JPH03213216A - Crack progress suppressing method - Google Patents

Abstract

PURPOSE:To adequately suppress progress of a crack, generated in a constitutional member, by inserting a load receiving jig into a through hole so as to engage a loading jig therewith and fixing it to apply a load in a direction of stopping opening of the crack with the opposed load receiving jig approaching. CONSTITUTION:Paired through holes 31, 32, 33 of suitable dimension such as, for instance, circular hole passing through obverse and reverse of a constitutional member 1 are drilled by drilling work or the like in a suitable number of opposed positions sandwiching a crack 2. Now preferably, a stop hole 10 is drilled in both point end parts of the crack 2. Next, after load receiving jigs are inserted into these through holes 31, 32, 33, loading jigs, engaged with the load receiving jigs, are attached to both obverse and reverse surfaces of the constitutional member 1 and fixed by loading loads P1, P2, P3 in a direction of stopping opening of the crack 2 with the opposed load receiving jigs approaching. In this way, an opening amount of the crack 2 is reduced as shown by a dotted line, thereafter more progress of the crack is suppressed.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is a crack propagation control method suitable for extending the life of machinery structures such as bridges, cranes, and construction machines that are susceptible to fatigue cracks due to repeated loads. Concerning deterrence methods.

[Conventional technology]

Traditionally, machinery such as bridges, cranes, and construction machinery.

The following methods are often used to extend the life of a structure when cracks such as fatigue cracks are discovered in structural members.

(1) Welding repair method: A method of removing cracks and rewelding.

(2) Stop-hole method: As shown in the 7th factor diagram,
A method of relieving high stress concentration at the tip of a crack by making a circular through hole, that is, a stomb hole 1o, which communicates with the front and back of the component, at the tip of a crack 2 that has occurred in a component 1.

(3) High power friction welding method: As shown in Figure 8 (A) top view and (B) side view, splice plate 11 covers crack 2.
is applied to both the front and back surfaces of the component 1 and tightened with high-strength bolts 12 by friction welding, and as shown in the figure, the above-mentioned stop hole method (2) is often used in combination.

However, such a method has the following drawbacks.

(11) Welding repair method introduces high tensile residual stress through welding, which may cause cracks to recur or grow over a relatively short life span.Also, the problem is that it is difficult to carry out in service because it involves large-scale construction work. There is.

(2) Although the stop hole method is the simplest in terms of construction, cracks may recur and grow at the end of the stop hole 10 within a relatively short life due to stress concentration in the stop hole 10 portion.

(3) The high-strength bolt friction welding method can be expected to have a stable life extension effect by restraining the crack opening and sharing the stress with the splicing plate 11, but it is not suitable for relatively large cracks that occur in flat structures. is limited. Also, similar to <11, the construction work will be large-scale.

[Problem to be solved by the invention]

The present invention was proposed in view of these circumstances, and
The machine can be easily installed using the stop-hole method.
It is an object of the present invention to provide a crack propagation suppression method that can accurately suppress the propagation of cracks that have occurred in structural members of a structure and that can exhibit a stable life extension effect similar to the high-strength bolt friction welding method. purpose.

[Means to solve the problem]

To this end, the present invention involves drilling a pair of through holes of an appropriate shape and two dimensions that pass through the front and back of the member at an appropriate number of opposing positions sandwiching cracks that have occurred in the structural members of machines and structures, and allowing the through holes to receive loads. The method is characterized in that after a jig is inserted, a load-bearing jig is engaged with the jig, and a load is applied and fixed in a direction in which the opposing load-receiving jig approaches and stops the opening of the crack.

[Effect]

In the crack propagation prevention method of the present invention, an appropriate number of through holes are drilled at opposing positions sandwiching cracks that have occurred in a component, a load receiving jig is inserted therein, and a load is applied using a load loading jig. By simply keeping it in place, even if repeated loads are applied to the crack, high stress concentration will not occur at the crack tip, and therefore crack propagation will be appropriately inhibited, and even if cracks have occurred in the component, Can withstand long-term use.

〔Example〕

An embodiment of the crack propagation inhibiting method of the present invention will be described with reference to the drawings. Fig. 1 is a plan view showing the basic principle of the method of the present invention, and Fig. 2 is a first embodiment.

FIG. 3 shows the second embodiment, and FIG. 4 shows the third embodiment.

FIG. 5 shows a fourth embodiment, in which (A) is a plan view, and
(B) is a sectional view taken along line BB in (A), and FIG. 6 is an explanatory diagram of a specific experimental example.

First, in FIG. 1, a crack 2 is generated by a load S acting on a component l of a machine, a structure, etc., and an opening amount of δ is shown in the center of the crack 2.

Therefore, in the crack propagation inhibiting method of the present invention, through holes 311 3 of an appropriate shape and size, such as circular holes, passing through the front and back of the component 1 are provided in pairs at an appropriate number of opposing positions sandwiching the crack 2.
2+ a! 1 is bored by drilling or the like. At this time, preferably, a strike knob hole 10 is made at both ends of the crack 2.

Next, a load receiving jig, which will be described later, is inserted into the through holes 3s, 32, and 39, and the load receiving jig that engages with it is applied to both the front and back surfaces of the component 1, so that the opposing load receiving jig approaches and closes the crack 2. Load P1 in the direction that stops the opening. P2 and P9 are loaded and fixed.

