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International Journal of Advanced Engineering Research and Science (IJAERS)

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Applicat ion of Finite Element Method inSolidification of Metal during Casting

Rahul Kshetri

1Department of Industrial & Production Engineering

Abstract—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 nontransient 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 between the casting and the mold plays a vital role. This work attempts 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. 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 patterned after the part to be manufactured, second allowing it to solidify, and finally removpart 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 components and power trains, agricultural and railroad equipment, pipes and plumbing fixtures, power-tool housings, gun barrels, frying pans, jewellery, orthopaedic implants, and very large components for hydraulic turbines. For the production of good-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:


ion of Finite Element Method inSolidification of Metal during Casting

Rahul Kshetri1, Dheeraj Gunwant2

Department of Industrial & Production Engineering, Department of Mechanical EngineeringUttarakhand, India

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 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

transfer between the casting is work attempts 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

is solidifying. ANSYS software has been used to obtain the temperature distribution in the casting process by performing Transient Thermal Analysis.

ANSYS, Casting, Solidification, Finite

desired geometry of component

Metal casting is one of the direct method. Basically three step involves in casting process first pouring molten metal

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

d applications to meet specific design requirements. By casting process a large variety of components and parts are made, such as engine blocks, crankshafts automotive components and power trains, agricultural and railroad equipment, pipes and plumbing

tool housings, gun barrels, frying pans, jewellery, orthopaedic implants, and very large

quality and economical castings a good understanding of the underlying science is

Casting rejections are a major concern in foundry industries which can be avoided by applying

A. FLOW OF THE MOLTENMOULD 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 moTemperature are the main variables that affect the fluidity of the metal and that are inherent to the metal itself , chemical composition, superficialviscosity of the cast metal, pressure, as well as the thermal diffusivity of the momould permeability. B. SOLIDIFICATION AND

METAL IN THE MOULDSeveral factors influencing the Solidification and of metals in the mould , including the metallurgical and thermal properties of the metal. After molten metal is poured into a mould, 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 grainsformed throughout the casting, which in turn influencesthe overall properties of the affecting these events are the type of metal,properties of both the metal and the morelationship 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 moldSolidification of metal stakes place through nucleation and growth of the solid phase under favourable thermal conditions [2-4]. Nucleation is followed by growth of the solid phase, whose development depends on the thermal

[Vol-3, Issue-2, Feb- 2016]

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ion of Finite Element Method in Solidification of Metal during Casting

Engineering, G.B.P.U.A.T., Pantnagar,

MOLTEN METAL INTO THE

uidity: the capacity to fill the mould i.e., the ability of low through the feed heads and

passages and filling all the interstices of the mould. Temperature are the main variables that affect the fluidity of the metal and that are inherent to the metal itself ,

composition, superficial oxide films, the iscosity of the cast metal, pressure, as well as the

thermal diffusivity of the mould, its hot tops, feeders and

AND COOLING OF THE

MOULD Several factors influencing the Solidification and cooling

ld , including the metallurgical and properties of the metal. After molten metal is

ld, a series of events takes place during the solidification of the metal and its cooling to ambient

events greatly influence the size, shape, uniformity, and chemical composition of the grains

casting, which in turn influences metal. The significant factors

affecting these events are the type of metal, the thermal properties of both the metal and the mould, the geometric relationship between volume and surface area of the casting, and the shape of the mold.

Cast structures of pure metal solidified in a square mold stakes place through nucleation

and growth of the solid phase under favourable thermal 4]. Nucleation is followed by growth of the

solid phase, whose development depends on the thermal


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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 walls, with grain growth taking place toward the center of the cast part 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 solidinterphase. Lateral growth is restricted by competitive growth, resulting in the formation of columnelongated grains growing in the direction of the thermal flow[5]. Some of the common defects shown in fig.2 occulack 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 of the cast object due to compressive stress generated during solidification. This compressive stress is governed by many factors of motopology. Compressive stress generated during solidification of casting can be controlled by mold thickness, mould materials, combination of different mould materials and layer thickness, draft angle etc. So, before taking decision on above parameters it is needeknow the stress distribution of cast object after solidification. Choudhariet al. 2013 perform modelingwith 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 of the last freezing


conditions during solidification and on the alloy tion. 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

al nucleation on ld’s walls, with grain growth taking place toward

the center of the cast part shown in fig. 1. Nucleated grains with the most favourable orientation grow preferentially, advancing toward the bulk of the casting

tion of atoms in the solid-liquid interphase. Lateral growth is restricted by competitive growth, resulting in the formation of column-like and elongated grains growing in the direction of the thermal

