Surface Generation Research Articles

Generation of functional surfaces to assist in decision-making for wire arc additive manufacturing

Traditionally, product development involved separate design and manufacturing processes, leading to significant challenges in cost, time, and quality. However, the advent of Computer-aided design (CAD) systems in the late 20th century bridged this gap, enabling a seamless exchange of design information and coinciding with the rise of Additive Manufacturing (AM) processes. A critical aspect of CAD/CAM systems is determining the functional specification of CAD assembly models, with design tolerances directly impacting product buildability. However, accessing this data remains complex. This paper presents an approach to extract feature surfaces from assembly models automatically. Initially, assembly constraints are analyzed to determine component relationships, which are then used to extract corresponding functional surfaces. This algorithmic process includes two pivotal phases: one for surface characterization and another for exploring constraints. This approach yields a comprehensive representation of functional surfaces associated with the components. Addressing this challenge, the effectiveness of this approach is demonstrated through an illustrative example, showcasing the extraction of information related to functional surfaces from the outset of the process. After conducting a thorough comparative analysis, specifically targeting the mechanical properties of parts produced using Cold Metal Transfer (CMT) and Cold Metal Transfer Cycle Step techniques, it was determined tS100hat CMT is best suited for constructing the main body of the component. Meanwhile, the CMT Cycle Step will be used for producing surrounding volumes. This strategic allocation ensures that each technique is employed to maximize its strengths, optimizing performance and efficiency throughout the manufacturing process. In conclusion, a hybrid approach combining both CMT and CMT Cycle Step techniques, while considering functional surfaces. This integrated strategy capitalizes on the strengths of each method.

A Novel Radial Basis Function Description of a Smooth Implicit Surface for Musculoskeletal Modelling

As musculoskeletal illnesses continue to increase, practical computerised muscle modelling is crucial. This paper addresses this concern by proposing a mathematical model for a dynamic 3D geometrical surface representation of muscles using a Radial Basis Function (RBF) approximation technique. The objective is to obtain a smoother surface while minimising data use, contrasting it from classical polygonal (e.g. triangular) surface mesh models or volumetric (e.g. tetrahedral) mesh models. The paper uses RBF implicit surface description to describe static surface generation and dynamic surface deformations based on its spatial curvature preservation during the deformation. The novel method is tested on multiple data sets, and the experiments show promising results according to the introduced metrics.

Surface generation mechanism and efficiency improvement in ultrasonic vibration assisted belt flapwheel flexible polishing GH4169

Surface generation mechanism and efficiency improvement in ultrasonic vibration assisted belt flapwheel flexible polishing GH4169

(Invited) Surface and Structural Dependent Reactivity of Alkylphosphonic Acids-Modified Titanium Oxide Nanostructures with 2-Chloroethyl Ethyl Sulfide Under Visible Light Excitation

Synthesizing novel TiO2 nanomaterials are valuable for heterogeneous reactivity to address toxic chemical remediation. Titanium oxide nanoflowers (comprising assemblies of nanorods) and nanowires have been synthesized in which photocatalytic reactivity with 2-chloroethyl ethyl sulfide (2-CEES) has been significantly enhanced under visible light (1000 nm > λ > 400 nm) excitation. Enhancement of photooxidation with reaction rates of 99 and 168 µmol/g/h (quantum yields of 5.07 x 10-4 and 8.58 x 10-4 molecules/photon) were observed for TiO2 synthesized in the presence of two different alkylphosphonic acids (C14H29PO3H2 and C9H19PO3H2). Additionally, H2Ti2O5‧H2O nanowires were synthesized and capable of highly efficient hydrolysis of the carbon-chlorine (C-Cl) bond of 2-CEES without light at a reaction rate of 279.2 µmol/g/h due to high surface area and chemical nature of the titanate structure. These observations are correlated with: 1) generation of new surface defects/states (i.e. oxygen vacancies) as a result of TiO2 grafting by alkyl phosphonic acid that may serve as reaction active sites; 2) better light absorption by assemblies of nanorods in comparison to individual nanorods, 3) surface area differences, and 4) the exclusion of OH groups due to the formation surface functionalization with alkylphosphonic acids via Ti-O-P bonds on the TiO2. These robust materials can be used for highly efficient surface decontamination.

