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In this paper, the width and depth of rectangular surface-breaking defects were successfully gauged using an all-optical laser-ultrasonic system. The finite element method was used to simulate propagating paths of defect-induced reflected and transmitted Rayleigh waves. It is observed that most Rayleigh waves with wavelengths less than the depth of the defect are reflected by the defect. A small part of the Rayleigh waves with wavelengths greater than the depth of the defect directly transmits through the bottom edge of the defect without acting on the left edge of the defect. Based on the simulation results, a three-step detection method of width and depth gauging of rectangular surface-breaking defects is proposed. In the first step, the pulsed laser and detection laser are irradiated on one side of the defect. In the second step, the sample is moved to a certain distance to ensure that both lasers reach the other side of the defect. In the third step, two lasers are irradiated on both sides of the defect. The width and depth of the defect are calculated according to the arrival time of the incident, reflected, and transmitted Rayleigh waves, as well as the movement distance of the sample. Experimental results are consistent with the reference-results measured by using a digital microscope. The proposed three-step detection method is proved to be feasible in simultaneous measurement of the width and depth of rectangular surface-breaking defects. Furthermore, it may be potentially useful for measuring other types of defect structures. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) tip-based nanofabrication is a feasible method to create nanofeatures on a variety of materials. Surface/subsurface integrity is important for qualifying surface performances. However, while machining on crystalline materials, subsurface amorphous layers are inevitably produced because of the large stress in the contact area between the sharp tip and the workpiece surface, which would reduce the mechanical performance of the surface. In this work, multi-pass reciprocating cutting (MPRC) was implemented to reduce the subsurface amorphous layer (SAL) of a single crystal silicon. The mechanism was studied by experiments and molecular dynamic simulation. Results showed the thickness of the amorphous layer can be greatly decreased to a low value and the tip wear can be reduced as well by the MPRC method. On this basis, by optimizing the machining parameters of the MPRC method, nanogrooves with varied depths but few subsurface amorphous phases were successfully fabricated. [Display omitted] • A method of multi-pass reciprocating cutting (MPRC) to fabricate nanostructures was proposed. • Nanostructures with reduced subsurface amorphous layer (SAL) was fabricated. • The tip wear was reduced by the MPRC due to its relatively low normal force. [ABSTRACT FROM AUTHOR]

This paper presents an ultrasonic technique for simultaneous determination of the complete set of acoustical and geometrical properties of a film or a thin layer in a stratified material embedded between two known materials using point-focus ultrasonic spectroscopy, which provides a high lateral resolution. The theoretical model of the two-dimensional spectrum Rt(θ,ω) of the stratified material is calculated as a function of six parameters of the unknown layer: longitudinal and transverse velocities cl, ct, attenuation αl, αt, density ρ, and thickness h, which fully determined the properties of the film. The experimental spectrum Re(θ,ω) can be measured by V(z,t) technique. A two-step algorithm is presented to decompose the searching process of parameters from one six-dimensional to two three-dimensional spaces. The sensitivity of the two-dimensional spectrum to individual properties and its stability against experimental noise are studied. The full set properties of a 250 μm thick stainless steel film and a 930 μm thick SiO2 thin layer of a three layered stratified material immersed in water are determined. The proposed technique used a point-focus transducer, which makes the setup simple and reliable. It allows measurement of the local properties of the film and enables precision material characterization. [ABSTRACT FROM AUTHOR]

This paper focuses on the design of the optimal scanning mode for the family of scanning probe microscopes. Based on different values of the maximum acceleration (deceleration) rate and maximum speed of X- and Y- axes of the mechanical scanner encountered in practice due to different mechanical design and loads, the design procedure of the optimal fast scanning mode is presented, which is found to be sensitive to the specific parameters of the scanning motion. By utilizing the simultaneous motion of the two axes, the fast raster scanning mode proposed can improve the scanning efficiency by 29% when comparing with the conventional raster (CR) scanning mode, if the scanning speeds of both axes are identical. In addition, the optimal fast mode provided by us has no effects on the image accuracy such as image degradation, image distortion when the efficiency is evaluated. No further difficulties are introduced to the control of the mechanical scanner and the data acquisition process. This optimal scanning mode is useful when the response time of the probe is very fast (such as ultrasonic probe in scanning acoustic microscope (SAM)), and the main limitations are due to the mechanical scanner. By applying different loads for both axes, the experiments with different scanning areas and scanning modes are conducted in a self-developed SAM. Experimental results coincide with the theoretical analysis and confirm the validation of our proposed optimal fast scanning mode and its superiority over the CR scanning mode. SCANNING 36:185-193, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The manufacturing process of fiber reinforced polymer laminates could induce local distortions from the nominal fiber architecture. Further, low-velocity impact events may induce additional changes in the fiber architecture, due to local plasticity and delamination formation. These deviations could have a significant effect on the structural performance of composites. This study presents a planar ultrasound computed tomography (pU-CT) technique to reconstruct the local fiber architecture of impacted CFRP laminates. The proposed pU-CT technique employs a pulse-echo scanning modality, and the 3D reconstruction process consists of three subsequent analysis steps: Step 1: Extraction of front- and rear surfaces, delamination interfaces, and interply interfaces. Step 2: Estimation of the out-of-plane ply orientation. Step 3: Extraction of the in-plane fiber direction. The developed pU-CT technique is experimentally demonstrated on an impacted 24-layer CFRP laminate with a stacking sequence [ 45 / 0 / − 45 / 90 ] 3 S. The obtained 3D reconstruction result reveals that the impact event introduced a complex delamination cluster, as well as local plasticity resulting in distorted out-of-plane ply orientation. The in-plane fiber angles remain unaffected and closely match the nominal quasi-isotropic stacking sequence. It is anticipated that the pU-CT method could complement X-ray computed tomography measurements for the inspection of (damaged) CFRP laminates with sizeable dimensions. [ABSTRACT FROM AUTHOR]

Fiber waviness and ply stacking errors compromise the mechanical performance of multi-layer composites. Measuring the local in-plane fiber orientation layer-by-layer is therefore important to assure the structural integrity of a composite. The Radon transform and the Gabor filter methods have been reported to be appropriate for extracting the fiber orientation from an ultrasonic dataset, where the Radon transform method was found to be more accurate and stable. This paper proposes a tomographic reconstruction method on the basis of classical ultrasound pulse-echo testing, in view of reconstructing the local in-plane fiber orientation in multi-layer composites. A 3D ultrasonic dataset is first sliced successively through depth, and each 2D slice is locally analyzed by a Gabor filter method coupled to the concept of an Information Diagram (GF-ID). The GF-ID improves the Gabor filter method by constructing local Gabor filters with optimal orientation and wavelength from which the local in-plane fiber orientations can be obtained in an automated way. The performance of the developed GF-ID method is investigated on both synthetic texture images and an experimental ultrasonic dataset obtained from a 24-layer [45/0/-45/90] 3S carbon fiber reinforced composite. It is found that the GF-ID method yields a high-quality tomographic reconstruction of the local orientations at different scales, and shows high noise resistance. Comparison with the classical Radon transform approach reveals the higher performance of the GF-ID method for ultrasonic reconstruction of the local in-plane fiber orientation in multi-layer composites. • Gabor filter-based Information Diagram (GF-ID) for fiber orientation measurement in multi-layer composites. • Multi-scale and multi-orientation pattern recognition. • Comparatively investigating the Radon transform and the GF-ID method. • Application to multi-scale texture images with local variations and low-contrast 3D ultrasonic data. [ABSTRACT FROM AUTHOR]

