AIRCRAFT STRUCTURES-II
2 Marks Questions with Answers
UNIT 1
1. Define
(a) Principal axis
(b) Neutral axis and give an expression to determine them.
(a) If the two axes about which the product of inertia is found, are such, that the
product of inertia becomes zero, the two axes are then called principal axes.
Ixy = 0
The product of inertia is zero.
xydA o
I
xy
∫
(b)In a beam subjected to bending the line of zero stress; a transverse section of the
longitudinal plane, or neutral surface, which passes through the centre of area of the section.
I
tan α −
uu
tan θ
I
vv
Where α =The angle of the straight line passing through the centroid G of the section,
which is inclined with UU.
2. Explain how unsymmetrical bending is developed in a beam?
(i) The section is symmetrical like I section, rectangular section, circular section, but he
load-line is inclined to both the principal axes.
(ii) The section itself is unsymmetrical like angle section or a channel section and load line
is along any centroidal axis.
3. Write down the expression for orientation of neutral axis of beam with unsymmetrical
cross section in z-x plane and subjected to bending moments Mx and Mz.
tan α z xx −
M I M I
x xz
x zz −
M I M I
y xz
, 4. Bending of a symmetric section subject to a skew load will be (symmetric /
un-symmetric ) Explain.
Ans. Un symmetric.
When the trace of the plane of the applied moment does not coincide with any
of the principal axes of inertia then this type of bending is called un-symmetrical or
non-uni-planar bending.
5. In unsymmetrical bending, the neutral axis passes through the centroid of the
cross section. (True/false).
Ans.; True.
6. A rectangular cross section is subject to a skew load. Mark the neutral axis and
sketch the bending stress distribution.
Bending stress at A = Tensile
Bending stress at B = Same at A, but compressive
7. Explain anyone method to obtain the bending stress due to unsymmetrical
bending. Principal axis method
2 Marks Questions with Answers
UNIT 1
1. Define
(a) Principal axis
(b) Neutral axis and give an expression to determine them.
(a) If the two axes about which the product of inertia is found, are such, that the
product of inertia becomes zero, the two axes are then called principal axes.
Ixy = 0
The product of inertia is zero.
xydA o
I
xy
∫
(b)In a beam subjected to bending the line of zero stress; a transverse section of the
longitudinal plane, or neutral surface, which passes through the centre of area of the section.
I
tan α −
uu
tan θ
I
vv
Where α =The angle of the straight line passing through the centroid G of the section,
which is inclined with UU.
2. Explain how unsymmetrical bending is developed in a beam?
(i) The section is symmetrical like I section, rectangular section, circular section, but he
load-line is inclined to both the principal axes.
(ii) The section itself is unsymmetrical like angle section or a channel section and load line
is along any centroidal axis.
3. Write down the expression for orientation of neutral axis of beam with unsymmetrical
cross section in z-x plane and subjected to bending moments Mx and Mz.
tan α z xx −
M I M I
x xz
x zz −
M I M I
y xz
, 4. Bending of a symmetric section subject to a skew load will be (symmetric /
un-symmetric ) Explain.
Ans. Un symmetric.
When the trace of the plane of the applied moment does not coincide with any
of the principal axes of inertia then this type of bending is called un-symmetrical or
non-uni-planar bending.
5. In unsymmetrical bending, the neutral axis passes through the centroid of the
cross section. (True/false).
Ans.; True.
6. A rectangular cross section is subject to a skew load. Mark the neutral axis and
sketch the bending stress distribution.
Bending stress at A = Tensile
Bending stress at B = Same at A, but compressive
7. Explain anyone method to obtain the bending stress due to unsymmetrical
bending. Principal axis method
