International Journal of Advanced Engineering Research and Science (IJAERS)
[Vol-3, Issue-2, Feb- 2016] ISSN: 2349-6495
Application ion of Finite Element Method in Solidification of Metal during Casting Rahul Kshetri1, Dheeraj Gunwant2 Department of Industrial & Production Engineering, Department of Mechanical Engineering,, G.B.P.U.A.T., Pantnagar, Uttarakhand, India Abstract—The The process of solidification is complex in nature and the simulation of such process is required in industry before it is actually undertaken. It is a non-linear non transient phenomenon, posing a challenge in terms of modelling and analysis. Finite element method is used to simulate the heat transfer process accompanying the solidification process. During the solidification of a casting in a mold, the heat-transfer transfer between the casting and the mold plays a vital role. This work attempts a to study heat flow within the casting, as well as from the casting to the mold, and finally obtains the temperature history of all points inside the casting. The most important instant of time is when the hottest region inside the casting is solidifying. fying. ANSYS software has been used to obtain the temperature distribution in the casting process by performing Transient Thermal Analysis. Keywords—ANSYS, Casting, Solidification, Finite Element Method I. INTRODUCTION For manufacturing the desired geometry of component Metal casting is one of the direct method. Basically three step involves in casting process first pouring molten metal into a mould ld patterned after the part to be manufactured, second allowing it to solidify, and finally removing the part from the mould. The first metal castings were made during the period from 4000 to 3000 B.C., using stone and metal moulds for casting copper [1]. Various casting processes have been developed over time, each with its own characteristics and applications to meet specific design requirements. By casting process a large variety of components and parts are made, such as engine blocks, crankshafts automotive otive components and power trains, agricultural and railroad equipment, pipes and plumbing fixtures, power-tool tool housings, gun barrels, frying pans, jewellery, orthopaedic implants, and very large components for hydraulic turbines. For the production of good-quality quality and economical castings a good understanding of the underlying science is essential. Casting rejections are a major concern in foundry industries which can be avoided by applying proper knowledge of the follows: www.ijaers.com
A. FLOW OF THE MOLTEN METAL INTO THE MOULD CAVITY Fluidity: the capacity to fill the mould i.e., the ability of the cast metal to flow through the feed heads and passages and filling all the interstices of the mould. mo Temperature are the main variables that affect the fluidity of the metal andd that are inherent to the metal itself , chemical composition, superficial oxide films, the viscosity of the cast metal, pressure, as well as the thermal diffusivity of the mould, mo its hot tops, feeders and mould permeability. B. SOLIDIFICATION AND COOLING OF THE METAL IN THE MOULD Several factors influencing the Solidification and cooling of metals in the mould ld , including the metallurgical and thermal properties of the metal. After molten metal is poured into a mould, ld, a series of events takes place during the solidification of the metal and its cooling to ambient temperature. These events greatly influence the size, shape, uniformity, and chemical composition of the grains formed throughout the casting, which in turn influences the overall properties of the metal. The significant factors affecting these events are the type of metal, the thermal properties of both the metal and the mould, mo the geometric relationship between volume and surface area of the casting, and the shape of the mold.
Fig. 1:
Cast structures of pure metal solidified in a square mold Solidification of metal stakes place through nucleation and growth of the solid phase under favourable thermal conditions [2-4]. 4]. Nucleation is followed by growth of the solid phase, whose development depends on the thermal Page | 42
International Journal of Advanced Engineering Research and Science (IJAERS) conditions during solidification and on the alloy composition. When the temperature is reduced uniformly throughout the liquid, extensive random nucleation occurs throughout the liquid. However, the practical conditions of heat flow promote the formation of temperature gradients in the liquid, which induce initial nucleation on the mould’s ld’s walls, with grain growth taking place toward the center of the cast part rt shown in fig. 1. Nucleated grains with the most favourable orientation grow preferentially, advancing toward the bulk of the casting by progressive deposition of atoms in the solid-liquid solid interphase. Lateral growth is restricted by competitive growth, resulting esulting in the formation of column-like column and elongated grains growing in the direction of the thermal flow[5]. Some of the common defects shown in fig.2 occur due to lack of information about solidification time during casting.
