Analysis of thermal errors in a high-speed micro-milling spindle

Thermally induced errors account for the majority of fabrication accuracy loss in an uncompensated machine tool. This issue is particularly relevant in the micro-machining arena due to the comparable size of thermal errors and the characteristic dimensions of the parts under fabrication. A spindle of a micro-milling machine tool is one of the main sources of thermal errors. Other sources of thermal errors include drive elements like linear motors and bearings, the machining process itself and external thermal influences such as variation in ambient temperature. The basic strategy for alleviating the magnitude of these thermal errors can be achieved by thermal desensitization, control and compensation within the machine tool.This paper describes a spindle growth compensation scheme that aims towards reducing its thermally-induced machining errors. The implementation of this scheme is simple in nature and it can be easily and quickly executed in an industrial environment with minimal investment of manpower and component modifications.Initially a finite element analysis (FEA) is conducted on the spindle assembly. This FEA correlates the temperature rise, due to heating from the spindle bearings and the motor, to the resulting structural deformation. Additionally, the structural deformation of the spindle along with temperature change at its various critical points is experimentally obtained by a system of thermocouples and capacitance gages.The experimental values of the temperature changes and the structural deformation of the spindle qualitatively agree well with the results obtained by FEA. Consequently, a thermal displacement model of the high-speed micro-milling spindle is formulated from the previously obtained experimental results that effectively predict the spindle displacement under varying spindle speeds. The implementation of this model in the machine tool under investigation is expected to reduce its thermally induced spindle displacement by 80%, from 6 microns to less than 1 micron in a randomly generated test with varying spindle speeds.     

On the Theory of Two-Temperature Thermoelasticity with Two Phase-Lags

The present paper is concerned with the theory of two temperature thermoelasticity with two phase-lags in which the theory of heat conduction in deformable bodies depends on two distinct temperatures – the conductive temperature and the thermodynamic temperature. A generalized heat conduction law with dual-phase-lag effects was proposed by Tzou (1995) for the purpose of considering the delayed response in times due to the microstructural interactions in the heat transport mechanism. Recently, Quintanilla (2008) has proposed to combine this constitutive equation with a two temperature heat conduction theory and has proved that a dual-phase-lag theory with two temperatures is a well-posed problem. In the present work we consider the basic equations concerning this dual-phase lag theory of two temperature thermoelasticity and make an attempt to establish some important theorems in this context. A uniqueness theorem has been established for a homogeneous and isotropic body. An alternative characterization of mixed boundary initial value problem is formulated and a variational principle as well as reciprocal principle have been established.     

Fabric Objective Measurement: A Comparative Study of Fabric Characteristics

The general characteristics of eight fabric groups as measured by the KES-F system are described. These fabric groups are divided by fibre content, fabric construction and special finishing treatment. Using silk fabric as a reference, caustic-reduced polyester fabrics exhibit strong silk-like characteristics except in their surface properties. Liquid ammonia-treated cotton fabrics also possess a certain silky hand. Micro-fibre fabrics are soft and smooth, but they do not have the high Kishimi hand which is typical of silk fabrics. Fabric construction has some influence on fabric stiffness, but not on hysteresis. Polyester-lining fabrics have high bending stiffness and polyester/cotton fabrics have very high shear stiffness and hysteresis. These two groups of fabrics are the least silk-like. Shear properties and bending hysteresis appear to be the most important factors affecting the hand of the fabrics studied.     

Structure/Property Relationships of Poly(ethylene terephthalate) Continuous-filament Yarn

Two commercial PET yarns, one as-spun and the other highly crystalline and drawn, were annealed at l8°C under various conditions. Mechanical and thermal-response measurements were made under high transient-heating conditions by using a UMIST-built Universal Fibre Tester (UFT). Differential-scanning-calorimetry (DSC) measurements were also made. A middle endotherm was observed on DSC traces for both the PET samples that had been annealed freely (free to shrink). Further thermo-mechanical treatments of these pre-annealed samples were made and thermal, creep, tangent-modulus, and other mechanical properties are recorded. The experimental results show structural instability in the fibre morphology irrespective of the process histories.     

