CN102163243B - Butt joint design method for implementing equal load carrying of I-shaped center crack-containing butt joint - Google Patents

Abstract

The invention discloses a butt joint design method for implementing equal load carrying of an I-shaped center crack-containing butt joint, belonging to the field of welding technology and solving the problem that the load carrying capacity of the I-shaped center crack-containing butt joint is lower than that of base material. For the butt joint with the center crack being contained in weld seam and crack existing in base material, the method mainly comprises the steps of: calculating matching ratio of fracture toughness of the joint, obtaining the stress intensity factor of a base material area, determining the stress intensity factor of a weld seam area satisfying equal load carrying when cracks exist in both the base material and the weld seam area, obtain the K-factor formula of the I-shaped center crack-containing butt joint and obtaining geometrical parameter values of the desired weld seam. And for the butt joint with the center crack being contained in weld seam and no flaw in base material, the method mainly comprises the steps of: measuring tensile strength of base material metal and fracture toughness of weld deposit metal, obtaining the K-factor formula of the I-shaped center crack-containing butt joint, determining the conditions that geometrical parameters of the equal load carrying joint reach, and obtaining geometrical parameter values of the desired weld seam. The method is suitable for flat butt joint with double sides being welded.

Description

Contain I type centre burst open joint and realize the open joint method for designing of equivalent-load

Technical field

The present invention relates to a kind of open joint method for designing, be specifically related to a kind of making and contain the open joint method for designing that I type centre burst open joint carries by the mother metal load-bearing capacity, belong to welding technology field.

Background technology

Often be unable to do without welded structure in the structural design, but because the singularity of welding process, welding joint is easy to generate pore, crackle, defective such as lack of penetration, and welding process is prone to produce bigger welding vestige stress in addition.Weld defects and welding vestige stress all make welded structure be prone to take place low stress brittle fracture, and the load-bearing capacity of joint reduces.Welding process makes that joint regional area crystal grain is thick, and various aspects of performance all decreases, and the fracture toughness that especially should distinguish reduces obviously than the fracture toughness of mother metal.For the structural research that contains defectives such as crackle and low stress brittle fracture takes place easily, should be from the fracturing mechanics angle.Three fracture parameters of fracturing mechanics can be changed between stress strength factor K, J integration, the crack tip opening displacement δ each other.

To having low stress brittle fracture in the welded structure application; Make the load-bearing capacity that has the crackle joint not reach the problem of the load-bearing capacity of mother metal; From the fracturing mechanics angle; Make welded structure to design with regard to the load-bearing capacity that how to improve welding joint, carry out corresponding research work, have realistic meaning according to the load-bearing capacity of mother metal.

Because the existence of weld defects, the crystal grain of adding the joint regional area is thick, and problems such as performance reduction and welding vestige stress all make the load-bearing capacity of joint reduce greatly.For welding joint, exist the situation of defectives such as crackle to happen occasionally at the weld seam center.Therefore take effective ways and measure to improve the load-bearing capacity of joint rather than reduce the load use to be necessary.From consulting reference materials, do not have research and report that the welded structure that there is centre burst in the weld seam is designed according to the load-bearing capacity of mother metal at present.

Summary of the invention

The purpose of this invention is to provide a kind of I of containing type centre burst open joint and realize the open joint method for designing of equivalent-load (can make weld seam contain the open joint method for designing that I type centre burst open joint carries by the mother metal load-bearing capacity), contain the problem that I type centre burst open joint load-bearing capacity is lower than the mother metal load-bearing capacity with solution.

Design concept of the present invention:, it is reached with the mother metal load-bearing capacity equate for raising contains the load-bearing capacity of I type centre burst open joint.For the situation that all has crackle in weld seam and the mother metal; Weld seam is equated with the fracture toughness matching ratio of joint with the ratio of the stress intensity factor of mother metal; Be that centre burst in the weld seam is not prior to the crackle unstable propagation in the mother metal, to guarantee that containing I type centre burst weld seam does not destroy prior to containing the crackle mother metal.For there being centre burst in the weld seam, and flawless situation in the mother metal, should make the limit stress of crackle unstable propagation in the weld seam be not less than the tensile strength of mother metal material, to guarantee that containing I type centre burst weld seam does not destroy prior to mother metal.

