Page 26 - Using ANSYS for Finite Element Analysis A Tutorial for Engineers

IntroductIon to FInIte element AnAlysIs • 13
1.1.6.11 fatigue

Fatigue is the phenomenon in which a repetitively loaded structure frac-
tures at a load level less than its ultimate static strength. For instance, a
steel bar might successfully resist a single static application of a 300 kN
tensile load, but might fail after 1,000,000 repetitions of a 200 kN load.
The main factors that contribute to fatigue failures include:

• Number of load cycles experienced
• Range of stress experienced in each load cycle
• Mean stress experienced in each load cycle
• Presence of local stress concentrations

A formal fatigue evaluation accounts for each of these factors as
it calculates how used up a certain component will become during its
anticipated lifecycle.

1.1.6.12 other types of engineering analysis

Other types of engineering that can be solved using FEA are:

• Heat transfer (linear and nonlinear)
• Fluid flow (laminar and turbulent)
• Crash dynamics
• Electromagnetics
• Optimization
• Kinematics

1.1.7 advantages and disadvantages

Advantages:

• Model irregularly shaped bodies quite easily
• Handle general load conditions without difficulty
• Model bodies composed of several different materials because the
element equations are evaluated individually
• Handle unlimited number and kinds of boundary conditions
• Vary the size of the elements to make it possible to use small
elements where necessary