The scanning speed of the two-dimensional stage dominates the efficiency of mechanical scanning measurement systems. This paper focused on a detailed scanning time analysis of conventional raster and spiral scan modes and then proposed two fast alternative scanning modes. Performed on a self-developed scanning acoustic microscope (SAM), the measured images obtained by using the conventional scan mode and fast scan modes are compared. The total scanning time is reduced by 29% of the two proposed fast scan modes. It will offer a better solution for high speed scanning without sacrificing the system stability, and will not introduce additional difficulties to the configuration of scanning measurement systems. They can be easily applied to the mechanical scanning measuring systems with different driving actuators such as piezoelectric, linear motor, dc motor, and so on. The proposed fast raster and square spiral scan modes are realized in SAM, but not specially designed for it. Therefore, they have universal adaptability and can be applied to other scanning measurement systems with two-dimensional mechanical scanning stages, such as atomic force microscope or scanning tunneling microscope. [ABSTRACT FROM AUTHOR]

A prototype STM system with high aspect ratio measurement capability is developed to fulfill accurate profile measurement of a high step microstructure with 90° steep sidewall. Distinguished from the traditional STM, the new system consists of a long range piezoelectric (PZT) actuator with full stroke of 60 μm as Z-direction servo scanner, a specially customized high aspect ratio STM probe with effective tip length of 300 μm, and an X-Y motorized driven stage for planar scanning. A tilt stage is used to adjust the probe-sample relative angle to compensate the evitable non-parallel effects. Based on the new STM system, sample-tilt-scanning methodology is proposed for eliminating the scanning blind region between the probe and the microstructure. A high step microstructure with height of 23 μm, 90° steep sidewall and width of 50μm has been successfully measured. The slope angle of the sidewall has been achieved to be 85° and the step height at the rising edge and the trench depth at the falling edge are both measured to be 22.96 μm. The whole measuring process only spent less than 10 min. It provides an effective and nondestructive solution for the measurement of high step or deep trench microstructures. In addition, this work also opens the way for further study on sidewall roughness and the tip-sample interaction at the edge of the sidewall, which are highly valuable for fabrication and quality control of high step microstructures. [ABSTRACT FROM AUTHOR]

Using custom made experimental apparatus, the art of electrochemical etching was systematically studied for fabricating micro/nano tungsten probes with controllable tip profiles of exponential, conical, multidiameter, and calabashlike shapes. The characteristic parameters of probe including length, aspect ratio, and tip apex radius could also be well defined. By combining of static and dynamic etching, the conical-shape probe with length up to several millimeters, controllable tip apex radius, and cone angle could be fabricated. In addition, by continuously lifting the tungsten wire up during the electrochemical etching with different speeds and distances, the multidiameter shape probe could be fabricated. Finally by controlling the anodic flow, the multiple 'neck-in' could be realized creating a calabashlike probe. The aspect ratio of probes depends on (i) the effective contact time between the surrounding electrolyte and the wire, (ii) the neck-in position of immersed tungsten wire. Under the optimized etching parameters, tungsten probes with a controllable aspect ratio from 20:1 to 450:1, apex radius less than 20 nm, and cone angle smaller than 3° could be achieved. The technique is well suited for the tungsten probe fabrication with a stabilized stylus contour, ultra-sharp apex radius, and high production reproducibility. The art for preparing microprobes will facilitate the application of such microprobes in diverse fields such as dip-pen nanolithography, scanning probe microscopy, micromachining, and biological cellular studies. [ABSTRACT FROM AUTHOR]

Abstract: Based on the systematic study of electropolishing process, an improved tungsten STM probe fabrication technique has been presented. The proper combination of pulse current and the electrolyte concentration is explored for the elimination of impurities and achieves high quality probes with ultra-smooth surfaces. An optimized immersion depth of tungsten wire in electrolyte is proposed for the purpose of realizing the probe with sharp apex as well as high aspect ratio structure. A control strategy for determining the power-off instant during the procedure of electropolishing is developed which will facilitate the fabrication of probe with exponential contour as well as ultrasharp tip. The proposed technique and process are experimentally confirmed to have advantages for the STM probe fabrication of the stabilized stylus contour, typically with apex radius of 30nm and the yield rate reaches as high as 85%. [Copyright &y& Elsevier]

Abstract: Adhesion of a pre-stressed silicone rubber film to a planar graphite surface was investigated by a new cylindrical punch method. A homemade apparatus was constructed to meet force and displacement resolutions of 0.1μN and 10nm. When the punch approached the intersurface force range across the punch-film gap, the film jumped into contact at “pull-in”. Upon unloading, once the tensile load reached a threshold, a spontaneous delamination occurred at “pull-off” with a non-zero contact circle. A theoretical model was constructed based a simple energy balance. The new method can be used to characterize an adhesion interface between a pre-stressed free-hanging film and a rigid substrate. [Copyright &y& Elsevier]

Abstract: Elasticity and adhesion of a prestressed circular biomembrane to planar graphite surface was investigated by a video enhanced depth-sensing indentation technique. This biomembrane was a combination of human skin cells and biodegradable polymer. Using this kind of membrane as a skeleton facilitated the easy formation of the hybrid sponges into desired shapes that had a high mechanical strength, while the collagen micro sponges nested in the pores, which allowed the cells to interact with the collagen surfaces. A homemade indenter apparatus was constructed to meet force and displacement resolutions of 0.1 μN and 10.0 nm. The indenter possessed the capability of measuring the applied force and resultant displacement simultaneously. By armed with a high magnification side-view system, it could record lateral profile variation of biomembrane, which was essential for observing and analyzing its gradually rupture. A linear theoretical elastic solution was applied to quantitatively interpret the measured central displacement of the membrane under a central point load. Elastic modulus of the biomembrane could be easily determined once the applied force and the central displacement, together with the essential dimensions were known. The biomembrane “jump-into” an adhesion contact when the punch approached the range of the intersurfaces force across the punch-membrane gap. A “pull-off” event was observed at a nonzero contact circle when the tensile load reaching a critical threshold. This technique provided the capability of measuring mechanical behaviors of prestressed ultra thin tissue and thin-walled biocapsules with a residual stress. [Copyright &y& Elsevier]

