Study on the mechanism of force calculations in flow forming a review


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Study on the mechanism of force calculations in flow forming a review

  1. 1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME194STUDY ON THE MECHANISM OF FORCE CALCULATIONS INFLOW FORMING: A REVIEW1G Venkateshwarlu, 2K Ramesh kumar, 3T. A. Janardhan Reddy, 4G. Gopi,1Assistant professor, Department of Mechanical Engineering, University college of Engineering,Osmania University, Hyderabad, Andhra Pradesh, India. –500007.2&4Scientist-‘G’ and Scientist-‘D’, Defence research development and laboratory,Hyderabad, Andhrapradesh, India –5000123Professor and Head, Department of Mechanical Engineering, CVR college of Engineering,Hyderabad, Andhrapradesh, India,–500013;ABSTRACTIn metal working industry, flowforming processes is widely used. Flow forming is a metalforming process in which a shorter and thinner ring, called preform, is elongated to a thin and long tubeover a rotating mandrel by means of three rollers. In this method, a hollow axisymmetric preform isaffixed to a mandrel. When the both are made to rotate, compression forces can be applied on theoutside diameter of the preform by hydraulically-driven CNC-controlled rollers. By a premeasuredquantity of wall thickness reduction, in one or more passes, the material is compressed above its yieldstrength, plastically deformed and made to flow. The needed geometry of the workpiece is gained andequipped when the outer diameter and the wall of the preform are reduced and the available materialvolume is forced to flow longitudinally over the mandrel. Typically, the preform can be flowformed upto six times its starting length before a need for reannealing of the metal is required. There are certainparameters like mandrel speed, roller feed, roller geometry etc. which directly affect the dimensionalaccuracy of flow formed component. In connection to these parameters the work piece metallurgicalproperties like hardness variation and grain size variation will have effect on the dimensional accuracyof flow formed components. The inside surface quality of the finished workpiece almost resembleswith the outside surface quality of the mandrel. Flow forming is used to produce rocket nose cones,rocket motor cases, gas turbine components and dish antennas in the aerospace industry. It can also beused to produce power train components and wheels in the automobile industry, gas bottles andcontainers for storage applications. The analysis of flow forming has been undertaken by severalresearchers. Most of the work is on the soft materials like lead, aluminum, low carbon steel, copper etc.A very few authors have tried with the forming process of hard-to-work materials. Concise definitionsINTERNATIONAL JOURNAL OF ADVANCED RESEARCH INENGINEERING AND TECHNOLOGY (IJARET)ISSN 0976 - 6480 (Print)ISSN 0976 - 6499 (Online)Volume 4, Issue 3, April 2013, pp. 194-201© IAEME: Impact Factor (2013): 5.8376 (Calculated by GISI)www.jifactor.comIJARET© I A E M E
  2. 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME195of the research done by other researchers on soft as well as hard-to-work materials is observed andcomprehended here. Advances in process simulation have been spurred essentially by the developmentof general-purpose, finite-element-method (FEM) packges such as DEFORM, ABAQUS, and MSC.Mar are generally applied for the study of elastic-plastic structural problems. The main advantages ofthese methods are that they reduce the computational time, and make possible some degree ofoptimization of the process parameters. This paper presents a study on the various mechanisms of flowforming process and the potential applications of it in defense, automotive and aerospace industries.Index Terms: CNC Flow forming, degree of optimization, Elasto-plastic FEM, Mechanics,Power spinning, Preform, staggered flow forming.NOMENCLATURE= initial thickness (mm)tf= final thickness (mm)f= feed (mm/min)R= roll radius (mm)kc= strength coefficient of materialn= strain hardening coefficientft= tangential force (N)fa= axial force (N)fr= radial force (N)ε= strain(three times of ln(ti/tf))σm1 = Effective and mean effective stressΦ = Reduction angleCS= over roll depth (mm)ρR=roller nose radius(mm)α = half – apex angle of mandrel (deg)= effective stress corresponding to an effective strain cot= outer cone radius= average value of deformation zone angledε= infinitesimal effective strainAt, Ar, Aa = projected areas of the contact surface between roller and cone in the tangential, radial, and axialdirections, respectively.N = speed of rotation of the mandrel, rpmσ = effective stress,σm = mean effective stress.dε = total effective strainα = one half the cone angle, degθo, θo = angle for deformation zone and its average value, respectively, radianθo’,θo’ = angle functionally related to θo and θo respectively, radian1. INTRODUCTIONFlow forming is a relatively new technique which is ideally suited to take the place of the currentforging and machining processes in components like the mortar tube. The flow forming operationbegins with a considerably short and thick-walled hollow cylinder preform.The preform is fit to amandrel with the same diameter as the product. Circumferential rollers rotate axially along the preform,thus cold working the billet, making it thinner and longer, until it has a near net shape to that of thefinished mortar tube. Flow forming produces a highly uniform, round and smooth, surface finish. Theamount of time spent on machining is additionally reduced, which effectively reduces fluidreplacement costs after machining. For most applications three rollers are used.2. CLASSIFICATION OF FLOW FORMING