It more than is the load-bearing capacity that the load-bearing capacity that guarantees to contain I type centre burst open joint from static load carrying aspect is not less than mother metal.For bearing the fatigue load angle; Guarantee to contain the fatigue strength of I type centre burst open joint and be not less than mother metal fatigue lifetime; Just should make welding toe of joint have certain transition arc radius; Reducing the SCF of welding toe, thus the fatigue strength and the fatigue lifetime of improving joint.

According to this joint design thought and realization condition; The concrete thinking that contains the design of I type centre burst open joint equivalent-load is concentrated minimum weld shape scheme at first confirming stress; Study the influence trend of this weld shape scheme lower sub geometric parameter then, set up joint geometric parameter and the relation equation that contains the stress intensity factor of I type centre burst weld seam the stress intensity factor that contains I type centre burst weld seam.Contain the open joint that also there is crackle in I type centre burst mother metal for weld seam, according to confirming to satisfy the required joint geometric parameter of equivalent-load realization condition under the specific fracture toughness matching ratio condition according to joint geometric parameter of establishing and the stress intensity factor relation equation that contains I type centre burst weld seam.Contain I type centre burst and the flawless joint of mother metal for weld seam; Confirm to satisfy the needed joint geometric parameter of tensile strength that the limit stress that makes crackle generation unstable propagation in the weld seam equals mother metal according to joint geometric parameter of establishing and the stress intensity factor relation equation that contains I type centre burst weld seam, can guarantee that the weld seam that contains I type centre burst does not destroy prior to flawless mother metal.

The principle of this joint design is; Can adjust the inner ess-strain of joint by means of the joint geometry parameter designing distributes; Reduce the stress concentration degree that toe of weld carries weak area; Reduce the inner ess-strain of weld seam and distribute, and then reduce near the ess-strain the crack tip, thereby the load-bearing capacity that contains I type centre burst weld metal zone is improved; Joint design makes the carrying weak area of joint shifted to mother metal that contains crackle or flawless mother metal by the weld seam that contains centre burst to a certain extent, and the welded structure that contains centre burst can be designed according to the mother metal load-bearing capacity.

The present invention solves the problems of the technologies described above the technical scheme of taking to be:

Scheme one: the ratio that open joint method for designing according to the invention is based on the stress intensity factor in weld seam and the mother metal and joint breaking toughness matching ratio equate, reduce the toe of weld SCF and realize equivalent-load; According to bearing behavior, the weld shape of open joint is confirmed as the weld shape that adopts simple circular curve transition between reinforcement and the mother metal; Said open joint method for designing is:

Step 1, calculating joint breaking toughness matching ratio m (weld(ing) deposit fracture toughness K _IC ^wWith mother metal fracture toughness K _IC ^bRatio);

Step 2, try to achieve the stress strength factor K in mother metal district _I ^b: the situation to contain centre burst in the mother metal is given an example; At thickness of slab, mother metal district crack size, when operating load is known, bring the stress strength factor K that limited wide plate centre burst stress intensity factor formula in following formula or the arbitrary fracturing mechanics teaching material is tried to achieve the mother metal district into _I ^b

$K_I^b=\frac{t}{\sqrt{t^2-{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="HDA0000041917730000021.png"\; state="\{\{state\}\}">a</figure-callout>}}^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size;

The stress strength factor K of the weld metal zone of step 3, the equivalent-load when confirming to satisfy mother metal and weld metal zone and all having crackle _I ^w: by the equivalent-load condition

$\frac{K_I^w}{K_I^b}=\frac{K_{\mathrm{IC}}^w}{K_{\mathrm{IC}}^b}=m$

Try to achieve

Wherein, m is the joint breaking toughness matching ratio of obtaining in the step 1, K _I ^bStress intensity factor for the mother metal district that obtains in the step 2;

Step 4, obtain the K factor formula that contains I type centre burst open joint:

$K_I=\{1+(0.85038+0.84549\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.17841+0.63191\frac{h}{h+t}}}{0.3+0.6\frac{h}{t}}\left]\right\}\frac{t}{\sqrt{{(t+h)}^2-{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="HDA0000041917730000021.png"\; state="\{\{state\}\}">a</figure-callout>}}^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size;

