Marquette Universitye-Publications@MarquetteMechanical Engineering Faculty Research andPublications Mechanical Engineering, Department of

11-1-1992

Development of Knowledge-Based Systems forAluminum WeldingR. J. NapolitanoCarnegie Mellon University

H. KullukCarnegie Mellon University

Mark L. NagurkaMarquette University, mark.nagurka@marquette.edu

R. P. MartukanitzPennsylvania State University

P. B. DickersonAluminum Co. of America

Published version. Welding Journal, Vol. 71, No. 12 (December 1992): 43-47. Publisher link. © 1992American Welding Society. Used with permission.Mark L. Nagurka was affiliated with Carnegie Mellon University at the time of publication.

Development of Knowledge-Based Systems for Aluminum Welding

Computer programs offer the extensive knowledge of experienced engineers

BY R. J. NAPOLITANO, H. KULL UK, M. L. NAGURKA, R. P. MARTUKANITZ AND P. B. DICKERSON

W elding engineers experienced wi th aluminurn pos­sess knowledge generally unavailable to others, in­

c luding those in need of such information such as design-ers and manufacturers of welded aluminum structures. The experienced engineers are often asked to: 1) recornmend appropriate filler metals, 2) recommend starting welding parameters; and 3) d iagnose difficu lties encountered dur­ing aluminum weld ing. Developing computer-based ex­pert systems in these areas can reduce the time required for o thers to access the desired information, overcome the limitations associated with the present methods of obtain­ing this informa tion and provide knowledge transfer by ex­posing users to the thought processes of experienced weld­ing engineers. Examples of two computer-aided welding systems are described in Refs. 1 and 2.

The present method of determin ing appropriate fil ler metals and welding parameters in industry is through the use of selecti on charts and tables. Although these have served their pu rpose well , there are advantages to com­puter methods. W ith appropriate design, knowledge-based systems can be extended rather easi ly to contain more in­fo rmation deemed usefu l to the user. The computer soft­ware can provide more complete information that would require l iterally hundreds of footnotes and additional charts and tables in the present method. For example, the appro­priate setting for arc voltage, and consequently amperage, depends on the parti cular type of fi ller metal employed in the gas metal arc welding (GMAW) process. The SXXX se­ries filler metals, wi th magnesium as the primary alloying element, requ ire higher current and lower arc voltage to

R. J. NAPOLITANO is with Department of Mechanical Engineer­inr;, Carnegie M effon University. 1-1. KULLUK and M. L. NACURKA are with Department of M echanical Engineering and Robotics lnsti lllte, Carnegie Meffun University, Pittsburgh, Pa. R. P. MARTUKANITZ is with Applied Research Laboratory, Penn­sylvania State University, State College, Pa. P. B. DICKERSON is rf'/ired, formerly with Aluminum Cu. of America.

ensure proper metal deposition compared to 4XXX filler metals and maintain total heat input, respectively. Another example is the fact that shielding gas composition as well as flow rate influence weld penetration and cross-sectional area (Refs. 3, 4). The addition of a certain percentage of helium to the argon shielding gas can be advantageous in particular situations. This type of knowledge can readily be incorporated into a knowledge-based system. Another advantage is that it can provide explanations for its con­clusions. This exposes users to the thought processes of ex­perienced welding engineers and streamlines knowledge transfer.

Toward this goal, in cooperation with the Aluminum Co. of America (Alcoa), two user-friendly software pack­ages were developed and a third module is in the final pro­totype stage. One package, the Filler Metal Selector is a knowledge-based system that recommends optimal filler metals for gas metal arc (GMA} and gas tungsten arc (GTA) welding of aluminum. The second package, the Process Parameter Sel_e~tor, provid~s typical starting welding pa­rameters and Joint preparations for a variety of base metal thicknesses. Currently under development is a third pack­age, the Weld Defect and Diagnostic System, which is a knowledge-based program to assist in determining causes of weld discontinuities during aluminum welding and to reco~1111end correcHve procedures. These three systems const1tute_the Aluminum Welding Engineer series and rep­resent an 111tegral part of the proposed interactive welding engi ne~ring workstation. The software systems were cre­ated with the help of several welding engineers, and the systems incorporate th:ir knowledge representing over one hundred years of experience with Alcoa in aluminum weld­ing.

