Rise solder the research progress of contact exhaustion function and latest technology

1 solder fatigue problem Normal Align=left> since invention of welding rod of medicine of the besmear at the beginning of 20 centuries up to now centenary come, solder to had made the technique with most wide application, find out another kind of development very hard such fast, using dimensions and diversification field can with the craft that solders to be compared, so that a lot of the most serious technology problems must be used now,solder to just can be solved, for example: Shipbuilding, railroad, car, aviation, spaceflight, bridge, boiler, large workshop and high-level building cannot leave to solder technical support. If solder to was not invented, a lot of structures are simple even say whole industry is to won't arise. Beyond question, go up in project production at present, soldering is the mainest join method, solder the 50% above that structural weight already held steely total output, this one scale of industrial developed country is already adjacent 70% . Solder however the structure often happens ceaselessly rupture accident, among them 90% for fatigue invalidation. Normal Align=left> exhaustion destroys a kind of when be considered as shipping and marine engineering construction all the time main destruction form, from steel qualitative seagoing vessel is born up to now, of because the structure is medium fatigue crackle generate, patulous, the example that brings about shipping to destroy finally has a story repeatedly. Committee of structure of shipping of United States Coast Guard (Ship Structure Committee, u.

S.

Coast Guard) ever organized force to reached detail of six structures in 9 warships to undertake investigation and study and statistic are analysed to 77 of 6 kinds of different types civil shipping, the result makes clear, the destruction that has about 1/9 and exhaustion are concerned. A few grave accident of marine platform on the history, the Sedco that if Japan was the United States 1965,builds go partly type platform is delivering the goods the damaged in road is sunken, cause 13 people death; 1980 Alexan, DerKeyland date goes partly type platform breaks up in the North sea heavy, make be buried of more than 100 people marine, the result that investigates an analysis makes clear, structural exhaustion is one of main reasons that cause an accident. Normal > is same, fatigue invalidation happens often also on the conduit of railroad highway bridge and power station. In 559 time, european road network gets high speed develops, use mostly at that time solder the technology builds steel bridge, because know inadequacy to highway bridge exhaustion in those days, undertake fighting fatigue design without the regulation in the standard, appeared a lot of designs solder inconsequently contact, today increasingly busy with aggravating traffic carriage load falls, accelerated exhaustion to injure a process, a lot of soldering steel bridge appeared fatigue crackle. Normal > solders in our country structure the project example of because of fatigue problem invalidation also appears ceaselessly, for example, 90 time end, the fatigue fracture of contact solders in bogie of high speed passenger car, and the fatigue fracture of ministry of root of hydraulic turbine lamina, caused huge pecuniary loss to country and enterprise. Normal >1.

2 solder the reason Normal > solders the reason of structural exhaustion invalidation basically has the following sides: ① is objective on tell, solder the Jing Zaicheng of contact gets ability general not under mother capable person; And bear when delivering fluctuant load, its bear ability is far however under mother capable person, and with solder contact type and solder configuration has close relationship. This is to because solder,cause a few structures a of the fatigue and premature invalidation of contact main factor; ② solders inchoately structural design spends a design to give priority to with Jing Zaijiang, fight fatigue design without the consideration, perhaps solder standard of structural exhaustion design is not perfect, so that appeared a lot of look now the design solders inconsequently contact; Personnel of technology of ③ engineering design is right solder structural fatigue resistance can characteristic understanding is insufficient, what design solder the fatigue design criterion that the structure often copies other metal structure and configuration; ④ solders the structure is increasingly extensive, and quantify the low cost that seeks a structure blindly artificially in design and making a process, gently, bring about solder design load of the structure is bigger and bigger; ⑤ solders the tendency that the structure has direction of burden of past high speed to develop, to soldering the structure bears dynamic the demand of ability is higher and higher, and to soldering the scientific research standard of respect of structural exhaustion intensity is relative lag. Normal >1.

3 rise solder the research meaning Normal > fatigue accident happened often on certain level to restrict solder farther wide application of the structure, make a few circumstances must abandon using solder structure, suspect even solder structure whether apply to bear dynamic project is actual, solder so of the structure fight fatigue problem to cause concern expert and project technology personnel domestic and internationally, especially the widespread attention of committee of major of exhaustion of international Institute of Welding. On the foundation of a large number of fatigue experiments and project practice, solder the structure fights exhaustion to design a standard to come on stage ceaselessly, the circular to load that the steel bridge that if British bridge exhaustion designs the exhaustion of association of steel structure of normative BS5400, Europe,designs standard, Japan designs railroad bridge of standard, United States and freeway to design Institute of Welding of standard, international solders the exhaustion of steel structure designs normative IIW.

