k2 stress-system

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