Fracture Mechanics ppt
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Transcript of Fracture Mechanics ppt
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FRACTURE MECHANICSCRACK ??
FRACTURE ???
MECHANICS OF MATERIAL/STRENGTH OF MATERIAL ??
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ASSUMPTIONHOMOGEN
CONTINUE
ISOTROPI
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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
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Fracture mechanicsLINEAR ELASTIC FRACTURE MECHANICS (LEFM)* BEBAN ELASTIS == FATIGUE
ELASTIC PLASTIC FRACTURE MECHANICS* BEBAN PLASTIS
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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
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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.
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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
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Expected highest service loadCrack sizeCycles/timeResidual strengthCrack size, timeDesign strengthExpected highest service loadNormal sevice loadFailuremay occurefailure
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FRACTURE/PATAHAWAL RETAK/CRACK INITIATIONCRACK PROPAGATIONFINAL FRACTURE
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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
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MODE OF FRACTUREMixedModeI & III & III
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FRACTURE MECHANICS PARAMETERSyK = v. a f (a/w)K = stress insity factora = crack sizef(a/w) = shape factor
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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)
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da/dN KIIIIIICrack initiationPropagationFinal/static fractureStable crackUnstable Kc propertiesFracture toughness valueK Kth
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Crack propagation (da/dNPARIS LAW
da/dN = C ( K)m K = stress intensity rangeC , m = the material constant K = K max K min
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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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