Effect of plastic strain and aging of N36K10T3 Invar on the output of an applied eddy-current transducer

Eddy-current parametersf ₀ andx ₀ as functions of the plastic strain in the N36K10T3 Invar have been studied. It has been proven that parametersf ₀ andx ₀ decrease monotonically as the strain degree rises to ∈=50%. Higher temperatures and longer times of aging (annealing) of the strained Invar lead to higherf ₀ andx ₀, whereas no changes in the eddy-current parameters have been detected in the case of an unstrained (quenched) Invar. Feasibility of deriving the strain, the temperature, and duration of isothermal aging of strained Invars with fcc lattices from the eddy-current parametersf ₀ andx ₀ has been demonstrated.     

Eddy-Current Studies of Aging Processes in N26T3 Metastable Austenite Steel

In the N26T3 austenite steel, the eddy-current parameter f ₀ has been measured after one aging cycle at temperatures of 700 and 650°C, and after two aging cycles, one of them at the same temperature and the second at 600 and 550°C. The two-stage aging is conducted by two schemes: (1) preliminary aging at 700 or 650°C, transfer of samples without cooling to the room temperature into a furnace heated to 600 or 550°C, then isothermal aging and cooling to room temperature T _r; (2) the same operations as in the first scheme, but the samples are cooled to T _r after the preliminary aging. The eddy-current parameter f ₀ measured at T _r increases with time after aging at 700 and 600°C owing to isothermal martensite transformation. After the two-stage aging, the isothermal martensite transformation at T _r still takes place, but it is stabilized, i.e., the parameter f ₀ drops with time. The stabilization of the austenite is the more pronounced, the lower the temperature of the second stage of aging, and it is stronger after the two-stage aging by the second scheme.     

A Study of Cellular Decay in Austenite Alloys Using an Applied Eddy-Current Transducer

The eddy-current parameter f ₀ of the N36K10T3 invar has been studied in the range of aging temperatures from 600 to 900°C. The maximal drop in f ₀ has been observed at the temperature T _ag = 800°C, and the drop in this parameter was the larger, the longer the aging process. The drop in this parameter is caused by the cellular decay process in the solid solution, which depletes the austenite of nickel and titanium. The parameter f ₀ increases notably (from 4 to 46 kHz) when crystals of lowtemperature martensite (-phase) are generated in samples of the N26T3 steel with 100% cellular decay. This high value (f ₀ = 46 kHz) persists at T _ag < 400°C and drops by a factor of 4.5 over the interval 400 < T _ag < 600°C because the ferromagnetic -phase transforms to the paramagnetic phase-hardened austenite ( _ph). Aging of the phase-hardened austenite in the steel with cellular decay at T _ag = 700°C increases the parameter f ₀ by a factor of two (from 10 to 20 kHz) because the ferromagnetic -phase is generated when the aged phase-hardened austenite transforms to the martensite (_ph ) as a result of cooling the steel from the aging to room temperature.     

Effect of structure of aging metastable austenitic steels on the signal from an eddy-current transducer

Eddy-current parameterf ₀ of the N26T3 steel has been studied as a function of both the aging temperatureT _ag=20–800°C and the time τ of exposure to a constant temperature of 550 and 600°C up to 6h. In the initial state, the steel had two phases: (1) cooling-induced martensite+austenite (α+γ) or (2) strain-induced martensite+austenite (α′+γ). The parameterf ₀ drops monotonically as τ increases, and this drop is the faster, the higherT _ag. The parameterf ₀ changes nonmonotonically with the aging temperature. In addition to the initial two-phase structures, the one-phase γ structure has also been studied. The parameterf ₀ grows monotonically with the plastic cold strain and changes nonmonotonically with the aging temperature (20–800°C). Observed changes inf ₀ have been explained.     

