The role of notch tip shape and radius on deformation mechanisms of 12Cr1MoV steel under impact loading. Part 1. Energy parameters of fracture

Abstract

Impact loading curves and fracture energy of the notched 12Cr1MoV ductile steel specimens are analysed. The qualitative description and quantitative parameters are obtained for major stages of ductile and brittle fracture depending on the shape of the notch and the stress stiffness ahead. It was shown that a zone with enhanced plasticity forms in the vicinity of V‐, U‐ and I‐shaped notches at 20 °C testing temperature, giving rise to ductile fracture. The stress stiffness at the notch tip increased with testing temperature reduced to −40 °C. We demonstrated that the size of shear lips on a fracture surface is a quantitative characteristic of fracture. Using this approach, which is close by nature to non‐linear fracture mechanics, together with the quantitative description of fracture surfaces, a physical–mechanical scheme of the specimen fracture was suggested for the case of enhanced and localized (constrained) plasticity near the stress concentrator tip.

Ductile failure prediction of thin notched aluminum plates subjected to combined tension-shear loading

“…Unlike brittle and quasi-brittle materials, ductile materials have widespread applications in engineering structures that their static failure is usually gradual and their final fracture takes place in a stable manner [7,8]. Such a failure behavior is mainly due to significant plastic deformations [9,10]. If a notched component is made of a ductile material, it is expected that the crack initiation from the notch border and the crack growth will accompanied by a considerable plastic zone around the notch.…”

The role of notch tip shape and radius on deformation mechanisms of 12Cr1MoV steel under impact loading. Part 2. Influence of strain localization on fracture and numeric simulations

“…The specimens of the steam pipe steel 12Cr1MoV were cut by electro‐erosion. The detail of specimen preparation and testing are given in the Part I of the present work . They were subjected to standard thermal treatment involving normalisation at T = 960–980 °C followed by high temperature annealing at T = 740–760 °C.…”

“…In the part I of this work, we considered the effect of the notch shape on the stress–strain distribution and fracture initiation and propagation in the Charpy specimens of a ductile heat resistant 12Cr1MoV steel. With the focus on the energy of fracture initiation and propagation, it was demonstrated that the stress risers in the form of V‐shaped, U‐shaped and I‐shaped notches leads to formation of a zone with enhanced plasticity and ductile fracture at 20 °C.…”

The peak stress method to calculate residual notch stress intensity factors in welded joints

“…In fatigue‐susceptible welded structures, cracks usually initiate and propagate from the weld toe and the weld root regions, which are stress concentration points. According to the notch stress intensity approach, the weld toe is modelled as a sharp V notch (0 radius), as proposed in the literature in the last 2 decades . The mode I and mode II notch stress intensity factors (NSIFs) quantify the magnitude of the asymptotic stress distribution according to the Williams exact solution .…”

“…According to the notch stress intensity approach, the weld toe is modelled as a sharp V notch (0 radius), as proposed in the literature in the last 2 decades. [13][14][15][16][17] The mode I and mode II notch stress intensity factors (NSIFs) quantify the magnitude of the asymptotic stress distribution according Nomenclature: a, sharp V notch or crack depth; a 0 , b 0 , molten pool dimensions; c 1 , c 2 , molten pool dimensions; d, adopted average finite element size; f 1 , f 2 , constants for the energy distribution of the heat flux; q, power density of the heating source; r, θ, cylindrical coordinates; t, actual time of welding process simulation; v, welding speed; K I , mode I stress intensity factor; K 1 , mode I notch stress intensity factor; Q, absorbed power; Q*, power input; η, efficiency; λ 1 , first Williams eigenvalue; σ n , nominal stress at the gross section; σ r , σ θ , stress components in a cylindrical frame of reference; σ I,peak , mode I, singular linear elastic peak stress calculated by finite element method at the sharp V-notch tip by means of a given mesh pattern; τ, time at which the heat flux reaches its maximum value; 2α, opening angle of the sharp V notch to the Williams exact solution. 18 In case of weld-like geometries, the NSIFs quantify the intensity of the elastic stress field near the weld toe and the weld root, which take into account the overall joint geometry (both local, ie, the weld shape effect, and global), the absolute dimensions, and the loading condition.…”