Mechanical properties of very thin cover slip glass disk

The biaxial flexural strength, Young’s modulus, Vicker’s microhardness and fracture toughness data for very thin, commercial, soda-lime-silica cover slip glass (diameter, D-18 mm, thickness, T-0.3 mm; T/D ≈ 0.02) are reported here. The ball on ring biaxial flexure tests were conducted at room temperature as a function of the support ring diameter (≈ 10–20 mm) and cross head speed (0.1–10 mm min⁻¹). In addition, the Weibull modulus data were also determined. The Young’s modulus data was measured using a linear variable differential transformer (LVDT) from biaxial flexure tests and was checked out to be comparable to the data obtained independently from the ultrasonic time of flight measurement using a 15 MHz transducer. The microhardness data was obtained for the applied load range of 0.1–20 N. The fracture toughnessK _IC data was obtained by the indentation technique at an applied load of 20 N.     

Development of nanotechnology for advancement and application in wound healing: a review

Wound healing is a series of different dynamic and complex phenomena. Many studies have been carried out based on the type and severity of wounds. However, to recover wounds faster there are no suitable drugs available, which are highly stable, less expensive as well as has no side effects. Nanomaterials have been proven to be the most promising agent for faster wound healing among all the other wound healing materials. This review briefly discusses the recent developments of wound healing by nanotechnology, their applicability and advantages. Nanomaterials have unique physicochemical, optical, and biological properties. Some of them can be directly applied for wound healing or some of them can be incorporated into scaffolds to create hydrogel matrix or nanocomposites, which promote wound healing through their antimicrobial, as well as selective anti‐ and pro‐inflammatory, and proangiogenic properties. Owing to their high surface area to volume ratio, nanomaterials have not only been used for drug delivery vectors but also can affect wound healing by influencing collagen deposition and realignment and provide approaches for skin tissue regeneration.Inspec keywords: skin, wounds, cellular biophysics, drug delivery systems, tissue engineering, hydrogels, nanocomposites, proteins, nanomedicineOther keywords: wound healing materials, nanomaterials, nanotechnology, proangiogenic properties, proinflammatory properties, collagen deposition, drug delivery vectors, skin tissue regeneration     

Far-Infrared Laser Stark Spectroscopy of CH3OD

The high resolution Stark spectra of the singly deuterated methanol isotope, CH₃OD, have been studied using the HCN laser with Stark fields up to approximately 60 000 V/cm. Numerous families of absorption lines have been observed in both parallel and perpendicular polarizations, resulting in the following assignments: with the 311 μm line – J _K = 18₁ ← 18₀ E ₂, υ _t = 1; and with the 337 μm line – J _k = 6₄ ← 5₃ E ₂, υ _t = 0 and J _K = 14₆ ← 13₅ A, υ _t = 1. Zero-field frequencies for the assigned transitions are in agreement with Fourier transform measurements and those calculated from the available molecular constants.     

Microstructure and mechanical properties of Al2O3 matrix nanocomposites produced by solid state precipitation

A novel and economical processing route for the production of Al₂O₃-based ceramic nanocomposites via solid solution–precipitation is reported. Dense (>98% ρ_th) and homogeneous solid solutions of 10 wt.% Fe₂O₃ in Al₂O₃ were produced by pressureless sintering at 1450 °C in air. Aging of the solid solutions in a reducing atmosphere at temperatures in the range 1250–1550 °C for different durations (up to 50 h) resulted in the precipitation of FeAl₂O₄ as second phase particles throughout the bulk of the samples. The optimum aging schedule resulted in a final microstructure comprising nano-sized (～100 nm) intragranular FeAl₂O₄ particles, along with coarser micro-sized particles on the matrix grain boundaries and triple point corners. Additionally, surface layers containing metallic Fe and with thicknesses up to ～100 μm were formed due to the further reduction of FeAl₂O₄. After removal of this surface layer, the hybrid nano/microcomposites possessed improved fracture toughness (by ～40%) and flexural strength (by ～50%) with respect to monolithic Al₂O₃.     

Backward Wave Oscillator Based THz Spectroscopy, Diatomic Formalism and Optically Pumped Lasers

In this paper the Backward Wave Oscillator (BWO) based spectroscopy technique and its application to molecular spectroscopy especially to diatomic molecules have been discussed. This is a new and electronically controlled technique with enormous capabilities most of which are yet to be exploited. This paper also presents a part of the culmination of the collective efforts in developing a cohesive and consolidated enunciation of the spectroscopic parameters and their relationship to effective molecular Hamiltonians for diatomic formalism, linear four- atomic formalism & quasi-linearity, Watson Hamiltonian and the complexities in symmetric and asymmetric top spectral structures and its relationship to optical pumping and / or interstellar space. All these considered together present a beautiful and consistent picture of molecular spectroscopy and THz Electromagnetic sources.