Susmel Multiaxial Notch Fatigue

1. Auflage 2009
ISBN: 978-1-84569-583-5
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 588 Seiten

Reihe: Woodhead Publishing Series in Metals and Surface Engineering

Metal and composite components used in structural engineering not only contain geometrical features resulting in stress concentration phenomena, but they are also subjected to in-service multiaxial fatigue loading. To address the problem, structural engineers need reliable methodologies which allow for an adequate margin of safety. The book summarises methods devised by the author to design real components against multiaxial fatigue by taking full advantage not only of nominal but also of local stress-strain quantities.The book begins by reviewing definitions suitable for calculating the stress-strain quantities commonly used to perform fatigue assessment. The Modified W”hler Curve Method is then explained in detail, by focusing attention on both the high- and the medium-cycle fatigue regime. The existing links between the multiaxial fatigue criterion and physical properties are also discussed. A procedure suitable for employing the method developed by the author to estimate fatigue damage both in notched and in welded components is explained. The Modified Manson-Coffin Curve method is investigated in depth, by reviewing those concepts playing a fundamental role in the so-called strain based approach. Lastly, the problem of performing the fatigue assessment of composite materials is addressed by considering design parameters influencing composite behaviour under complex cyclic loading paths and those criteria suitable for designing real components against multiaxial fatigue. The book also contains two appendices summarising experimental data from the technical literature. These appendices provide a unique and highly valuable resource for engineers. The appendices summarise around 100 values of the material characteristic length L, experimentally determined by testing specimens made of different engineering materials and about 4500 experimental fatigue results generated by testing plain, notched and welded specimens under constant-amplitude proportional and non-proportional multiaxial fatigue loading are listed. - Summarises methods devised by the author to design real components against multiaxial fatigue - Reviews definitions suitable for calculating the stress-strain quantities commonly used to perform fatigue assessment - Includes an in-depth explanation of both the Modified W”hler Curve and Modified Manson-Coffin Curve Method

Luca Susmel is an Associate Professor in Structural Integrity at the University of Ferrara, Italy.

Autoren/Hrsg.

Susmel, Luca

Leseproben

Nomenclature
a Unit vector defining the orientation of axis a a Notch depth a* Notch depth defining the blunt notch regime in Atzori and Lazzarin’s diagram a, b, a, ß Constants in the governing equations of the MWCM a0 El Haddad’s short crack constant an, bn, an, ßn Constants of the MWCM calculated in terms of nominal net stresses ax, ay, az Components of unit vector a aH, CH Constants in Heywood’s formula aN Constant in Neuber’s formula ap Constant in peterson’s formula 2a Crack length b Unit vector defining the orientation of axis b b Fatigue strength exponent b0 Fatigue strength exponent under shear strain bx, by, bz Components of unit vector b c Fatigue ductility exponent c0 Fatigue ductility exponent under shear strain d Hole diameter K Negative inverse slope kI, kII Non-dimensional quantities depending on the welded joint geometry kt Negative inverse slope of the modified Wöhler curve l Actual length l0 Gauge length m Mean stress sensitivity index n Number of cycles n Strain hardening exponent n' Cyclic strain hardening exponent n Unit vector normal to plane ? nx, ny, nz Components of unit vector n Oxyz Frame of reference Oabn Frame of reference relative to plane ? Or?? Polar coordinates q Notch sensitivity factor q Unit vector defining the orientation of direction q qx, qy, qz components of unit vector q rn Notch root radius t Time t, L Welded plate thickness t Total stress vector tx, ty, tz components of vector t z Weld bead height A Constant in Kuhn and Hardraht’s formula A0 initial value of the cross-sectional area A, B Constants in the LM vs. Nf relationship C, m Constants in Paris’ law D Notch depth E Young’s modulus E (%) Error F LEFM geometrical factor Fa Amplitude of the axial force F (t) Axial force I1s, I2s, I3s First, second and third stress invariant K Strength coefficient K' Cyclic strength coefficient K1, K2, K3 Notch stress intensity factors due to Mode i, ii and iii loading Kf Fatigue strength reduction factor Kft Fatigue strength reduction factor under torsional loading Kf, e Estimated fatigue strength reduction factor Ki (Nf) Calibration functions for assessing composite materials (i = 1, 2,…, 6) Kt Stress concentration factor Ktt Stress concentration factor under torsional loading Kt, gross Stress concentration factor referred to the gross area K*t, gross Kt value defining the transition from the blunt to the sharp notch regime Kt, net Stress concentration factor referred to the net area KC Fracture toughness K1C Plane strain fracture toughness KI, KII, KIII Stress intensity factors due to Mode i, ii and iii loading KI, max Maximum value of the stress intensity factors due to Mode I loading L Material characteristic length LM Material characteristic length in the medium-cycle fatigue regime LT Material characteristic length under Mode III loading Mt Torque M-DV Multiaxial critical distance value N0 Number of cycles to failure defining the position of the knee point Nt Number of cycles to failure Nf, e Estimated number of cycles to failure NA Reference number of cycles to failure ND Reference number of cycles to failure NS Reference number of cycles to failure in the low cycle fatigue regime PS Probability of survival R Load ratio (R = s,min/s i, max where i = x, y, z) RCP Load ratio relative to the critical plane Re strain ratio T Period of the cyclic load history Ts Scatter ratio of reference shear stress amplitude for 90% and 10% probabilities of survival UF, a Amplitude of the strain energy density UF, A Reference amplitude of the strain energy density extrapolated at NA cycles to failure 2a Opening angle ? a Maximum shear strain...