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Borovik P.V.
3D MODEL OF CUTTING BY ROLLING CUT TYPE SHEARS
Abstract. 3D model of rolling cut process by shears on the base of finite element method is developed and dependence of maximum cutting force on the knife curve radius is detected. Suggestions directed to increase of productivity of shears are recommended.
Keywords: shears, rolling cut, curved knife, cutting force.
Separation operations are widely used in rolling production and establish quality and cost price of metal products. One of such separation operations is thick sheet cutting using the rolling cut type shears [1, 2].
Rolling cut is used for longitudinal and sectional cutting of sheets. With this type of cutting one can almost avoid deformation of cutting edge at circulated shear movement [1, 2].
As experience shows, at rolling cut a dependence of cutting force on the starting point of the cutter going into metal has got apparent peak (Fig. 1,b) that can be explained by less value of cutting angle. Because of various model shears difference between maximum and fixed cutting force can be about 30...60%. This fact helps in increasing shears metal content.
a.
b
Fig. 1. Scheme for rolling cut (a) and specific dependence of cutting force (b)
There are technical decisions known [3, 4] that tend to reducing the peak loads during rolling cut which is made by changing the shears design. But such approach has low technical efficiency during manufacturing.
In present days due to advanced computational tools and progress in theoretical researches simulation techniques for different pressure treatment technological processes aiming to their thoroughly studying and improvement are widely used.
Therefore, to give full image of rolling cut process it is necessary to use modern theoretical approaches and methods among which finite element method (FEM) has got a special role [5, 6].
The purpose of this work is to develop 3D model of rolling cut process on the base of finite element method and detect factors affecting the cutting force value.
To get to the purpose set theoretical researches have been made using AbAquS software. 3D model has been developed for this describing cutting process of sheets with curved knife on the shears with rolling cut in Lagrange formula using ALE (Arbitrary Lagrangian Euleri-an) mesh adaptation and including gravity.
A model (Fig. 2) is for extremely hard analytical rigid body - a holder, a Table, upper curved and lower stationary knife, as well as deformable beam as a model of sheet being cut.
And as an analog to real design of rolling cut type shears a motion is transmitted to upper curved knife along the specific trajectory and to the Table in vertical direction while the lower knife and a holder are fixed.
Deformable beam is a mesh of isoparametric an 8-node linear brick elements with reduced integration scheme and hourglass control, having the features of entire deforma-ble material. Mesh configuration is irregular getting compacting in the shearing zone (Fig. 3).
Friction between contact surfaces models Coulomb's friction law. Herewith, constant of friction is fixed and characterizes the relation between contact pressure and equivalent shear stress.
Material fracture was simulated using a method of elimination of elements from the calculations after the ductility resources were over in accordance with ductility curve [6].
Fig. 2. General view of cutting process simulation for sheets using curved knife on rolling cut type shears
Borovik P.V.
So, further researches have been directed to reveal the possibilities of reducing such gap.
Fig. 3. Initial mesh configuration
For simulating in cutting processing they used steel grade St2ps. Sheet depth is 50 mm, width - 2500 mm.
On the first study stage through famous methods [1,2,7] calculations of kinematic operation parameters of shears have been made. Two-crank shears from NMBW (Novokramatorsk Machine - Building Works) has been taken as a model. Fig. 4 shows the calculated trajectory for reference point which afterwards has been put into a model for simulating the upper knife motion.
In the studied model of rolling cut type shears a radius of curved knife in the initial point is 47m, and a clearance between knives in the initial point is 148 mm. Fig. 5 shows the simulation results.
As you can see from the results presented the maximum cutting force is ~1,6 times more than steady cutting.
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Fig. 4. Path the reference point of upper knife
In this way they changed the radius of knife curve at constant clearance between the knives and kinematics of system movement. The results revealed that increasing the knife radius promotes reducing the force in the starting cutting moment and its simultaneous raise at the end of cutting (Fig. 6, a). Basing on the results achieved the dependence of maximum cutting force on the knife curve radius was obtained (Fig. 6, b).
