Three-dimensional Complex Shapes Research Articles

Solvent-free high-performance photocurable 3D printing resin from a noncoplanar branched maleimide oligomer for high-resolution fabrication

The ever-increasing requirements of photosensitive materials are put forward by the increase in the applications of photocuring 3D printing in high-tech fields. Nevertheless, the poor compatibility between high-performance resins and photocurable monomers renders challenges associated with the preparation of solvent-free resins with excellent comprehensive properties. In this work, a maleimide oligomer with a noncoplanar branched structure is synthesized in one step, which can be dissolved in a photocurable monomer. A low-viscosity, high-performance photocurable resin is prepared without an organic solvent and printed in layer by layer into a high-resolution (50 µm) three-dimensional complex shape. The material’s crosslinking density is further increased by thermal curing, achieving a improvement in mechanical properties. The printing device exhibits an storage modulus of up to 1.9 GPa at 200 °C and a dimensional shrinkage of less than 4%; it can also support a heavy object that exceeds its own weight by 1124 times. This resin achieves the balance between the viscosity, printing accuracy, and performance, demonstrating immense application potential in microelectronics, aerospace, etc.

Optical Printing of Single Au Nanostars.

Obtaining arrays of single nanoparticles with three-dimensional complex shapes is still an open challenge. Current nanolithography methods do not allow for the preparation of nanoparticles with complex features like nanostars. In this work, we investigate the optical printing of gold nanostars of different sizes as a function of laser wavelength and power. We found that tuning the laser to the main resonances of the nanostars in the near-infrared makes it possible to avoid nanoparticles reshaping due to plasmonic heating, enabling their deposition at the single particle level and in ordered arrays.

Selective laser melting of Al–Si–10Mg alloy: microstructural studies and mechanical properties assessment

Additive Manufacturing (AM) technique is widely recognized by aerospace sectors for its potential to fabricate complex shape components directly from a Computer-Aided Model data (CAM). Selective Laser Melting (SLM) is an innovative method high degree of adaptability among different AM techniques. SLM is one of the AM techniques adopted to produce the three-dimensional complex shape components. Current research work focuses on fabricating an Al–Si–10Mg aluminium alloy by SLM process which is studied for the influence of scanning speed and build orientation on the mechanical strength and surface finish of the as built component compared with as casted specimen. The importance of the sample studied for the scanning speed and built direction is relatively essential exclusively for dynamic applications. The as-built samples surface micrographs was surprisingly refined with a progressively reduced grain size diameter from 7.2 μm to 5.5 μm by increasing scanning speed compared to that of AlSi10Mg parts (∼9.1 μm). The mean layer thickness increased from 20 μm to 30 μm by decreasing the scanning speed from 500 mm/s to 200 mm/s. Attractive advantage of the Orowan mechanism, fine grain strengthening, and the graded interfacial layer, a considerably-high microhardness (135 ± 3.1HV), and enhanced mechanical properties were achieved.

Flow forming of wood irradiated with electron beam ― Molding load of irradiated wood and mechanical properties of the molded material

In the flow forming technique of wood, a wood block is flowed into metal dies to mold the material into a three-dimensional complex shape. The purpose of this study was to investigate the effect of molding load and the mechanical properties of the molded material in the case that wood as a raw material was irradiated with electron beam (EB). The EB-irradiated wood board was impregnated with thermosetting resin and was subsequently molded into the material by adding pressure and heating in a closed metal die. It was found that the molding load of the impregnated wood was decreased with increasing the EB absorbed dose. The mechanical properties of the molded material were evaluated using modulus of elasticity (MOE) and modulus of rupture (MOR) in a three-point bending test. With increasing EB dose, MOR decreased greatly, while MOE decreased slightly. The EB irradiation on raw wood made it possible to mold the material at low load, though higher dose irradiation caused larger decreases in the mechanical properties.

Research on mathematical model of characteristic curve of surface perception by PVDF array based on Ferguson function

The traditional 3D shape perception and reconstruction requires the use of relatively expensive 3D scanning equipment to obtain the coordinates of discrete feature points of the 3D shape. The reconstruction accuracy is determined by the scanning accuracy of the 3D scanning device, generally, the accuracy is low. In this study, based on the PVDF piezoelectric film sensing array, the 3D topographic feature point coordinate value is perceived and acquired. According to the feature point coordinate value, the feature curve fitting of the 3D shape is obtained, and the slope information of the 3D topography characteristic curve is obtained. The mathematical model of the feature surface of PVDF array surface topography based on Ferguson curve is studied to realise the surface reconstruction of 3D complex topography. Theoretical research shows that three-dimensional complex topographic reconstruction technique based on Ferguson curve for PVDF piezoelectric film array surface topography perception has the advantages of simple principle, easy implementation and high precision of shape reconstruction. It can develop intelligent structure with three-dimensional complex shape perception function.

