Your SlideShare is downloading. ×
Experimental and theoretical study of the influence of the addition of alumina powder
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Experimental and theoretical study of the influence of the addition of alumina powder

379

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
379
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
26
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. INTERNATIONAL Mechanical Engineering and Technology (IJMET), ISSN 0976 – International Journal of JOURNAL OF MECHANICAL ENGINEERING 6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME AND TECHNOLOGY (IJMET)ISSN 0976 – 6340 (Print)ISSN 0976 – 6359 (Online) IJMETVolume 3, Issue 3, September - December (2012), pp. 412-428© IAEME: www.iaeme.com/ijmet.asp ©IAEMEJournal Impact Factor (2012): 3.8071 (Calculated by GISI)www.jifactor.com EXPERIMENTAL AND THEORETICAL STUDY OF THE INFLUENCE OF THE ADDITION OF ALUMINA POWDER TO 7020 ALUMINUM ALLOY FOAM ON THE MECHANICAL BEHAVIOR UNDER IMPACT LOADING ArkanJawdat Abassa1, DhaferSadeq Al-Fatal2 1 (Department of machines and equipment Engineering/ University of Technology, Baghdad, Iraq, arkan_abassa@yahoo.com). 2 (Department of machines and equipment Engineering/ University of Technology, Baghdad, Iraq, alfattal40@yahoo.com). ABSTRACT Aluminum foams are new materials mainly produced by expansion in proper chambers. A relevant quantity of voids is generated in the metallic matrix during manufacturing, resulting in a low material density. Aluminum foams are strongly affected by cells size, cells shape, foam density, weight fraction and types of additives to aluminum foam. In this paper, the influence of particle size, and weight fraction of Al2O3 particles on impact behavior of 7020 aluminum alloy foam was investigated, and then modeled using ANSYS12 software. Three- dimensional models are suggested to model aluminum foam structure under impact loading. Experimental results showed that the increase of the weight fraction of alumina powder as reinforcement raises the acceleration-time curves. The decrease of alumina particle size leads to an increase in the acceleration-time response of aluminum foam. Theoretical results of the models are in good agreement with the experimental acceleration-time, velocity-time and displacement-time curves of 7020 aluminum alloy foam. Keywords: Impact loads, Aluminum foam, Alumina particles, aluminum foam models, Calcium carbonate. I. INTRODUCTION Metal foams are new, as yet imperfectly-characterized, class of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties[1]. They offer potential for light-weight structures, for energy absorption such as crash boxes in automobiles, for thermal management such as heat insulation or heat exchangers according to cells type, and for acoustic absorption such as sound insulation, and some of them, at least, are cheap. Metal foam is a cellular solid, just like wood, coral, bone and bread, but with the cells made out of metal. Usually the metal is an aluminum alloy, but it can also be made of 412
  • 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEother metals, for example steel, nickel, titanium or gold [2]. In other words, metal foamsaresolids with high fraction of porosity.Metallic foams are generally divided into two types, open and closed cell microstructures. Inthe open-cell foam the cells are interconnected and the foam has the same appearance as ascouring pad. The connections in open-cell foam are called struts, which meet in nodes. Forclosed-cell foams the cells are closed by so-called faces, which meet in so-called cell edges,which in turn meet in nodes. Generally, closed cell microstructures have higher mechanicalstrength than open cell microstructures. The closed cell type of microstructure is particularlyattractive for applications in the field of light weight construction and energy absorption.II. EXPERIMENTAL WORKAll foams made in this work were prepared by using 7020 aluminum alloy with the chemicalcomposition shown in table (1). A calcium carbonate CaCO3 powder, as a blowing agent,with particle size of less than 10 µm and weight fractions (2%) was used to generate poresinside the aluminum alloy.Many significant factors affect the use of CaCO3 powder instead of TiH2 powder as blowingagent. The main factors are 1- Calcium carbonate is cheap as compared with TiH2 as blowing agent[3]. 