FRACTURE MECHANICSCRACK ??

FRACTURE ???

MECHANICS OF MATERIAL/STRENGTH OF MATERIAL ??

ASSUMPTIONHOMOGEN

CONTINUE

ISOTROPI

CASES

1800 1870 : Accidents were caused by Fractures of wheel, axle, rails (Great Britain).19th March 1830 : Montrose Suspension Bridge.Main chain gave way 700 persons killed.22nd January 1866 : A portion of roof of the Manchester railway station fell. 2 men death.Caused by failure of cast iron struts connected.13th December 1898 : The failure of a large gas tank in New York.3th January 1913 : A high pressure water burst at Boston flooded the districtFebruary 1866 : Boiler explosionsMost of serious railway accidents

Spec pipa : API. 5 LX grade X52, electric resistance welded, longitudinal weld pipa- Mechanical properties : u, y- Dimensi pipa : 16 , t = 0,250 Kondisi operasi : p = 600 psig (avg) Sistem perlindungan- Kondisi lingkungan

POOR DESIGN

Fracture mechanicsLINEAR ELASTIC FRACTURE MECHANICS (LEFM)* BEBAN ELASTIS == FATIGUE

ELASTIC PLASTIC FRACTURE MECHANICS* BEBAN PLASTIS

STRESS CONCENTRATION FACTOR (Kt)RADIUS OF FILLETr/Dr/D>Notch stress (notch)>>>notch = Kt x unnotch/ nBagaimana kalau r ~ 0, D = constantr/D = 0/D ~ infinite = crack/retakCrack # notch/holeKt = faktor pengendali konstruksi yang ada notch

SOURCES OF STRESS CONCENTRATEDIMPURITY,VACANCY,DISLOCATION,GRAIN BOUNDARYROUGHNESS OF SURFACEWELD DEFECTHOLE FOR RIVET, BOLT

DONT CONSIDER TO AVOID FRACTURE, BUT CONSIDER TO CONTROL FRACTURE IN DESIGN, MANUFACTURING, MAINTENANCE AND REPAIR.

What is CRACK????Notch yang r ~ 0 Alat kontrolnya bukan lagi Kt K1 , K2 atau K3 (factor intensitas tegangan/ stress intensity factor)KI = MODUS I , tensionKII = modus II, slidingKIII = modus III, tearing

Expected highest service loadCrack sizeCycles/timeResidual strengthCrack size, timeDesign strengthExpected highest service loadNormal sevice loadFailuremay occurefailure

FRACTURE/PATAHAWAL RETAK/CRACK INITIATIONCRACK PROPAGATIONFINAL FRACTURE

TOTAL24277%FATIGUESIMPLE FATIGUE

58%CORROSIO FATIGUEROLLING CONTACTFATIGUE

11 %ThermalFatigue 8 %Others23 %

SCC 5% corrosion burst 3%Static fracture 13%24290 %Stress concentrationWelded part

77Key, atc

56Bolt 32Pulley,roll

28Gear 18Cast 15Wire rope 8Others 10

MODE OF FRACTUREMixedModeI & III & III

FRACTURE MECHANICS PARAMETERSyK = v. a f (a/w)K = stress insity factora = crack sizef(a/w) = shape factor

Fracture toghness Kc is fracture toughness value/ nilai ketangguhan retak K ~ Kc === patah/fracture K < Kc == crack propagation/menuju patah a ~ ac (critical size) patah K = K max K min K max = max V . a f (a/w) K min = min V . a f (a/w)

da/dN KIIIIIICrack initiationPropagationFinal/static fractureStable crackUnstable Kc propertiesFracture toughness valueK Kth

Crack propagation (da/dNPARIS LAW

da/dN = C ( K)m K = stress intensity rangeC , m = the material constant K = K max K min

CRACK PROPAGATION

N(cycles)ada/dN (log scale)K (log scale)da/dN = C (K)mP1>P2>P3P1P2P3PPtb at(time)PP maxP mindadNK = (a)^1/2 f(a)+-R = -1

R=0

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