  3. 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME196The classification of Flow forming process can be done based on two criteria.(i) According to fixing necessities of preform shapes.(ii) According to length of position of rolls during the forming process.2.1. According to fixing necessities of preform shapesFigure.1.Forward Flow forming Figure.2.Backward Flow formingThe First type is forward flow forming (Fig.1) and it is used to form preforms which have ashape with one side is partially closed or fully closed. In forward flow forming, a tailstock is used to fixthe preform to the mandrel. The elongation of the workpiece during forward flow forming is at the samedirection with the relative axial movement of the rollers. Second type of flow forming is backward flowforming (Fig.2) and it is used to form preforms with a constant hole inside. In backward flow forming,a toothed ring is used to fix the preform to the mandrel and it is also used for reloading of the finishedworkpiece. The elongation of the workpiece during backward flow forming is at the opposite directionto the relative axial movement of the rollers. For precision long flow forming operations, typically threerollers placed with 120° design is used. These rollers have precalculated radial and axial offsetsbetween each other to achieve necessary forming conditions shown in (Figs.3,4). The analysis of tubemaking has been adopted by several researchers.Figure.3. the flow form process Figure.4. Offsets of 3-rollers2.2. According to the length of position of rolls during the forming process
  4. 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME1972.2.1. Staggered-Roll Flow Forming ProcessIn the staggered-roll process, three rolls are staggered axially and radially. Each roll has aspecific geometry and job function during the forming process. The three rolls, which are positioned at120ofrom one another moving equally. They are driven by hydraulic force and rotate at the same speedas the mandrel, so that, when they initially contact the preform they are moving at the same speed so asnot to score or gall the preform on initial contact. After the flow forming action is initiated, the rollersare disengaged so that, they spin only by the friction of the rotation of the preform on the mandrel andare then no longer driven by the hydraulic force. The staggered-roll process is used primarily for coldforming, tubular products with thin walls open ends, and closed or semi-closed cylinders on one end.The staggered-roll configuration allows for greater contact surface with the material than that of thein-line process, which keeps the material from belling in front of the rolls and allows for a largerreduction in cross sectional area in one pass. As noted, each roll has a specific geometry and jobfunction. The first roller is predominately responsible for making sure the “wave condition” on thepreform doesn’t fold over and flake. The second roller is predominately responsible for forming thelarge wall reduction. Usually this angle is steeper than the first because, it is not concerned with the“wave phenomena.” This facilitates and maximizes the amount of wall reduction that can be taken inone pass. The last roller does not take as much of a reduction as the second roller, and it is responsiblefor the finish or burnishing of the part. The sharper the leading angle, the better the surface finish willbe on the flow-formed part.2.2.2. In-line Flow Forming ProcessUnlike the staggered-roll method, flow forming with in-line rolls is characterized by either threeor four rolls that are in-line both axially and radially (Fig.6). The rollers also are not independentlydriven as in the staggered roll process, rather than the rollers begin to rotate as they engage the spinningworkpiece.The rollers engage the workpiece at the specified angle and feed rate so as not to creategalling or other dimensional or surface imperfections. Some of the other distinctive characteristics ofthe in-line process are described later in this section. Some of the distinctive characteristics of thein-line process areBoth cold and hot flow-forming processes can be readily used depending on workpiece ductilityand the amount of area reduction taken at each pass.Integral-end fittings or flanges can be rolled on both ends of the tube maintaining taper angles andlinear dimensions consistently during the run without adjustment to the tooling.Springback, straightness, and dimensional distortion are controlled by roll configuration, feed rate,and rate of rotation.The roll arrangement permits self-centering of the component between the rollers, with theprovision that the work is divided equally between the rollers and the forces are perfectly balanced.3. Flow Forming Process DetailsIn flow forming, as shown schematically in Fig.7, the blank is fitted into the rotating mandreland the rollers approach the blank in the axial direction and plasticize the metal under the contact point.In this way, the wall thickness is reduced as material is encouraged to flow mainly in the axial direction,increasing the length of the work piece. The flow of metal directly beneath the roller consists of twocomponents, axial and circumferential.
