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TORSION OF
NON-CIRCULAR SHAFTS
INTRODUCTION
Generally for power transmission, circular shafts are used because there is
uniform stress distribution along any radius of the shaft. Plane sections of the
shaft remain plane after the application of twisting moment, as a result there is
no distortion in the sections of shafts and change in volume of the shaft is zero.
For stationary torque application, non-circular shafts of different sections such
as square, rectangular, triangular, elliptical solid, or hollow are used.
Figure 1 Formation of ridges and valleys
The assumption that transverse sections of the shaft remain plane after the
applications of torque does not hold good for shafts of non-circular section. Only
the lines of symmetry remain straight; all other lines in the section go out of
plane and the section gets severely distorted. Figure 1 shows the undeformed
shaft of square section and deformed shape after the application of a twisting
moment along the axis of the shaft.
Figure 2 shows the formation of ridges and valleys in the square section of a
shaft. Shaft of rectangular section is subjected to axial torque T.
Figure 2 (a) Change of shape of cross-section (b) Warping
A rectangular shaft of section
2b × 2a, fixed at one end, is
subjected to axial torque T as
shown in Figure 3 which
produces shear stresses in the
shaft which are zero at centre
and maximum at the outer
surface, but varies from one
radial line to another radial line.
Figure 3 Shaft of rectangular section subjected to axial torque T
Figure 4 shows that the original plane cross-section has deformed or worked
out of its own plane. In general, torsion of a shaft which does not possess
circular symmetry produces deformation that involves rigid body rotation of
one cross-section with respect to another cross-section accompanied by
warping out of the original plane. Figure 4 shows four dotted lines AC, BD,
ac, bd, lines of symmetry remain straight, but all other lines in the cross-
section deform when the shaft is twisted.
Figure 4 Distortion in rectangular section
All non-circular sections are distorted under torsion to a greater or lesser
degree. For sections close to circle, these effects are less marked as in the
case of elliptical section.
The detailed analysis on torsion of non-circular shafts including the warping of
the sections requires a complicated analysis. However, the results of the
theory developed by St. Venant and Prandtl for the calculation of maximum
shear stress and angular twist in non-circular shafts will be summarized here.
section and 2a is the shorter side of the section
as shown in Figure 5.
RECTANGULAR SECTION Torque T = GJθ [Similar to M=EI(d2y/dx2)]
where GJ = Torsional rigidity of the shaft,
θ = angular twist per unit length, and
J = Polar moment of inertia: Ka3b
Angular twist,
The value of constant K depends upon the ratio of
, where 2b is the longer side of the rectangular
Figure 5 Rectangular section
r
L T
lengthunitLL
GJ
T
L
r
GJ
rT
GJ
rTG
rL
,
,
ab
bGKa
T3
The values of K for various ratios of are given in tables, such as
presented here.
Table Values of constants for rectangular section
Maximum shear stress, [for circular sections ]
where K1 is another constant again depending upon the ratio of .
J
Tr
JTa
K1
ab
ab
or
where
The constants K, K1, and K2 are presented in the Table.
Expressions for and can be approximately given as follows, and
then one does not need to refer to the table of constants.
where
For the sake of comparison let us take =1.5.
From tables K = 3.136, K1 = 1.696, K2 = 0.541
Maximum shear stress,
Angular twist per unit length
From approximate analysis Maximum shear stress,
ab
Angular twist per unit length
If we compare the results of maximum shear stress and angular twist, from
two analyses, we can find only negligible difference between the two analysis.
The maximum intensity of shear stress, , occurs at the centre of the longer side
for rectangular cross section as shown in Figure 6. Figure 7 shows the distortion of
the ends of a shaft of square section.
Figure 6 Shear stress distribution in shaft of rectangular section
Figure 7 warping of a square section
Example
A 50 mm × 25 mm rectangular steel shaft is subjected to a torque of 1.0 kNm.
What is the maximum shear stress developed in the shaft and what is the
angular twist per unit length? G = 80 GN/m2.