Step 5, confirm toe of weld arc transition radius r: the size of open joint toe of weld radius r is selected bigger grinding wheel radius or toe of weld formative radius, to obtain less toe of weld SCF according to existing machinery processing or other molding condition as far as possible; Grinding wheel radius described here or toe of weld formative radius are the toe of weld radius r;

Step 6, confirm the relation of w, h: the formula of the r substitution step 4 of confirming step 5, integrating step three is confirmed K _I ^wValue, obtain the relation of w and h, i.e. w=nh;

Step 7, confirm joint reinforcement h: the w=nh substitution joint reinforcement area formula (being shown below) that the r that confirms step 5 and step 6 are confirmed, obtain the reinforcement h that satisfies the S minimum, be the h that finally meets the demands;

$S=\mathrm{wh}+(r-h)\sqrt{2\mathrm{rh}-h^2}-{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA0000041917730000021.png"\; state="\{\{state\}\}">r</figure-callout>}}^2\arccos \frac{r-h}{r}$

Step 8, confirm capping bead half-breadth w: the w=nh that the joint reinforcement h substitution step 6 of confirming step 7 is confirmed can obtain the capping bead half-breadth w of joint;

Step 9, can obtain weld seam according to reinforcement height h, toe of weld radius r, the total half-breadth w of capping bead and contain required weld shape and the geometric parameter values thereof of open joint that I type centre burst mother metal contains crackle.

Scheme two: the limit stress that weld shape method for designing according to the invention is based on crackle unstable propagation in the weld seam and the tensile strength of mother metal equate, reduce the toe of weld SCF and realizes equivalent-load; According to bearing behavior, the weld shape of open joint is confirmed as the weld shape that adopts simple circular curve transition between reinforcement and the mother metal; Said open joint method for designing is:

The tensile strength sigma of step 1, measurement base metals _b ^bAnd the fracture toughness K of weld(ing) deposit _IC ^w

Step 2, obtain the K factor formula that contains I type centre burst open joint:

$K_I=\{1+(0.85038+0.84549\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.17841+0.63191\frac{h}{h+t}}}{0.3+0.6\frac{h}{t}}\left]\right\}\frac{t}{\sqrt{{(t+h)}^2-{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="HDA0000041917730000021.png"\; state="\{\{state\}\}">a</figure-callout>}}^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size;

Step 3, confirm the condition that the joint geometric parameter of equivalent-load satisfies:, obtain the satisfied condition of geometric parameter of equivalent-load joint according to condition

half t of substitution thickness of slab that satisfies equivalent-load this moment, crackle half long a:

${\mathrm{\&sigma;}}_c^w=\frac{K_{\mathrm{Ic}}^w}{\{1+0.85(1+\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.25(1+\frac{h}{t})}}{0.35}\left]\right\}\frac{t\sqrt{\mathrm{\&pi;a}}}{\sqrt{{(t+h)}^2-a^2}}}={\mathrm{\&sigma;}}_b^b$

Step 4, confirm toe of weld arc transition radius r: the size of open joint toe of weld radius r is selected bigger grinding wheel radius or toe of weld formative radius, to obtain less toe of weld SCF according to existing machinery processing or other molding condition as far as possible; Grinding wheel radius described here or toe of weld formative radius are the toe of weld radius r;

Step 5, confirm the relation of w and h: the formula of the r substitution step 3 of confirming step 4, obtain the relation of w and h, i.e. w=nh;

Step 6, confirm joint reinforcement h: the w=nh substitution joint reinforcement area formula (being shown below) that the r that confirms step 4 and step 5 are confirmed, obtain the reinforcement h that satisfies the S minimum, be the h that finally meets the demands;

$S=\mathrm{wh}+(r-h)\sqrt{2\mathrm{rh}-h^2}-{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA0000041917730000021.png"\; state="\{\{state\}\}">r</figure-callout>}}^2\arccos \frac{r-h}{r}$

Step 7, confirm capping bead half-breadth w: the w=nh that the joint reinforcement h substitution step 5 of confirming step 6 is confirmed can obtain the capping bead half-breadth w of joint;

Step 8, can obtain weld seam according to reinforcement height h, toe of weld radius r, the total half-breadth w of capping bead and contain the I type and split required weld shape and the geometric parameter values thereof of the center flawless open joint of line mother metal.

