JP2977713B2 - Bolt delayed fracture test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test apparatus for testing the limit of delayed fracture of bolts made of high-strength steel.

[0002]

2. Description of the Related Art Generally, high-strength steels such as chromium molybdenum steel and carbon steel are used for flywheels, crankshafts, and bolts for assembling the same in order to reduce the mass of the entire engine or to reduce its size. Selected and used. However, since this high-strength steel may cause a phenomenon of sudden fracture after a certain period of time when a certain stress is applied, so-called delayed fracture, the material used or the material used in actual selection It is necessary to conduct a durability test to determine whether or not the component can withstand practical use. As a result of the test, after confirming that it is within the delayed fracture limit corresponding to general fatigue fracture, work the same material as the test material into a bolt or the like, or use a bolt of the same quality as the test bolt.

[0003] Heretofore, the present applicant has proposed a delayed fracture test apparatus (Japanese Utility Model Application Laid-Open No. 55-113949) which is an apparatus for testing the durability at the stage of material before forming a bolt. In this device, a pair of columns are erected on a base, a spring is fixed horizontally across the upper end of the column, and a tension jig is attached to the center of the spring so as to be vertically movable and fixed. After fixing the fixing jig on the upper surface of the base opposite to and fixing the test sample via the connecting jig between the tension jig and the fixing jig,
It is configured to apply stress.

[0004] However, it is difficult to perform a delayed fracture test in the practical stage of the bolt with the above-mentioned apparatus. For this reason, the device shown in FIG. 5 was prototyped and tested. That is, an insertion hole 2a into which the test bolt 1 can be inserted is provided in the upper center of the cylindrical body 2 having an elliptical cross section, and the male screw portion of the bolt 1 is screwed in the lower center of the cylindrical body 2 facing the insertion hole 2a. A compatible screw hole 2b is provided. The cylindrical body 2 is made of a highly elastic steel material, and the test bolt 1 is inserted through the insertion hole 2a and the screw hole 2b is formed.
When the head 1a is brought into close contact with the edge of the insertion hole 2a, a stress corresponding to the load applied to the bolt 1 during actual use is generated. It is considered that the delayed fracture occurs mainly due to hydrogen in the high-strength steel. Therefore, the cylindrical body 2 is immersed in the oxidizing liquid 3 with the bolt 1 screwed thereto, and is immersed in a corrosive atmosphere. Left unattended, promoting delayed destruction.

[0005]

However, in the delayed fracture test apparatus described above, the cylindrical body is large compared to the test bolt and its manufacture is not easy. In addition, since the shape and elastic force of the cylinder are uniform, if the length of the test bolt is changed or if you want to test the test bolt with different tensile stress, a new cylinder that meets the test conditions Had to be prepared. Moreover, in order to test a plurality of test bolts, a plurality of insertion holes and screw holes are provided in the cylinder, and when a plurality of test bolts are tested at the same time, the stress generated by tightening the test bolts affects adjacent test bolts. There is a trouble that the interval between the insertion holes must be increased so as not to prevent the trouble, or a cylinder must be prepared for the number of test bolts. Further, when the material of the attached body to which the test bolt is actually fixed and the material of the cylindrical body are not the same, there is a problem that the reliability of the test data is not high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bolt delayed fracture test apparatus which is small in size and easy to manufacture.
It is another object of the present invention to provide a delayed fracture test apparatus for a bolt having a high test throughput by simultaneously testing a plurality of test bolts with a single test apparatus. Still another object of the present invention is to test even if the test bolt has a slightly different length, to apply a different tensile stress to the test bolt, to perform the test, and to perform the test under a condition close to the condition actually used. It is an object of the present invention to provide a bolt fracture test apparatus capable of performing a test.