G = 80 GN/m2 = 80 × 109 N/m2 = 80 × 103 N/mm2
Longer side, 2b = 50 mm, (b = 25 mm)
Shorter side, 2a = 25 mm, (a = 12.5 mm)
Torque, T = 1.0 kNm = 1.0 × 106 Nmm
Maximum shear stress,
From tables for ba
TK
22
Angular twist per unit length,
θ
=
= 0.06987 × 10−3 radian / mm length
= 0.06988 radian / meter length
= 4.0 ° / meter length
Example
A rectangular shaft 6 cm × 4 cm made of steel is subjected to a
torque of 3000 Nm. What is the maximum shear stress developed in
the shaft and what is the angular twist per metre length? G = 80
kN/mm2. Use approximate relationship.
Torque, T = 3 kNm = 3 × 106 Nmm
Longer side, 2b = 6 cm, b = 3 cm = 30 mm
Shorter side, 2a = 4 cm, a = 2 cm = 20 mm
G = 80 kN/mm2
Maximum shear stress,
Angular twist per mm length
where
Exercise 6.1
A rectangular shaft of section 60 mm × 24 mm made of steel is subjected
to a torque such that maximum shear stress developed in shaft is 40
N/mm2. What is the magnitude of the torque and what will be the angular
twist in 1 m length of the shaft? G = 80 kN/mm2.
Take 1) values of constants from the table,
2) approximate values.
Compare the two results.
TORSION OF ELLIPTICAL SECTION SHAFT For the elliptical section shaft, the expressions for maximum shear stress and angular twist per unit length are
and
where b = semi-major axis and
a = semi-minor axis of ellipse.
Maximum shear stress occurs at the
ends of the minor axis as shown in
Figure 8, i.e. at the points B and D. Figure 8 Maximum shear stress occurs
at the ends of the minor axis
Figure 9 shows the contour lines of constant displacement. The convex
portions of the cross-section, where displacements in the direction of axis
of the shaft are positive, are shown by continuous lines. Where the surface
is depressed, depressions are shown by dotted lines.
Figure 9 Contour lines of displacement
Example A shaft of elliptical section with minor axis 2a and major axis 2b is subjected to a torque of 2 kNm. If the maximum shear stress in the shaft is not to exceed 80 N/mm2, determine the major and minor axes, if b = 1.5a. What will be the angular twist in a meter length in this shaft under the given torque? G = 80000 N/mm2. Maximum shear stress,
or
a3
=
Minor axis = 44 mm
Major axis = 66 mm
Angular twist per mm length
θ per meter length = 3.27 × 10–2 = 1.87°
Exercise 6.2
A shaft of elliptical section with major axis 60 mm and minor axis
40 mm is subjected to an axial twisting moment of 0.5 kNm.
What is the maximum shear stress developed in the section and
what is the angular twist per meter length?
G = 40 kN/mm2.
TORSION OF A SHAFT WITH EQUILATERAL TRIANGULAR SECTION
Figure 10 shows an equilateral triangle section of a shaft subjected to the
twisting moment T. Let’s assume a is the side of the equilateral triangle.
Maximum shear stress occurs at the center of the sides.
Angular twist per unit length
Maximum shear stress,
At the corners of the triangle,
i.e. at A, B, and C, shear
stress is zero. Figure 10 Shear stress distribution in equilateral triangular section
Example
A shaft of equilateral triangular section of side 40 mm is subjected to an axial
twisting moment T. Determine the magnitude of T if the maximum shear stress
is not to exceed 100 N/mm2. What will be the angular twist in 2 metres length
of the shaft?
G = 80000 N/mm2.
= 100 N/mm2
Side, a = 40 mm
Angular twist per meter length,
θ
=
= 0.0625 × 10−3 radians/mm length
= 0.0625 radians/m length
Angular twist in
2 meters length
= 0.0625 × 2
= 0.125 radians
= 7.162°
Exercise 6.3
A shaft of equilateral triangular section of side 60 mm is subjected to a
torque of 1.0 kNm.
Determine (i) maximum shear stress developed in shaft and (ii) angular
twist per meter length of the shaft.
G = 84 kN/mm2.
PRANDTL’S STRESS FUNCTION FOR TORSION
The stress function approach is also useful when dealing with torsion on a
prismatic element with a noncircular cross section. Airy’s stress function cannot
be used here since the general torsion problem does not fall into the category
of a plane elastic problem. Thus, for pure torsion, the equations of equilibrium
and compatibility must be reformulated.
Let’s consider the general cross-
section undergoing torsion in
Figure 11. A surface isolation
perpendicular to the rod axis is
also shown, where it can be seen
that the shear stresses xy and zx
act over a dydz element. Cross
shears xy and yx and xz and zx
are equal.