The invention has the beneficial effects as follows:

The present invention is applicable to that the weld seam of the two-sided welding of double V groove contains the open joint of I type centre burst.The present invention does not destroy the weld seam that contains I type centre burst prior to the mother metal that contains crackle; Also can make the critical load of the weld seam that contains I type centre burst be not less than the tensile strength of flawless mother metal, the load-bearing capacity that so just can guarantee to contain the open joint of I type centre burst is not less than the load-bearing capacity of mother metal.Because there is certain arc transition in welding toe, reduce the SCF of welding toe substantially simultaneously, improve the fatigue strength of joint.The present invention can make and contain I type centre burst open joint static load load-bearing capacity and be not less than mother metal, and fatigue strength is apparently higher than the as-welded common open joint that contains crackle of the same race.Be applicable to the dull and stereotyped open joint of two-sided welding.

Concrete beneficial effect of the present invention shows the following aspects:

(1) when existing I type centre burst mother metal to contain defective in the weld seam, make crackle in the weld seam of open joint not prior to the crackle unstable propagation in the mother metal.This makes weld seam contain I type centre burst mother metal also to exist the welded structure of defective to design according to the load-bearing capacity of mother metal, and needn't consider defect influence.

(2), make the limit stress of the crackle generation unstable propagation in the weld seam of open joint be not less than the tensile strength of mother metal when there being I type centre burst in the weld seam during mother metal zero defect.This makes weld seam contain I type centre burst and the flawless welded structure of mother metal can design according to the intensity of mother metal, and needn't consider to exist in the weld seam defect influence.

(3) there is certain arc transition in welding toe, has reduced the SCF of welding toe, makes the load-bearing capacity of the welding toe that load-bearing capacity is weak improve, and with respect to common open joint, has improved the fatigue strength of joint.

(4), make equivalent-load design open joint lower than common open joint to the sensitivity of crack defect because the equivalent-load design does not destroy weld seam prior to mother metal.The more common open joint of equivalent-load design open joint is better.Engineering significance is comparatively desirable.

Description of drawings

Fig. 1 is that weld seam contains I type centre burst mother metal and also has crackle open joint synoptic diagram (1-mother metal, 2-weld seam contain I type centre burst, the crackle in the 4-mother metal in the 3-weld seam); Fig. 2 is that weld seam contains I type centre burst mother metal zero defect open joint synoptic diagram (1-mother metal, 2-weld seam contain I type centre burst in the 3-weld seam).

Embodiment

Embodiment one: referring to Fig. 1; The described I of the containing type of this embodiment centre burst open joint realizes that the open joint method for designing of equivalent-load is suitable for weld seam and contains the joint form that also there are crackle in I type centre burst and mother metal, and the ratio that said method is based on the stress intensity factor in weld seam and the mother metal and joint breaking toughness matching ratio equate, reduce as far as possible the toe of weld SCF and realize equivalent-load; According to bearing behavior, for guaranteeing the fatigue strength of joint, the weld shape of open joint is confirmed as the weld shape that adopts simple circular curve transition between reinforcement shown in Figure 1 and the mother metal; Said open joint method for designing is:

Step 1, calculating joint breaking toughness matching ratio m (weld(ing) deposit fracture toughness K _IC ^wWith mother metal fracture toughness K _IC ^bRatio).Design fracture toughness sample, the fracture toughness of test mother metal and weld(ing) deposit (wlding) obtains joint breaking toughness matching ratio;

Step 2, try to achieve the stress strength factor K in mother metal district _I ^b: the situation to contain centre burst in the mother metal is given an example; At thickness of slab, mother metal district crack size, when operating load is known, bring the stress strength factor K that limited wide plate centre burst stress intensity factor formula in following formula or the arbitrary fracturing mechanics teaching material is tried to achieve the mother metal district into _I ^b

$K_I^b=\frac{t}{\sqrt{t^2-{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="HDA0000041917730000021.png"\; state="\{\{state\}\}">a</figure-callout>}}^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size;