A new atomic force microscope (AFM) probe for local conductivity measurement is presented. This silicon nitride based probe with a V-shaped two-dimensional sliced structure tip is patterned by using conventional photolithography method. The probe is then etched to four parallel electrodes that isolated from each other, for the purpose of performing current input and electrical potential drop measurement. The newly developed four-point AFM probe not only inherits the function of AFM surface topography generating but also has the capability of characterizing the local conductivity simultaneously. The nanoresolution position control mechanism of AFM allows the probe scanning across micrometers sized area and creating high spatial resolution map of the in-plane conductivities. Experiments have shown this four-point AFM probe to be mechanically flexible and robust. The repeatable conductivity measurements on the surface of aluminum and indium tin oxide (ITO) thin films indicate this four-point AFM probe technique has potential applications for characterizing devices and materials in microscale. [ABSTRACT FROM AUTHOR]

Abstract: The elastic properties and adhesion of a thin silicone rubber membrane have been characterized. An effective instrumentation embodying a video-enhanced microscope, which meets force and displacement resolution of and 10nm, was developed. It provides the capability of simultaneously measuring both the applied force and the resultant displacement of the thin polymer membrane. A linear theoretical elastic solution was applied to quantitatively interpret the measured central deflection of the membrane under a circular concentrical load. Young''s modulus of the membrane can be easily determined once the applied force and the central deflection, together with the essential dimensions, are known. The membrane jumped into an adhesion contact when the punch approached the range of the inter-surface force across the punch-membrane gap. A pull-off event was observed at a nonzero contact circle when the tensile load reached a critical threshold. The experiment is basically consistent with a theoretical model based on linear elasticity and an energy balance. The new method can be used to measure mechanical behavior of prestressed ultra-thin biomembranes and thin walled biocapsules with a residual stress. [Copyright &y& Elsevier]

We present a new technique to characterize the elastic properties of a thin biological membrane. An effective instrument that embodies video enhanced microscope was developed primarily to provide the capability of simultaneously measuring both the applied force and the resultant displacement of the biological membrane under a central point force. A theoretical linear elastic solution was applied to quantitatively interpret the measured central deflection of the membrane under a central point load. The Young’s modulus of raw and boiled Leghorn egg inner tissue can be easily determined once the applied point load and the central deflection, together with the essential dimensions are known. The viscoelasticity property of natural tissue was manifest in the experiment. The experimental results have verified that the novel technique is applicable to determine the Young’s modulus and other viscoelatic properties of thin biological tissue. [Copyright &y& Elsevier]

We present a new method to characterize the viscoelastic properties of a thin polymeric film. A sensitive microscope visualization instrument was used for measuring the time-dependent deformation, i.e. creep, of the circular thin membrane under a constant load. The elastic deformation of the thin membrane was measured laterally. The elastic modulus as a function of time can be explicitly determined by our recently developed equations. A viscoelastic theory, Zener model, was applied to interpret the measured time-dependent deformation of the membrane under various temperatures, and the creep parameters can therefore be quantitatively estimated. The results show the elastic constants and viscosity coefficient of the membrane materials decrease with the increasing temperatures. [Copyright &y& Elsevier]

In this paper, transmitted surface waves are used to quantitatively detect the length and angle of inclined surface cracks based on laser ultrasonic technique. The interaction between laser-generated surface waves and inclined surface cracks is analysed, and the propagation path and mode conversion process of the transmitted surface waves are considered. Then, the propagation paths of some peaks and troughs of the transmitted surface waves are obtained. Based on the obtained path and modal conversion information, a quantitative detection method for the length and angle of inclined surface cracks is proposed. The finite element method is used to verify the propagation paths and proposed method, and the results show that the arrival time of the theoretical path is consistent with that of the simulation. The relative measurement errors of the surface crack length and angle are less than 15% and 10%, respectively, which verifies the rationality and correctness of the proposed method. [ABSTRACT FROM AUTHOR]

A symmetric modulation methodology is proposed to combine robust control of external disturbance, rapid response to steep sidewalls with the high speed of a traditional scanning tunneling microscopy. The 1400 × 200 μm2 topography of a comb-like steep sidewalls micro-structure with the depth of 23 μm was acquired at a high scanning speed of 120 μms-1 and the detectable slope angle is up to 85°. The total measuring time was only 17 min. In addition, a 4 × 4 mm2 aluminum dual-sinusoidal array has been successfully measured with a scanning speed up to 500 μms-1. It improved the performance of the normal scanning tunneling microscope and enables efficient and stable measurement of large-area complex micro-structures, and thus can be introduced to engineering applications. [ABSTRACT FROM AUTHOR]

A compact but practical scanning tunneling microscope (STM) with high aspect ratio and high depth capability has been specially developed. Long range scanning mechanism with tilt-adjustment stage is adopted for the purpose of adjusting the probe-sample relative angle to compensate the non-parallel effects. A periodical trench microstructure with a pitch of 10 μm has been successfully imaged with a long scanning range up to 2.0 mm. More innovatively, a deep trench with depth and step height of 23.0 μm has also been successfully measured, and slope angle of the sidewall can approximately achieve 67°. The probe can continuously climb the high step and exploring the trench bottom without tip crashing. The new STM could perform long range measurement for the deep trench and high step surfaces without image distortion. It enables accurate measurement and quality control of periodical trench microstructures. [ABSTRACT FROM AUTHOR]

In this paper, the depth and length of lateral subsurface cracks were gauged using laser-generated Rayleigh waves in the frequency domain. First, the frequency domain characteristics of reflected and transmitted Rayleigh waves after a laser-generated Rayleigh wave interacts with lateral subsurface cracks are investigated based on the finite element method (FEM). The simulation results reveal that there is a certain relationship between the center frequency of reflected and transmitted Rayleigh waves and crack size. The center frequency of the reflected Rayleigh wave decreases with increasing crack length but is independent of depth. When the crack length remains unchanged, the center frequency of the transmitted Rayleigh wave increases with increasing crack depth. Then, the quantitative relationships between the ratio of the crack length to the incident Rayleigh wavelength and the ratio of the reflected Rayleigh wave frequency to the incident Rayleigh wave frequency, the ratio of the crack depth to the incident Rayleigh wavelength and the ratio of the transmitted Rayleigh wave frequency to the incident Rayleigh wave frequency were obtained via multiple function fitting, and a method for the quantitative detection of the lateral subsurface crack depth and length was proposed. Finally, experimental and simulated data were used to validate the proposed relationships, and the results showed that the relative error of the measured crack length did not exceed 7.19% and that the relative error of the measured crack depth did not exceed 14.82%. The results show that the method has good application prospects for the quantitative measurement of lateral subsurface crack depth and length. [ABSTRACT FROM AUTHOR]