光纤光梳温度反馈控制方法研究

为了解决光学频率梳长时锁定困难的问题,对光学频率梳重复频率（fr）与载波相位偏移频率（f0）的控制方法进行了改进。采用上、下两块半导体制冷片（TEC）对振荡器局部环境进行温度控制,并微调TEC温度将fr与f0漂移量分别稳定在10 Hz和600 Hz以内。利用锁相电路反馈控制有效腔长和泵浦光功率对fr与f0进行了精密锁定...     

A study on fatigue damage modeling using neural networks

Fatigue crack growth and life have been estimated based on established empirical equations. In this paper, an alternative method using artificial neural network (ANN) -based model developed to predict fatigue damages simultaneously. To learn and generalize the ANN, fatigue crack growth rate and life data were built up using in-plane bending fatigue test results. Single fracture mechanical parameter or nondestructive parameter can’t predict fatigue damage accurately but multiple fracture mechanical parameters or nondestructive parameters can. Existing fatigue damage modeling used this merit but limited real-time damage monitoring. Therefore, this study shows fatigue damage model using backpropagation neural networks on the basis of X-ray half breadth ratioB/B ₀ , fractal dimensionD _f and fracture mechanical parameters can estimate fatigue crack growth rateda/dN and cycle ratioN/N _f at the same time withinengineering limit error (5%).     

Weighting Factor in Calculation of Comprehensive Quality Index and Optimization of PVC Membrane Composition for Ion Selective Electrode

Abstract

The comprehensive quality index (CQI) method which is used in evaluating the response performance of an ion‐selective electrode has been presented recently. Under this strategy, a set of weighting factors (f _s , f _LR , f _LD , f _t ,) involving a numerical calculation of CQI is the key parameter, not only influencing the magnitude of CQI value, but also inducing a different conclusion on the optimization of composition for poly(vinyl chloride) (PVC)‐based sensing membranes, which was formulated with an electroactive substance, PVC, and plasticizer. In the present work, two techniques, multivariate regression and extremum analysis of a multiple function are used to study the optimization of the weighting factor. The best set of weighting factors obtained is as follows: f _s =0.38, f _LR =0.30, f _LD =0.20, f _t ,=0.10.     

Evaluation of fracture toughness degradation of CrMoV rotor steels based on ultrasonic nonlinearity measurements

The objective of this paper is to develop a nondestructive method for estimating the fracture toughness (K _IC) of CrMoV steels used as the rotor material of steam turbines in power plants. To achieve this objective, a number of CrMoV steel samples were heat-treated, and the fracture appearance transition temperature (FATT) was determined as a function of aging time. Nonlinear ultrasonics was employed as the theoretical basis to explain the harmonic generation in a damaged material, and the nonlinearity parameter of the second harmonic wave was the experimental measure used to be correlated to the fracture toughness of the rotor steel. The nondestructive procedure for estimating theK _IC consists of two steps. First, the correlations between the nonlinearity parameter and the FATT are sought. The FATT values are then used to estimateK _IC, using theK _IC versus excess temperature (i.e.,T-FATT) correlation that is available in the literature for CrMoV rotor steel.     

Dynamic thermoanalytical test method for qualifying brake lining materials

A thermoanalytical test method is described for qualifying brake lining materials, based upon the recording of coefficient of friction f versus temperature T diagrams. Tests are performed at a low sliding speed, thus avoiding substantial increase in temperature due to dissipation of frictional energy. During testing, the temperature in the friction interface of a brake lining-metal ring friction couple is increased linearly with time by means of time-controlled inductive heating of the metal ring. It is shown that the method yields a ‘fingerprint’ of the brake lining material, which is characteristic for its friction-temperature behaviour as related to composition and structure and which can thus be used for identification purposes and in acceptance testing. Repeated runs in the range T_o–T_max, performed at , yield information on the f−T behaviour of lining materials which, in previous runs, have been exposed to a maximum contact temperature T_max. The method is illustrated with results obtained with a resin/asbestos and a cermet/graphite material.     

