Numerical Modeling of Friction Welding Process

Transcription

1 Numeical Modeling of Fiction Welding Pocess Ali. Moaefadeh Abstact Fiction welding is a solid state joining pocess which can be used to join a numbe of diffeent metals. Fiction welding achieves 100 pe cent metal-to-metal joints, giving paent metal popeties. It is the only joining pocess to do this. No addition mateial o filles ae equied and thee ae no emissions fom the pocess. The themal effect of fiction welding that specially depends on the fiction type and tempeatue field of it in wokpiece, is the main key of analysis and optimiation of this pocess, fom which the main goal of this pape has been defined. Numeical simulation of welding pocess in SIMPELC method and by ANSYS softwae fo gaining the tempeatue field of cabon steel, the effect of paamete vaiation on tempeatue field and pocess optimiation fo diffeent cases of electode done. Keywods Numeical Simulation, Fiction, Weld, SIMPLEC, ANSYS, Tempeatue Field and Cabon Steel F I. INTRODUCTION iction welding is a solid state joining pocess which can be used to join a numbe of diffeent metals. Fiction welding achieves 100 pe cent metal-to-metal joints, giving paent metal popeties. It is the only joining pocess to do this. No addition mateial o filles ae equied and thee ae no emissions fom the pocess. The pocess involves making welds in which one component is moved elative to, and in pessue contact, with the mating component to poduce heat at the faying sufaces. Softened mateial begins to extude in esponse to the applied pessue, ceating an annula upset. Heat is conducted away fom the intefacial aea fo foging to take place. The weld is completed by the application of a foge foce duing o afte the cessation of elative motion. The joint undegoes hot woking to fom a homogenous, full suface, high-integity weld. Metals ae made up of positive ions floating in a sea of electons (Fig. 1). Howeve, in a pactical situation metal pieces do not spontaneously bond to each othe and fom 1 piece. This is because even polished metal sufaces have a laye of oxide and suface contamination. They ae also not smooth enough fo the atoms to be bought close enough to bond. In fiction welding, the sufaces ae ubbed togethe to bun off the oxide and suface contamination layes and bing the atoms in close enough poximity to bond. A. Types of Fiction Welding Rotay Rotay fiction welding is the most common fom of fiction welding and has become the industy standad fo a numbe of pocesses including welding API dill pipes and dill ods, joining of axle cases and spindles and welding of piston ods. Faculty membe of Depatment of Mechanical Engineeing, Mahshah Banch, Islamic Aad Univesity, Mahshah, Ian; a_moaefadeh@yahoo.com, a.moaefadeh@mahshahiau.ac.i Tel: Fig. 1. Fiction Welding Pocess Rotay fiction welding involves holding one component still while spinning the othe component and bining the two togethe. Thompson Fiction Welding is the wold leades in otay fiction welding having supplied ove 500 machines and has ove 45 yeas expeience. In ode fo a join to be successful the following pocesses must take place (Fig. 2): a) Pe-Contact: One pat is held stationay in a fixed clamp. The othe pat is held in a otating chuck. (a) b) Fist Fiction: The chuck is acceleated to speed and the pats bought into contact unde a light foce. (b) c) Second Fiction: The foce is inceased plastic mateial stats to extude fom the weld inteface. [ISSN: ] 47

