Effects of cementite morphology on short-fatigue-crack propagation in binary Fe–C steel

The effects of cementite morphology on short-fatigue-crack propagation were investigated by subjecting smooth steel specimens to rotating-bending fatigue tests. Intergranular and transgranular cementite precipitation steels free of other phases were prepared through heat treatments. In the intergranular cementite precipitation steel, short-fatigue-crack propagation was decelerated at the grain boundaries, and accelerated in the grain interiors. In contrast, the transgranular precipitation steel showed the deceleration of the crack propagation in the grain interiors but not in the vicinity of the grain boundaries.     

Surface Colour is not a Perceptual Content

In this paper, I consider a view that explains colour experience by the independent representation of surface and illumination. This view implies that surface colour is a phenomenal perceptual content. I argue from facts of colour phenomenology to the conclusion that surface colour is not a phenomenal perceptual content. I then argue from results of surface-matching experiments to the conclusion that surface colour is neither a perceptual content of any kind nor any sort of computational output of the perceptual system. These conclusions contradict widely accepted views in both the philosophy of perception and colour science. I finish by considering and rejecting a competing account of the surface-matching results, according to which surface colour is represented indeterminately in perception.     

Screw misfit dislocations perpendicular to one or two free surfaces

ABSTRACT

When a screw dislocation pierces one or two free surface(s), noticeable elastic relaxation takes place nearby these surfaces. To refine the theoretical interpretation of an electron microscopy image this relaxation should be included in a precise imaging model. In the present work, the relaxation field is evaluated for a periodic set of misfit screw dislocations normal to the free surface of a semi-infinite or plate-like heterogeneous bicrystal. The proposed approach uses an appropriate combination of known biperiodic elastic fields. For a homogeneous medium and when the period increases, the results around a misfit screw dislocation converge to those of Eshelby and Stroh (1951) who considered an isolated translation screw dislocation.     

Density evolution during the growth of disc-shaped aluminium nanoparticles on a liquid surface

Aluminium (Al) nanoparticles (NPs) have been successfully fabricated on a liquid surface by thermal evaporation at room temperature. The Al NPs exhibit a disc-shaped morphology with mean diameter and height in the ranges 20–35 and 1.3–3.7?nm, respectively. As the nominal film thickness increases from 0.02 to 0.18?nm, the mean diameter and height are nearly independent of the thickness, implying that the density of the NPs increases during their growth. An explanation for this phenomenon is presented.     

Revealing texture architecture in a surface gradient nanostructured Al-Cu-Mg alloy

ABSTRACT

A multiscale crystallographic texture architecture in a surface gradient nanostructured Al-Cu-Mg alloy after surface sliding friction treatment (SSFT) has been revealed by a combination of electron backscatter diffraction and precession electron diffraction (PED)-assisted transmission electron microscopy (TEM) orientation mapping. Accompanying a grain structure variation from lamellar coarse grains to equiaxed nanograins, the major texture components evolve from brass {110}<112> in the coarse-grain matrix, Goss {110}<001> at a depth of ～80?μm, E {111}<011> and F {111}<112> at a depth of ～20?μm, to a mixture of rotated cube {001}<110>, E and F in the topmost surface layer. The through-thickness textural development and evolution are attributed to the cyclic loading of concurrent shear and compression during the SSFT processing. The PED-assisted orientation mapping shows good capability in mapping severe plastic-deformation-induced nanostructures with large residual strains and high defect density.     

Discontinuous cracking of TiN films on a steel substrate induced by an adhesive interlayer

ABSTRACT

The basic mechanisms governing the process of cracking of single-layer brittle films have been extensively explored through both simulations and experiments. However, the role that an adhesive interlayer plays in the cracking of the overlying brittle film remains unclear. By performing three-point bending experiments, we observed that the insertion of a 100?nm thick Ti interlayer changed the cracking behaviour of TiN films from a continuous pattern to a discontinuous pattern. The slight change in the microstructure of the film and the increase in film thickness arising from the addition of the Ti interlayer are unlikely to cause the observed cracking morphology. The combination of the different interface between the Ti and the steel substrate and the fracture of the Ti interlayer are responsible for the transition in the TiN film cracking morphologies.     

Relaxation of electrons following trapping in the space-charge-limited conduction regime of n + -i-n + hydrogenated amorphous silicon structures

The relaxation of a space charge due to trapped electrons in an n + -i-n + hydrogenated amorphous silicon structure has been modelled by Solomon. Here we extend the model by obtaining analytical expressions for the current at the beginning of the relaxation as well as for long times when retrapping of electrons is taken into account. Our expression for the current at long times differs considerably from that given previously. Consequences for the derived values of the capture cross-sections of the gap states near the Fermi level are examined and discussed.     

Simulation of surface effects on the intrinsic dissipation of nanooscillators

The rapid increase of surface area-volume ratio (SVR) with shrinking structure size has a great impact on surface-related intrinsic dissipation, which usually leads to low quality factors for the devices composed of nanoelectromechanical systems. In the present study, the flexural oscillations of nanocantilevers with varying thicknesses and lengths were simulated using the molecular dynamics method, in which the surface effects on the energy dissipation was evaluated when SVR was increased to extremely large values (between 0.4 and 2.0 nm^?1). And, it is also interesting to note that the prediction of the size-dependent Young's modulus by means of resonant frequency of the underdamped oscillation showed good agreement with previous findings.     

Equivalent strain-hardening work theorem

A new physical concept, termed ‘equivalent strain-hardening work’, is proposed. The physical concept can be used to redefine the commonly used effective stress and effective strain theory as applied in constructing the constitutive relations of stress and strain, especially when related to an anisotropic strain-hardening material. The concept concerns that part of plastic work which emphasizes the action due to the strain-hardening behaviour of a material. Based on this concept, any one of the strain-hardening stress–strain curves obtained through common experiments on anisotropic materials can be selected as a nominally effective stress and an associated effective strain, and the rest of the strain-hardening relations can all be then transformed to be functions of variables of the nominally effective strain. Thus, any kind of loading path can be characterized by a single relation between effective stress and effective strain. When applied to the isotropic materials, the equivalent strain-hardening work concept is identical with the work-equivalent deformation concept but is more general.