The forced convection flow over a flat plate with finite length with a constant convective boundary condition

The flow of a fluid past a flat plate of finite length and infinite width (two-dimensional flow) is considered. The plate is heated by convection from a fluid with constant temperature T _f with a constant heat transfer coefficient h _f . In all previous works, the problem was considered using boundary layer theory whereas, in the present work, the solution is based on the full Navier-Stokes equations. The problem is investigated numerically with a finite volume method using the commercial code ANSYS FLUENT. The governing parameters are the Reynolds number, the new heat transfer parameter, and the Prandtl number. In addition, the influence of these three parameters on the temperature field is investigated. It is found that high Reynolds and high Prandtl numbers the wall temperature increases along the plate. They reach a maximum near the trailing edge then decrease. The same occurs as the heat transfer parameter increases. When the Reynolds and Prandtl numbers are low, the plate temperature tends to become symmetric, with a maximum at the middle of the plate. The temperature profiles become thicker as the Reynolds number and the Prandtl number is reduced while the temperature profiles become thicker as the heat transfer parameter increases.     

Bulk Modulus of Lubricating Oils as Predominant Factor Affecting Tractional Behavior in High-Pressure Elastohydrodynamic Contacts

The phase diagrams corresponding to transition from liquid to viscoelastic solid and that from viscoelastic solid to elastic-plastic solid of Santotrac100 (SN100), mineral oil, synthetic naphthenic oil, polybutene, and tetradecane were first made up by high-pressure density measurements and others. The bulk modulus of lubricating oils under a quasi-static condition was evaluated using a phase diagram. The results indicated that the bulk modulus of lubricating oils is closely related to the oil molecular packing parameter T _VE ?T (where T _VE is the viscoelastic solid transition temperature at pressure p, and T is the oil temperature). The constant values of the bulk modulus in the elastic-plastic range are different depending on the molecular structures of the oils. It has also been shown that SN100, mineral oil, synthetic naphthenic oil, and polybutene converted to amorphous solids at high pressures and tetradecane converted to molecular crystal. Next, the elastohydrodynamic lubrication tractions were measured by a ball-on-disk machine. The results indicated that the maximum traction coefficient is closely related to T _VE ?T. As a result, the importance of the bulk modulus as a predominant factor for traction characteristics of lubricating oil was pointed out.     

Study of ductile mode cutting in grooving of tungsten carbide with and without ultrasonic vibration assistance

In this study, ductile mode chip formation in conventional cutting and ultrasonic vibration assisted cutting of tungsten carbide workpiece material has been investigated through experimental grooving tests using CBN tools on a CNC lathe. The experimental results show that as the depth of cut was increased there was a transition from ductile mode to brittle mode chip formation in grooving both with and without ultrasonic vibration assistance. However, the critical value of the depth of cut for ductile mode cutting with ultrasonic vibration assistance was much larger than that without ultrasonic vibration assistance. The ratio of the volume of removed material to the volume of the machined groove, f _ab , was used to identify the ductile mode and brittle mode of chip formation in the grooving tests, in which f _ab <1 indicates ductile mode chip formation and f _ab >1 indicates brittle mode chip formation. For the same radius of tool cutting edge, the value of f _ab at the ductile-brittle transition region either with or without ultrasonic vibration was less than 1. However, the f _ab value with ultrasonic vibration assistance was close to 1. The experimental results demonstrate that ultrasonic vibration assisted cutting can be used to improve the ductile mode cutting performance of tungsten carbide work material.Nomenclature A amplitude - A ₁ , A ₂ cross-section areas of the ridge - A _V cross-section area of the groove - A _W the value of A _V subtracted by A ₁+A ₂ - f vibration frequency - f _ab ratio of work material removal - t time - v nominal cutting speed - v _u vibration velocity - v _t true cutting speed in ultrasonic cutting - angular frequency     

Features of Electromagnetic-to-Acoustic Conversion in Thermally Processed 30KhGSA Steel

The paper reports on an experimental investigation of EMAC parameters characterizing the 30KhGSA steel as functions of temperature in samples processed at various tempering temperatures T _tem. The EMAC efficiency varies with temperature in a different manner in samples processed at different tempering temperatures. The character of correlations among EMAC parameters as functions of T _tem remains largely the same over the temperature range between the room temperature and 200°C. Features of EMAC have been studied in the regions of domain wall displacement and domain rotation. We have found a parameter that is a derivative of the E-effect and correlates with the impact toughness.     