Software Design

After reviewing several expert system shells it was de­cided to use Personal Consultant Plus (PC+) 1;arketed by

WELDING JOURNAL I 43

ALUMINUM WELDING ENGINEER • Filler Metal Selector

~ Current olJiective:

ALCOA

Filler Metal Selector

This Expert System recommends optimal filler metals for GMA and GTA welding of Aluminum.

It will recommend fillers for any combination of alloys being welded, including castings, as well as when Postweld Thermal processing is being used.

Information regarding the application, joint design and particular alloys being welded is asked, and type of Postweld thermal processing where appropriate.

•• End • RETURN/ENTER to continue

Fig. 1 - Filler metal selector introductory screen.

Texas Instruments. The software is inexpensive, can be run on any IBM or fully compatible computer, is well sup­ported and maintained and is easy to learn and use. It pro­vides the ability to access externally written routines and external databases, can be integrated with graphics, and can explain in text why the system reaches a certain con­clusion. Additional access to PC Scheme, a dialect of Lisp capable of running on personal computers, is provided, and it was used extensively in the development of these systems.

Personal Consultant Plus is a rule-based expert system shell. The rules themselves are entered into the knowledge base using the Abbreviated Rule Language (ARL). The knowledge-based designer provides translations for each parameter used in the system. PC+ uses these translations and the format of ARL to generate plain-English transla­tions of the rules, useful for development purposes, and for the conclusions that the end user sees. This is an im­portant aspect of the software that allows the users of the system to follow and understand the experts' thought pro­cesses represented by the knowledge base. The software has a data type called a frame which allows the knowl­edge base to be divided into logical segments. This is ex-

ALUMINUM WELDING ENGINEER • Filler Metal Selector

PIPING

fl[[) NO

The following weld property requirements for this application have been assumed:

WELDABILrrY STRENGTH DUCTILITY CORROSION HIGH TEMP COLOR MATCH

VERY IMPORTANT IMPORTANT IMPORTANT VERY IMPORTANT NOT IMPORTANT NOT IMPORTANT

Do you agree with these values?

1. use the arrow keys or first letter of item to position cursor. 2. Press RETURN/ENTER to continue.

Fig. J - Screen showing default weightings of weld properties for a piping application.

44 I DECEMBER 1992

ALUMINUM WELDING ENGINEER • Filler Metal Selector

Select the most appropriate application > AEROSPACE ARCHITECTURAL ARMOR-BALLISTIC AUTOMOTIVE CRYOGENIC ELECmlCAL•CONDUCTOR FURNITURE HOME-APPLIANCE

I W~;QkMARINE I PRESSURE-VESSEL RAILROAD CAR STORAGE-TANK STRUCTURAL 01her

1. Use the arrow keys or first letter of item to position cursor. 2. Press RETURN/ENTER lo continue.

Fig. 2 - list of typical applications in aluminum welding show­ing the selection of a piping application.

tremely useful in the development of large and complex knowledge bases. It also speeds execution times for the end user by loading in only those frames that affect the course of the consultation, i.e., the thought processes rep­resented by the rules. The software is user-friendly, which is exemplified by the presentation of inquiries and conclu­sions, both graphic and literal, to the end user. This soft­ware development tool was used to create the expert sys­tems from the knowledge domains described previously.

Filler Metal Selector

The selection of appropriate filler metals essentially in­volves optimizing desired weld characteristics under met­allurgical and mechanical constraints determined by the materials' chemical and physical properties. The system asks a series of questions related to the above, determines which filler metals are most appropriate for the alloys being welded, evaluates each of these separately and then rec­ommends one or possibly several filler metals. When post­weld thermal processing is employed or when welding certain castings and wrought products, there are few filler metals deemed appropriate, and the system simply recom-

