A finite element analysis of temperature in accelerated cutting

Temperature attained during machining has significant effects on the properties of tool, chip and workpiece. It governs the parameters like shear angle, cutting force, tool wear, surface finish etc. Review of literature reveals that hardly any information is available about the analytical determination of the tool-chip interface temperature and the temperature distribution during the accelerated cutting.

This paper presents the temperature analysis of accelerated cutting (i.e. taper turning and facing) as well as longitudinal turning, using the finite element technique. It has been concluded that the temperature distribution within the tool-chip-work system and the average tool-chip interface temperature for the two classes of machining (viz longitudinal turning and accelerated cutting) are not the same, even though the conditions of machining are identical. Further, the average tool-chip interface temperature is lowest in case of facing and highest in case of longitudinal turning.     

Stochastic modeling of mean-wind profiles for in-flight wind estimation--A new approach to lower order stochastic realization schemes

A new approach has been proposed for the design of approximate, lower order discrete time realizations of stochastic processes from the output covariance matrix over a finite time interval. No restrictive assumptions are imposed on the process, that is, it can be nonstationary and also can lead to higher dimension realization. Classes of fixed order models ("guaranteed models") are defined having the joint covariance matrix of the combined vector of the outputs in the interval of definition greater than or equal to the process covariance matrix. The design is achieved by minimizing, in one of those classes, the approximation between the model and the process measured by the trace of the difference of the respective covariance matrices. The method has been employed in a practical problem of developing lower order wind models from a higher order covariance matrix in numerical form. The wind model is intended to be incorporated on board an aircraft maneuvering according to a four-dimensional guidance scheme in the neighborhood of the terminus of a flight. Choice of the order of the model and the resulting accuracies of the estimation schemes are compared.     

Further studies on redoxokinetic titrations

The previously described “redoxokinetic effect” is used to indicate the end-points of titrations of Fe²⁺ with Cr₂O₇^2-, sulphuric acid with sodium hydroxide, AsO₂- with I₂ and Ag⁺ with Cl⁻. With the first three systems an accuracy of 0·1 per cent is possible. The method is not suited to the fourth system.

Abstract

Titrations of sulphuric acid vs. sodium hydroxide at 0·1 N concentration and ferrous ammonium sulphate vs. potassium dichromate at 0·05 N concentration can be carried out with an accuracy of ±0·1 per cent using the redoxokinetic technique. A very sharp end-point was obtained in the case of iodine vs. arsenite titration at 0·1 N concentration. Silver nitrate vs. chloride titrations cannot be carried out by the redoxokinetic technique.

Addition of MnSO₄ to the extent of 50 g/l. of the solution enhances the precision considerably in the titration of dilute solutions of ferrous ammonium sulphate with dichromate.     

Studies on the ionic transport and structural investigations of La<Subscript>0.5</Subscript>Li<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript> perovskite synthesized by wet chemical methods and the effect of Ce,Zr substitution at Ti site

La_0.5Li_0.5TiO₃ perovskite was synthesized by various wet chemical methods. By adopting low temperature methods of preparation lithium loss from the material is prevented. La_0.5Li_0.5TiO₃ (LLTO) was formed with cubic symmetry at 1473 K. LLTO was formed at relatively lower temperature by using hydrothermal preparation method. PVA gel-decomposition route yield tetragonal LLTO on annealing the dried gel at 1473 K. By using gel-carbonate route LiTi₂O₄ minor phase was found to remain even after heat-treatment at 1473 K. The hydroxylation of LLTO was done in deionized water as well as in dilute acetic acid medium. By hydroxylation process incorporation of hydroxyls and leaching out of Li⁺ was observed from the material. The Li⁺ concentration of these compositions was examined by AAS. The electrical conductivities of these compositions were measured by dc and ac impedance techniques at elevated temperatures. The activation energies of electrical conduction for these compositions were estimated from the experimental results. The measured activation energy of Li⁺ conduction is 0.34 eV. Unhydroxylated samples exhibit only Li⁺ conduction, whereas, the hydroxylated LLTO show proton conductivity at 298–550 K in addition to Li⁺ conductivity. The effect of Zr or Ce substitution in place of Ti were attempted. La_0.5Li_0.5ZrO₃ Perovskite was not formed; instead pyrochlore phase (La₂Zr₂O₇) along with monoclinic ZrO₂ phases was observed above 1173 K; below 1173 K cubic ZrO₂ is stable. (La_0.5Li_0.5)₂CeO₄ solid solution was formed in the case of Ce substitution at Ti sublattice on heat-treatment up to 1673 K.     