[0007]

The configuration of the present invention for achieving the above object will be described with reference to the drawings corresponding to the embodiments. As shown in FIGS. 1 and 2, a delayed fracture test apparatus for a bolt according to the present invention has
And an insertion hole 12 into which the male screw portion 13a and the shaft portion 13c of the test bolt 13 can be inserted, and a through hole 1 communicating with the insertion hole 12 for feeding the oxidizing fluid 16 into the insertion hole 12.
4 is provided in the block body 11, and a female screw portion 12 into which a male screw portion 13 a can be screwed is provided in a portion near one edge of the insertion hole 12.
b is formed, one end of the through hole 14 faces the non-threaded portion 12 a of the insertion hole 12 where the female screw portion 12 b is not formed, and the non-threaded portion 12 a is formed to have a larger diameter than the shaft portion 13 c of the bolt 13. When the male screw portion 13a is screwed into the female screw portion 12b and the bolt 13 is tightened with a predetermined torque to bring the head 13b of the bolt 13 into close contact with the other hole edge of the insertion hole 12, the bolt 13 is inserted into the insertion hole 12 through the through hole 14. The oxidizing fluid 16 is fed so that a predetermined tensile stress is generated in the bolt 13.

The oxidizing fluid 16 is an oxidizing liquid, and the metal block 11 is immersed in a storage tank 17 for storing the oxidizing liquid 16 so that the insertion hole 1 is inserted through the through hole 14.
It is preferable to feed the oxidizing liquid 16 to 2. Further, as shown in FIG. 2, a plurality of insertion holes 12 are provided at intervals in the metal block body 11, and cuts 11c for cutting off the stress generated by the bolts 13 tightened in the adjacent insertion holes 12 are inserted. It is preferable to provide the block body 11 between the holes 12 so as to be parallel to the insertion hole 12 and to divide the block body 11 for each insertion hole.

Further, as shown in FIGS. 3 and 4, a notch 11 provided to divide the metal block body 11 is provided.
c, a metal partition plate 1 inserted so as to protrude from a surface 11b having the other hole edge of the insertion hole 12 of the block body 11
8 and a through hole 19 made of the same material as a member which is arranged on the divided surface of the block body 11 and is actually fixed by the same bolt as the test bolt 13 and has the same diameter as the insertion hole 12.
a, and an attached body 19 having a side hole 19b communicating with the through hole 19a. The male screw portion 13a of the bolt 13 inserted into the through hole 19a and the insertion hole 12 is screwed into the female screw portion 12b with a predetermined torque. When the bolt 13 is tightened to bring the head 13b of the bolt 13 into close contact with the hole edge of the through hole 19a, the oxidizing fluid 16 is fed into the through hole 19a and the insertion hole 12 through the side hole 19b and the through hole 14. Preferably, the bolt 13 is configured to generate a predetermined tensile stress.

[0010]

1 and 2, the male screw portion 13a and the shaft portion 13c of the test bolt 13 are connected to the non-threaded portion 1 of the insertion hole 12.
After insertion into 2a, the male screw portion 13a is screwed into the female screw portion 12b. The head 13b of the bolt 13 is tightened by applying a predetermined torque with a tightening tool such as a torque wrench. Thereby, the head 13b of the bolt 13 comes into close contact with the surface of the block body 11 having the hole edge of the insertion hole 12, and a predetermined tensile stress is applied to the shaft portion 13c. The through hole 1 provided in the block body 11 with a predetermined tensile stress applied to the test bolt 13
From 4, the oxidizing fluid 16 is sent around the bolt shaft 13 c in the insertion hole 12. Thus, the oxidizing fluid 16 comes into contact with the shaft portion 13c made of high-strength steel, and a corrosive environment is formed.

