Ultrasound Measurement of Two-Filler Concentrations in Polypropylene Compounds. Part 2: On-Line Calibration

An ultrasound system capable of measuring the concentration levels of two fillers, glass fibres and mica flakes, in polypropylene blends during extrusion compounding, has been successfully developed. The system is capable of operating under harsh conditions of the extruder settings while efficiently measuring the acoustic properties of the polymer melt. The attenuation and time-of-flight measurements of 1 MHz ultrasound waves propagating continuously through the polymer stream, prior to exiting the extrusion die, are used to characterise the morphology of the polymer blend and to determine the relative concentrations of blend additives. Prior work on the static calibration of the ultrasound set-up (Part 1) has been used to evaluate the real-time performance of the system. The ultrasound measurements showed a good match with the laboratory analysis. ID="A2"Correspondance and offprint requests to: Dr N. H.Abu-Zahra, Industrial and Manufacturing Engineering Department, University of Wisconsin-Milwaukee, PO Box 784, Wisconsin, WI 53201, USA. E-mail:nidal@uwm.edu     

Polishing of Ultra-clean Inner Surfaces Using Magnetic Force

In this study, an internal polishing system using magnetic force was developed for the production of ultra-clean tubes with average surface roughness ranging from 0.02 _m to 0.05 _m or less, and the application of magnetic abrasives composed of WC/Co powder was developed. After finding the optimal conditions, machining characteristics using newly developed abrasives ware analysed. From the results obtained by the experimental design method, optimal polishing conditions were analysed.     

Grinding of Aluminium-Based Metal Matrix Composites Reinforced with Al2O3 or SiC Particles

This paper presents results obtained from the grinding of aluminium-based metal matrix composites reinforced with either aluminium oxide (Al2O3) or silicon carbide (SiC) particles using grinding wheels made of SiC in a vitrified matrix or diamond in a resin-bonded matrix. The study used grinding speeds of 1100–2200 m min^-1 , a grinding depth of 15 _m for rough grinding and 0.1–1 _m for fine grinding, a crossfeed of 3 mm and 1 mm for rough and fine grinding, respectively,while maintaining a constant table feedrate of 20.8 m min ^-1 . Surface integrity of the ground surfaces and subsurfaces was analysed using a scanning electron microscope and a profilometer. Grinding using a 3000-grit diamond wheel at depths of cut of 1 _m and 0.5 _m produced ductile streaks on the Al2O3 particles and the SiC particles, respectively. There was almost no subsurface damage except for rare cracked particles when fine grinding with the diamond wheel.     

Economic-Statistical Design of Multivariate Control Charts Using Quality Loss Function

When a control chart is applied to monitor a production process, three test parameters should be determined: the sample size, the sampling interval between successive samples, and the control limits or critical region of the chart. In this paper, we develop the procedure to carry out the economic-statistical design of multivariate control charts by using a quality loss function for monitoring the process mean vector and covariance matrix simultaneously; i.e., to determine economically the optimum values of the three test parameters so that the statistical constraints (including the requirements of type I error probability and power) of the control chart can be satisfied. The test statistic _2_nL is used to develop this procedure and the cost model is established based on the cost function developed by Montgomery and Klatt and the multivariate quality loss function presented by Kapur and Cho. A numerical example is provided to illustrate the solution procedure of the design and then the effects of cost parameters on the optimal design are studied. ID="A1"Correspondance and offprint requests to: Dr Chao-Yu Chou, Department of Industrial Engineering and Management, National Yunlin University of Science and Technology, Touliu 640, Taiwan. E-mail: choucy@pine.yuntech.edu.tw     

Note: Piezoelectric polymers as transducers for the ultrasonic-reflection method and the application in mechanical property-screening of coatings