2- The density of CaCO3 is (2.71 to 2.83 gr/cm3), almost identical to the density of molten aluminum. Moreover, its decomposition temperature is above the melting point of aluminum, usually in the temperature interval between 660 °C and 930 °C. Therefore, CaCO3 is particularly suitable for the melt-route settling-free production of foamed aluminum based materials. 3- The use of CaCO3 was found to be potentially suitable as a foaming agent for direct (melt-route) foam manufacturing. Moreover, the decomposition products of CaCO3 have a significant effect on foam stabilization [4].In this work, 7020 aluminum alloy foams were produced with different weight fraction ofalumina particles (0%, 2% and 4%) as reinforcement. The alumina particles were prepared bysieving them to multi sizes of 90-106 µm, 106-125µmand 125-150 µm. An electrical furnacewas setto a temperature of 800ºC to melt the7020 aluminum alloy by using a graphitecrucible.Alumina particles with specific particle size and weight fraction were added to the melt of7020 aluminum alloy at a temperature of 800ºC. An electrical stirrer was used to mix thealumina particles inside the melt of aluminum for about one minute. This melt was turnedback to the furnace to rise up its temperature, and this process was repeated three times until agood distribution of alumina particles inside the melt of aluminum was achieved. Calciumcarbonate was added to the melt with 2% weight fraction, and again the stirrer was used toget a good distribution of the blowing agent particles inside the melt of aluminum. Thismixture was turned back to the furnace but this time at a temperature of 740ºC for about 15minutes to get a 7020 aluminum alloy foam reinforced with alumina powder. Aluminumfoam samples have a cylindrical shape with a diameter of 50.24mm, and a height of 44mm,as shown in fig. 1. 413
  • 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEAll aluminum foam samples are impacted by a drop weight, as shown in fig. 2. An aluminumfoam specimen was put on the solid base. A block which weighs 0.71 kg was let free to fallonto the foam sample from a height of 1 m. This represents 6.965 J of kinetic energy atimpact. In the center of the block, a one axis accelerometer, type B&K 4370, was installed.Electrical signals were generated by the accelerometer at the moment of impact. Thesesignals were sent to the charge conditioning amplifier, type B&K 2626 for amplification, andwere displayed by data storage oscilloscope, type ADS 1022C, 25MHz. This test involves adynamic load being applied to a cylindrical shape specimen. The impact load has a velocityof 4.429 m/sec at impact moment. After impact, specimen’s deformation was measured, andby using equation (10), the maximum force and the acceleration exerted by the impactor canbe calculated. TABLE I Chemical composition of 7020Si % Fe % Cu % Mn Mg Cr % Ni % Zn % Ti % P% Pb % Sn % V% Zr % Al % % %0.127 0.168 0.084 0.084 0.95 0.24 0.001 4.03 0.041 0.001 0.001 0.001 0.008 0.129 Bal -A- -B- -C- Fig. 1: A- 7020 aluminum alloy foam samples, B-side view, C- Top view. Fig. 2: Drop weight tester machine 414
  • 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEIII. THEORETICAL ANALYSISA drop weight test of aluminum foam samples can be modeled, as shown in fig.3. A weightW is released from rest at a height of h above an aluminum foam sample with cross sectionalarea A, and a length L. The aluminum foam sample is modeled as a spring with stiffness kand a mass Wb. Fig. 3: Vertical beam (aluminum foam sample) under impact [5]This model can be solved by the application of the law of conservation of energy to thesystem.The kinetic and potential energy are illustrated in equations at the start, when the block is atrest above the spring at height h, and at the end, when the block is at its lowest point.At the start, Kinetic energy=0 Potential energy= W (h). where W=mg, and h= height.At the bottom, ଵௐ ଶKinetic energy= ଶ ௚ ‫ݒ‬௛By equating the total energy at the start (at height h), and at the end (when contacting thespring): ଵௐ ଶ W (h) = ଶ ௚ ‫ݒ‬௛ → ‫ݒ‬௛ ൌ ඥ2݄݃ … (1)Wherevh=velocity of weight W at contacting point.First, it should be noted that the spring mass will contribute to the kinetic energy duringdeflection of the spring, since each differential element of mass along the length will movedownward with some kinetic energy during the deflection. This will decrease the potentialenergy of the system. The uppermost element of mass will move the same amount as theblock, since it is immediately below it. Second, the block, upon falling through a height, and gaining speed, now impacts anothermass (the mass of the spring), and the change in speed upon impacting the spring needs to beascertained using the principle of conservation of momentum. The next element will move slightly less, etc. The lowest element will not move at all,since it is contiguous with the base of the spring. 415
