Model of a Surface Flaw and Calculation of Topography of Its Magnetic Field for Tangential Magnetization by Alternating Magnetic Fields. Quasi-Stationary Case

A model of a surface flaw is proposed. The model describes topography of the magnetic field for tangential magnetization by an alternating magnetic field H at a frequency . It is shown that H can be represented in the form of two multipliers: one describes the dependence on the (X, Z) coordinates and the flaw parameters (the depth h and the opening width 2b) and the other describes the dependence on the electrophysical properties of the tested material in which the surface flaw is located (the specific conductivity and the relative magnetic permeability ). The computational model proposed makes it possible to describe the magnetic field topography ( = 0) reducing it to the quasi-stationary case and extend representations on the formation of magnetic fields induced by surface flaws with allowance of the magnetization frequency . The data on processing the experimental dependences in accordance with the proposed computational formulas give satisfactory results which confirm the validity of the computational model proposed in the study.     

Deterministic Friction Model of a Rough Surface Sliding Against a Flat Layered Surface

In this paper, a layered surface is modeled like a solid that has effective mechanical properties (E _eff(), _eff() and H _eff()) as a function of indentation depth () and the rough surface is modeled as a population of spherically shaped asperities with different radii and heights (not necessarily Gaussian distributed). The contact behavior and the resistant to motion experienced by each asperity is analyzed locally and summarized as the total friction force based on the adhesion and ploughing mechanisms. The present model extends the capability of Halling's model to predict friction of layered surfaces. With this model, one is able to predict the friction of soft layer on a hard substrate and hard layer on a soft substrate in contact with a rough counter surface.     

The Boundary Lubrication Properties of Model Esters

The friction of three chemically distinct esters was measured in order to determine how molecular architecture influences friction. The friction coefficients of mica surfaces separated by a thin film (<2 nm) of -chlorodecyl benzoate, -chlorodecyl pentafluoro benzoate, and -chlorodecyl perfluoro hexanoate were measured to be 0.15±0.015, 0.13±0.012, and 0.12±0.02, respectively. The friction coefficients for the esters are lower than the previously measured friction coefficients of simple hydrocarbon liquids such as n-tetradecane (=0.8), but are comparable to the friction coefficients of surfactant monolayer coated surfaces (=0.001–0.2). The results suggest that the ester molecules adsorb onto the mica surface with the (phenyl or hexyl) carbonyl next to the surface and the hydrocarbon tail pointing away from the surface. Hence, the friction is controlled by the packing density and properties of the hydrocarbon tail. Changes in the chemistry and structure of the carboxylic acid portion of the ester only give rise to small changes in the friction coefficient.     

