# Finite Element Method Questions and Answers – Three Dimensional Problems – Mesh Preparation

This set of Finite Element Method Multiple Choice Questions & Answers (MCQs) focuses on “Three Dimensional Problems – Mesh Preparation”.

1. The finite element method increases the degrees of freedom from finite to infinite.
a) True
b) False

Explanation: The given statement is false. The finite element method decreases the degrees of freedom from infinite to finite. This is achieved by discretization or meshing of the structure under discussion. This comes under the pre processing stage of the finite element method.

2. 2D Meshing is carried out on a mid surface. Why is it so?
a) Element thickness is assigned half on top of the element and half below
b) Element thickness is assigned completely on the top of the element
c) Element thickness is assigned uniformly across the element
d) Element thickness is assigned completely at the bottom of the element

Explanation: 2D Meshing is carried out on a mid surface. These elements are planar, and in order to represent the geometry appropriately the meshing is carried out in such a fashion. The element thickness is assigned half on the top of the element and half on the bottom side.

3. What are the different types of meshing techniques?
a) Controlled, Authentic and Fraudulent
c) Automatic, mapped and manual
d) Integral, Discrete and continuous

Explanation: There are various types of meshing techniques; these are broadly classified into Automatic, Mapped and Manual types respectively. Automatic Meshing is the easiest to perform, as the software performs geometry cleanup and meshing with minimal input from the user.

4. Geometry cleanup/check is not a pre requisite for performing meshing.
a) True
b) False

Explanation: 2D Meshing is carried out on a mid surface. These elements are planar, and in order to represent the geometry appropriately the meshing is carried out in such a fashion. The element thickness is assigned half on the top of the element and half on the bottom side.

5. “Special care needs to be taken while meshing in critical areas.” Why is this so?
a) Because of high stress
b) Because of low stress
c) Because of axial stress
d) Because of bending stress

Explanation: Critical areas are those which are prone to high stress. Due to this reason, extra care needs to be taken while meshing in such areas. Some examples of critical areas include – elements with holes, and elements with fillets etc.
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6. Which of the following defines a free edge?
a) Edge owned by two surfaces only
b) Edge owned by two or more surfaces
c) Edge owned by three surfaces only
d) Edge owned by one surface only

Explanation: Free edge is defined as an edge that is owned by one surface only. Surfaces which have a free edge in between them do not combine to form a single surface. A free edge is undesirable when it comes to meshing.

7. Which of the following defines a shared edge?
a) Edge shared by two adjacent surfaces
b) Edge shared by two parallel surfaces
c) Edge shared by two perpendicular surfaces
d) Edge shared by two coincident surfaces

Explanation: Shared edge is defined as an edge shared by two adjacent edges. When the edge between two adjacent surfaces is a shared edge; they are said to be geometrically continuous. This edge is desirable and very much needed for meshing.

8. Which of the following is not a type of mesh element?
a) Trias
b) Pentas
d) Circles

Explanation: Circles is not a type of meshing element. A meshing element defines the shape of the element into which the structure can be broken down. Trias, pentas, quads are all existing types of meshing elements.

9. Which of the following is not a type of discontinuity encountered in a structure?
b) Geometry
c) User data
d) Material

Explanation: User data is not a type of discontinuity. Geometric discontinuity refers to the sudden change in shape and size of the structure. Load discontinuity refers to the sudden change in the magnitude of the load applies. Material discontinuity refers to holes or uneven material distribution.

10. “Symmetry in the structure should be made use of.” Why is this so?
a) Memory requirement is increased
b) Memory requirement is reduced
c) Memory requirement is constant
d) Memory requirement is inconsistent

Explanation: By making use of symmetry in the structure for meshing, one can cut down on the memory allotted for the operation in the system. This facilitates for increasing the number of elements to enable a much refined mesh.

11. Which of the following defines the element aspect ratio?
a) Ratio of length to breadth in an element
b) Ratio of smallest to largest size in an element
c) Ratio of largest to smallest size in an element
d) Ratio of element weights

Explanation: Element aspect ratio is defined as the ratio of largest to smallest size in an element. Shape of the element plays an important role in the procedure of meshing. For optimal calculation and results, the aspect ratio should be as close to unity as possible.

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