Surface Profile Research Articles

Effect of static compression on near-field tsunami waves: Three-dimensional solution

An analytical solution of three-dimensional surface wave profiles due to arbitrary spatio-temporal disturbance of a circular ocean bottom in a compressible ocean is obtained by incorporating the influence of the static ocean background compression under the assumptions of linearized water wave theory. Time-domain simulations of the surface profile in three dimensions and the pressure distribution within the water column for a circular uniform rise and tilt are shown. The corresponding animation movies depict the temporal evolution of the surface profile and pressure field inside the water column eloquently, which was not shown in earlier literature. The impact of static compression is also discussed through the simulations. A novel analytical expression of the potential function for a generic tilted motion (rmcos(mθ),m∈Z) of the circular ocean floor is derived. An efficient numerical code is developed to find surface elevation and pressure distribution, implementing the inverse Fourier integral as matrix multiplication. Validation is performed for the specific case of a rising flat ocean floor, showing the oscillations due to acoustic-gravity modes. Initially, a simplified problem of a flat rising ocean bottom is solved using the eigenfunction matching method, which involves finding a particular solution for the nonhomogeneous ocean bottom condition and the solution for its homogeneous counterpart. Solutions are obtained using a newly developed inner product between the depth-dependent functions. Later, a Green function technique is used to incorporate the impact of the arbitrary spatio-temporal motion of the circular portion of the ocean bed. The solution obtained from the eigenfunction matching method is utilised to obtain the analytical form of Green’s function and, eventually, an expression of surface elevation and pressure distribution inside the ocean water column.

Fatigue life and behaviour of ribbed GFRP reinforced concrete beams

Despite the growing adoption of glass-fibre reinforced polymer (GFRP) as an alternative to steel reinforcement, there is limited research addressing the fatigue performance of GFRP bars in reinforced concrete structures. Existing literature presents contradictory experimental data and conclusions regarding the fatigue behaviour of GFRP rebars embedded in concrete. This study investigates the fatigue life of ribbed GFRP bars embedded in concrete beams through an experimental program, considering factors such as concrete strength and fatigue stress levels. Additionally, it introduces a testing protocol utilizing a displacement-controlled scheme to conduct fatigue testing, addressing many issues associated with force-controlled fatigue testing. Furthermore, the paper discusses cracking behaviour, deflection, and slippage, providing insights into the interaction between GFRP rebars and concrete under fatigue loading. The results of this study demonstrated that ribbed GFRP bars can withstand 2 million cycles of fatigue loading at a 40% stress ratio. The obtained fatigue life exceeds findings in existing literature, emphasizing the impact of stress ratio and bar surface profile on fatigue performance.

Dynamic response and roughness control of surface materials on TC4 titanium alloy subjected to laser shock wave planishing

Abstract In this study, ABAQUS was used to predict the dynamic response of surface materials on TC4 titanium alloy during laser shock wave planishing (LSWP). The experiments were conducted to evaluate the simulations. The results indicate that during the initial stage of LSWP, the contact status between the contact foil and the micro-protrusion changes from the one-dimensional stress state to the one-dimensional strain state. This causes the high-amplitude tensile residual stress to converge at the center of the flattened micro-protrusion surface. When treating specimens with high surface roughness, the application of a thin contact foil can significantly lower the height of micro-protrusions and lift the bottom of micro-depressions. This improves the plastic flow of micro-protrusions and prevents the convergence of tensile residual stress. Using a thick contact foil can help extend the pressure pulse duration and prevent the overall surface profile subsidence when treating specimens with lower surface roughness. The outcomes of the experiment and the simulation agree rather well. Additionally, a thick contact foil can reduce the build-up of tensile residual stress by reducing the contact pressure.

