Geometric Surface Research Articles

Smooth Mixed-Geometry Transitions in Water-Supply Canals

AbstractFifth-degree parametric equations were developed to calculate the cross-sectional dimensions and bed centerline elevations (thus, the geometric surface coordinates) between the two ends of ...

Surface Qualification Toolpath Optimization for Hybrid Manufacturing

Hybrid manufacturing machine tools have great potential to revolutionize manufacturing by combining both additive manufacturing (AM) and subtractive manufacturing (SM) processes on the same machine tool. A prominent issue that can occur when going from AM to SM is that the SM process toolpath does not account for geometric discrepancies caused by the previous AM step, which leads to increased production times and tool wear, particularly when wire-based directed energy deposition (DED) is used as the AM process. This work discusses a methodology for approximating a part’s surface topology using on-machine contact probing and formulating an optimized SM toolpath using the surface topology approximation. Three different geometric surface approximations were used: triangular, trapezoidal, and a hybrid of both. SM toolpaths were created using each geometric approximation and assessed according to three objectives: reducing total machining time, reducing surface roughness, and reducing cutting force. Different prioritization scenarios of the optimization goals were also investigated. The optimal surface approximation that yielded the most improvement in the optimization was determined to be the hybrid surface topology approximation. Furthermore, it was shown that when the machining time or cutting force optimization goals were prioritized, there was little improvement in the other optimization goals.

Post-Processing of 3D-Printed Polymers

Additive manufacturing, commonly known as 3D printing, is an advancement over traditional formative manufacturing methods. It can increase efficiency in manufacturing operations highlighting advantages such as rapid prototyping, reduction of waste, reduction of manufacturing time and cost, and increased flexibility in a production setting. The additive manufacturing (AM) process consists of five steps: (1) preparation of 3D models for printing (designing the part/object), (2) conversion to STL file, (3) slicing and setting of 3D printing parameters, (4) actual printing, and (5) finishing/post-processing methods. Very often, the 3D printed part is sufficient by itself without further post-printing processing. However, many applications still require some forms of post-processing, especially those for industrial applications. This review focuses on the importance of different finishing/post-processing methods for 3D-printed polymers. Different 3D printing technologies and materials are considered in presenting the authors’ perspective. The advantages and disadvantages of using these methods are also discussed together with the cost and time in doing the post-processing activities. Lastly, this review also includes discussions on the enhancement of properties such as electrical, mechanical, and chemical, and other characteristics such as geometrical precision, durability, surface properties, and aesthetic value with post-printing processing. Future perspectives is also provided towards the end of this review.

A new organotellurium compounds based on camphor, aniline and p-toluidine: preparation, characterization and theoretical study

The present study involved the preparation of organomercury and organotellurium compounds derived from camphor and (2-amino-5-methylphenyl) mercury (II) chloride and their derivatives by a condensation reaction. Characterization of the studied compounds was carried out using infrared spectrum (IR), proton nuclear magnetic resonance spectrum (1H NMR), and elemental analysis (C.H.N). The molecular structure of the organotellurium compounds was investigated using the density functional theory with hybrid functional (B3LYP) and the basis set 3-21G. Geometrical structure, HOMO surfaces, LUMO surfaces, and energy gap have been produced throughout the geometry optimization. The molecular geometry and contours for the organotellurium compounds were investigated throughout the geometrical optimization. The donor and acceptor properties have been studied by comparing the highest occupied molecular orbital energies (HOMO) of organotellurium compounds. The electronegativity, electrophilicity, Ionization potential, electron affinity, Chemical Hardness, and Chemical softness for the organotellurium compounds was calculated for the molecules under the study.

Recent Progress on ZnO Nanowires Cold Cathode and Its Applications.

