The components of a machine, when rotating at a high speed, are subjected to a high degree of load, which fluctuates from a high value to a low value.
For the machine elements under the action of static loads, static failure theories are applied to know the safe and hazardous working conditions and regions..
The components are subjected to forces, which are not static, but vary in magnitude with respect to time.
The stresses induced due to such forces are called Fluctuating Stresses.
The most popular model for stress–time relationship is the sine curve..
The load fluctuation would be a factor that increases the reserve power.
In order to reflect, the system has been analyzed according to period, season and load level.
The method has been analyzed load fluctuation to power system frequency by using the Fourier transform..
Fatigue is defined as a process that causes damage in a material and structure under fluctuating loads of a magnitude much less than the static failure load..
The failure of a material under the action of a fluctuating load, namely fatigue, has been recognised as one of the major causes of fracture in metals..
A machine member is subjected to fluctuating stress σ = σo cos (8πt).
The endurance limit of the material is 350 MPa..
47.
REVERSED STRESSES—DESIGN FOR FINITE AND INFINITE LIFE •There are two types of problems in fatigue design— (i) components subjected to completely reversed stresses, and (ii) components subjected to fluctuating stresses, the mean stress is zero in case of completely reversed stresses.
21.
Fluctuating stresses When the mechanical component is subjected to fatigue or fluctuating load then stress induced is known as Fluctuating stress.
Mean stress Stress amplitude Examples of components subjected to fluctuating stresses are Rocker Arm of I.C. engine, I.C. engine cylinder 22.
Unit 3 Design against fluctuating load Session 3.5:
Machine elements are subjected to varieties of loads, some components are subjected to static loads, while some machine components are subjected to fluctuating loads, whose load magnitude tends to fluctuate.
