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Explain in brief about each property used in mechanics?
The properties of the mechanics are as follows:
• Strength: this is the applied force on a material that can withstand prior to
fracture. It is measured by the proof or yield stress of a material that is
under action.
• Working stress: this is the stress that is being imposed on a material as a
result of the load that is being subjected on the material. The loads that are
given must be in the elastic range.
• Proof stress: defines the tensile stress
• Ultimate tensile stress (UTS): defines of a material that is given by a
relationship or its maximum load.
• Specific strength: defines the light and strong of a material that is used in
aircraft making. This is done to maximize the payload and meeting all the
safety requirements.
• Malleability: defines the ability to be rolled into sheets or get a shape
under pressure. This includes examples of gold, copper and lead.
• Elasticity: defines the ability of a material to return to its original shape
when an external force is removed from the material.
What is the purpose of load extension graphs?
Load extension graphs are used to show the result of mechanical test done on the
material to know their certain properties for example finding out the heat
treatment of a material. These graphs shows certain phases of a material when
it is being tested for destruction of the properties like elastic range, limit
of proportionality, etc. The material needs to obey Hooke’s law. The elastic
limit needs to be at or very near to the limit of proportionality. If the limit
is passed the material ceases to be proportional to the load. If the stress
increases on the material then the waist reduces as the stress = force/area.
This graph represents a curve that shows different stages like elastic stage,
and plastic stage.
Why is torsion such an important feature in aircraft engines?
Torsion is used to drive shafts for aircraft engine driven pumps and motors.
They are also involved in having a force behind propeller shafts, pulley
assemblies and rive couplings for machinery. The shear stress is setup within
the shafts and it results from the torsional loads. The size and the nature of
torsional loads and stresses need to be known while making the design or else
premature failure can occur. The shafts are used as a component to transmit
torsional loads and twisting moments or torque. They can be a cross section or
a circular component as it is more suitable to transmit the torque for pumps
and motors to supply the power to the aircraft system.
What is the main function of propulsive thrust?
Propulsive thrust is used in aircraft system, when an aircraft is traveling
through air in straight or level flight then the engine produces a thrust that
is equal to the air resistance or the drag force on the aircraft. If the engine
thrust exceeds the drag then the aircraft will accelerate and if drag exceeds
the engine thrusts then the aircraft system will slow down. The thrust force
that is used for aircraft propulsion should always come from air or gas
pressure. The forces that are external always act on the engine or propeller.
This propeller can be driven either by a piston or a gas turbine engine. If
there is a use of jet engine then the high velocity exhaust gas is produced.
Why is the study of gyroscopes motion required to learn aircraft applications?
Gyroscopic motion is considered as an important study for aircraft application
for the inertia and momentum of the body that is used in circular motion. The
momentum is the product of the mass of a body and its velocity. This is a
measure of the quantity of motion of a body. Inertia is the force that doesn’t
allow any change to happen in momentum. Gyroscope is the rotating mass that can
be moved freely at right angles to its plane of rotation. This utilizes the
gyro rotor or gyroscopic inertia to provide the motion unless it is compelled
by an external force to change the state. This uses property of rigidity as
gyroscope acts as a reference point in space.
What are the laws of gyro-dynamics?
Gyro-dynamics deals with gyroscopic motion that is used for creating aircraft
application as it allows inertia and momentum of the body. These laws consist
of the two properties of rigidity and precession to provide the visible effects
gyro-dynamics. These are as follows:
• If a rotating body is mounted and it is free to move about any axis that
passes through the center of mass, then the spin axis that is used will remain
fixed in inertial space without displacing any of the frame.
• If a constant torque is applied to any direction such as about an axis, or
perpendicular to the axis, then the spin axis will move about an axis that is
mutually perpendicular to both the spin and the torque axis.
What is being expressed by Sperry’s rule of precession?
Sperry’s rule of precession describes about the direction in which the
precession takes place. This precession is dependent on the direction of
rotation for the mass and the axis of the torque that is applied on the
material. It provides a guide to the direction of precession that allows easy
finding of the direction of the applied torque. This also helps in finding out
the direction of the rotation of gyro-wheel. If the torque is applied and is
perpendicular to the spin axis then it can be transferred as a force.
What are the elements required to display oscillatory motion?
The elements required to display oscillatory motion are as follows:
Period: this is related to the time and it signifies the time that elapses in
between the motion that will repeat itself after some time again. Oscillatory
motions allow themselves to be repeated after equal intervals of time and this
is called as periodic.
• Cycle: it represents the completion of one period and it also signifies the
motion that is completed in one period.
• Frequency: defines the number of cycles completed in unit time.
• Amplitude: defines the distance from one point to another or from highest to
lowest point of the motion from the central position.
What are the different lift augmentation devices present?
Lift augmentation devices provides flaps that are moving wing sections that
increase wing camber and provide an angel of attack. Flaps have their own use
like if an aircraft takes off and land in a short distance then the wings of it
should produce sufficient lift at lower speed. Flaps provide a way to slow down
the aircraft. There two categories and they are as follows:
• Trailing edge flaps includes different flaps like
• Plain flap that is used to retract the complete section of trailing edge and
it is used in downward.
• Split flap gets formed by the hinged lower part of trailing edge and the
lowered top surface remains unchanged and it eliminates the airflow that occurs
over the top of the surface of the plain flap.
• Leading edge flaps: is used to augment the low speed lift that is swept on
the wing aircraft. They help in increase the camber and allow the coupling to
operate together with the trailing edge flaps.
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