No abstract

The aim of this research is to identify the optimum levels of leading laser cutting parameters for accomplishing precise cut geometry with better quality for cutting of newly developed Basalt-Glass-Kevlar 29 hybrid FRP composite laminate. The total of 42 experiments have been performed on a 2.34 mm thick laminate using a 250W pulsed Nd:YAG laser cutting system. Lamp current, pulse width, standoff distance, compressed air pressure, and cutting speed have been selected as variable laser cutting parameters. Thereafter, grey relational analysis approach has been adopted to single index optimization of top and bottom kerf deviation, simultaneously. These optimal solutions have been validated by comparing the results of confirmation experiments and found satisfactory improvement. Standoff distance has been observed as the most influencing parameter for both top and bottom kerf deviation.

In laser beam machining, the geometrical precise cutting of fiber reinforced polymer (FRP) composite materials is a challenging task in order to produce a higher quality cut. The aim of the present research is to determine optimum levels of cutting parameters able to provide geometrically accurate cut for 1.60 mm thick Basalt Fiber Reinforced Polymer (BFRP) composite laminate. The total of 42 experiments have been performed on a 250W pulsed Nd:YAG laser system. During experimentation, the lamp current, pulse width, pulse frequency, compressed air pressure and cutting speed have been varied to evaluate different kerf quality characteristics such as top and bottom kerf width, top & bottom kerf deviation, and kerf taper. Experimental results have been used to single index optimization of evaluated multiple kerf quality characteristics. A hybrid grey relational analysis coupled with genetic algorithm approach has been adopted for the optimization. The optimum levels of cutting parameters have been found at moderate lamp current (184.5 Amp), lower pulse width (2 ms), compressed air pressure (8 kg/cm 2) and cutting speed (50 mm/min) and higher pulse frequency (30 Hz). Finally, confirmation experiments have been conducted and it has been observed that optimal levels of cutting parameters are able to improve top kerf width, bottom kerf width, top kerf deviation, bottom kerf deviation, and kerf taper by 13.33 %, 13.29 %, 23.52 %, 23.07 %, and 10.83 %, respectively. From the experimental results, it has been found that lamp current is the most significant parameter for all kerf quality characteristics.

Copper molds are critical components in the continuous casting of steel. Surface condition of the mold directly affects product quality, and premature failure/low wear life affects the output of the continuous casting plant. This paper presents the failure analysis of a nickel coating on a copper plate during a plant trial using in situ ultrasonic testing for coating thickness evaluation and in situ testing to confirm the loss of coating. The failure analysis indicated maximum coating wear near the bottom corners of the mold. More wear was found on the wide end face compared with that observed on the narrow face. On top portion of the mold, wear was almost negligible. Based on the wear profile obtained during trial, it was recommended that the coating on the bottom portion of the mold have a higher hardness to improve mold life.

The proportion of Fe-Zn intermetallic phases in the galvannealed coating are of great importance to their final performance with respect to weldability, formability, paintability, etc. In the present study, an attempt has been made to quantify different Fe-Zn intermetallic phases present in the galvannealed coating on three different grades of steel. These coatings were analyzed by galvanostatic methods, and percentages of the Fe-Zn intermetallic phases in the coating were determined. Unlike other methods, the galvanostatic technique does not require any sample preparation or calibration for coating phase characterization; therefore, it is a simple method compared to other techniques.Galvannealed coating is produced by in-line heat treatment of the zinc coating, which is carried out by heating the coated steel immediately after zinc bath to approximately 550°C and holding there for a few seconds. This leads to alloying of zinc with the iron by diffusion. After this heat treatment, the average iron content of galvannealed coating is about 10 wt pct, which varies from 7 wt pct (at the top of the coating) to 23 wt pct (near steel interface), and the coating becomes a layered structure of Fe-Zn intermetallic phases. [1,2] The optimum alloyed galvannealed microstructure consists of a thin iron-rich gamma (C) layer of about 1-lm thickness and an overlay containing delta (d) phase, interspersed with a small amount of zeta (f) phase, at the top. The ranges of iron content of the f, d, and C phases are 5 to 6, 7 to 11, and 23 to 28 wt pct, respectively. [2] Different Fe-Zn intermetallic phases in the galvannealed coating have distinct anodic dissolution potential. Therefore, at a given current density, dissolution of each alloy layer takes place at a particular potential. The length of the time (in the galvanostatic potential-time curve) for which this particular dissolution potential is sustained is the measure of the thickness of the same layer in the galvannealed coating. [3] Quantification of galvannealed coating phases using the galvanostatic method is based on the aforementioned principle. The galvanostatic method is an indirect method for coating phase characterization compared to other metallurgical techniques such as scanning electron microscopy with energy-dispersive spectroscopy (EDS) and glow discharge optical emission spectroscopy (GDOES). However, once the relation between the morphological structure and galvanostatic curve is known, the method can be used in a much simpler way to characterize any layered metallurgical structure. The galvanostatic method does not require calibration or sample preparation unlike other methods such as GDOES (requires calibration) and EDS (requires sample preparation). This method is simple and therefore can be effectively used for characterization and quantification of galvannealed coating phases, because the microstructures of galvannealed coatings are known.The coating phases of three different galvannealed steels (named as S 1 , S 2 , and S 3 ) were characterized by galvano...