  • 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEThis equivalent mass is 1/3 of the spring mass [5], and it is then assumed that the spring hasno mass and an “effective” mass is mounted on top of the spring as a lumped mass. That is,the original spring is replaced by a weightless spring, and on top of this spring is attached ablock having 1/3 the original weight of the spring.By applying, the conservation of momentums to the system of block, and lumped mass at thetime of contact. The spring weight will be defined as WS. It will be assumed that the impact istotally inelastic (e = 0). The two masses then move as one at a common velocity of vS. ௐ ௐ ௐ ‫ݒ‬௛ ൌ ቀ + ଷ௚ ቁ ‫ݒ‬௦ ೞ ௚ ௚ ௐ ‫ݒ‬௦ ൌ ‫ݒ‬ ௐାௐ௦ൗଷ ௛ … (2)The kinetic energy of the combined masses will now be: ௐାௐ௦ൗଷ ଶ ௐାௐ௦ൗଷ ௐమ ‫ݒ‬௦ ൌ ௐK.E. = మ 2݃ℎ = ௐାௐ௦ൗ (ܹℎ) … (3) ଶ௚ ଶ௚ ൫ௐାௐ௦ൗଷ൯ ଷNote that the kinetic energy is less than that just prior to collision (Wh). This is a necessaryresult whenever there is an inelastic collision, where a portion of the energy is lost to heat anddeformation.The maximum deflection of the spring, δ, can now be determined by equating the total energyat the top of the spring, and at the point where the masses come to a stop at a distance δ downfrom the top:At the top, ௐ Kinetic energy= ௐାௐ௦ൗ (ܹ݄) ଷ Potential energy=0At the bottom, kinetic energy=0 (Block reaches zero speed). ௐೞ ଵ Potential energy=− ቀܹ + ଷ ቁ ߜ + ଶ ݇δଶEquating the energies: ௐ ௐೞ ଵ (ܹ݄) + 0 ൌ 0 − ቀܹ + ቁ ߜ + ଶ ݇δଶ … (4)ௐାௐ௦ൗଷ ଷThe average force F, due to the impact occurs at the maximum deflection, δ. ଵSince, ‫ ܨ‬ൌ ଶ ݇δ, …(5)andsubstituting equation 5 into equation 4 gives, ௐ ௐೞ (ܹ݄) + ቀܹ + ቁ ߜ ൌ ‫ܨ‬δ … (6) ௐାௐ௦ൗଷ ଷDividing equation (6) by δ ௐమ ௛ ௐೞ ‫ ܨ‬ൌ ௐାௐ௦ൗ + ቀܹ + ቁ … (7) ଷஔ ଷBut W=mg (௠௚)మ ௛ ௠ೞ ‫ ܨ‬ൌ ൫௠ା௠௦ + ቀ݉ + ቁ݃ …(8) ൗଷ൯௚ ஔ ଷ ௠మ ௛ ௠ೞ ‫ܨ‬ൌ ݃൤ + ቀ݉ + ቁ൨ … (9) ൫௠ା௠௦ൗଷ൯ ஔ ଷ 416
  • 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME ௠ೞ ௠మ ௛Term ቀ݉ + ଷ ቁ is small as compared with ൬൫௠ା௠௦ ൰ , so equation (9) can be written as, ൗଷ൯ ஔ ௠మ ௛ ‫ ܨ‬ൌ ݃ ൤൫௠ା௠௦ ൨ … (10) ൗଷ൯ ஔEquation (10) is used to determine the magnitude of maximum acceleration exerted by theimpact load by dividing the force F by a mass of impactor.VI. THEORETICAL WORKThe Finite Element Method (FEM) offers a way to solve complex continuum problems bysubdividing it into a series of simple interrelated problems. FEM is most commonly used innumerical analysis for obtaining approximate solutions to wide variety of engineeringproblems [6]. In the present study, a commercial general purpose finite element programANSYS® 12.0 is used for numerical simulation of aluminum foam structure. ANSYS®program has many finite element analysis capabilities, ranging from simple, linear, staticanalysis to a complex nonlinear, transient dynamic analysis [7]. The mechanical behavior ofaluminum foam under impact loading was investigated by finite element simulations. In thisstudy, many suggested structural models are investigated in impact mode.V. ALUMINUM FOAM MODELSThree types of 7020 aluminum alloy foams are modeled; the first is aluminum foam withoutreinforcement, and its bulk density is 0.753 g/cm3.The second type is aluminum foam reinforced with 2% weight fraction of alumina whoseparticle size is 90-160µm, and its bulk density is 0.565 g/cm3.The third type is aluminum foam reinforced with 4% weight fraction of alumina whoseparticle size is 90-160µm, and its bulk density is 0.464 g/cm3.The samples of aluminum foam are modeled in three dimensions using closed honeycombcells models with two types of arrangements, as shown in figures 4-Aand 4-B, and a cubicmodel, as shown in figure 5. The behaviors of these models under impact loading arecompared with experimental results.VI. CALCULATION OF CELLS WALL THICKNESSWall thickness of suggested models is calculated based on real values of aluminum foam andaluminum solid densities. Aluminum foam density isρf and aluminum density as solid isρs.Calculations of cell wall thickness are derived based on the rule of densities and volumes, 417