Fig. 2:
Defects during casting solidification
C. INFLUENCE OF THE TYPE OF MOULD MATERIAL Mould type also has an important influence, because it affects the rate of cooling. In casting of an object many problems are raised during solidification. One of these problems is internal cracks off the cast object due to compressive stress generated during solidification. This compressive stress is governed by many factors of mould mo topology. Compressive stress generated during solidification of casting can be controlled by mold thickness, mould materials, combination of different mould ld materials and layer thickness, draft angle etc. So, before taking decision on above parameters it is needed to know the stress distribution of cast object after solidification. Choudhariet al. 2013 perform modeling and simulation with Experimental Validation of Temperature Distribution during Solidification Process in Sand Casting and they conclude that simulation of the solidification process enables visualization of the progress of freezing inside a casting and identification entification of the last freezing www.ijaers.com
[Vol-3, Issue-2, Feb- 2016] ISSN: 2349-6495
regions or hot spots [6].Gopinathand Gopinathand Balanarasimman 2012 optimize the riser size by ANSYS simulation [7]. Another Numerical Simulation on Heat Transfer during the Solidification of Pure Iron in Sand and Mullite Molds is performed by Pariona and Mossi 2005 and concluded that cooling in the sand system was slower than in the mullite system. This fact caused a larger thermal flow and thermal gradient in the sand system than in the mullite system [8]. In this work a finite element analysis is performed with the help of ANSYS to obtain the temperature history of all points inside the casting, plot the progress of solidification fronts (isothermal contours) at different instants of time, and identify the last freezing regions. II. MATERIALS AND METHODS When the molten metal is poured into the mould cavity, it releases large amounts of heat in a very short period of time and raising the temperature of the mould in a flash. After a period of time, the temperature of the mould achieves a relative balance point (during solidification & cooling process). Heat transfer during this process is an unsteady problem which can be solve by finite element method. The finite element method (FEM) is a numerical method, which can be used for accurate solution of complex engineering problems. Finite element analysis (FEA) is the method of dividing a large body into small parts called ‘elements’, connected at predefined points called nodes. Element behaviour is approximated in terms of the nodal variables called the DOFs.Elements are assembled with due consideration of loading and boundary conditions. In the analysis results are obtain from finite number of equations which ch represents the approximate behavior of the solution.
Fig. 3:
Casting Model in 3-D 3
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International Journal of Advanced Engineering Research and Science (IJAERS)
Fig. 6:
Fig. 4:
Symmetry of the casting and mold 2-D 2
Casting model design shown in fig.3 made of steel which has homogeneous and isotropic characteristics. The geometry of the cast part was designed together with the sand mould. ld. This geometry is illustrated in Fig. 4, which represents the symmetry. The symmetry was used in order to reduce the number of grid points, i.e., to facilitate the computation of the system of nonlinear equations and avoid overloading the computer’s capacity. However, in this work the analysis was made for half symmetry in 22 D, which is illustrated in Fig. 5.
Fig. 5:
Half Symmetry of the casting and mould mo with different points at different locations
III. FINITE ELEMENT ANALYSIS In order to generate the system of equations, as well as to find the result at each point of the cast part, a mesh was generated throughout the area of each part as shown in fig. 6. The geometrical unit of each mesh element must fit the geometry of the part. In order to achieve this, the ANSYS program allows for control of the size and geometry of the mesh in order to obtain the most precise solution. Cast metal (steel), sand properties and initial and boundary conditions (given in the table I) were w then applied to the symmetry of the parts.
