The magnetic properties of engineering materials are due to the spinning of electrons in them. Also, the orbit of electrons around the nuclei of engineering materials is another reason for the magnetic properties of engineering materials.
When electrons spin in opposite directions, there is no magnetic field because the spinning of electrons causes them to neutralize each other. But when there is an excess of electrons spinning in the same direction, a magnetic field is produced.
This study of the magnetic properties of engineering materials is necessary because it is from it we understand the structure and behavior of matter. Some important properties of engineering materials are:
Absolute permeability: It is the ratio of the flux density in a material to the magnetizing force producing that flux density.
Coercive Force: may be defined as the magnetizing force necessary to neutralize completely the magnetism in an electromagnet when the magnetizing force is zero.
Magnetic hysteresis: is that quality of a magnetic substance as a result of which energy is dissipated in it on reversal of its magnetism.
Thursday, March 24, 2011
Electrical Properties of Engineering Materials.
Engineering materials have electrical properties which is their ability to permit or resist the flow of electricity through them. These properties could be sub-divided into restivity,conductivity, temperature coefficient of resistance, dielectric strength and thermoelectricity.
(1.) Resistivity: This the electrical property of a material due to which it opposes the flow of electricity through it. It is given by
Resistivity, P = R.A/l
(2.) Conductivity: This is the reciprocal of resistivity.
(3.) Temperature coefficient of resistance: This is the variation of resistivity with temperature.
(4.) Dielectric strength: is the insulating capacity of a material against high voltages.
(5.) Thermoelectricity: This is when a small voltage is produced as a result of heating 2 different metals together.
(1.) Resistivity: This the electrical property of a material due to which it opposes the flow of electricity through it. It is given by
Resistivity, P = R.A/l
(2.) Conductivity: This is the reciprocal of resistivity.
(3.) Temperature coefficient of resistance: This is the variation of resistivity with temperature.
(4.) Dielectric strength: is the insulating capacity of a material against high voltages.
(5.) Thermoelectricity: This is when a small voltage is produced as a result of heating 2 different metals together.
Saturday, March 19, 2011
Mechanical Properties of Engineering Materials Part 2.
One had started mechanical properties, for the start click here.The remaining are discussed here.
(1.) Ductility: The ability of a material to withstand bending or elongation without breaking. A material that has this characteristics is said to be ductile. This property is valuable in chains and ropes because they don't snap off or break due to elongation and bending during service.
(2.) Malleability:
This is the ability of a material to be hammered or rolled easily into thin sheets without rupturing. Malleability of a material increases with the increase in temperature.
(3.) Toughness: is the resistance of a material to rupture. This resistance to rupture is due to the force of attrac tion between each molecules which gives them the power to resist any force tending to tear them apart. Toughness of a material can be expressed as the energy absorbed per unit volume of the material participating in the absorption of energy. It's unit is Nm/m^3.
(4.) Brittleness: This is when a body breaks easily when subjected to shocks. Such a material is said to be brittle.
(5.) Hardness: is the resistance of a material to penetration. The hardness of engineering materials is generally carried out by pressing an indentor into the surface of the material through slowly applied load. The extent of the resulting impression caused by the indentor is then measured mechanically and optically. A large impression means that the material is soft while a small impression means that the material is hard.
(6.) Fatigue: When materials are subjected to flunctuating or repeating loads (or stresses), they tend to fail. This type of failure is different from that which they experience when subjected to steady loads. This type of failure is called FRACTURE. The phenomenon that leads to fracture is FATIQUE.
(7.) Creep: is the slow plastic deformation of metals under constant stress or when they are subjected to prolonged loading at high temperature. Creep can lead to fracture at static stresses which are much smaller than those which will break the material by loading quickly. Creep is specially taken care off in Internal Combustion enginer, boilers and turbines
(1.) Ductility: The ability of a material to withstand bending or elongation without breaking. A material that has this characteristics is said to be ductile. This property is valuable in chains and ropes because they don't snap off or break due to elongation and bending during service.
(2.) Malleability:
This is the ability of a material to be hammered or rolled easily into thin sheets without rupturing. Malleability of a material increases with the increase in temperature.
(3.) Toughness: is the resistance of a material to rupture. This resistance to rupture is due to the force of attrac tion between each molecules which gives them the power to resist any force tending to tear them apart. Toughness of a material can be expressed as the energy absorbed per unit volume of the material participating in the absorption of energy. It's unit is Nm/m^3.
(4.) Brittleness: This is when a body breaks easily when subjected to shocks. Such a material is said to be brittle.
(5.) Hardness: is the resistance of a material to penetration. The hardness of engineering materials is generally carried out by pressing an indentor into the surface of the material through slowly applied load. The extent of the resulting impression caused by the indentor is then measured mechanically and optically. A large impression means that the material is soft while a small impression means that the material is hard.
