Mechanicial Properties of Materials Lecture # 5 and 6 Mechanicial Properties of Materials Objectives: 1): Relating Stress to Strain using experimental method. 2): Plotting Stress verses Strain (Stress – Strain diagram) 3): Extracting mechanical properties from – diagram.

The Tension and Compression Test Typical steel specimen with attached strain gauge. Electrical-resistance Strain gauge.

The Stress – Strain Diagram Conventional and true stress-strain diagrams for ductile material (steel) (not to scale).

True Stress – Strain Diagram Stress-Strain diagram for mild steel

Stress – Strain Behavior of Ductile and Brittle Materials Percent elongation = Percent reduction of area =

Hooke’s Law  (mm/mm)

Typical Stress-Strain curve showing modulus of resilience, MR. Typical Stress-Strain diagram showing modulus of toughness, MT.

Poission’s ratio. Lateral contraction for a bar in tension with Cross-sectional dimensions.

Deflection Due to Axial Loading Undeformed bar and Bar subject to axial force showing deformation. (in.) or (mm.)

Deflection Due to Axial Loading Bar with intermediate axial loads. Bar with changes in cross section and intermediate loads. (in.) or (mm.)

Deflection Due to Axial Loading Bar with variable cross sectional area and Bar subjected to loading that varies with x. (in.) or (mm.)

Elastic Strain verses Plastic Strain Strain Hardening

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