Burr detection by using vision image

In this paper, a practical force model for the deburring process is first presented. It will be shown that the force model is more general than Kazerooni's model and it is suitable for both upcut and down-cut grinding. In terms of this force model, an algorithm of burr detection by using a 2D vision image is proposed. In the burr detection algorithm, the relevant data of burrs, such as frequency, cross-section area, and height are simplified so that they are functions of the burr contour only. Then, a fast tracking method of the burr contour (BCTM) is developed to obtain the contour data. Experiments show that the BCTM of this passive (i.e. without lighting) image system can be as fast as 18.2 Hz and its precision is 0.02 mm, so online burr detection and control by using the vision sensor is feasible.Nomenclature A _burr cross-section area of the burr - A _chamfer cross-section area of the chamfer - A _n proportional factor - A _work cross section area in the contact zone while deburringA _work=A _burr+A _chamfer - w cutting width - w _root thickness of the root of the burr - a depth of cut - a _root burr heighta _root=a(w _root) - C ₁ static cutting edge density - D equivalent wheel diameter - d _s wheel diameter - d _w workpiece diameterD=d _w d _s/(d _w±d _s)D=d _s andd _w for the deburring process - F _h horizontal grinding force - F _v vertical grinding force - F _n normal grinding force - F _t tangential grinding force - F _n(K) normal grinding force of the Kazerooni's model - F _t(K) tangential grinding force of the Kazerooni's model - F _o threshold thrust force - f _burr burr frequency - f _n normal grinding force per active grain - f _t tangential grinding force per active grain - f _r first resonant frequency of the robot - f _tool resonant frequency of the end-effector at the normal direction - exponential constant for describing the edge distribution = [(1 +n) + (1 –n)]/2 = (1 +n)/2 for = 0 [21] - K proportional factor of the force model of the grinding processK =A _n ^1–n / - K ₀ specific contact force per contact length - K ₁ specific chip formation force per contact length - V _s wheel speed - V _w workpiece speed - _w metal-removal parameter - K ₂ specific metal-removal parameter per wheel speedK ₂ = _w/V _s - K _c specific chip formation force per area - K _f specific friction force per area - k constant for the parabolic burr - k ₁,k ₂,k ₃,k ₄ constants for the circular burr - L contact width between the wheel and the workpieceL is equal to the chamfer's hypotenuse length, orL=w _root when there is no chamfer - l contact length - l _k contact length between the wheel and the workpiece - m exponential constant for describing the edge shape 0m1m=1 for the deburring process [21] - N _dyn number of engaged cutting edges per wheel surface - n exponential constant for describing the cutting process 0n1n=1 for the pure chip formation process andn=0 for the pure friction process [22] - average contact pressure - p exponential constant for describing the relationship between the static cutting edge and the wheel surface depth 1p2p=1 for linear case [21] - Q magnitude of the individual chip cross-section in the contact zone - r radius of the circular burr - Z _w metal-removal rate - ,, exponential constants for describing the edge distribution [21] = (p –m)/(p + 1) = 0 form = 1,p = 1 =p/(p) + 1 = 1/2 forp = 1 = (1 –n) = 1n/2 for = 1/2 - actual contact area between the wheel and the workpiece - coefficient of the sliding friction - variable of the contact angle - _k maximum contact angle - _m mean rotating angle - _t half of the tip angle of the grains - ratio of tangential chip formation force to the normal chip formation force. Usuihideji has pointed out that = /(4tan_t) [29]     

Measurements of the Thermal Diffusivity and Thermal Conductivity of Metals Near the Melting Point

A pulsed technique for measuring the thermal diffusivity a and thermal conductivity of spherical samples with an allowance for the spatial–time energy distribution over the laser-beam cross section is described. The measured temperature dependences () and () for solid and liquid tin near the melting point of samples are presented. The a and measurement accuracies are 5 and 15%, respectively.     

Automated Devices for the Testing of Mill Rolls

Multichannel -type devices developed at TsNIITMASh for the automated ultrasonic inspection of cylindrical objects, such as mill rolls, shafts of turbines and compressor units, circular welded joints of thick-walled shell rings, etc., are described. These devices feature from two to eight acoustoelectronic channels. Acoustic contact occurs through industrial water. The testing is performed under workshop conditions; the object being inspected is rotated by a turning lathe or any other handling mechanism. Sonication is simultaneously performed by piezoelectric transducers (PETs) with input angles of 0, 40, 50, 60, and 70° and also by surface and head waves in order to reveal surface and subsurface flaws. A wide-span eddy-current transducer of special design is also used for this purpose. All data are stored in flash memory and retrieved on a PC located in an office. The inspection results are displayed as C- and B-type scanning defectograms. Moreover, it is possible to obtain an isometric image of flaw zones. -type devices have been used for over one and a half years in two workshops at OAO Severstal'.     

The ВД-12НФП Eddy-Current Flaw Detector and Methods for Processing a Measured Signal Produced by a Flaw

The field of application, the features of operation, and the main performance characteristics of a -12 eddy-current flaw detector are considered. Methods of digital data processing for improving the recognition of flaw-produced signals against the background noise are presented.     