In the apparatus shown in FIG. 3 and FIG.
After the partition plate 18 is inserted into the block 1c, the mounted body 19 is placed on the surface of the block body 11 having the hole edge of the insertion hole 12, and the test bolt 13 is inserted into the through hole 19a and the insertion hole 12 so that the male screw portion 13b is inserted. It is screwed into the female screw part 12b. When a predetermined torque is applied to the head 13b of the bolt 13, the attached body 19 tries to rotate together, but the attached body 19 comes into contact with the partition plate 18 to prevent rotation. The bolt 13 is tightened with a predetermined torque, and is sent from the side hole 19b and the through hole 14 to the periphery of the bolt shaft 13c in the insertion hole 12 with a predetermined tensile stress applied to the shaft 13c. Thereby, the oxidizing fluid 1
6 comes into contact with the shaft portion 13c made of high-strength steel to form a corrosive environment. The test bolt 13 can be evaluated under conditions close to actual use conditions by interposing the attached body 19 made of the same material as a member actually fixed by the same bolt as the test bolt 13.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIGS. 1 and 2, the test apparatus main body of the present embodiment includes a substantially rectangular parallelepiped carbon steel block body 11. The block body 11 is provided with five insertion holes 12 in which the male screw portion 13a and the shaft portion 13c of the test bolt 13 can be inserted in parallel at predetermined intervals. The test bolt 13 is made of the same material as the bolt actually used, and is made of high-strength steel in this example. These insertion holes 12 pass from one surface 11a of the block body 11 to the other surface 11b. On one surface 11a, a female screw portion 12b to which the male screw portion 13a of the bolt 13 can be screwed is formed in a portion of the insertion hole 12 near the hole edge. The block 1 has a shaft portion 1 of the test bolt 13 extending from the other surface 11b to a predetermined position.
A non-threaded portion 12a having a diameter larger than the diameter of 3c is provided.
The two through holes 14 communicating with the insertion holes 12 for feeding 6 are provided perpendicular to the insertion holes 12 by two. These through holes 14
One end of the insertion hole 12 has no female screw portion 12b.
Facing the non-threaded portion 12a. One of the two through holes 14 faces the non-threaded portion 12a near the female screw portion 12b, and the other one is provided near the surface 11b of the block body 11. The length of the insertion hole 12, that is, the height of the block body 11,
The length is determined by the length of the shaft portion 13c of the test bolt 13, and the male screw portion 13a is determined so as not to protrude from the one surface 11a of the block body 11 in a state where the test bolt 13 is tightened. A cut 11c is formed in the block body 11 between the five insertion holes 12 so as to divide the block body 11 for each insertion hole from its surface 11b to a position deeper than the depth of the non-threaded portion 12a.
Are provided in parallel with the insertion holes 12.

A description will be given of a test method using the thus configured bolt fracture test apparatus. As shown in FIG. 1, the test bolt 13 is inserted into the insertion hole 1 from the male screw portion 13a side.
After being inserted into the second non-threaded portion 12a, the male threaded portion 13a is screwed into the female threaded portion 12b. The head 13b of the bolt 13 is rotated until the head 13b comes into close contact with the hole edge surface 11b of the insertion hole 12. From this state, the bolt 13 is tightened with a torque actually applied to the bolt 13 by a tightening tool such as a torque wrench or more. Thus, test bolt 1
The shaft 13c between the third head 13b and the external thread 12b is subjected to a tensile stress actually used or higher. Similarly, although not shown, four test bolts 13 are similarly inserted into the other four insertion holes 12 and tightened. The stress generated by the bolt 13 fastened to the adjacent insertion hole 12 by the cut 11c is cut off.

Next, in a state where a predetermined tensile stress is applied to the five test bolts 13, the block 11 is immersed together with the oxidizing fluid 16 stored in the storage tank 17 in order to positively establish a corrosive environment. The oxidizing fluid 16 is an oxidizing liquid such as dilute sulfuric acid, dilute nitric acid, or dilute hydrochloric acid, and is dilute sulfuric acid in this example.
By immersion, the lower through-hole 1 provided in the block body 11
Dilute sulfuric acid, which is an oxidizing fluid 16, enters from 4, and air is exhausted from the upper through-hole 14. Thereby, the space around the shaft portion 13c of the bolt 13 is filled, and the delayed fracture test is accelerated. In this example, after the block body 11 is immersed in the oxidizing fluid 16 for 14 days, the block body 11 is taken out of the storage tank 17, and the bolt 13 is removed to check for any delayed fracture.