Increasing SAR Imaging Precision for Burden Surface Profile Jointly Using Low-Rank and Sparsity Priors

The synthetic aperture radar (SAR) imaging technique for a frequency-modulated continuous wave (FMCW) has attracted wide attention in the field of burden surface profile measurement. However, the imaging data are virtually under-sampled due to the severely restricted scan time, which prevents the antenna being exposed to high temperatures and heavy dust in the blast furnace (BF) for an extended period. In traditional SAR imaging algorithm research, the insufficient accumulation of scattered energy in reconstructing the burden surface profile leads to lower imaging precision, and the harsh smelting increases the probability of distortion in shape detection. In this study, to address these challenges, a novel rotating SAR imaging algorithm based on the constructed mechanical swing radar system is proposed. This algorithm is inspired by the low-rank property of the sampled signal matrix and the sparsity of burden surface profile images. First, the sparse FMCW signal is modeled, and the position transform matrix, calculated according to the BF dimensions, is embedded into the dictionary matrix. Then, the low-rank and sparsity priors are considered and reformulated as split variables in order to establish a convex optimization problem. Lastly, the augmented Lagrange multiplier (ALM) is employed to solve this problem under double constraints, and the imaging results are obtained using the alternating direction method of multipliers (ADMM). The experimental results demonstrate that, in the subsequent shape detection, the root mean square error (RMSE) is 15.38% lower than the previous algorithm and 15.63% lower under low signal-to-noise (SNR) conditions. In both enclosed and harsh environments, the proposed algorithm is able to achieve higher imaging precision even under high noise. It will be further optimized for speed and reliability, with plans to extend its application to 3D measurements in the future.

Tribo-Dynamic analysis of nano-enhanced palm blend lubricant for roller bearing application

Abstract Environmental concerns have led to an increase in the development of bio-lubricants during the last ten years. Many tribological studies address the findings of various types of bio-based lubricant performance derived from plant-based edible and non-edible oils in different operating conditions. However, those tribological tests were limited to workbench tribometers. In the present work, experimental investigations were carried out to evaluate the lubrication performance of functionalized multiwall carbon nanotubes (FMWCNTs) blended palm oil compared to mineral oil. The steel bearings are commonly used to minimize the effect of dynamic loads coming from the driven end in sliding / rolling conditions of the bearing. The wear severity on the bearing surfaces was examined using a Scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (EDX), 3D-optical profilometer results provided detailed information on surface profiles and roughness created on bearing surfaces under machine operating conditions. FFT-bearing vibration results were correlated with the surface degradation study of SEM analysis. Zeta-potential values reveal that the nanomaterial showed stable performance in the lubricant for 80 % of the total machine operating duration. Overall, experimental studies indicate that the tribological and vibration response of nanomaterial blended bio-oil lubricated bearing exhibited better results than that of mineral oil-lubricated bearing results.

A varifocal augmented reality head‐up display using Alvarez freeform lenses

AbstractA crucial requirement of augmented reality head‐up displays (AR‐HUDs) is continuously adjustable virtual image distance (VID), which allows adaptation to various depths in road environments and thereby avoids visual fatigue. However, usual varifocal components for near‐eye displays are unavailable because AR‐HUDs require the varifocal component's aperture to be larger than 10 cm. This study considers the Alvarez lenses, which change the optical power by in‐plane sliding two freeform lenses. Under the paraxial assumption, classic Alvarez lenses can create a quadratic wavefront profile, but the large aperture and extensive diopter variation range required by AR‐HUDs lead to significant aberrations. Thus, the classic paraxial Alvarez lens design is extended by co‐optimizing Alvarez lenses with high‐order surface profiles and a primary freeform mirror. Therefore, a novel varifocal AR‐HUD containing Alvarez lenses with apertures larger than 15 cm is proposed. The AR‐HUD generates a varifocal plane whose VID can be continuously adjusted between 2.5 and 7.5 m, and another focal plane with a fixed VID at 7.5 m. In addition, merely one display panel is used for compactness. Finally, an AR‐HUD prototype with a reduced volume of 9.8 L was built. The expected varifocal performance and qualified imaging quality were experimentally verified through the field of view, VID, and image sharpness.