Investigation of Surface Integrity Induced by Ultra-Precision Grinding and Scratching of Glassy Carbon.

Glassy carbon provides material characteristics that make it a promising candidate for use as a mould material in precision glass moulding. However, to effectively utilize glassy carbon, a thorough investigation into the machining of high-precision optical surfaces is necessary, which has not been thoroughly investigated. This research analyses the process of material removal and its resulting surface integrity through the use of nano-scratching and ultra-precision grinding. The nano-scratching process begins with ductile plastic deformation, then progresses with funnel-shaped breakouts in the contact zone, and finally concludes with brittle conchoidal breakouts when the cutting depth is increased. The influence of process factors and tool-related parameters resulting from grinding has discernible impacts on the ultimate surface roughness and topography. Enhancing the cutting speed during cross-axis kinematic grinding results in improved surface roughness. Increasing the size of diamond grains and feed rates leads to an increase in surface roughness. An achievable surface roughness of Ra < 5 nm together with ductile-regime grinding behaviour meet optical standards, which makes ultra-precision grinding a suitable process for optical surface generation.

Femtosecond Pulsed Laser Irradiation of Zirconia for Embedding Silver Nanoparticles in Surface Nanopores

Femtosecond pulsed laser irradiation was performed to investigate the feasibility and fundamental characteristics of embedding silver nanoparticles onto zirconia ceramic surfaces. By irradiating laser, nanopores were fabricated on the surface of the yttria-stabilized zirconia (YSZ) substrate, and silver nanoparticles were infiltrated and immobilized into the pores using a commercial nano-silver dispersion solution. Numerous nanopores embedded with silver nanoparticles were successfully obtained on the YSZ surface while keeping the grains’ shapes unchanged by controlling laser parameters. Optimizing laser fluence and scanning speed near the ablation threshold made it possible to remove only the excess dispersant that remained on the surface while keeping silver in the pores and without causing machining of the surface of the YSZ substrate. In addition, about 60% embedding in the nanopores was achieved. It was found that the shorter pulse width was suitable to avoid evaporating both dispersant and silver. Cross-sectional observation revealed that the silver nanoparticles were agglomerated to form clumps and were embedded without a gap at the bottom of the pores at a depth of about 600 nm. After laser irradiation, no significant laser-induced phase change was observed in the YSZ substrate, indicating that there was no in-process thermal damage to the bulk. These findings demonstrated the possibility of adding a metal nanoparticle to the zirconia surface by using only a laser process without damaging the properties of the base material during the process. New applications of zirconia, such as the generation of functional surfaces with antibacterial properties, are expected.

New insights on the layer uniformity of multilayered films produced by coextrusion with interfacial surface generators

AbstractPolymer coextrusion is a manufacturing process whereby at least two polymer melts feed a die to form an extrudate made up of different layers, typically up to 12, to achieve a better product performance. Extruded films with hundreds or thousands of layers can be produced by using sequences of layer multipliers, also known as interfacial surface generators (ISG), at the die inlet. Each ISG splits, stacks, and merges the flow by means of various geometrical channel transformations (GT), in such a way that the number of layers at the outlet is doubled. However, in practice, the thicknesses of the individual layers generated after each transformation are often non‐uniform. This work deals with the numerical simulation of multilayer co‐extrusion of Newtonian polymer melts, aiming at providing new insights on the influence of the ISG geometry on the layer uniformity. It was found that depending on the combination of GT taking place, uneven layers may form due to the development of unsymmetrical velocity profiles along the direction perpendicular to the fluid interface. From this information, improved ISG dies, capable of producing coextruded films with uniform layer distribution, are proposed and assessed numerically.Highlights The polymer coextrusion process produces multilayer products. Extruded films can be produced using Interfacial surface generators (ISG). Polymers flow through ISG by several channel geometric transformations (GTs). Polymer melts flow through ISG undergoing various channel geometric transformations (GTs). Non‐uniform layers can be generated in the ISG. ISG performance can be improved when GTs are thoughtfully combined.

