# Finite Element Method Questions and Answers – Finite Analysis on Shell

This set of Finite Element Method Multiple Choice Questions & Answers (MCQs) focuses on “Finite Analysis on Shell”.

1. Which of the following is not an approach to generate shell elements?
a) Trapezoidal elements
b) Curved elements
c) Flat elements
d) Solid elements

Explanation: There are four approaches to generate shell elements for the finite element analysis. Along with Curved, flat and solid elements; there is another type which is referred to as degenerated solid elements. This is a special type of solid elements approach; where only degenerated bodies are made use of.

2. Discontinuities of slope incase of flat elements give rise to spurious moments.
a) False
b) True

Explanation: The given statement is true. Discontinuities of slope incase of flat elements give rise to spurious moments; this is one of the many disadvantages of making use of flat elements. Other disadvantages include – absence of curvature within the element, other limitations that arise during analysis of flat and shell elements consequently.

3. Which of the following is a disadvantage of using curved elements?
a) Easy to achieve inter element compatibility
b) Difficult to achieve intra element compatibility
c) Difficult to achieve inter element compatibility

Explanation: One of the many disadvantages of using Curved elements is, it is difficult to achieve inter element compatibility; which is not the case with flat elements. Other disadvantages include – difficulty in describing geometry making use of element data, acute satisfaction in rigid body modes etc.

4. Which of the following is an example of a solid shell element?
a) 3 node triangle
c) 5 node triangle
d) 4 node tetrahedron

Explanation: 4 noded tetrahedron is an example of a solid shell element. Triangular and quadrilateral elements are 2 dimensional elements, hence cannot be classified as solid shell elements. Other examples include – 8 node hexahedron, 20 node curved solid elements etc.

5. Solid shell elements possess very less degrees of freedom; making them desirable for use in shell elements.
a) False
b) True

Explanation: The given statement is false. In fact, solid shell elements possess very high number of degrees of freedom; making them uneconomic for computation and use in shell type elements. By making use of such elements, there is further scope for the concerned equations to become ill conditioned due to very large stiffness coefficients that are involved.
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6. Which of the following is an assumption for degeneration of elements?
a) Stress is uniform throughout
b) Strain is uniform throughout
c) Normal stresses and strains in the direction of thickness is zero
d) Stresses acting parallel to the surface are neglected

Explanation: There are two important assumptions considered while making use of the degeneration procedure. They are –

• Normal stresses and strains in the direction of thickness is zero.
• Normal to mid surface might not remain normal after deformation, but could remain straight.

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