  5. 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME198Figure.7. Principal of flow forming (deformation zone and forces)If the length of circumferential contact is much longer than the axial contact length, then theaxial plastic flow will dominate the circumferential one. In this case, reduction in thickness willresemble that of plane strain extrusion and a sound product will be produced. On the other hand, ifthe opposite is true, then circumferential flow will dominate leading to high constraint of flow inthe axial direction. This situation will normally give rise to bulges in front of the rollers causingdefects. As the workpiece volume is constant, with negligible tangential flow, the final componentlength can be calculatedAs L1 = L0 S0 (di + S0) /S1 (di +S1) ……………. (1)WhereL1 is the work piece length,L0 is the blank length,S0 is the starting wall thicknessS1 is the final wall thickness,di is the internal diameter.4. MAIN ADVANTAGES OF FLOW FORMINGFlow forming is a chipless, seamless and cold manufacturing processes. Improved materialproperties such as yield strength, fatigue life, etc. Manufacturing capability of very accurate longhollow parts. Preventing secondary operations such as turning, grinding, etc..Highly Precise, seamless construction to net shapesImproved mechanical propertiesTubular, conical & contoured geometryUniform axially-directional, and stable grain micro structureBetter surface finishVery high diameter-to-length ratioRepeatable accuracy part-to-part & lot-to-lot5. TYPICAL APPLICATIONS OF FLOW FORMINGSo=starting wallthicknessS1=Finished wallthicknessL0=Starting Lengthdi=Inside diameterFR=Radial forceFA=Axial forceFT=Tangential forceδ =Trailing angleγ =Leading angler = nose radius
  6. 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME199Fast and economical production rates inclined to other methods various applications are listedTubular- type components i.e., Missile casings, flight and launch motor housings, Rockets andcartridge case.Rocket nose cones, rocket motor cases, gas turbine components and dish antennas in theaero-space Industry.Power trained components and wheels in the Automobile Industry, and gas bottles andcontainers for storage applications.The manufacturing of thin walled tubes and closed and cylinders for the chemical, nuclear,food, pharmaceutical, cryogenic, beverage, filtration and printing Industries.Mass production of small containment vessels for drum packages.Various typical applications are shown in fig.8. Furthermore, flow forming produces a highly uniform,round and smooth, surface finish. Flow forming method also allows achieving high dimensionalaccuracies and required to mechanical properties.Figure.8. Typical flow forming applications6. LIMITATIONS OF FLOW FORMINGFollowing are the limitations of flowformingThe flow forming process is limited to forming radially symmetrical hallow parts such ascones and cylinders.Flow forming reduces the ductility and elongation of the material and spring back may beproblem with some results.Not competitive with deep drawing for long production runs accepting even when counter arecomplexes.Tooling cost for flow forming are lesser than for drawing, but advantage is lost in long runsbecause of longer operation time per piece.7. CONCLUSIONS
  7. 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME200According to the analytical models stated above, most of the researchers have worked on the softmaterials like lead, aluminum, low carbon steel, copper etc. A very few authors have tried with theforming process of hard-to-work materials. A brief description of the work done by other researchers onsoft as well as hard-to-work materials was studied. The studies revealed that more power was consumedwhile working on the hard materials. While working on soft materials observed that the increase inpercentage of reduction, increase in power consumption of radial force and