Mirror milling is an effective and environmentally friendly means to manufacture large thin-walled parts. The remaining wall thickness of such parts is supposed to be strictly controlled to balance strength and weight reduction. However, the clamping deformation will lead to overcut or undercut if the nominal tool path is directly utilized. To address this issue, it would be helpful to scan and reconstruct the deformed unknown workpiece surface and then adjust the nominal tool path. In this paper, an automatic profile tracking approach is proposed to adaptively sample the deformed surface and reconstruct the surface model, based on a multi-ultrasonic-probe measurement system. The adaptive sampling algorithm calculates the position and surface normal of the next sampling point simultaneously based on a curvature sphere, which utilizes the surface information of the local area covered by the multi-ultrasonic-probe system. Moreover, a boundary processing algorithm is proposed to ensure the sampling process is carried out inside the boundary. The feasibility of the proposed automatic measurement method was validated through experiment.
SiC/SiC composites with high thermal conductivity shows promising application in field of fusion reactors. In this work, CNTs papers were fabricated by a vacuum filtration strategy while using pitch-based carbon fibers to build a network structure into SiC/SiC composite (SiC-CNTs-C/SiC, SCCS). The thermal conductivity and related mechanical properties before and after heat treatment at different temperature were investigated. The bonding between CNTs paper layers and SiC matrix were mainly mechanical. Compared to the composite without transfer channels, the bending strength of SCCS (434.54MPa) increased by 19% due to the reinforcement of transfer channels from the network structure. However, the damage to SiC fibers resulting from high temperature treatment adversely affected the mechanical properties. The disorder degree of SiC matrix and SiC fibers decreased after heat treatment while mean free path of phonons increased, which are conducive to heat transfer. Contracted to room temperature, the measured thermal conductivity at 1600℃ was 53.83 W/(m·K) in vertical direction and 29.85 W/(m·K) in plane. In summary, heat treatment apparently enhanced thermal conductivity of SCCS composites while partly sacrificed the mechanical properties.
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