ALUMINUM WELDING ENGINEER • Filler Metal Selector

Select the particular type of butt Joint >

SQUARE-BUTT-NO-GAP SQUARE-BUTT-WITH-GAP

lstNGLE-Y I DOUBLE-V SINGLE-U DOUBLE-U

1. Use the arrow keys or first letter of item to position cursor. 2. Press RETURN/ENTER to continue.

5c v3,- • l'i 'I Ii ~f Fig. 4 - Screen for specific type of butt joint with single-V-groove joint design selected.

j

ALUMINUM WELDING ENGINEER • Filler Metal Selector

Select tho first base alloy >

~ 6063 6005 6009 6010 6013 6070 6101 6201 6151 6351 6951

1. Use the arrow keys or first letter of item to position cursor. 2. Press RETURN/ENTER to continue.

Fig. 5 - Screen for 6XXX series wrought alloys showing 6061 se­lected.

mends their use. In general, the following information is required: 1) The

application, which dictates desired weld characteristics; 2) the particular joint design; and 3) the base metals being welded.Currently, there is information available for over 60 base metals, including both wrought products and cast­ings.

The system first displays an introductory screen describ­ing the program and its function - Fig. 1. It begins by de­termining the desired weld characteristics dictated by de­sign requirements and/or service conditions, and then pre­sents the user with a list of possible applications for alu­minum welding, such as automotive or aerospace uses, pressure vessels, or home appliances to name a few. This screen is shown in Fig. 2. Once the user selects a particu­lar application, the system retrieves from an external file the default values of the relative importance of six weld properties. The user is shown the default values and may change any or all of the relative weightings. Figure 3 de­picts the screen showing relative weightings for a piping application. There are three possible relative weightings that can be assigned to each weld attribute. The weight­ings (very important, important and not important) deter­mine the order and importance placed on the various weld attributes or characteristics.

r ALUMINUM WELDING ENGINEER - Process Parameter Selector "I

.-Currant Objective: ALCOA

Process Parameter Selector

The Process Parameter Selector recommends starting procedures for GMA and GT A welding of aluminum.

Inputs are the type of process, the basic form

fa's~:::,~~ :~~~~h:~po~ ~iL~'~e:~r i:r~~ing used, If applicable.

The outputs are the electrode diameter. gas

rii0:~~:~=~~e9!~~~~::.:·r:11~~s:r;g•:~~ of necessary welding data •· Currents, Voltages and Travel speeds.

•• End • RETURN/ENTER to continue - ·~

Fig. 7 - Process parameter selector introductory screen.

ALUMINUM WELDING ENGINEER • Fillel Metal SeledOr

-PIPING JOINT-DESIGN - - BASE-ALLOY-WELDABIUTY : VERY IMPORTANT SlRENGTH :IMPORTANT

JOINT: SINGLE-V BASE•1 :356 DUCTD.ITY :IMPORTANT CORROSION : VERY IMPORTANT BASE-2:6061 HIGH-TEMP : NOT IMPORTANT COLOR MATCH : NOT IMPORTANT DILUTION RATIO: 0.4

- RECOMMENDATION NOT RECOMMENDED

The IIICXIITl'llllllded Illas - by DucUly ant : ALLER REASQ\I

5554 Cr.rddng V1rylasllyW11kild&IDl1I • 4043 5654 Cr.rddng No Easily welded Dens 5356 ComJSlan No Commerdalyweldallle filllrs 5183 Comlslon

5556 Comlslon

End - RETURWENTER IO c:ontlrue . Fig. 6 - Recommendation screen of the filler metal selector for pipe welding 6061 wrought alloy to 356 casting alloy utilizing a single-V-groove joint design.

The system next asks the user to provide the type of joint that will be welded. For a butt joint, a specific joint design is requested through a screen query, as shown in Fig. 4. A base metal/filler metal dilution ratio is calculated based on the particular joint design and is displayed for confirmation. The default ratio may easily be changed if the user is more confident of a more appropriate dilution ratio.

Information is available for over 60 base metals

The system next asks the user to identify the base ma­terials being welded. The alloy systems that are normally used for the specified application are presented and the system can easily account for welding of dissimilar alloys. Figure 5 shows the screen used for selecting 6XXX series wrought alloys for a piping application.