  • 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME ఘ೑ ௏ ఘೞ ൌ ௏ೞ … (11) ೑A Three-dimensional honeycomb cell is shown in fig.6-A, and a cubic cell is shown in fig.6-B, and the equations of wall thicknesses are: 1- A three-dimensional honeycomb structure, ఘ೑ ଷ௟ ௧ ௧೎ ାଷ௟ ௧ ோ ୡ୭ୱ ଷ଴ ఘೞ ൌ ଷ௟ ௧೎ ோ ୡ୭ୱ ଷ଴ … (12)where: - ߩ௙ ൌAluminum foam density, ߩ௦ ൌAluminum solid density, ݈ ൌ Side length of cell, (݈ ൌ 2ܴ sin 30). ‫= ݐ‬Wall thickness of cell, ‫ݐ‬௖ =Cell length, ܴ =Radius of honeycomb cell (R=0.5 d). 2- A three-dimensional cubic cell, ఘ೑ ଷ௧ ఘೞ = ௟ … (13)In equations 11, 12, and 13, ߩ௦ is 2.7 g/m3 for 7020 aluminum alloy, ߩ௙ is foam density whichis calculated from measuring the weight and volume of aluminum foam.VII. DIMENSIONS OF ALUMINUM FOAM MODELSThe honeycomb structure model-1 has a width of 34.641 mm, but honeycomb model-2 has awidth of 35 mm, and these differences are due to cell arrangement.Honeycomb models 1, and 2 have height of h=44mm, cell length of tC=2mm (cell lengthequal to sample thickness), and wall thickness of 0.1685mm which is calculated usingequation (12). Cubic cell model has a width of 20 mm (equal to seven cells or more in each side) [8],height of h=44mm which is equal to a real sample height, cell length of tC=2mm (cell lengthequal to the sample thickness), and wall thickness of 0.186mm which is calculated usingequation (13). -A- -B- Fig.4: A three-dimensional closed honeycomb cells model for 7020 aluminum alloy foam under impact (A- model-1, B- model-2). 418
  • 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME Fig.5:A three-dimensional closed cubic cells model for 7020 aluminum alloy foam under impact (model-3). Fig.6: A- A honeycomb cell, B-A cubic cell.VIII. ELEMENTS USED IN IMPACT LOADS.A nonlinear transient (large displacement) solution is used for the analytical behavior ofaluminum foam under impact loads by using ANSYS Multi-physics. Elements used intransient solution are of two types, the first is for aluminum foam structure which is SHELL181,as shown in fig.7-A. The second is for drop weight which is SOLID 45, as shown infig.7-B.Elements of SHELL 181 are suitable for analyzing thin to moderately-thick shell structures.It is a 4-node element with six degrees of freedom at each node: translations in the x, y and zdirections, and rotations about the x, y and z-axes. SHELL 181 is well-suited for linear, largerotation, and/or large strain nonlinear applications. Change in shell thickness is accounted forin nonlinear analyses. In the element domain, both full and reduced integration schemes aresupported [7]. 419
  • 9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMESOLID 45 is used for the 3-D modeling of solid structures. The element is defined by eightnodes having three degrees of freedom at each node: translations in the nodal x, y and zdirections. The element has plasticity, creep, swelling, stress stiffening, large deflection, andlarge strain capabilities. A reduced integration option with hourglass control is available [7]. -A- -B- Fig.7:A-SHELL 181 geometry, B- A solid 45 geometry[7].IX. EXPERIMENTAL RESULTS Impact tests have been performed on 7020 aluminum alloy foam samples reinforcedwith 2%, and 4% alumina with different weight fraction of particle size (d=90-106, d= 106-125, and d=125-150 µm). The impactor acceleration with respect to time from the moment ofimpact is shown in figures (8to 11). These curves represent experimental results recorded bydata storage oscilloscope. The increase of weight fraction of alumina as reinforcement infigures (9to 11) increases the acceleration of impactor. Figures (12and 13) show the influenceof particle size with 2%, and 4% weight fraction of alumina on the behavior of acceleration-time curves. The decrease of alumina particle size increases the acceleration. The impactoracceleration with respect to time is fitted to quadratic equations using a curve expert softwareversion 1.4. The integration of these curves gives the velocity and the double integrationgives the displacement of impactor with the boundary conditions: initial velocity of -4.429m/sec and initial displacement of zero. The acceleration, velocity, and displacement curveswith respect to time are shown in figures (14 to 17). Figures (15 A, 16 A and 17 A) show anincrease in the impactor acceleration as the weight fraction of alumina particles increases andthe time needed to reach the maximum value of acceleration decreases. The increase ofacceleration means an increase in the impact force according to Newton’s law (Force = massx acceleration) where mass=mass of impactor.Increasing the weight fraction of alumina as reinforcement in aluminum foam increases thestrength of aluminum foam samples. The increase in strength of Al 7020 foam is due to thedistribution of alumina particles around boundaries of pores. This distribution decreases the 420