Feasibility of NDT of Ferromagnetic Steel Structures Based on Measurements of Residual Magnetization as a Function of Elastic Stress

Algorithms for estimating elastic stress in ferromagnetic steel structures are based on measurements of the residual magnetization M _r as a function of tensile and compressive stress ₀ after quenching and tempering at different temperatures T _tem. The suggested testing technique is highly sensitive because the range of M _r (₀) is fairly wide (for the interval 0.6_{y 0} –0.6_y, where _y is the yield limit, the range is 600–800 kA/m). The necessary condition for using this testing technique is the availability of calibration curves for the selected testing algorithm measured on samples of steels to be tested (i.e., of the same sort of steel tempered at the same temperature). All the testing algorithms suggested in the paper enable one to determine both the magnitude and sign of the stress in the material.     

Detection of the Increment of an Instantaneous Phase in a Long-Base Laser Meter of Small Vibrations

A phase meter for processing signals of a laser meter of small displacements and vibrations at long base distances is described. Vibrations of objects are transformed into small increments of a signal phase at an RF carrier, which are detected by the phase meter and are outputted as signals proportional to microvibrations in the acoustic range. At a given carrier frequency f _c = 10.7 MHz, vibrations are detected within a band f = 3 kHz. Such vibrations produce phase fluctuations of 10^–42, which correspond to magnitudes of 1 nm for a laser wavelength 10 m.     

Assessment of the Hazard Level (Depth) of Flaws Using a ВД-12НФМ Eddy Current Flaw Detector

The operation features and the main technical characteristics of the -12 eddy current flaw detector are considered. A method is proposed for testing complex-shaped parts with the use of holding attachments and a specialized transducer with a slanted sensitive element. The capabilities of the device in assessing the hazard level (depth) of a flaw are shown. The distinctive features of the -12 eddy current flaw detector are presented.     

Capacitive Discharge Excilamps

UV radiating sources on KrCl ( 222 nm), XeCl ( 308 nm), and XeBr ( 282 nm) molecules excited by a capacitive discharge are described. The sources have a simple design of the radiator and are characterized by a high radiation efficiency (up to 25%), a lifetime of up to 2500 h, and a radiation band half-width of 4–8 nm.     

A generalised model of milling forces

This paper presents the development of a generalised cutting force model for both end-milling and face-milling operations. The model specifies the interaction between workpiece and multiple cutter flutes by the convolution of cutting-edge geometry function with a train of impulses having the period equivalent to tooth spacing. Meanwhile, the effect of radial and axial depths of cut are represented by the modulation of the cutting-edge geometry function with a rectangular window function. This formulation leads to the development of an expression of end/face-milling forces in explicit terms of material properties, tool geometry, cutting parameters and process configuration. The explicitness of the resulting model provides a unique alternative to other studies in the literature commonly based on numerical integrations. The closed-form nature of the cutting force expression can facilitate the planning, optimisation, monitoring, and control of milling operations with complicated tool—work interactions. Experiments were performed over various cutting conditions and results are presented, in verification of the model fidelity, in both the angle and frequency domains.Notation * convolution operator - helix angle of an end mill - _A,_R axial and radial angles of a face mill - angular position of any cutting point in the cylindrical coordinate system - unit area impulse function - ^(i–1)(–T _o) (i–1)th derivative of (–T _o) with respect to - angular position of cutter in the negative Y-direction - _L, lead and inclination angles of a face mill - angular position of any cutting point in the negative Y-direction - ₁, ₂ entry and exit angles - upper limit of cutting edge function in terms of - as defined in equation (10) - A _xk ,A _yk ,A _zk kth harmonics of cutting forces in the X-, Y-, and Z-directions - d _a,d _r axial and radial depth of cut - dA instantaneous cut area - D diameter of cutter - f _o frequency of spindle - f _t,f _r,f _a local cutting forces in the tangential, radial, and axial directions - f _x ,f _y ,f _z local cutting forces in the X-, Y-, and Z-directions - F _x ,F _y ,F _z resultant cutting forces in the angle domain in the X-, Y-, and Z-directions - F as defined in equation (5) - h derivative of height function of cutting edge with respect to - h() height function of one cutting edge with respect to - H height of any cutting point - K _r,K _a radial-to-tangential and axial-to-tangential cutting force ratios - K _t tangential cutting pressure constant - K as defined in equation (6) - p as defined in equation (6) - N number of cutting edges - r() radius function of one cutting edge with respect to - R radius of any cutting point - T cutting engagement time function of any cutting point - T _o cutting engagement time of the cutting point at =0 - T th() tooth sequence function - t _c average cut thickness - t _x feed per tooth - W _A,W _W,W _C amplitude, width and centre of a window function - W(,) unit rectangular window function - y _min,y _max minimum and maximum positions of workpiece in the Y-direction - Z _min,Z _max integration limits in the Z-direction     

