Strength of Materials

By -
Define stress.
When an external force acts on a body, it undergoes deformation. At the same time the body resists deformation. The magnitude of the resisting force is numerically equal to the applied force. This internal resisting force per unit area is called stress.
Stress = Force/Area     N/m2
Define strain
When a body is subjected to an external force, there is some change of dimension in the body. Numerically the strain is equal to the ratio of change in length to the original length of the body.
Strain = Change in length/Original length
e = δL/L

Define- elastic limit
Some external force is acting on the body, the body tends to deformation. If the force is released from the body it regain to the original position. This is called elastic limit.

State Hooke’s law
It states that when a material is loaded, within its elastic limit, the stress is directly proportional to the strain.
Stress α Strain
σ α e

Define – Young’s modulus
The ratio of stress and strain is constant within the elastic limit.
E = Stress/ Strain


Comments

Post a Comment

Popular posts from this blog

Fire detection system in aircraft

By -
Image
What are the common fire detection methods followed in aircraft? Explain them with neat diagrams. Thermal Switch: Thermal switches are heat –sensitive units that complete electrical circuits at a certain temperature. They are connected in parallel with each other. If the temperature rises above a set value in any one section of the circuit, the thermal switch will close the electrical circuit and gives indication to the pilot through indication lights. Thermo-couple systems: A thermocouple gives the rate of temperature rise. A Thermocouple is the junction of two dissimilar metals which generates a small electric current that varies according to the temperature of the junction. For this reason it does not require an external power source. The dissimilar metals can be constantan and iron, Alumel and Chromel, or some other combination of metals or alloys which will produce the required results. The complete thermocouple circuit consists of the ‘cold’ junction, the ‘h
Get more »

Vapour cycle cooling system in aircraft

By -
Image
Explain the vapor cycle cooling system used in aircraft with neat illustration. Also explain the physics behind the scene of working. Physical principle Liquids can be vaporized at any temperature by changing the pressure acting on it.  To clearly understand this concept, we will take an example of water contained in a vessel. When the vessel is at atmospheric pressure, the water will be boiling at 100°C when heating. If I am pressurizing the vessel to more than the atmospheric pressure, then water will not boil at 100°C. If I am creating a drop in pressure in the vessel by a vacuum pump, then water will boil at a temperature less than 100°C. Basic law of thermodynamics states that heat will always flow from hot body to cold body. If I need a reverse of this, I have to add some work. System operation: 1. We are having the FREON as refrigerant in the vapor cycle cooling system. It has a boiling point of 4°C. 2. At the receiver I am having high pressure, so t
Get more »

Smoke detection system in Aircraft

By -
Image
What are the methods to find smoke prevailing in aircraft? Explain with neat sketches. For smoke, fire is main reason. In some cases it may not be. However pure air just contains 78% of nitrogen, 21% of oxygen and 1% rest of other gases. When there is fire in the aircraft the air will be dirt since carbon monoxide or carbon dioxide presents. There are four effective ways to identify the smoke. Light detection Light Refraction Ionization Solid state semiconductor Light detection type: We all know photo voltaic cell converts light energy into electrical energy. The pure light rays will be fall on photo voltaic panel and produces some electrical energy at normal.  When the area is surrounded by smoke the intensity of light rays falling on the panel gets differ. From that we get alarm. Light Refraction type smoke detector: Here a certain mass of air is taken for smoke detection by use of fan. Source of light is the Electric bulb. It is made to pass
Get more »