A multi-wavelet based technique for calculating dense 2D disparity maps from stereo

A vision based approach for calculating accurate 3D models of the objects is presented. Generally industrial visual inspection systems capable of accurate 3D depth estimation rely on extra hardware tools like laser scanners or light pattern projectors. These tools improve the accuracy of depth estimation but also make the vision system costly and cumbersome. In the proposed algorithm, depth and dimensional accuracy of the produced 3D depth model depends on the existing reference model instead of the information from extra hardware tools. The proposed algorithm is a simple and cost effective software based approach to achieve accurate 3D depth estimation with minimal hardware involvement. The matching process uses the well-known coarse to fine strategy, involving the calculation of matching points at the coarsest level with consequent refinement up to the finest level. Vector coefficients of the wavelet transform-modulus are used as matching features, where wavelet transform-modulus maxima defines the shift invariant high-level features with phase pointing to the normal of the feature surface. The technique addresses the estimation of optimal corresponding points and the corresponding 2D disparity maps leading to the creation of accurate depth perception model.

Three-dimensional Finite Element modelling of laser shock peening process

Laser shock peening (LSP) is an innovative surface treatment technique for metal alloys, with the great improvement of their fatigue, corrosion and wear resistance performance. Finite element method has been widely applied to simulate the LSP to provide the theoretically predictive assessment and optimally parametric design. In the current work, 3-D numerical modelling approaches, combining the explicit dynamic analysis, static equilibrium analysis algorithms and different plasticity models for the high strain rate exceeding 106s-1, are further developed. To verify the proposed methods, 3-D static and dynamic FEA of AA7075-T7351 rods subject to two-sided laser shock peening are performed using the FEA package–ABAQUS. The dynamic and residual stress fields, shock wave propagation and surface deformation of the treated metal from different material modelling approaches have a good agreement.

CO2 laser manufacturing of miniaturised lenses for lab-on-a-chip systems

This article describes the manufacturing and characterisation of plano-convex miniaturised lenses using a CO2 laser engraving process in PMMA substrates. The technique allows for lenses to be fabricated rapidly and in a reproducible manner at depths of over 200 µm and for lens diameters of more than 3 mm. Experimental characterisation of the lens focal lengths shows good correlation with theory. The plano-convex lenses have been successfully embedded into capillary microfluidic systems alongside planar microlenses, allowing for a significant reduction of ancillary optics without a loss of detection sensitivity when performing fluorescence measurements. Such technology provides a significant step forward towards the portability of fluorescence- or luminescence-based systems for biological/chemical analysis.

Comparative study of the microstructures and mechanical properties of direct laser fabricated and arc-melted AlxCoCrFeNi high entropy alloys

High entropy alloys (HEA) are a relatively new metal alloy system that have promising potential in high temperature applications. These multi-component alloys are typically produced by arc-melting, requiring several remelts to achieve chemical homogeneity. Direct laser fabrication (DLF) is a rapid prototyping technique, which produces complex components from alloy powder by selectively melting micron-sized powder in successive layers. However, studies of the fabrication of complex alloys from simple elemental powder blends are sparse. In this study, DLF was employed to fabricate bulk samples of three alloys based on the AlxCoCrFeNi HEA system, where x was 0.3, 0.6 and 0.85M fraction of Al. This produced FCC, FCC/BCC and BCC crystal structures, respectively. Corresponding alloys were also produced by arc-melting, and all microstructures were characterised and compared longitudinal and transverse to the build/solidification direction by x-ray diffraction, glow discharge optical emission spectroscopy and scanning electron microscopy (EDX and EBSD). Strong similarities were observed between the single phase FCC and BCC alloys produced by both techniques, however the FCC/BCC structures differed significantly. This has been attributed to a difference in the solidification rate and thermal gradient in the melt pool between the two different techniques. Room temperature compression testing showed very similar mechanical behaviour and properties for the two different processing routes. DLF was concluded to be a successful technique to manufacture bulk HEA[U+05F3]s.