The stress strength factor K of the weld metal zone of step 3, the equivalent-load when confirming to satisfy mother metal and weld metal zone and all having crackle _I ^w: by the equivalent-load condition

$\frac{K_I^w}{K_I^b}=\frac{K_{\mathrm{IC}}^w}{K_{\mathrm{IC}}^b}=m$

Try to achieve

$K_I^w=m{K}_I^b$

Wherein, m is the joint breaking toughness matching ratio of obtaining in the step 1, K _I ^bStress intensity factor for the mother metal district that obtains in the step 2;

Step 4, obtain the K factor formula that contains I type centre burst (the certain reinforcement of band as shown in Figure 2) open joint:

$K_I=\{1+(0.85038+0.84549\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.17841+0.63191\frac{h}{h+t}}}{0.3+0.6\frac{h}{t}}\left]\right\}\frac{t}{\sqrt{{(t+h)}^2-a^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size;

Step 5, confirm toe of weld arc transition radius r: the size of open joint toe of weld radius r is selected bigger grinding wheel radius or toe of weld formative radius, to obtain less toe of weld SCF according to existing machinery processing or other molding condition as far as possible; Grinding wheel radius described here or toe of weld formative radius are the toe of weld radius r;

Step 6, confirm the relation of w, h: the formula of the r substitution step 4 of confirming step 5, integrating step three is confirmed K _I ^wValue, obtain the relation of w and h, i.e. w=nh;

Step 7, confirm joint reinforcement h: the w=nh substitution joint reinforcement area formula (being shown below) that the r that confirms step 5 and step 6 are confirmed, obtain the reinforcement h that satisfies the S minimum, be the h that finally meets the demands;

$S=\mathrm{wh}+(r-h)\sqrt{2\mathrm{rh}-h^2}-{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA0000041917730000021.png"\; state="\{\{state\}\}">r</figure-callout>}}^2\arccos \frac{r-h}{r}$

Step 8, confirm capping bead half-breadth w: the w=nh that the joint reinforcement h substitution step 6 of confirming step 7 is confirmed can obtain the capping bead half-breadth w of joint;

Step 9, can obtain weld seam according to reinforcement height h, toe of weld radius r, the total half-breadth w of capping bead and contain required weld shape and the geometric parameter values thereof of open joint that I type centre burst mother metal contains crackle.

According to bearing behavior; When the open joint weld seam contains I type centre burst simultaneously also there is crackle in mother metal; Can meet the demands by embodiment one said weld shape method for designing; The weld shape of the open joint that the said method of this embodiment of usefulness obtains is a shape as shown in Figure 1, wherein, adopts simple circular curve transition between reinforcement and the mother metal.The toe of weld radius r of open joint can add condition according to existing machine, and perhaps other molding condition is definite, selects bigger radius, to obtain less toe of weld SCF as far as possible.Embodiment one said weld shape method for designing is applied under the horizontal loading environment, and suitable weld seam contains the geometrical parameter design of the equivalent-load open joint that has crackle (like Fig. 1) in I type centre burst and the mother metal.

Embodiment two: referring to Fig. 2; The described I of the containing type of this embodiment centre burst open joint realizes that the open joint method for designing of equivalent-load is suitable for weld seam and contains the flawless joint form of I type centre burst mother metal, and the limit stress that said method is based on crackle unstable propagation in the weld seam equates with the tensile strength of mother metal, the toe of weld SCF minimizes and realizes equivalent-load; According to bearing behavior, for guaranteeing the fatigue strength of joint, the weld shape of open joint is confirmed as the weld shape that adopts simple circular curve transition between reinforcement shown in Figure 2 and the mother metal; Said open joint method for designing is:

The tensile strength sigma of step 1, measurement base metals _b ^bAnd the fracture toughness K of weld(ing) deposit _IC ^wDesign fracture toughness sample, the fracture toughness of test weld(ing) deposit (wlding).Layout board shape tensile sample, the tensile property of test mother metal is got the mean value of three samples, obtains the tensile strength of mother metal.