Effect of aging and plastic deformation on the mechanical,magnetic, and thermal properties of cobalt-containing invars

The mechanical, magnetic, and thermal properties of water-quenched (from 1150°C) alloys, such as H36K10T3, H36K10X5T2, and H36K5T2, which were strengthened by aging (at 650°C) and high-temperature deformation (1100–800°C) followed by aging, are studied. The decomposition of a supersaturated solid solution in the Invar alloys under study was shown to increase the strength properties and coercive force but to decrease the plasticity and saturation magnetization. In this case, the aging ambiguously affects thermal expansion coefficient α of the different alloys; the temperature range of invariance decreases. The plastic deformation of Invars was found to increase the ultimate strength, yield strength, and coercive force. The additional aging of deformed materials increases the strength and decreases the plastic properties; among the magnetic parameters, the saturation magnetization exhibits the most adequate correlation with the mechanical properties. The thermal properties (the α coefficient and invariance range) resulting from the complex heat treatment differ slightly from those resulting from the single aging.     

Alternative optimisation strategies and CAM software for multipass rough turning operations

The development of constrained optimisation analyses and strategies for selecting optimum cutting conditions in multipass rough turning operations based on minimum time per component criterion is outlined and discussed. It is shown that a combination of theoretical economic trends of single and multipass turning as well as numerical search methods are needed to arrive at the optimum solution. Numerical case studies supported the developed solution strategies and demonstrated the economic superiority of multipass strategies over single pass. Alternative approximate multipass optimisation strategies involving equal depth of cut per pass, single pass optimisation strategies and limited search techniques have also been developed and compared with the rigorous optimisation strategies. The approximate strategies have been shown to be useful, preferably for on-line applications such as canned cycles on CNC machine controllers, but recourse to the rigorous multipass strategies should be regarded as the reference for use in assessing alternative approximate strategies or for CAM support usage.Nomenclature d _i depth of cut for theith pass - d _opt optimum depth of cut - d _T total depth of cut to be removed - D _i workpiece diameter before theith pass - D _o,D _m initial and final workpiece diameter (afterm passes) - f _i feed for theith pass - f _max,f _min machine tool maximum and minimum feed - f _opt optimum cutting feed - f _sj, V_sj available feed and speed steps in a conventional machine tool - f _sgl, f_rec optimum and handbook recommended single pass cutting feeds - F _pmax maximum permissible cutting force - L workpiece length of cut - m continuous number of passes - m _H next higher integer number of passes from a givenm - m _HW upper limit to the optimum integer number of passesm _opt - m _L next lower integer number of passes from a givenm - m _LW lower limit to the optimum integer number of passesm _opt - m _o optimum (continuous) number of passes - m _opt optimum integer number of passes - N _a machine tool critical rotational speed whenP _a=P _max - N _max,N _min machine tool maximum and minimum rotational speed - n,n ₁,n ₂,K speed, feed and depth of cut exponents and constant in the extended Taylor's tool-life equation - P _a,P _max machine tool low speed and maximum power constraints - T _i tool-life using the cutting conditions for theith pass - T _L loading and unloading time per component - T _R tool replacement time - T _s tool resetting time per pass - T _T production time per component - T _TDi multi-passT _T equation with workpiece diameter effect - T _TDm, T_TDo multi-passT _T equations with constant diameterD _m andD _o, respectively - T _Topt overall optimum time per component - T _Tsgl optimum time per component for single pass turning - T _{T2re c} handbook recommended time per component - V _i cutting speed for theith pass - V _max,V _min machine tool maximum and minimum cutting speed - V _sgl,V _rec optimum and handbook recommended single pass cutting speeds - V _opt optimum cutting speed - a, E, W empirical constants in theP _a/F _pmax/P _max equations - , , feed, depth and speed exponents inF _pmax andP _max equations     