A noise-resistant linearization model that reveals the true nonlinearity of the sensor is essential for retrieving accurate physical displacement from the signals captured by sensing electronics. In this paper, we propose a novel information-driven smoothing spline linearization method, which innovatively integrates one new and three standard information criterions into a smoothing spline for the high-precision displacement sensors' linearization. Using theoretical analysis and Monte Carlo simulation, the proposed linearization method is demonstrated to outperform traditional polynomial and spline linearization methods for high-precision displacement sensors with a low noise to range ratio in the 10−5 level. Validation experiments were carried out on two different types of displacement sensors to benchmark the performance of the proposed method compared to the polynomial models and the the non-smoothing cubic spline. The results show that the proposed method with the new modified Akaike Information Criterion stands out compared to the other linearization methods and can improve the residual nonlinearity by over 50% compared to the standard polynomial model. After being linearized via the proposed method, the residual nonlinearities reach as low as ±0.0311% F.S. (Full Scale of Range), for the 1.5 mm range chromatic confocal displacement sensor, and ±0.0047% F.S., for the 100 mm range laser triangulation displacement sensor. [ABSTRACT FROM AUTHOR]

We studied a multi-metallic microscale 3D printing based on the meniscus-confined electrodeposition (MCED). The composition of Cu/Pt alloys can be controlled by applying different bias voltages to the CuSO4/H2PtCl4 mixed solution in MCED. We find that a double-barrel system had higher Cu/Pt alloy purity (maximum 100% Cu or maximum 80% Pt) than a single-barrel system. A Λ-shaped microstructure was printed to verify the capability to multi-metal microstructures in a single printing process. [ABSTRACT FROM AUTHOR]

To achieve quantitative detection of subsurface-inclined cracks, the reflected surface waves from subsurface cracks with different lengths and angles were obtained by the finite element method (FEM). The relationship between the time difference of each feature wave in the reflected waves and the length and angle of the subsurface inclined crack was analysed. The arrival time difference between the lowest trough and the first trough of the reflected wave is independent of the angle of the subsurface crack and approximately a linear function of the crack length. Furthermore, when the crack lengths remain unchanged, the arrival time difference between the highest peak and the second trough of the reflected wave is a quadratic function with the angle of the subsurface crack. Thus, a quantitative measurement method for gauging the length and angle of subsurface inclined cracks is proposed based on the above phenomena. The relationships between the length and angle of the subsurface inclined crack and the arrival time difference of the reflected surface waves were obtained by curve fitting. The proposed method was verified by simulation data. The maximum relative error of the crack length obtained by the method was 7.76%, and the maximum relative error of the obtained inclination angle was 11.61% when the crack angle was large. The proposed approach will open the way for simultaneous measurement of the length and angle of subsurface inclined cracks and structures. [ABSTRACT FROM AUTHOR]

The out‐of‐band energy loss caused by in‐built color filters significantly degrades the signal‐to‐noise ratio and the dynamic range of conventional image sensors, which has restricted the attempt to develop ultrahigh‐density imaging devices by merely shrinking the pixel size. This issue will be more serious for security cameras, which need to collect both visible (VIS) and near‐infrared (NIR) light. The existing solutions mostly explore complex photonic nanostructures, which are often too complicated for production. In this work, a pixelated spectral router is demonstrated utilizing a 2D Si3N4 Mie‐type metagrating that can spatially divide NIR (850 nm) and VIS (400–700 nm) light to different pixels at high efficiencies. It has a minimum feature size larger than 360 nm, highly promising for massive production. Compared with the traditional filter design, this router can gain ≈42% and ≈30% signal enhancement for NIR and VIS bands, respectively. It is shown that it also has good polarization insensitivity and incident angle tolerance. The NIR–VIS simultaneous imaging is inspected without any complex reconstruction algorithm. Mode analysis indicates that the periodic interference of multipolar scattered fields caused by this metagrating provides the necessary degrees of freedom to spatially optimize the routing functions for broadband photons. [ABSTRACT FROM AUTHOR]

Detection of surface defects is critical in quality control of reflective optics. In this note, we propose a new surface defect detection method for reflective optics using the normalized reflectivity, which is calculated from the signal intensity of a chromatic confocal surface profiler. This detection method first scans the surface to acquire signal intensity data and then models the intensity data to calculate the normalized local reflectivity map. The reflectivity map is further processed by threshold segmentation to extract defects from normal areas. Measurement experiments on an Al-coated concave reflector with artificial defects were carried out to demonstrate the feasibility of the method. This detection method can provide existing optical surface profilers with defect detecting capabilities without extra equipment. [ABSTRACT FROM AUTHOR]

Grooved nerve guide conduits (NGCs) have been effective in the clinical treatment of peripheral nerve injury. They are generally fabricated from a micro-structured spinneret using a spinning process, which easily can cause a variety of pores and morphological deviation. The topography of internal grooves as well as the porosity can greatly influence the therapeutic effect. Traditional optical or scanning electron microscopy (SEM) methods can be used to image the grooves; however, these methods are destructive and require slicing NGCs to prepare specimens suitable for imaging. Moreover, lengthy experiments and large batches of NGCs are required to ensure reliable results from both in vitro experiments and clinical studies. In this paper, a non-destructive method for evaluating the grooves and porosity of NGCs is proposed using ultrasonic imaging combined with rotary scanning and an image analysis algorithm. Two ultrasonic methods were used: a 25-MHz point-focus ultrasonic transducer applied to observe axial cross sections of the conduits and a 100-MHz point-focus ultrasonic transducer to detect large pores caused by defects. Furthermore, a theoretical algorithm for detecting the local porosity of a conduit based on density is proposed. Herein, the proposed acoustic method and traditional optical methods are evaluated and compared. A parameter representing the specific surface area of the internal grooves is introduced and computed for both the optical and acoustic methods, and the relative errors of the computed parameter values for three different NGCs were 7.0%, 7.9%, and 15.3%. The detected location and shape of pores were consistent between the acoustic and optical methods, and greater porosity was observed in the middle of the conduit wall. In this paper, the results of the acoustic and optical methods are presented and the errors relating to the acoustic factors, device characteristics, and image processing method are further analyzed. [ABSTRACT FROM AUTHOR]

Cross-mode-family mode conversion and secondary reflection of guided waves in pipes complicate the processing of guided waves signals, and can cause false detection. In this paper, filters operating in the spectral domain of wavenumber, circumferential order and frequency are designed to suppress the signal components of unwanted mode-family and unwanted traveling direction. Common-source synthetic focusing is used to reconstruct defect images from the guided wave signals. Simulations of the reflections from linear oblique defects and a semicircle defect are separately implemented. Defect images, which are reconstructed from the simulation results under different excitation conditions, are comparatively studied in terms of axial resolution, reflection amplitude, detectable oblique angle and so on. Further, the proposed method is experimentally validated by detecting linear cracks with various oblique angles (10–40°). The proposed method relies on the guided wave signals that are captured during 2-D scanning of a cylindrical area on the pipe. The redundancy of the signals is analyzed to reduce the time-consumption of the scanning process and to enhance the practicability of the proposed method. [ABSTRACT FROM AUTHOR]

