Statistical assessment of notch toughness against cleavage fracture of ferritic steels

Abstract

The work is an initial effort on adopting a statistical approach to correlate the fracture behavior between a notched and a fracture mechanics specimen. The random nature of cleavage fracture process determines that both the microscopic fracture stress and the macroscopic properties including fracture load, fracture toughness, and the ductile to brittle transition temperature are all stochastic parameters. This understanding leads to the proposal of statistical assessment of cleavage induced notch brittleness of ferritic steels according to a recently proposed local approach model of cleavage fracture. The temperature independence of the 2 Weibull parameters in the new model induces a master curve to correlate the fracture load at different temperatures. A normalized stress combining the 2 Weibull parameters and the yield stress is proposed as the deterministic index to measure notch toughness. This proposed index is applied to compare the notch toughness of a ferritic steel with 2 different microstructures.

Fatigue behaviors of laser hybrid welded AA7020 due to defects via synchrotron X‐ray microtomography

“…As a detailed comparison, an inner pore with 10 times diameter of a surface pore cannot initiate a crack under exactly the same condition . It is thus concluded that internal defects have little probability to initiate a crack especially in both low cycle and high cycle fatigue regimes …”

“…17 It is thus concluded that internal defects have little probability to initiate a crack especially in both low cycle and high cycle fatigue regimes. 8,[31][32][33] Currently, few systematical investigations are performed on the influence of gas pores on fatigue damage behaviors of fusion welded Al alloys. By the synchrotron radiation X-ray computed microtomography (SR-μCT) and fatigue experiments, current work tentatively reveals the relationship between the pore and crack initiation and propagation of hybrid laser welded AA7020-T651.…”

Structural reliability analysis and uncertainties‐based collaborative design and optimization of turbine blades using surrogate model

“…To improve the performance of blades, it is necessary to analyze the coupling mechanism between shockwave and boundary layer . Many valuable studies have been proposed to perform this analysis by means of numerical simulations combining with physics of failure modeling . Among them, Wang et al utilized a reliability index strategy and proposed an uncertainty‐based optimization model for the structure design problem with bounded uncertain information.…”

“…9 Many valuable studies have been proposed to perform Nomenclature: X R , continuous random variable; M XR ξ ð Þ, the moment generating function of X R ; K XR ξ ð Þ, the cumulant generating function of X R ; f XR x R ð Þ, the probability density function of X R ; e ξ, the saddlepoint; ϕ(•), the standard normal probability density function of X R ; Φ(•), the standard normal cumulant generating function of X R ; X, the vector of local design variables; X S , the vector of shared design variables; Y ji , the vector of coupling variables which are the output of discipline j; Y ij , the vector of coupling variables which are the output of discipline i; J, the compatibility constraint; Pr(•), the reliability constraints this analysis by means of numerical simulations combining with physics of failure modeling. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Among them, Wang et al 10 utilized a reliability index strategy and proposed an uncertainty-based optimization model for the structure design problem with bounded uncertain information. Correia et al 11 proposed a generalization probabilistic fatigue model which can include multiaxial loading conditions and mean-stress effects.…”

Fatigue damage and reliability assessment of subway train bogie frames under operating conditions

“…12 The probabilistic designing in engineering application has been an increasingly tendency. [13][14][15][16] The dynamic stress of the bogie frame usually consists of the contribution from the elastic vibration of the frame structure under the wheel-track excitations and the resulted damage at critical areas presents probabilistic characteristics. Therefore, a reliability assessment method considering the probabilistic characteristics during the real operation is required.…”