Confidence intervals in Cavalieri sampling

The aim of this study is to derive a formula that allows the prediction, from a Cavalieri data sample, of an appropriate confidence interval for a parameter Q. Two different approaches are used to address the problem. The first approach is to investigate whether the asymptotic distribution of the Cavalieri estimator exists when the sampling period T tends to zero. In particular, the distribution of the standardized version of the Cavalieri estimator z_T is analysed for a measurement function f whose smoothness constant is an integer number m. The analysis reveals that when the first noncontinuous derivative of f, f^(m), exhibits a unique discontinuity, the asymptotic distribution of z_T exists and it has a bounded support. An analytical expression of the distribution is derived for the cases m = 0 and 1. However, when f^(m) has two or more discontinuities, the asymptotic distribution of z_T does not exist and its support may be unbounded. In the second approach, a generalized version of the refined Euler Mac‐Laurin summation formula, valid for measurement functions with a fractional, rather than just an integer, smoothness constant, is applied to the Cavalieri estimator. As a result, a formula that predicts a lower and upper bound for the true parameter is derived for small T. This bound prediction formula is applied to Cavalieri data samples of human cerebral cortex. In particular, for sample sizes n = 8, 12 and 16, the true volume of cerebral cortex is bounded by relative distances 8%, 4% and 2% of the Cavalieri estimate, respectively.     

Prediction of tool failure rate in turning hardened steels

This paper presents a stochastic model for predicting the tool failure rate in turning hardened steel with ceramic tools. This model is based on the assumption that gradual wear, chemical wear, and premature failure (i.e. chipping and breakage) are the main causes of ending the tool life. A statistical distribution is assumed for each cause of tool failure. General equations for representing tool-life distribution, reliability function, and failure rate are then derived. The assumed distributions are then verified experimentally. From the experimental results, the coefficients of these equations are determined. Further, the rate of failure is used as a characteristic signature for qualitative performance evaluation. The results obtained show that the predicted rate of ceramic tool failure is 20% (in the first few seconds of machining) and it increases with an increase in cutting speeds. These results indicate that there will always be a risk that the tool will fail at a very early stage of cutting. Such a possibility should not be overlooked when developing proper tool replacement strategies. Finally, the results also give the tool manufacturers information which can be used to modify the quality control procedures in order to broaden the use of ceramic tools.Nomenclature c constant - ch chamfer width of the tool, mm - d depth of cut, mm - h _i hardness value at theith location on the workpiece during machining - h mean ofh ₁,h ₂,h ₃, ...,h _nn - n hardness mean location - m Meyer exponent determined experimentally to define the nonlinear relation between the cutting force and the ratioh _i/h - f feedrate, mm rev^–1 - f(t) probability density function of tool failure - f ₁(t) probability density function of tool failure due to breakage caused by tool quality - f ₂(t) probability density function of tool failure due to breakage caused by workpiece condition - f ₃(t) probability density function of tool failure due to tool chipping caused by chemical wear - f ₄(t) probability density function of tool failure due to flank wear - f ₅(t) probability density function of tool failure due to crater wear - O() error - t cutting time, min - x ₁,x ₂,...,x _n independent variables - A _i instantaneous area of contact between the tool and the workpiece - C ₁ chip load, which can be determined as a function of the cutting conditions and tool geometry - K _I crater wear index - K _T maximum depth of crater wear on tool face, mm - K _M crater centre distance, mm - N number of failures - P(t) probability function of tool failure - P _j(t) corresponding probability of failure, such that 1j5 - R tool nose radius, mm - R(t) reliability function - R _j(t) corresponding reliability function, such that 1j5 - T _V estimate of tool life for a set value of average flank wear (V _B ^* ) - T _K estimate of tool life for a set value of maximum depth of crater wear (K _T ^* ) - V cutting speed, m/min - V _B average tool wear, mm - Z(t) instantaneous failure rate or hazard function - ₃ shape parameter in the Weibull probability density function - rake angle - ₃ scale parameter in the Weibull probability density function, min - failure rate of the cutting tool - mean of a logarithmic normal distribution function - standard deviation of a logarithmic normal distribution function - tool wear function - time corresponding to the occurrence of tool failure - (.) standard logarithmic normal distribution function     