The authors are retracting the referenced paper[1] that was found to utilize the formalism and parameters of Ref. [2] without attribution. Retraction: "3D printing of multi-metallic microstructures by meniscus-confined electrodeposition" [Rev. Sci. Instrum. 93, 025102 (2022).10.1063/5.0076677 2 A. Ripoll Oliveras, "Microscale 3D printing of multi-metal in meniscus-confined electrodeposition", M.S. thesis (Universitat Politècnica de Catalunya); available at https://upcommons.upc.edu/bitstream/handle/2117/333489/mt-albertripoll-multi-metal-printing-corrected.pdf?sequence=1&isAllowed=y (2020). [Extracted from the article]

In a machining process, cutting force is one of the most important machining parameters which can directly reflect the state of tool and quality of the machined workpiece. The cutting force in micro/nano cutting is required to be measured with a high accuracy of a few millinewtons. However, traditional cutting force indirect estimation methods are difficult to meet the high-accurate measurement requirement. In this paper, a reliable and high-accurate cutting force estimating method based on machine learning for a fast tool servo driven by Lorentz force without using additional sensors is proposed. A concept of virtual forces, which could enable obtaining sufficient type of forces than that by actual cutting, is developed to increase the data training accuracy. In addition, an effective data filtering method combining the fast Fourier transform and the inverse fast Fourier transform is adopted to further improve the estimation accuracy. Cutting force estimated by the proposed method is compared with that estimated by traditional disturbance observer and Kalman filter, which demonstrates a much better estimation accuracy. The experiment results show that the estimated cutting force is in good consistent with the best commercial dynamometer. Even the details of small cutting force fluctuation on the order of 50 mN can be clearly identified. The experimental results demonstrated that the cutting force estimation method for micro/nano machining process could have a high measurement resolution of 10 mN and relatively measurement error as small as 0.4%. • A high-accurate cutting force estimation based on machine learning for a VCM driven FTS is proposed. • A concept of virtual forces is developed to increase the data training accuracy. • A data filtering method combining the FFT and the inverse FFT is adopted. • The estimated cutting force is in good consistent with the best commercial dynamometer. [ABSTRACT FROM AUTHOR]

In this paper, a fiber-based chromatic dispersion probe for simultaneous measurement of X-axis and Z-axis displacements with nanometric resolutions by using the full width at half maxima (FWHM) of the detected spectral signal has been proposed and demonstrated. For X-axis, FWHM is employed for indicating the X-axis displacement based on the fact that the FWHM remains almost constant with the varying Z-axis displacement of the fiber detector and shows a linear relationship with the X-axis displacement within a specific Z-axis displacement range. For the Z-axis, the linear relationship between the centroid wavelength λ of the detected spectral signal and the Z-axis displacement is employed for indicating the Z-axis displacement based on the fact that the sensitivity (slope of the λ-Z curve) is also linear with X-axis displacement within a certain X-axis displacement range. Theoretical and experimental investigations have verified the feasibility of the proposed chromatic dispersion probe, which yields X- and Z-axis measurement ranges of 2.3 μm and 15 μm and X- and Z-axis measurement resolutions of better than 25 nm and 50 nm, respectively. Experiments were further performed to evaluate the basic performance of the prototype probe and the maximum measurement errors were less than 10 nm and 60 nm for X- and Z-axis displacements, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a fiber-based chromatic dispersion probe for the simultaneous measurement of dual-axis absolute and relative displacement with nanometric resolutions. The proposed chromatic dispersion probe is based on optical dispersion. In the probe, the employed light beam is split into two sub-beams, and then the two sub-beams are made to pass through two optical paths with different optical settings where two identical single-mode fiber detectors are located at different defocused positions of the respective dispersive lenses. In this way, two spectral signals can be obtained to indicate the absolute displacement of each of the dual-axes. A signal processing algorithm is proposed to generate a normalized output wavelength that indicates the relative displacement of the dual-axis. With the proposed chromatic dispersion probe, the absolute and relative displacement measurements of the dual-axis can be realized simultaneously. Theoretical and experimental investigations reveal that the developed chromatic dispersion probe realizes an absolute measurement range and a measurement resolution of approximately 180 μm and 50 nm, respectively, for each axis. Moreover, a relative displacement measurement range and a measurement resolution of about 240 μm and 100 nm, respectively, are achieved for the dual-axis. [ABSTRACT FROM AUTHOR]

In this study, the widths of subsurface lateral rectangular defects were successfully gauged using laser-generated Rayleigh waves. Finite element analysis was used to simulate the interaction between Rayleigh waves and subsurface defects. The results of the simulation show that diffracted bulk modes resulting from the interaction between Rayleigh waves and subsurface defects may interact with the free surface. Modes are converted into Rayleigh waves that propagate along the surface. The arrival time of reflected mode-converted Rayleigh waves remains constant, even when the height of subsurface defects increases. However, as the depth increases, the arrival time of reflected mode-converted Rayleigh waves changes due to mode conversion caused by diffracted bulk modes interacting with the free surface. The influence of mode conversion was quantitatively analyzed and taken into account in the width measurement method for subsurface lateral defects. Experimental results are consistent with simulation results and show that Rayleigh waves induced by a pulsed line laser are sensitive to subsurface defects. Finally, the proposed method may be potentially useful for width measurements of other types of subsurface structures. [ABSTRACT FROM AUTHOR]

Microleverage mechanism which is widely applied in microelectromechanical systems (MEMS) transfers and amplifies force or displacement from input to output. In this work, one-stage microleverage mechanism is integrated into a biaxial micro resonant accelerometer to improve sensitivity. Force amplification factor of the microleverage is analyzed and deduced by integral method. The results from theoretical model match well with the ones from finite element method (FEM) simulation, which proves that the proposed model is relatively accurate and the width of lever beam is a quite important parameter in design. The resonant accelerometer is successfully fabricated by MEMS technology. Preliminary experiments are conducted and demonstrate differential sensitivity of 71 Hz/g for the accelerometer with resonant frequency of 267.726 kHz. [ABSTRACT FROM AUTHOR]

This paper presents a new on-machine measuring system based on scanning tunneling microscope principle, in order to meet the demand for precision form control of fabricated micro-structures. It is compactly established and mounted on a diamond turning machine, capable of on-machine measuring microstructures with steep slopes and size of tens of micrometers, which remains a challenge task to accomplish undistorted measurement even for general off-line metrological methods. Fly cutting with V-tip fly-cutter was first applied in two directions with interval angle of 60° to form the crossed micro V-grooves, and then efficient on-machine measurement was carried out to characterize the machined surface form without ending the proceeding of the subsequent fabrication. By depth compensation of fly cutting in 120° direction through feedback of on-machine measured results, the surface of rectangular pyramid array with diamond-shaped feature was successfully generated. Experimental results demonstrate that the proposed measuring system is of significance in the fabrication process, owing to its efficient on-machine characterization capability for generating accurate micro-structured surfaces. [ABSTRACT FROM AUTHOR]