  • 10. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEpore size, and the number of pores is increased as illustrated by MarchoHaeche [9]. Thisincrease in the number of pores means an increase in the number of walls that carry thecompression load. . Fig.8:Impactor acceleration- Time curve for 7020 aluminum alloy foam. Fig.9:Impactor acceleration-Time curve for 7020 aluminum alloy foam reinforced by (90- 106 µm) alumina particlesFig.10:Impactor acceleration-Time curve for 7020 aluminum alloy foam reinforced by (106- 125 µm) alumina particles. 421
  • 11. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEFig.11:Impactor acceleration-Time curve for 7020 aluminum alloy foam reinforced by (125- 150 µm) alumina particles.Fig.12:The influence of alumina particle size on impactor acceleration- Time curve for 7020 aluminum alloy foam reinforced by 2% weight fraction of alumina particlesFig.13: The influence of alumina particle size on impactor acceleration-Time curve for 7020 aluminum alloy foam reinforced by 4% weight fraction of alumina particles.The impactor velocity in figures (15B, 16B and 17B) at impact is -4.429 m/sec, and the timeneeded to reach a zero velocity value decreases as the weight fraction of alumina particles isincreased in aluminum foam samples. The decrease of the time to reach zero value of velocityis due to the increase of the reaction force generated by impact with the high strength ∆୚aluminum foam samples according to (F = m ୲ ) where ∆V = Vϐ୧୬ୟ୪ െ V୧୬୧୲୧ୟ୪ .The negative values of velocity represent the downward movement of the impactor whichcompresses the aluminum foam sample while the positive values represent the velocity of theimpactor after rebound. Impactor displacements in figures (15C, 16C and 17C) represent thedeflection of aluminum foam samples when displacements lie between zero, and maximumnegative values. Maximum deflection occurs when the velocity is zero. Displacementsbetween maximum negative values and to the end of the displacement curve represent therebound displacement of the impactor. The ability for deformation of aluminum foam 422
  • 12. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEsamples is decreased when weight fraction of alumina particles is increased due to increasedstrength. -A- -B- -C- Fig.14:A- Acceleration–Time (sec) -B- Velocity–Time -C- Displacement–Time for 7020 aluminum alloy foam without reinforcement. -A- -B- -C- Fig.15: A- Acceleration–Time -B- Velocity–Time -C- Displacement– Time for 7020 aluminum alloy foam reinforced with alumina particles of (d=90-106 µm). 423
  • 13. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME -A- -B- -C- Fig.16:A- Acceleration–Time -B- Velocity–Time -C- Displacement– Time for 7020 aluminum alloy foam reinforced with alumina particles of (d=106-125 µm). -A- -B- -C- Fig.17: A- Acceleration–Time -B- Velocity–Time -C- Displacement–Time for 7020 aluminum alloy foam reinforced with alumina particles of (d=125-150 µm). 424
  • 14. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEX. THEORETICAL RESULTSTensile tests were performed on 7020 aluminum alloy samples with, and withoutreinforcement to determine the parameters of Young’s modulus, yield stress, and slope ofstress- strain diagram at the plastic region.Mechanical properties of the as cast 7020 aluminum alloy is: Modulus of elasticity is 4.2 GN/m2. Yield stress is 120MPa. Slope of plastic stress- strain region is 2GN/m2.Mechanical properties of the as cast 7020 aluminum alloy reinforced with 2% of weightfraction of alumina powder with particle size of 90-106 µm is: Modulus of elasticity is 2.6548 GN/m2. Yield stress is 112 MPa. Slope of plastic stress- strain region is 1.5GN/m2.Finally the mechanical properties of the as cast 7020 aluminum alloy reinforced with 4% ofweight fraction of alumina powder with particle size of 90-106 µm is: Modulus of elasticity is 3.526 GN/m2. Yield stress is 116 MPa. Slope of plastic stress strain region