A study of the cutting modes in the grooving of tungsten carbide

In this paper, the cutting modes for grooving a tungsten carbide work material are investigated and presented. The grooving tests were carried out on an inclined workpiece surface using a solid CBN tool on a CNC lathe. The experimental results indicated that there was a transition from a ductile mode cutting to a brittle mode cutting in the grooving of tungsten carbide workpiece material as the depth of cut was increased from zero to a critical value. Ductile mode cutting is identified by the machined workpiece surface texture and the material removal ratio f _ab -ratio of the average of the volume of material removed to the volume of the machined groove. Scanning electron microscopy (SEM) observations on the machined workpiece surfaces indicated that there are three cutting modes in the grooving of tungsten carbide as the depth of cut increased: a ductile mode, a semi-brittle mode and a brittle mode. The ductile cutting mode depends on the stress in the cutting region, i.e., whether or not the shear stress in the chip formation region is greater than the critical shear stress for the chip formation ( _slip > _c ), and whether or not the fracture toughness of the work material is larger than the stress intensity factor (K ₁<K _c ). When ( _slip < _c ) and (K₁>K _c ), crack propagation dominates, the chip formation and the cutting mode are brittle.Nomenclature A ₁ , A ₂ A cross-section areas of the ridge - A _V A cross-section area of the groove - A _W The value of A _V subtracted by A ₁+A ₂ - F _X The horizontal force - F _Z The vertical force - K _C The fracture toughness - K _I The stress intensity factor - f _ab The work material removal ratio - f _n The normal cutting force - f _t The tangential cutting force - The inclined angle - _c The critical shear stress for dislocation - _slip The shear stress in chip formation zone     

A Study of the Influence of Superimposed Low-Frequency Modulation on the Drilling Process

A preliminary investigation of the effects of low-frequency modulation of the force in drilling has been completed. Important changes occur in the drilling of aluminum with the imposition of modulation at frequencies below 200 Hz. The effects depend on the amplitude of the modulation and the relationship of the frequency of modulation f_p to the frequency of rotation of the drill f_d. When f_p/f_d is an even integer, the modulation introduces no significant effects in the force, torque, or chip morphology. When f_p/f_d is an odd integer, the average drilling force decreases, and a large dynamic component of force and torque is seen with a frequency dependence f_p. For peak-to-peak amplitudes of vibration that are greater than one-half of the drill feed/rev, the chips are broken. A simple explanation of these effects is provided.     

Experiments and theoretical approaches on the burning behaviors of single n-heptane droplet

This study was conducted to improve the theoretical prediction of the burning characteristics of an n-heptane droplet by comparing them with experimental results. To achieve this, numerical approaches were conducted by assuming that the droplet combustion can be described by both quasi-steady behavior for the region between the droplet surface and the flame interface, and transient behavior for the region between the flame interface and ambient surrounding. Comparisons were considered for droplet diameter (d _t ), flame diameter (d _f ), flame standoff ratio (FSR), and viscous drag induced fluxes which are Stefan flux and thermophoretic flux for various initial droplet diameter (d ₀ ) and oxygen (O ₂ ) concentration conditions. It was revealed that the flame diameter (d _f ) and flame standoff ratio (FSR) initially increase dramatically and approach quasi-steady behavior within the observation period, and the flame standoff ratio (FSR) increases a little with the initial droplet diameter (d ₀ ) both experimentally and theoretically. The value of flame diameter (d _f ) decreases from its maximum value when oxygen (O ₂ ) concentration is increased from a value of 18% to 40%. The burning rate (K) constant becomes higher as the oxygen (O ₂ ) concentration increases since the increase of oxygen (O ₂ ) concentration produces a higher maximum flame temperature (d _f ) which enhances the effective thermo-physical properties of the gas-phase bounded by droplet and flame front.