2 (c) d) Second Fiction: The second fiction phase continues until sufficient mateial has been extuded. calculated though yeas of expeience. Howeve, as the pocess is inheently obust and flexible, deviations on these paametes can still give a good weld. In linea fiction welding the same pinciples apply as otay. One component is held still while the othe is moved at speed and the two ae bought togethe. The diffeence is that the moving component does not otate; it is made to oscillate lateally. The weld times fo pats ae simila no matte how big the pat. Due to the geomety, otay fiction welding does not have any fiction in the cente of the otating pat. This potion of the weld must heat up conventionally athe than due to fiction. This is not the same fo a linea fiction weld. Fiction occus thoughout the weld suface. This means that weld times ae vey quick and do not vay hugely fom pat sie to pat sie. The lagest linea fiction weld eve poduced at Thompson Fiction Welding had a weld time of aound 4 seconds. II. NUMERICAL SIMULATION (d) e) Foge: Rotation is stopped the foce inceased and the pats foged togethe. (e) f) Weld Complete: The weld is complete a full aea, homogenous bond. (f) Fig. 2. Fiction welding joints desciption The otay fiction welding pocess is inheently flexible, obust and toleant to diffeent qualities of mateials. The paametes involved ae the otational speed, time and foce applied. Thee ae optimum paametes fo each paticula weld that Thompson Fiction Welding has The diffeential Equations (1) (4) ae solved iteatively by the SIMPLEC numeical pocedue: Mass continuity equation: 1 ( ρυ ) + ( ρυ ) = 0 (1) Radial momentum consevation equation: 1 2 ( ρυ ) + ( ρυ υ ) = ρ 1 υ j Bθ + (2η ) + υ υ υ ( η + η ) 2η 2 Axial momentum consevation equation: 1 ( ρυ ) ( 2 υ + ρυ ) = ρ υ + j Bθ + (2η ) + (3) 1 υ υ ( η + η ). Enegy consevation equation: 1 ( ρυ h) + ( ρυ h) = 1 k h k h ( ) + ( ) + c c j E p + j E R, p In the solution of Equation (1) (4), special attention needs to be put on the enegy effects on the electode suface. At the cathode suface, additional enegy flux tems should be included in Eq. (4) because of themionic cooling due to the mission of electons, ion heating, and adiation cooling [2]. (2) (4) [ISSN: ] 48

3 Finite-Element techniques: 1- Finite elements modeling, types and popeties fo model diffeent pats. 2- The definition of mateial popeties 3- Paamete definition 4- Loading 5- Bounday and initial value definition III. ADVANTAGES OF FRICTION WELDING Fiction welding has become industy standad in a numbe of applications. Some of the advantages of the pocess ae detailed below: Weld monitoing can insue 100% weld quality Fiction welding poduces a 100% coss sectional weld aea Fa supeio weld integity compaed to MIG welding Limited opeato taining equie full automation also possible The weld cycle is fully contolled by the machine Repeatable esults Fiction welding is a solid state pocess and does not suffe fom inclusions and gas poosity. Fiction welding equied no consumables theefoe becomes moe cost effective ove time Fiction welding typically will complete a full coss sectional weld in 15% of the time it take MIG welding to poduce an 85% coss sectional weld. Fiction welding equies no special weld inteface pepaation welding) No post machining is needed fo fiction welded components in many cases Dissimila mateials can be joined with no alloying of the mateial IV. RESULTS AND DISCUSSION Conclusions fo fluid tempeatue field cabon steel tempeatue field, completely shown in Fig. 3. A peson acting as Fie Watche must be standing by with suitable fie extinguishing equipment duing and fo some time afte welding o cutting if Combustibles (including building constuction) ae within 10 metes. Combustibles ae futhe than 10 metes but can be ignited by spaks. Openings (concealed o visible) in floos o walls within 10 metes may expose combustibles to spaks. Combustibles adjacent to walls, ceilings, oofs, o metal (a) Fig. 3. Conclusions fo tempeatue field: a) tempeatue field, b) Cabon steel tempeatue field (b) patitions can be ignited b adiant o conducted heat. Afte wok is done, check that aea is fee of spaks, glowing embes, and flames. Any tank o dum which has contained combustibles can poduce flammable vapos when heated. Such a containe must neve be welded on o cut, unless it has fist been cleaned as descibed in AS , the S.A.A. Cutting and Welding Safety Code. This includes a thoough steam o caustic cleaning (o a solvent o wate washing, depending on the combustible's solubility), followed by puging and ineting with nitogen o cabon dioxide, and using potective equipment as ecommended in AS Wate-filling just below woking level may substitute fo ineting. Hollow castings o containes must be vented befoe welding o cutting. They can explode. Neve weld o cut whee the ai may contain flammable dust, gas, o liquid vapos. Exposed conductos o othe bae metal in the welding cicuit, o ungounded electically alive equipment can fatally shock a peson whose body becomes a conducto. Ensue that the machine is coectly connected and eathed. If unsue have machine installed by a qualified electician. On mobile o potable equipment, egulaly inspect condition of tailing powe leads and connecting plugs. Repai o eplace damaged leads. Fully insulated electode holdes should be used. Do not use holdes with potuding scews. Fully insulated lock-type connectos should be used to join welding cable lengths. Teminals and othe exposed pats of electical units should have insulated knobs o coves secued befoe opeation. The output fluid tempeatue field fom nole showing heat tansfe way between electical ac and electode and envionment, with elated tempeatues is completely dawn in Fig. 4. Fo study the tempeatue vaiations in plasma axis and its heat tansfe to electode accoding to diagam (Fig. 5), the tempeatue field of electical ac in its symmety axis with standoff is dawn. In this diagam, in each distance fom nole to wokpiece suface, the desied tempeatue can be deived. Themal conductivity vaiation and themal specific of cabon steel ae shown in Fig. 6 and Fig. 7. Fig. 8 shows a BSE image of the inclusions. White shows the aeas whee the espective element is found, and black shows a lack of that element. By compaing Fig. 8, it can be seen most of the sulfuis in the inclusions, as expected. [ISSN: ] 49

