Chapter 3:Stresses And Strains

Problem 3.1,Page no.54

In [65]:
import math

#Initilization of Variables

P=40 #mm #Force applied to stretch a tape
L=30 #m #Length of steel tape
A=6*1 #mm #Cross section area
E=200*10**9*10**-6 #KN/m**2 #Modulus of Elasticity

#Calculations

sigma_L=(P*L*10**3)*(A*E)**-1 #mm 

#Result
print"The Elongation of steel tape is",round(sigma_L,4),"mm"
The Elongation of steel tape is 1.0 mm

Problem 3.2,Page no.54

In [4]:
import math

#Initilization of VAriables


#D=(D_0-2) #cm #Inside Diameter of cyclinder
#A=(pi*(D_0-1)) #cm**2 #Area of cross-section
#L=(pi*(D_0-1)*5400) #N #Crushing load for column
F=6 #Factor of safety
T=1 #cm #wall thickness of cyclinder

#S=L*F**-1
#After Simplifying,we get
S=600*10**3

#Calculations

D_0=(S*F)*(pi*54000)**-1+1 #cm #Outside diameter of cyclinder

#Result
print"The outside Diameter of cyclinder is",round(D_0,2),"cm"
The outside Diameter of cyclinder is 22.22 cm

Problem 3.3,Page no.56

In [25]:
import math 

#Initilization of variables

P=800 #N #force applied to steel wire
L=150 #m #Length of steel wire
E=200 #GN/m**2 #Modulus of Elasticity
d=10 #mm #Diameter of steel wire
W=7.8*10**4 #N/m**3 #Weight Density of steel
#A=(pi*4**-1)*(d)**2 #m**2

#After simplifying Area,we get
A=7.85*10**-5 #m**2

#calculation (Part-1)

#Elongation Due to 800N Load 
dell_L_1=(P*L*10**-3)*(A*E*10**9*10**-6)**-1 #mm

#calculation (Part-2)

#Elongation due to Weight of wire 
dell_L_2=((pi*4**-1)*150*W*L*10**-3)*(2*A*E*10**7)**-1 #mm

#calculation (Part-3)

#Total Elongation of wire
dell_L_3=dell_L_1+dell_L_2


#Result
print"The Elongation due to 800N Load is",round(dell_L_1,2),"mm"
print"The Elongation due to Weight of wire is",round(dell_L_2,2),"mm"
print"Total Elongation of wire is",round(dell_L_3,2),"mm"
The Elongation due to 800N Load is 7.64 mm
The Elongation due to Weight of wire is 4.39 mm
Total Elongation of wire is 12.03 mm

Problem 3.4,Page no.55

In [29]:
import math

#Intilization of variables

d=10 #mm #Diameter of Punching Hole
t=4 #mm #Thickness of Mild Steel Plate
tou=320 #N/mm**2 #Shear Strength of mild Steel

#Calculations

#Force Required for punching the hole
P=tou*pi*d*t #N 

#Area of punch in contact with the plate surface
A=(pi*4**-1*d**2) #mm*2

#Compressive stress
sigma_c=P*A**-1 #N/mm*2

#Result
print"Force Required for punching the hole is",round(P,2),"N"
print"Compressive stress is",sigma_c,"N/mm*2"
Force Required for punching the hole is 40212.39 N
Compressive stress is 512.0 N/mm*2

Problem 3.6,Page no.57

In [67]:
import math

#Initilization of variables

P=200*10**3 #N
L_1=0.10 #mm #Length of of portin AB
L_2=0.16 #mm #Length of of portin BC
L_3=0.12 #mm #Length of of portin CD
E=200*10**9 #N
d_1=0.1 #cm
d_2=0.08 #cm
d_3=0.06 #cm
A_1=(pi*4**-1)*(0.1)**2 #mm**2
A_2=(pi*4**-1)*(0.08)**2 #mm**2
A_3=(pi*4**-1)*(0.06)**2 #mm**2

#Calculations

dell_L_1=(P*L_1*10**3)*(A_1*E)**-1 #mm
dell_L_2=(P*L_2*10**3)*(A_2*E)**-1 #mm
dell_L_3=(P*L_3*10**3)*(A_3*E)**-1 #mm
dell_L=dell_L_1+dell_L_2+dell_L_3 #mm

#Result
print"Total Elongation of steel bar is",round(dell_L,3),"mm"
Total Elongation of steel bar is 0.087 mm

Problem 3.7,Page no.57

In [44]:
import math

#Initilization of variables

#from F.B.D,we get
P_1=50 #KN
P_2=20 #KN
P_3=40 #KN

d=0.02 #mm #Diameter of steel bar
L_1=0.4 #mm
L_2=0.3 #mm
L_3=0.2 #mm
E=210*10**9 #N