FIGS. 3 and 4 show another embodiment of the present invention. In these figures, the same reference numerals as those in FIGS. 1 and 2 indicate the same components. The characteristic configuration of the present embodiment is that the partition plate 18 inserted into the cut 11 c so as to protrude from the surface 11 b having the hole edge of the insertion hole 12 of the block body 11 and the divided surface of the block body 11 are arranged. And the attached body 19. The attached body 19 is the test bolt 1
3 is made of the same material as the member actually fixed by the same bolt. For example, if the member to be actually fixed has been subjected to surface treatment with alloy cast iron (FCA1),
No. 9 is the same alloy cast iron (FCA1) and the same surface treatment is applied. A through hole 19a having the same diameter as the insertion hole 12 is provided at the center of the attached body 19, and a side hole 19b communicating with the through hole 19a is provided at a side portion of the attached body 19 perpendicular to the through hole 19a. Can be The attached body 19 has a cut 11 c and a block body 11.
Is a rectangular parallelepiped having a top surface and a bottom surface of a rectangle slightly smaller than the rectangle surrounded by the end side 11d. In this example, the block body 11 is made of carbon steel (S53C), and the attached body 19 is gray cast iron (FC25) of the same material as the flywheel attached to the rear end of the crankshaft of the engine.
0), and the test bolt 13 is made of high-strength steel. The total length of the male screw portion 13a and the shaft portion 13c of the test bolt 13 is substantially equal to the total length of the through hole 19a and the insertion hole 12 of the attached body 19.

A description will be given of a test method using the thus-configured bolt fracture test apparatus for bolts. First, the partition plate 18 is inserted into the cut 11c, and the upper part thereof is made to protrude from the block body 11, and then the mounting body 19 is placed on the surface 11b having the hole edge of the insertion hole 12 of the block body 11. Next, the test bolt 13 is inserted into the through hole 19a and the insertion hole 12, and the male screw portion 13b is screwed into the female screw portion 12b. When a predetermined torque is applied to the head 13b of the bolt 13 in the same manner as in the above embodiment, the mounted body 19 tries to rotate together due to frictional resistance between the head 13b and the mounted body 19. The body 19 abuts against the partition plate 18 to prevent rotation. The bolt 13 is tightened with a predetermined torque, and a predetermined tensile stress is applied to the shaft portion 13c. As a result, the bolt 13 is tightened under the conditions actually used.

To accelerate the test in this state, FIG.
As shown in (1), the block 11 is immersed in dilute sulfuric acid which is an oxidizing fluid 16 stored in a storage tank 17. The oxidizing fluid 16 penetrates through the side hole 19b and the through hole 14 and around the bolt shaft 13c in the insertion hole 12 as in the above embodiment. As a result, the oxidizing fluid 16
The contact with the third shaft portion 13c forms a corrosive environment. The test bolt 13 can be evaluated under conditions close to actual use conditions by interposing the attached body 19 made of the same material as a member actually fixed by the same bolt as the test bolt 13.

In the above embodiment, an oxidizing liquid is used as the oxidizing fluid. However, an oxidizing gas such as oxygen or hydrogen chloride gas may be used. Further, the through hole provided in the block body is provided perpendicular to the insertion hole, but this need not be the case. Further, in the above embodiment, five insertion holes are provided in the block body in parallel with each other in five rows, but the number and the direction of the insertion holes are not limited to the above embodiment. The above may be provided. Moreover, the arrangement direction may be a honeycomb shape.

Further, the partition plate may not be provided if the attached body does not rotate due to resistance when tightening the bolt with torque. Furthermore, the attached body can be used as an adjuster for adjusting the length of the test bolt.

