Unforeseen machine tool component failures cause considerable losses. This study presents a new approach to unsupervised machine component condition identification. It uses test cycle data of machine components in healthy and various faulty conditions for modelling. The novelty in the approach consists of the time series representation as features, the filtering of the features for statistical significance, and the use of this feature representation to train a clustering model. The benefit in the proposed approach is its small engineering effort, the potential for automation, the small amount of data necessary for training and updating the model, and the potential to distinguish between multiple known and unknown conditions. Online measurements on machines in unknown conditions are performed to predict the component condition with the aid of the trained model. The approach was exemplarily tested and verified on different healthy and faulty states of a grinding machine axis. For the accurate classification of the component condition, different clustering algorithms were evaluated and compared. The proposed solution demonstrated encouraging results as it accurately classified the component condition. It requires little data, is straightforward to implement and update, and is able to precisely differentiate minor differences of faults in test cycle time series.
Minimizing the machining cost of an individual cutting tool has become important for computer-based machining industry. This paper mathematically presents an Optimum Material Removal Control (OMRC ) Model,where the material removal rate ( MRR )i s comprehensively introduced,to accomplish the dynamic machining control and tool life determination of a cutting tool under an expected machining quantity. To resolve the incessant cutting-rate control problem,Calculus of Variations is implemented for the optimum solution. Additionally,the decision criteria for selecting the dynamic solution are suggested and the sensitivity analyses for key variables in the optimal solution are fully discussed. The versatility of this study is furthermore exemplified through a numerical illustration from the real-world industry with VISUAL BASIC. It is shown that the theoretical and simulated results are in good agreement. This study absolutely explores the very promising solution to dynamically organize the MRR in minimizing the machining cost of a cutting tool for the contemporary machining industry.
The rapid self-infiltration in the reactive Si/C, AgCuInTi braze/Si3N4, AI/TiC and other high-temperature systems indicates that dynamic contact angles could markedly influence the capillary invasion in these systems. In view of the scarcity of suitable models of the dynamic phenomenon for reactive systems, the classical models due to De Gennes, Joos, and Blake and Haynes for inert liquids were applied to the reactive capillary flows. An assessment of the model outcomes in light of published measurements on flow of Si through porous carbon points to their limitation in describing the reactive capillary flows. It is shown through analysis that the combined effect of an unstable contact angle and transitions in flow mechanisms (interface- versus diffusion-control) due to pore shrinkage (or expansion) can qualitatively explain the rather distinctive and abrupt drop in the flow velocity with increasing distance in the Si/C couples. The use of a scalar to represent the pore size distribution in real solids is, however, a major source of the discrepancy between theory and experiment.
We present a model to calculate the threshold ion bombarding energy required for overall rearrangement of target atoms in the ion-beam-enhanced deposition of carbon nitride films. This model describes the transient modification of the film-bonding configuration by successive individual ion impact events. Each ion impact is treated as a cylindrical thermal spike with a finite initial width, taking into account energy loss and energy dissipation processes. It is shown that the rearrangement of atoms during a cylindrical spike is the dominant mechanism leading to the formation of carbon nitride phase. The predicted characteristic energy range in which bombardment of the target atoms has at least one rearrangement is in good agreement with the experimental observation. The sp(3) bonding structure is dominant in carbon nitride films synthesized by ion-beam-enhanced deposition technique. It is suggested that one way to enhance the potential for formation of sp(3) configuration is to increase the thermal energy of target atoms to promote their rearrangement.
Control of flow progression to achieve a void-free mold filling is an important task in the resin transfer molding process. This paper presents an adaptive control method to control the flow front velocity by tracking a desired flow front location. The parameter estimation is used for on-line modeling. The input-output model of RTM makes use of lineal sensors for measuring the resin flow front. Several models of varying complexity are examined in this paper. The proper selection of model structure is important for the adaptive controller to achieve accurate tracking of the desired trajectory. Simulation results suggest that the control performance can be improved by selecting a proper model structure. Furthermore, it is found that nonlinear input-output models or the models with more undetermined parameters may not offer much advantage over simple linear models.
In Electro discharge machining the material removal is in the form of crater formed because of melting and evaporation of work piece over a localized area. The crater under single spark have been predicted by theoretical models adopting different approaches in solving the transient heat conduction equation considering suitable assumptions with appropriate initial and boundary conditions. In the present work, a transient thermal model for a very large solid cylinder has been used to predict the volume of the crater obtained under single spark by determining the melting isotherm both in axial and radial direction. The volume of the material within the melt isotherm corresponds to the material removed by a single spark. An analytical study of the effect of Plasma channel radius, Heat flux, Pulse duration and Thermal diffusivity on the shape of the crater has been made. Experiments are conducted in a commercial Electro discharge machine. The craters are measured under microscope and comparison with theoretical results is presented. Subsequently, the effect of plasma channel radius, the heat flux, pulse duration and thermal diffusivity on the crater volume has been explored. Finally a comparison of crater volume predicted by the present model for very large solid with the volume predicted in semi-infinite model has been made.