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—
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V
Angle
d
Fig. 5. Simulation results: a - knife position in moving of cams to 99°; stress-strained state of sheet in the same position; c - configuration after full separation of the sheet;
d -cutting force ( N x mm ) dependence on rotation angle of cams
b
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Fig. 6. Effect of knife curve radius to cutting force: a - specific dependences of cutting force in increasing knife curve radius; b dependence of maximum cutting force on knife curve radius
According to the results of the work one can summa- 6.
rize:
- technological opportunities of rolling cut type shears are not always used in full volume due to large 7. (about 60%) divergence between maximum cutting force and its steady value;
- increasing the knife curve radius to certain value provides more even distribution of force during cutting process and then its visible growth on knife coming out of cut;
- applied to the given shears design at cutting the sheets with maximum depth 50 mm knife curve radius 80...200 meters allows to obtain more stable force distribution during the cutting process;
- in given conditions maximum cutting force relatively to curve radius of 47 m reduces for 25.30 %, that indicates to real opportunity to increase the range of cut sheets.
The results of the work can be used for practical application and during research and development of cutting process for rolling cut type shears.
References
1.
Korolev A.A. Konstrukcija i raschet mashin i mehanizmov prokatnyh stanov. [Design and calculation of rolling mill machinery]. Moscow : Metallurgija, 1985. 376 p. Ivanchenko F.K., Grebenik V.M., Shirjaev V.I. Rozrahunok mashin i mehanizmivprokatnih cehiv. [Machinery calculating for rolling mills]. Kiev: Vishha shk., 1995. 455 p. Adamovich R.A., Rudel'son L.M., Rogoza A.M., Pal'min A.D. Nozh dlja listovyh nozhnic s katjashhimsja rezom. [Knife with rolling cutter for sheet shears]. A.s. USSR, no. 810403, 1981.
Adamovich R.A., Rudel'son L.M., Rogoza A.M., Pal'min A.D. Nozh dlja nozhnic s katjashhimsja rezom. [Knife shears with rolling cutter]. A.s. USSR, no. 902989, 1982. Liu G.R., Quek S.S. The Finite Element Method: A Practical Course, 2003, 348 p. Borovik P.V., Usatjuk D.A. Novye podhody k matematicheskomu mod-elirovanju tehnologicheskih processov obrabotki davleniem. [New approaches to the mathematical modeling of pressure treatment processing]. Alchevsk : DonGTU, 2011. 299 p.
Notchenko V.D, Bojdenko A.N., Emchenko E.A., Cherkasov N.D., Zozulja E.S., Poslushnjak A.V. Chislennoe matematicheskoe modelirovanie processa rezanija listovogo metalloprokata na nozhnicah s dugoobraznym nozhom. [Numerical mathematic process simulation of sheet metal cutting with shears with embowed knife]. Udoskonalennja procesiv i obladnannja obrobki tiskom v mashinobuduvanni i metaiurgti: temat. zb. nauk.. pr. [Pressure treatment processing and machinery improving in machine building and metallurgy: Col.of Scient Papers]. Kramators'k, 2001. pp. 454-457.
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Gribkov E.P., Danilyuk V.A.
MATHEMATICAL MODELLING OF SRTESS-STRAIN BEHAVOIR IN ROLLING OF THE COMPOSITIONS INCLUDING POWDER MATERIALS
Abstract. The developed mathematical model of rolling of two-layer powder materials allows to determine the rational technological parameters of process excluding deformation of a substrate and raising an exit of suitable by production of inserts of sliding bearings. It is established that the less thickness of a metal substrate, the more subjects is deformed, and respectively, powder is less deformed. In increasing the layers ratio the force and the rolling moment growing and the increasing of final relative density of powder composition are observed.
Keywords: mathematical model, rolling, powder materials, substrate, relative density, deformation center.
One of the perspective directions in the field of composite hardware production is rolling of compositions with using the powder materials, allowing to receive wide assortment of production with simultaneous ensuring specific operational properties and simultaneous economy of extremely scarce and expensive materials. The most widespread ways of rolling of such type production is rolling of compositions powder-powder and powder-monometal.
The mathematical model of rolling single-layer pow-
der materials [1] was taken as a principle of numerical mathematical model of rolling of two-layer powder materials. The settlement scheme of the integrated deformation center used in this case is submitted in figures 1 and 2.
Splitting of a consolidation zone into a final set of elementary volumes and definition of geometrical characteristics, and also tensions Ox, Tx and px in a final and differential form (Fig. 2) was carried out by analogy to a technique stated in work [1].