#After simplifying Area,we get
A=pi*10**-4 #m**2 #Area of cross section

#Calculations

sigma_AB=P_1*1000*A #N/m**2
sigma_BA=P_2*1000*A #N/m**2
sigma_CD=P_3*1000*A #N/m**2
dell_L=((P_1*L_1+P_2*L_2+P_3*L_3)*(A*E)**-1)*10**6 #mm

#Result
print"Total Elongation of Steel bar is",round(dell_L,3),"mm"
Total Elongation of Steel bar is 0.515 mm

Problem 3.8,Page no.58

In [26]:
import math
import numpy as np

#Initilization of variables

#R_a+R_c=25 #KN #R_a,R_b are reactions at supports A and C respectively
L_ab=2 #m
L_bc=3 #m

#Calculation

#From F.B.D,we get
#dell_L_AB=(R_a*L_AB)*(A*E)**-1 #Elongation of portion AB
#dell_L_BC=(R_c*L_BC)*(A*E)**-1 #Compression of portion BC

#After simplifying above equations we get,
#R_a=(1.5)*R_c #KN
#R_a+R_c=25 #KN
#Solving the above simultaneous equations using matrix method
A=np.array([[1,-1.5],[1,1]]) #Here the coefficients of the first equations of unknowns are setup
B=np.array([0,25]) #Here the RHS of both equations are setup
C=np.linalg.solve(A,B)

#print C[0] #Prints the first element in the vector C
#print C[1] #Prints the second element in the vector C

#Result
print"The reaction at support A is",round(C[0],2),"KN"
print"The reaction at support C is",round(C[1],2),"KN"
The reaction at support A is 15.0 KN
The reaction at support C is 10.0 KN

Problem 3.9,Page no.59

In [17]:
import math

#Initilization of variables

#P is the force acting on the bar BC compressive in nature and force on AB is (100-P) Tensile in nature
E=200*10*9 #N
A_1=3*10**-4 #cm**2 #Area of AB
A_2=4*10**-4 #cm**2 #Area of BC
L=1.5 #cm #Length of bar

#Calculations

#The total elongation of bar
#(((100-P)*10**3*1.5)*(3*10**-4*E)**-1)-((P*10**3*1.5)*(4*10**-4*E)**-1)=0 

#The total elongation of bar is limited to 1
#(25-0.4375*P)*10**-4=1*10**-3

#After simplifying above equation we get,
P=-(10-25)*0.4375**-1 #KN #Total elongation of bar
F_AB=100-P #KN #force in AB
F_BC=P #KN #Force in BC
sigma_AB=(((F_AB)*(3*10**-4)**-1)*10**-3) #KN #Stress in AB
sigma_BC=((F_BC)*(4*10**-4)**-1*10**-3) #KN #Stress in Bc


#Result
print"F_AB",round(F_AB,2),"KN"
print"F_BC",round(F_BC,2),"KN"
print"sigma_AB",round(sigma_AB,2),"KN"
print"sigma_BC",round(sigma_BC,2),"KN"
F_AB 65.71 KN
F_BC 34.29 KN
sigma_AB 219.05 KN
sigma_BC 85.71 KN

Problem 3.12,Page no.61

In [11]:
import math

#Initilization of variables

P=500 #KN #Safe Load
d=20 #mm #steel rod diameter
n=4 #number of steel rod
sigma_c=4 #N/mm**2 #stress in concrete 
#E_S*E_c**-1=15


#Calculations

A_s=4*pi*4**-1*d**2 #mm**2 #Area os steel rod
sigma_s=15*sigma_c #N/mm**2 #stress in steel

#P=sigma_s*A_s+sigma_c*A_c 

#After substituting and simplifying above equation we get,

A_c=(P*10**3-sigma_s*1256)*(sigma_c)**-1 #mm**2 #Area of the concrete
X=(A_s+A_c)**0.5 #mm #Total cross sectional area
P_s=A_s*sigma_s*10**-3 #KN #Load carried by steel

#Result
print"Load carried by steel is",round(P_s,2),"KN"
print"stress induced in steel is",round(sigma_s,3),"KN"
print"cross sectional area of column is",round(X,2),"mm"
Load carried by steel is 75.4 KN
stress induced in steel is 60.0 KN
cross sectional area of column is 327.74 mm

Problem 3.13,Page no.62

In [1]:
import math

#Initilization of variables

A_s=500 #mm**2
E_s=200000
E_al=80000
A_al=1000


#Calculations

#(P_al*L_al)*(A_al*E_al)**-1+(P_s*L_s)*(A_s*E_s)**-1=1*2**-1 

P=1*1000**-1*((A_s*E_s*A_al*E_al)*(A_s*E_s+A_al*E_al)**-1) #N
P_s=P_al=P #N
sigma_t=P_s*A_s**-1 #N/mm**2 #Tensile stress in bolt
sigma_c=P_al*A_al**-1 #N/mm**2 #Compressive stress in Aluminium tube

