided on the back surface which is the surface facing the other side in the axis P direction. It should be noted that whether the concave portions 100a and 100b are provided on one surface or the other surface can be appropriately changed depending on the number of arm pieces 12 and the installation position.

  By doing in this way, the test piece 6 can be attached and fixed so as to be screwed into the annular member 100.

  Next, a method for predicting stress corrosion cracking using the multiaxial stress load test apparatus of the above-described embodiment will be described.

  The stress corrosion cracking prediction method includes a multiaxial data acquisition step (first step) in which test data in a multiaxial stress field is acquired by a multiaxial stress load test device, and a test in a prestored uniaxial stress field. A single-axis data preparation step (second step) for preparing data, and a crack prediction step (third step) for calculating a correlation by comparing these test data.

  In the multi-axis data acquisition process, a test is performed in a plurality of representative multi-axis stress fields, and the relationship between the stress σ generated in the test pieces 6, 21, 31, 41, 51 and the occurrence time t of stress corrosion cracking. Obtain test data for and create an approximate curve.

  In the uniaxial data acquisition step, already obtained test data is prepared for the relationship with the occurrence time of stress corrosion cracking in a uniaxial stress field. In addition, many tests in the uniaxial stress field have been performed in the past, and there are abundant test data.

  In the crack prediction process, test data in the multi-axis data acquisition process is compared with test data in the single-axis data acquisition process. And as shown in FIG. 13, correlation (beta) between the test data of a uniaxial stress field and the test data of a multiaxial stress field is calculated.

  By doing this, the correlation β can be applied to already accumulated uniaxial stress field test data without changing the conditions and performing a huge amount of tests in the multiaxial stress field. It is possible to predict stress corrosion cracking under the multiaxial stress field conditions. In this way, highly reliable data can be obtained, and stress corrosion cracking can be predicted.

Although the embodiment of the present invention has been described in detail above, some design changes can be made without departing from the technical idea of the present invention.
For example, you may combine suitably the test piece, annular member, etc. which were shown by the above-mentioned embodiment and modification.

DESCRIPTION OF SYMBOLS 1 ... Multiaxial stress load test apparatus 5 ... Ring member 5a ... Through-hole 6 ... Test piece 11 ... Main body piece 12 ... Arm piece 12a ... Male screw part 14 ... Nut member 15 ... Spring member P ... Axis 20 ... Ring member 21 ... Test piece 22 ... Arm piece 30 ... Ring member 31 ... Test piece 32 ... Arm piece 41 ... Test piece 42 ... Arm piece 51 ... Test piece 52 ... Arm piece 60 ... Ring member 61 ... First member 62 ... Second member 65 ... Bolt 66 ... Nut 70 ... annular member 71 ... first member 80 ... annular member 81 ... first member 81b ... projection part 82 ... second member 82b ... groove part 90 ... annular member 95 ... bolt 100 ... annular member

Claims (3)

An annular member made of a flexible material;
A main body piece disposed radially inward of the annular member, and a test piece having a plurality of arm pieces extending from the main body piece to the radially outer side of the annular member provided at intervals in the circumferential direction;
And a nut member that is fitted onto each arm piece and fixes the arm piece while pressing the annular member in a radial direction.   The spring member which provides a biasing force to the annular member so as to resist deformation in the radial direction of the annular member is further provided between the annular member and the nut member. Multiaxial stress load test equipment. An annular member made of a material having flexibility, a main body piece arranged radially inside the annular member, and a plurality of circumferentially spaced gaps from the main body piece to the radially outer side of the annular member A multi-axial stress comprising: a test piece having an arm piece extending in the direction; and a nut member that is externally fitted to each of the arm pieces and fixes the arm piece against the annular member in a radial direction. A method for predicting stress corrosion cracking using a load testing device,
A first step of performing a test of the stress corrosion cracking in a multiaxial stress field and obtaining test data;
A second step of preparing test data of the stress corrosion cracking in a uniaxial stress field;
A method for predicting stress corrosion cracking, comprising: a third step of comparing the test data of the first step and the test data of the second step and calculating a correlation.

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