In this study, the feasibility and reliability of detecting the depth and length of subsurface cracks in combination with backpropagation neural network (BPNN) and laser-generated surface acoustic waves (SAW) are explored. First, the interaction between SAWs and subsurface cracks is simulated by the finite element analysis. Then, the reflected and transmitted SAWs from the cracks with different depths and lengths are obtained. Next, characteristic parameters of the transmitted and reflected surface waves in the time domain and frequency domain are extracted through the Fourier transform and wavelet transform methods. These parameters are filtered according to the network contribution and are used to train and test the BPNN. A set of out-of-sample signals is used to estimate the depth and length of subsurface cracks. The obtained results demonstrate a very good correlation with the actual results, while the relative estimation error is less than 4%. It can be concluded that the BPNN method coupled with the laser ultrasonic technique is promising in the quantitative measurement of the depth and length of subsurface cracks. [ABSTRACT FROM AUTHOR]

This paper presents the implementation and verification of a dual-probe measurement system with a novel method and easily integrated chromatic confocal probes, for synchronous evaluation of not only the inner and outer cylindricity but also the thickness distribution of a ring-type cylinder. A pair of measuring probes mounted on a four-axis scanning stage, which is composed of XYZ -slides and a spindle, is utilized to target the two sides of the ring-type cylinder. In the developed system, to reduce the influence of the positioning errors and tilt misalignments of the confocal probes and the cylinder, alignment methods are developed. The outputs of the measuring probes are employed to accurately evaluate the geometric errors of the ring-type cylinder through performing spiral scanning while separating the Z -slide and spindle motion errors of the scanning stage based on a reversal error separation method. To verify the performance of the proposed system and method, the geometric errors of a thin-walled cylinder which has a nominal outer diameter of 50 mm, an inner diameter of 40 mm, and a length of 100 mm are evaluated in experiments. The experimental results are further compared with those by a coordinate measuring machine (CMM), and the high correspondence of the comparison results well confirm the feasibility of the implemented measurement system. Finally, measurement uncertainty analysis is conducted to demonstrate the reliability of the proposed method for the evaluation of the geometric errors of ring-type cylinders. The measurement accuracy is comparable to that of a CMM. • A dual-probe measurement system was developed for geometrical evaluation of ring-type cylinders. • The inner, outer roundness and thickness distribution of a ring-type cylinder was simultaneously measured. • The measurement uncertainty was analyzed to confirm the reliability of the proposed method. [ABSTRACT FROM AUTHOR]

• An all-optical laser-ultrasonic system was developed. • Mode-converted Rayleigh waves from rectangular subsurface defects were detected. • A detection method for gauging rectangular subsurface defects was proposed. • Width and depth of rectangular subsurface defects were successfully gauged. In this study, width and depth of rectangular subsurface defects have been successfully gauged based on all-optical laser-ultrasonic technology. A specific all-optical laser-ultrasonic system has been developed to obtain Rayleigh waves from subsurface defects. Time domain and frequency domain analysis of the obtained Rayleigh waves show that most of the high-frequency Rayleigh waves with small wavelengths transmit the subsurface defect. Only a small part of the low-frequency Rayleigh waves with large wavelengths are reflected by the subsurface defect. This phenomenon is completely different from that of surface defect, because surface defect reflects high-frequency Rayleigh waves and allows low-frequency Rayleigh waves to transmit. In addition, it is found that the transmitted mode-converted Rayleigh wave has the smallest amplitude but the highest center frequency compared with other obtained incident, reflected mode-converted and transmitted Rayleigh waves. Width and depth of subsurface defects are measured by the proposed three-step detection method, which is based on the arrival time of the incident, reflected mode-converted, transmitted and transmitted mode-converted Rayleigh waves, as well as the movement distance of samples. Agreement between experimental results and digital microscope measurement reference-results indicates applicability of the proposed three-step detection method in simultaneous measuring width and depth of rectangular subsurface defects. [ABSTRACT FROM AUTHOR]

Additive manufacturing is a rapidly evolving technology for the fabrication of 3D metallic microstructures. However, the production of complex 3D metallic micro/nanoscale structures with satisfactory mechanical properties is challenging for existing additive manufacturing technologies. In this study, a voxelated meniscus-confined electrodeposition 3D printing technology was developed to fabricate 3D metallic structures in an ambient environment at the microscale and nanoscale with high stiffness and stability. The proposed method changes the continuous meniscus-confined electrodeposition process to a discrete process, which facilitates the fabrication of 3D metallic microstructures and strengthens the stiffness of meniscus-confined electrodeposition. To verify the newly proposed method, a single-voxel deposition, micropillars, a micropillar array, tilt micropillars, and multi-pillar supporting microstructures were fabricated. In-situ microscale compression tests under scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were conducted to compare the mechanical performances of the fabricated metallic microstructures obtained using the continuous and the voxelated meniscus-confined electrodeposition methods. Our results demonstrate that micropillars fabricated via the voxelated meniscus-confined electrodeposition method could have much smaller nanograined structures and have higher stiffness than those structures fabricated via the continuous method. We discussed the formation process of nanograins fabricated by the voxelated method and it is found that the superior mechanical property of the structures fabricated by the voxelated method was owing to its high current density and discrete voltage supply in the electrodeposition process. [Display omitted] • Voxelated meniscus-confined electrodeposition was developed for fabrication of 3D metallic microstructures. • Microstructures fabricated by the voxelated electrodeposition have better mechanical properties than traditional ones. • Micro-pillar fabricated using the voxelated method has nanograins with much smaller sizes than conventional ones. [ABSTRACT FROM AUTHOR]

This paper presents force servo single point diamond cutting of freeform surfaces with nano-precision on a micro-precision machine. For nanometric machining accuracy, traditional diamond cutting based on position servo, requires accurate machine axial motions by ultra-precision machine with high cost, or utilizes a fast tool servo to compensate for machine slide vibration and motion error of common machines that is a complicated procedure. In this paper, nanometric machining accuracy was achieved on a micro-precision machine by force servo diamond cutting, in which the tool can be driven to trace the workpiece surface to compensate for the machine slide vibration, machine motion errors and workpiece incline errors accurately and automatically. For highly sensitive and stable force controlling, force servo nanocutting mechanism (FSNM) based on flexible structures was designed with force sensing resolution down to submillinewton level, and a damping controller was developed to suppress the resonant vibration of the FSNM. For extending application of force servo cutting from fabrication of only discontinuous microstructures to continuous freeform surfaces, referring force maps were developed by considering the real material removal volume of each cutting point. Force servo cutting was then validated by fabricating freeform surfaces with surface form errors of less than 10 nm on silicon spherical surfaces based on the micro-precision machine. The works discussed in this paper provide an effective technique for the fabrication of complex and continuous microstructured and freeform surfaces with nano-precision by common machines only with micron even tens of microns precision. [Display omitted] • Force servo nanocutting mechanism was designed with force sensing resolution of submillinewton level. • Machine slide vibration and motion errors were automatically compensated in force servo cutting process. • Fabrication of nano-precision complex freeform surfaces was achieved on a machine with only micro-precision. [ABSTRACT FROM AUTHOR]