#result
print"Tensile stress in bolt is",round(sigma_t,2),"N/mm**2"
print"Compressive stress in Aluminium tube is",round(sigma_c,2),"N/mm**2"
Tensile stress in bolt is 88.89 N/mm**2
Compressive stress in Aluminium tube is 44.44 N/mm**2

Problem 3.14,Page no.63

In [1]:
import math

#Initilization of variables

A=1600 #mm**2 #Area of the Bar
P=480*10**3 #N #Load
dell_L=0.4 #mm #Contraction of metal bar
L=200 #mm #Length of metal bar
sigma_t=0.04 #mm #Guage Length
t=40

#Calculations

sigma_L=dell_L*L**-1
E=((P*L)*(A*dell_L)**-1*10**-3) #N/mm**2 #Young's Modulus 
m=t*sigma_t**-1*sigma_L


#Result
print"The value of Young's Modulus  is",round(E,2),"N/mm*2"
print"The value of Poissoin's ratio is",round(m,2)
The value of Young's Modulus  is 150.0 N/mm*2
The value of Poissoin's ratio is 2.0

Problem 3.15,Page no.63

In [21]:
import math

#Initilization of variables

A_s=0.003848 #m**2 #Area of steel bar
A_al=0.003436 #m**2 #Area of Aluminium tube
E=220*10*9 #N #Young's modulus of steel
E=70*10*9 #N #Young's modulus of aluminium
P=600*10**3 #N #Load applied to the bar
#dell_L_al-dell_L_s=0.00015 #mm #difference between strain in aluminium bar and steel bar

#Calculations


#Let the aluminium tube be compressed by dell_L_al and steel bar by by dellL_s
#dell_L_al=sigma_al*E_al**-1*L_al
#dell_L_s=sigma_s*E_s**-1*L_s

#After substituting and simplifying above equation we get,
#((sigma_al*70**-1)-(sigma_s*220**-1))=300000               #(equation 1)

#After simplifying above equation we get,
#sigma_al=17462.165*10**4-1.1199*sigma_s                    #(equation 2)

#Now substituting sigma_al in equation(1)
#((17462.165*10**4-1.1199*sigma_s)*(70)**-1)-(sigma_s*220**-1)=300000

#After simplifying above equation we get,

sigma_s=-((300000-249.4594*10**4)*0.0205444**-1)*10**-6 #MN/m**2 #stress developed in steel bar
#sigma_al=17462.165*10**4-1.1199*sigma_s
sigma_al=(17462.165*10**4-1.1199*106822005.02)*10**-6


#Result
print"stress developed in steel bar is",round(sigma_s,2),"MN/m**2"
print"stress developed in aluminium bar is",round(sigma_al,2),"MN/m**2"
stress developed in steel bar is 106.82 MN/m**2
stress developed in aluminium bar is 54.99 MN/m**2

Problem 3.16,Page no.64

In [43]:
import math

#Initilization of variables

E=200 #GN/m**2 #Modulus of elasticity
alpha=11*10**-6 #per degree celsius #coeffecient o flinear expansion of steel bar
L=6 #m #Length of rod


#Calculations 

#(Part-1) #IF the walls do not yield

t=58 #degree celsius #Fall in temperature #(t=80-22)
dell=alpha*t #strain
sigma=E*10**9*dell*10**-6 #MN/m**2 #Stress
A=pi*4**-1*6.25*10**-4 #mm**2 #Area of wall and rod
P=sigma*10**6*A*10**-3 #KN #Pull Exerted

#(Part-2) #IF the walls yield together at the two ends is 1.15 mm

L_2=L*(1-alpha*t) #m #Length of rod at 22 degree celsius
L_3=L-L_2 #m #Decrease in Length 

#As the walls yield by 1.5 mm, actual decrease in length is
L_4=L_3-0.0015 #m 
dell_2=L_4*L**-1 #strain 
P_2=E*10**9*dell_2*A*10**-3 #KN

#Result
print"Pull Exerted by the rod:when walls do not yield",round(P,2),"KN"
print"                       :when total yield together at two ends is 1.5 mm",round(P_2,2),"KN"
Pull Exerted by the rod:when walls do not yield 62.64 KN
                       :when total yield together at two ends is 1.5 mm 38.09 KN

Problem 3.17,Page no.65

In [54]:
import math

#Initilization of variables

D=4.5 #cm #External Diameter of tube
d=3 #cm #Internal diameter of tube
t=3 #mm #thickness of tube
t_1=30 #degree celsius
t_2=180 #degree celsius #when metal heated
L=30 #cm #Original LEngth
alpha_s=1.08*10**-5 #Per degree celsius #coefficient of Linear expansion of steel tube
alpha_c=1.7*10**-5 #Per degree celsius #coefficient of Linear expansion of copper tube
E_s=210 #GPa #Modulus of Elasticity of steel 
E_c=110 #GPA #Modulus of Elasticity of copper