The steel structure of DOC-639-8l and our country designs normative GB-17-88. Main shipbuilding and each marine resource develop the world country, be built in the design of shipping and marine engineering construction and examine to soldering into class standard fatigue intensity of the structure made regulation and demand. Normal > solders the action of concentration of the weld defects that contact solder foot is in, stress and leftover tensile stress, the fatigue intensity that its exhaustion intensity belongs to substantially under basic gold. Solder so fatigue intensity of the structure depends on the fatigue function of contact, solder namely the fatigue resistance of contact can, concerning to solder structure whether safety is used. Solder to assure accordingly structural dependability, bear in the design hand in those who become dynamic to carry on one's shoulder or back to solder when the structure, design standard stipulates with soldering the fatigue intensity of contact regards whole as fatigue intensity of the structure, and the fatigue strength that does not use basic metal, apparent this creates great waste. Even so, in contact place local stress centers action to fall, still can produce the premature and fatigue invalidation of integral structure. To make solder the structure satisfies what put forward to its on the project to bear to ask dynamicly well, the step that can take basically has at 2 o'clock. On one hand, increase to soldering structural fatigue resistance can understanding, elaborate design configuration reachs contact form, make what design solder the construction is more reasonable, have higher fatigue strength; Rise to solder with strict control at the same time quality, prevent and reduce the generation of weld defects; On the other hand, face directly solder the weakness with contact exhaustion poorer performance, soldering in structural production process, after finishing and significant craft step is taken in use process, increase the fatigue strength of contact, increase its to bear dynamic ability, prolong its service life. Normal > solders because of this rises and be being improved contact exhaustion intensity has huge potential economic benefits and social benefit, come for a long time, it is the heat task that studies domestic and internationally about the expert. Normal >2 influence solders the main factor Normal >2.

1 Jing Zaijiang is spent to soldering the influence of structural exhaustion intensity is in the research of steely material, people always hopes material is had taller than intensity, assume greater laden weight namely with lighter oneself weight, because the structure of identical weight can have huge carrying capacity; Or it is the weight that same carrying capacity can reduce oneself. So excel in steel emerge as the times require, also have higher fatigue strength, the fatigue intensity of basic metal always increases as what Jing Zaijiang spends and rise. Normal > but to soldering for the structure, the situation is different, the constituent performance that because solder,static strength of the fatigue intensity of contact and quiet intensity of mother capable person, welding line metal, heat affects an area and strength of welding line metal match to did not concern how oldly, should solder only that is to say the detail of contact is same, the fatigue intensity of excel in steel and mild steel is same, have same S-N curve, this rule suits butt joint connect, horn to receive contact and solder all sorts of contact type such as bridge. Maddox studied yield point is in 386, the carbolic manganese steel between 636MPa and the welding line metal that use solder with 6 kinds of welding rod and the fatigue crackle that heat up influence area are patulous circumstance, the result makes clear: The mechanical function of material expands to crackle rate has certain effect, but the impact is not big. Bear in the design hand in change of load solder when the structure, try to pass choose relatively the steel of high strenth is planted will satisfy a project to need is no point. Be more than in stress comparing only + 0.

Below the circumstance of 5, when the main effect since quiet intensity condition, solder contact mother capable person just should use excel in steel. Normal > causes afore-mentioned results is line existence has similar those who bite an edge is slaggy wedge piece blemish, its ply is in 0.

075mm-0.

5mm, most advanced half classics is less than 0.

015mm. This acuteness blemish is the place that fatigue crackle begins, be equivalent to fatigue crackle forming level, the fatigue life that consequently contact leaves in particular stress amplitude, basically decide by the patulous phase of fatigue crackle. The occurrence of these blemish makes the same kind of all rolled steel solders contact has similar fatigue strength, and reach with mother capable person solder the quiet intensity concern of material is not big. Normal >2.

2 stress center the influence Normal >2.

2.