[0020]

As described above, the test apparatus of the present invention has a through hole through which an oxidizing fluid flows, so that it can be made smaller and easier to manufacture than the conventional apparatus shown in FIG. Can be. Also, a plurality of insertion holes are provided in one block body,
By providing cuts in the block between the insertion holes, a plurality of test bolts can be tested at the same time without being affected by the tensile stress of the adjacent test bolts, which is compact and has a high test throughput. Also, if an attached body is interposed,
The test can be performed even if the length of the test bolt slightly changes, and if the attached body is made of the same material as the member that is actually fixed by the same bolt as the test bolt, it will be ready for actual use. Can be tested under similar conditions. As a result, highly reliable data can be obtained. In particular, by changing the value of the tightening torque of the test bolt, the tensile stress applied to the shaft of the test bolt can be changed widely, so that it is not necessary to prepare a test device for each value of the tightening torque. Can perform delayed fracture tests of various bolts.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along line AA of FIG. 2 showing a test apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of the test apparatus.

FIG. 3B shows a test apparatus according to another embodiment of the present invention.
-B line sectional drawing.

FIG. 4 is a perspective view of the test apparatus.

FIG. 5 is a configuration diagram of a conventional test apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Block body 11a, 11b Block body surface 11c Cut 12 Insertion hole 12a Non-thread part 12b Female thread part 13 Test bolt 13a Male thread part 13b Head 13c Shaft part 14 Through hole 16 Oxidizing fluid 17 Storage tank 18 Partition plate 19 Attached body 19a Through hole 19b Side hole

Claims (4)

(57) [Claims] The test apparatus main body is made of a metal block body.
An insertion hole (12) into which the male screw portion (13a) and the shaft portion (13c) of the test bolt (13) can be inserted, and the insertion for feeding the oxidizing fluid (16) into the insertion hole (12). A through hole (14) communicating with the hole (12) is provided in the block body (11), and the male screw portion (1) is provided in a portion near one edge of the insertion hole (12).
3a) is formed with a female screw portion (12b) that can be screwed therein, and one end of the through hole (14) faces the non-thread portion (12a) of the insertion hole (12) where the female screw portion (12b) is not formed. The non-threaded portion (12a) is formed to have a larger diameter than the shaft portion (13c) of the bolt (13), and the male threaded portion (13a) of the bolt (13) is screwed into the female threaded portion (12b) and fixed. When the head (13b) of the bolt (13) is brought into close contact with the other hole edge of the insertion hole (12) by tightening the bolt (13) with the torque of, the insertion hole is inserted through the through hole (14). A delayed fracture test apparatus for a bolt configured to generate a predetermined tensile stress in the bolt (13) in a state where the oxidizing fluid (16) is supplied to the (12). 2. The oxidizing fluid (16) is an oxidizing liquid,
A metal block is placed in a storage tank (17) for storing the oxidizing liquid.
Insert hole (12) through through hole (14) by immersing (11)
2. A bolt fracture test apparatus according to claim 1, wherein said oxidizing liquid is fed to said bolt. 3. A plurality of insertion holes (12) are provided at intervals in a metal block body (11), and said insertion holes (12) are adjacent to each other.
A notch (11c) for blocking the stress generated by the bolt (13) fastened to the block body (11) between the insertion hole (12) is parallel to the insertion hole (12) and the block body.
3. The delayed fracture test apparatus for a bolt according to claim 1, wherein the apparatus is provided so as to divide the insertion hole for each insertion hole. 4. A notch (11c) provided to divide the metal block (11) into a surface (11b) having the other hole edge of the insertion hole (12) of the block (11). The same as the metal partition plate (18) inserted so as to protrude, and the member that is disposed on the divided surface of the block body (11) and is actually fixed by the same bolt as the test bolt (13) A mounting member (19) made of the same material and having a through hole (19a) having the same diameter as the insertion hole (12) and a side hole (19b) communicating with the through hole (19a); The male thread (13a) of the bolt (13) inserted into the hole (19a) and the insertion hole (12) is screwed into the female thread (12b), and the bolt (13) is tightened with a predetermined torque to tighten the bolt (13). ) Head (1
3b) when the side hole (19a) is brought into close contact with the edge of the through hole (19a).
b) and through hole (14) through hole (19a) and insertion hole (12)
4. The delayed fracture test apparatus for bolts according to claim 3, wherein a predetermined tensile stress is generated in the bolts (13) in a state where the oxidizing fluid (16) is supplied to the bolts.