Time-of-Flight Characteristics of Scintillation Counters with Fine-Mesh Photomultipliers

The characteristics of the time-of-flight system of scintillation counters with the -527 and R5505 fine-mesh-dynode photomultipliers for high-magnetic-field environment were measured. Scintillation counters with thin plastic scintillators 1, 3, and 5 mm thick were designed to operate in comparatively strong stray magnetic fields of up to several kilogauss. The measurements were carried out in beams of the U-10 proton synchrotron (Institute of Theoretical and Experimental Physics) with proton, ⁺-meson, and ^–-meson momenta of 0.63, 1.03, and 1.28 GeV/c. For counters with scintillator sizes of 1 × 20 × 154 mm (BI-408) and 3 × 20 × 200 and 5 × 20 × 200 mm (Kuraray and SCSN-81), time resolutions of 45–180 ps were obtained. The time resolution of the scintillation counters, in which scintillators 20 mm thick and -527 photomultipliers were used, was found to be 50–80 ps.     

Fracture mechanics-based model of abrasive waterjet cutting for brittle materials

Advanced engineering ceramic materials such as silicon carbides and silicon nitride have been used in many engineering applications. The abrasive waterjet is becoming the most recent cutting technique of such materials because of its inherent advantages.In the present study, two elastic-plastic erosion models are adopted to develop an abrasive waterjet model for cutting brittle materials. As a result, two cutting models based on fracture mechanics are derived and introduced. The suggested models predict the maximum depth of cut of the target material as a function of the fracture toughness and hardness as well as the process parameters.It is found that both models predict the same depth of cut within a maximum of 11%, for the practical range of process parameters used in the present study. The maximum depth of cut predicted by the suggested models are compared with published experimental results for three types of ceramics. The effect of process parameters on the maximum depth of cut for a given ceramic material is also studied and compared with experimental work. The comparison reveals that there is a good agreement between the models' predictions and experimental results, where the difference between the predicted and experimental value of the maximum depth of cut is found to be an average value of 10%.Nomenclature C abrasive efficiency factor, see equation (16) - C ₁,C ₂ c ₁/4/3, c₂/4/3 - c ₁,c ₂ erosion models constants, see equations (1) and (2) - d _a local effective jet diameter - d _j nozzle diameter - d _S infinitesimal length along the kerf - f ₁ ( _E ) function defined by equation (7) - f ₂ ( _E ) function defined by equation (8) - f ₃ ( _e ) function defined by equation (14) - g ₁ ( _E ) f ₁( _e )/f ₃ ² ( _e ) - g ₂ ( _e ) f ₂( _e /f ₃ ² ( _e ) - H Vickers hardness of the target material - h maximum depth of cut - K _c fracture toughness of target material - k kerf constant - M linear removal rate, dh/dt - m mass of a single particle - abrasive mass flow rate - water mass flow rate - P water pressure - Q total material removal rate, see equation (11) - R abrasive to water mass flow rates - r particle radius - S kerf length - u traverse speed - V material volume removal rate (erosion rate) - V idealised volume removal by an individual abrasive particle - particle impact velocity - ₀ initial abrasive particle velocity - x,y kerf coordinates - local kerf angle, Fig. 1 - _E jet exit angle at the bottom of the workpiece, Fig. 1 - particle density - _w water density On leave from: Mechanical Engineering Department, Suez Canal University, Egypt.On leave from: Mechanical Power Engineering Department, Alexandria University, Egypt.     

