Evolution of active species and discharge sparks in Na2SiO3 electrolyte during PEO process

For the plasma electrolytic oxidation (PEO) of Mg alloy in Na₂SiO₃ electrolyte, optical emission spectroscopy (OES) was adopted to identify the active plasma species at the four stages and the evolution of the discharge sparks in the PEO process was analyzed. At the conventional anodic oxidation stage the emitting-light was correlated to the “flaws” in the oxide films. At the transition stage the active species were O₂ and H₂O. At the transition stage, the collapse and ionization of the bubble layer happened. At the plasma discharge stage, the active plasma species transited and emitted light. The main active plasma species of the micro-discharges were Na, K, Mg, H_α, O₂⁺ and OH. At the arc discharge stage, the energy was not uniform and the discharge was uneven, the light intensity increased sharply, O⁺ and O were excited.     

RESEARCH ON ADAPTIVE DATA COMPRESSION METHOD FOR TRIANGULATED SURFACES

NC code or STL file can be generated directly from measuring data in a fas re-verse-engineering mode. Compressing the massive data from laser scanner is the key of the new mode.An adaptive compression method based on triangulated-surfaces model is put forwar. Normal-vectoranges between triangles are computed to find prime vertices for removal. Ring data structure isadopted to save massive data effectively. It allows the efficient retrieval of all neighboring vertices andtriangles of a given vertices. To avoid long and thin triangles, a new re-triangulation approach based onnormalized minimum-vertex-distance is proposed, in which the vertex distance and interior angle oftriangle are considered. Results indicate that the compression method has high efficiency and can getreliable precision. The method can be applied in fast reverse engineering to acquire an opimal subsetof the original massive data.     

ADAPTIVE MEASUREMENT METHOD BASED ON CHANGING-CURVATURE FOR UNKNOWN FREE-FORM SURFACE

Current measurement method for unknown free-form surface has low efficiency. To acquire given precision, a lot of null points are measured. Based on change surface curvature, a new measurement planning is put forward. Sample step is evaluated from the change curvature and the locally-bounded character of extrapolating curve. Two coefficients, maximum error coefficient and local camber coefficient, are used to optimize sampling step. The first coefficient is computed to avoid sampling-point exceeding the measurement range and the second control sampling precision. Compared with the other methods, the proposed planning method can reduce the number of the measuring-point efficiently for the given precision. Measuring point distributes adaptively by the change surface curvature. The method can be applied to improve measurement efficiency and accuracy.