Estructura Aviones
Páginas: 63 (15528 palabras)
Publicado: 11 de julio de 2012
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INTRODUCTION
The airframe of a fixed wing aircraft is generally considered to consist of five principal units, the fuselage, wings, stabilizers, flight control surfaces, and landing gear. Helicopter airframes consist of the fuselage, main rotor and related gearbox, tail rotor (on helicopters with a single main rotor), and the landing gear.
The airframe components areconstructed from a wide variety of materials and are joined by rivets, bolts, screws, and welding or adhesives. The aircraft components are composed of various parts called structural members (i.e., stringers, longerons, ribs, bulkheads, etc.).
Aircraft structural members are designed to carry a load or to resist stress. A single member of the structure may be subjected to a combination ofstresses. In most cases the structural members are designed to carry end loads rather than side loads: that is, to be subjected to tension or compression rather than bending.
Strength may be the principal requirement in certain structures, while others need entirely different qualities.
For example, cowling, fairing, and similar parts usually are not required to carry the stresses imposed byflight or the landing loads. However, these parts must have such properties as neat appearance and streamlined shapes.
PRESSURIZATION PROBLEMS
There are many complex technical problems associated with pressurized aircraft.
Perhaps the most difficult problems are in the design, manufacturing, and selection of structural materials which will withstandthe great differential in pressure that exists between the inside and outside of a pressurized aircraft when flying at high altitudes.
If the weight of the aircraft structure were of no concern, it would be a relatively simple matter to construct a fuselage which could withstand tremendous pressures.
It is necessary to construct a fuselage capable of containing air under pressure, yet belight enough to allow profitable loading. As a general rule pressurized aircraft are built to provide a cabin pressure altitude of not more than 8,000 feet at maximum operating altitude.
If an aircraft is designed for operation at altitudes over 25,000 feet, it must be capable of maintaining a cabin pressure altitude of 15,000 feet, in the event of any reasonably likely failure.
Theatmospheric pressure at 8,000 feet is approximately 10.92 psi, and at 40,000 feet it is nearly 2.72 psi. If a cabin altitude of 8,000 feet is maintained in an aircraft flying at 40,000 feet the differential pressure which the structure will have to withstand is 8.20 psi (10.92 psi minus 2.72 psi).
If the pressurized area of this aircraft contains 10,000 square inches, the structure will besubjected to a bursting force of 82,000 pounds, or approximately 41 tons.
In addition to designing the fuselage to withstand this force, a safety factor of 1.33 must be added. The pressurized portion of the fuselage will have to be constructed to have an ultimate strength of 109,060 pounds (82,000 times 1.33), or 54.5 tons.
From the foregoing example it is not difficult to grasp an idea ofthe difficulties encountered in designing and building a fuselage structure which will be light enough and strong enough at the same time.
PROPERTIES OF METALS
A given metal can possess several properties.
Among these are strength, hardness, malleability, ductility, brittleness, conductivity, expansion, elasticity, toughness, fusibility, and density.
STRENGTH
Oneway to classify metals is according to the amount of strength they possess.
A metal's strength is determined by the percentage of parent metal and other elements used to make an alloy.
TENSILE STRENGTH
When a piece of sheet metal is pulled from each end, the resultant force is called tension.
The ability to withstand tension is called tensile strength, and is measured in pounds per...
INTRODUCTION
The airframe of a fixed wing aircraft is generally considered to consist of five principal units, the fuselage, wings, stabilizers, flight control surfaces, and landing gear. Helicopter airframes consist of the fuselage, main rotor and related gearbox, tail rotor (on helicopters with a single main rotor), and the landing gear.
The airframe components areconstructed from a wide variety of materials and are joined by rivets, bolts, screws, and welding or adhesives. The aircraft components are composed of various parts called structural members (i.e., stringers, longerons, ribs, bulkheads, etc.).
Aircraft structural members are designed to carry a load or to resist stress. A single member of the structure may be subjected to a combination ofstresses. In most cases the structural members are designed to carry end loads rather than side loads: that is, to be subjected to tension or compression rather than bending.
Strength may be the principal requirement in certain structures, while others need entirely different qualities.
For example, cowling, fairing, and similar parts usually are not required to carry the stresses imposed byflight or the landing loads. However, these parts must have such properties as neat appearance and streamlined shapes.
PRESSURIZATION PROBLEMS
There are many complex technical problems associated with pressurized aircraft.
Perhaps the most difficult problems are in the design, manufacturing, and selection of structural materials which will withstandthe great differential in pressure that exists between the inside and outside of a pressurized aircraft when flying at high altitudes.
If the weight of the aircraft structure were of no concern, it would be a relatively simple matter to construct a fuselage which could withstand tremendous pressures.
It is necessary to construct a fuselage capable of containing air under pressure, yet belight enough to allow profitable loading. As a general rule pressurized aircraft are built to provide a cabin pressure altitude of not more than 8,000 feet at maximum operating altitude.
If an aircraft is designed for operation at altitudes over 25,000 feet, it must be capable of maintaining a cabin pressure altitude of 15,000 feet, in the event of any reasonably likely failure.
Theatmospheric pressure at 8,000 feet is approximately 10.92 psi, and at 40,000 feet it is nearly 2.72 psi. If a cabin altitude of 8,000 feet is maintained in an aircraft flying at 40,000 feet the differential pressure which the structure will have to withstand is 8.20 psi (10.92 psi minus 2.72 psi).
If the pressurized area of this aircraft contains 10,000 square inches, the structure will besubjected to a bursting force of 82,000 pounds, or approximately 41 tons.
In addition to designing the fuselage to withstand this force, a safety factor of 1.33 must be added. The pressurized portion of the fuselage will have to be constructed to have an ultimate strength of 109,060 pounds (82,000 times 1.33), or 54.5 tons.
From the foregoing example it is not difficult to grasp an idea ofthe difficulties encountered in designing and building a fuselage structure which will be light enough and strong enough at the same time.
PROPERTIES OF METALS
A given metal can possess several properties.
Among these are strength, hardness, malleability, ductility, brittleness, conductivity, expansion, elasticity, toughness, fusibility, and density.
STRENGTH
Oneway to classify metals is according to the amount of strength they possess.
A metal's strength is determined by the percentage of parent metal and other elements used to make an alloy.
TENSILE STRENGTH
When a piece of sheet metal is pulled from each end, the resultant force is called tension.
The ability to withstand tension is called tensile strength, and is measured in pounds per...
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