Some of the common defects shown in fig.2 occur due to lack of information about solidification time during

Defects during casting solidification

MOULD

Mould type also has an important influence, because it casting of an object many

problems are raised during solidification. One of these problems is internal cracks of the cast object due to compressive stress generated during solidification. This compressive stress is governed by many factors of mould

y. Compressive stress generated during solidification of casting can be controlled by mold

ld materials, combination of different 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

modeling and simulation with Experimental Validation of Temperature Distribution during Solidification Process in Sand Casting

tion of the solidification process enables visualization of the progress of freezing inside a casting and identification of the last freezing

regions or hot spots [6].Gopinathand 2012 optimize the riser size by ANSYS simulationAnother Numerical Simulation on Heat Transfer during the Solidification of Pure Iron in Sand and Mulliteis performed by Pariona and Mossithat cooling in the sand system was slower than in the mullite system. This fact caused a larger thethermal 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

II. MATERIALSWhen 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 tempeachieves 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 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 represents the approximate behavior of the solution.

Fig. 3: Casting Model in 3


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Gopinathand Balanarasimman optimize the riser size by ANSYS simulation [7].

Numerical Simulation on Heat Transfer during the Solidification of Pure Iron in Sand and Mullite Molds

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

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.

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

The finite element method (FEM) is a numerical method, hich 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

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 represents the approximate

Casting Model in 3-D


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Fig. 4: Symmetry of the casting and mold 2

Casting model design shown in fig.3 made of steelhas homogeneous and isotropic characteristics. The geometry of the cast part was designed together withsand mould. 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 nonlinearavoid overloading the computer’s capacity. However, in this work the analysis was made for half symmetry in 2D, which is illustrated in Fig. 5.

Fig. 5: Half Symmetry of the casting and modifferent points at different locations

III. FINITE ELEMENT ANALYSIS

In order to generate the system of equations, as well as tofind the result at each point of the cast part, a mesh wasgenerated 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 achieANSYS 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 then applied to the symmetry of the parts.


Symmetry of the casting and mold 2-D

Casting model design shown in fig.3 made of steel which and isotropic characteristics. The

geometry of the cast part was designed together with the ld. This geometry is illustrated in Fig. 4, which

represents the symmetry. The symmetry was used in order the number of grid points, i.e., to facilitate the

nonlinear equations and capacity. However, in

was made for half symmetry in 2-

Half Symmetry of the casting and mould with

different points at different locations

ANALYSIS 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

order to achieve this, the control of the size and

obtain the most precise solution. Cast metal (steel), sand properties and initial and boundary conditions (given in the table I) were then

Fig. 6: The mesh in the Symmetry of the casting and mo

Table.1: Information f

Coordinates of Points on Metal Casting and Sand Mo

Point 1 (16,6,0) Point 2 (14,8,0) Point 3 (18,4,0) Point 4 (12,10,0) Element type

Properties of Steel

Temperature (0F) Enthalpy (Btu/inch3)

0 0 2643 128.12750 163.82875 174.2

Properties of Specific Heat

(Btu-0F) Conductivity (hr-

0.28 0.025Initial and Boundary Conditions

Temperature of steel

Temperature of sand

Heat transfer coefficient 0.14

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


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The mesh in the Symmetry of the casting and

mould

for Finite Element Analysis

Coordinates of Points on Metal Casting and Sand Mould

Point 5 (20,2,0) Point 6 (2,6,0) Point 7 (5,10,0) Point 8 (11,2,0)

Quad 4node 55

Properties of Steel Enthalpy (Btu/inch3)

Conductivity (hr-inch-0F) 1.44

128.1 1.54 163.8 1.22 174.2 1.22

Properties of Sand Mold Conductivity

-inch-0F) Density

(lb/inch3) 0.025 0.54

Initial and Boundary Conditions

2875 0F

80 0F

0.14 (Btu/ (hr-inch2-0F)

& 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

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

International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-3, Issue-2, Feb- 2016]

ISSN: 2349-6495

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after 4 hours. In 4 hours maximum temperature of metal vary from 2875 to 1926 0F.

Fig. 7: Temperature profiles during casting

solidification after 1.14 hour


solidification after 2.14 hours


solidification after 3.14 hours


solidification after 4 hours

Fig. 11: Variation of temperature with time at different

points in cast metal

Fig. 12: Variation of temperature with time at different

points in sand mould 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.

International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-3, Issue-2, Feb- 2016]

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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.

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, 23-29.

[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, 32-38.

[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

the Brazil Society of Mechanical Science & Engineering,2005, Vol. 27, 399-406.

[9] Handbook ANSYS 12, ANSYS, Inc.

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