Three-dimensional Surface Topography Research Articles

Large-area surface topography analysis of additively manufactured metallic materials using directional reflectance microscopy

The surface topography of additively manufactured metals carries valuable information about the mechanisms involved during materials formation. As such, it may be used as an indirect measure of materials quality, both during and after production. Standard surface analysis techniques, however, are characterized by narrow field of view and low data acquisition rate, making them unsuited to rapidly characterize large areas. In this work, we describe a novel method to quantify the three-dimensional surface topography of a 1 cm3 metal sample produced by selective laser melting. The method relies on directional reflectance microscopy—an optical technique that quantifies surface reflectance as a function of the illumination angle. By fitting the directional reflectance measurements with a reflection model, we map the surface normal orientation and microscopic surface roughness over the entire sample surface at a spatial resolution of ~5.3μm. We also discuss the possibility of integrating our method within the additive process by reducing the number of measurements required to reconstruct surface topography. Because of the inexpensive equipment employed, the large field of view measurements, and rapid data acquisition speed, we believe that our method is a competitive alternative for analysing the surface topography—and thus the quality—of additively manufactured metals both during and after production.

Measurement and Analysis of the Stepwise Curved Surface of Diffractive Optical Elements by a Constant Speed Confocal Probe

Diffractive optical elements (DOEs) play an important role in improving imaging quality and reducing system volume. The measurement of DOE surface topography is of great significance to the evaluation of DOE quality and the optimization of its manufacturing process. However, there are still some difficulties in measuring the large curvature and the large sag of curve-based DOEs. In this paper, considering the geometrical feature information and measurement problems of curve-based DOEs, a measurement method based on a confocal measurement principle for DOE measurement is proposed. The proposed measurement data processing method is verified by a high-precision motion axis system and the stability of an ultra-precision lathe. The results show that the proposed measurement method can reconstruct and accurately evaluate the three-dimensional surface topography of DOEs.

A comprehensive investigation of surface generation and material removal characteristics in ultrasonic vibration assisted grinding

Ultrasonic vibration assisted grinding (UVAG) has been proved to be superior in improved machining quality and reduced surface roughness compared with conventional grinding (CG), but its mechanism is still in constant research and understanding. Except for the imposed axial vibration, another much smaller radial vibration is generated due to Poisson effect at the same time, which has different effect on the surface generation. In this paper, a comprehensive simulation model of UVAG considering Poisson effect has been developed to predict the three-dimensional surface topography and calculate the parameters (undeformed chip thickness, dynamic active grain number) which could reflect the characteristics of corresponding material removal process. The comparison between experimental results and simulated results shows that the method proposed in this paper is in good agreement with the experimental results. The imposed axial vibration can increase dynamic active grain number, generate uniform undeformed chip thickness and reduce the surface roughness, while the additional radial vibration causes the fluctuation of undeformed chip thickness and the increase of surface roughness. The proposed simulation model of UVAG provides a new approach to the prediction of the ultrasonic surface topography and understanding of material removal process as well as the optimization of the UVAG.

Study on crater depth during material removal in WEDC of Ni-rich nickel–titanium shape memory alloy

The objective of this experimental investigation is to reveal the individual effect of wire electrical discharge cutting (WEDC) process parameters, namely discharge energy density, wire feed rate, spark frequency, wire tension, and spark gap voltage on average crater depth, material removal rate (MRR), and metallographic changes of Ni55.95Ti44.05 shape memory alloy (SMA). The analysis of crater size during material removal in WEDC has been also discussed in this study. The three-dimensional surface topography at higher discharge energy density divulges the formation of deeper and wider craters with high surface roughness on the machined surface compared to lower discharge energy density. MRR and average crater depth increase with the increase in discharge energy density and decrease with the increase in spark frequency and spark gap voltage, whereas wire feed rate and wire tension have the trivial effect. The analysis of X-ray diffraction peaks of the machined surface shows the presence of various compounds such as NiTi, TiO, TiO2, Ni4Ti3, CuZn, Cu2NiZn, NiTiO3, and NiZn and tensile residual stress.

