JP2013036878A - Completely reversed four-point bending test device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure true fatigue strength of a test piece when conducting a completely reversed four-point bending test.SOLUTION: A completely reversed four-point test device comprises: fixing and supporting means 2 and 3 for supporting corresponding positions of one side 1a and the other side 1b of a test piece 1 at an interval L; two first loading points 4a and 4b separately loaded on the one side 1a of the test piece 1 within the interval L of the fixing and supporting means 2 and 3; and two second loading points 5a and 5b separately loaded on the other side 1b of the test piece 1 within the interval L of the fixing and supporting means 2 and 3. The first loading points 4a and 4b and the second loading points 5a and 5b are arranged so as to be loaded on the test piece 1 at different positions.

Description

  The present invention relates to a double swing four-point bending test apparatus for testing the fatigue strength of a material by repeatedly applying positive and negative bending stresses to a test piece.

  As a bending test apparatus for test pieces, two fulcrum points are fixed at a predetermined distance in the horizontal direction, and one side (lower surface) of the test piece is supported by each fulcrum. In this case, one pressing point is pressed from the other side (upper surface) of the test piece in the case of three-point bending, and two pressing points are pressed in the case of four-point bending so as to apply a bending stress to the test piece. Yes (see Patent Document 1).

  However, Patent Document 1 has a disadvantage that only the material strength data for bending in one direction can be obtained because the swinging is performed by bending the test piece only in one direction. In other words, in the design of mechanical members and the like, there are many cases where fatigue strength data is required in both swings in which positive and negative bending stresses are repeatedly applied to a test piece, but material strength data in one swing is required for a material. There was a possibility that the true performance could not be grasped.

  For this reason, there is a double swing four-point bending test apparatus in which positive and negative bending stresses can be repeatedly applied to the test piece (see Patent Document 2).

  The four-point bending test apparatus of Patent Document 2 has a center jig and side jigs located on both sides of the center jig, and the side jig has a lower fulcrum and an upper fulcrum that are aligned vertically. The center jig is provided at a position where the lower loading point and the upper loading point by rollers arranged on the left and right sides are aligned vertically. The test piece is disposed between the lower fulcrum and the upper fulcrum of the side jig and between the lower and upper loading points of the center jig.

  Then, by moving the center jig in the center up and down, the test piece is positively and negatively bent alternately by the lower and upper loading points of the center jig, and compressed to one side and the other side of the test piece. It is possible to load repeatedly from stress to tensile stress.

JP 2006-258454 A JP 2000-131206 A

  However, in the four-point bending test apparatus described in Patent Document 2 described above, the lower loading point and the upper loading point provided in the side jig are arranged at positions that coincide with each other in the vertical direction. Had a serious problem.

  That is, in a double-bending bending test in which positive and negative bending loads are repeatedly applied to a test piece, it is known that fatigue fracture occurs on the surface opposite to the side on which the loading point of the test piece is pressed. In the configuration in which the lower loading point and the upper loading point are aligned at the upper and lower positions as in Document 2, the pressing load due to the loading point acts on the site where fatigue failure occurs. There was a possibility that a performance different from the fatigue strength of the steel was measured.

  The present invention has been made in view of the above-described conventional problems, and an attempt is made to provide a double swing four-point bending test apparatus capable of measuring the true fatigue strength of a test piece when performing a double swing four-point bending test. To do.

According to the present invention, fixed support means for supporting the corresponding positions of one side and the other side of the test piece with an interval therebetween, and the test piece is loaded on one side of the test piece within the interval of the fixed support means. Two first loading points, and two second loading points that are separated and loaded on the other side of the test piece within the interval of the fixed support means,
The present invention relates to a double swing four-point bending test apparatus, wherein the first loading point and the second loading point are arranged to be loaded on a test piece at different positions.

  In the double swing four-point bending test apparatus, it is preferable that the two first loading points are arranged with an interval between the two second loading points.

  In the double swing four-point bending test apparatus, it is preferable that two first loading points and two second loading points are provided in one moving block driven by a push-pull means.

  In the double swing four-point bending test apparatus, it is preferable that at least one of the two first loading points and the two second loading points is supported so that the separation interval can be adjusted.

  According to the double swing four-point bending test apparatus of the present invention, an excellent effect that the true fatigue strength of the test piece can be measured by the double swing four-point bending test can be obtained.

