AERONAUTICAL LECTURING NOTES

Explain the stress- strain diagram neatly with relevant fig. To select a material for using it in aircraft, we need to know what its life time is.  How much it performs?  and many more requirements. All these are for having a safe flight. The life time and every required factors will be known once if we know stress strain diagram. In order to attain stress strain diagram, we need to have a specimen of desired standards. A standard specimen of the mild steel material is prepared as per BIS standards is given below. Then we need to fix it properly in the universal testing machine. We can give tensile (widely used) or compressive load to the specimen. Load value has to be adjusted very smoothly. By determining the stress and strain at various magnitudes of the load, we can plot a diagram of stress versus strain. Some common terminologies  Load - The force applied to a material during testing. Strain  Gage  or Extensometer  - A devic...

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/m 2 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 = δ L/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 modulu...