# Tensile Properties

Tensile Properties

It indicates how a material will react when tensile force / load is applied on them.

1. a) Linear Elastic Region
2. b) Hook’s Law
3. c) Young’s Modulus / Modulus of Elasticity
4. d) Yield Strength Point
5. e) Yield Strength
6. f) Ultimate Tensile Strength
7. g) Breaking Strength

Tensile Test is done to determine the Tensile Properties

Tensile Testing Machines

Tensile Force (Load) is applied on the Specimen

Both the Load applied & Elongation are measured

A graph is plotted – Load along Y axis & Elongation along X axis.

We will get a Load vs Elongation Curve

Stress = Force (Load) / Cross Sectional Area

Strain = Elongation / Original Length

Denominators are constants [Cross Sectional Area & Original Length]

Numerators are Varying

Load vs Elongation Curve has the same shape of Stress vs Strain Curve

Load vs Elongation Curve can be converted to a Stress vs Strain Curve

The curve relates the applied stress to the resulting strain.

1. a) Linear-Elastic Region of the Curve – It is part of stress vs strain curve, where Stress and Strain increases linearly.

i.e., when the stress is reduced, the material will return to its original shape.

1. b) Hook’s Law – In the Linear-Elastic region of the Stress vs Strain curve, Ratio of Stress to Strain is a constant.
1. c) Modulus of Elasticityor Young’s Modulus of a material:

It is the Slope of the Line (y/x), in the Linear-Elastic region of the Stress vs Strain curve.    Unit is pascal (N/m2)

• Young’s Modulus is used to find out how much a rod or wire stretches under a tensile load.
1. d) Yield Strength Point: It is the point at which the Stress-Strain curve deviates from the straight-line relationship and Hook’s Law no longer applies.

From this point onwards some permanent (plastic) deformation occurs in the specimen.

1. e) Yield Strength is defined as the stress required to produce a small amount of plastic deformation.
2. f) Ultimate Tensile Strength is the maximum stress a material can withstand without breaking.

It is the maximum stress applied in a tension test and it is the highest point where the line is momentarily flat.

1. g) Breaking Strength is the stress at which fracture occurs
1. d) Yield Strength Point: It is the point at which the Stress-Strain curve deviates from the straight-line relationship and Hook’s Law no longer applies.

From this point onwards some permanent (plastic) deformation occurs in the specimen.

1. e) Yield Strength is defined as the stress required to produce a small amount of plastic deformation.
2. f) Ultimate Tensile Strength is the maximum stress a material can withstand without breaking.

It is the maximum stress applied in a tension test and it is the highest point where the line is momentarily flat.

1. g) Breaking Strength is the stress at which fracture occurs
•                        Failure of Marine Engg Materials under Tension
• Bolts are subjected to tension when they are over tightening
• Bolts in tension will neck down & deformation of the bolt starts when the applied stress crosses its yield strength.
• Microscopic voids between grain structures link up and voids get enlarged.
• The bolt begins to tear apart.
• Finally the edges tear away (bolt breaks).
• The sharp edge (shear lip) is the indicator where the bolt ultimately failed.
• The broken pieces mate together in what is called a cup and cone failure
• Failure of Marine Engg Materials under Shear

When a ship is floating in still water, the lightweight & dead weight  of the ship are supported by vertical force of  buoyancy (up thrust) acting on the hull.

The weight of a vessel is not uniformly distributed. Elements such as engines, cargo and superstructure provide an uneven distribution of weight along a vessels length.

This uneven weight distribution causes local differences in the vertical forces of buoyancy and the ship’s weight along the ship’s length .

These unbalanced net vertical forces, acting along the length of the ship, will induce Longitudinal shear forces causing the Hull Girders to Shear, at each section of the hull.

Hull Girders are Continuous Longitudinal Structures of a Ship.

Various Hull Girders are:

1     Strength Deck – Plating & Longitudinal

3     Side Shell – Plating & Longitudinal

5     Bottom Shell – Plating & Bottom Longitudinal

7     Inner Bottom – Plating & Longitudinal

9     Double Bottom Girder

10   Topside Tank Sloping Plating & Topside Tank Sloping Plating Longitudinal

12   Hopper Tank Sloping Plating & Hopper Tank Sloping Plating Longitudinal