2. Physics Study Program Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung FI-1101 Fisika Dasar IA Kuliah 18 ELASTISITAS

3. Physics Study Program - FMIPA | Institut Teknologi Bandung PHYSI S Materi Hari Ini Tegangan (stress) Regangan (strain) Modulus Elastisitas

4. Physics Study Program - FMIPA | Institut Teknologi Bandung PHYSI S Elastisitas Adalah cabang dari Fisika yang menjelaskan tentang bagaimana suatu benda berubah bentuk ketika diberikan suatu gaya Real rigid bodies are elastic  we can slightly change their dimensions by pulling, pushing, twisting or compressing them. Stress: Deforming force per unit area Strain: Unit deformation Tensile stress: associated with stretching Shearing stress Hydraulic stress Stress = Elasticity Modulus x Strain Elastic modulus: describes the elastic behavior (deformations) of objects as they respond to forces that act on them

5. Physics Study Program - FMIPA | Institut Teknologi Bandung PHYSI S (1) Stress = cte x Strain  Recovers original dimensions when stress removed. (2) Stress > yield strength S y  specimen becomes permanently deformed. (3) Stress > ultimate strength S u  specimen breaks. Tension and compression: ( F= force applied perpendicular to the area A of the object) ( fractional change in length of the specimen) Stress = (Young ’ s modulus) x Strain Shearing: ( F= force in the plane of the area A) ( fractional change in length of the specimen) Units of Young modulus: F/m 2 Stress = (Shear modulus) x Strain Hydraulic stress: Hydraulic Stress = (Bulk modulus) x Hydraulic compression

6. Physics Study Program - FMIPA | Institut Teknologi Bandung PHYSI S Young ’ s Modulus Everything is a spring … … until it breaks!

7. Physics Study Program - FMIPA | Institut Teknologi Bandung PHYSI S Shear Modulus Shear moduli and Young moduli are comparable in magnitude for most materials (Liquids have zero shear modulus)

8. Physics Study Program - FMIPA | Institut Teknologi Bandung PHYSI S Pressure and Bulk Modulus Pressure is defined as force per unit area Unit of pressure is N/m 2 = Pascal (Pa) Atmospheric pressure ~ 10 5 Pa= 15psi 1 psi = 1 pound per square inch Bulk modulus B relates fractional volume change to pressure change

9. Physics Study Program - FMIPA | Institut Teknologi Bandung PHYSI S Stress, Strain and Hooke ’ s law F/A or pressure are known as “ stress ” Fractional changes in length or volume are known as “ strain ” Above relations between stress and strain account for “ elastic ” behavior and Hooke ’ s law

10. Physics Study Program - FMIPA | Institut Teknologi Bandung PHYSI S End of Section...