The influence Normal > solders the form of contact basically has: To receiving connect of contact, form of cruciform joint, T and lap joint, because pass line of force to be disturbed,accepting head position, produce stress to center a phenomenon consequently. Normal > butt joint is lesser, consequently stress centers coefficient lesser, its exhaustion intensity also prep above other connect form. But the experiment makes clear, the fatigue intensity of butt joint connect changes inside very big range, because a series of elements affect the cause of the fatigue function of butt joint connect,this is. Form of the dimension that is like sample, groove, solder type of method, welding rod, solder the heat treatment after the welding line treatment after appearance of the position, welding line, solder, solder all can be opposite its produce an effect. Have permanent model the serious to receiving contact to be formed as a result of bolster plate place stress concentration of bolster plate, reduced the fatigue intensity of contact. The fatigue crackle of this kind of connect all is in generation from the joint of welding line and bolster plate, is not to be in solder foot place to arise, its exhaustion intensity, kind with what do not carry bolster plate least of all the fatigue intensity of the butt joint connect of beautiful appearance is equal. Normal > cruciform joint or T form connect are soldering wide application received in the structure. Plant in this bear in force connect, because transfer to basic metal in welding line,be in have apparent sectional change, the stress that its stress centers coefficient to want to compare butt joint connect centers coefficient tall, accordingly the fatigue intensity of cross or T form connect wants under butt joint connect. A shows welding line with frit of ministry of standoff of connect of fillet weld connective groove connect to opening groove, when welding line delivers working stress, its fatigue fracture may happen on two weak point, namely basic metal and welding line foot carry boundary or welding line. Appear to opening groove solder cruciform joint, rupture to happen in solder foot place only commonly, is not to be in welding line place. Welding line does not bear the fatigue intensity of the T form of working stress and cruciform joint basically depends on welding line and the stress concentration that basically suffer force board boundary, t form connect has higher fatigue strength, and the fatigue intensity of cruciform joint is inferior. The basic measure that increases T form or strength of cruciform joint exhaustion is to open groove to solder, machine welding line to transfer be in made round glide to cross, improve measure through this kind, fatigue intensity can have relatively substantially rise. Normal > lap joint is very low, because line of force got,this is serious twist. Use alleged " strengthen " the butt joint connect of cover board is extremely unreasonable, because increased stress to focus an effect, after using cover board, the butt joint connect with fatigue before higher intensity was weakened by big earth. To bear connect of force cover board, fatigue crackle can happen in mother capable person, also can happen in welding line, change the length of the width of cover board or welding line additionally, also can change stress to distributing mediumly in basic metal, because this will affect the fatigue intensity of contact, namely the addition as welding line length and rate of cover board width, the fatigue intensity of contact increases, because stress distributings in basic metal,this is tend even be caused by. Normal >2.

2.

The influence Normal > is why to be planted contact form, they are by connective of two kinds of welding line, butt joint welding line and fillet weld. Welding line figure is different, its stress centers coefficient not identical also, thereby fatigue intensity has bigger dispersive sex. The figure of butt joint welding line is the greatest to the fatigue strength effect of contact. Normal > (1) transfers the person such as influence Yamaguchi of horn built exhaustion horn transfers between intensity and basic metal and welding line metal (outside obtuse angle) relation. Width of welding line of the W(in the experiment) with H(height) change, but H/W ratio keeps constant. This means included angle to keep changeless, test result makes clear, fatigue intensity also keeps changeless. But if W keeps changeless, metabolic parameter H, discover H increases, contact exhaustion intensity is reduced, this is apparently outside the result that included angle reduces. Normal > (2) welding line shows welding line radius blend is same as a result fatigue to contact intensity has main effect, namely radius blend increases (transfer horn maintains changeless) , fatigue intensity increases. The appearance of fillet weld also has bigger effect to the fatigue intensity of contact. Normal LINE-HEIGHT: 18pt">2.

2.

The influence Normal > solder foot has the drawback of a large number of different types, the blemish of these different types brings about fatigue crackle inchoate craze and make the fatigue intensity of mother capable person drops quickly (drop 80% ) . Weld defects substantially can divide two kinds: Face shape blemish (wait like crackle, incomplete fusion) with bulk blemish (stomatic, slag inclusion) , their influence rate disregards, at the same time the sort of the influence of intensity of exhaustion of head of weld defects butt joint and blemish, direction is mixed the position is concerned. Normal > 1) crackle solders medium crackle, be like cold, hot crack, outside having the constituent structure that has brittleness except companion, it is serious stress concentration source, it can reduce the fatigue intensity of structure or connect substantially. Inchoate research oneself make clear, be in wide 60mm, thick 12.

In the sample of connect of mild steel butt joint of 7mm, have in welding line long 25mm, deep 5.