Figure 11 Torsion of a prismatic element
For equilibrium in the x direction, it will be assumed that sx is negligible. We
should note, however, that when torsion is applied to noncircular cross sections
without constraint in the x-direction, plane surfaces perpendicular to the
longitudinal axis will not remain plane and the surfaces warp. If the rod is
constrained from warping in the x direction, sx will develop. We are going to
assume that the rod is free in the x direction. Thus, for equilibrium of forces in
the x direction, neglecting the body force and the normal stress sx,
0
0
xzxxyx
zxxy
Fzyx
zy
s
xF
If a stress function (y, z), called the Prandtl’s stress function, exists such
that
y
z
zx
xy
The equilibrium equation is automatically
satisfied.
When deflections in terms of the angle of twist
are considered, the deflection of a point on the
isolated surface is as shown in Figure 12, from
which it can be seen that for small
Figure 12 Isolated surface
zvyw
022
yzzy
w
y
v
z
0
zy
zxxy or
Assuming that the rod is fixed at the origin of
xyz, we can represent the angle of twist per unit
length ', where =‘ x, and
xzv
xyw
For noncircular cross sections, the surface warps,
and in general the point will also deflect in the x
directon u. However, this is independent of x and
u = u (y, z). The strains xy and zx are
z
uy
z
u
x
w
y
uz
y
u
x
v
zx
xy
Since = [E/2(1+n)],
z
uy
E
y
uz
E
zx
xy
12
12
Writing the expression, using the above expressions, zy
xyzx
1
E
zy
xyzx
yz
uEE
z
zy
uEE
y
xy
zx
2
2
1212
1212
Substitution of results in
This equation is called the Poisson’s equation, it is the governing
equation for the torsional stress function .
At the boundary, the net shear stress must be tangent to the boundary.
Thus,
0 dzdyordz
dyxyzx
zx
xy
yzzxxy
1
2
2
2
2 E
zy
1
E
zzyy(x -1)
dy
dz
xy
zx
net
Substituting in results in
However, since = (y, z), the above equation can be written
yzzxxy
0
dz
zdy
y
0d
Since this requirement applies to the boundary, is constant along the
boundary of the cross section. The value of this constant is arbitrary
and is normally chosen to be zero. If the boundary of the cross section
is a well-behaved function of y and z such as a circle, ellipse, etc., the
equation of the boundary becomes an excellent stress function.
To relate the stress function to the transmitted torque T, as seen in the
figure, the net torque about the x axis due to the stresses on the dydz
element is (yzx – zxy)dydz. Thus, the total torque is
dydzzyT xyzx
Substitution of
gives
yzzxxy
dydzz
zy
yT
z
y
Let’s consider the first term in the integral. Integrating this with respect to
y by parts gives
dzdyydzdy
yydydz
yy
y
y
2
1
where y1 and y2 are boundary points for the dz slice. However, as stated
earlier, is zero at the boundary. Thus is zero at y1 and y2, and the first
term within the integral disappears, resulting in
dzdydzdy
yy
In a similar manner, the second integral gives identical results, so that we
have
dzdyT 2
Example
A solid circular shaft of radius ro is transmitting a torque. Determine the
corresponding shear stress distribution.
The equation for the boundary of a circle of radius ro in the xz plane is
y2 + z2 = ro2. Let’s try the following stress functon:
222
orzyk
where k is a constant. = 0 along the entire
boundary. To establish the value of k we can use
. It can be seen from the above
Prandtl’s stress function that polar coordinates
are more suitable to the problem. Let r2 =y2 + z2,
where r is a variable radial position.
dzdyT 2
y
ro
z
z
y
The infinitesimal area dydz can be replaced by 2prdr since at any given
position r, the stress function is constant. Thus, for this problem, the double
integral of reduces to a single integral, and dzdyT 2
r
dr rdrrrkTor
o 40
22
p
Integrating and solving for k results in
4 or
Tk
p
The polar moment of inertia of a circular cross section is J = (p/2)ro4. Thus,
J
Tk
2
Substituting k into the stress function, we get
222
2orzy
J
T
The shear stresses are determined as
J
Ty
J
Tzzxxy
We should note that at any given point, the net shear stress is given by
22
)( zxxynetx
J
Tryz
J
Tnetx 22
)(
Therefore,
which is identical to that used in
elementary strength of materials.
