Fracture Mechanics Assessment of highly loaded cast iron components for low temperature. Dr. Peter Langenberg

Transcription

1 Fracture Mechanics Assessment of highly loaded cast iron components for low temperature Dr. Peter Langenberg IWT (Ingenieurbüro für Werkstofftechnik) Aachen Cast Tec 2012 Krefeld, November2012 1,00E+00 1,00E-01 1,00E-02 GJS600 R=0,1 Pusch et al.2002 GJS600, R= 0,3, Pusch et al 2002 GJS600, R = 0,1, Hübner 2008 da/dn 1,00E-03 1,00E-04 Bemessungslinie 1,00E-05 K th = 6 1,00E-06 C = 2,22E-09 m = 4,1 1,00E K

2 Working areas Joint Industry projects (Steel, Welding, Safety, Standardisation) Component Safety and Component Testing Structural Integrity and Fracture Mechanics European Standardisation for pressure equipment (N 13445, EN13480) projects Contact: Dr. Peter Langenberg, Tel: +49 (0) Visit also: 2

3 Overview 1. Why using cast iron 2. When using fracture mechanics 3. Fracture Mechanics Methods 4. Application for cast iron (GJS700) 5. Conclusions

4 Why using cast iron? 1. Wide spectrum of strength GJS 350 bis GJS Good ductility up to GJS 400, A 12 % 3. Possibility for low temperature service with Toughness T = -40 C GJS 350 LT and T = -20 C EN GJS 400 LT (KV min = J) 4. Weldable economic flexible safe.?

5 Overview 1. Why using cast iron 2. When using fracture mechanics 3. Fracture Mechanics Methods 4. Application for cast iron (GJS700) 5. Conclusions

6 When using fracture mechanics 1. Elongation is smaller than 12 % ( ab GJS 450). 2. No toughness requirements (except LT-Grades). 3. Load Deformation Behaviour with low plastic deformation capacity. 4. Quality level of NDT according toen , EN 1369, EN Fatigue Loading (High Cycle). 6. Low Temperature application (down to -40 C).

7 Former applications of Fracture Mechanics 1. z.b. Motz et al., Publication during the 80ties 2. Pusch, Baer und andet al.ere (TU Freiberg, BAM Berlin) in relation to Nuclear Waste Container (CASTOR) 3. MEGAWIND (AIF Projekt) 4. VDMA Technical Commitee Planet Carrier (Gear Producers)

8 Overview 1. Why using cast iron 2. When using fracture mechanics 3. Fracture Mechanics Methods 4. Application for cast iron (GJS700) 5. Conclusions

9 Fracture Mechanics Methods r pl EDZ ESZ Rißspitze r pl 1. Linear Elastic Fractur Mechanics LEFM Stress Intensity Factor K Ic 2. Elastic Plastic Fracture Mechanics EPFM J-Integral (J IC ) CTOD (CTOD I ) K I = σ π a y( w, t)

10 Fracture Mechanics based Limit State Design S A F E AIM: Avoidance of Brittle Fracture METHOD: Fracture Mechanics Limit State: Initiation of an unstable Crack Loading S <(=)> Resistance R Crack driving Force <(=)> Crack Resistance U N S A F E K, J, CTOD (Component) <(=)> K, J, CTOD (Material) copyright

11 Procedure 1. Component Analysis Componentgeometry and Imperfectiongeometry, external load, lowest service temperatrur 2. Fracture Mechanics Model 3. Calculation of Crack Driving Force 4. Determination of Fracture Resistance (fracture toughness) 5. Limit State Calculation (Crack Driving Force = Fracture Resistance) Result: 1. Toughness Requirements or 2. Critical crack geometry or 3. Critical Load KI N/mm3/ Grenzzustand K in N/mm^3/2 K in MPam^1/2 0 0 σ crit K1c 600= 1000 Spannung, MPa K1c = 2000 K1c = 3000

12 Overview 1. Why using cast iron 2. When using fracture mechanics 3. Fracture Mechanics Methods 4. Application for cast iron (GJS700) 5. Conclusions

13 Transfer to Cast Iron I 1. Component Analysis and Imperfection Geometry a. Volumetric Imp. (EN ) b. Surface Imp. (EN 1369, EN 1371) c. Strength critical areas Spannung, MPa Spannungsverlauf an der Oberfläche Modell 1, Spot 1 und S1 SEQV Entfernung von Hot Spot, mm

14 Transfer to Cast Iron I 2. Material properties a. K IC (LEBM) or J IC (EPBM) b. Paris Constants C, m, K threshold c. But, testing expensive, d. Leading to the question of using Correlations, Master Curve, Damage Mechanics (see contribution Dr. Muenstermann) 1,00E+00 1,00E-01 1,00E-02 GJS600 R=0,1 Pusch et al.2002 GJS600, R= 0,3, Pusch et al 2002 GJS600, R = 0,1, Hübner 2008 da/dn 1,00E-03 1,00E-04 Bemessungslinie 1,00E-05 1,00E-06 K th = 6 C = 2,22E-09 m = 4,1 1,00E K

