SISTIM TEGANGAN &
RESIDUAL STRESS
DEPARTEMEN METALURGI MATERIALS
FAKULTAS TEKNIK UNIVERSITAS INDONESIA
Dr. Ir. Winarto, M.Sc.
Jenis Tegangan yang Umum
Secara umum jenis tegangan dibagi menjadi 3 bagian :
1. Tegangan tarik / tekan (tension / compression stress)
2. Tegangan geser (shear stress)
3. Tegangan puntir (torsion stress)
Static Dynamic
Tension Torsion - Compression
Shear vs. Cleavage
SEM Image of Ductile Fracture
Cleavage facets
Ductile vs. Brittle
Tension stress
Schematics of typical tensile test fractures
Tension
Compression
Hasil Uji Kuat Tekan Pasta
Geopolimer
Hasil Uji Kuat Tekan Beton
Geopolimer
Buckling of Cold-Formed Steel Columns
Shear Stress Failure
Torsion
Torsion
TORSION FAILURE
Ductile Fracture
Brittle Fracture
Torsion Fracture
Perpatahan Pada Komponen Mesin
Drive Pinion
Axle Shaft
Stress Strain Diagram
Diagram - for Steels
Diagram - for Cast Iron
Modulus vs. Temperature
Effect Surface on Fatigue
Stress Concentration on Plate
(tension)
Stress Concentration on Rods
(torsion)
Stress Concentration on Plate
(compression)
Stress Concentration on Plate
(bending)
Stress Concentration on Hollow Rod
Wear on Rollers
Shear on plates
Stress on Boiler
Fatigue on Rods
Fatigue on Plates
Initial Fracture vs Stress
Initial Fracture vs Stress
RESIDUAL STRESS
Residual stress adalah stress yang tinggal di dalam struktur
sebagai hasil dari perlakuan mekanis atau thermal atau
keduanya.
Residual stress dapat menyebabkan 2 efek utama yaitu :
- Distorsi pada komponen
- Menyebabkan kerusakan premature pada komponen
Distorsi akibat panas timbul daerah yang terkontraksi tidak
seragam menyebabkan shrinkage (susut) di bagian tertentu.
Residual Stress
The Cause of Residual Stress
Fig. Effect of surface residual stress on the endurance limit of selected steel. All samples were water quenched except as shown, and all
specimen dimensions are given in inches. Source: Ref 23, 24
Compression at the surface
Surface working: shot peening, surface rolling,
lapping, and so on
Rod or wire drawing with shallow penetration(a)
Rolling with shallow penetration(a)
Swaging with shallow penetration(a)
Tube sinking of the inner surface
Coining around holes
Plastic bending of the stretched side
Grinding under gentle conditions
Hammer peening
Quenching without phase transformation
Direct-hardening steel (not through-hardened)
Case-hardening steel
Induction and flame hardening
Prestressing
Ion exchange
Tension at the surface
Rod or wire drawing with deep penetration
Rolling with deep penetration
Swaging with deep penetration
Tube sinking of the outer surface
Plastic bending of the shortened side
Grinding: normal practice and abusive
conditions
Direct-hardening steel (through-hardened)(b)
Decarburization of steel surface
Weldment (last portion to reach room
temperature)
Machining: turning, milling
Built-up surface of shaft
Electrical discharge machining
Flame cutting
Table. Summary of compressive and tensile residual stresses at the surface of
the parts created by the common manufacturing processes (Source: Ref 22 )
(a)Shallow penetration refers to 1% reduction in area or thickness; deep penetration refers to 1%.
(b)Depends on the efficiency of quenching medium.
Thermal Effect
Metal Modulus of elasticity
Coefficient of
expansion Thermal conductivity
GPa psi 106 10-6/K 10-6/F W m-1 k-1 Btu in./ft2 h F
Pure iron (ferrite) 206 30 12 7 80 555
Austenitic steel 200 29 18 10 15 100
Aluminum 71 10 23 13 201 1400
Copper 117 17 17 9 385 2670
Titanium 125 18 9 5 23 160
Table 5 Relevant physical properties in the development of thermal stresses (Ref 29).
Steel Heat treatment
Residual stress
(longitudinal)
MPa ksi
832M13
(type)
Carburized at 970 C (1780 F) to 1 mm (0.04 in.) case with 0.8% surface C
Direct-quenched 280 40.5
Direct-quenched, -80 C (-110 F) subzero treatment 340 49.0
Direct-quenched, -90 C (-130 F) subzero treatment, tempered 200 29.0
805A20 Carburized and quenched 240-340(a) 35.0-49.0
805A20 Carburized to 1.1-1.5 mm (0.043-0.06 in.) case at 920 C (1690 F), direct oil quench, no temper
190-230 27.5-33.5
805A17 400 58
805A17 Carburized to 1.1-1.5 mm (0.043-0.06 in.) case at 920 C (1690 F), direct oil quench, tempered 150 C (300 F)
150-200 22-29
897M39 Nitrided to case depth of about 0.5 mm (0.02 in.) 400-600 58.0-87.0
905M39 800-1000 116.0-145.0
Cold-rolled
steel
Induction hardened, untempered 1000 145.0
Induction hardened, tempered 200 C (390 F) 650 94.0
Induction hardened, tempered 300 C (570 F) 350 51
Induction hardened, tempered 400 C (750 F) 170 24.5
(a) Immediately subsurface, that is, 0.05 mm (0.002 in.).
Source: Ref 29
Table 6 A compiled summary of the maximum residual stresses in surface heat-treated steels
Fig. 10 (a) The transverse shrinkage occurring in butt weldments.
(b) Longitudinal residual stress patterns in the weldment and
surrounding regions. This also shows longitudinal shrinkage in a
butt weld. Source: Ref 47
Shoot Peenning
Schematic of Residual Stress
Home Work1. Jelaskan jenis-jenis Tegangan yang terjadi pada
material
2. Jelaskan dengan gambar distribusi tegangan pada pelat
(plates) dan batangan (rods) akibat tegangan tarik bila
stress konsentrasinya (a) tidak ada, (b) dipermukaan,
(c) di bagian tengah
3. Gambarkan terjadinya residual stress dan efek-nya
pada material.
4. Jelaskan penyebab dari tegangan sisa (residual stress)
5. Jelaskan mengapa shoot peening dan penghalusan
permukaan menyebabkan kekuatan fatiknya menjadi
tinggi sedangkan chrom-plating menyebabkan kekuatan
fatik turun. Uraikan dengan gambar skematis
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