For the angle of twist, substitution of the stress function
into yields
EJ
T
E
J
T
J
T
12
1
If the total length of the bar is L, the angle of twist across the entire
length is , and thus,
1
2
2
2
2 E
zy
222
2orzy
J
T
L
12 12
GE
EJ
TL
which again agrees with the elementary strength of materials solution.
MEMBRANE ANALOGY
A German Scientist Prandtl, analyzed that the solution of a partial differential
equation that must be solved in the elastic torsion problem is mathematically
identical to that for a thin membrane, such as a thin rubber sheet stretched
over a hole, and the hole is geometrically similar to the cross-section of the
shaft under study. On one side of the thin sheet, or membrane, there is a light
air pressure. Following rules are followed for the analogous solution:
1.Shear stress at any point of the section (non-circular section of shaft) is
proportional to the slope of the stretched membrane at that point.
2.The direction of a particular shear stress at a point is at right angles to the
slope of the membrane at the same point.
3.Torque on the section is proportional to twice the volume enclosed by the
stretched membrane.
Figure 13 (a) shows that the area
bound by the edges of a thin rubber
sheet- membrane is of the shape of a
shaft of non-circular section. The
stretched sheet or membrane is
subjected to an internal pressure and
the membrane is deflected as shown in
Figure 13 (b). It should be noted that
the initial tension in membrane should
be large enough, so that when
membrane is blown up due to internal
air pressure, changes in tension can be
ignored. With the help of a travelling
microscope, deflection at grid points on
membrane can be noted down.
Figure 13 Deflection contour lines of membrane
(a)
(a)
And deflection contours (lines of
constant deflection) are plotted as
shown in Figure 13 (c). From deflection
contours, slope at any point of the
section can be determined, as shown by
a tangent at any point P of non-circular
section. Knowing the results of a
circular section shaft for a given torque,
the membrane is calibrated for a
circular section under a given
pretension σ, internal pressure p, and
membrane thickness.
Figure 13 Deflection contour lines of membrane
Membrane covering a curved cross-section
x
zy
yzx
yz
yz
xz
xzyz
yz
(from page 57)
yz
yz
yz
yz
xz
yz
T
T
T
T T
T
T
T T
T T
T T
T
TORSION OF
THIN WALLED
SECTIONS
Consider a shaft with thin walled
tubular section subjected to a
twisting moment T. The
thickness of the tube can vary,
and we have considered the
section of variable thickness as
shown in Figure 14 (a). At any
point along the periphery say t is
the thickness and is the shear
stress. Take a small element
abcd on the periphery of tubular
section, with thickness t1, at cd
and t2 at ab. Since there is
variation in thickness, there will
be variable shear stress. Figure 14 (a) Variable thin walled section (b) Sections of variable thickness
At cd, thickness is t1, and shear stress is 1.
At ab, thickness is t2, and shear stress is 2.
Axial length of element is dl. An enlarged view of the element is shown
in Figure 14 (b).
Complementary shear stress on face dd′c′c —1
Complementary shear strain on face a′b′ba —2
For equilibrium of forces
t1 dl 1 − τ2dl 2 = 0
or t1 1 = t2 2 = t q (for any thickness t)
Figure 15 Element of variable thin walled section
Let us consider a small element of length ds along the periphery, say thickness is t
Shear force acting on the small element, dQ = tds =qds
= shear flow × length. (Figure 15)
Moment of the force dQ at the centre O of the shaft
dT = hdQ = hq ds where q is the shear flow q = . t.
where dT = q 2 dA (where dA is the area of small triangle)
Total torque,
ds − base of triangle (shaded area)
h = altitude of the triangle.
dT = q (hds)
where A is the mean area enclosed by the centre line of the thin tubular
section as shown for a rectangular section in Figure 16.
Figure 16 Thin rectangular section
A = B × D, area bounded by outer
line of section. This equation T = 2q A is generally known as Bredt-Botha equation.
qAdAqT 22
Let us determine the angular twist in the shaft. Consider a small element abcd of
axial thickness dL. Due to the twisting moment point d is displaced to d″ and a is
displaced to a″.
