1. MEKANIKA MATERIAL (BAHAN)
Jenis pembebanan pada material
Jenis tegangan (stress)
Perhitungan kekuatan material untuk menentukan dimensi dan pemilihan bahan berdasarkan jenis pembebanan yang terjadi

4. Terminology for Mechanical Properties
Stress - Force or load per unit area of cross-section over which the force or load is acting.
Strain - Elongation change in dimension per unit length.
Young’s modulus - The slope of the linear part of the stress-strain curve in the elastic region, same as modulus of elasticity.
Shear modulus (G) - The slope of the linear part of the shear stress-shear strain curve.

5. Engineering Stress Stress has units: N/m2 (or lb/in2 )
Tegangan Normal (): intensitas gaya yang bekerja tegak lurus bidang irisan
contoh: Tensile stress, ()
Tegangan geser (): intensitas gaya yang bekerja sejajar bidang irisan
Contoh : Shear stress, ():
Stress has units: N/m2 (or lb/in2 )

6. Modes of loading and states of stress

9. Modes of loading and states of stress

10. Modes of loading and states of stress

15. PEMBEBANAN PADA BEJANA TEKAN

16. PEMBEBANAN PADA BEJANA TEKAN

17. Tegangan Hoop pada bejana tekan

18. Gaya Hoop pada bejana tekan
Berdasarkan gambar d akan diuraikan gaya-gaya yg berlaku

26. Pure Tension Pure Compression stress strain Elastic response
Pure Shear
stress
strain
Elastic
response
Pure Torsional Shear 26

27. Mekanika bahan konsep stress

28. Hooke’s law for extension:
σ = E 
Hooke’s law for shear:
 = G 

29. 1 Pa = ×10−6 psi

30. Hooke’s law for extension:
σ = E 
Hooke’s law for shear:
 = G 

34. Common States of Stress
• Simple tension: cable
Ski lift (photo courtesy P.M. Anderson)
• Simple shear: drive shaft
Note: t = M/AcR here. 34

35. (c)2003 Brooks/Cole, a division of Thomson Learning, Inc
(c)2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
gauge
length
Figure. A unidirectional force is applied to a specimen in the tensile test by means of the moveable crosshead. The cross-head movement can be performed using screws or a hydraulic mechanism

36. Properties Obtained from the Tensile Test
Elastic limit
Tensile strength, Necking
Hooke’s law
Poisson’s ratio
Modulus of resilience (Er)
Tensile toughness
Ductility

37. Test Specimen Standard

38. Figure. The stress-strain curve for an aluminum alloy
(c)2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
Figure. The stress-strain curve for an aluminum alloy

39. (c)2003 Brooks/Cole, a division of Thomson Learning, Inc
(c)2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
Figure. (a) Determining the 0.2% offset yield strength in gray cast ion, and (b) upper and lower yield point behavior in a low-carbon steel

40. cup-and-cone fracture in Al
Figure. Localized deformation of a ductile material during a tensile test produces a necked region
brittle fracture in mild steel 40

41. (Ultimate) Tensile Strength, σTS
• Maximum possible engineering stress in tension. y
strain
Typical response of a metal
F = fracture or
ultimate
strength
Neck – acts as stress concentrator
engineering TS
stress
engineering strain
• Metals: occurs when necking starts.
• Ceramics: occurs when crack propagation starts.
• Polymers: occurs when polymer backbones are
aligned and about to break. 41

42. Deformation Process During Test

46. cup-and-cone fracture in Al
(c)2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
cup-and-cone fracture in Al
Figure. Localized deformation of a ductile material during a tensile test produces a necked region
brittle fracture in mild steel 46

47. EULER CRITERIA

53. Modes of loading and states of stress

54. PROBLEM

56. PROBLEM

57. PROBLEM
Rod AB
Rod BC

60. PROBLEM

61. PROBLEM