A cold cathode has many applications in high frequency and high power electronic devices, X-ray source, vacuum microelectronic devices and vacuum nanoelectronic devices. After decades of exploration on the cold cathode materials, ZnO nanowire has been regarded as one of the most promising candidates, in particular for large area field emitter arrays (FEAs). Numerous works on the fundamental field emission properties of ZnO nanowire, as well as demonstrations of varieties of large area vacuum microelectronic applications, have been reported. Moreover, techniques such as modifying the geometrical structure, surface decoration and element doping were also proposed for optimizing the field emissions. This paper aims to provide a comprehensive review on recent progress on the ZnO nanowire cold cathode and its applications. We will begin with a brief introduction on the synthesis methods and discuss their advantages/disadvantages for cold cathode applications. After that, the field emission properties, mechanism and optimization will be introduced in detail. Then, the development for applications of large-area ZnO nanowire FEAs will also be covered. Finally, some future perspectives are provided.

Reversible Dendritic-Crystal-Reinforced Polymer Gel for Bioinspired Adaptable Adhesive.

High-strength and reversible adhesion technology, which is a universal phenomenon in nature but remains challenging for artificial synthesis, is essential for the development of modern science. Existing adhesive designs without interface versatility hinder their application to arbitrary surfaces. Bioinspired by creeper suckers, a crystal-fiber reinforced polymer gel adhesive with ultrastrong adhesion strength and universal interface adaptability is creatively prepared via introducing a room-temperature crystallizable solvent into the polymer network. The gel adhesive formed by hydrogen bonding interaction between crystal fibers and polymer network can successfully realize over 9.82MPa reversible adhesion strength for rough interface and 406.87 J m-2 peeling toughness for skin tissue. In situ anchoring is achieved for adapting to different geometrical surfaces. The adhesion performance can be significantly improved with the further increase of the interfacial roughness and hydrophilicity, whose dissipation mechanism is simulated by finite element analysis. The melting-crystallization equilibrium of the crystal fibers is proved by synchrotron radiation scattering. Accordingly, reversible phase-transition triggered by light and heat can realize the controlled adhere-detach recycle. Later adjustments to the monomers or crystals are expected to broaden its applications to various fields such as bioelectronics, electronic processing, and machine handling.

Transfer method of geometric tolerance items based on assembly joints

In order to reduce the uncertainty in the selection of geometric tolerance items, a qualitative method for top-down transfer of geometric tolerance items is proposed. The assembly joint which is composed of two mating surfaces with functional requirements or structural constraints is acted as the basis of geometric tolerance items transmission. According to the structural characteristics, the assembly joints are divided into meta-assembly joints and composite assembly joints, and the priority rules for assembly joints are proposed. The transfer path of part-level geometric tolerance items is established according to the functional requirements and structural constraints among parts. On this basis, by adding information about the composition and constraint types of assembly joints between parts and the position constraint relationship of the general structure surface in the part, the transfer path of part-level geometric tolerance items is extended to the transfer path of geometric feature surface-level. With the development of product design, the initial functional requirements will be transformed into structural constraints between parts and geometric feature surfaces, and the structural transformation model of functional requirements is constructed. The generation specifications of geometric tolerance items based on structural constraints and the transfer specifications of datums are established. And based on the above specifications, the mapping relationship between functional requirements, structural constraints, and geometric tolerance items is defined. The synchronous transmission of geometric tolerance items along with the product design process are realized which provides an effective analysis tool for the top-down design of geometric tolerance items. Finally, the effectiveness of the method is verified by taking the transmission parts and connection parts in the crankshaft-piston mechanism as an example.

ABSOLUTE 3D ACCURACY ASSESSMENT OF UAS LIDAR SURVEYING

Abstract. Surveying an area with small, unoccupied aerial systems (UAS) equipped with a lidar mapping payload—absent permanent, stable, geometrical reference surfaces—demands accurate, repeatable data collection procedures. While relative error within a single UAS lidar dataset may reveal itself in strip misalignment, absolute error (particularly horizontal error) can prove more difficult to detect, casting doubt upon the quality of both individual surveys and time change analyses of multiple surveys of the area. To gain insight on the UAS lidar error budget, this study presents an analysis of multiple UAS lidar surveys over a set of accurately surveyed geometric checkpoints. Each flight’s trajectory was processed multiple times using multiple static GNSS base observations, both autonomous and set over surveyed monuments, at varying distances from the study site. Custom algorithms were used to mensurate the geometric targets detected in each UAS lidar survey's point cloud, allowing for precise comparison of both absolute horizontal and vertical accuracy of each survey against the rigorous ground survey. The results of the analysis suggest that high horizontal accuracy can be achieved under a variety of conditions, whereas vertical accuracy is sensitive to the quality of ground control. and a discussion of the results explores the ultimate goal of isolating and understanding the sources and magnitudes of error in the UAS lidar error budget.