Multiscale Modeling of a Chain Comprising Selective Laser Melting and Post-Machining toward Nanoscale Surface Finish.

The generation of rough surfaces is an inherent drawback of selective laser melted (SLM) material that makes post-treatment operation a mandatory process to enhance its surface condition and service performance. However, planning an appropriate and optimized chain to attain the best surface finish needs an integrated simulation framework that includes physics of both additive manufacturing and post-processing. In the present work, an attempt is made to model the alternation of surface roughness which is produced by SLM and post-processed by milling and sequential surface burnishing. The framework includes a series of closed-form analytical solutions of all three processes embedded in a sequence where the output of the preceding operation is input of the sequential one. The results indicated that there is close agreement between the measured and predicted values of arithmetic surface roughness for both SLM material and the post-processed ones. It was also found that a nanoscale surface finish is obtained by finishing milling and single pass rolling at a static force of 1500 N. In addition, the results of the simulation showed that elimination of the milling process in the chain resulted in a six-times-longer production time that requires three times bigger rolling force compared to a chain with an included milling operation.

Contact Analysis for Cycloid Pinwheel Mechanism by Isogeometric Finite Element

Cycloid drives are generally used in precision machinery requiring high-reduction ratios, such as robot joint (RV) reducers. The contact stress of cycloidal gears greatly affects lifetime and transmission performance. Traditional finite element method (FEM) has less computational efficiency for contact analysis of complex surface. Therefore, in this paper, isogeometric analysis (IGA) was employed to explore the multi-tooth contact problem of the cycloid pinwheel drive. Based on the nonuniform rational B spline (NURBS) curved surface generation method, the NURBS tooth profile of the cycloid gear was reconstructed. In addition, the NURBS surface of the cycloid gear–pin tooth–output pin was generated via the element splicing method. A geometrical analysis model of cycloid pinwheel drive was established to solve the contact force of the meshing pair under different input angles and compared with the finite element method in terms of convergence, resultant accuracy, and solving timeliness. The results show that isogeometric analysis has higher accuracy and efficiency than the finite element method in calculating the contact stress and contact force. The error of the IGA is only 8.8% for 10 × 10 elements in contact, while the error of the finite element method reaches about 40%. The method can improve the contact simulation accuracy of the cycloid drive and provides a reference for the design evaluation of RV reducer.

Advances in laser-based surface texturing for developing antifouling surfaces: A comprehensive review

Surface fouling is a major challenge faced within various engineering applications, especially in marine, aerospace, water treatment, food and beverage, and the energy generation sectors. This can be prevented or reduced in various ways by creating artificial surface textures which have fouling resistance properties. Ultrafast laser texturing provides an efficient method for the texturing of surfaces of different materials with high accuracy, precision, and repeatability. Laser texturing methods can enhance the production of well-defined surface nano- and microscale patterns. These surfaces with nano- and micro-scale patterning can be tailored to have inherent properties such as hydrophobicity, hydrophilicity, and resistance to fouling. This review gives an overview of the various types of fouling that can occur, the properties affecting a surface's fouling resistance, as well as the latest physical and chemical strategies for the generation of antifouling surfaces. Surfaces architectures which have inherent antifouling capabilities are presented. This review focuses on the utilization of the higher precision laser-based texturing offered from femtosecond laser systems for enhance fouling resistance. The process parameters to fabricate these textures and the current state of art femtosecond laser sources are presented and discussed. The challenges and future research requirements in the field of laser-based methods to fabricate antifouling surfaces are presented.

