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

Notch depth

* Notch depth defining the blunt notch regime in Atzori and Lazzarin’s diagram

, , , Constants in the governing equations of the MWCM

0 El Haddad’s short crack constant

, n, n, n Constants of the MWCM calculated in terms of nominal net stresses

, , Components of unit vector a

, H Constants in Heywood’s formula

N Constant in Neuber’s formula

p Constant in peterson’s formula

2 Crack length

b Unit vector defining the orientation of axis

Fatigue strength exponent

0 Fatigue strength exponent under shear strain

, y, Components of unit vector b

Fatigue ductility exponent

0 Fatigue ductility exponent under shear strain

Hole diameter

Negative inverse slope

I, kII Non-dimensional quantities depending on the welded joint geometry

Negative inverse slope of the modified Wöhler curve

Actual length

0 Gauge length

Mean stress sensitivity index

Number of cycles

Strain hardening exponent

Cyclic strain hardening exponent

n Unit vector normal to plane

, , Components of unit vector n

Frame of reference

Frame of reference relative to plane

Polar coordinates

Notch sensitivity factor

q Unit vector defining the orientation of direction

, , components of unit vector q

n Notch root radius

Time

, Welded plate thickness

t Total stress vector

, , components of vector t

Weld bead height

Constant in Kuhn and Hardraht’s formula

initial value of the cross-sectional area

, Constants in the LM vs. Nf relationship

, Constants in Paris’ law

Notch depth

Young’s modulus

(%) Error

LEFM geometrical factor

Amplitude of the axial force

() Axial force

1, , First, second and third stress invariant

Strength coefficient

Cyclic strength coefficient

, K2, K3 Notch stress intensity factors due to Mode i, ii and iii loading

f Fatigue strength reduction factor

ft Fatigue strength reduction factor under torsional loading

Kf, e Estimated fatigue strength reduction factor

(f) Calibration functions for assessing composite materials ( = 1, 2,…, 6)

Kt Stress concentration factor

tt Stress concentration factor under torsional loading

Kt, gross Stress concentration factor referred to the gross area

t, gross t value defining the transition from the blunt to the sharp notch regime

t, net Stress concentration factor referred to the net area

C Fracture toughness

1C 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

Material characteristic length

Material characteristic length in the medium-cycle fatigue regime

T Material characteristic length under Mode III loading

t Torque

V Multiaxial critical distance value

Number of cycles to failure defining the position of the knee point

Number of cycles to failure

f, e Estimated number of cycles to failure

NA Reference number of cycles to failure

D Reference number of cycles to failure

S Reference number of cycles to failure in the low cycle fatigue regime

S Probability of survival

Load ratio (R = ,min/, max where = , , )

CP Load ratio relative to the critical plane

strain ratio

Period of the cyclic load history

Scatter ratio of reference shear stress amplitude for 90% and 10% probabilities of survival

F, a Amplitude of the strain energy density

F, A Reference amplitude of the strain energy density extrapolated at NA cycles to failure

2 Opening angle

? a Maximum shear strain...