(6.) Fatigue: When materials are subjected to flunctuating or repeating loads (or stresses), they tend to fail. This type of failure is different from that which they experience when subjected to steady loads. This type of failure is called FRACTURE. The phenomenon that leads to fracture is FATIQUE.
(7.) Creep: is the slow plastic deformation of metals under constant stress or when they are subjected to prolonged loading at high temperature. Creep can lead to fracture at static stresses which are much smaller than those which will break the material by loading quickly. Creep is specially taken care off in Internal Combustion enginer, boilers and turbines
Properties Of Engineering Materials
Engineering Materials exhibit the following properties. They are
(1.) Physical properties.
(2.) Mechanical properties.
(3.) Electrical properties.
(4.) Magnetic properties.
(5.) Chemical properties.
Physical Properties of Engineering Materials.
The physical properties of engineering materials, metals in particular are colour, size, shape, density, thermal conductivity, melting point and boiling point.
Mechanical Properties of Engineering Materials.
The mechanical properties exhibited by engineering materials include strength, elasticity,plasticity, ductility, stiffness,malleability, toughness, brittleness, hardness, fatigue and creep etc.
(1.) Strength: This is the ability of a material to resist or withstand externally applied forces to which it is subjected to during a test or in service without breaking. The internal resistance by a material to the externally applied force is called stress. The strength of a material could be defined in terms of tensile strength, compressive strength, proof stress, shear strength etc. Also the strength of any engineering material could be seen as the measure of the capacity of the resistance of solid masses or pieces of the material to any force tending to produce in them a permanent deformation or fracture. The strength of engineering materials depends on the forces which are present in and around the molecules of the material. One of these forces is cohesion. Another one is adhesion.
(2.) Elasticity: This is the property of a material to regain its original shape and size after deformation when the external load or force causing the deformation is removed. A material is said to be perfectly elastic if all the stresses (which lead to the deformation of the material) disappears completely upon the removal of the load. This property is desirable for materials used in machine cutting tools. Elasticity has a constant of proportionality called Young's Modulus (E).
(3.) Stiffness:This is the ability of a material to resist deformation under stress. The Young's Modulus (E) is a measure of the stiffness of a material.
(4.) Plasticity: This is the property of a material to remain deformed permanently or to retain a deformation caused by an applied load permanently after the removal of the load. During plastic deformation, there are displacement of atoms within the grains of the material. This makes the material to experience a change in shape.
(1.) Physical properties.
(2.) Mechanical properties.
(3.) Electrical properties.
(4.) Magnetic properties.
(5.) Chemical properties.
Physical Properties of Engineering Materials.
The physical properties of engineering materials, metals in particular are colour, size, shape, density, thermal conductivity, melting point and boiling point.
Mechanical Properties of Engineering Materials.
The mechanical properties exhibited by engineering materials include strength, elasticity,plasticity, ductility, stiffness,malleability, toughness, brittleness, hardness, fatigue and creep etc.
(1.) Strength: This is the ability of a material to resist or withstand externally applied forces to which it is subjected to during a test or in service without breaking. The internal resistance by a material to the externally applied force is called stress. The strength of a material could be defined in terms of tensile strength, compressive strength, proof stress, shear strength etc. Also the strength of any engineering material could be seen as the measure of the capacity of the resistance of solid masses or pieces of the material to any force tending to produce in them a permanent deformation or fracture. The strength of engineering materials depends on the forces which are present in and around the molecules of the material. One of these forces is cohesion. Another one is adhesion.
(2.) Elasticity: This is the property of a material to regain its original shape and size after deformation when the external load or force causing the deformation is removed. A material is said to be perfectly elastic if all the stresses (which lead to the deformation of the material) disappears completely upon the removal of the load. This property is desirable for materials used in machine cutting tools. Elasticity has a constant of proportionality called Young's Modulus (E).
(3.) Stiffness:This is the ability of a material to resist deformation under stress. The Young's Modulus (E) is a measure of the stiffness of a material.
(4.) Plasticity: This is the property of a material to remain deformed permanently or to retain a deformation caused by an applied load permanently after the removal of the load. During plastic deformation, there are displacement of atoms within the grains of the material. This makes the material to experience a change in shape.
Saturday, November 27, 2010
Groups of Engineering Materials.
Based on their properties, this post has grouped engineering materials into:
(1.) Alloys (or Metals)
(2.) Plastic Materials.
(3.) Ceramics and Rubbers.
(4.) Composite Materials.
Alloys (or Metals).
