Unified triaxiality at the crack tip subjected to plane strain condition under mixed‐mode (I + II) fracture

The new model of stress triaxiality, subjected to plane strain condition under mixed‐mode (I + II) loading, at the yield loci of the crack tip, has been formulated using unified strength theory. It evaluates critical values of triaxiality for various convex and non‐convex failure criteria, unlike the existing model. It shows the effects of Poisson's ratio and intermediate principal stress for materials whose strength in tension and compression is either equal or unequal. Further, on this basis, the crack initiation angles are predicted for various crack inclinations and compared with those obtained from other fracture criteria. The plastic zone shapes supplement the results. Critical yield stress factor, a significant parameter at the crack tip got lowered as the difference among the three principal stresses reduced to a minimum. The crack initiation angles obtained from the model showed good agreement with those obtained from G‐, S‐, and T‐criterion.     

The Finite Analysis of Deformation and Stress Triaxiality of a Mixed I + II Mode Elastic-Plastic Crack Tip

The deformation and distribution of stress triaxiality σ_{_m}/σ of mixed I + II mode elastic-plastic cracks under plane strain and plane stress conditions were analysed by the large strain finite element method and were compared with the HRR field. The results show that, (1) the model of crack-tip deformation under mixed I + II mode loading is sharpening-blunting, the sharpening and blunting deformation is acted on by compressive stress (σ_{_m}/σ > 0) and tensile stress (σ_{_m}/σ > 0), respectively; (2) in the plane strain case, the (σ_{_m}/σ)_{_max} of the real crack tip decreases with an increase of mode II component, but increases with an increasing strain hardening n for every mixed ratio. For the loading of K_{_I}/K_{_II} > 0.5, the (σ_{_m}/σ)_{_max} value of the real crack tip is less than that of the (σ_{_m}/σ)_{_max} given by the HRR field, but the opposite holds true cases where K_{_I}/K_{_II} > 0.5; (3) in the plane stress case, the (σ_{_m}/σ)_{_max} decreases a few values with an increasing mode II component, the values of (σ_{_m}/σ)_{_max} of every mixed ratio are far less than these of the corresponding loading condition in the plane strain case. In the plane stress case, the (σ_{_m}/σ)_{_max} values of every mixed ratio for any strain hardening exponent n are almost constant. This revised version was published online in August 2006 with corrections to the Cover Date.     

Prediction of crack growth direction for mode I/II loading using small-scale yielding and void initiation/growth concepts

Under the assumption that the processes which control the direction of crack growth in 2024-T3 aluminum are directly related to void initiation and growth, a theoretical framework is developed to predict the direction of crack growth. The basic premise of the framework is that, depending on the mode mixity of the remotely applied loading, either σ _m /σ_eff or σ_eff triggers the nucleation and growth of voids hence, fracture. The theoretical development uses linear elastic assumptions and two terms in the asymptotic expansion to describe the stress field in the vicinity of the crack tip for a mixed-mode I/II ARCAN specimen. Predictions based on the theory indicate that: (a) the transition from Mode~I type to Mode~II type crack propagation can be accurately quantified, and (b) the direction of crack growth is reasonably well predicted for both types of crack propagation. In addition, a qualitative, but microstructurally based, physical rationale for the observed phenomena is presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Solid-state synthesis of amorphous iron(III) phosphate at room temperature and its absorption properties for Hg(II) and Ag(I) ions

Amorphous iron(III) phosphate has been synthesized by solid-state reaction at room temperature and was characterized by several methods. The non-crystalline sample displayed the particle size within the range of 100-200 nm, and it had a strong fluorescence emission peak centered at 306.6 nm. Moreover, its absorption properties for Hg(II) and Ag(I) heavy metal ions have been investigated. The experimental research results revealed that its excellent absorption capacity for Hg(II) and Ag(I) could reach to 1.831 mmol/g and 1.354 mmol/g, respectively, at pH = 5.98 and the absorption time t = 6 h. The absorption properties for Hg(II) were usually stronger that those for Ag(I).     

Brittle Mixed-Mode (I+II) Fracture: Application of the Equivalent Notch Stress Intensity Factor to Cracks Emanating from Notches

In the present paper, crack initiation in mixed-mode (I+II) fracture has been studied using notched circular ring specimens. A new criterion of brittle mixed-mode (I+II) fracture based on the notch tangential stress and the volumetric approach has been developed. The critical value of the equivalent notch stress-intensity factor has been considered as fracture toughness in mixed-mode (I+II) fracture.