Once the alloys to be welded are obtained, the system utilizes the dilution ratio to determine applicable filler met­als based on the desired joint characteristics. Information pertaining to the applicability of the filler metals is shown by the system, and a final recommendation is made based

ALUMllllUM WELDING ENGINEER - PIOCIISS Pa!amstat Selaclor

Press any key to c:onllnue.

Fig. 8 - Screen output showing recommended single-V-groove joint design for GMA welding a 0.375-in.-thick plate.

WELDING JOURNAL I 45

At.UMINUM WELDING ENGINEER •• Process Parameter Selector - EQUIPMENT-SPECIFICATIO,. EDGE·PREPARATIO,,.

PROCESS: GMAW POLARITY: DC(EP) FORM: PLATE POSITION: FLAT GAS:ARGON JOINT:BUTT BACKING CUP DIAMETER: 1/2 In. ROOT OPENING WIDTH: 0.375 In GAS FLOW: 50 cfh HEIGHT: " ... '"

MIN: 0.125In. BEVEL: 60 ELECTRODE DIAMETER: 0.062 In. MAX: 0.125 In. NOM: 0.125In. LANO: 0.062In

'-SCHEDULE PASS CURRENT VOLTAGE TRAVEL SPEED TOTAL NUMBER CODE [Amps] [Volts) (1pm] OFPASSES: 3

1 245 30 21 2 245 30 21 3BR 245 30 21

End - RETURN/ENTER lo continue

Fig. 9 - Recommendation screen of the process parameter se­lector detailing suggested gas metal arc welding parameters for 0.375-in.-thick plate welded in the flat position.

on optimizing the desired attributes. Shown in Fig. 6 is the recommendation screen for pipe welding 6061 base metal to a 356 casting alloy utilizing a single-V-groove joint de­sign. The system may also be used to improve the utility of a filler metal by suggesting other joint designs.

Process Parameter Selector

The Process Parameter Selector recommends optimal starting welding parameters for gas metal arc (GMA) and gas tungsten arc (GTA) welding of aluminum. It has over 50 separate databases which contain information about welding parameters, as well as joint designs. It covers both plate and pipe welding and allows for different positions, joint designs and base metal thicknesses.

Over 50 databases contain parameter information

Parameter selection involves collecting information about the particular welding process, the basic form of the base metals, the joint design, the welding position, the base metal thickness and, in certain cases, the type of filler metal employed. The conclusions consist both of the re­quired essential parameters such as current, voltage and travel speed, as well as desired edge preparations.

The general approach the software takes is similar to that of an experienced welding engineer. The program first displays an introductory screen describing the inputs and outputs of the system - Fig. 7. The system first asks which particular process is being used, GMA or GTA welding. It then asks which basic form, plate or pipe, is being used. If pipe is chosen and the process is GMA, the system con­tains one database that is in the horizontal-rolled position. If pipe is chosen and the process is GT A, the three posi­tions, horizontal-rolled, horizontal-fixed and vertical-fixed may be chosen. If plate is selected, then the system re­quests what general joint design is of interest. The avail­able joint types are butt, T, lap, corner or edge. The sys­tem then asks which welding position is being used, flat, horizontal, overhead or vertical. Also, if GMA welding is chosen, the system needs to know which series filler metal is being used since it affects the choice of welding param­eters. The system then retrieves from an appropriate

46 I DECEMBER 1992

database the available thicknesses for this particular situa­tion and presents these to the user for selection.

The initial screen output shows the recommended joint design, as shown in Fig. 8, for GMA welding of 0.375-in. (9.5-mm) thick plate. This includes root face thickness, groove angle, root opening width and backing dimensions when necessary. The information provided at this screen is also in literal form on the final screen. The final screen, shown in Fig. 9, summarizes the inputs and provides rec­ommendations.

The approach is similar to that of an experienced welding engineer

The Equipment Specification window and the Edge Preparation window are self-explanatory. The Schedule window provides the actual number of passes and the pa­rameters for each pass. The pass coding utilizes BR to spec­ify backgouging on the root side.