When the crackle of 2mm (the 10%) that they occupy sample cross section to accumulate about, handing in change below load condition, its the fatigue intensity of 106 cycling life reduced 2 × about 55%~65% . Normal > 2) not solder ought to explain fully, not certain not solder all considers as blemish fully, because ask certain connect is appeared for week ministry solder artificially sometimes, typical case is the design that certain pressure vessel take-overs. Not solder appears blemish to be exterior blemish sometimes (bosseyed welding line) , it is in-house blemish sometimes () of double-faced welding line, it can be local property, also can be integral property. Its basically are affected sufficient weaken cut area and cause stress to center. In order to weaken an area the 10% fatigue life when and the test result photograph that did not contain this kinds of drawback are compared, its exhaustion intensity was reduced 25% , this means its the effect is not as serious as crackle. Normal > 3) incomplete fusion because sample hard preparation, concern research up to now extremely exiguous. But apodeictic, incomplete fusion attributes planar flaw, not allow to ignore consequently, mix its commonly not solder is equal fully treat. Normal > 4) bites edge token to bite an edge has L of length gnawing an edge, depth gnawing an edge W of H, width gnawing an edge. The main parameter that affects fatigue intensity is H of deepness gnawing an edge, h of current and usable deepness or deepness and board thick ratio (H/B) regards parameter assess connect as fatigue intensity. Normal >5) stoma is bulk blemish, harrison undertook analytic summing up to the concerned test result of forefathers, because air hole reduced cut area size to cause,fatigue intensity drops basically is, there is proper line sexual relationship between them. But a few research make clear, should use machine treatment method to machine sample surface, make air hole is in apparently when, or when just be located in exterior lower part, stomatic adverse effect is increased, it will center a source to act well as stress, and those who become fatigue crackle case crack a dot. The position with this stomatic specification compares his impact of intensity of exhaustion of head of dimension butt joint is bigger, the stoma below the surface or surface layer has the most adverse effect. Normal > 6) slag inclusion: As bulk blemish, strength effect wants exhaustion of head of butt joint of stoma of slag inclusion comparing big. Normal > sees the effect of intensity of exhaustion of head of weld defects butt joint through afore-mentioned introductions, not only concern with blemish dimension, and dawn still decides at a lot of other factors, affect than in-house blemish like exterior blemish big, what compare other direction with the influence of the face shape blemish with active force perpendicular direction is big; The influence that is located in remains to pull the blemish inside stress area is more leftover than be in those who control stress area is big; The blemish that is located in stress to center an area (be like crackle of welding line toe) same defect impact is big in field of evener than be in stress. Normal >2.

3 solder the leftover stress influence to fatigue intensity Normal > solders leftover stress is to solder the characteristic with structural peculiar place, accordingly, it to soldering the influence of structural exhaustion intensity is people wide the problem that is a care, undertook for this people many experiment considers to work. The experiment often is used have solder the sample of leftover stress and the sample after eliminating leftover stress through heat treatment, undertake fatigue experiment oppose is compared. Because solder,the generation of leftover stress often is being accompanied solder the material function that hot loop causes varies, and heat treatment is in eliminate leftover stress while the property that also restore or rehabilitated material partly, at the same time also the dispersive sex as a result of test result, because this pair experimented to produce different explanation as a result, the influence of leftover to soldering stress also had different opinion. Normal > tries lift inchoate the research job that with the near future place of a few people has is exemple, can show this one issue clearly, the 2 × that undertake to having butt joint contact of Yu Gao experiment 106 times circularly result, different investigator reached different conclusion. Somebody discovers: The fatigue intensity of samer than as welded sample increases the fatigue strength that heat treatment eliminates stress sample 12.

5% ; Additional somebody discovers the fatigue intensity of the sample of as welded and heat treatment is consistent, namely difference is not big; But also although have,somebody discovers intensity of the exhaustion after using heat treatment to eliminate leftover stress increase, but raise a cost far under 12.

5% etc. To the sample of butt joint connect of exterior burnish test result also is such, namely some experiments think, fatigue strength can increase after heat treatment 17% , but also some test results explain, fatigue intensity did not rise after heat treatment etc. This issue makes person bewilderment indissolubles for a long time, until before a few scholars are handing in Russia change a series of tests had below load, just settled this one issue gradually. Normal > is worth to put forward most among them is Trufyakov the research that effect of strength of exhaustion of head of leftover stress butt joint solders below feature of loop of different to be in stress. The experiment uses 14Mn2 steel of structure of common low alloy, there is welding line of a transverse butt joint on sample, and in v of two sides of positive and negative fore-and-aft solder each one. One group sample undertook elimination the heat treatment of leftover stress after solder, another group without heat treatment. Experiment of fatigue intensity contrast uses R=-1 of coefficient of feature of loop of 3 kinds of stress, 0, + 0.

3. Handing in change below load (R=-1) , the fatigue intensity that eliminates leftover stress sample is close to 130MPa, and without eliminating leftover stress it is 75MPa only, fall in pulsatile load (R=0) , the fatigue intensity of two groups of sample is same, all be 185MPa. And when R=0.

3 when, the sample exhaustion intensity that eliminates leftover stress via heat treatment is 260MPa, instead slightly under not the sample of heat treatment (270MPa) . The main reason that produces this phenomenon is: It is when R cost is higher, fall in pulsatile load for example (R=0) , fatigue intensity is higher, in taller pull down stress effect, leftover stress gets quickly releasing, because this is leftover the stress influence to fatigue intensity is abate; Increase when R 0.