Shear force dQ on small element, = τtds
Say displacement of the edge ab or cd = δ
Shear strain,
Strain energy for the small element =
dL
But shear strain,
Shear strain energy
but
So, shear strain energy,
Moreover,
Let us take dL = 1, so that we can find out strain energy per unit length
Total strain energy per unit length
modulusShear
stressShear
G
t
dsdL
GA
Tdu
2
2
8
tdsdL
2
1
Using the Castigliano’s theorem, angular twist θ per unit length
Again,
where integral
is the summation of (length/thickness) along the periphery of thin tubular section.
t
ds
GA
Tu
2
2
8
Example
A thin walled box section 3a × 2a × t is subjected to a twisting moment T. A
solid circular section of diameter d is also subjected to the same twisting
moment. Determine the thickness of the box section (a) if the maximum shear
stress developed in box section is the same as that in solid circular section, and
d = 2a, and (b) if the stiffness for both is the same under the same torque.
The figure shows the thin walled section 3a × 2a × t and a solid circular section of diameter d.
Maximum shear stress in circular section,
Shear flow in box section,
Taking a ≫ t (side ≫ thickness)
Maximum shear stress in box section,
But
or
Angular twist for solid circular shaft
or
where
but d = 2a
So,
Angular twist for the thin box section,
where area A = 3a × 2a = 6a2
and
But θ = θ′
So,
Exercise 6.4
A shaft of hollow square section of outer side 48 mm and inner side 40
mm is subjected to a twisting moment such that the maximum shear
stress developed is 50 N/mm2. What is the torque acting on the shaft and
what is the angular twist if the shaft is 1.6 m long?
G = 80000 N/mm2.
TORSION OF THIN RECTANGULAR SECTIONS
Figure 17 shows a thin rectangular section subjected to the torque T.
Thickness t of the section is small in comparison to its width b (b>>t).
This section consists of only one boundary. In this case maximum shear
stress occurs at .
Figure 17 Shear stress flow as in thin rectangular sectors
If
θ = angular twist per unit length
T = torque on the section
T =
2t
y
Gbt 3
31
Angle of twist per unit length,
= maximum shear stress
These results can be applied to sections built up of rectangular strips and
having only one boundary such as angle section, channel section, T section
and I section as shown in Figure 18.
Figure 18 Various cross sections
3
31
bt
TG
2
3
bt
T
In the case of channel section and I section, Torque,
Angle of twist per unit length,
In the case of Angle section and T section,
G = 8 × 104 N/mm2 = 8 × 106 N/cm2
Torque T = 2 kNm = 2 × 105 N cm
2 Flanges, b1 = b3 = 10 cm, t3 = 2 cm
1 Web b2 = 28 cm, t2 = 1 cm
Example An I section with flanges 10 cm × 2 cm (b1 = b3 x t3) and web
28 cm × 1 cm (b2 x t2) is subjected to a torque T= 2 kNm. Find the maximum
shear stress and angle of twist per unit length. G = 80,000 N/mm2.
Maximum shear stress,
Angular twist per unit length,
Exercise 6.5
A T-section with flange 10 cm × 1 cm and web
19 cm × 0.8 cm is subjected to a torque of 200 Nm. Find the
maximum shear stress and angle of twist per meter length.
G = 82 kN/mm2
TORSION OF THIN WALLED MULTI-CELL SECTIONS
The analysis of thin walled closed sections can be extended to multi-cell
sections. Let’s consider a two cell section as shown in Figure 19. Say the
shear flow in cell 1 is q1, in cell 2 it is q2 and in the web, shear flow is q3.
Now consider the equilibrium of shear forces at the junction of the two
cells, taking a small length δl, along the axis of the multi-cell section. The
complementary shear stresses 1, 2, and 3 are shown in the longitudinal
sections of length δl each with thicknesses t1, t2, and t3, respectively.
Figure 19 Multi cell sections
δl
For the equilibrium along the direction of the axis of multi-cell tubular section:
1t1 δl − 2t2 δl − 3t3 δl = 0
or 1t1 = 2t2 + 3t3
or q1 = q2 + q3
shear flow, q1 = shear flow q2 + shear flow, q3.
This is equivalent to fluid flow dividing itself into two streams:
Shear flow in web, q3 = q1 – q2
Twisting moment T1 about O due to q1, flowing in cell 1.
T1 = 2 q1 A1
where A1 = area enclosed by the centre line of cell 1.
δl
Twisting moment T2 about O due to q2 in cell 2: T2 = 2 q2 (A2 + A′1) − 2 q2 A′1 where 2 q2 A′1 is the twisting moment due to shear flow q2 in the middle web.