Optimizing FDM process parameters: predictive insights through taguchi, regression, and neural networks

Abstract Fused deposition modelling (FDM) is a popular additive manufacturing process used for rapid prototyping and the production of complex geometries. Despite its popularity, FDM's susceptibility to variations in numerous process parameters can significantly impact the quality, design, functionality, and mechanical properties of 3D printed parts. This study explores thirteen FDM process parameters and their influence on the mechanical properties of polylactic acid (PLA) polymer, encompassing surface roughness, warpage, tensile and bending strength, elongation at break, deformation, and microhardness. The optimum parameters were identified alongside key contributors by applying the Taguchi method, signal-to-noise ratios, and analysis of variances (ANOVA). Notably, specific FDM parameters significantly affect the surface profile, with layer thickness contributing 32.65% and fan speed contributing 8.59% to the observed variations. Similarly, warping values show notable influence from nozzle temperature (29.53%), wall thickness (16.74%), layer thickness (16.56%), and retraction distance (12.80%). Tensile strength is primarily determined by wall thickness (31.83%), followed by infill percentage (26.73%) and infill pattern (16.18%). Elongation at break predominantly correlates with wall thickness (44.82%), with a supplementary contribution from nozzle temperature (10.90%). Microhardness lacks a dominant parameter. Bending strength variations primarily arise from layer thickness (38%), wall thickness (37.6%), and infill percentage (9.17%). Deformation tendencies are influenced by layer thickness (19.20%), print speed (11.37%), wall thickness, and fan speed (10.9% each). The optimized dataset of FDM process parameters was then employed in two prediction models: multiple-regression and artificial neural network (ANN). Evaluation based on the correlation coefficient (R2) and root mean squared error (RMSE) indicates that the ANN model outperforms the multiple-regression approach. The results indicate that precise control of FDM parameters, coupled with ANN predictions, facilitates the fabrication of 3D-printed parts with the desired mechanical characteristics.

Batch Specular Plane Flatness Measurements Based on Phase Measuring Deflectometry

Flatness is a critical parameter in the manufacturing industry, directly impacting the fit and overall product performance. As the efficiency of manufacturing continues to advance, there is an increasing demand for more accurate and efficient measurement techniques. Existing methods often struggle to strike a balance between precision and efficiency. In response, this article introduces a novel approach that is capable of achieving high-precision and rapid measurements concerning multiple surfaces. By enhancing the traditional phase measuring deflectometry (PMD) method, employing a matching technique based on polar lines and normal vector constraints to address discrete surface measurement challenges, and implementing a plane pre-positioning method to tackle low efficiency in binocular matching and solving, we successfully performed swift and synchronized measurements for a large batch of specular surfaces and obtained the three-dimensional surface profile of each measured surface. Through experimental validation, the method proposed in this paper can perform the batch measurement of specular planes while maintaining high measurement accuracy.

Chromatic confocal precision measurement accuracy analysis with surface roughness based on a scalar diffraction and raytracing hybrid model

Chromatic confocal sensors are widely used in surface inspection steps in precision machining. However, it is still a challenge to achieve optimum accuracy when measuring rough surfaces. Rough surfaces can lead to a deviation of several hundred nanometers in the measurement results, which is approximately twice the nominal measurement accuracy of the sensor. The wave optical model is commonly used to analyze the impact of surface roughness characteristics on the accuracy of chromatic confocal sensors. The model is computationally complex and highly dependent on the surface profile. In this paper, an improved model is proposed by combining the scalar diffraction and raytracing. Based on the generalized Harvey-shack (GHS) scattering theory and the masking effect function, the model reveals the relationship between the statistical parameters of rough surface and the error of spectral confocal signal. Based on this model, we find that the rough surface with the root mean square (RMS) roughness 0.01–0.3 μm introduces about 0.05–1 μm deviation in profile measurement. We further experimentally verified the effect of surface roughness on the spectral signals and proved the reliability of the analytical model. The model can be used as a theoretical basis for analyzing scattering phenomena caused by surface roughness and as a reference for sensor selection, design and data compensation for measuring rough surfaces using chromatic confocal sensors.