Step 2, obtain the K factor formula that contains I type centre burst (the certain reinforcement of band as shown in Figure 2) open joint:

$K_I=\{1+(0.85038+0.84549\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.17841+0.63191\frac{h}{h+t}}}{0.3+0.6\frac{h}{t}}\left]\right\}\frac{t}{\sqrt{{(t+h)}^2-a^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size.

Step 3, confirm the condition that the joint geometric parameter of equivalent-load satisfies:, obtain the satisfied condition of geometric parameter of equivalent-load joint according to condition

half t of substitution thickness of slab that satisfies equivalent-load this moment, crackle half long a;

${\mathrm{\&sigma;}}_c^w=\frac{K_{\mathrm{Ic}}^w}{\{1+0.85(1+\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.25(1+\frac{h}{t})}}{0.35+0.6\frac{h}{t}}\left]\right\}\frac{t\sqrt{\mathrm{\&pi;a}}}{\sqrt{{(t+h)}^2-a^2}}}={\mathrm{\&sigma;}}_b^b$

Step 4, confirm toe of weld arc transition radius r: the size of open joint toe of weld radius r is selected bigger grinding wheel radius or toe of weld formative radius, to obtain less toe of weld SCF according to existing machinery processing or other molding condition as far as possible; Grinding wheel radius described here or toe of weld formative radius are the toe of weld radius r;

Step 5, confirm the relation of w and h: the formula of the r substitution step 3 of confirming step 4, obtain the relation of w and h, i.e. w=nh;

Step 6, confirm joint reinforcement h: the w=nh substitution joint reinforcement area formula (being shown below) that the r that confirms step 4 and step 5 are confirmed, obtain the reinforcement h that satisfies the S minimum, be the h that finally meets the demands;

$S=\mathrm{wh}+(r-h)\sqrt{2\mathrm{rh}-h^2}-{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA0000041917730000021.png"\; state="\{\{state\}\}">r</figure-callout>}}^2\arccos \frac{r-h}{r}$

Step 7, confirm capping bead half-breadth w: the w=nh that the joint reinforcement h substitution step 5 of confirming step 6 is confirmed can obtain the capping bead half-breadth w of joint;

Step 8, can obtain weld seam according to reinforcement height h, toe of weld radius r, the total half-breadth w of capping bead and contain required weld shape and the geometric parameter values thereof of the flawless open joint of I type centre burst mother metal.

According to bearing behavior; When the open joint weld seam contains I type centre burst and during the mother metal zero defect; Stating the weld shape method for designing by embodiment two can meet the demands; The weld shape of the open joint that the said method of this embodiment of usefulness obtains is a shape as shown in Figure 2, wherein, adopts simple circular curve transition between reinforcement and the mother metal.The toe of weld radius r of open joint can add condition according to existing machine, and perhaps other molding condition is definite, selects bigger radius, to obtain less toe of weld SCF as far as possible.Embodiment two said weld shape methods for designing are applied under the horizontal loading environment, and suitable weld seam contains I type centre burst and the geometrical parameter design of the equivalent-load open joint of mother metal zero defect (like Fig. 2).

Embodiment three: referring to Fig. 1, the crackle in the said method of this embodiment in the mother metal can be arranged in any position that the crackle of butt welded seam does not exert an influence, and the crackle in the mother metal is positioned at outside the capping bead width.Other composition and annexation are identical with embodiment one.

Realize the prerequisite of the object of the invention: to the dull and stereotyped open joint of two-sided welding, on the basis of normal weld upwards with the both sides built-up welding enough highly and the welding bead of width.Machine work perhaps obtains the weld shape and the joint geometric parameter values thereof of equivalent-load open joint through other shaping means.Guarantee that the reinforcement upper surface can not polish yet under the situation of reinforcement height design load.To the exigent welded structure of fatigue behaviour; At first reinforcement is taked to scabble processing; Satisfying on the basis of weld width processing toe of weld radius then, the toe of weld radius adds that machine that the polishing direction of milling in man-hour or emery wheel should make the toe zone produce compression as far as possible adds stress and the machine of avoiding producing stretching adds stress.All machines add the cut that process all should be avoided parallel fusion length direction, and the face of weld roughness should reach more than 3.2.Method for designing according to the invention and parameters of formula are applicable to, the dull and stereotyped open joint of two-sided welding, are not suitable for the dull and stereotyped open joint of one-sided welding.