3 when, leftover stress falls in load action, reduce further, already did not act well to fatigue intensity actually. And heat treatment is in eliminate leftover stress while bate material is qualitative, make consequently fatigue intensity drops instead after heat treatment. This one experiment showed remains very quite stress and solder the effect that hot loop place causes material qualitative change to change pair of fatigue intensity. Also can see from here solder the stress loop character of the influence of intensity of exhaustion of head of leftover stress butt joint and fatigue load is concerned. It is namely when circular character value is inferior, the impact is bigger. Normal > oneself point out, because be put in structural welding line,have the leftover stress that reachs material yield point, because this is in constant bring to bear on in the connect of stress loop action, place susceptive is actual near welding line stress will be circularly swing downward by the yield point of material, and no matter its are primitive the circular feature of action how. For example nominal stress is circularly + S1 arrives - S2, criterion its stress limits should be S1+S2. But the limits of real stress loop in contact will be by the stress of Sy(yield point) to Sy-(S1+S2) . This solder in research is very important when contact exhaustion intensity, it brought about standard of a few designs to replace circular feature R with stress limits. Normal > in addition, in experiment process, means of the dimension size of test specimen, to load, stress is compared circularly, load chart is right also fatigue intensity has very big effect. Normal >3 improvement solders the technique Normal > solders contact exhaustion crackle is opened commonly crack positional consist in solder root and solder foot two place, if the fatigue crackle of solder root place opens cracked danger to be restrained, solder the critical point of contact is centered at solder foot place. A lot of methods can be used at rising to solder the fatigue intensity of contact, ① decreases or eliminate solder be short of owe start to talk especially blemish; ② improves the geometrical appearance of solder foot place to reduce stress to center coefficient; ③ adjustment solders leftover stress field, generation remains compresses stress field. It is OK that these improve a method cent is two kinds big, if express,1 is shown. Solder the process optimizes a method is to be aimed at not only rise solder structural exhaustion intensity and consideration, to soldering at the same time structural Jing Zaijiang is spent, solder each respect such as the metallurgy function of contact has huge profit, the material of this respect is very much in this not much give uncecessary details. Normal Align=center> expresses 1 solder the improvement of structural exhaustion intensity methodological Normal Align=center>normal > the main method of contact exhaustion intensity. Normal >3.

Appearance of geometry of foot of 1 improvement solder reduces the methodological Normal >3.

1.

1TIG frit repairs Normal > all makes clear, TIG frit is repaired can rise substantially solder the fatigue intensity of contact, this kind of method is to use method of solder of arc of tungsten pole argon soldering the transition of contact place remelting, make smooth glide is formed to cross between welding line and basic metal. Reduced stress concentration, also reduced the content of tiny metalloid slag inclusion of this place at the same time, make the fatigue intensity of contact place rises consequently. Normal > frit repairs craft to ask welding torch is located in place of the foot that be apart from solder commonly 0.

5~1.

5mm place, should hold remelting position clean, if match beforehand with slight burnish effect much better. Important is when extinguish arc happening in remelting, if why handle the method that has arc afresh, because this certainly will affects the quality that remelting solder, recommending the best place that has arc afresh commonly is in front of of hole of solder path arc 6mm is in, of a few countries of Europe of organization of Institute of Welding of the closest international and Japan a few solder institute, use unified solder by England the sample of institute preparation undertook, some the oneness research that improves effectiveness of method of contact exhaustion intensity, the nominal and fatigue intensity that confirms via the 2 × of this connect after this method is handled 106 loops fall rises 58% , if the fatigue intensity gotten 211MPa is nominal,value conversion becomes corresponding eigenvalue (K index) for 144MPa. The highest FAT in the intensity of contact detail exhaustion that solder of international of its oneself tower above learns is worth. Normal >3.

1.

2 machining Normal > undertakes machining to welding line surface, stress centers degree to will decrease greatly, the fatigue intensity of butt joint connect also rises accordingly, when welding line when nonexistent blemish, the fatigue intensity of contact but the fatigue intensity that capital of prep above radical belongs to. But the cost of machining of this kind of surface is very high, mix benignantly truly only accordingly the place that can machine really, just machine at using this to plant aptly. And contain serious flaw and need not the welding line of bottom solder, many the stress concentration that its blemish is in or stress of ministry of welding line root wants to compare welding line face centrally is serious, the machining that leaves welding line outside in this kind of circumstance so is without a meaning. If put,have not solder shows defect, because fatigue crackle will be absent Yugao and solder foot place are initiative crack, transform department of welding line root however not solder is in fully. In have not below the case that solder shows blemish to exist, machine treatment often can reduce contact exhaustion intensity instead. Normal > need not have machine treatment to metal of integral welding line sometimes, and need to use machining grinding processing to solder foot place only, this kind of practice can increase contact exhaustion strength substantially. Consider to make clear, below this kind of circumstance, the dot is being cracked since is not to be in solder foot place, change position of welding line blemish however. Normal > is right excel in steel (of welding line of transverse butt joint of B=1080 MPa) of tensile strength σ hand in change the fatigue pressure test of load makes clear, in below as welded condition 2 × intensity of the exhaustion when 106 circulations time is ± 150MPa, if undertake to welding line machining is handled, eliminate beyond is tall, fatigue intensity raises ± 275MPa, this already comparatived with the fatigue intensity of basic metal. But if undertake local grinding to solder foot place,machine, its exhaustion intensity is ± 245MPa, 83% it is machine treatment effect, compare with as welded photograph, fatigue intensity rises 65% , it is to use machine treatment method no matter of course, still be grinding method, if cannot undertake carefully by the requirement, so that assure to machine the effect, of fatigue intensity rising is finite. Normal >3.