4 Fig. 4. Electical ac tempeatue field Fig. 8. SEM (BSE) image of inclusions (500X), Location of S (500X), Location of Mn (500X) Fig. 5. The tempeatue field of electical ac in its symmety axis by standoff Fig. 6. Themal conductivity of cabon steel Fig. 7. Themal specific of cabon steel V. CONCLUSIONS Exposed conductos o othe bae metal in the welding cicuit, o ungounded electically alive equipment can fatally shock a peson whose body becomes a conducto. Ensue that the machine is coectly connected and eathed. If unsue have machine installed by a qualified electician. On mobile o potable equipment, egulaly inspect inspect condition of tailing powe leads and connecting plugs. Repai o eplace damaged leads. Fully insulated electode holdes should be used. Do not use holdes with potuding scews. Fully insulated lock-type connectos should be used to join welding cable lengths. Teminals and othe exposed pats of electical units should have insulated knobs o coves secued befoe opeation. A 3D mathematical model fo the metal tansfe pocess in FRICTION WELDING was fomulated in this aticle. A complete model descibing the FRICTION WELDING welding pocess is developed, howeve, the computation of the tansient solution of the complete model was pohibitively time-consuming and beyond the capability of the cuent PCs. In ode to study the plasma ac inteaction with metal duing the metal tansfe pocess, some simplifications have been made. A case of an axisymmetic ac was studied fist using this 3D model fo the veification pupose. The numeical esults ageed well with the pevious two-dimensional studies. A case of a moving ac was then computed to demonstate the 3D capability of the model. The esults evealed that the time-invaiant Gaussian assumption fo the distibutions of the ac pessue, heat flux, and cuent density on the wokpiece suface did not epesent of the eal situation. The calculated distibutions fo the moving ac wee non-axisymmetic and the peaks shifted to the ac moving diection. The bittle natue of the welded pat was investigated using tensile tests, impact tests, and SEM photogaphs. Seveal heat teatments wee investigated in an attempt to estoe the ductility of the samples. No heat teatment could be found that estoed the ductility and impact stength. The 416 can be fiction welded with adequate tensile stength, but thee was a sevee loss of ductility and impact stength due to the eoientation of the sulfide inclusions. [ISSN: ] 50

5 REFERENCES [1] S. Tashio, M. Tanak, L. Muph, and J. Lowke, "Pediction of enegy souce popeties of fee-buning ac" Welding Jounal, Mach 2008, pp [2] A. Moaefadeh, "Numeical simulation of tempeatue field by Plasma ac welding Pocess in stainless steel", IREMOS Jounal, Febuay 2010, pp [3] A. Moaefadeh, Choosing Suitable shielding gas fo themal optimiation of GTAW pocess, IREME Jounal, Sep [4] E. Goman, New developments an application in Fiction welding, Welding Jounal, July 2004, pp [5] Y. Wang, and Q. Chen, "On-line quality monitoing in Fiction welding, Jounal of Mateials Pocessing Technology, Januay 2005, pp [6] H. Kyselica, "High Fequency evesing ac switch fo plasma welding of Aluminum" Welding Jounal, May 2005, pp [7] G. Langfod, "Plasma keyhole ac welding of stuctual stainless steel joints", Welding Jounal, Feb 2005, pp [8] ANSYS Help system, Analysis Guide & Theoy Refeence Ve. 9, 10. Ali Moaefadeh Faculty membe of Depatment of Mechanical Engineeing, Mahshah Banch, Islamic Aad Univesity, Mahshah, Ian Tel: [ISSN: ] 51