Embodiment (combining Fig. 1 and Fig. 2):

One, layout board shape tensile sample, the tensile property of test mother metal and weld(ing) deposit is got the mean value of three samples, obtains the tensile strength of mother metal and weld(ing) deposit.Design the fracture toughness sample, test the fracture toughness of mother metal and weld(ing) deposit, obtain the fracture toughness matching ratio of joint.

Two,, select corresponding weld shape design proposal respectively according to the situation that whether contains crackle in the mother metal; According to the fracture toughness matching ratio of thickness of slab and joint or the tensile strength of mother metal, the open joint of confirming according to the design procedure of embodiment one or embodiment two to make weld seam contain I type centre burst is according to the weld seam geometric parameter values of equivalent-load design.

Three, welding open joint.

Four, machine work perhaps adopts other shaping means to obtain the weld shape and the joint geometric parameter values thereof of equivalent-load open joint.Guarantee that the reinforcement upper surface can not polish yet under the situation of reinforcement height design load.To the exigent welded structure of fatigue behaviour; At first reinforcement is taked to scabble processing; Satisfying on the basis of weld width processing toe of weld radius then, the toe of weld radius adds that machine that the polishing direction of milling in man-hour or emery wheel should make the toe zone produce compression as far as possible adds stress and the machine of avoiding producing stretching adds stress.All machines add the cut that process all should be avoided parallel fusion length direction, and the face of weld roughness should reach more than 3.2.

Claims (3)

1. one kind contains the open joint method for designing that I type centre burst open joint is realized equivalent-load, and said method is suitable for weld seam and contains the joint form that also there are crackle in I type centre burst and mother metal; It is characterized in that: the ratio that said open joint method for designing is based on the stress intensity factor in weld seam and the mother metal and joint breaking toughness matching ratio equate, reduce the toe of weld SCF and realize equivalent-load; According to bearing behavior, the weld shape of open joint is confirmed as the weld shape that adopts simple circular curve transition between reinforcement and the mother metal; Said open joint method for designing is:

Step 1, calculating joint breaking toughness matching ratio m, joint breaking toughness matching ratio m is weld(ing) deposit fracture toughness K _IC ^wWith mother metal fracture toughness K _IC ^bRatio;

Step 2, try to achieve the stress strength factor K in mother metal district _I ^b: at thickness of slab, mother metal district crack size, when operating load is known, bring the stress strength factor K that following formula is tried to achieve the mother metal district into _I ^b

$K_I^b=\frac{t}{\sqrt{t^2-a^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size;

The stress strength factor K of the weld metal zone of step 3, the equivalent-load when confirming to satisfy mother metal and weld metal zone and all having crackle _I ^w: by the equivalent-load condition

$\frac{K_I^w}{K_I^b}=\frac{K_{\mathrm{IC}}^w}{K_{\mathrm{IC}}^b}=m$

Try to achieve

$K_I^w=m{K}_I^b$

Wherein, m is the joint breaking toughness matching ratio of obtaining in the step 1, K _I ^bStress intensity factor for the mother metal district that obtains in the step 2;

Step 4, obtain the stress intensity factor formula that contains I type centre burst open joint:

$K_I=\{1+(0.85038+0.84549\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.17841+0.63191\frac{h}{h+t}}}{0.3+0.6\frac{h}{t}}\left]\right\}\frac{t}{\sqrt{{(t+h)}^2-a^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size, and h is the joint reinforcement, and r is the toe of weld radius, and w is the capping bead half-breadth;

Step 5, confirm open joint toe of weld radius r: the size of open joint toe of weld radius r is processed according to existing machinery, selects bigger grinding wheel radius or toe of weld formative radius, to obtain less toe of weld SCF; Grinding wheel radius described here or toe of weld formative radius are the toe of weld radius r;

Step 6, confirm the relation of w, h: the formula of the r substitution step 4 of confirming step 5, the K that integrating step three is confirmed _I ^wValue, obtain the relation of w and h, i.e. w=nh;