Effect of a subsurface void on the micromechanics of ductile metal indentation using remeshing

Near-surface voids and pores are generated in metal processing operations as diverse as additive manufacturing and powder processing, but their effect on indentation hardness has not been explored outside homogenized frameworks. Here we model the micromechanics of near-surface void deformation up to closure in a wedge-indentation field in ductile metal, and reveal the considerable softening effect of voids on the indentation hardness. Both symmetrically and eccentrically located voids, at various depths below the free surface, are studied. Notably, the extent of apparent reduction in the elastic modulus due to a void is much smaller than its effect on apparent hardness, e.g. 6.5% against 55% for the same void. Critical to the simulations is an adaptive remeshing finite element (FE) framework that allows accurate capture of processes like void closure and void-wall self-contact. The simulations reveal the subsurface plastic strain, strain-rate, and velocity fields with high fidelity, and their radical differences from the radial indentation field in a void-free specimen. These differences include the presence of localized pockets of high and low strain, and the initial accommodation of material displaced by the indenter by a corresponding reduction in void area. Unlike voids under uniform compression, the void-area evolution in indentation shows a characteristic sigmoidal pattern of reduction with indentation depth for all but the smallest voids. Interestingly, the indented surface profile can exhibit a one-sided pile-up feature which is diagnostic of the presence of an eccentrically located sub-surface void. Our remeshing scheme is versatile, as exemplified by its ability to model the extreme deformation associated with two nearly closed-spaced voids under an indenter. Our work shows that void-closure simulations in related applications like forming could benefit from the adoption of a remeshing framework.

A confocal measurement method for surface profile variations and shell thickness uniformity of hemispherical shell resonator

Here we present a confocal measurement method for the precise measurements of variations in the inner and outer surface profiles (IOSPs) and shell thickness uniformity (STU) of the hemispherical shell resonator (HSR). In this method, the unilateral-shift-subtracting confocal technique is applied to determine the focus of the sensor on the IOSPs of the HSR. The normal tracking technique is employed for measuring the outer surface, while the normal direction of the outer surface serves as the reference for measuring the inner surface, thereby enhancing the accuracy of relative position measurements for the HSR. Furthermore, we applied a trajectory-prediction method to narrow down the scanning range of the confocal sensor, which significantly improved the measurement efficiency. The experimental results showed that the repeated accuracies of the proposed methods are better than 40 nm for IOSP variations measurement and better than 50 nm for HSR STU measurement.

White light diffraction phase microscopy for imaging of red blood cells for different storage times

In this study, the effects of different storage times on the surface morphology of red blood cells (RBCs) were investigated using white light diffraction phase microscopy (WDPM). Blood samples collected from 10 volunteer and stored for 56 days, were imaged on WDPM at every 7 days without any sample preparation. To obtain the phase profiles of RCBs, first the sample and then the reference interferograms were obtained from the experimental setup. Then, surface profiles were calculated from these interferogram images using Fourier transform (FT). With the experiment performed every 7 days, 10 RBC phase information were obtained from each sample and surface profiles were created. From these profiles, 7 parameters related with RBC morphology (average cell thickness—ACT; mean corpuscular volume—MCV; projected surface area—PSA; total surface area—SA; diameter—D; mean corpuscular haemoglobin—MCH; surface area to volume ratio - SAV) have been calculated. Therefore, changes in the morphology of RBCs during storage were evaluated quantitatively. Additionally, phase calibration target was used to confirm the accuracy of our experimental setup system. From the interferogram images, the depth of the phase target (GRP 9 and element 3) was obtained as 309 nm, in accordance with the produced depth. By this way, the reliability of the WDPM setup is demonstrated. This study suggests that the morphology of RBCs can be quantitatively obtained in a reliable manner at higher resolution with WDPM without sample preparation.