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[Vol-3, Issue-2, Feb- 2016] ISSN: 2349-6495
The mesh in the Symmetry of the casting and mould
Table.1:
Information for Finite Element Analysis
Coordinates of Points on Metal Casting and Sand Mo Mould Point 1 (16,6,0) Point 5 (20,2,0) Point 2 (14,8,0) Point 6 (2,6,0) Point 3 (18,4,0) Point 7 (5,10,0) Point 4 (12,10,0) Point 8 (11,2,0) Element type Quad 4node 55
Properties of Steel Enthalpy Conductivity Temperature (0F) (Btu/inch3) (hr-inch-0F) 0 0 1.44 2643 128.1 1.54 2750 163.8 1.22 2875 174.2 1.22 Properties of Sand Mold Specific Heat Conductivity Density (Btu-0F) (hr--inch-0F) (lb/inch3) 0.28 0.025 0.54 Initial and Boundary Conditions Temperature of steel 2875 0F Temperature of sand 80 0F Heat transfer coefficient 0.14 (Btu/ (hr-inch2-0F) IV. RESULTS & DISCUSSIONS In this study, For non linear case an analysis of heat transfer for the casting process in two dimensions are made. During four hours of solidification to determine the distribution of temperature, thermal gradient, cooling curves in the cast metal, and heating curves in the moulds when casting process of steel in sand moulds happened. Fig. 1 to 4 represents the temperature contour during the solidification at 1.14 hours, 2.14 hours, 3.14 hours and Page | 44
International Journal of Advanced Engineering Research and Science (IJAERS)
[Vol-3, Issue-2, Feb- 2016] ISSN: 2349-6495
after 4 hours. In 4 hours maximum temperature of metal vary from 2875 to 1926 0F.
Fig. 10: Temperature profiles during casting solidification after 4 hours Fig. 7:
Temperature profiles during casting solidification after 1.14 hour
Fig. 11: Variation of temperature with time at different points in cast metal Fig. 8:
Temperature profiles during casting solidification after 2.14 hours
Fig. 12: Variation of temperature with time at different points in sand mould Fig. 9:
Temperature profiles during casting solidification after 3.14 hours
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In Fig. 10 at points 1,2 and3 the cooling curves inside the cast metal in the sand mould is presented. initially all the points are at same temperature (2875 0F) It is clear from the figure and cooling at point 3 is faster than others however behaviour at point 1 and 2 is approximately for given solidification time. Page | 45
International Journal of Advanced Engineering Research and Science (IJAERS) Fig. 11 shows at different points the variation of temperature with time in the sand mould. Cause of large heat rejection by molten metal, temperature of sand mould increases and heating curves are shown in figure at different locations. Point 4 is the most critical location during casting it is clear from the figure it is due to symmetry of the casting. Chills can be used at that position to increase heat transfer rate.
[Vol-3, Issue-2, Feb- 2016] ISSN: 2349-6495
the Brazil Society of Mechanical Science & Engineering,2005, Vol. 27, 399-406. [9] Handbook ANSYS 12, ANSYS, Inc.
V. CONCLUSIONS Present work is an attempt to casting simulation using ANSYS has been carried out to obtain the temperature variation with time at different points. 1. ANSYS provides an effective way to study the solidification of different materials under different mold designs and materials. 2. Details of temperature variations in cast metal are an important factor in improving the casting quality, reduced cost of development and speeding up the improvement of the product. 3. Variation of temperature with time at different points in sand mould, enable the designer to select correct size of the mould, positions for chills. REFERENCE [1] Kalpakjian S. and Schmid S.R. “Manufacturing Engineering and Technology” Prentice Hall, 2010 [2] Pariona, M.M., Bolfarini, C., Dos Santos, R.J. and Kiminami, C.S., “Application of Mathematical Simulation and Factorial Design Method to the Optimization the Atomization Stage in the Forming of a Cu-6% Zn Alloy”, Journal of Materials Processing Technology,2000, vol.102, 221-229. [3] Campbell, J., “Casting”, Butterworth-Heinemann, Oxford, 1991. [4] Flemings, M.C., “Solidification processing”, McGraw-Hill, 1974. [5] Ghosh A. and Mallik A.S., “Manufacturing science” EWP, 2006 [6] Choudhari C.M., Narkhede B.E., Mahajan S.K., “Modeling and Simulation with Experimental Validation of Temperature Distribution during Solidification Process in Sand Casting”, International Journal of Computer Applications, 2013, vol.16, 2329. [7] Gopinath V., Balanarasimman N., “Effect of Solidification Parameters on the Feeding Efficiency of Lm6 Aluminium Alloy Casting”, IOSR Journal of Mechanical and Civil Engineering, 2012, Vol. 4, 3238. [8] Pariona M.M. and Mossi A.C., “Numerical Simulation of Heat Transfer During the Solidification of Pure Iron in Sand and MulliteMolds” Journal of www.ijaers.com
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