In the last years, non-destructive ultrasonic testing methods are more and more frequently employed in order to investigate the drying and curing processes of different coatings. Among them an ultrasonic reflection method was developed allowing the simultaneous measurement with longitudinal and transversal waves. In order to generate the ultrasonic pulse, piezoelectric ceramics or oxides are usually used as transducer materials which are connected to a delay line. Here, we demonstrate a similar approach for the ultrasonic reflection method installing piezoelectric polymers as ultrasonic transducer materials. In detail, poly(vinylidene fluoride and trifluoroethylene) [P(VDF-TrFE)] copolymers were prepared as piezoelectric transducer layers directly onto the metallization of glass delay lines avoiding additional bonding processes. The film preparation was carried out by solvent casting the polymer onto an area with a diameter of 12 mm and is optimized so that relatively homogeneous polymer layers with thicknesses between 14 and 35 μm are adjusted by the deposited amount of the polymer. Electrical poling renders the polymer piezoelectric. The ultrasonic properties of the P(VDF-TrFE) transducer and their usability for the ultrasonic reflection method are described also in comparison to previous measurements using LiNbO(3) transducer.     

A Strategic Decision Model for the Justification of Technology Selection

In this paper a new approach to the decision making on technology selection is proposed. In this approach a strategic decision-making model is used in which the tangible benefits of a technology are evaluated by addressing both cost and time dimensions, and the intangible benefits are evaluate d using the analytical hierarchy process (AHP). In AHP, experts in the functional area give judgemental values required for the comparison matrices. However, the opinions of the experts may deviate, and also a single estimate is not realistic, hence, in this approach of evaluating alternative technology, a range of judgemental values are taken and three different levels are considered in the range. The change in the preference level of the alternatives with the change in objective factor weightage ( _), and the range of _ at which the transition in the choice of technology takes place, are analysed, which assists the decision maker. ID="A1"Correspondance and offprint requests to: Dr M. Punniyamoorthy, Department of Management Studies, Regional Engineering College, Tiruchirrapalli 620015, Tamil Nadu, India. E-mail: puniya@rect.ernet.in     

Measuring melt density in polymer extrusion processes using shear ultrasound waves

Ultrasound shear waves propagating at a frequency of 2.25 MHz are used to measure the density of polymer melt in real time during extrusion process. The acoustic impedance of the polymer melt is calculated using the measured reflection coefficient off the polymer melt interface boundary. A normalisation procedure was developed to normalise for the effect of other process and material parameters not pertinent to the melt density. The ultrasound measurement is independent of the attenuation in the polymer melt and the thickness of the melt stream, which makes this technique highly desirable for heavily loaded polymers and large extrusion dies. The system was evaluated using polyvinyl chloride compounds containing various levels of foaming agent and process aid at fixed processing conditions. The system measurements of the melt density are compared to the weight of the extrudate measured by a laboratory scale. The correlation coefficient between the two measurements is approximately 96%.     

Tool Chatter Monitoring in Turning Operations Using Wavelet Analysis of Ultrasound Waves

This paper presents a new method for tool chatter monitoring using the wavelet analysis of ultrasound waves. Ultrasound waves are pulsed through the cutting tool towards the nose and are reflected back off the cutting edge. Fluctuating states of contact and non-contact between the tool insert and the workpiece, which are generated as a result of tool chatter, affect the amount of the transmitted ultrasound energy into the workpiece material and, in turn, the amount of the reflected energy. The change in the energy of the echo signals can be related directly to the severity and frequency of tool chatter. Wavelet packet analysis was used to filter the ultrasound signals. A three-layer multilayer perceptron (MLP) artificial neural network (ANN) was used to correlate the response of the ultrasound sensor to the accelerometer measurement of tool chatter. The main advantage of the ultrasound sensor is its ability to monitor other parameters such as the first contact of the tool and workpiece tool chipping and flank gradual tool wear. Experimental results show that the severity of tool chatter can be successfully monitored using the proposed ultrasound system. The system response to various frequency levels of tool chatter was investigated, however, the measurement of the chatter frequency is beyond the system capability at the current time.     