Control of band-edge surface plasmons and their influences on photoluminescence of colloidal quantum dots on metal gratings

We holographically fabricated metal gratings demonstrating clear bandgaps and controlled resonances of band-edge surface plasmons (SP), and studied their influences on photoluminescence (PL) of colloidal quantum dots (cQDs) on the gratings. It is verified by numerical simulations that intrinsically existing but indiscernible bandgaps of SPs on sinusoidal metal gratings get distinctly open by introducing second harmonic components in their surface profiles. We elucidated roles of spatial harmonic components of the metal gratings on the bandgaps and their experimental manifestations. The band-edge SP resonance modes are shown to enhance PL of the cQDs and have the PL linearly polarized in direction parallel to grating vector. By systematically varying position of the bandgap relative to intrinsic PL peak of the cQDs, effects of the bandgap and band-edge SPs on PL of the cQDs in modifying the spectral profiles are demonstrated. It's also verified, by varying strength of coupling between the cQDs and the SP modes, that polarization of the PL is induced by the SPs, instead of selectivity of the gratings in diffractive coupling of the emitted photons in different polarization states. In additioin, it's interestingly found that excitation light coupled to the band-edge SPs can evidently improve linear polarization degree of the PL.

In-situ measurement of thermal expansion in Cu/SiO2 hybrid structures using atomic force microscopy at elevated temperatures

Thermal expansion of Cu plays a crucial role in the bonding mechanism of the Cu/SiO2 hybrid joints. In-situ heating atomic force microscopy (AFM) was employed to observe the evolution of surface topographies of Cu/SiO2 hybrid structures at various annealing temperatures. We found that the surface profile of the nanotwinned-Cu (NT-Cu) pad in SiO2 via exhibited a 6-nm recess at room temperature and shifted to a 4-nm protrusion at 200 ℃. The microstructural difference between NT-Cu and regular-Cu vias also influences their thermal expansion behaviors. The regular-Cu via has a larger expansion due to its smaller Young’s modulus. The changes in the surface profiles before and after annealing also demonstrate the plastic deformation of the Cu pads. The conservation of the Cu volume further indicates the migration of Cu atoms through creep mechanism at high temperatures, which results from the plastic deformation. This study provides a more comprehensive understanding with direct evidence of the Cu/SiO2 hybrid bonding mechanism.

Enhancement of in-vitro cellular structure morphology imaging using multiwavelength confocal endoscopic scanner

Optical imaging is crucial for cell examination, but its instruments' bulky optics limit their flexibility, and a single wavelength provides limited sample information. This paper presents a fibre cantilever-based endoscopic scanner for multiwavelength reflectance confocal microscopy. The scanner utilises the dual-core fibre cantilever to produce Lissajous scans while accommodating two distinct wavelengths. Coloured surfaces were imaged at wavelengths of 520 nm, 635 nm and 850 nm, and verified with a colour chart and reflectance spectroscopy. Blue ink-stained plant stem cross-section samples were also imaged and compared. Furthermore, the scanner performed structure morphology imaging on cellular samples. The 520 nm and 635 nm wavelengths create low- and high-contrast images respectively, while the 850 nm wavelength delivers a sharper image while also capturing the surface profile of the target sample. The findings demonstrated the endoscopic scanner’s capability to extract information based on different wavelengths, providing a more diverse view of the sample and enhancing the surface profile. Using 635 nm and 850 nm, the reconstructed images have a contrast enhancement of 67.9% and 90.8% respectively from 520 nm. The smallest feature size measured on the cellular sample is 5 µm. The endoscopic scanner has the potential to study microfluidic and cell morphology.

Freeform Liquid–Crystal Polarization Imaging Optics: A Practical Approach from Design to Fabrication

AbstractFreeform liquid–crystal polarization imaging optics (LPIOs) have vast potential for application in next‐generation interactive displays like augmented reality and virtual reality. However, tailoring the phase profile of a freeform LPIO for flexible aberration correction and diffraction efficiency control is still a big challenge due to the difficulties arising from the non‐zero étendue of an imaging system and the finite bandwidth of LPIOs. Here, a practical approach to creating freeform LPIOs from design to fabrication is proposed. A freeform polarization exposure is developed to produce a flexible, precise, and ultra‐high‐resolution photoalignment pattern for a freeform LPIO. A cooperative optimization is performed between the freeform LPIO and the freeform polarization exposure system to find the optimal phase of the freeform LPIO and the optimal surface profiles of the freeform lenses employed in the exposure system to produce freeform wavefronts. The optimal phase of the freeform LPIO is then achieved by superposition interference of the engineered freeform wavefronts via freeform polarization exposure. The effectiveness of the approach and the advantages of freeform LPIOs is experimentally demonstrated. The proposed approach will significantly promote the widespread applications of freeform LPIOs in the field of optics and photonics.