Friction performance of DLC film textured surface of high pressure dry gas sealing ring

After applying the diamond-like carbon (DLC) coating and surface micro-texturing into dry gas seal, the friction performance of textured surface DLC film of high pressure dry gas sealing ring has been researched in this paper. Firstly, the variation curves of friction coefficient with different load, rotation speed, and micro-texture geometric parameters are measured by using end-face friction and wear experiment machine (HDM20) under dry friction condition. Secondly, in order to compare the wear condition, the surface morphology of pretest and posttest is analyzed by using three-dimensional non-contact surface topography instrument (ST400). The experiment results show that: (1) The seal face which exists micro-textured DLC film has low friction coefficient, (2) under the same condition of micro-textured parameters, the friction coefficient would decrease with the increase in the load and would decrease firstly and then increase with the increase in the rotation speed, and (3) under the same running condition, the friction coefficient would decrease with the diameter of micro-pit and would increase with the increase in the density of textured area; however, the changing degree of friction coefficient would decrease. The experiment results could provide foundation for researching the tribological characteristics of faces of dry gas seal and optimizing the micro-textured structure.

A profile-adaptive compliant polishing tool for aero-engine blade finishing process

As a key role in the precision finishing of aero-engine parts, polishing tools strongly affect the surface quality of finished parts. In this paper, a novel profile-adaptive compliant polishing tool with a controlled and movable sleeve was developed for aero-engine blade finishing process. The profile of the polishing tool’s end can be changed to fit well with the profile of workpiece surface by adjusting the tool’s rotational speed and the length of its protrusion. The control and implementation of the profile-adaptive polishing for aero-engine blades was proposed. Then, the approximate curvature prediction model of polishing tool’s end was experimentally established. Finally, polishing experiments with the unimproved polishing tool and the proposed compliant polishing tool were carried out for TC4 aero-engine blades. Through comparing and analyzing the measurement results of surface texture, three-dimensional surface topography, and surface roughness, the feasibility and effectiveness of the proposed profile-adaptive compliant polishing tool for aero-engine blade finishing process were proved.

Investigations of the Adhesive Contact Behavior of Elastic Layered Media With Surface Roughness

A deterministic adhesive model for the contact between an elastic layered medium with surface roughness and a smooth elastic microsphere was developed on the basis of the Lennard–Jones surface force law. Through numerical simulations, the adhesive contact behavior of the layered medium with the measured three-dimensional (3D) surface topography was comparatively analyzed with that of the homogeneous medium. Furthermore, the contact characteristics of the layered medium with pre-assigned roughness parameters were investigated with the aid of a computer-generated technique for simulating surface roughness. Results showed that the pull-off force for the contact problem involving rough surfaces was influenced by the contact location, and the average value for the contact between an alumina (SiO2) microsphere and a diamond-like carbon/silicon (DLC/Si)-layered medium was smaller than that for the contact between a SiO2 microsphere and a Si homogeneous half-space. In addition, the effect of the diamond-like carbon (DLC) layer on reducing adhesion was smaller than that of the surface roughness. Finally, the average pull-off force for a DLC/Si-layered medium with computer-generated surface roughness rapidly decreased; however, it eventually became almost unchangeable with the increase in the root-mean-square (RMS) deviation.

Effect of grinding depth on surface topography by considering vibrations and a force prediction model

Little consideration has been given to vibrations when the effect of grinding process parameters on the surface morphology is studied. Taking a grinding force as the intermediate variable, influences of grinding depths on the surface topography are investigated with considering vibrations in this paper. Firstly, a novel grinding force prediction model is proposed through amending the Malkin model by integrating with contact arc length and abrasive grain contact angle. Secondly, vibrations of the feed platform and the grinding wheel shaft are analysed. Vibration displacement in the x-direction of wheel axis remains substantially between 140-150 nm, while in the y-direction, it increases with the grinding depth. Finally, three-dimensional surface topographies with different grinding depths are investigated. It is observed that the pronounced defects and a coarse texture are generated as the grinding depth increases. Parameters like Sa, Sq, Sku, Ssk are more suitable to represent the real grinding quality of workpiece surface.