It is a perspective view which shows the outline of the 1st Example of the double swing four-point bending test apparatus of this invention. It is a perspective view which shows the outline of the 2nd Example of the double swing 4-point bending test apparatus of this invention. It is a front view which shows the outline of the 3rd Example of the double swing 4-point bending test apparatus of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment of a double swing four-point bending test apparatus according to the present invention. Fixed support means 2 and 3 comprising, for example, rolls 2a, 2b, 3a, and 3b are provided so as to support the positions at a predetermined interval L (support span).

  On the other hand, one side 1a of the test piece 1 in the interval L (support span) between the fixed support means 2 and 3 has a predetermined separation interval S1 (loading span), and the test piece from the direction of the arrow A. Two first loading points 4a and 4b made of, for example, a roll for loading a pressing force on 1 are provided. The two first loading points 4a and 4b are simultaneously pressed by the first pressing means 4 with the same pressing force. Further, the other side 1b of the test piece 1 in the interval L (support span) between the fixed support means 2 and 3 has a predetermined separation interval S2 (loading span), and the test piece 1 from the direction of arrow B. Two second loading points 5a and 5b made of, for example, rolls for loading the pressing force are provided. The two second loading points 5a and 5b are simultaneously pressed by the second pressing means 5 with the same pressing force.

  The first loading points 4a and 4b and the second loading points 5a and 5b are arranged with their upper and lower positions shifted in the longitudinal direction of the test piece 1 so as to load the test piece 1 at different positions. ing.

  In the embodiment shown in FIG. 1, the separation interval S1 between the first loading points 4a and 4b is larger than the separation interval S2 between the second loading points 5a and 5b, and the two first loading points 4a and 4b are It arrange | positions so that two 2nd loading points 5a and 5b may be pinched | interposed.

  Reference numeral 6 denotes an observation apparatus in which the surface state of the test piece 1 is observed in a non-contact manner by an optical or magnetic method. As a method of observing the state of the surface of the test piece 1, in addition to the observation device 6, a strain gauge or the like may be installed on the surface of the test piece 1 or may be observed visually.

  Next, the operation of the embodiment of FIG. 1 will be described.

  In order to conduct a fatigue strength test by swinging the test piece 1 with the double swing four-point bending test apparatus of FIG. 1, the test piece 1 is supported by the fixed support means 3 arranged at a predetermined interval L (support span). To do.

  Subsequently, the test piece 1 is pressed in the A direction from the lower side by the two first loading points 4a and 4b, and a load is applied to bend the test piece 1 upward. Then, the load which presses the test piece 1 in the B direction from the upper side by two 2nd loading points 5a and 5b and bends the test piece 1 downward is given. The pressing force applied to the test piece 1 by the first loading points 4a and 4b and the second loading points 5a and 5b is determined based on the pressing force expected to be received by the material in the actual machine.

  As described above, the fatigue of the test piece 1 due to both swings is repeated by repeating the pressing of the test piece 1 by the first loading points 4a and 4b and the positive and negative pressing by the pressing of the test piece 1 by the second loading points 5a and 5b. A strength test is performed. In the fatigue strength test, the number of stress loads from when the positive / negative pressing operation to the test piece 1 is started until the test piece 1 breaks is counted, and the number of stress loads counted until the test piece 1 is broken. Is used to measure the fatigue strength of the test piece 1.

  Further, as described above, when positive and negative pressure is repeatedly applied to the test piece 1, the surface roughness of the test piece 1 and cracks due to fatigue are generated on the surface of the test piece 1 before the fracture. For this reason, by observing the state of the surface of the test piece 1 with the observation device 6, it is possible to observe the change in the state of the test piece 1 until the test piece 1 is broken.

  At this time, in the double swing four-point bending test apparatus of FIG. 1, since the separation interval S2 between the second loading points 5a and 5b is smaller than the separation interval S1 between the first loading points 4a and 4b, the second loading point. The bending angle of the test piece 1 bent from the top to the bottom by pressing the 5a and 5b is larger than the bending angle of the test piece 1 bent from the bottom to the top by pressing the first loading points 4a and 4b. Therefore, when the pressing force by the first loading points 4a and 4b and the pressing force by the second loading points 5a and 5b are the same, the bending stress received by the test piece 1 is the stress caused by the first loading points 4a and 4b. The stress due to the second loading points 5a and 5b becomes larger than that.