Analysis of Assembly Tolerance Based on Assembly Constraint Information Model

Mechanical products are composed of two or more parts. The geometric tolerance and dimensional tolerance of each feature in part will affect the assembly performance of the product, which are accumulated and propagated between assembly fit and parts. In this paper, through the secondary development of CAD software, the B-rep model of parts is obtained. The model information is decomposed and simplified based on geometric features to obtain the key information of parts in the assembly process, simplify the operation, and improve the accuracy. Through a directed graph network, the transmission model of assembly error information based on geometrical and dimensional tolerances (GD&T) on the surface of parts is established. Combined with the error transfer characteristics of different geometric surfaces and different error sources, guided by the breadth-first search algorithm and the shortest path theory, the search and establishment of a three-dimensional assembly chain are realized. Finally, the three-dimensional chain is simulated by the Monte Carlo method. The calculation results are compared with the error range obtained by the traditional method to prove the effectiveness of the method.

Formation and evolution of fracture spacing on various geometric surfaces in layered materials

Fracture spacing as a widespread phenomenon in nature shows similar patterns on various geometric surfaces. To explore the similarities and differences between various geometric surfaces in the process of fracture spacing formation, numerical simulations are conducted on bi-layered three-dimensional models of three various geometric surfaces, including slab surface, cylindrical surface, and spherical surface by the finite element method (FEM). The fractures develop under a quasi-static loading condition with constant displacement increments. The progressive failure process from fracture initiation to saturation is researched, and the material heterogeneity is introduced by using a probability distribution, which acts as the main reason for failures generating randomly inception. An intuitive explanation is also provided for the phenomenon of fracture saturation. Then, as the loading condition varies, fracture patterns in both slab surface models and cylindrical surface models show a transition from parallel fractures, step-like fractures to regular polygonal fractures. However, in spherical surface models, only uniform polygonal fractures emerge under the condition of radial expansion. Furthermore, through quantitative analysis by statistical means, we find that, except for the fractured layer thickness, curvature also has a significant impact on the crack density.

Toward controlled geometric structure and surface property heterogeneities of TiO2 for lipase immobilization

To effectively immobilize an enzyme while maintaining its high activity and stability, the design of supports with controlled geometric structures and heterogeneous surface properties is desirable. Towards this goal, heterogeneous titanium dioxide (TiO2) surfaces with controlled pore sizes were synthesized in this study and used to efficiently immobilize lipase. The immobilized lipase activity increased by a factor of 1.31 with an increase in the TiO2 pore size from 11.46 to 21.14 nm. The highest protein loading of 15.52 mg/g was achieved in ethenyl triethoxy silane (ETS)-modified TiO2 (E-P25) after immobilizing the enzymes at 30 ℃, pH 7.33 for 3 h and using a protein concentration in solution of 0.176 mg/mL. Among the different surface functionalities, the highest activity yield of 428.04 % was accomplished by using TiO2 calcinated at 650 ℃ and modified by ETS as immobilization support. The immobilized enzymes showed excellent storage stability and retained almost 95 % of their activity after being stored at 4 ℃ for 8 weeks. This research provides experimental evidence that highlights the importance of studying of enzyme immobilization on the supports with synergistically designed geometric structures and surface chemical properties.

Mechanical behavior of butt curved adhesive joints subjected to bending

Abstract Factors such as the surface geometry of a joint, the direction of the applied load, and the type of adhesive used have a great influence on the strength of a joint in adhesive bonding. In adhesively bonded joints (ABJ), it is possible to improve surface geometry by forming various geometric surfaces. ABJs are not very resistant to peeling stress, thus requiring that a bonding model be analyzed according to the direction of the applied load to prevent peeling stress. In this study, a butt curved joint was prepared from aluminum plates (A2024-T3) to improve the surface geometry of the joint. The mechanical behavior of the joints in three-dimensions and subjected to bending were investigated depending on an increase in the curvature radius. The adhesive DP810 was used for bonding. The finite element analysis was performed in ANSYS and cohesive zone modeling was used for a simulation of the damage growth in the adhesive layer. The results of bilinear and exponential models were found to be more appropriate to the experimental results. When the radius of curvature increases, the damage load carried decreases in the butt curved lap joints. It was seen that decreases in the curvature radius significantly decrease normal stress.

