The experimentally determined marked rise of the stress intensity factor required to initiate crack propagation in brittle solids under variably high loading rates, is analyzed. This problem of fracture initiation at the tip of a crack is considered in terms of activating a flaw at some distance away from the tip. By using a semi-infinite crack in an unbounded two-dimensional solid subjected to...

In the framework of crack number density analysis, a theoretical investigation is carried out on the relationship between the statistical characteristics of fatigue initiation life and the stochastic growth of short fatigue cracks. The numerical results indicate that, compared with the influence of grain boundary resistance, the effect of the degree of randomness of crystallographic crack growt...

A new multiaxial high-cycle fatigue initiation life prediction model for railroad wheels is proposed in this paper. A general fatigue damage analysis methodology for complex mechanical components is developed and applied to the wheel/rail rolling contact fatigue problem. A 3-D elasto-plastic finite element model is used for stress analysis. A submodeling technique is used to achieve both comput...

Converting chemical energy into electricity is done by an electro-chemical device known as a fuel cell. Thermal stress is caused at high operating temperature between 700 oC to 1000 oC of SOFC. Thermal stress causes gas escape, structure variability, crack initiation, crack propagation, and cease operation of the SOFC before its lifetime. The aim of this study is to presen...

The main aim of this paper is to present more accurate stochastic fatigue models for solving the fatigue reliability problems, which are attractively simple and easy to apply in practice for situations where it is difficult to quantify the costs associated with inspections and undetected cracks. From an engineering standpoint the fatigue life of a structure consists of two periods: (i) crack in...

Age-related deterioration of the fracture properties of bone, coupled with increased life expectancy, is responsible for increasing incidence of bone fracture in the elderly, and hence, an understanding of how its fracture properties degrade with age is essential. The present study describes ex vivo fracture experiments to quantitatively assess the effect of aging on the fracture toughness prop...

The aging-related deterioration of the fracture properties of bone, coupled with higher life expectancy, is responsible for increasing incidence of bone fracture in the elderly; consequently, an understanding of how these fracture properties degrade with age is essential. In this study, ex vivo fracture experiments have been performed to quantitatively assess the effect of age on human cortical...

Nickel-base superalloys have become the key materials of hot-end components in the aeroengines over the past several decades. Nickelbase superalloys are easy to produce thermo-mechanical fatigue (TMF) behavior when withstanding the combined effects of high temperature, creep, oxidation, mechanical stress and thermal stress. The occurrence of TMF seriously affects the normal service for hot-end ...

The effect of low cycle fatigue (LCF) predamage on the subsequent very high cycle fatigue (VHCF) behavior is investigated in TC21 titanium alloy. LCF predamage is applied under 1.8% strain amplitude up to various fractions of the expected life and subsequent VHCF properties are determined using ultrasonic fatigue tests. Results show that 5% of predamage insignificantly affects the VHCF limit du...

A continuum crystal plasticity model is used to simulate the material behavior of a directionally solidified Ni-base superalloy, DS GTD-111, in the longitudinal and transverse orientations. Isothermal uniaxial fatigue tests with hold times and creep tests are conducted at temperatures ranging from room temperature (RT) to 1038°C to characterize the deformation response. The constitutive model i...