Imaging Coral II: Using Ultrasound to Image Coral Skeleton

We report on imaging of coral skeletal densities using pulse-echo ultrasound. Focused ultrasound transducers with frequencies ranging from 1 to 5 MHz were used to image coral skeletal samples. Each transducer was scanned over the surface of a coral and the reflected signal from the coral was recorded. Post-processing of the ultrasound signal was used to generate images of the acoustic impedance of the coral—a quantity that is related to the density of the coral. The ultrasound images were qualitatively consistent with X-ray images of the coral samples—X-ray absorption is also related to coral density. Both images showed a banding structure related to the annual growth cycle of the coral. The results indicate that ultrasound can be used for nondestructive imaging of coral skeletal structure. The ultimate goal would be an in situ system for quantitatively measuring skeletal densities of live corals underwater. The skeletal density of several massive reef coral species is strongly correlated with ocean temperature. A time series reconstructions of the skeletal density of long lived specimens would provide a history of surface ocean temperatures over time periods extending over several centuries, far beyond the available instrumental record.     

基于激光测振仪的兰姆波离面和面内位移检测

激励模态和频响特性是超声导波传感器性能评估的两个重要指标,而传统的传感器,如压电传感器和电磁声传感器(Electromagnetic acoustic transducer,EMAT)等,受自身带宽和模态选择性的影响,无法有效地实现这两个参数的评估。激光测振仪可以测量结构中弹性波原始的离面和面内位移,且测量不受带宽的限制,因而是进行超声导波传感器激励模态测定和频响特性测量的理想方法之一。采用此种方法对一种周向一致激励兰姆波的EMAT进行测试,结果表明,此传感器在150～210 kHz的范围内能激励产生出单一S0模态兰姆波,在50～150 kHz范围内,A0模态与S0模态共存。利用激光测振仪检测离面和面内位移的方法,是进行传感器评估和兰姆波接收的有效方法,在超声导波的非接触测量、高温波导体检测及弹性波传播3D可视化方面也有广阔的应用前景。     

The use of geometrical acoustics for the solution of visualization problems

Recently, antenna arrays with computer processing of acoustic signals with subsequent visualization of a test zone have been widely used in the control of ultrasound waves. The authors present the results of studies on the determination of the trajectory of ultrasound from a piezoelectric transducer to the chosen point of a test zone using analytical and numerical methods of calculation, both for linear and matrix antenna arrays. Based on the obtained equations, the results of the reconstruction of the test zone, comparison of productivity, and recommendations on their use are given.     

AC conduction mechanism and battery discharge characteristics of (PVC/PEO) polyblend films complexed with potassium chloride

New K⁺ ion-conducting polymer blend electrolyte films based on amorphous polymer poly(vinyl chloride) (PVC) and semicrystalline polymer poly(ethylene oxide) (PEO) complexed with KCl salt were prepared using a solution-cast technique. The maximum value of ionic conductivity of a PVC/PEO:KCl (42.5:42.5:15) system is 8.29 × 10⁻⁶ S/cm at 303 K. The absorption edge was found at 4.30 eV for undoped film, while it was observed at 4.03 and 3.93 eV for 10 and 15 wt% KCl doped films, respectively. The direct band gaps for these pure and salt doped PVC/PEO films were found to 4.10, 3.86 and 3.74 eV, respectively, whereas the indirect band gaps were determined as 4.15, 3.72 and 3.64 eV. Transference number values showed that the charge transport in this electrolyte system is predominantly due to ions (t_ion = 0.97). The discharge capacity for PVC/PEO:KCl (42.5:42.5:15) polymer blend electrolyte system is 11 μA/h.     