Total twisting moment,
T = T1 + T2
= 2 q1 × A1 + 2 q2 × A2
For continuity, the angular twist per unit length in each cell will be the
same. For closed thin sections
But in this case shear flow is changing, therefore
Say,
for cell 1 including web
for cell 2 including web
for the web
For cell 1,
For cell 2,
Shear flow q1, q2, and angular twist θ can be worked out using the equations derived.
Example The figure shows the dimensions of a double walled cross-
section in the form of a rectangle and a triangle. A torque of 4 kNm is
applied. Calculate the shear stress in each part and the angle of twist per
meter length. G = 82 kN/mm2.
Say,
shear flow in rectangular cell= q1 and shear flow in triangular cell = q2
Area, A1 = 150 × 100
= 15 × 103 mm2
Area,
Line integrals,
Now torque,
T = 2q1 × A1 + 2q2 × A2
4000 × 103 Nmm = 2 × 15 × 103 × q1 + 2 × 7.5 × 103 × q2 (i)
2000 = 15q1 + 7.5q2
But θ in cell 1 = θ in cell 2
So,
But
Substituting in Eq. (ii), we get 130q1 − 60q2 = 320q2 − 120q1 or 250q1 = 380q2 or q1 = 1.52q2 (iii)
Substituting in Eq. (i), we get 15 × 1.52q2 + 7.5q2 = 2000 or shear flow
1, shear stress in rectangular part
2, shear stress in triangular part
3, shear stress in web
Exercise 6.6
A steel girder of the section is shown in the figure. It has a uniform thickness
of 12 mm throughout. What is the allowable torque if maximum shear stress
is not to exceed 30 MPa? What is the angular twist per meter length of the
girder? What is the shear stress in middle web of the section?
G = 82 kN/mm2.
Example
A shaft of rectangular cross section is subjected to a torque of 0.8 kNm
and the maximum permissible shear stress in the shaft is 40 N/mm2. If
the ratio of breadth to depth is 1.5, determine the size of the shaft and
the angle of twist in a length of 4 m.
G = 78.4 kN/mm2.
Torque T = 0.8 × 106 Nmm = 800 × 103 Nmm
Larger side = 1.5 × shorter side (a)
b = 1.5 a
Maximum shear stress = 40 N/mm2
(From page 10)
or
14.2857 a3 = 800 × 103 Nmm
a3 = 56 × 103 mm3
Shorter side, a = 38.2 mm
Longer side, b = 1.5 × 38.2 = 57.3 mm
Angle of twist
where
(From page 10)
Example
A closed tubular section of mean radius R and radial thickness t and a
tube of the same radius and thickness but with a longitudinal slit are
subjected to the same twisting moment T. Compare the maximum shear
stress developed in both and also compare the angular twist in these
tubes.
Mean radius = R
Thickness = t
For Closed Tubular Section
Maximum shear stress
Angular twist per unit length
tA
T
2
tR
T
2 21p
t
R
RG
TL
t
ds
AG
TL p
p
2
4 m 1
4 422
Tubular section with a small slit. This can be treated as a thin rectangular section
of width 2pR and thickness t.
Maximum shear stress,
Angular twist per unit length,
It is seen that the closed tubular section is much more stronger and stiffer than
the open tubular section with a slit.
Example
A shaft made of plastic is of elliptical cross-section as shown in the figure. If
it is subjected to torsional loading as shown, determine the shear stress at
point A. Also determine the angle of twist at the end B. Gplastic = 15 GPa.
T, Torque at the point A = 60 + 30 = 90 Nm 90 × 103 Nmm
Semi-major axis of ellipse, b = 50 mm
Semi-minor axis of ellipse, a = 20 mm.
Shear stress at point A (end of the minor axis)
2
2
3
2/86.2
5020
109022mmN
ba
T
pp
Torque for 2 m length, T1 = 60 Nm
Torque for another 2 m length, T2 = 60 + 30 = 90 Nm
Angular twist,
So,
Exercise 6.7
A shaft section consists of a hollow
rectangular section and a solid
rectangular section as shown in the
figure. Composite shaft is
subjected to a twisting moment of
100 Nm. Determine (i) torque
shared by hollow and solid section,
(ii) maximum shear stress
developed in both the sections, (iii)
angular twist per meter length in
shaft if G = 25 × 103 N/mm2.