axial force. As the diameterof the roller increases there was increase in power consumption, axial force and the radial force. This isdue to the fact that as the diameter of the roller increases, more volume of the material comes intocontact due to which more power and forces are required.Most of the analytical models developed the tangential force by few authors. This is becausethe tangential force consumes most of the power in the Spinning, and it is thus significantly importantfor the design of spinning machines. From the calculations the tool force based on the assumption thatthe deformation mode in spinning is a combination of bending and shearing. Moreover, by assuminguniform roller contact pressure,Through comparing the finite element simulation results with the Thamasett algorithmcalculation results of spinning forces, the finite element simulation results differ slightly from theThamasett algorithm calculation results of the spinning force measurement experimental results.As review, a result of the flow formed component will have considerably higher mechanical propertiesthan the ones of the starting material. Typically, the preform material is plastically deformed with wallreductions causing a substantial refinement of the grain structure and a total realignment of the grain’smicrostructure in Flow forming method also allows to achieve high dimensional accuracies andrequired mechanical properties.REFERENCES[1] Avitzur B, Yang CT. “Analysis of power spinning of cones”. Journal of Engineering for Industry,Transactions of the ASME 1960; 82:231–45.[2] Kalpakcioglu S. “On the mechanics of shear spinning”. Journal of Engineering for Industry.Transactions of the ASME Series B 1961;83:125–30.[3] Kobayashi S, I.K., Hall, Thomsen EG.“A theory of shear spinning of cones”. Journal of Engineeringfor Industry.Transactions of the ASME 1961; 83:485–95.[4] Hayama M, Kudo H, Shinokura T. “Study of the pass schedule in conventional simple spinning”.Bulletin of the JSME 1970; 13(65).[5]Ram Mohan.T, and Mishra.R., “Studies on power spinning of tubes”, International Journal ofproduct Research, 10,4 Oct. 1972, page (351-64).[6]Chandra Sekharan. N and Venkatesh. V.C., “Theory of Mechanics of flow turning”, Journal ofInstitution of Engineering’s, vol. 57, November 1976.[7] M. Hayama, H. Kudo, “Analysis of diametrical growth and working forces in tube spinning”,Bulletin of Japan Society of Mechanical Engineers 22 (1979) 776–784.[8] T. Wang, Z.R. Wang, Q. Wang, Y. Zhao, S. Wang, “The slipline fields of thickness reductionspinning and the engineering calculation of the spinning forces”, in: Proceedings of the FourthInternational Conference of Rotary Forming, October, 135–139, 1989,pp. 89–93.[9]Thomsett, “ Rotational symmetric of Aluminum” A doctrol dissertation, University of stuggart,West Germany. 1976.[10] Held M. Determination of the material quality of copper shaped charge liners. Propellants,Explosives, Pyrotechnics 1985; 10:125–8.[11] Ming-Der Chena, Ray-Quan Hsua,_, Kuang-Hua Fuhb “An analysis of force distribution in shearspinning of cone” International Journal of Mechanical Sciences 47 (2005) 902–921
  8. 8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME201[12]Sukhwinder Singh Jolly and D.S. Bedi “ Analysis of Power and Forces in the Making of LongTubes in Hard-to-Work Materials ” Proceedings of the World Congress on Engineering 2010 Vol IIWCE 2010, June 30 - July 2, 2010, London, U.K.[13]Yang Yu12, Xu Hongji1 “Finite Element Analysis of Power Spinning and Spinning Force for TubeParts” International Journal of Advanced Science and Technology Vol. 23, October, 2010[14] Dr.R.Uday Kumar, Mahatma Gandhi Institute of Technology, “Mathematical Modeling AndEvaluation Of Radial Stresses In Hydroforming Deep Drawing Process” International Journal OfMechanical Engineering & Technology (IJMET) Volume 3, Issue 2, PP: 693 - 701, ISSN PRINT: 0976– 6340, ISSN ONLINE: 0976 – 6359