The Generation of 3D Surface Meshes for NURBS-Enhanced FEM

This work presents the first method for generating triangular surface meshes in three dimensions for the NURBS-enhanced finite element method. The generated meshes may contain triangular elements that span across multiple NURBS surfaces, whilst maintaining the exact representation of the CAD geometry. This strategy completely eliminates the need for de-featuring complex watertight CAD models and, at the same time, eliminates any uncertainty associated with the simplification of CAD models. In addition, the ability to create elements that span across multiple surfaces ensures that the generated meshes are highly compliant with the requirements of the user-specified spacing function, even if the CAD model contains very small geometric features. To demonstrate the capability, the proposed strategy is applied to a variety of CAD geometries, taken from areas such as solid/structural mechanics, fluid dynamics and wave propagation.

Surface generation and material removal mechanism incorporated with the randomness of grain size and distribution in grinding

Grinding process can achieve minimal material removal quantity and multiple material removal mechanisms simultaneously, which makes it extremely popular in industrial applications to meet the requirements of high dimension precision, excellent surface quality and rigorous tolerance. However, due to the randomly-sized and randomly-distributed abrasive grains, an accurate ground surface prediction model remains a significant challenge by considering the actual microstructure of grinding wheel. This research aims to develop a novel surface prediction model to take into account the random nature of the grain size and its distribution in grinding wheel. The generation of ground surface is modeled by calculating the transient trajectory of grain in the whole contact zone. Micro grain-workpiece contact mechanism is revealed in terms of the typical stages of rubbing, plowing and cutting to determine the ground surface morphology. Grinding experiments were performed to compare with the predicted surface morphologies. The proposed model was further validated in the terms of surface topography, roughness and material removal rate. Additionally, material removal mechanism associated with surface generation has been explored by the predicted ground surface and material removal rate under different grain-workpiece interaction states. The provided model is further employed to examine the impact of the randomness of grain size and distribution and grinding parameters on the surface roughness. Thus, the research provides fresh insights into understanding the underlying mechanism in different grain stages as well as revealing the transient contact mechanisms in generating ground surface integrity.

Mechanism of surface modification on monocrystalline silicon during diamond polishing at nanometric scale

The demand for polished silicon wafers has increased significantly in recent years to cater to the development of the semiconductor industry. For example, polished silicon wafer has direct applications in integrated circuits, radio frequency amplifiers, micro-processors, micro-electromechanical systems, etc. To carry out mechanical polishing, lapping, grinding, or single-point diamond turning of silicon, diamond abrasives were extensively used before the implementation of chemo-mechanical polishing. During the diamond-based polishing, a few problems have already been identified, such as the formation of an amorphous phase, heat-affected zones, low material removal, etc. Some research work has also reported that nano-structured abrasives lead to a thin layer of the amorphous phase and a better material removal rate. In the same direction, a molecular dynamics simulation is carried out in this paper to investigate the mechanism of material removal from monocrystalline silicon during the diamond-abrasive-based polishing process. The present work is mainly focused on the dynamics of material removal phenomena near the abrasive particles at the nanometric scale by considering stress, lattice, cohesive energy, etc. This reveals that a higher value of indentation force results in surface buckling, which creates a zone of both compressive and tensile stresses, which increases the coordination number and forms β-silicon just ahead of the abrasive particle. This mechanism happens by developing a β-silicon phase on the surface with a thickness beyond a certain value of indentation force on the zone of compression. Buckling on this phase happens due to stress localisation in compression, as the flow stress of this phase is less than that of diamond cubic lattices. To avoid the mechanism of surface buckling and process silicon material on the surface, the indentation force needs to be maintained below a critical value. In the present case, it was found that the indentation force of less than or equal to 190 nN for the abrasive size of ϕ8 nm does the material removal by surface processing only without surface buckling. It was also found that surface processing helps to reduce the depth of the amorphous layer significantly without compromising the material removal rate or the generation of a wavy surface. Thus, the present mechanism will help in the polishing of silicon with minimum defects and reduce processing time for the final stage of polishing towards manufacturing ultra-smooth and planer surfaces.

