GS-02 [Compatibility Mode]

STRESS (Tegasan) & STRAIN ( Keterakan)Strain didefinisikan sebagai jumlah

perubahan atau deformasi suatu obyek p y(batuan) dibandingkan dengan bentuk dan ukuran asli obyek tersebut.y

STRESS ( TEGASAN )( )

Compression Stress that acts to shorten an object. Tension Stress that acts to lengthen an object. Normal Stress Stress that acts perpendicular to a surface.

Can be either compressional or tensional. Shear Stress that acts parallel to a surface It can causeShear Stress that acts parallel to a surface. It can cause

one object to slide over another.

STRAINSTRAINSimple shearSimple shear

Perhaps the most familiar illustration of shear is the movement of rocks on opposite sides of a fault as shown here Because this type of shear is the easiest to visualize it ishere. Because this type of shear is the easiest to visualize, it is called simple shear.

Imagine when the fault starts moving we draw a line at right angles to the fault. As the fault slips, the line rotates (and also lengthens) and angle A increases However angle A will neverlengthens), and angle A increases. However, angle A will never reach 90 degrees unless the slip on the fault is infinite.

STRAINSTRAINSimple shearSimple shear

We can define shear strain exactly the way we do longitudinal strain: the ratio of deformation to original dimensions. In the case of shear strain, though, it's the amount of deformation perpendicular to a given line rather than parallel to it. The ratio turns out to be tan A, where A is the angle the sheared line makes

ith it i i l i t ti N t th t if A l 90 d th h t i iwith its original orientation. Note that if A equals 90 degrees, the shear strain is infinte.

STRAINSTRAINPure shearPure shear

Simple shear vs Pure shearSimple shear vs Pure shear

Simple Shear:Simple Shear:One direction remains constant and everything else rotates relative to it. Approximates the situation in a shear zone.

Pure ShearDirections of greatest compression and extension are constant. The major and minor axes of the deforming ellipse remain constant. All other lines rotate.

STRESS ( TEGASAN )STRESS ( TEGASAN )

Definisi : Secara konvensional, tegasan () adalah gaya (F) , g ( ) g y ( )yang berarah orthogonal per satuan luas (A)

/ = F/A


Simbol / Notasi :

(sigma) Satuan :

Newton/m2 Pascal (Pa)Newton/m2 , Pascal (Pa),

Atmosphere (Atm), Psi, dan lain-lainp ( )

STRESS ( TEGASAN )STRESS ( TEGASAN )T tiTraction

Apa yang kita sebut sebagai stress, pa ya g ta sebut sebaga st ess,sebetulnya lebih tepat disebut sebagai tractiono

Sedangkan Stress yang sebenarnya g y g yadalah sejumlah traction dari berbagai arah secara kolektif yang bekerja pada y g j psuatu titik pada suatu bidang


F = gaya

F = Gaya normalFn = Gaya normal

= F cos Fs = Gaya geser (shear)

= F sin


Gaya normal adalah gaya yang memiliki arah orthogonal atau tegaklurusarah orthogonal atau tegaklurus terhadap permukaan suatu bidang

Gaya geser (shear) adalah suatu gaya yang memiliki arah sejajar dengan permukaan suatu bidang


= Stress atau tegasan/ l= F / luas

Normal stress =

Shear stress =


Lithostatic stress

= F/A


Stress TensorKita ambil suatu bagianKita ambil suatu bagian dari kubus granit suatu titik (P) berbentuk kubus pada d k bdasar kubus.


Stress Tensor Suatu bidang berorientasi =500 thd sumbu Z, akan memiliki luas = nm2

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Stress Tensor


Stress Tensor


Stress Tensor

Jadi xz adalah stress vector atau traction yang dihasilkan oleh stress vertikal 40 Mpa dan stressvertikal 40 Mpa dan stress horisontal 20 Mpa pada bidang yang beorientasi 500 thd sb Z,

iliki b 32 23M dmemiliki besaran 32,23Mpa dan berorientasi 22,760 thd sb - z


Stress Tensor


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GS-02 [Compatibility Mode]

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