Super-resolution spectral interference fitting method for the simultaneous measurement of the thin film thickness and surface profile

Conventional spectral interferometry cannot measure film thicknesses less than optical resolution. However, none of the existing super-resolution methods can obtain the film thickness distribution and surface profile in a single measurement, which will seriously reduce the measurement efficiency and accuracy. We propose a fitting method for Linnik-type spectral interferometry to solve these problems. Compared to the traditional reflectance spectral model for thin films, a new spectral interferometric model is developed for measurements. The results obtained from this method were compared with those from ellipsometry and stylus profilometry, respectively. We confirmed the results matched each other well and proved the validity of the solution.

Inverse Designing Surface Curvatures by Deep Learning

Smooth and curved microstructural topologies found in nature—from soap films to trabecular bone—have inspired several mimetic design spaces for architected metamaterials and bio‐scaffolds. However, the design approaches so far are ad hoc, raising the challenge: how to systematically and efficiently inverse design such artificial microstructures with targeted topological features? Herein, surface curvature is explored as a design modality and a deep learning framework is presented to produce topologies with as‐desired curvature profiles. The inverse design framework can generalize to diverse topological features such as tubular, membranous, and particulate features. Moreover, successful generalization beyond both the design and data space is demonstrated by inverse designing topologies that mimic the curvature profile of trabecular bone, spinodoid topologies, and periodic nodal surfaces for application in bio‐scaffolds and implants. Lastly, curvature and mechanics are bridged by showing how topological curvature can be designed to promote mechanically beneficial stretching‐dominated deformation over bending‐dominated deformation.

Application of 3D Imaging for Analyzing the Chip Groove Shapes of Cutting Inserts

An effective chip formation process is significant for an efficient metal-cutting process. Long continuous chips can lead to scratches on the machined surface, increasing the risk to operator safety and stability of the machining process. The use of chip grooves on cutting inserts allows for control of the chip formation and breaking process during machining. The shape of the rake surface and the design of the chip groove also affect the efficiency of the machining process. The article presents the use of 3D imaging to analyze changes in the selected chip groove shapes depending on the cutting depth ap = 0.10, 0.25, and 0.50 mm and the angular location of the cutting insert relative to the machined surface of the workpiece (i.e., major cutting-edge angle Ƙ = 60° and Ƙ = 90°). The analysis methodology was based on the use of 3D image registration and surface shape modeling. In the analysis based on the 3D imaging presented, the novelty was the adaptation of methods typically used to map and model the terrain surface, which have not been used previously in cutting processes. The evaluation of the shape of the chip groove surface was carried out using, e.g., watershed maps and 3D surface maps. The obtained results indicated a significant influence of the cutting depth and major cutting-edge angle on the surface shape, profile, and length of the chip former; chip groove volume; and the theoretical contact area of the formed chip with the cutting insert. It was observed that for small depths of cut, i.e., ap < 0.25 mm, the chip-curling process may be difficult due to the flattened shape of the rake surface. In addition, the influence of the convexity of the rake surface of the cutting insert on the chip formation process was demonstrated. The results of the experimental research that verified the conclusions are presented. The developed results may be useful in the process of selecting the parameters and conditions of the metal finishing through use of tools with a shaped rake surface.

A Sharp Version of the Benjamin and Lighthill Conjecture for Steady Waves with Vorticity

We give a complete proof of the classical Benjamin and Lighthill conjecture for arbitrary two-dimensional steady water waves with vorticity. We show that the flow force constant of an arbitrary smooth solution is bounded by the flow force constants for the corresponding conjugate laminar flows. We prove these inequalities without any assumptions on the geometry of the surface profile and put no restrictions on the wave amplitude. Furthermore, we give a complete description of all cases when the equalities can occur. In particular, that excludes the existence of one-sided bores and multi-hump solitary waves. Our conclusions are new already for Stokes waves with a constant vorticity, while the case of equalities is new even in the classical setting of irrotational waves.