Key ConceptsStress (TEGASAN)measure of internal loadsukuran untuk beban dalamanStrain (TERIKAN) measure of deformationukuran untuk perubahan bentukStress*

Stress

AXIAL MEMBERS:Average Normal Stress ( Direct Normal Stress):*Requirements for Average Normal Stress, s = P/A:Member starts out straight and remains straight after loadingHomogenous, isotropic

Stress*MEMBER(ANGGOTA)Apabila suatu anggota dikenakan beban luaran (P), beban ini akan dipindahkan ke dalam anggota tersebut.FA dan FB

Stress

Definition of StressStress* (sigma) = P/A

Stress

Units of StressStress*

Stress

Units of StressStress*

Stress

Units of StressStress*

Stress

Units of StressStress*Civil engineers often use pounds per square foot as a unit of stress (pressure). 1 psi = 144 psf

Stress

Sheet1

1 psi = 6.895 kPA

1 ksi = 6.895 MPa1 kPa = 0.1450 psi

1000000 psi = 1 Gpa1 MPa = 145.0 psi

1000 ksi = 6.895 Gpa

1 psf = 47.88 Pa1 Pa = 0.02089 psf

Sheet2

Sheet3

Example Normal Stress:If P = 20 kNand A = 20 mm2s = ?

*

EXAMPLE10 kN10 kN10 mm x 10 mm x 1000 mm10 kNPINTERNAL

EXAMPLESTRESS () = P/A = 10 kN/100 mm2 = 0.1 kN/mm2 = ______ Pa ?

QUESTION10 kNArea = 10 mm x 10 mm = 100 mm2FIND THE STRESSES IN SECTION AB, BC AND CD IF THE CROSS SECTIONAL AREA OF THE MEMBER IS UNIFORM = 35 mm22

Normal Strain = /LLPP

Strain

STRAIN

STRAIN = ELONGATION/ORIGINAL LENGTH (epsilon) = (delta)/L

= length/length = UNITLESS

StrainIF original length (L) is 100 mm and elongation is 5 mmTHEN STRAIN = 5 mm/ 100mm = 0.05

Strain

RELATIONSHIP BETWEEN STRESS AND STRAIN

Stress-Strain Test

Stress-Strain Diagram: Ductile Materials

Stress-Strain Diagram: Ductile Materials

Stress-Strain Diagram: Ductile MaterialsSlope = sigma/epsilonSlope = Young Modulus (E)

YOUNG MODULUSSTRAINSTRESSYOUNG MODULUS =SLOPE = STRESS/STRAINE = /

Stress-Strain Diagram: Brittle Materials

Hookes Law: Modulus of ElasticityStrength is affected by alloying, heat treating, and manufacturing process but stiffness (Modulus of Elasticity) is not.

Elastic vs. Plastic BehaviorIf the strain disappears when the stress is removed, the material is said to behave elastically. When the strain does not return to zero after the stress is removed, the material is said to behave plastically.The largest stress for which this occurs is called the elastic limit.

Deformations Under Axial Loading

*Figure: 01-15

*Figure: 01-27a