• A regression model is established by using machine learning (ML) for femtosecond laser micromachining of 3D curved surfaces on single crystal sapphire. • The quantitative relationship between femtosecond laser processing parameters and the processed 3D functional curved surface topography is established. • The maximum profile prediction error of the 3D curved surfaces is within 12.6% by the ML regression model, without any prior optimization experiments. In this study, a regression model is proposed using the machine learning (ML) method for femtosecond laser micro-machining of three-dimensional (3D) surface profiles on flat single-crystal sapphire. Based on the ML regression model, a quantitative relationship is established between the femtosecond laser processing parameters and the processed 3D functional curved surface topography. The combination of laser processing parameters (i.e. laser fluence F 0 , hatch d h, and scanning speed v) is also optimized according to the predicted parameters (i.e. surface quality Ra , ablation depth Z, and material removal rate MRR). Finally, the optimized combination of laser processing parameters was employed to process 3D surface profiles on flat single-crystal sapphire sheets. The maximum predicted profile error of the 3D structures was approximately 12.6% without any prior optimization experiments. Both the numerical simulation and experimental results demonstrate the feasibility of the proposed ML regression model in optimizing laser processing parameter combinations to achieve the desired 3D surface geometries on single-crystal sapphire by femtosecond laser micro-machining without trial-and-error. [ABSTRACT FROM AUTHOR]

A force controlled nanocutting system based on a flexible mechanism was developed. Instead of utilizing force sensors, the force sensing and control in the developed system is realized by sensing and controlling the deformation of the flexible mechanism. With force feedback control for controlling the cutting force in real time, this system could achieve adaptive cutting along non-planar surfaces without prior knowledge about the surface shape. The finite element method was used to model the flexible mechanism and a Pareto-based multi-objective optimization algorithm with the goals of high force resolution and stability was used to obtain the geometric parameters of the flexible mechanism. During the cutting processing, a capacitive displacement sensor was used to detect the deformation of the flexible mechanism to measure the force in real time, and a piezoelectric ceramic actuator was used to adjust the feed position of the tool to control the cutting force. Nanocutting experiments of microstructures were successfully carried out on inclined and curved surfaces of ductile as well as brittle materials without prior knowledge of their surface forms. • A force controlled nanocutting system based on a flexible mechanism (FM) was developed. • The cutting force sensing and control is realized by sensing and controlling the deformation of the FM without using force sensors. • Adaptive cutting of microstructures along non-planar surfaces was achieved. [ABSTRACT FROM AUTHOR]

• Metrological evaluation of microstructure surfaces is vital to their performances. • Dynamic mode SPMs are more suitable for surfaces with large height distribution. • Error source sensitivity guides the design and setup of metrological equipment. • Surface geometry has a great influence on the final measurement error distribution. • Compensation scheme based on geometric error model promise better accuracy. This paper presents a novel measurement error model for closed-loop surface metrology. In these surface metrology systems, the motion of the probe tip is strictly constrained on a parallel surface that is separated from the measured sample surface of constant displacement by closed-loop controllers. Examples of such metrology systems include constant signal mode scanning probe microscopes and coordinate measuring machines. The combined effect of volumetric errors and surface tracking controllers on the final measurement error was analyzed using an error model developed based on multi-body system theory and surface geometry. A comprehensive overview of the errors of a typical large-scale scanning tunneling microscopy system is provided as an example. Simulations were performed to illustrate the influence of the systematic errors on the final accuracy. Experiments were also conducted on the measurement of a typical micro-structured surface to both verify the proposed error model and establish a possible compensation scheme. [ABSTRACT FROM AUTHOR]

Cutting force measurement is important for monitoring the diamond cutting process. In this paper, a new measurement method of thrust cutting force associated with a voice coil motor (VCM) driven fast tool servo (FTS) system has been developed. Instead of integrating additional force sensors to the FTS which would influence the dynamics of the FTS, the force measurement in the proposed system is achieved associated with in-process monitoring the variation of the driving current of the VCM and pre-process determining the system parameters. In this way, the cutting forces are accurately obtained by subtracting the influences of the driving force, the spring force, the damping force and the inertial force associated with the system as well as the cutting process. Based on the proposed method, a microstructure array was machined using the developed VCM-FTS and the cutting force during the machining process was monitored in real time. The measured force signal was in good agreement with the machining result. The surface profile error of the fabricated microstructure could be clearly distinguished by the variation of the measured cutting force signal. This provides a new approach for in-process cutting force measurement associated with FTS based diamond cutting process. • A cutting force measuring method associated with a voice coil motor (VCM)-driven fast tool servo (FTS) system has been developed. • Cutting force in diamond cutting are in-process measured without any force sensor by the VCM-FTS. • The influences of servo motion induced forces are separated for accurately obtaining the cutting forces. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the surface profile measurement of a XY-grid workpiece with sinusoidal microstructures using an atomic force microscope (AFM) on a diamond turning machine. The sinusoidal micro-structures, which are fabricated on an aluminum plate by fast tool servo-assisted diamond turning, are a superposition of periodic sine-waves along the X- and Y-directions (wavelength (XY): 150μm, amplitude (Z): 0.25μm). A linear encoder with a resolution of 0.5nm is integrated into the AFM-head for accurate measurement of the Z-directional profile height in the presence of noise associated with the diamond turning machine. The spindle and the X-slide of the machine are employed to spirally scan the AFM-head over the sinusoidal grid workpiece. Experiments fabricating and measuring the sinusoidal grid workpiece are carried out after accurate alignment of the AFM cantilever tip with the spindle centerline. [Copyright &y& Elsevier]

Meniscus-confined electrodeposition is a potential approach to fabricate three-dimensional (3D) metallic microstructures. However, the quality of the deposited microstructures by this approach, which is conventionally checked by a scanning electron microscope (SEM) used off-process, cannot be well in-process qualified. This paper presents a study on meniscus-confined electrodeposition of metallic microstructures with in-process monitoring of deposition qualities. Firstly, to understand the fabrication mechanism in meniscus-confined electrodeposition which formed the fundamental for quality control, mathematical model was derived to study the geometric shape of the meniscus. Multi-physical field simulation was carried out to investigate the effect of several process parameters on the deposition results, including the micropipette aperture, biased voltage and solution concentration, etc. Meniscus-confined electrodeposition of metallic micro-wires by utilizing a micropipette was carried out. The ionic current during the electrodeposition is in-process monitored for contact point detection and fabrication quality monitoring. The corresponding relationship between the quality of the fabricated micro-wires and the in-process monitored ionic currents was investigated. This study provides a potential way for in-process quality control with the local electrodeposition method. • The meniscus-confined electrodeposition is in-process qualified by ionic current measurement. • Multi-physical field simulations and experiments were conducted to investigate the effect of several process parameters. • It provides a potential way for in-process quality control for micro/nano-scale electrodeposition. [ABSTRACT FROM AUTHOR]

