Important point of Strength of material

Important point of Strength of material

• Stress : P/A =N/mm2
• Strain : Change in length / original length = No unit
• Hook's law = good for elastic limit
• Modulus of elasticity = linear stress/linear strain

• Poison ratio :  lateral strain / linear strain (Max. = 0.5)
• E = 210 kN/mm2
• Strain roseter = used to measure liner strain.
• Max. stress at smaller end in tapper bar
• bolt pass through pipe both are tightly fitted with nut and washer so bolt in tension tube in compression
• bar cooled at -5 degree c it develop tensile stress.
• Energy stored in body = strain energy
• Total strain energy stored in body = Resilience
• Max. strain energy stored in body = Proof resilience
• Proof resilience / Unit volume = Modulus of resilience 
• Strain energy suddenly loaded = 4 x Gradually loaded 
• Contraflex point = bending moment change sign (overhanging beam)(simply supported beam)
• Shear force = 0, Bending moment = max
• Bending moment at fix end = max
• In pure bending = bending is constant, shear is o

Important point of Strength of material

• Elastic strength

if depth double =elastic strength four times
if width double = elastic limit double
if length double = elastic strength 1/4th

• Natural axis shear force = 0
• Flinched beam is used to equal strength and compression.
• Torsional rigidity - " Torque required to produce twist one redian /unit length"

T/theta

• Torsional -" closely coil helical spring is subjected to axial "
• stiffness of spring = cd4/8D3n
• Spring index = Mean dia/ wire dia
• Closely coil spring 

Wire dia is double =  stiffness is 1/6th
No. of turrns is double = stiffness is 1/2
Spring cut in to haft = stiffness is double  

• Rivets

Rivets are made from ductile material.
Size of hole is grater , 25mm hole  = 23 mm rivet
Used for permanent fastener
Generally specified by shank diameter
Shank dia. is minor dia of thread
Center of rivet to nearest edge is margin
Caulking is  made for riveted make leak proof.

• Unwin formula = 6 x root  "t"
• Slenderness ratio = Length of column/ Least radius of gyration

Slenderness ratio <80 , Short column
Slenderness ratio <=100 , Long column                                       strength of material

• Dam created with cement Concentrate is meson dam.
• Hook 's law = good for elastic limit

Important point of Strength of material