Composite organic-inorganic nanoparticles (COINs) with chemically encoded optical signatures

To obtain a coding system for multiplex detection, we have developed a method to synthesize a new type of nanomaterial called composite organic-inorganic nanoparticles (COINs). The method allows the incorporation of a broad range of organic compounds into COINs to produce surface enhanced Raman scattering (SERS)-like spectra that are richer in variety than fluorescence-based signatures. Preliminary data suggest that COINs can be used as Raman tags for multiplex and ultrasensitive detection of biomolecules.     

The kinetics of hydrogen attack of steels

The hydrogen attack of steel involves the formation of methane bubbles along the grain boundaries and their subsequent link-up to form fissures. This paper presents a detailed model for the kinetics of growth of such methane bubbles. The model considers two parallel processes which can control the growth—one involving the bubble growth by direct power-law creep and the other involving combinations of surface diffusion, grain boundary diffusion and matrix accommodation processes. The proposed model is more general and complete than the earlier ones and considers for the first time the possibility of bubble growth being controlled by surface diffusion and accommodation processes. The predictions of the model are shown to compare well with the experimental results obtained in our lab and with the literature data. The model also indicates the relative importance of lower carbon activity and increased creep stength of steel to its hydrogen attack resistance.     

Demineralization by electrodialysis using ampholytic ion-conducting spacers

The synthesis of ampholytic ion-conducting spacers and their use in demineralization of low saline waters with cost of treatment are given. The various modifications on the use of conducting spacers in demineralization by electrodialysis are discussed. Extension of the technique in prevention of environmental pollution by recovery of valuable materials and/elimination of harmful ions in trace quantities is also described.     

Micro- and nano-tribological behavior of soybean oil-based polymers of different crosslinking densities

Biobased polymers produced from renewable and inexpensive natural resources, such as natural oils, have drawn considerable attention over the past decades, due to their low cost, ready availability, environmental compatibility, and their inherent biodegradability. In this study, the micro/nanotribological wear behavior of biopolymers with different crosslinking densities prepared from low saturated soybean oil (LSS) by cationic copolymerization with divinyl benzene and polystyrene are evaluated and compared. Microtribological measurements were performed using a ball-on-flat reciprocating microtribometer using two different probes −1.2 mm radius Si₃N₄ spherical probe and a 100 μm radius conical diamond probe with 90° cone angle. Nanoscale wear tests were performed using a DLC coated antimony (n) doped silicon probe of radius ∼200 nm in an atomic force microscope (AFM). Wear volumes were estimated from AFM topography maps of groove geometry and wear coefficients were evaluated for the materials. Elastic modulus and hardness information were evaluated using nanoindentation tests. Correlations between crosslinking density and observed wear behavior across scales are discussed. These results provide some insight into the wear behavior of soybean oil-based polymers.     

Irradiation Target Cooling Using Circular/Slot Air Jet

To study the effect of irradiation on materials, sample coupons are irradiated in cyclotron facilities. During the irradiation process, these samples produce significant heat. This heat needs to be continuously removed from the samples in order to avoid melting of the samples as well as to keep the samples at a particular temperature during irradiation. The area available for heat transfer is limited due to small size of the samples. To increase the heat transfer rate, jet cooling is used as it provides large heat transfer co-efficient. To understand the heat transfer characteristics of jet cooling under these conditions, experiments have been carried out. Two inclined jets hitting on both sides of the target plate give maximum cooling and uniform temperature distribution. This paper gives the details of the numerical and experimental studies carried out and the discussions about the results obtained.     

Luminomagnetic Nd3+ doped fluorapatite coated Fe3O4 nanostructures for biomedical applications

Luminomagnetic nanostructured Nd³⁺ doped fluorapatite (FAP) coated Fe₃O₄ nanoparticles were produced by hydrothermal method. X-ray diffraction analysis indicates that the prepared nanoparticles contain both FAP and Fe₃O₄ phases. Electron microscope analysis shows the formation of nanoparticles of Fe₃O₄ encased in rod shaped FAP nanoparticles of average length 40 nm. Magnetic measurements confirm the room temperature superparamagnetic nature of the nanoparticles with saturation magnetization value up to 7.8 emu/g. The prepared nanoparticles display strong near infrared (NIR) emission at 1060 nm under 800 nm excitation. Cell viability studies for 72 hour demonstrate the survival rate of over 84% with 500 μg/mL concentration indicating the good cytocompatibility of the prepared materials. The present Nd³⁺ doped FAP coated Fe₃O₄ nanostructure provides an excellent multifunctional platform for diagnostics and therapeutic applications.