Step 7, confirm joint reinforcement h: the w=nh substitution joint reinforcement area formula that the r that confirms step 5 and step 6 are confirmed, obtain the reinforcement h that satisfies the S minimum, be the h that finally meets the demands;

$S=\mathrm{wh}+(r-h)\sqrt{2\mathrm{rh}-h^2}-r^2\arccos \frac{r-h}{r}$

Step 8, confirm capping bead half-breadth w: the w=nh that the joint reinforcement h substitution step 6 of confirming step 7 is confirmed can obtain the capping bead half-breadth w of joint;

Step 9, can obtain weld seam according to joint reinforcement h, toe of weld radius r, capping bead half-breadth w and contain required weld shape and the geometric parameter values thereof of open joint that I type centre burst mother metal contains crackle.

2. the open joint method for designing that contains I type centre burst open joint realization equivalent-load according to claim 1; It is characterized in that: the crackle in the said method in the mother metal can be arranged in any position that the crackle of butt welded seam does not exert an influence, and the crackle in the mother metal is positioned at outside the capping bead width.

3. one kind contains the open joint method for designing that I type centre burst open joint is realized equivalent-load, and said method is suitable for weld seam and contains the flawless joint form of I type centre burst mother metal; It is characterized in that: the limit stress that said open joint method for designing is based on crackle unstable propagation in the weld seam and the tensile strength of mother metal equate, reduce the toe of weld SCF and realizes equivalent-load; According to bearing behavior, the weld shape of open joint is confirmed as the weld shape that adopts simple circular curve transition between reinforcement and the mother metal; Said open joint method for designing is:

The tensile strength sigma of step 1, measurement base metals _b ^bAnd the fracture toughness K of weld(ing) deposit _IC ^w

Step 2, obtain the stress intensity factor formula that contains I type centre burst open joint:

$K_I=\{1+(0.85038+0.84549\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.17841+0.63191\frac{h}{h+t}}}{0.3+0.6\frac{h}{t}}\left]\right\}\frac{t}{\sqrt{{(t+h)}^2-a^2}}\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$

In the formula, t is that thickness of slab is half the, σ is that plus load, a are the half the of centre burst size, and h is the joint reinforcement, and r is the toe of weld radius, and w is the capping bead half-breadth;

Step 3, confirm the condition that the joint geometric parameter of equivalent-load satisfies:, obtain the satisfied condition of geometric parameter of equivalent-load joint according to condition

half t of substitution thickness of slab that satisfies equivalent-load this moment, crackle half long a:

${\mathrm{\&sigma;}}_c^w=\frac{K_{\mathrm{Ic}}^w}{\{1+0.85(1+\frac{h}{h+t})\exp [-\frac{{\left(\frac{w-\sqrt{h(2r-h)}}{t+h}\right)}^{0.25(1+\frac{h}{t})}}{0.35}\left]\right\}\frac{t\sqrt{\mathrm{\&pi;a}}}{\sqrt{{(t+h)}^2-a^2}}}={\mathrm{\&sigma;}}_b^b$

Step 4, confirm open joint toe of weld radius r: the size of open joint toe of weld radius r is processed according to existing machinery, selects bigger grinding wheel radius or toe of weld formative radius, to obtain less toe of weld SCF; Grinding wheel radius described here or toe of weld formative radius are the toe of weld radius r;

Step 5, confirm the relation of w and h: the formula of the r substitution step 3 of confirming step 4, obtain the relation of w and h, i.e. w=nh;

Step 6, confirm joint reinforcement h: the w=nh substitution joint reinforcement area formula that the r that confirms step 4 and step 5 are confirmed, obtain the reinforcement h that satisfies the S minimum, be the h that finally meets the demands;

$S=\mathrm{wh}+(r-h)\sqrt{2\mathrm{rh}-h^2}{-r}^2\arccos \frac{r-h}{r}$

Step 7, confirm capping bead half-breadth w: the w=nh that the joint reinforcement h substitution step 5 of confirming step 6 is confirmed can obtain the capping bead half-breadth w of joint;

Step 8, can obtain weld seam according to joint reinforcement h, toe of weld radius r, capping bead half-breadth w and contain the I type and split required weld shape and the geometric parameter values thereof of the center flawless open joint of line mother metal.

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