METAL FOAM

• A metal foam is a cellular structure consisting of a solid metal, For ex.

aluminium, containing a large volume fraction of gas-filled pores. • The pores can be sealed (closed-cell foam), or they can form an interconnected

network (open-cell foam).• The defining characteristic of metal foams is a very high porosity: typically 75-

95% of the volume consists of void spaces.• The strength of foamed metal possesses a power law relationship to its

density; i.e., a 20% dense material is more than twice as strong as a 10% dense material.

• Metallic foams typically retain some physical properties of their base material. Foam made from non-flammable metal will remain non-flammable and the foam is generally recyclable back to its base material. Coefficient of thermal expansion will also remain similar while thermal conductivity will likely be reduced.

INTRODUCTION

STRUCTURE OF METAL FOAM• In metal foams cells are divided

into distinct cells. the boundaries of these materials are made of solid material, the interior are voids.

TYPES OF METAL FOAMOPEN CELL METAL FOAM CLOSED CELL METAL FOAM

Open cell Ni -foam Closed cell Al foam

1. Closed-cell metal foams are primarily used as an impact-absorbing material,

2. They are light (typically 10–25% of the density of the metal they are made of, which is usually aluminium) and stiff, and are frequently proposed as a lightweight structural material. However, they have not yet been widely used for this purpose.

3. Closed-cell foams retain the fire resistant and recycling capability of other metallic foams but add an ability to float in water.

4. Light weight Al foam has a density of from 300 to 1,000 kg/m³, that is, 30 to 100% that of water. Components made of the material can therefore be expected to float.

5. Foam metal has also begun to be used as an experimental prosthetic in animals

1.Heat exchangersCompact electronics coolingCryogen tanksPCM heat exchangers

2.Energy absorption3.Flow diffusion and lightweight optics4.Extremely fine-scale metal foam are used as high-temperature filters in the chemical industry.

Due to the high cost of the material it is most typically used in advanced technology aerospace and manufacturing.

OPEN CELL METAL FOAM CLOSED CELL METAL FOAM

MANUFACTURING1. Foaming of Melts by Gas Injection

2. Foaming of Melts with Blowing agents

3. Powder processing method

SIMULATION OF THE CRUSHING OF A METAL FOAM

CHARACTERISTICS OF AL FOAM• Are very stiff at a very low weight • Are very effective in terms of acoustical absorption• Are very effective in terms of electromagnetic

shielding and structural damping • Absorb impact energy regardless of impact direction • Are much more stable than organic materials like

wood or plastics • Are decorative are completely recyclables and hence

do not cause any harm to our environment

PROPERTIES1. STIFFNESS

2. SOUND ABSORPTION

3. IMPACT ENERGY ABSORPTION

4. Thermal conductivity• Thermal conductivity λ, defined according

Fourier’s law

• Depends strongly on the cross sectional area S enabling the thermal flow rate Q’ through the specimen (dT/dx is a temperature gradient).

• In a foamed aluminium only a small part of the cross section (pore walls) is metallic with the thermal conductivity given by the base alloy. The rest are the pores filled with gas which has a much lower thermal conductivity than an aluminium alloy

APPLICATION OF AL FOAM1.Crash box

2.Acoustic noise reduction-Sound absorption in difficult condition-Sound absorption in commercial buildings, hotels, roads

3.Electromagnetic shielding -Cover boxes for electronic devices -Wall and ceiling plates for protection of rooms against entering or releasing of electromagnetic waves

Photographs of crushed crash box

4.Self-supporting, stiff and super light weight panels for building and transport

5.Compressor casings 6.Heat exchangers, filters, catalysts 7.Instrument housing 8.Loudspeaker enclosures 9.Gearbox housings 10.Structural parts for spacecraft

ADVANTAGES 1. Metal foams provide excellent energy absorption

features at a higher strength level as compared to foamed polymers

2. Metal foams are easily processed by sawing, drilling, milling, etc,

3. Metal Foams can be joined by adhesive bonding, brazing, and TIG and laser welding techniques.

4. It does not erode, even under the effects of air flow or vibration.

5. It is easily recyclable.6. Provides sound absorption at low frequencies at a

smaller material thickness in comparison with other absorption materials such as glass or mineral wool fibers or polymer foams.

1. They are difficult to manufacture as precision manufacturing is required.

2. Cost is a major factor3. Difficultly in manufacturing high temperature

metal4. Knowledge about the metal foam is still not

wide spread5. Once damaged it can not be repaired ,the

whole metal foam has to replaced by new one.

DISADVANTAGES

CONCLUSION1.There is considerable interest in the applications

of metallic foams from a wide range of industries.

2.Impact and energy absorption are key applications, particularly within the transport industries.3.Thermal management properties can be exploited by the electronics industry in particular.

Metal foam are yet to widely used the metal foams can be used in the following fields which are yet to tapped in the market.

– 1. In commercial light weight doors– 2. In the impact absorbing in cars– 3. In lift safety system– 4. In road medians and dividers– 5. In construction industry as light weight material– 6.In Shipping industries– 7. In helmets

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