1.

Normal > uses emery wheel grinding, although its effect is inferior to machining, but also be one kind rises solder the effective method of contact exhaustion intensity. International Institute of Welding recommends the emery wheel that introduces high speed electric power or hydraulic drive, rotate speed is (15000~40000)r/min, emery wheel by carbon - tungsten material is made, its diameter should assure burnish deepness to radius should is equal to or be more than 1/4 board thick. Recent research makes clear international Institute of Welding, after sample classics burnish, its the nominal and fatigue intensity below 106 loops of 2 × rises 45% , if will get 199MPa fatigue intensity is nominal value conversion becomes corresponding eigenvalue (135MPa) it also the highest FAT value in the intensity of contact detail exhaustion of Institute of Welding of prep above international. Those who want an attention is grinding direction should agree with direction of line of force, keep as perpendicular as line of force score in the meeting in welding line otherwise, it is equivalent to stress centering a source, rise to reduce the effect of contact exhaustion intensity. Normal >3.

1.

Normal > method was to develop a kind of new-style welding rod, its liquid state metal and liquid state are slaggy have higher dissolve wet capacity, can improve the radius blend of welding line, reduce solder foot angle, the stress that drops solder foot point centers degree, rise thereby solder the fatigue intensity of contact. The defect phase that builds with TIG frit is similar, it to soldering the position is had stronger alternative, special agree with position of flat position welding and solder of a straight angle, and mix to vertical position welding, horizontal position welding admire solder, its advantage was reduced significantly. Normal >3.

The 2 methodological Normal >3.

2.

1 beforehand overload law Normal > brings to bear on on the sample that contains stress concentration drawing load, until happen in breach place succumb, accompany the drawing plasticity with have certain to be out of shape, after uninstalling, carry breach to reach drawing plasticity happens to be out of shape place general generation reduces stress near its, and the under yield point tensile stress that in sample sectional place will have other to be balanced with its arises. Get the sample that manages here, in its subsequently exhaustion experiments in, its stress limits will with primitive did not bring to bear on beforehand the sample of overload is different, namely remarkable decrescent, accordingly it can rise solder the fatigue intensity of contact. Study the result makes clear, large solder structure (wait like bridge, pressure vessel) it is certain to before investment moves, need to undertake beforehand overload experiments, this fatigue to rising function is advantageous. Normal >3.

2.

Normal > uses local heating to be able to adjust solder leftover stress field, be in generation to reduce leftover stress centrally in stress namely, consequently fatigue to improving joint intensity is advantageous. This kind of method is restricted to be used at fore-and-aft blame at present successive welding line, or have fore-and-aft the connect that adds muscle board. Normal > is received to bosseyed horn board, heat the position is apart from welding line to be about commonly board wide 1/3, receive to double-faced horn board the circumstance heats the position is panel center. Can make sure inside welding line generation reduces stress so, can increase the fatigue strength of contact thereby. Different investigator applies the result that this method gets to differ somewhat, receive to bosseyed horn board, raise fatigue intensity 145%-150% , receive to double-faced horn board, raise fatigue intensity 70%-187% , . Normal > local heating has main effect, when the dot shape heats is a part is carried in welding line when two undertake, the breach part that carries a department in welding line was caused reduce leftover stress, as a result fatigue intensity rises 53% ; But when the dot shape heats is in welding line center of the sample that carry a department undertakes when, be apart from welding line to carry a distance is identical, although this produced same metallographic to organize an influence, but because leftover stress is drawing remains stress, the contact exhaustion intensity that measures and blame processing sample are same. Normal >3.

2.

Normal > local extruding and drop record heat the method is same, all be to rely on to compress leftover stress to increase contact exhaustion strength namely. But its action point is different, extruding position should be located in need to produce remains to reduce the position of stress. Sample of excel in steel uses extruding method its effect is more more distinct than mild steel. Normal >3.

2.