Phase decomposition characteristics of Bi12SiO20 and the transferability of decomposition-produced phases to Bi12SiO20 were investigated in detail. The major results are as follows. (1) The decomposition of Bi12SiO20 appears to be due to the stick contact between melt and Pt crucible where there are the combining effects of the liquid-phase separation in bismuth silicate melt and the chemisorption of Pt on the silica-rich melt. (2) The decomposition fraction increases with the melt temperature, the time kept above the critical liquid-phase separation temperature, the aging (or annealing) time [if the sample was aged (or annealed) at about 500degreesC without dispartment from the Pt crucible], and the specific interface between the melt and Pt surface, while it decreases with the cooling rate between 618degreesC and 500degreesC. (3) The types of decomposition-produced phases are dependent on the decomposed extent.
Single crystals Bi12TiO20 (BTO) with various sizes were successfully grown from the stoichiometric melt by a laser-heated floating zone method. The amount of inclusions of Bi4Ti3O12 and Bi2O3 is mainly dependent on the length of the molten zone if the temperature gradient in the grown crystal near the solid-liquid interface is large enough (e.g., about 320degreesC/mm). The transmittance and lattice constant of the produced crystals appear to be little affected by the growth rate if it is less than a critical value. The stoichiometric BTO crystal (grown at 1.0 mm/h) has a lattice constant of a = 10.17370(1) Angstrom. For a nonstoichiometric (Bi2O3 excess) crystal (grown at 1.0 mm/h),its lattice constant decreases [a = 10. 18372(9),- 0.00070189(6)X-TiO2 (Angstrom), where X-TiO2, is in mol%] and its transmittance increases with the concentration of TiO2.
Fiber reinforced polymer composites are highly susceptible to environmental conditions despite their favorable properties. Among various environmental factors, moisture absorption is known to have significant adverse effects on such materials. This work investigates the effects of accelerated moisture absorption on the mechanical properties of resin transfer molded glass/epoxy composites. 152.4 mm diameter disk-shaped parts are fabricated using EPON 815C resin and EPICURE 3282 curing agent. Reinforcement is provided by four layers of randomly oriented planar glass fiber preforms with 0.459 kg/m2 surface density, yielding approximately 21.2% fiber volume fraction. Samples cut from the molded disks are immersed into boiling water for accelerated aging. The masses of the specimens are measured at periodic intervals to quantity the amount of water absorbed. Tensile and short beam shear tests are performed at different levels of moisture absorption. Mechanical properties are found to decrease as moisture diffused into the material. Fiber pullouts on the surfaces of tested samples show fiber loosening as the cause of material weakening. To investigate the desorption and characteristics, part of the samples are dried at 65°C after the maximum moisture absorption is reached. Total stiffness recovery is observed after desorption but ultimate tensile strenth only recovered by 27.7%, which is 33.4% lower than the initial value.
Influence of strengths of a static magnetic. field and electro-conductivity of the enclosure wall was numerically studied for oscillatory natural convection of liquid metal in a cubical enclosure. Direction of the static magnetic field is horizontal and parallel to the vertical heated and opposing cold walls. Computations were carried out for Ra= 10(5), Pr = 0.025, Ha = 50, 200 and 1000, and for the ratio of electro-conductivity (that of wall versus that of fluid) Cm from zero to infinity.The average Nusselt number slightly increased at Ha = 50, and almost the same even with the increase in the Hartmann number for Cm = 0 and 10(-3). On the other hand, the average Nusselt number decreased extensively with the Hartmann number for Cm=0.1 to infinity.
We estimate the concentration dependence of the diffusion constant and specific heat in zeolite solution using molecular dynamics technique. The zeolite particles approach Short-range order in a dense region under microscopic interaction. The predicted diffusion constant is strongly dependent on the particle volume fraction. This dependence follows the Arrhenius expression, in which the activation energy is a function of particle concentration. We also calculate the specific heat due to the interaction of zeolite particles as a function of particle volume fraction.
Having first defined the constant helical angle as the angle between the cutting edge and the revolving axis of the cutter, this paper then presents design models for producing the helical cutting edge and helical groove of a revolving cutter with a circular-arc generator. The section profile and relative feed speed of the grinding wheel in the NC machining of the cutter are derived for a given speed of rotation. A revolving cutter with a circular-arc generator and an approximately constant angle between the helical cutting edge and the axis of the cutter may be obtained. A remedial grinding operation to eliminate the residual revolving surface is also presented. A series of ideal models of the NC machining of this type of revolving cutter are provided. This paper provides a valuable reference for the design and NC machining of this cutter type.
The effect of g-jitter, the modulation of the gravitational field in a microgravity environment such as Space Station, was numerically investigated for a three-dimensional rectangular cavity filled with liquid. Results showed that when the g-jitter field is perpendicular to the direction of the induced temperature gradient, the strength of the convective flow in the liquid is dependent on the frequency of the g-jitter field. However, when the g-jitter field is parallel to the temperature gradient, there was no effect on the flow field. This result has an important implication for crystal growth experiments in a microgravity environment: for a striations-free crystal growth, the furnace must be designed to maintain the temperature gradient parallel to the g-jitter field.
