A review of the fatigue strength of structural materials under multiaxial loading in terms of the local energy density

Abstract

A review of some recent data from multiaxial fatigue data from different notched materials is carried out in the paper. The approach based on the strain energy density (SED) averaged over a control volume is first used to summarise uniaxial and multiaxial fatigue strength data of welded joints made of structural steel and aluminium alloys. In all welded joints, the weld toe and weld root regions are modelled like sharp, zero radius, V-notches with different opening angles. The control volume radius is 0.28 mm for structural steels, 0.12 mm for aluminium alloys. Afterwards the SED approach is applied to multi-axial fatigue data from plain and Vnotched specimens made of AISI 416 stainless steel (hardened and tempered state), subjected to tension, torsion and combined tension and torsion, both in-phase and out-of-phase. Notched specimens are characterised by a very small root radius, =0.1 mm, which results in high nonlinear effects ahead of the notch tips. All results are summarised in terms of WN (SED range versus cycles to failure) scatterbands. Together with the new results, a number of multiaxial fatigue data recently obtained from sharply notched specimens made of C40 steel (normalised state) and 39NiCrMo3 steel (hardened and tempered state) are represented with the aim to provide a global synthesis in terms of local SED. Finally a synthesis from Ti6Al4V alloy is carried out showing the capability of the SED approach to be applied also to light alloys.

The effect of loading rate on fracture energy of asphalt mixture at intermediate temperatures and under different loading modes

“…Single-edge notched beam (SENB) test [16][17][18], double-edged notched tension (DENT) test [19], disk shaped compact tension (DCT) test [20][21][22], Edge notched disc bend (ENDB) test [23][24][25][26][27], and semicircular bend (SCB) test [28][29][30][31][32][33][34][35][36][37], are to name a few. Disc-shaped compact tension (ASTM D7313-07a) and semicircular bending (SCB) tests [29,[38][39][40][41][42] are among the frequently used fracture specimens for evaluating fracture behavior of asphalt concretes. Cylindrical samples obtained from Superpave Gyratory Compactor (SGC) or cores achieved from field and underservice AC layers can be used to build SCB samples which is known as low-cost test.…”

Using XFEM Techniques to Predict the Damage of aluminum 2024T3 notched under tensile load

“…Torbani [10] investigated the damage of an O, U, V-shaped slotted plate where he used the point stress criterion combined with the equivalent material concept, he concluded that the accuracy of each failure criterion depends on essentially the characteristic of the notch and therefore the distribution of stresses around the edge of the notch. Other researchers such as berto and all [11] have worked on uniaxial and multiaxial fatigue for different types of notches. The approach is based on strain energy density (SED) of a steel and aluminum alloys structure to tension, torsion and combined tension and torsion.…”

Fatigue surface crack propagation and intersecting cracks in connection with welding residual stresses

“…In spite of significant progress in the study of the effect of welding residual stress on the fatigue crack growth rate, the interpretation of most results is given in terms of the stress intensity factor in the framework of the validity of linear elastic fracture mechanics. It should be noted that other failure theories such strain‐based criteria can also be used to predict the fatigue life of welded structures …”

“…It should be noted that other failure theories such strain-based criteria can also be used to predict the fatigue life of welded structures. [15][16][17][18][19][20][21][22] The nonsingular (T-stress) term in the Williams series expansion 23 characterizes the crack-tip constraint and plays significant role in linear elastic fracture mechanics having influence on the crack-tip plastic zone, the fracture toughness, crack paths, and the fatigue crack growth rate (eg, previous studies [24][25][26][27][28][29][30][31][32] ). Seitl and Knesl 32 have introduced the T-stress in the Paris-Erdogan law to reflect the effect of crack-tip constraint on the fatigue crack propagation rate.…”