4Gurnnerts method Normal > heats as a result of what decide local heating way well and truly hard sometimes the position and heat temperature, to achieve satisfactory result, gunnert offers a kind of means, the point of this method is direct to breach place is not the place around heats to be able to produce plasticity to be out of shape but under change temperature the temperature of 55 ℃ or 550 ℃ , next quick gush drenchs cooling. What because surface layer issues metal and the metal that gush did not suffer to drench all round its,cool is later, the systole when waiting for its to cool will be in cooling already apparently generation reduces stress. Thereby compresses stress to be able to increase the fatigue strength of component part. Those who need an attention is: Heat to make rock-bottom Yi Da arrives purpose, heat the process wants some slower, gunnert suggests to heat time is 3min, and Harrison suggests to heat time is 5min. Normal >Ohta used what this method succeeds to prevent interior of butt joint conduit to produce fatigue crackle. Specific means is conduit exterior use inductive law to heat, with the loop water cools inside. Because this arose to reduce stress in conduit interior, prevented fatigue crackle effectively to arise in conduit interior consequently. The fatigue crackle of conduit of welding line of the butt joint after processing expands rate is reduced greatly, achieve as patulous as the crackle with mother same capable person rate. Normal >3. The 3 methodological Normal >3. 3.

1 hammer attacks law Normal > hammer strikes a law is cold working method, its action is in contact solder foot place surface is caused reduce stress. Accordingly, the effectiveness of this method and the plasticity that arise in solder foot surface are out of shape about; At the same time hammer attacks the breach acuteness that still can reduce presence to spend, reduced stress concentration consequently, this also is the reason that increases contact exhaustion strength substantially. The air hammer pressure that international Institute of Welding recommends should be 5~6Pa. Peen coping should be the hypostatic material of 8~12mm diameter, recommend use concussion 4 times to be amounted to in order to make sure hammer attacks deepness 0.

6mm. Recent job makes clear international Institute of Welding, bear the weight of to be not T form connect, after hammer is attacked its intensity of exhaustion of the connect below 106 loops of 2 × rises 54% . Normal >3. 3.

Normal > gush bolus is another kind of form that hammer attacks, also belong to the method that pounds treatment. The effect of 9 relies on gush dimension of gush bolus diameter, gush pill measure should not pass big, in order to make its can handle tiny flaw. In the meantime, gush pill measure also should not pass small, in order to assure certain cold make sclerotic property, gush bolus can produce effect on the deepness in apparently thousand millimeter commonly. Study the result makes clear, gush bolus can increase the fatigue strength of connect of excel in steel significantly, gush bolus has outstanding effect to material of steel of excel in of argon arc solder, its rate is repaired high even at TIG frit. At the same time TIG frit make repairs and supply replacements is attacked with gush bolus hammer, criterion its effect is more distinct. Normal >4 rises solder the latest technology Normal >4.

Normal > solder the method of contact and structural exhaustion intensity, its mechanism and hammer are attacked and gush bolus agrees basically. But actuator of this kind of method is deft, it is good to can charge a sex, use minimum of agile and convenient, noise, efficiency suffer when tall, application be restricted little, low and cost is energy-saving, apply to all sorts of connect, the improvement after the solder that is a kind of ideal solders the method of contact exhaustion function. To a few kinds the model solders the structure bears the weight of with the butt joint of steel and blame fore-and-aft horn connect carries out supersonic concussion to handle, the comparative exhaustion that undertook as welded and concussion processing next experiments, studied supersonic concussion law improves the practical effect of intensity of solder connect exhaustion, comparative result sees a table 2. Visible, solder after contact is handled via supersonic concussion, fatigue intensity raised 50%~170% , the effect is very distinct. Normal >4.

2 low photographs change Normal >4.

2.

1 rise solder principle of contact exhaustion intensity and development Normal > compresses stress to be able to rise solder the fatigue intensity of contact, already many document is discussed, however if why soldering,the problem is the more convenient introducing in contact reduces stress. Normal LINE-HEIGHT of fatigue intensity contrast that Center" Align=center> expresses 2 supersonic concussion to handle from beginning to end: 14pt; TEXT-ALIGN: Center" Align=center>normal > is well-known, because content of chemical composition, alloy and cooling rate are different, steely material can produce different organization in cooling process change or for many times constituent change, change of this one organization is accompanied bulk expands, will arise to change below cabined condition stress, belong to reduce stress. To welding line metal, this reduces those who be helpful for leftover tensile stress appear even remains reduces stress, improve thereby solder the mechanical function of contact. Low photograph changes bit of welding rod (Low Transformation Temperature Welding Electrode, LTTE) use one kind namely change stress is soldering the generation in contact compresses stress to rise solder of contact exhaustion intensity new-style solder material. Normal > is in early 60 time, russia solders before the expert put forward low photograph to change method of dot welding rod can rise solder fatigue intensity of the structure, but did not put forward at that time " low photograph changes bit of welding rod " concept, call its a kind of special welding rod only the Mn content that composition of its v metal basically relies on 3%-4% will reduce change dot, implementation metallurgy photograph changes. Document points out, choose these special welding rod, when having fatigue test to small test specimen, the fatigue intensity after using these welding rod v wants prep above not v experiments 75% . Normal > in last few years, support Cr and Ni are reduced solder the martensite photograph of metal of material frit apply changes dot, develop as a result of what exceed mild steel ability, low photograph changes dot welding rod got rapid development, japan and China had much research in this respect, but still be in at present lab phase. Normal >4.

