Properties of Curved Parts Laser Cladding Based on Controlling Spot Size

In this study, a method based on controlling the laser spot size was proposed in the process of curved parts laser cladding, and the coatings obtained by this method were analysed through investigation of the microstructure, microhardness, adhesion property and wear resistance properties. The nonuniform rational B-spline surface (NURBS) reconstruction method was used to obtain the workpiece geometrical characteristics of laser cladding, and through the establishment of a mathematical model, the process of the laser beam working on the curved surface was simplified as the intersection of the cylinder and curvature sphere. Then, the spot size was transformed into the area of a cylinder intersecting with a sphere, and by adjusting the laser head, the size of the laser spot was controlled in the threshold and interpolation points were obtained. The laser cladding trajectory was ensured by these interpolation points, and the experiment was carried out to study the properties of the coating. The results showed that the average coating thickness was about 1.07 mm, and the fluctuation of coating thickness did not exceed 0.05 mm; also, there were no cracks or pores in the layer after penetrant flaw detection. The SEM showed that the grains passed through the transition of plane crystal, cellular crystal, dendrite and equiaxed crystal from the bottom to the top of the layer. After 30 cycles of thermal shock tests, the cladding layer was still well bonded with the substrate and the microhardness and wear resistance were 2 times and 1.4 times higher than that of substrate, respectively.

Eshelby's tensor for embedded inclusions and the Elasto-Capillary phenomenon

The elastic state of an embedded inclusion undergoing a stress-free transformation strain was the subject of John Douglas Eshelby's now classical paper in 1957. This paper, the subject of which is now widely known as “Eshelby's inclusion problem”, is arguably one of the most cited papers in solid mechanics and several other branches of physical sciences. Applications have ranged from geophysics, quantum dots to composites. Over the past two decades, due to an interest in all things “small”, attempts have been made to extend Eshelby's elastic analysis to the nanoscale by incorporating capillary or surface energy effects. In this note, we revisit a particular formulation that derives a very general expression for the elasto-capillary state of an embedded inclusion. This approach, that closely mimics that of Eshelby's original paper, appears to have the advantage that it can be readily used for inclusions of arbitrary shape (for numerical calculations) and provides a facile route for approximate solutions when closed-form expressions are not possible. Specifically, in the case of inclusions of constant curvature (sphere, cylinder) subject to some simplifications, closed-form expressions are obtained.

Research on Triangularization of Parametric Surface Based on Surface Curvature

In five-axis tool path planning, interference between the cutting tool and parametric surface is very critical. One way of doing interference detection is first to discretize the surface. In this article we develop a new approach to discretize parametric surface adaptively by applying curvature sphere. Layer by layer the original surface is discretized into triangle meshes bases on the polyline between the triangulated and un-triangulated areas of the surface. Triangles generated with our method are adaptive, which means the density of the triangles changes with the local curvature value of the surface. We also develop a method to deal with triangle meshes overlapping problem. So triangle meshes generated with our algorithm is without gaps or any overlapping problem. Finally a criterion is suggested when the generation should stop. The algorithm has been tested for some parametric surfaces and the result turns out to be satisfactory.