#Calculation

#For Equilibrium of the system, Total tension in steel=Total tension in copper

#sigma_s*A_s=sigma_c*A_c (equation 1)

A_c=pi*4**-1*d**2 #cm**2 #Area of copper
A_s=pi*4**-1*(D**2-d**2) #cm**2 #Area of steel

#simplifying equation 1
#sigma_s=1.785*sigma_c

T=t_2-t_1 #change in temperature

#Actual expansion of steel=Actual expansion of copper
#alpha_s*T*L+sigma_s*E_s**-1*L=alpha_c*T*L-sigma_c*E_c**-1*L

#After substituting values in above equation and simplifying we get

sigma_c=(930*10**5*1.7591**-1)*10**-6 #MN/m**2 #Stress in copper
sigma_s=1.785*sigma_c #MN/m**2 #Stress in steel

#Increase in Length of either component
L_2=(alpha_s*T+sigma_s*10**6*(E_s*10**9)**-1)*L

#Result
print"stress in copper bar is",round(sigma_c,2),"MN/m**2"
print"stress in steel bar is",round(sigma_s,2),"MN/m**2"
print"Increase in Length is",round(L_2,3),"cm"
stress in copper bar is 52.87 MN/m**2
stress in steel bar is 94.37 MN/m**2
Increase in Length is 0.062 cm

Problem 3.18,Page no.66

In [60]:
import math

#Initilization of variables

t_1=15 #degree celsius #temperature of steel bar
t_2=315 #degree celsius #raised temperature 
E_s=210 #GPa #Modulus of Elasticity of steel bar
E_c=100 #GPa #Modulus of Elasticity of copper bar
dell_L=0.15 #cm #Increase in Length of bar

#Calculation

#For Equilibrium of the system, Tension in steel bar = Tension in copper bar
#sigma_s*A_s = sigma_c*2*A_c
#sigma_S=2*sigma_c

#Actual expansion of steel = Actual expansion of copper
#L*alpha_s*T+sigma_s*E_s**-1*L = L*alpha_c*T-sigma_c*E_c**-1*L (Equation 1)

T=t_2-t_1 #per degree celsius #change in temperature

#After substituting values in above equation and simplifying we get
sigma_c=(1650*10**5*1.9524**-1)*10**-6 #MN/m**2 #Stress in copper
sigma_s=2*sigma_c #MN/m**2 #Stress in steel

#Actual Expansion of steel bar 
#L*alpha_s*T+sigma_s*E_s**-1*L = L*alpha_c*T-sigma_c*E_c**-1*L 
#After substituting values in above equation and simplifying we get
L=0.15*10**-2*0.0044048**-1 #m

#Result
print"Stress in copper bar is",round(sigma_c,2),"MN/m**2"
print"Stress in steel bar is",round(sigma_s,2),"MN/m**2"
print"Original Length of bar is",round(L,2),"m"
Stress in copper bar is 84.51 MN/m**2
Stress in steel bar is 169.02 MN/m**2
Original Length of bar is 0.34 m

Problem 3.19,Page no.67

In [64]:
import math

#Initilization of variables

L=100 #m #Length of rod
A=2 #cm**2 #cross sectional area
rho=80 #KN/m**3

#Calculatiom
W=A*10**-4*L*rho #KN

sigma_s=10+1.6 #KN #Rod experiencing max tensile stress when it is at top performing upstroke
sigma_s_2=sigma_s*10**3*200**-1 #N/mm**2 #corresponding stress at this moment

sigma_c=1 #KN ##Rod experiencing max compressive stress at its lower end,free from its own weight
sigma_c_2=sigma_c*10**3*200**-1 #corresponding stress at this moment

#Result
print"Tensile stress in bar",round(sigma_s_2,2),"N/mm**2"
print"Compressive stress in bar",round(sigma_c_2,2),"N/mm**2"
Tensile stress in bar 58.0 N/mm**2
Compressive stress in bar 5.0 N/mm**2

Problem 3.20,Page no.68

In [6]:
import math

#Initilization of variables

sigma=0.012 #strain
P=150 #KN   #Total Load on the Post
E=1.4*10**4 #N/mm**2 #modulus of elasticity
#b be the width of the post in mm
#2b is the longer dimension of the post in mm

#Calculations

#We know,
#sigma=(P*(A*E)**-1) 

#After substituting values and simplifying, we get
b=((150*10**3)*(0.012*1.4*2*10**4)**-1)**0.5
q=2*b #mm #Longer dimension of post

#Result
print"Width of post is",round(b,2),"mm"
print"Longer dimension of post is",round(q,2),"mm"
Width of post is 21.13 mm
Longer dimension of post is 42.26 mm