The multilayer structure of fiber-reinforced polymers may be extracted by ultrasonic pulse-echo inspection. Depending on the employed ultrasonic frequency and subsequent processing methodology, different depth resolution and dynamic depth range can be achieved. This study compares the performance of different ultrasonic pulse-echo approaches for extracting the ply-by-ply structure of multilayered composites. The following methodologies are studied: Method 1: 50 MHz, 15 MHz, and 5 MHz ultrasound with low-pass filtering using analysis of the instantaneous amplitude, Method 2: 15 MHz ultrasound with Wiener deconvolution (and autoregressive spectral extrapolation) using analysis of the instantaneous amplitude, and Method 3: 5 MHz ultrasound with low-pass or log-Gabor filtering using analysis of the instantaneous phase. In the simulation study, the performance of the various techniques is investigated on synthetic data representative for a 24-ply carbon fiber reinforced polymer. The robustness of the techniques is evaluated for different signal-to-noise ratios. The various techniques are further investigated on experimental data of a 24-ply cross-ply carbon fiber reinforced polymer. The ply-by-ply structure is extracted and presented in the form of both B-scan and C-scan images. The thickness of each ply is estimated for quantitative analysis. The obtained results indicate that the 5 MHz ultrasound coupled to analytic-signal analysis with log-Gabor filter shows the best performance for reconstructing the multilayer structure of the studied composites. [ABSTRACT FROM AUTHOR]

Recently, researchers proposed the use of ultrasound combined with analytic-signal concepts for the reconstruction of the internal ply structure of composites. Optimal parameters for the pulse-echo mode ultrasonic testing are determined by modeling the analytic-signal response. The internal structure can be reconstructed by instantaneous metrics based on the interaction of the multilayer structure and the ultrasonic wave. However, there are certain drawbacks associated with the use of instantaneous metrics. The phase-derived interply track tends to be sensitive to the inspection conditions. This paper analytically studies the errors of the interply tracking for a wide range of parameters, including (i) signal-to-noise ratio, (ii) bandwidth, (iii) interply thickness, and (iv) attenuation, amongst others. It provides a guideline on how to improve the performance of the interply tracking procedure in real measurements. An experimental study combining the analytic-signal procedure with a standard log-Gabor filter in the frequency domain is performed to derive the interply tracks of a 24-layer composite laminate in a robust way. The bandpass filter selects the appropriate frequency band of the analytic-signal response from the composite. It shows a good ability for frequency and bandwidth selection, and can efficiently cope with noise features. The reconstructed ply tracks in A-scan, B-scan, and C-scan modes are analyzed to verify the performance of this procedure. • Investigating the errors of the interply tracking by analytic-signal technique. • Providing a guideline on how to improve the performance of the interply tracking. • The analytic-signal procedure with a standard log-Gabor filter is presented. • The ply tracks of a 24-layer composite laminate are analyzed to verify the procedure. [ABSTRACT FROM AUTHOR]

This paper presents a fast tool servo (FTS) driven by a voice coil motor (VCM) with a function of self-sensing of cutting forces. Conventionally, cutting force measurement associated with a FTS system is made by integrating an additional force sensor or a dynamometer, which would make the system complicated and influence the dynamic performance of the FTS. Differing from the conventional method, the force measurement in the proposed system is achieved by detecting the current of the VCM and then obtaining the cutting force based on the electromagnetic field distribution of the VCM. Since it is not necessary to integrate additional force sensors, the main body of the FTS could be compact and the dynamics of the FTS would not be influenced by the added function of force measurement. The FTS mainly consists of an air bearing guide driven by a VCM with a stroke of 2.5 mm, an optical encoders feedback system for precision positioning and a hall current sensor for current measurement. To obtain forces from the measured currents, the magnetic field distribution of the VCM is figured out and the nonlinear relationship between the position and the magnetic field distribution is corrected. The basic performances of the FTS for positioning and force measurement were experimentally investigated. It is shown that the system could have a positioning resolution of 20 nm and a force self-sensing resolution of 5 mN based on the proposed method. The proposed method provides a new way for in-process cutting force measurement associated with FTS systems. • A VCM-FTS is developed with a function of self-sensing of cutting forces. • Cutting forces are measured by detecting the current of the VCM without using additional force sensors. • The force measurement resolution by the proposed method was evaluated to be 5 mN. [ABSTRACT FROM AUTHOR]

A quantitative analysis of the acoustic potential well has been proposed for the purpose of realizing stability improvement of ultrasonic transportation. It was found that the boundary Rp and elastic constant kl(l,θ) of the acoustic potential well, acoustic radiation force offset ratio βfl, and elastic constant offset ratio βkl are the critical parameters that define the trapping ability. They were made clear both their intrinsic significance. The stability of the ultrasonic transportation using three transducers is theoretically studied. Long range ultrasonic transportation of silica beads with better stability is realized by optimizing the acoustic parameters to get the well-defined acoustic potential wells. No slip-off the equilibrium position has been observed, which proved its strong ability of trapping and transportation. Because of its simplicity, flexibility, and non-destructivity, the ultrasonic transportation offered a competitive micro-manipulation technology and will provide a promising tool for life science, chemistry and micro-assembly. [ABSTRACT FROM AUTHOR]

• The duplex mode tilt measurements can be realized at the single device. • ±90° large angle range tilt measurement is achieved. • The two-stage microleverage mechanisms are adopted to provide large force amplification. • The decoupling beams are employed to improve the structural compactness. • The proposed tilt sensor has high-performance of multi-function, high sensitivity and high resolution. This paper firstly reports the duplex mode tilt measurements (biaxial tilt measurement with small angle range and uniaxial tilt measurement with large angle range) based on a micro electromechanical system (MEMS) biaxial resonant accelerometer. For the accelerometer, two pairs of double-ended tuning fork (DETF) resonators are the sensing elements and they are integrated with a single proof mass. The two-stage microleverage mechanisms, possessing higher amplification factor, amplify and translate the weight component to the resonators. The adoption of decoupling beams lower the cross impact and allow the simultaneous differential measurement of tilt angles acting along two orthogonal axes. Based on the biaxial sensing structure, the biaxial tilt measurement is realized on the two orthogonal sensing axes. By the combination of the four DETFs resonant frequencies at each angular position, the linear range of uniaxial tilt measurement is extended. For the biaxial tilt measurement with small angle range, the experiments demonstrate a high sensitivity (X-axis: 4.351 Hz/deg and Y-axis: 5.257 Hz/deg) and a low cross-axis sensitivity (X-axis: 0.180 Hz/deg and Y-axis: 0.202 Hz/deg) for a ±40° biaxial tilt angle range. For the uniaxial tilt measurement with large angle range, the device shows an average sensitivity of 3.973 Hz/deg for a ±90° range. In addition, the close-loop self-oscillation is realized and the minimum Allan deviation of 68 ppb is obtained. The performance makes the device a potentially attractive option for compact, multi-functional and highly-sensitive tilt measurements. [ABSTRACT FROM AUTHOR]