A faster, more reliable solver of regular-grid TSPs: single value threshold accepting

The main point of this paper is to provide a simple and efficient threshold value for the threshold accepting (TA) algorithm to attempt an optimal solution for the regular grid travelling salesman problems (TSPs) in a reliable way. This new algorithm is named the single value threshold accepting algorithm (SVTA). The number of the threshold value is one and its value is: where g is the grid size and is the smallest integer not less than a real number x. For the regular-grid TSPs, g can be set as where n is the problem size. It is shown empirically, with 100 independent simulations performed with 441 cities, in 16 different cases, that the SVTA is far superior to (at least five times faster on average than) the previous double threshold accepting (DTA) with respect to the speed of finding a global optimal reliably. Particularly in the case of the 441 cities, the proposed algorithm is at least 21 times faster and rises up to 96 times on average and optimistically 284 times faster than the previous one. Important insight is provided that reveals how the formula works and why it works successfully.Notation ={} State space of the tours in TSP - L() The length of a tour - L_opt The optimal tour length - TH Threshold - g Grid size in a square regular-grid TSP - n Number of points in TSP - L Lid value of a "pocket" around a good suboptimal solution x_min - N(L) Volume (= number of tours) of the "pocket" around a good suboptimal solution x_min with lid value L - M(L) Number of local minimum in the pocket with lid value L - K(n) Number of experienced local minima in a simulation by the SVTA     

Analysis of the diamond sawing process

There are three methods in use for separating diamonds, i.e. by cleaving, by laser beam and by sawing. Sawing is one of the main methods used for this purpose. This operation is carried out on special sawing machines equipped with a sawing disk blade, 0.04–0.14 mm thick and 76 mm initial diameter. The rotational velocity (n) of the disk is between 6000 and 12 000 r.p.m. Diamond powder is embedded in the periphery of the disk. The outcome surface of a diamond after the sawing operation must be flat and smooth, Whenever such a surface is actually obtained, the polishing time and the loss in size and weight of the diamonds are reduced.In the present work, the positioning of the diamond to be sawed, with respect to an embedded particle in the disk, to create a favourable cutting angle is discussed. This would make it possible to reduce the rake angle () to near-zero, and thereby the cutting forces. Furthermore, a method to control the morphology and grain size of the diamond powder to be used in the cutting was developed.In the diamond industry, two modes of sawing operations are in practice. One uses the periphery of the disk for the sawing while the other employs a circular hole in the centre of the disk. Analysis of the two modes showed that the hole mode is more promising, as the design in that case requires tensioning of the disk and makes for better lateral stability during the sawing process. In addition the tangential and the radial stresses, developed in both sawing methods, were calculated. To support the above, data was obtained from existing literature and analysed.Nomenclature n rotational velocity of the disk, r.p.m. - rake angle, degrees - back clearance angle, degrees - cutting angle, degrees - m relative frequency - f feed - b disk radius, mm - a disk hole radius, mm - r current disk radiusb>r>a, mm - density of disk material, kg m^–3 - angular velocity - Poisson ratio of disk material - g acceleration of gravity, m s^–2 - _r radial stress, kg cm^–2 - _{r max} highest radial stress, kg cm^–2 - _t tangential stress, kg cm^–2 - tangential stress at outside circumference, kg cm^–2 - tangential stress at inside circumference, kg cm^–2     

Determining the Surface Electrostatic Potential Ψ s of a Dielectric-Bordering Semiconductor Using the Method of Ψ s "/Ψ s Diagrams

A quantitative approach to determining the integration constant _s0(V _{g 0}) in an expression relating the semiconductor surface potential _s to the voltage V _g applied to the metal–insulator–semiconductor (MIS) structure and its quasi-static capacitance–voltage characteristic C _v(V _g) (normalized to the dielectric capacitance) is described. The method is based on the analysis of experimental functions _s ^"( _s ), where _s ^" = d _s /dV _g, and the same functions calculated for an ideal MIS structure. The obtained function _s (V _g) is a rather exact and complete characteristic of electron properties of the MIS-structure phase boundary (the integrated interface state density, flat-band voltage V _FB, sign and density of the dielectric fixed charge, and variations of these parameters under the action of various factors). Using the example of a particular n-Si MIS structure, it is shown that the method of _s ^"/ _s diagrams ensures a noticeable (up to 0.93 eV) widening of the Si gap sounding region and observation (by the value of the V _FB shift) of very small ( 1 × 10⁷ cm^–2) variations in the charge density at the Si/SiO₂ phase boundary.     