An alloy can be defined as a metallic solid or liquid which is a mixture of 2 or more metals. For two metals to form a strong alloy, they must be able to mix with each other in their molten state. Alloy may contain some non-metallic elements such as carbon. Examples of alloys are Steel, Cast Iron.
Plastics.
These are organic materials containing molecules of high molecular weight which can be moulded to shape through the application of pressure at moderately high temperatures. Once moulded, some plastics may retain their plasticity while others may become hard and brittle. Examples of plastics are polyethene, nylon and bakelite.
(3.) Ceramics and Rubbers.
Ceramics are inorganic non-metallic materials which in most cases have been subjected to high temperature at some stages during manufacture. Examples of ceramics are natural and man-made glasses used to make bottles, windows and lenses, cements etc.
Rubbers are substances which have polymer molecules arranged in a manner that allows reversible extension to take place at normal temperatures. Well an example of rubber is the natural one derived from the sap of rubber tree.
(4.) Composite Materials.
Composite materials are groups of dissimilar materials combined together to form a new complex whose properties are different in type and magnitude from those of its seperate constituents. An example of a natural composite is wood which consists of cellulose bounded by lignin. Other examples of composites are reinforced concrete and vulcanized rubber.
(1.) Alloys (or Metals)
(2.) Plastic Materials.
(3.) Ceramics and Rubbers.
(4.) Composite Materials.
Alloys (or Metals).
An alloy can be defined as a metallic solid or liquid which is a mixture of 2 or more metals. For two metals to form a strong alloy, they must be able to mix with each other in their molten state. Alloy may contain some non-metallic elements such as carbon. Examples of alloys are Steel, Cast Iron.
Plastics.
These are organic materials containing molecules of high molecular weight which can be moulded to shape through the application of pressure at moderately high temperatures. Once moulded, some plastics may retain their plasticity while others may become hard and brittle. Examples of plastics are polyethene, nylon and bakelite.
(3.) Ceramics and Rubbers.
Ceramics are inorganic non-metallic materials which in most cases have been subjected to high temperature at some stages during manufacture. Examples of ceramics are natural and man-made glasses used to make bottles, windows and lenses, cements etc.
Rubbers are substances which have polymer molecules arranged in a manner that allows reversible extension to take place at normal temperatures. Well an example of rubber is the natural one derived from the sap of rubber tree.
(4.) Composite Materials.
Composite materials are groups of dissimilar materials combined together to form a new complex whose properties are different in type and magnitude from those of its seperate constituents. An example of a natural composite is wood which consists of cellulose bounded by lignin. Other examples of composites are reinforced concrete and vulcanized rubber.
Saturday, November 20, 2010
Materials In Engineering.
All engineering products are made up of materials. In fact almost nothing in this world useful to man is not a material which has an engineering application. For example, the concrete of highways and the bodies of automobiles are obviously engineering materials. Most of us know the importance of electricity to our modern world. But the materials used to transmit electricity from the source of power supply to our homes are engineering materials. Even our houses are made up of engineering materials. The food we eat, the water we drink or any edible thing we take into our bodies are processed and prepared using engineering materials. So there is almost nothing that is useful and man made to us in this world that is not an engineering material or closely related and connected to any engineering material. Therefore we can safely conclude that the advancement in technology is strongly dependent on the development of materials which help us to translate the engineering ideas into reality.
Seeing the importance of engineering materials, it is necessary for all engineers in all engineering fields to have a basic knowledge of engineering materials so that they will be able to select and specify the best material which has the required properties for any engineering application. For instance, looking at the earlier examples given, the materials to be used for the design and the construction of highways should be such that they can be easily processed into satisfactory and economical final products. Again they must have the required properties which will enable them to give the desired performance during service which is high strength and durability properties that cannot be ignored when looking at the safety of life and property. So any engineer in any engineering field needs to have a basic knowledge of engineering materials so that he/she will be able to know the best material to chose for any engineering application. The understanding of how engineering materials behave when subjected to different conditions will enable the engineer to know the limitations of the material chosen and the modifications he has to make both in the design and manufacture of the chosen material.
Seeing the importance of engineering materials, it is necessary for all engineers in all engineering fields to have a basic knowledge of engineering materials so that they will be able to select and specify the best material which has the required properties for any engineering application. For instance, looking at the earlier examples given, the materials to be used for the design and the construction of highways should be such that they can be easily processed into satisfactory and economical final products. Again they must have the required properties which will enable them to give the desired performance during service which is high strength and durability properties that cannot be ignored when looking at the safety of life and property. So any engineer in any engineering field needs to have a basic knowledge of engineering materials so that he/she will be able to know the best material to chose for any engineering application. The understanding of how engineering materials behave when subjected to different conditions will enable the engineer to know the limitations of the material chosen and the modifications he has to make both in the design and manufacture of the chosen material.
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