In order to explain the mechanism of material removal in electro discharge machining, various theoretical models based on transient heat conduction equation have been proposed by considering suitable assumptions and appropriate initial and boundary conditions. In this paper, the Laplace and Hankel integral transforms have been used in order to solve three dimensional transient heat conduction equation for an infinite solid subject to circular heat source. The computer program has been developed to compute the temperature distribution and the effect of heat flux, plasma channel radius, pulse duration on temperature distribution has been studied in order to study the nature of the crater formed under a single spark. Finally, a comparison has been made with the results of the semi infinite model.
The effects of base plate temperature and the initial concentration on the channel formation during the unidirectional solidification of ammonium chloride-water solution inside acylindrical test cell were investigated. Experiments to study the channel formation were carried out for 15%, 25%, 30% and 32% NH4Cl concentrations. For each concentration, the experiments were conducted at base plate temperatures of -21degreesC, -26degreesC and -38degreesC, respectively, The experimental results show that channels were formed during the solidification for all concentrations except at the 15% concentration. The channels formed during solidification were observed to be more pronounced and fewer in number with increasing concentration, The channels formed decreased in number with decreasing base plate temperature.
Modeling of 6H-SiC wafer heating during rapid thermal processing (RTP) based on incoherent radiation has been done using numerical methods. This model takes into account the spectrum of the incoherent radiation as well as a dependence of the absorption coefficient on the temperature and doping concentration of a wafer. The calculated curves of the temperature distribution at various parameters of the wafer and different conditions of the processing are discussed.
Knowledge of the flow front position of the injected fluid is essential for Liquid Composite Moulding (LCM) process development and optimisation. This paper presents two sensing techniques, Linear Direct Current (LDC) and ultrasound interface change, that deliver different types of information on the flow front position (continuous and punctual). Preliminary flow measurements were conducted to quantify the sensitivity of the considered monitoring techniques and to optimise the experimental set-up. Evaluation criteria include qualitative comparison of results delivered by visual, LDC and ultrasound monitoring systems with regard to position and shape of the flow front. The maximum deviations between visual and the investigated monitoring systems are Deltax(LDC) = 33.9 x 10(-3) m and respectively Deltax(US) = 2.8 x 10(-3) m. The second part of the paper presents permeability characterisation in the ID-flow channel based on flow front position delivered by LDC, ultrasound monitoring techniques and visual recording. The flow front position determined by conventional methods based on video capture is taken as reference. Comparison of the permeability values (K-visual, K-LDC and K-US) shows a maximum deviation of 6.93% given by the LDC-system. The ultrasound interface change measurement principle allows very accurate and reproducible punctual flow front tracking and shows a maximum deviation compared to the reference permeability (K-visual) of 3.32%. This study shows the potential of the investigated techniques for flow front monitoring of LCM injection processes.
The reduction of redundant deformation, and the forming load magnitudes can be largely effected by the design of the forming pass geometry. The new design concepts used in metal forming processes gave very good results that, on one hand, increased the processes efficiency and, on the other, improve the product quality. In response to that, one of these concepts has been adopted in this work to study its effect on the extrusion of Cans.The forward extrusion die has been designed and used to investigate the metal flow pattern and also to assess the forming load level, that in effect of the profile shapes for the piercing plug used in the process.The piercing plug profiles have been designed in accordance to the concept of constancy of the ratios of homogeneous strains (CRHS) that includes varying the rate of deformation flow, as accelerated, uniform and decelerated rates, and also with three values of the plug advances.Four extrusion reduction ratios of cross-sectional area have been used, that for pure lead billets which has been selected as a model material.The results have shown clearly the effect of the die geometry parameters on the level of the redundant deformation and consequently on the forming load magnitudes.
A methodology is developed and used to evaluate the response sensitivity of the thermal systems to variations in their design parameters. Techniques for computing the sensitivity of temperature distributions to changes in processing parameters needed for deciding the more effective laser input parameters for laser surface hardening treatment are considered. In this study, a state equation governing the heat flow in laser surface treatment is analyzed using a three-dimensional finite element method and sensitivity data of the processing parameter obtained using a direct differentiation method applied for sensitivity analysis. The interesting processing parameter is taken as the characteristic beam radius (r(b)) of the sensitivity of the temperature T versus r(b) and is analyzed for variation in other conditions. And these sensitivity results obtained in other parameters are fixed conditions.
Successful application of the shear forming method for production of large seamless cylinders can reduce production costs and increase the reliability of aerospace structural components through the reduction of material scrap and part count and the minimization of joints. The current research evaluates the applicability of shear forming to the Al-Cu-Nlg-Ag alloy C415, developed for airframe structure. The processing-microstructure-property relationships, are investigated for lab-scale shear formed C415 cylinders which had undergone various amounts of shear-forming strain. The grain structure, texture, and mechanical properties developed during and after shear forming are evaluated and compared with C415-T8 sheet. The cylinders exhibited a primarily recrystallized grain structure and weak texture. The grain size was fairly uniform through the thickness for low levels of shear-forming strain, However, at higher levels of strain, a bimodal grain size distribution developed. Room-temperature T8 yield and ultimate tensile strengths were comparable to C415-T8 sheet.