15 Transfer to Cast Iron I 3. Crack Driving Force a. K I (LEBM) or J I (EPBM) b. Finit Element Analysis or analytical c. Software EPFM KI N/mm3/ LEFM Grenzzustand K in N/mm^3/2 K in MPam^1/2 0 0 σ crit K1c 600= 1000 Spannung, MPa K1c = 2000 K1c = 3000 K R K R = K I K mat Grenzkurve Option 2 FAD Versagenspfade L R = σ Brutto σ Fließ L R

16 Application GJS 700 (Planet Carrier) 1. Component Analysis Component and Failure Geometry, exteral laods and crack geometry 2. Fracture Mechanic Model 3. Crack Driving Force Calculation 4. Drivation of Fracture Toughness 5. Limit Load Calculation FEM Analyse 300 Spannungsverlauf über Dicke unter Hot Spot Modell 2, Spot 5 Modell: Shaft with embed elliptical imperfection Source: IWM Verb Spannung, MPa S1 SEQV Design Crack size after EN lunkerartiger Fehler porenartiger Fehler Entfernung von Hot Spot, mm Modell Spot Rand/Kern 2c 0 *1 2a 0 2c 0 *2 2a 0 R / K mm mm mm mm 1 4 R 13,8 2,8 7,0 6,3 K 53,6 10,7 7,0 6,3 2 5 R 13,8 2,8 7,0 6,3 K 53,6 10,7 7,0 6,3 3 6 RK 10,7 2,1 4,0 3,6 4 7 RK 10,7 2,1 4,0 3,6 *1 : a/c = 0,2 *2 : a/c = 0,9

17 Application GJS 700 (Planet Carrier) 1. Component Analysis Component and Failure Geometry, exteral laods and crack geometry 2. Fracture Mechanic Model 3. Crack Driving Force Calculation 4. Drivation of Fracture Toughness 5. Limit Load Calculation FADAnalyse K R K R = K I K mat Grenzkurve Option 2 Fracture Toughness Test at T =-20 C Statistical derivation Weibulldistribution Versagenspfade L R = σ Brutto σ Fließ L R lunkerartiger Fehler Modell Rand/Kern 2a 0 2a crit 2c 0 2c crit S a R oder K mm mm mm mm 1 R 2,8 15,1 13,8 75,7 5,5 K 10,7 60,0 53,6 300,0 5,6 Result 2 R 2,8 8,9 13,8 44,3 3,2 K 10,7 30,4 53,6 152,0 2,8 3 RK 2,1 14,1 10,7 70,7 6,6 4 RK 2,1 11,0 10,7 55,0 5,1 Tabelle 10: Ergebnisse der bruchmechanischen Sicherheitsberechnung für lunkerartige Fehler, Berechnung mit Bemessungswerten für Werkstoffparameter und extremaler Last.

18 Application GJS 700 (Planet Carrier) 1. Component Analysis Component and Failure Geometry, exteral laods and crack geometry 2. Fracture Mechanic Model 3. Crack Driving Force Calculation 4. Drivation of Fracture Toughness 5. Limit Load Calculation Spannungsamplitude σ, MPa 140,0 120,0 100,0 80,0 60,0 40,0 20,0 0,0 Spannungskollektiv, Knoten 51817, Spot 4, Modell 1, Load Cycle Distirbution berechnet von Jahnel-Kestermann 1,0E+00 1,0E+02 1,0E+04 1,0E+06 1,0E+08 1,0E+10 n_i n_i acc. da/dn 1,00E+00 1,00E-01 1,00E-02 1,00E-03 1,00E-04 1,00E-05 1,00E-06 1,00E-07 Paris Law GJS600 R=0,1 Pusch et al.2002 GJS600, R= 0,3, Pusch et al 2002 GJS600, R = 0,1, Hübner 2008 Bemessungslinie K th = 6 C = 2,22E-09 m = 4, K Lastspiele N Result 1. K < K threshold, Componetn safe 2. K > K threshold, Inspection intervall necessary

19 Overview 1. Why using cast iron 2. When using fracture mechanics 3. Fracture Mechanics Methods 4. Application for cast iron (GJS700) 5. Conclusions

20 Conclusions 1. GJS (EN1563), a flexible and economic material 2. Toughness oriented Limit State Design available (Fracture Mechanics, especially for low temperature and high strength) 3. But: Toughness and Fatigue properties aer missing and derivation is expensive 4. And: Applciation fo fracture mechanics not commonly used (specialised experts) 5. Solution 1: Specific formulation of Boundary Conditions for FM Analysis (Example: Planet Carrier Guideline worked out by AK Planetenträger, VDMA), 6. Solution 2: Derivation of Material Properties from Master Curve or Correlationen 7. Solution 3: Joint Industry Project

21 Thank you for your attention Questions?? Do not hesitate to contact me. IWTprojects Ltd und IWT Aachen (Ingenieurbuero) Mail: Web: Web: Phone: +49 (0)