  For this reason, if the operation of applying positive or negative bending to the test piece 1 is continued as described above, fatigue failure such as cracking occurs on one side (lower surface) of the test piece 1 opposite to the second loading points 5a and 5b. To come. In other words, in the configuration of FIG. 1, the fatigue occurs in the generation range X between the first loading points 4a and 4b on one side 1a (lower surface) of the test piece 1 on the opposite side of the second loading points 5a and 5b having a small separation interval S1. Destruction will only occur in a limited way. Accordingly, the fatigue fracture can be observed by observing the generation range X between the first loading points 4a and 4b on the lower surface of the test piece 1 by the observation device 6 or by visual observation. In addition to being able to greatly reduce, reliable measurement can be performed.

  In the double swing four-point bending test apparatus of FIG. 1, the first pressing means 4 alternately presses the first loading points 4a and 4b and the second pressing means 5 presses the second loading points 5a and 5b. Therefore, it is necessary to synchronize the push / pull operation by the first pressing means 4 and the push / pull operation by the second pressing means 5.

  FIG. 2 shows a second embodiment of the double swing four-point bending test apparatus according to the present invention in which it is not necessary to synchronize the push-pull operation by the first press means 4 and the push-pull operation by the second press means 5 in FIG. In FIG. 2, the first loading points 4 a and 4 b and the second loading points 5 a and 5 b are mounted on one moving block 7, and the moving block 7 is moved in the A direction by one push-pull means 8. Push and pull in the B direction. According to the configuration of FIG. 2, the moving block 7 is driven only by one push / pull means 8, and the test piece 1 is moved to the one side 1a by the first loading points 4a and 4b and the second loading points 5a and 5b. Both swings can be performed by alternately pressing from the side 1b.

  FIG. 3 shows a third embodiment of the double swing four-point bending test apparatus of the present invention. In this embodiment, at least one of the first loading points 4a and 4b and the second loading points 5a and 5b is shown. However, the separation interval can be adjusted. The embodiment of FIG. 3 shows a case where the present invention is applied to the apparatus of FIG. 2, and a support base 9 is provided so as to separately support the first loading points 4a and 4b. The separation interval S <b> 1 can be changed by enabling movement in the longitudinal direction of the test piece 1 along the guide groove 10 provided on the surface. Although FIG. 3 shows the case where the first loading points 4a and 4b can be moved, the second loading points 5a and 5b may be moved, and the first loading points 4a and 4b and the second loading points 4a and 4b may be moved. You may enable it to move both the loading points 5a and 5b.

  As shown in FIG. 3, the bending stress applied to the test piece 1 can be changed by changing the spacing S1, S2 between at least one of the first loading points 4a, 4b and the second loading points 5a, 5b. it can.

  In addition, the double swing four-point bending test apparatus of the present invention is not limited to the above-described embodiment, and various shapes can be used for the loading point, and other points do not depart from the gist of the present invention. Of course, various changes can be made within the range.

DESCRIPTION OF SYMBOLS 1 Test piece 1a One side 1b The other side 2,3 Fixed support means 4a, 4b 1st loading point 5a, 5b 2nd loading point 7 Moving block 8 Pushing / pulling means L space | interval S1, S2 space | interval space S3 space space

Claims (4)

Fixed first support means for supporting corresponding positions on one side and the other side of the test piece with an interval between them, and two first parts that are loaded on one side of the test piece within the interval of the fixed support means. A loading point and two second loading points that are spaced apart and loaded on the other side of the test piece within the interval of the fixed support means,
A double swing four-point bending test apparatus, wherein the first loading point and the second loading point are arranged to be loaded on a test piece at different positions.   2. The double swing four-point bending test apparatus according to claim 1, wherein the two first loading points are arranged with an interval between the two second loading points.   The double swing four-point bending test apparatus according to claim 1 or 2, wherein the two first loading points and the two second loading points are provided in one moving block driven by the push-pull means. .   The double swing four-point bending according to any one of claims 1 to 3, wherein at least one of the two first loading points and the two second loading points is supported so that the separation interval can be adjusted. Test equipment.

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