Effect of grinding depth on surface topography by considering vibrations and a force prediction model

Little consideration has been given to vibrations when the effect of grinding process parameters on the surface morphology is studied. Taking a grinding force as the intermediate variable, influences of grinding depths on the surface topography are investigated with considering vibrations in this paper. Firstly, a novel grinding force prediction model is proposed through amending the Malkin model by integrating with contact arc length and abrasive grain contact angle. Secondly, vibrations of the feed platform and the grinding wheel shaft are analysed. Vibration displacement in the x-direction of wheel axis remains substantially between 140-150 nm, while in the y-direction, it increases with the grinding depth. Finally, three-dimensional surface topographies with different grinding depths are investigated. It is observed that the pronounced defects and a coarse texture are generated as the grinding depth increases. Parameters like Sa, Sq, Sku, Ssk are more suitable to represent the real grinding quality of workpiece surface.

Characterization of surface texture in electropolishing processes using 3D surface topography parameters

Surface engineering requires new technology for the evaluation of surface texture. Profiling methods for the characterization of surface finish do not permit the detailed analysis of surface microgeometry. Thus, advances in the field of surface metrology have led to the development of topographic profilometer systems capable of the three-dimensional topographical reconstruction of real surface texture using phase shift scanning of surfaces, with instruments able to measure microgeometric form, waviness, and roughness, individually or integrated. The innovative three-dimensional evaluation methods, using contact and non-contact technology, enable the virtual reconstruction of surfaces for the evaluation of area roughness parameters, three-dimensional topographic maps with color scale, and profiling of sections in any area of a surface to provide the two-dimensional roughness parameters, among others. In this study a set of 3D surface parameters were analyzed: fractal analysis, area roughness parameters (Sa, Sz, and Spd), and three-dimensional surface topography, in order to determine the information provided by each in the analysis of surface texture. The topographic analysis performed detected deformations on the borders of the workpieces when high electropolishing times and current densities were combined, due to the lack of homogeneity in the elimination of the treated surface material. Finally, this study has determined electropolishing conditions and electrolytic effects on surface texture using the three-dimensional analysis of surface texture.

Effects of Micro-Textured Polystyrene Substrates by Compression Molding on Cell Adhesion and Proliferation

Surface chemistry and micro-nanoscale topography of biomaterials can significantly influence tissue engineering and cell biology. In this study, polystyrene (PS) Petri dishes were subjected to microtexturing by compression molding process, which resulted in three-dimensional (3D) microscale surface topographies. Three different micropatterned surfaces were fabricated using bronze sintered molds with different mean pore pitch sizes. The surface changes and the morphological aspects were analyzed by 3D surface analyzer. The dishes were then used to investigate the cell behavior of Mouse Embryonic Fibroblasts (MEF) P4 cells. The surface micropatterning have affected in different ways the MEF cell adhesion and proliferation, related to the morphological changes in comparison with unmodified PS. At the increasing of the sintered particle dimensions of the mold, the cavities dimensions on the molded Petri increase and also the cells adhesion in the cavities seems to increase independently from the roughness inside them.

Effects of crystallographic orientation and negative rake angle on the brittle-ductile transition and subsurface deformation in machining of monocrystalline germanium

In this study, taper cutting experiments using a diamond tool were conducted to investigate the effects of negative rake angle and cutting orientation on the brittle-ductile transition and subsurface deformation of monocrystalline germanium cut on the (100), (101), and (111) planes. Confocal laser scanning microscopy and Raman spectroscopy were used to observe the three-dimensional surface topographies of the samples and characterize the subsurface deformation, respectively. The results showed that the negative rake angle and crystallographic orientation have a significant effect on the brittle-ductile transition and subsurface deformation mechanisms in ductile regime machining of monocrystalline germanium. A large negative rake angle alters the initial surface crack patterns, as well as anisotropic behavior of the ductile-brittle transition and subsurface deformation of monocrystalline germanium.