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2LTTE welding rod improves the effect Normal > Tianjin university is designed and optimize developed low photograph to change bit of welding rod, be in all sorts of soldering undertook many fatigue experiment and technical properties experiment on contact. Normal > (1) LTTE method Normal > uses low photograph to change bit of welding rod LTTE and E5015 of common welding rod part to bear the weight of to connect of transverse butt joint, blame cruciform joint, fore-and-aft surround connect of fillet weld connect, fore-and-aft parallel fillet weld and connect of fore-and-aft butt joint apply solder, undertake fatigue contrast experiments. The result makes clear, change the fatigue intensity of connect of bit of welding rod LTTE compares E5015 of common welding rod to receive fatigue intensity to rise respectively 11% , 23% , 42% , 46% close 59% , fatigue life increases scope from arrive severalfold about a hundred times. Normal Align=center> expresses 3 different types to solder the improvement of contact exhaustion intensity effect Normal Align=center>normal > changes as a result of low photograph dot welding rod is the remains that produces martensite photograph to change to bulk expands and be obtained below inferior temperature reduces stress, the size that reduces stress because of this remains and solder contact is cabined degree have bigger concern, cabined degree bigger, its remains reduces stress bigger, of fatigue intensity improve the result bigger also. Normal > (2) low photograph changes frit of foot of solder of dot welding rod repairs (LTTE-dressing) methodological Normal Align=left> however, to make welding line metal is in regular cooling rate falls and martensite photograph happens to change below inferior temperature, solder more alloying element was added in material, make thereby low photograph changes the cost that spot welding receives data rises a lot of. If one solders,entire welding line of the structure uses low photograph to change solder material undertakes applying solder, solder structural cost also will raise substantially, this is very wasteful. Normal Align=left> is well-known, solder contact fatigue fracture is main from craze of solder foot place, if make solder,the remains of generation of solder foot place of contact reduces stress, can rise solder the fatigue intensity of contact, and do not need to use low photograph to change entirely bit of welding rod, can reduce use cost so. From consideration of this one train of thought, tianjin university put forward low photograph to change on the foundation of the experiment frit of foot of solder of dot welding rod is repaired (LTTE-dressing) rises solder the method of contact fatigue intensity. Use blame bear the weight of cruciform joint and fore-and-aft surround fillet weld connect type of two kinds of connect, contrasted respectively low photograph changes frit of foot of solder of dot welding rod is repaired (LTTE-dressing) and common welding rod solder the fatigue intensity of contact, former fatigue intensity rises than latter respectively 19.

9% with 41.

7% , the feasibility that proved this one train of thought and practical, change for low photograph bit of welding rod LTTE is more reasonable was in the project is actual medium applying to undertake early days experiment studies, at the same time low photograph changes frit of foot of solder of dot welding rod is repaired (LTTE-dressing) connect also can mirror low photograph to change the applied case that dot welding rod is building cover welding line and close solder foot to build face solder to. Normal >4.

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3 low photographs change of bit of welding rod actor defect Normal > advantage: Normal >(1) low photograph changes dot welding rod solders the method is be accompanying solders the process undertakes at the same time, avoided the inconvenience that processing machines after solder; Normal >(2) low photograph changes method of dot welding rod need not handle a demand specially, consequently the operation goes to the lavatory simply; Normal >(3) low photograph changes spot welding receives material to be used at rising to solder contact exhaustion intensity, because do not suffer follow-up solder path to heat up the influence of action, it more agree with concealment the fatigue intensity of the welding line, welding line that be enclothed, rear welding line of bosseyed solder welding line that cannot make processing machines after solder raises;normal > (4) LTTE welding rod still can be used at soldering the rehabilitate of structural exhaustion crackle. Normal > defect: Solder more alloying element was added in material, make thereby low photograph changes the cost that spot welding receives data rises. But can try to make up for through the method such as LTTE-dressing. Normal LINE-HEIGHT of Exactly">5 last word: 18pt; Mso-line-height-rule: The place on Exactly"> put together is narrated, because solder,in recent years it is thus clear that the structure has the tendency that develops toward direction of high speed burden, bear to its dynamic the demand of ability is higher and higher, because this development reachs promotion application,improvement solders the new technology of contact exhaustion function solders to driving applied sense of the structure is great. Relative to character, the supersonic concussion technology that domestic and international newest development rises and use low photograph to change spot welding receives material to rise solder the method of contact exhaustion intensity is to solder the important research way that structural exhaustion function improves technology and technology. CNC Milling