finite element analysis interview questions

1 Define: finite element method.
ans A numerical technique for finding approximate solutions of partial differential equations (PDE) as well as of integral equations.
or
computational technique for determining the distribution of stresses in engineering structures under load.
2 Finite element method is an approximate method (true/false). Also justify your answer.
3 What are approximating functions?
4 What are field variables?
5 Name at least four FEA popular packages.
ans Abaqus: Franco-American software from SIMULIA,by Dassault ystemes
ADINA
ALGOR Incorporated
ANSA: Adv. CAE pre-processing software 4 complete model build up.
ANSYS
LS-DYNA
6 Define: i. node ii. Element.
7 Briefly explain the application of FEA for a stress analysis with an element.
8 Compare between FEM and classical methods.
9 Compare between FEM and FDM.
10 When there are several FEA packages are available in that any need to study this method.
11 Discuss the advantages and disadvantages of FEA.
12 Explain the concept of FEM briefly and outline the procedure.
13 Write the equation of equilibrium in plane stress condition.
14 Draw a typical three dimensional element and indicate state of stress in their positive signs.
15 Derive the equation of equilibrium in case of a two dimensional stress system.
16 State and explain generalized hook’s law.
17 Explain the term plane stress.
A state of stress in which two of the principal stresses are always parallel to a given plane and are constant in the normal direction.
18 Explain the term plane strain.
A deformation of a body in which the displacements of all points in the body are parallel to a given plane, and the values of these displacements do not depend on the distance perpendicular to the plane.
19 Distinguish between plane stress and plane strain.
20 When do you select plane stress / plane strain approximation?
ANS Plane strain and Plane stress are two simplification structural models for the modeling of 3D problems, in which:
- Plane strain modelling: strain in Z-direction is neglectible
- Plane stress modelling: stress in Z-direction is neglectible
For a beam, plane stress is normally used, assuming that the stress in Z-direction can be neglected;
otherwise 3D modelling is advisable.
With reference to the element types, for 2D models, quadrilateral elements with quadratic interpolation is recommended.
For 3D models, brick solid elements with quadratic interpolation is recommended.
21 Write the constitutive equation for the plane stress and plane strain problems.
22 Write the standard form of finite element equation.
23 Draw bar element and write the stiffness matrix.
24 Define DOF.
Minimum no of parameters required to define an entity completely in space
25 Draw a plane truss element and indicate the truss element.
26 What are natural coordinates?
27 Define: local coordinates.
28 Write the stiffness matrix for the plane truss element.
29 Explain the use of element connectivity table.
30 State the purpose of element connectivity table.