Tribological Behavior of Electrochemically Etched AISI 316 Stainless Steel with a Textured Surface

In this work, AISI 316 stainless steel (316 SS) was electrochemically etched in four NaCl solutions (10, 15, 20, and 25 wt.%) to form textured surfaces. Surface morphologies, three-dimensional surface topographies, and surface profiles of the textured 316 SS samples were obtained by scanning electron microscopy (SEM) and laser scanning confocal microscope (LSCM). Sliding friction tests of the textured 316 SS samples were conducted in air and under grease lubrication. The results suggested that the variable degrees of microtextured surfaces after electrochemical etching in 10, 15, and 20 wt.% NaCl solutions. The 316 SS samples etched in 15 and 20 wt.% NaCl solutions showed more promising tribological performance than other samples, as reflected by their friction coefficients, mass loss per unit distance traveled (mg/m), and wear morphologies.

Temporal-spatial resolved laser-induced breakdown spectroscopy of T91 steel of different aging grades

As a representative heatproof martensitic steel, T91 steel is extensively used for building industrial pressure-bearing heat-exchange surface. The mechanical properties and metallographic structure of the steel components will gradually change in long-term operation (also known as material aging). It will seriously endanger the operation safety and reduce the lifespan of the equipment. In this study, in order to deeply understand the mechanism of steel degradation surface measurement by laser-induced breakdown spectroscopy (LIBS), the temporal-spatial evolutions of spectral line emissions of T91 steel specimens with different aging grades were observed by using grating spectrometer with intensified charge coupled device detector (ICCD). The time-resolved line intensity ratios of ionic to atomic and matrix element to alloying element of specimens with different aging grade were investigated. Besides, the time-resolved plasma temperatures of different specimens were studied. And the three-dimensional surface topographies of ablated craters of specimens with different aging grades were analyzed. The study results show that the line emissions are located at greater height above surface for the specimen with lower steel aging grade during the early stage of the plasma expansion (300–700 ns delay time). The integrated line intensities which are close to the specimen surface (at≈0–500 μm above specimen surface) increase with the increase of steel aging grade during 300–700 ns delay time. The line intensity ratios are correlated with the steel aging grade at specific height above specimen surface during 500–700 ns delay time, and these correlations are sensitive to the delay time and observation distance from specimen surface. In addition, it was found that the plasma temperatures of specimens with lower aging grades are higher during 300–700 ns delay time. And the depth and volume of ablated crater increase with the increase of the steel aging grade. The investigations create a better understanding of physical mechanism in LIBS steel degradation analysis, and provide a good reference for practical measurement.

Advanced damage detection techniques in historical buildings using digital photogrammetry and 3D surface anlysis

Abstract In the last twenty years, advances in technology led to a progressive digitalization in photography and photogrammetry and to the development of a considerable number of image processing software. In several fields, Digital Image Processing techniques began to spread. For example, in Civil Engineering there are many methodologies for the monitoring of reinforced concrete structures or road pavements. In most cases they involve the application of mathematical and morphological filters to two-dimensional images, to obtain quantitative information about the decay of the analyzed structures. Instead in Architectural Restoration there are still few researches focused on these methodologies, because of the great complexity and uniqueness of historical buildings. Furthermore, until now architectural photogrammetry mainly concerned geometric survey and it was not widely used to diagnose the presence of alterations on buildings, despite the great potential of a non-invasive, contactless survey technique. Therefore, the aim of this research is to create an analysis approach, to detect damages on three-dimensional models, richer in information about depth and volume. The analysis can be carried out through a specific set of spatial and morphological filters for advanced surface analysis, adopting software tools mostly used for three-dimensional metrology and surface topography. A sequence of operations can be executed, allowing to obtain quantitative information about some kinds of alterations (cracks or features induced by material loss) from three-dimensional models like point clouds or polygonal meshes. The procedure was tested and validated on a case study (Palazzo Palmieri, Monopoli – Italy). The result of the research is a low interaction approach, through which it is possible to identify and quantify damages on the surfaces.

Study on the extraction and reconstruction of arbitrary frequency topography from precision machined surfaces

This article presents an extraction and reconstruction method for arbitrary two-dimensional and three-dimensional frequency features in precision machined surfaces. A combination of power spectrum density and continuous wavelet transform is used to analyze the potassium dihydrogen phosphate crystal surface topography. All frequencies involved in sampling area of measuring instrument are distinguished by power spectrum density method. Compared to discrete wavelet transform used to decompose frequency features, continuous wavelet transform method can extract and reconstruct two-dimensional profile and three-dimensional topography of arbitrary frequency features from original precision machined surfaces. Analysis results show that amplitude and distribution of different frequency features in two-dimensional profile or three-dimensional surface topography are fully restored by continuous wavelet transform. The effects of different factors in machining process on precision machined surface topography may be discovered. Furthermore, the extraction and reconstruction method is generally applicable for the analysis of all precision machined surfaces.