As a result, the opening amount of crack 2 is 6 as shown by the dotted line in the figure.
2, subsequent crack growth will be inhibited. The greater the number of through-holes 31 etc. drilled across the crack 2, the greater the effect, but the number is naturally limited by the relationship between the dimensions of the crack 2 and the dimensions of the load-bearing jig, which will be described later. It is desirable that the jigs be as compact as possible so that a large number of pairs can be provided.

Next, in FIG. 2 of the first embodiment, -
A round bar-shaped load receiving jig 4a with a diameter that is filled in the cup and a length that protrudes from both the front and back surfaces of the component 1a is inserted, and a bar-shaped load receiving jig 5 that holds the opposing load receiving jig 4a is inserted.
A is placed on both the front and back sides of the component 1a. This load bearing jig 5a is provided with a screw 6a which is a part of the jig, and by tightening this, the opposing load receiving jig 4a
, 4a approach and can apply a load P in a direction to stop the opening of the crack 2a.

In addition, in FIG. 3 of the second embodiment, a load receiving jig 4b is inserted into the through hole 3b in the same manner as in the first embodiment, and a similar load receiving jig 5b is preheated to a high temperature. A load P is applied to both the front and back surfaces of the member 1b by the shrink fit effect.

Further, in FIG. 4 of the third embodiment, the load receiving jig 4C is inserted into the through hole 3C in the same manner as in the first embodiment and the second embodiment, and the outer peripheral surface is tapered while holding the load receiving jig 4c. A ring-shaped load-bearing jig 5C having a ring-shaped load-bearing jig 5C and a ring-shaped load-bearing jig 6c fitted on the outside with a tapered surface are placed on both the front and back sides of the component IC, and the load-bearing jig 6C is aligned with the arrow. A load P can be applied by driving in the direction of 7C. Note that after applying the load, there is a concern that a portion of the taper may loosen due to repeated loads, so it is desirable to fix both the load applying jigs 5c and 6c by welding 8C.

Furthermore, in FIG. 5 of the fourth embodiment, a load receiving jig 4d is inserted into the through hole 3d in the same manner as in each of the above embodiments, and a double ring-shaped load receiving jig is inserted into the through hole 3d. The load P can be applied by setting the tools 5d and 6d on both the front and back surfaces of the component 1d and tightening the load application jig 6d in the direction of the arrow 9d.

A specific example of an experiment in which a fatigue test was conducted using a welded structure model in order to examine the effects of the method of the present invention will be described below with reference to FIG.

The test specimen was a plate with a stiffener attached, measuring 655 cranes in length, 350 m in width, and 10 fins in thickness.Fatigue tests were conducted under a variable load of 20 tons. As a result, the number of repetitions is 9.7
X 105 times, a fatigue crack with a length of 95 m (j) in the lateral direction as shown in the dashed line circle in Fig. It was done.

Therefore, the test was interrupted at this point, and a load was applied in the direction of stopping the opening of the crack, as shown in the chain line circle in the figure, using the method of the first embodiment.

Note that no stop holes were machined at this time. Thereafter, a fatigue test was carried out under the same conditions as before the suspension, and as a result, no fatigue cracks developed at all, confirming the effectiveness of the method of the present invention.

〔Effect of the invention〕

In short, according to the present invention, an appropriate number of pairs of 1-dimensional σ through-holes passing through the front and back of the member are bored in pairs at positions that sandwich cracks that have occurred in the σ constituent members of machines and structures; By placing a load receiving jig on one person and engaging the load applying jig with the same jig, the opposing load receiving jig approaches and fixes by applying a load in the direction to stop the i4° opening of the crack. ,
The machine can be easily installed using the stop-hole method.
The present invention provides a crack propagation suppression method that can accurately suppress the propagation of cracks that have occurred in structural members of Il structures, and can exhibit a stable life extension effect similar to that of high-strength bolt friction welding. The invention is extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the basic principle of the method for inhibiting crack growth of the present invention, FIG. 2 is a first embodiment, FIG. 3 is a second embodiment, FIG. 4 is a third embodiment, and FIG. Four examples are shown, and each (
A) is a plan view, (B) is a sectional view taken along line BB in (A), and FIG. 6 is an explanatory diagram of a specific experimental example. FIG. 7 is a plan view showing a conventional stop hole method, and FIG. 8 is a plan view showing a conventional high-strength bolt friction welding method, with FIG. 7(A) being a plan view and FIG. 8(B) being a side view. 1, la, lb, lc, Ld--constituent members, 2.2a
, 2b, 2c, 2d--Crack, 3. . 32.39.3a, 3b, 3c, 3d---Through hole, 4
a, 4b, 4c, 4d=-load receiving jig, 5a, 6a, 5
b, 5c, 6c, 5d, 6d...Load loading jig, P,
, P2. P,,P...Load.

Claims (1)

[Claims] Pairs of through-holes of an appropriate shape and size passing through the front and back of the member are drilled at an appropriate number of opposing positions sandwiching the cracks that have occurred in the structural members of machines and structures, and load receiving jigs are inserted into the through-holes. A method for inhibiting crack growth, characterized in that a load-bearing jig is engaged with the jig, and a load is applied and fixed in a direction in which the opposing load-receiving jig approaches and stops the opening of the crack.