is 2 GN/m2.The above parameters are used in ANSYS12 to make, and solve the models.The comparison of acceleration- time, velocity-time, and displacement- time curves for thesuggested models under impact, and experimental curves for 7020 aluminum alloy foamwithout and with reinforcement are shown in figures (18to 20). A comparison of experimental, and theoretical results (transient solution) for manytypes and densities of aluminum foam shows good agreement in displacement-time, andvelocity – time response, especially in the region between zero, and maximum displacementor velocity (i.e. impacting region). However, there is a slight difference in acceleration-timeresponse in the same region. The differences between experimental and theoretical resultsincreased in the region of rebound of impactor which is less important than the impact region. The best suggested model is a three-dimensional cubic model which shows a goodresponse in acceleration, velocity and displacement with time. Fig. 21 shows acceleration-time, velocity-time and displacement-time for solid 7020aluminum alloy subjected to impact.It can be observed that the maximum acceleration for aluminum foam is less than one halfthat for the solid aluminum alloy. For this reason, aluminum foam is widely used today toabsorb impact energy for many applications. 425
  • 15. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME -A- -B- -C- Fig.18:A- Acceleration–Time -B- Velocity– Time-C- Displacement – Time for 7020 aluminum alloy foam (without reinforcement). -A- -B- -C- Fig.19:A- Acceleration–Time -B- Velocity–Time (sec) -C- Displacement–Time for 7020 aluminum alloy foam reinforced with 2% alumina particles of (d=90-106 µm). 426
  • 16. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME -A- -B- -C- Fig.20:A- Acceleration–Time -B- Velocity–Time-C- Displacement– Time for 7020 aluminum alloy foam reinforced with 4% alumina particles of (d=90-106 µm). -A- -B- -C- Fig.21:A- Acceleration–Time -B- Velocity–Time -C- Displacement– Time for solid 7020 aluminum alloy. 427
  • 17. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEXI. CONCLUSIONAluminum alloy foams reinforced with Al2O3 particles have been successfully produced.Impact tests results exhibit a decrease in the amount of deformation of aluminum foamsamples and the Impact tests results exhibit a decrease in the amount of deformation ofaluminum foam samples and an increase in the impactor acceleration with decreasing particlesize and increasing weight fraction of alumina powder. Maximum deformation of aluminumfoam samples at zero velocity of impactor and the time needed to reach zero velocitydecrease with decreasing particle size and increasing weight fraction of alumina powder.Impacting force increases as the particle size decreases and the weight fraction of aluminapowder increases.The suggested models are in general in good agreement with experimental acceleration,velocity, deformation, and force response with time curves of 7020 aluminum alloy foam butthe best model is the three-dimensional cubic model.ACKNOWLEDGEMENTS The authors would like to acknowledge the mechanical engineering department of Al-Nahrain University, for the provision of laboratory facilities.REFERENCES [1] Michael F. Ashby and L.U. Tianjian, Metal foams: A survey, Science in China, series B, 46 (6), December 2003. [2] E. Amsterdam, Structural performance and failure analysis of aluminum foams, Ph.D. thesis, Zernike Institute, 2008. [3] VaružanKevorkijan, Lowcostaluminum foams made by CaCO3 particulates, Association of Metallurgical Engineers of Serbia, MJoM,16 (3), 205-219, (2010). [4] J. D. Bryant, M. D. Clowley, M. D. Wilhelmy, J. A. Kallivayalil, W. Wang, In Metfoam 2007, DEStech Publications Inc., Lancaster, PA, pp. 27, 2008. [5] Matthew Huang,Vehicle crash mechanics, CRC Press LLC, 2002. [6] Huebner, H.H., Dewhirst, D.L., Smith, D. E., and Byrom, T. G. The Finite Element Method for Engineers. 4th ed., New York: J. Wiley. 2001. [7] ANSYS® Release 12.0 Documentation, ANSYS Inc, 2009. [8] M.F. Ashby, A.G. Evans, N.A. Fleck, L.J. Gibson, J.W. Hutchinson and H.N. G. Wadley, Metal foam: A design guide,Butterworth-Heinemann, 2000. [9] MarchoHaeche, Jorg Weise, Francisco Garcia-Moreno and John Banhart, Influence of particle additions on the foaming behavior of AlSi11/TiH2 composites made by semi- solid processing, Materials Science and Engineering, A480 (1, 2), 283-288, 2008. 428

×