Experimental study on bond behavior of corroded rebars coated by anti-corrosive materials in polymer cement mortar

This study investigates the bond behavior of anti-corrosive coated corroded rebars in a polymer cement mortar (PCM) as a common patching material to repair corrosion-induced damaged reinforced concrete structures. Cementitious and epoxy types of anti-corrosive coating materials are utilized. The corroded rebars are prepared by accelerated corrosion test in laboratory with a 5–10% target corrosion degree. The single effect of the coating materials on the bond behavior is investigated using coated round and deformed rebars. The combined effects of the corrosion and the coating materials are investigated using coated corroded deformed rebars. To thoroughly understand the bond behavior and mechanism, the effects of the corrosion and the coating materials on the change in the geometrical properties and surface roughness of the rebars are quantitatively analyzed by laser scanning tests. Finally, a two-end pull-out test is conducted to measure and investigate the bond-slip relationship, ultimate bond strength, bond toughness, and bond ductility.Similar to the findings on cementitious coated deformed rebar confined in concrete in a previous study by the authors, the results of the current study revealed that in the PCM, the cementitious coated rebar presents promising good bond performance regardless of the corrosion degree compared to the epoxy coated rebar. This is because when the ribs of the deformed rebars would deteriorate owing to corrosion, the rough surface of a cementitious coated rebar can sustain well its bond performance compared with the smooth and glassy surface of an epoxy coated rebar. Moreover, the direct effect of the surface roughness characteristics of these coating materials is clarified using coated round rebars. Consequently, the cementitious coated rebar achieves a considerably higher bond strength with a brittle behavior than the epoxy coated rebar, which presents a ductile behavior.

Vision-Guided MPC for Robotic Path Following Using Learned Memory-Augmented Model.

The control of the interaction between the robot and environment, following a predefined geometric surface path with high accuracy, is a fundamental problem for contact-rich tasks such as machining, polishing, or grinding. Flexible path-following control presents numerous applications in emerging industry fields such as disassembly and recycling, where the control system must adapt to a range of dissimilar object classes, where the properties of the environment are uncertain. We present an end-to-end framework for trajectory-independent robotic path following for contact-rich tasks in the presence of parametric uncertainties. We formulate a combination of model predictive control with image-based path planning and real-time visual feedback, based on a learned state-space dynamic model. For modeling the dynamics of the robot-environment system during contact, we introduce the application of the differentiable neural computer, a type of memory augmented neural network (MANN). Although MANNs have been as yet unexplored in a control context, we demonstrate a reduction in RMS error of 21.0% compared with an equivalent Long Short-Term Memory (LSTM) architecture. Our framework was validated in simulation, demonstrating the ability to generalize to materials previously unseen in the training dataset.

EDEM Investigation and Experimental Evaluation of Abrasive Wear Resistance Performance of Bionic Micro-Thorn and Convex Hull Geometrically Coupled Structured Surface

