A STOCHASTIC CHARACTERIZATION OF THE MACHINE TOOL WORKPIECE SYSTEM IN BTA OEEP HOLE MACHINING Part I: Mathematical Modelling and Analysis

A three dimensional model of the BTA deep-hole machining system is presented by modelling each of the components separately and later combining to represent the total system. A model for the interaction between the workpiece and the cutting tool is also included. Such a model can determine the response of any component of the machine tool as well as the individual influence on the system performance. Based on this, physical models representing the three working methods in the BTA process can be studied, from which stochastic differential equations are derived to represent the resultant force system on the machine tool

A physical model for the stationary workpiece and rotating cutting tool working method is developed. The assumed modes method along with the Lagrange' equation is used to obtain the stochastic differential equation to represent the influence of axial force and torque, in order to obtain the response of the system under the action of the axial force and torque to predict the stability behaviour.     

Ring hydrogenation of naphthalene and 1-naphthol over supported metal catalysts in supercritical carbon dioxide solvent

Catalytic ring hydrogenations of naphthalene and 1-naphthol were studied over several supported metal catalysts in supercritical carbon dioxide solvent at low temperature. Higher concentration of hydrogen in supercritical carbon dioxide and lower reaction temperature were responsible for higher catalyst activity and selectivities to the desired partial ring hydrogenated products as compared with those observed in organic solvent for the same catalyst.     

Development and Validation of HPTLC Method for Estimation of Tacrolimus in Formulations

A new, simple, and rapid high-performance thin-layer chromatographic method with a derivatization procedure was developed and validated for quantitative determination of tacrolimus. Tacrolimus was chromatographed on silica gel 60 F₂₅₄ TLC plate using toluene–acetonitrile–glacial acetic acid (6:4:0.1, by volume) as mobile phase. Tacrolimus was visualized using a derivatization reagent containing anisaldehyde–sulfuric acid in absolute alcohol and quantified by densitometric analysis in the reflectance mode at 675 nm. The method was found to give compact spots for the drug (R_f?=?0.40?±?0.03). The linear regression analysis data for the calibration plots showed good linear relationship with r²?=?.9989 in the concentration range 100–800 ng/spot. The method was validated for precision, recovery, repeatability, and robustness as per the International Conference on Harmonization guidelines. The minimum detectable amount was found to be 28.90 ng, whereas the limit of quantitation was found to be 97.04 ng. Statistical analysis of the data showed that the method is precise, accurate, reproducible, and selective for the analysis of tacrolimus. The method was successfully employed for the estimation of equilibrium solubility and quantification of tacrolimus as a bulk drug and in commercially available capsules and in-house developed self-microemulsifying formulations.     

Optical Kerr switching technique for the production of a picosecond,multiwavelength CO2 laser pulse

A wavelength-independent method for optical gating, based on the optical Kerr effect, has been demonstrated. Using this method, we produced 100-ps, 10-kW, two-wavelength pulses (10.3 and 10.6 microm) with a signal-to-background ratio contrast of 10(5) by slicing a long CO2 pulse. The capability of gating consecutive pulses separated on a picosecond time scale with this method is also shown.     

Activity performance and kinetics for glycerol carbonylation with urea over Zn-Co mixed metal oxide catalyst

Efficient carbonylation of glycerol using urea with Zn-Co mixed metal oxide (MMO) catalyst has been achieved. Various methods of catalyst preparation were explored for glycerol carbonate (GC) synthesis. The optimized method of catalyst preparation was found to be co-precipitation (CP) with a Zn:Co ratio of 70:30, achieving 81% glycerol conversion with 97% GC selectivity. X-ray diffraction (XRD) studies revealed the formation of ZnO, Co₃ O₄, and spinel ZnCo₂O₄ phases. Thermal treatment given to the catalyst allows insertion of Zn cations into Co₃O₄ lattice forming ZnCo₂O₄ phase which was also evidenced in X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Herein, for the first time, reaction kinetics was studied to propose the rate equation, based on which a plausible reaction pathway is proposed involving two-site adsorption of glycerol (basic site) and urea (acidic site), which undergo carbonylation followed by cyclization into GC. A recycle study and hot filtration test have proven the reusability of the catalyst.     

Vibration of higher-order-shearable pretwisted rotating composite blades

The free and forced vibration of a rotating, pretwisted blade modeled as a laminated composite, hollow (single celled), uniform box-beam is studied. The structural model includes transverse shear flexibility, restrained warping, and centrifugal and Coriolis effects. A key element of this model is its ability to satisfy the zero shear–traction requirement on the external bounding surfaces. The governing system possesses complicated and eigenvalue-dependent natural boundary conditions. Hence an extended Galerkin method using admissible functions is employed. Free-vibration results obtained for the present higher-order shearable model are compared with those of the existing first-order shearable and the non-shearable models. For the data considered, the present theory provides conservative predictions. This suggests that through-the-thickness variations of transverse shear strains are significant and should be considered when pursuing non-resonant designs. The effect of pretwist, while marginal for the lowest eigenfrequency, is substantial for the higher ones especially for lower rotation speeds and larger ply angles. A combination of softening and stiffening effects are also possible for the same eigenfrequency when pretwist is varied. Tailoring studies using the present model show an enhancement of eigenfrequency characteristics and also reveal the potential for passive mitigation of forced response.     

A STOCHASTIC CHARACTERIZATION OF THE MACHINE TOOL WORKPIECE SYSTEM IN BTA DEEP HOLE MACHINING Part II: Response Analysis and Evaluation of the Tool Tip Motion

In this paper, the solutions to the stochastic differential equations, which mathematically represent the machine tool work-piece system in BTA deep hole machining are presented. The solutions to the parametric stochastic differential equations have been obtained using the well known averaging technique. The non-parametric inhomogeneous equations have been solved using the Fokker-Planck equation. Based on these solutions, the true motion of the tool tip has been described using the maximum, average and minimum deviation curves. These curves predict that helical grooves will be formed on the workpiece and such helical grooves were observed on the workpieces. Also, the maximum, average and minimum values of deviation of the tool tip which is a measure of the roundness error are established. Based on these results an upper bound for the roundness error as a function of depth of hole is derived. The measurement of roundness of the specimens reveals that the experimental values be in the zone predicted by the theory in a finite region. So it can be speculated that the resultant force system is not completely balanced at the pads.