矩形超声换能器空间脉冲响应计算方法研究

空间脉冲响应模型是一种可以高速、精确地计算平面型超声换能器瞬态声场的方法,该方法不需要对平面型探头的表面进行离散化或近轴近似处理。首先将空间点投影到换能器平面内,将构建空间脉冲响应函数转化为计算以该投影点为圆心,与换能器相交的圆弧段的圆心角。由于矩形换能器包括4个顶点和4条边线,其几何形状与圆形换能器相比较为特殊,所以当投影点位于平面内的不同位置时,其计算方法也不相同。首先将探头所在平面进行分区,当投影点位于同一分区中时,其空间脉冲响应函数的计算方法相同;然后给出了当投影点位于各个分区中时的空间脉冲响应函数的计算过程,分析了矩形换能器尺寸的变化对分区的影响;最后,对一维超声相控阵探头的瞬态辐射声场进行了计算实验,并采用动态光弹方法对瞬态声场进行观测实验。实验结果表明,不同的换能器尺寸对计算过程及结果有显著影响,本文计算方法可以有效地实现矩形超声波探头在均匀单一介质中的瞬态声场仿真计算,有利于对平面矩形类超声换能器进行优化设计。     

An experimental study of the acousto-elastic effect in a rolled plate of steel

The acousto-elastic effect in rolled steel is studied experimentally by transmitting ultrasonic transverse waves and measuring amplitudes of reflected echoes. A Y-cut quartz transducer with a frequency 4.8 MH_z and ultrasonic flaw detection equipment are used for generation and detection of waves, and three tensile specimens with different orientations are prepared from a rolled plate so as to ascertain an important role of its slight orthotropy. At first the variation of amplitude with the transducer direction is examined in the unstressed state, and the slight orthotropy of each specimen is determined quantitatively. Then the variation of amplitude with the tensile stress is examined in the elastic range. The results depend clearly on the orientation of each specimen, and rotation of polarization direction is affirmed in the specimen with an inclination 45° against the rolling direction. Quantitative discussions about the whole experimental results give the conclusion that the acousto elastic effect in this rolled plate obeys the relations which were proposed theoretically by one of the authors.     

Estimation of the equivalent complex modulus of laminated glass beams and its application to sound transmission loss prediction

The complex modulus E(jω) characterizes the visco-elastic behavior of a material. Using a system identification approach, this modulus can be measured via broadband modal analysis experiments. The technique is applied to determine the equivalent complex modulus E(jω), with its uncertainty bound, of multilayer glass beams from transversal vibration experiments in free-free boundary conditions. This property is related to the effective complex bending stiffness of the laminated glass specimen, and is further used for predicting the sound transmission loss of a multilayer plate. The data are rationalized in the terms of the linear visco-elastic properties of the polymer interlayer.     

Improved dielectric constant of thermoplastic blend as a function of alumina loading

Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al₂O₃ into the polymer matrix using solution blending. The modified blends were characterized by X-ray diffraction, Thermogravimetric analysis, and Scanning electron microscopy. The crystalline to amorphous phase variation was confirmed by XRD with increase in the interplanar distance (d). TGA results indicate that the thermal stability of the modified blend was significantly improved as a function of alumina loading which may be due to interfacial interaction between the alumina particles and the polymers. Scanning electron microscopy studies reveal the presence of alumina particles resulting in plane surface morphology. The modified blends show very high dielectric constant value (10⁵–10⁷) as a function of frequency (in the range 50 Hz–35 MHz) and temperature in the range (40–150 °C). The modified polymer blend demonstrate consistent polarization across the frequency band 50 Hz–10 kHz. The neutral aggregates formation due to higher concentration of alumina loading demonstrated an influence on AC conductivity. This investigation can be feasible for electronic and electrical engineering application as the dielectric medium.     