Procambarus clarkii was found to have excellent anti-wear performance against abrasive materials. To improve the wear resistance performance of the soil-engaging component of agricultural machinery, in this study, the micro-thorn and convex hull coupled geometrical structured surfaces inspired from the cephalothorax exoskeleton of the Procambarus clarkii was selected as the bionic prototype. By adopting bionic engineering techniques, three types of novel geometrical structured surfaces were proposed, which were bionic single, double and triple micro-thorn coupled convex hull surfaces (Bionic Type 2, 3 and 4, respectively). The anti-abrasive wear properties of these proposed geometrical surfaces were compared with a conventional bionic convex hull structured surface (Bionic Type 1) and a surface without any structures (smooth). Abrasive wear tests were conducted by using a rotational abrasive wear testing system. The accumulative test time was 80 h and the total wear distance was 6.09 × 105 m. By adopting the EDEM software (discrete element modeling), the Archard Wear model was selected to simulate the wear behavior of five different surfaces. In addition, the wear mechanisms of different surfaces were investigated. The results showed that the smooth surface suffered the most severe abrasive were, the abrasion loss reached 194.1 mg. The anti-abrasive properties of bionic geometric structured non-smooth surfaces were greatly improved; the reduction in terms of abrasion losses ranged between 20.4% and 94.1%, as compared with the smooth surface. The wear resistance property of micro-thorn and convex hull coupled structured surfaces were greatly improved as compared with convex hull and smooth surface. Bionic Type 3 was found to have the best anti-abrasive wear property: the abrasion loss was 11.5 mg. The wear morphology was observed by a scanning electron microscope. Smooth surface was characterized with wide, large size of grinding debris, while the bionic non-smooth surface featured narrow and small size abrasive dust. The results obtained from EDEM simulation agreed well with those of the aforementioned real scenario tests. It was revealed that the wear areas of the micro-thorn and convex hull coupled structured surface were mainly concentrated on the edge of convex hull and micro-thorn that faced the coming direction of particle flow. The geometric structure of the convex hull had beneficial effects on changing the movement behavior of particles, which means the stream of particle flow could be altered from a sliding to rolling state. Consequently, the ploughing and cutting phenomena of particles that act on the surfaces were greatly mitigated. Moreover, after being coupled with micro-thorns, the anti-abrasive wear preparty of the bionic convex hull geometrical structured surface was further improved. The rebound angle of particle flow that contacted the bionic micro-thorn coupled convex hull structured surface was greater than that of the conventional convex hull surface. Therefore, the dispersion effect of particle flow was further enhanced, since the movement behavior of the subsequent impact particle flow was altered. As a result, the wear of the bionic non-smooth surface was further reduced. This biconically inspired novel micro-thorn and convex hull coupled structured surface could provide theatrical and technical references to enhance the wear resistance performance of the soil-engaging component of agricultural machinery and mitigate the problem of abrasive wear failure.

Segmentation of Change in Surface Geometry Analysis for Cultural Heritage Applications.

This work proposes a change-based segmentation method for applications to cultural heritage (CH) imaging to perform monitoring and assess changes at each surface point. It can be used as a support or component of the 3D sensors to analyze surface geometry changes. In this research, we proposed a new method to identify surface changes employing segmentation based on 3D geometrical data acquired at different time intervals. The geometrical comparison was performed by calculating point-to-point Euclidean distances for each pair of surface points between the target and source geometry models. Four other methods for local distance measurement were proposed and tested. In the segmentation method, we analyze the local histograms of the distances between the measuring points of the source and target models. Then the parameters of these histograms are determined, and predefined classes are assigned to target surface points. The proposed methodology was evaluated by considering two different case studies of restoration issues on CH surfaces and monitoring them over time. The results were presented with a colormap visualization for each category of the detected change in the analysis. The proposed segmentation method will help in the field of conservation and restoration for the documentation and quantification of geometrical surface change information. This analysis can help in decision-making for the assessment of damage and potential prevention of further damage, and the interpretation of measurement results.

A new tomography-based approach for the fluid dynamic description of conventional structured packings and sandwich packings

Pressure drop, holdup and flooding points are essential factors for the hydraulic design of columns equipped with structured packings. This is also true for sandwich packings representing a combination of two alternating layers of conventional structured packings with different geometric surface areas. Such a combination results in a heterogeneous flow pattern evolving within certain operating ranges. In order to describe accurately the fluid dynamics over the entire operating range of both common structured packings and sandwich packings, a modelling approach is proposed based on conventional measurements and tomographic investigations. The approach distinguishes film-like flow patterns and froth regimes. For film-like flow patterns, packing-typical descriptions are used, whereas the froth in packings is described using an analogy to trays. Correlations were derived to determine the liquid holdup for film and froth flow, the dry and irrigated pressure drop as well as the gas velocities at the loading limits. The fluid dynamic model was verified with 1595 measurements for pressure drop and 510 measurements for holdup for the test system water/air.

