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Draw the stress-strain curve for ductile and brittle material also. Explain factor of safety with the help of stress-strain diagram of both
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1. Stress-Strain diagram for Ductile material

Considering low Carbon Steel having Carbon content less 0.15% and its example is Mild Steel. • Point A is the proportionality limit, up to A, stress is directly proportional to strain i.e Hook's law followed.
• Point B is the elastic limit.
• Point C is the upper yield point. At upper yield point, the resistance suddenly decreases. Therefore, stress is also decreased, this is the particular property of mild steel.
• Point D is the lower yield point which is the stable point for the design, the yield strength is considered to lower yield point
• Point F is the ultimate point. At point F necking starts and due to necking 45-degree micro cracks generates.
• Point G is the breaking point. At G component break into two pieces and failure is the cup-cone failure.The cup-cone failure is a shear failure.

• Stress-Strain diagram for Brittle material OA is non-linear elastic AB is the Strain Hardening.

• Brittle material never yields, a point similar to yield point is first cracking point, where simple cracks develop; which may expand further leading to failure.
• A point is the first cracking point. After first cracks develop, the material undergoes an increase in strain by widening the crack and fails almost at the same stress. Therefore for all calculation in brittle material design stress is ultimate or breaking stress i.e Sut.

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1. Stress-Strain diagram for Ductile material

Considering low Carbon Steel having Carbon content less 0.15% and its example is Mild Steel. • Point A is the proportionality limit, up to A, stress is directly proportional to strain i.e Hook's law followed.
• Point B is the elastic limit.
• Point C is the upper yield point. At upper yield point, the resistance suddenly decreases. Therefore, stress is also decreased, this is the particular property of mild steel.
• Point D is the lower yield point which is the stable point for the design, the yield strength is considered to lower yield point
• Point F is the ultimate point. At point F necking starts and due to necking 45-degree micro cracks generates.
• Point G is the breaking point. At G component break into two pieces and failure is the cup-cone failure.The cup-cone failure is a shear failure.

• Stress-Strain diagram for Brittle material OA is non-linear elastic AB is the Strain Hardening.

• Brittle material never yields, a point similar to yield point is first cracking point, where simple cracks develop; which may expand further leading to failure.
• A point is the first cracking point. After first cracks develop, the material undergoes an increase in strain by widening the crack and fails almost at the same stress. Therefore for all calculation in brittle material design stress is ultimate or breaking stress i.e Sut.

Factor of Safety

Factor of safety (F.O.S) also known as Safety Factor (SF), is a term describing structural capacity of system beyond the expected load or actual load.

• Ductile:  • Brittle:  • Margin of Safety: M.O.S= F.O.S-1