Surface roughness measurements in finish turning

A new approach is proposed for the on-line measurement of the maximum peak-to-valley roughness,R _max, of a finished-turned surface in the feed direction. The method is based on solving the inverse problem of light scattering by using a linear least-square estimate of the angular scattered light pattern reflected from a surface. A laser system has been developed to capture the light reflected under different cutting conditions. The effects of the ambient room light as well as the workpiece's rotational speed and methods for thier compensation are also discussed. Good correlation was found between the optical and stylus-measuredR _max.Nomenclature R _max maximum peak-to-valley roughness within the sampling length - R _q RMS surface roughness within the sampling length - R _a arithmetically averaged roughness within the sampling length - _z r.m.s. surface height within the sampling length - u r.m.s. slope of the surface within the sampling length - T correlation distance of the surface, defined as the distance in which the correlation coefficient,C(), equals e^–1 - I(₁,) intensity of reflected light - I _m(₁,₂,) measured intensity of reflected light at instant - ₁ angle of incidence of laser beam - ₂ scattering angle defining a CCD pixel location (₁ and ₂ are measured with respect to the normal of the surface of the workpiece coincident with the centre of the laser beam) - v scattering vector of reflected light - _x,_z components ofv in thex andz direction, respectively - L sampling length associated with the laser spot on the surface of the workpiece - j representative location of a CCD pixel - j CCD pixel location corresponding to the mean light level - p _j density function of the light intensity of thejth pixel - wavelength of laser light - nose radius of the cutting tool - ASLP angular scattered light pattern - K correction factor for the measured light intensity - S _m standard deviation of the measured ASLP - S _c standard deviation of the ASLP calculated from an estimatedR _max - K control step size ofK - computational error, defined as =|S _m–S_c|/S _m - K _a,K_b starting and ending point, respectively, within the search range forK - K _c,K_d two points within (K _a,K_b), determined by the golden section search method - V cutting speed (m/min) - f feed rate (mm/rev) - d depth of cut (mm) - H hardness of workpiece (found on Rockwell scale C) - CCD charge-coupled device     

A Magnetometer Based on a Hall Probe

A magnetometer based on a 606117 Hall probe with residual field compensation and a sensitivity threshold of 10^–8 T Hz^–1/2 is described. A four-step algorithm of the residual field compensation is suggested. The algorithm allows the residual voltage to be reduced by a factor of 1200 and more. The magnetometer makes use of the analog switches series 590 and 1014.     

Drill and clamping interface in high-performance drilling

The behaviour of a drill and a clamping unit was investigated in high-performance drilling. Some clamping units were characterised experimentally. In a series of experiments, the free-rotating drill behaviour, and the drilling events were investigated under high-performance conditions. A non-rotating measurement system, including proper procedures for signal processing, enabled the presentation of all measured values in terms and coordinates of the rotating tool. This led to a better understanding of the first-contact event, the penetration and the full drilling phases, as well as the influence of the clamping unit under different cutting conditions.Notation F impulse test exciting force [N] - Fz drilling axial force [N] - F _x F _y drilling lateral force components [N] - F _T drilling table speed (mm min^–1) - L drill overhang - T drilling torque [Nm] - X, Y, Z world coordinates [mm] - X _T,Y _T,Z _T rotating tool coordinates [mm] - _L hole location error [mm] - drill diameter [mm] - rotating angle [°] - R drill end circular movement fadius in world coordinates [mm] - X, Y drill end deflection in world coordinates [mm] - X _T, Y _T drill end deflection in world coordinates [mm] =2R