The purpose of thisstudy is to evaluate the crack closure phenomenon of 2024-T3 aluminum alloy panel and the FSW panel joined by the *** attention on crack opening stress,its calculation using elasto-plastic FEM is co...
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The purpose of thisstudy is to evaluate the crack closure phenomenon of 2024-T3 aluminum alloy panel and the FSW panel joined by the *** attention on crack opening stress,its calculation using elasto-plastic FEM is conducted to clarify the influence of residual stress on crack opening *** calculated crack opening stress of base material and the FSW panel are in close agreement with the measured *** the FEM results show that the part of crack faces around FSW weld line is opened by tensile residual stress despite no external *** behavior conforms qualitatively to that of test *** da/dN—（?）K curves for FSW panel are obtained using the crack growth test results of base material and the calculated crack opening stress for base material and the FSW *** obtained curve conformed to the experimental result,indicating the crack growth rate of FSW panel could be predicted quantitatively by evaluating crack opening stress in elasto-plastic FEM.
We demonstrate nanoscale antireflection structures on GaAs substrate with linearly graded effective refractive index using a lenslike shape transfer for broadband light-absorbing device application. From reflectance c...
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We employ a parallel, three-dimensional level-set code to simulate the dynamics of isolated dislocation lines and loops in an obstacle-rich environment. This system serves as a convenient prototype of those in which e...
We employ a parallel, three-dimensional level-set code to simulate the dynamics of isolated dislocation lines and loops in an obstacle-rich environment. This system serves as a convenient prototype of those in which extended, one-dimensional objects interact with obstacles and the out-of-plane motion of these objects is key to understanding their pinning-depinning behavior. In contrast to earlier models of dislocation motion, we incorporate long-ranged interactions among dislocation segments and obstacles to study the effect of climb on dislocation dynamics in the presence of misfitting penetrable obstacles/solutes, as embodied in an effective climb mobility. Our main observations are as follows. First, increasing climb mobility leads to more effective pinning by the obstacles, implying increased strengthening. Second, decreasing the range of interactions significantly reduces the effect of climb. The dependence of the critical stress on obstacle concentration and misfit strength is also explored and compared with existing models. In particular, our results are shown to be in reasonable agreement with the Friedel-Suzuki theory. Finally, the limitations inherent in the simplified model employed here, including the neglect of some lattice effects and the use of a coarse-grained climb mobility, are discussed.
The generation of arbitrarily shaped nonspherical laser-induced cavitation bubbles is demonstrated with a optical technique. The nonspherical bubbles are formed using laser intensity patterns shaped by a spatial light...
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The generation of arbitrarily shaped nonspherical laser-induced cavitation bubbles is demonstrated with a optical technique. The nonspherical bubbles are formed using laser intensity patterns shaped by a spatial light modulator using linear absorption inside a liquid gap with a thickness of 40 μm. In particular we demonstrate the dynamics of elliptic, toroidal, square, and V-shaped bubbles. The bubble dynamics is recorded with a high-speed camera at framing rates of up to 300 000 frames per second. The observed bubble evolution is compared to predictions from an axisymmetric boundary element simulation which provides good qualitative agreement. Interesting dynamic features that are observed in both the experiment and simulation include the inversion of the major and minor axis for elliptical bubbles, the rotation of the shape for square bubbles, and the formation of a unidirectional jet for V-shaped bubbles. Further we demonstrate that specific bubble shapes can either be formed directly through the intensity distribution of a single laser focus, or indirectly using secondary bubbles that either confine the central bubble or coalesce with the main bubble. The former approach provides the ability to generate in principle any complex bubble geometry.
The phase behavior of hard superballs is examined using molecular dynamics within a deformable periodic simulation box. A superball’s interior is defined by the inequality |x|2q+|y|2q+|z|2q≤1, which provides a versa...
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The phase behavior of hard superballs is examined using molecular dynamics within a deformable periodic simulation box. A superball’s interior is defined by the inequality |x|2q+|y|2q+|z|2q≤1, which provides a versatile family of convex particles (q≥0.5) with cubelike and octahedronlike shapes as well as concave particles (q<0.5) with octahedronlike shapes. Here, we consider the convex case with a deformation parameter q between the sphere point (q=1) and the cube (q=∞). We find that the asphericity plays a significant role in the extent of cubatic ordering of both the liquid and crystal phases. Calculation of the first few virial coefficients shows that superballs that are visually similar to cubes can have low-density equations of state closer to spheres than to cubes. Dense liquids of superballs display cubatic orientational order that extends over several particle lengths only for large q. Along the ordered, high-density equation of state, superballs with 1
Dielectric elastomer actuators, consisting of an elastomer film sandwiched between two compliant electrodes, are of increasing interests in application. Due to the nonlinearity, the nature of large deformation and the...
Hydrophilicity/hydrophobicity is often used to identify the chemical properties of a material surface, which can be characterized by adhesion force variations measured by atomic force microscopy (AFM). The surface rou...
Hydrophilicity/hydrophobicity is often used to identify the chemical properties of a material surface, which can be characterized by adhesion force variations measured by atomic force microscopy (AFM). The surface roughness has a significant influence on adhesion. This study presents a systematic approach to the correlation among surface roughness, adhesion force, and hydrophilicity or hydrophobicity of materials. The surface topography was obtained on the surface of materials representing silicates, phylo‐silicates, calcites, and carbon. On the basis of the topographic image analysis of AFM, the root‐mean‐square (RMS) roughness was calculated. The results indicate that the adhesion force decreases with increasing RMS roughness.
Carbon dioxide (CO2) corrosion of carbon steel in the presence of brine has been a recognized problem in oil production for many years and it is becoming more common with the extensive use of CO2-flooding as an oil re...
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Large strain actuation in barium titanate (BaTiO3) single crystals subjected to combined uniaxial stress and electric field is examined. A maximum strain of about 0.45% is measured under a combined loading of 2.7 MPa ...
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