A Two-Dimensional Thermoelasticity Solution for Bimodular Material Beams under the Combination Action of Thermal and Mechanical Loads

A typical characteristic of bimodular material beams is that when bending, the neutral layer of the beam does not coincide with its geometric middle surface since the mechanical properties of materials in tension and compression are different. In the classical theory of elasticity, however, this characteristic has not been considered. In this study, a bimodular simply-supported beam under the combination action of thermal and mechanical loads is theoretically analyzed. First, a simplified mechanical model concerning the neutral layer is established. Based on this mechanical model, Duhamel’s theorem is used to transform the thermoelastical problem into a pure elasticity problem with imaginary body force and surface force. In solving the governing equation expressed in terms of displacement, a special solution of the displacement equation is found first, and then by utilizing the stress function method based on subarea in tension and compression, a supplement solution for the displacement governing equation without the thermal effect is derived. Lastly, the special solution and supplement solution are superimposed to satisfy boundary conditions, thus obtaining a two-dimensional thermoelasticity solution. In addition, the bimodular effect and temperature effect on the thermoelasticity solution are illustrated by computational examples.

Radiation Resistance Of Filled Elastomer Compositions

The paper investigates the physical and chemical properties of the carbon-containing material of the secondary raw material for the production of acetylene and its effect on the radiation resistance of rubber products and cable rubbers. It was found that the carbon-containing material is modified carbon, the surface of which is microencapsulated with oligomeric oxygen-containing compounds, its thickness, calculated from the value of the specific geometric surface, amounted to 50-60Å. The effect of carbon-containing material on the relaxation coefficient and compressive stress is shown, and radiation resistance by the relative elongation of rubbers in an ionizing radiation environment 60Co. At the same time, it was found that, due to the finished oligomer on the surface of particles of carbon-containing material, threshold dose of radiation of rubbers based on styrene butadiene rubber according to the relaxation index, compressive stress and the coefficient of radiation resistance in terms of relative elongation increases three times compared to carbon blacks P803. Similarly, dependencies were obtained in rubbers based on other types of rubbers, including nitrile butadiene rubbers, possessing low radiation resistance due to the increased tendency to structuring. The findings indicate that the carbon-containing material is an effective filler for increasing the radiation resistance of industrial rubber goods and cables, operated in the environment of ionizing radiation.

Determination of the Physical and Mechanical Properties of Turmeric (Curcuma longa L.)

Turmeric is a medicinal crop widely popular due to its curcumin content. While other countries have established the physical properties of this crop, literatures specific for turmeric found in the Philippines have yet been documented. Freshly harvested turmeric rhizomes were randomly selected and their physical and mechanical properties were measured. Test results showed that the rhizomes have an average moisture content of 84.7 %. The samples have mean dimensions of 77.2 mm (length), 23.0 mm (width) and 19.7 mm (thickness). Computations showed that the rhizomes have a geometric mean diameter, sphericity, aspect ratio, surface area, and volume of 32.4 mm, 0.436, 31.6, 3371.2 mm2 , and 19044.8 mm3 , respectively. The gravimetric properties were also determined, and measurements showed that the fresh rhizomes have true density, bulk density, and porosity of 1.002 g/mL, 0.51 g/mL, and 48.8 %, respectively. Frictional properties against plywood (across the grain), plywood (along the grain) and stainless steel revealed that the rhizomes have a coefficient of friction of 0.41, 0.30 and 0.20 against these materials, respectively. The average angle of repose on a flat level surface is 18.6°. The maximum puncture and shear force that mother rhizomes can withstand were determined to be 0.1761 and 0.1708 kN, respectively. For the finger rhizomes, a maximum puncture force of 0.1029 kN and shear force of 0.0899 kN were recorded. Fresh rhizomes were sliced and dried until the final moisture content reached 8 to 9%, in which they were then pulverized. Optical properties were characterized using the CIE L*a*b* color scale and were converted to H-S-B. Preliminary findings showed that hue values for the three classifications were almost the same and were identified to fall between the orange and yellow hue. The dried rhizomes recorded the lowest saturation and brightness values, however, these values increased after pulverization indicating that only the surface color was affected and the interior of the rhizomes retained its vividness.