Leakage Monitoring in Static Sealing Interface Based on Three Dimensional Surface Topography Indicator

Leakage directly affects the functional behavior of a product in engineering practice, and surface topography is one of the main factors in static seal to prevent leakage. This paper aims at monitoring the leakage in static sealing interface, using three-dimensional (3D) surface topography as an indicator. The 3D surface is measured by a high definition metrology (HDM) instrument that can generate millions of data points representing the entire surface. The monitoring approach proposes a series of novel surface leakage parameters including virtual gasket, contact area percentage (CAP), void volume (VV), and relative void volume (SWvoid) as indicators. An individual control chart is adopted to monitor the leakage surface of the successive machining process. Meantime, based on the Persson contact mechanics and percolation theory, the threshold of leakage parameter is found using finite element modeling (FEM). Experimental results indicate that the proposed monitoring method is valid to precontrol the machining process and prevent leakage occurring.

Multifractal analysis of three-dimensional surface topographies of GCr15 steel and H70 brass during wear process

The variation of three-dimensional topographies of GCr15 steel and H70 brass during wear process was studied by multifractal method. A multi-stage test method was proposed to obtain the worn surfaces of friction pair at different wear time. The tests were performed on a ring-on-disc tribometer. The three-dimensional (3D) topographies of ring and disc were measured by laser confocal microscopy. Box-counting method was applied to compute multifractal spectrum, spectrum width Δα and spectrum difference Δf(α) of counter surfaces. All the spectra of mating surfaces are presented as parabolic curve, which indicates that the worn surfaces have the characteristics of multifractal. The Δα and Δf(α) of disc surfaces decrease at first, then stabilize at a small value and finally increase rapidly. Those of ring surfaces increase at first, then maintain at a small value and finally increase gradually. The multifractal study of 3D surface topographies reveals the singularity and nonlinear behavior of the friction system.

Quasicommon-path digital holographic microscopy with phase aberration compensation based on a long-working distance objective

We present a quasicommon-path digital holographic microscopy with phase aberration compensation, which is based on a long-working distance objective and can be used for the quantitative characterization of microstructure specimens. The quasicommon-path arrangement makes the holographic system very compact and stable. Meanwhile, the object and reference beams all travel along the same path, which can effectively eliminate the system aberration, and the mirror in the reference arm can be adjusted precisely for the phase tilt compensation. In the experiment, a wafer with orderly patterns and unified height of 180 nm is measured, and its three-dimensional surface topography is obtained. A long-term system stability of 1.39 nm is achieved in measurement with the proposed method.

A loading fractal prediction model developed for dry-friction rough joint surfaces considering elastic–plastic contact

In the microscopic view, the contact between two solid surfaces is reckoned to be the contact among asperities indeed. These asperities loaded which contact with each other are to experience three stages of deformation in succession: elastic deformation, elastic–plastic deformation, and plastic deformation, not the direct transition from elastic deformation to plastic deformation. In addition, these asperities should be distributed on the three-dimensional surface topography, and the corresponding fractal dimension is $$2<D<3$$ . In this study, firstly, based on the fractal theory and Hertz contact theory, the loading fractal model of rough dry-friction joint surfaces is established in consideration of elastic–plastic deformation of asperities and three-dimensional surface topography. Secondly, two important fractal parameters, fractal dimension D and fractal roughness G, can be calculated according to sampled surface topography of 45 steel and power spectrum density function method. Then, the effects of friction factor $$\mu $$ , fractal dimension D, and fractal roughness G on the loading fractal model are analyzed by numerical simulation. Finally, the present model is compared with experimental data and other models, which indicates that their trends are the same. The elastic–plastic loading modeling provides a certain theoretical reference for the accurate solution of contact among rough surfaces.