System Verification

Extensive on-site testing has been performed for both the Filler Metal Selector and the Process Parameter Selec­tor. Two issues were of primary concern during this pro­cess. The first was reevaluating the experts' conclusions and ensuring the accuracy of their results, while the sec­ond issue in verification was to ensure that the system re­ported these same results to the user along with clear ex­planations as to how certain conclusions were reached. For the Filler Metal Selector, this involved having the ex­perts recommend filler metals when utilizing less common combinations of aluminum base metals. Their results and reasoning were compared to the system's recommenda­tions. When appropriate, modifications to the system were made to further improve its accuracy. In several cases re­assessment of the experts' recommendations were made. Hundreds of test cases have been performed for this sys­tem with excellent corroboration of the experts' recom­mendations. For the Process Parameter Selector, informa-

Hundreds of test cases have been performed

tion was taken from handbooks that are well maintained and represent values considered optimal by welders with many years of experience in aluminum welding. In this case, several conditions were tested at random by produc­ing weldments using the system's recommendations for welding parameters and joint design. With minor modifi­cations to the parameters, the system functioned as ex­pected and provided excellent starting conditions.

Conclusions

The development of the Filler Metal Selector and the Process Parameter Selector as well as initial work in con­structing the Weld Defect and Diagnostic System have led to the following conclusions:

1) The appli c a tion of kn o w ledge-based systems fo r welding is an effecti ve vehicle for capturing experts' knowl­edge and transferring it to o thers. W ith proper design, such sy stem s a llow easy access to the knowledge and thought p rocesses of experienced a luminum w elding engineers.

2) The system s sig nifi c an tl y reduce the time required to obtain the desired informatio n .

3 ) Knowledge-based sy stems ca n outperform current methods for obtaining desired information.

4) Knowledge-based sy stem s c an be used successfully by a wide varie ty of en cl u sers in terms of the ir degree of experience in aluminum w eld ing.

A ckno wledgments

The autho rs wou ld li k e to thank A lcoa, and the Ben Franklin Pa rtnership Program o f Pennsylvania fo r funding this work.

References

1 . Kuhne , A. H ., G ary, H . 8 ., and Prin z, F. 8 ., 1987. An ex­pert syste m fo r robo tic a rc w e lding . We/ding /ouma/66(11 ):21- 25.

2. Lucas, W. 1987. M ic roc ompute r syste m s, software and ex­pert s ys tems for weldi n g engineering . \N e/ding Journal 66(4):27- 30.

3. Re ic helt, W. R., Evanc ho, J. W ., and Hoy, M. G. 1980. Ef­fects of s hie lding g as o n ga s metal arc w e lding a luminum. Weld­ing Journal 59 (5):1 47-s to 15 5 -s.

4. Brungraber, R. )., and Ne lson, F. G . 1973. Effect of we ld ing variable s on a luminum a lloy w e ldm e n ts . W elding )ollmal 52(3 ):97-s to 11 3-s.

Stop Flash in its Tracks

K oike Sentinel flashback arrestors add safety to your cutting operation by reducing flash­back danger. Very compact in size, they dis­perse flash and absorb heat just like much larger arrestors. The easy-to-reset Sentinel Plus connects to your regulator, while the Super Sentinel attaches to hand and machine torches. For fuel gas and oxygen. See your Koike Aronson distributor or write for free data sheet. NOTE: In the event or flaShback. carefully inspect arrestor. coup­lings and an connected equipment prior to reuse.

II KOIKE ARONSON 635 W. Main St. Arcade, NY 14009 (716} 492-2400

Circle No. 18 on Reader lnfo•Card

U% Off Hotel Rates At Over 1,500 Locations Nationwide "American Welding Society" Part11ership With Quest Jnt,er,,ationa/,

Gives You Preferred Access To The Nation's Leading Hotel Savi.tigs Program nc it ! Y o u'll s<:k:ct from <>VL" r l, 'i()(J

, h<itcl s , all a v ailahl<: a t 'iO'¼, s avings! NI! W ith Qt1<.:st l nt<:rn:1 t io11:1 I. And njoin Q u est right now at hugcs:1v ings.

, You've Got The Advantage

-"Jl..,I ,ncmlx: rs hi p r<:lails for $ ')9. But 4J a s pc.:cia l agrL"L"lllL'nt wi th D L·s tin :1-lnc .. (1-1m11j.Jdistrilmto 1~fi,rQ 11cst ,. you'll .ra fractio n ofth<: rL"la il cost! Just $29.95!