The effect of oxygen and carbon dioxide concentration on soot formation in nonpremixed flames using time resolved LII technique

The influence of oxygen concentration and CO₂ as diluent in oxidizer side on soot characteristics was studied by Laser Induced Incandescence, Time Resolved LII and Transmission Electron Microscopy photography in non-premixed coflowing flames. Through the comparison of TEM photographs and the decay rate of LII signal, suitable two delay times of TIRE-LII method and signal sensitivity (ΔS TIRE - LII /Δ) were determined. The effects of O₂ and CO₂ as diluent in oxidizer side on soot formation are investigated with these calibrated techniques. The O₂+CO₂, N₂, and [Ar+CO₂] mixture in co-flow were used to isolate CO₂ effects systematically. The number concentration of primary particle and soot volume fraction abruptly decrease by the addition of CO₂ to the co-flow. This suppression is resulted from the short residence time in inception region because of the late nucleation and the decrease of surface growth distance by the low flame temperature due to the higher thermal capacity and the chemical change of CO₂ including thermal dissociation. As the oxygen concentration increases, the number concentration of soot particles at the inception region increases and thus this increase of nucleation enhances the growth of soot particle.     

Dynamic friction measurements with an atomic force microscope on polymer surfaces

The combination of scanning friction force microscopy (SFFM) and lock‐in techniques leads to dynamic SFFM (DSFFM) and provides great advantages in friction force studies with sub‐micrometre resolution. In this paper are presented measurements on thin adsorbed organic films on polymers (polymer blend of 75% poly(allylaminehydrochloride) (PAA) and 25% poly(diallyl‐dimethylammonium chloride) (PDDAC)) and on mica (as a reference). The amplitude and phase response as a function of the excitation amplitude can be explained on hard surfaces by a simple static and dynamic friction model. This model allows us further to distinguish static friction forces and kinetic friction forces in a quantitative way. Furthermore, we demonstrate the use of these spectra to determine the correct modulation amplitude of the excitation to achieve the optimal friction contrasts directly. Polymer data suggest that the viscoelastic shear flow under the atomic force microscope (AFM) tip is responsible for the shape of the phase and amplitude spectrum. Lastly, we demonstrate that DSFFM is a useful technique for surface characterisation in situations where SFFM may not be adequate.     

Electrochemical Drilling of Inconel Superalloy with Acidified Sodium Chloride Electrolyte

The performance of modern air engine components such as turbine rotor and stator assemblies depends on a very large number of small holes, with diameters and aspect ratios in the range of 1–4 mm and 40–200, respectively. These high-temperature components are made of difficult-to-machine superalloys such as inconel. Shaped tube electrolytic machining (STEM) appears to be the preferred technique for drilling cooling holes in turbine blades. A review of the literature shows that the dynamics of STEM for deep hole drilling have not been sufficiently investigated. Guidelines for the selection of operating parameters such as voltage, electrolyte flowrate, and tool feedrate are not available. The objective of the present investigation has been to optimise the operating parameters of STEM such as voltage and tool feedrate using high-speed steel (HSS). The optimised parameters have then been used for drilling holes in inconel. Experiments show that good holes can be obtained by a combination of low voltage and comparatively high feedrate which results in low values of equilibrium inter-electrode gap. A good, uniform hole with an aspect ratio of 11 was obtained in inconel at voltage and tool feedrate of 17 V and 1.0 mm min _1 , respectively. Results also point to the need for using dummy workpieces above and below the workpiece for obtaining uniform hole diameter, specifically at the ends.     

An integrated microfluidic chip with 40 MHz lead-free transducer for fluid analysis

The design, fabrication, and evaluation of a high-frequency transducer made from lead-free piezoceramic for the application of microfluidic analysis is described. Barium strontium zirconate titanate [(Ba(0.95)Sr(0.05))(Zr(0.05)Ti(0.95))O(3), abbreviated as BSZT] ceramic has been chosen to be the active element of the transducer. The center frequency and bandwidth of this high-frequency ultrasound transducer have been measured to be 43 MHz and 56.1%, respectively. The transducer was integrated into a microfluidic channel and used to measure the sound velocity and attenuation of the liquid flowing in the channel. Results suggest that lead-free high-frequency transducers could be used for in situ analysis of property of the fluid flowing through the microfluidic system.