Generation of Amorphous Silica Surfaces with Controlled Roughness.

Amorphous silica (a-SiO2) surfaces, when grafted with select metals on the active sites of the functionalized surfaces, can act as useful heterogeneous catalysts. From a molecular modeling perspective, one challenge has been generating a-SiO2 slab models with controllable surface roughness to facilitate the study of the effect of surface morphology on the material properties. Previous computational methods either generate relatively flat surfaces or periodically corrugated surfaces that do not mimic the full range of potential surface roughness of the amorphous silica material. In this work, we present a new method, inspired by the capillary fluctuation theory of interfaces, in which rough silica slabs are generated by cleaving a bulk amorphous sample using a cleaving plane with Fourier components randomly generated from a Gaussian distribution. The width of this Gaussian distribution (and thus the degree of surface roughness) can be tuned by varying the surface roughness parameter α. Using the van Beest, Kramer, and van Santen (BKS) force field, we create a large number of silica slabs using cleaving surfaces of varying roughness (α) and using two different system sizes. These surfaces are then characterized to determine their roughness (mean-squared displacement), density profile, and ring size distribution. This analysis shows a higher concentration of surface defects (under-/overcoordinated atoms and strained rings) as the surface roughness increases. To examine the effect of the roughness on surface reactivity, we re-equilibriate a subset of these slabs using the reactive force field ReaxFF and then expose the slabs to water and observe the formation of surface silanols. We observe that the rougher surfaces exhibit higher silanol concentrations as well as bimodal acidity.

3D Surface Reconstruction Based on Dynamic Graph Convolutional Occupancy Network

A 3D reconstruction method based on dynamic graph convolutional occupancy networks is proposed to address the issues of texture information loss, geometric information loss after voxelization, and lack of object completeness constraints in the process of 3D reconstruction using voxel representation in a block-wise manner. By constructing a dynamic graph structure for feature extraction, the method aims at restore 3D models with fewer holes and local details. In the feature extraction stage, local pooling is employed within each point cloud block to address the problem of nonsignificant texture feature loss. To tackle the issues of geometric constraint loss and insufficient scene semantic information caused by block-wise processing, a feature fusion method between adjacent blocks is proposed to learn richer scene semantic information and long-range dependencies between points. By learning features within and between blocks, each point retains as much geometric information as possible, mitigating the problem of geometric information loss due to voxelization. During the surface generation, interpolation is used to infer the occupancy value for each point, and the Marching Cubes algorithm is employed for three-dimensional surface reconstruction. Experimental validation on object-level (ShapeNet dataset) and scene-level (Synthetic Rooms dataset, MatterPort3D dataset for real-world scenes) datasets demonstrates the effectiveness and advancement of the proposed method.

Digital terrain, surface, and canopy height model generation with dual-baseline low-frequency InSAR over forest areas

Digital terrain, surface, and canopy height model generation with dual-baseline low-frequency InSAR over forest areas

Marriage of High-Throughput Gradient Surface Generation with Statistical Learning for the Rational Design of Functionalized Biomaterials.

Functional biomaterial has already become an important aspect in modern therapeutics, yet the design of novel multi-functional biomaterial is still a challenging task nowadays. When several biofunctional components are present, the complexity that arises from their combinations and interactions would lead to tedious trial-and-error screening. In this work, we present a novel strategy of biomaterial rational design through the marriage of gradient surface generation with statistical learning. Not only parameter combinations can be screened in a high-throughput fashion, the optimal conditions beyond the experimentally tested range can also be extrapolated from the models. We have demonstrated the power of our strategy in rationally designing an unprecedented ternary functionalized surface for orthopedic implant, with optimal osteogenic, angiogenic and neurogenic activities, and have confirmed its optimality in vitro and the best osteointegration promotion in vivo. The presented strategy is expected to open up new possibilities in the rational design of biomaterials. This article is protected by copyright. All rights reserved.