I 50% Off! Are They Crazy?

1dl, hotc.:ls d o it? -- Simple. -- l'n!fi"ts.

I •·rage.:, a nnual hot c.: I o c c u pancy i<.: vL·is ,,,u n d 65 pcrccnt. But rc nH.:mlK-r that ·,« u pan cy mea n s :$~ of l'Ve ry l 00 rrn >rns

I .Dfys;iu:h n ight. And any addit ional m o rns '"p.in,.; a <.kl<.:d profit for t h<: h otL·I. / :1•c11

·,r 11011 swy f o r ha//:pricl'i

1' • a~iona ll y a ho;c.:1 fills cornpk-tL·ly. likL'

, ;ian,nvc.:ntion. If t hey <: Xp L-cl t<> fill tlwy •11·, line.: a half-pric <: re serv a tion . But. the

[

'A' tltc.: t im e they'd love to have y ou s tay ' ¼lw'> 1,c.: n sc.:, doc.:s n 't it>

,. hotc.:I e arns incorllL' it w o u lt1n ·1 h:t vL· r>ti'IC made.:, and you s a v <: a ru II 'i0 ' 1/c ,. ......

The b o tto m line is this. Q uest 111<.:mhe~ llnd s pace isavailabk the vast 111:1jority of the t im e. 1\nd you s ave a full 50%1 Al yourspeci:il $ 29.95 Quest 1: lll' you're likL'iv to s:1ve more 1h:1n 1h:rt the very first time you use it!

Try Quest All Year -- Risk Free!

T ,ke Quest on lht: fomily vm:ation. Or a week­end gcW\\'<IY- Try Quest all year. If yo u're IJ.Q!

fullv s:uisfred vou get all your mone y back at :trw time during the life of your members1il; A toll-free phonec1II is all it takes to cancel and gL'I a full refund. •o questions asked .

How Do I Kuow Wbere I Ca11 Stay?

P anicipating Q uest hotel.~ ind ude I lo liday Inns. 1 lilto ns. lkst WeslL'rns. She1:11ons and Cau i-soo-STAY-4-50 and join Quest now!

mon.:1 Vinu:dly e very majo r chain thl'rL' is! And you gel you r own HO-page ho tel di re ctory. Plus every <JOd :1ys you' ll n.:cL'i\·e a n e w hotel dirL·c·tcny a t no extra charge.

Yo ur one-yL":tr d i­rec to ry subscrip tio n is ahs olutL'i y free . 0 1her Q uL·st lllL' 111· h e rs pay S(i.00 ~-x1r.1 fo r th is con ven ient fc.:aturL'. llut through this s pn·ial o ffe r. you gL·t the m FREE!

--- I. SQ a11d 11se yo11r Visa, Master-CAll l-800-STAY-<t- Card or American Express

IVcs! IWantT0JolnQues1I11temational&Save50%0nMyliotdBI&"il I O Ern.:lo.~-tl L._ my ci1t··c:k nr mont:·y onkr for $29.9:J, tnJ.<lt: PJY-J.t:c to •Dt."Stin.uions. Inc.• I I ('rorni: $36_9, ,,;1h a spouse cmd • Please check t,o., below I I O ctmg~ my: O vi."1 o ~fa;i<:tClrd 0Amerk:,n Express I

A -- -----------:-::-Exp. D,ie: / I ct.'ount Number ---..L._ I

Ye,! Send , per.sonalizc'tl Quc,,t C"rd for my ,pou:,e. A,ld s7.00 - T<>1ul; S.lo.95 --r I

II Q spow,,· ' :1111<! _ ____________ it I N

SJgnature _______ _

I ame ---------------=--=--=--=--=--=--:~~--------1 I Address I !City ___ _____ St:1t · ZipCCldc-----1

C.all l-800-782-9450 _ Or mail to: A \Y/5 Quest Offer, One Lllke Aspen Park, I tJ3ccess # 1875-12 l

1

All':'.2·f2cic,~~~~~~ ;!~i~