Trapping processes of large volumes of natural hydrogen in the subsurface: The emblematic case of the Bourakebougou H2 field in Mali

Most of the ongoing discussions about natural hydrogen (H2) exploration focus on surface hydrogen occurrences and generation processes. However, the trapping process is the most critical issue with regard to both discovering significant accumulations of hydrogen in the subsurface and providing profitable clean energy production for humankind. The extremely high mobility of hydrogen molecules is due to their very small size that confers very diffusive properties, and this results in frequent surface seepages that have recently been recorded worldwide. During this study, we performed a detailed characterization of the caprocks (dolerites) that retain hydrogen in the Bourakebougou natural H2 field. Our investigation on the sealing capacity of these dolerites revealed that their thickness is important in addition to the density and size of their fractures. The role of aquifers has also been highlighted as contributing to the retention of H2 in subsurface. Indeed, hydrogen being poorly soluble in water at low pressure and temperature conditions, it is less likely to diffuse easily to the surface at shallow depth. This study highlights that the exploration of H2 fields should not be based only on the presence of an H2 generation process, but also based on the presence of a very efficient trapping system.

Bridging Eulerian and Lagrangian Poisson-Boltzmann solvers by ESES.

The Poisson-Boltzmann (PB) model is a widely used electrostatic model for biomolecular solvation analysis. Formulated as an elliptic interface problem, the PB model can be numerically solved on either Eulerian meshes using finite difference/finite element methods or Lagrangian meshes using boundary element methods. Molecular surface generators, which produce the discretized dielectric interfaces between solutes and solvents, are critical factors in determining the accuracy and efficiency of the PB solvers. In this work, we investigate the utility of the Eulerian Solvent Excluded Surface (ESES) software for rendering conjugated Eulerian and Lagrangian surface representations, which enables us to numerically validate and compare the quality of Eulerian PB solvers, such as the MIBPB solver, and the Lagrangian PB solvers, such as the TABI-PB solver. Furthermore, with the ESES software and its associated PB solvers, we are able to numerically validate an interesting and useful but often neglected source-target symmetric property associated with the linearized PB model.

Effects of powder surface conditions on the rheological behavior of Ti–6Al–4 V alloy powders for additive manufacturing

Laser powder-bed fusion (L-PBF) is a promising manufacturing process for fabricating metallic parts with tailored architectures. A feedstock powder with good flowability is required to homogeneously deposit the powder on the building substrate and obtain reliable and high-quality L-PBF products. Although the effects of powder morphology and particle size on flowability have been widely investigated, the relationship between powder surface conditions and rheological behaviors is not well established. Therefore, in this study, the surface conditions of Ti–6Al–4 V alloy powders were intentionally adjusted through conventional heat treatments under different gas atmospheres. The morphology and particle size distribution of the Ti–6Al–4 V powder heat treated at 773 K in air (Air773) and Ar (Ar773) atmospheres remained unchanged compared to those of the untreated powder. However, the quantity of surface oxides on the Air773 powder increased, enhancing the decoration of surface hydroxyl groups, as illustrated by water wettability tests. By contrast, the oxide layer of the Ar773 powder decomposed and dissolved into the matrix, resulting in the generation of fresh metallic surfaces. Consequently, the flowability of the Air773 powder increased, whereas that of the Ar773 powder tended to decrease, thereby deteriorating the quality of powder beds during the recoating process. The results prove that the cohesive strength of Ti–6Al–4 V powder is more strongly determined by metallic TiTi interactions than by hydrogen bonds. Thus, the effective approach for adjusting the powder surface conditions presented in this study offers new insights into the potential for economically developing high-performance Ti alloy components by controlling the powder properties and L-PBF process.