Development of 1-T Class Force-Balanced Helical Coils Using REBCO Tapes

The authors proposed the concept of the force-balanced helical coils (FBC) using high-temperature superconducting (HTS) tapes as a feasibility option for superconducting magnetic energy storage (SMES). Although the FBC can minimize the mechanical stresses induced by the electromagnetic forces, the FBC has three-dimensional complex shapes of helical winding. Therefore, when the tensile strain and the complex bending strain simultaneously apply to the HTS tapes, the critical current of the HTS coils may decrease irreversibly. The objective of this work is to clarify the critical current property of REBCO tapes depending on the applying complex mechanical strain due to the winding process, the winding configuration and the electromagnetic forces through the development of the HTS-FBC. As a first, design parameters of 1-T class FBC using REBCO tapes and coil winding trajectory were introduced, and the authors discussed the normalized critical current of the HTS-FBC for complex uniaxial strain distribution. The authors also reported a development of a helical winding machine whose motion was optimized to prevent from decreasing the critical current of the HTS tapes during winding process.

A Review on Direct Metal Laser Sintering: Process Features and Microstructure Modeling

Additive manufacturing (AM) has gained market interest in recent times, due to improvement in technologies and introduction of new metal powders for the end product with the application on different fields such as aerospace, medical and automotive sectors. Laser-based additive manufacturing is presently regarded as the most versatile process in additive manufacturing. This manufacturing technology produces three-dimensional complex shapes from the powder material in a layer by layer fashion directly from the metal powder. The process has the potential to be more flexible, to produce a wider range of shapes, and to form more challenging materials. As it is a rapid manufacturing technique, in which complex non-equilibrium physical and chemical metallurgical phenomena takes place. These phenomena will directly affect the qualities of build parts, which are dependent on the microstructure as well as process parameters. Thus, to understand the processing mechanism and the prediction of part microstructures during the process may be an important factor for process optimization. At the present time, an increase in computational resources allows for direct simulations of microstructures during materials processing for specific manufacturing conditions. So, there is a demand to develop an integrated computational platform coupling various phenomena or models together to understand and ultimately control and optimize the AM build process. The objective of this review is to present a thorough analysis of direct metal laser sintering process, process parameters, sintering mechanism, and comprehensive discussion on the phase field method for microstructure evolution and its application. This review aims at providing an insight into the mechanism of the processes and microstructure evolution both experimentally and numerically. It will act as a guide for researchers working on additive manufacturing and would also provide the future research gap for further studies.

에어나이프 시스템을 이용한 3차원 복합 형상 PDMS 마이크로스텐실 제작 및 세포배양 응용

에어나이프 시스템을 이용한 3차원 복합 형상 PDMS 마이크로스텐실 제작 및 세포배양 응용

Complex three- dimensional-shaped knitting preforms for composite application

For decades, street lighting and electric poles are made of metal and it is vulnerable to corrosion due to the harsh weather and chemicals. To overcome such essential problems, galvanized iron is used although it adds more hard work to increase the manufacturing cost. Therefore, fiber reinforced polymer lighting pole is proposed. Fiber reinforced polymer materials possess many advantages such as corrosion resistance, high specific strength and stiffness, etc. Two-dimensional woven fabrics and three-dimensional woven fabrics preforms are used to produce composite structures. However, complex shapes cannot be manufactured as a one piece preform. Woven fabrics, whether two-dimensional or three-dimensional need to be cut into patterns to finally produce the complex shapes. These processes add more cost and time to the final composite products. In this research, innovative technique to produce a three-dimensional complex shape knitted preform using regular flat-knitting machine will be presented. Production of such shaped three-dimensional preform permits the production of one piece-shaped preform without any connection or further sewing processes. Produced knitted preform can be used for various reinforcement applications such as light and communication poles, scaffold façades, traffic sign, oars, and wind mill blades.

Application of Rapid Prototyping to Create Additive Prototype Using Computer System

Rapid prototyping is a new group of manufacturing processes, which allows fabrication of physical of any complexity using a layer by layer deposition technique directly from a computer system. The rapid prototyping process greatly reduces the time and cost necessary to bring a new product to market. The prototypes made by these systems are used in a range of industrial application including design evaluation, verification, testing, and as patterns for casting processes. These processes employ a variety of materials and mechanisms to build up the layers to build the part. The present work was to build a FDM prototyping machine that could control the X-Y motion and material deposition, to generate two-dimensional and three-dimensional complex shapes. This study focused on the deposition of wax material. This work was to find out the properties of the wax materials used in this work in order to enable better control of the FDM process. This study will look at the integration of a computer controlled electro-mechanical system with the traditional FDM additive prototyping process. The characteristics of the wax were also analysed in order to optimise the model production process. These included wax phase change temperature, wax viscosity and wax droplet shape during processing. Keywords—Rapid prototyping, wax, manufacturing processes, additive prototyping.

Numerical modelling of forming of a non-crimp 3D orthogonal weave E-glass composite reinforcement

A hyperelastic constitutive model is implemented to study the formability on three-dimensional complex shapes of a single layer E-glass non-crimp 3D orthogonal woven reinforcement. Experimental measurements of the main deformation modes have been used to identify the strain energy density function of the constitutive model. The comparison of the finite element simulations and experimental results of tetrahedron and double-dome shaping processes demonstrated the adequacy of the adopted hyperelastic model to describe the deformation mechanisms involved during draping and the efficiency to predict the global behaviour of the non-crimp 3D woven reinforcement during complex shape forming.

Quantification of press elasticity in the forging of three-dimensional complex shapes

This paper presents an improved approach to characterize press elastic behaviour and to quantify the effect of press elasticity in the forging of three-dimensional (3D) complex shapes. Using a stiffness matrix formulation, the overall press elasticity is characterized by press elastic deformation and initial clearances of the press guideway. The effect of press elasticity in forging is evaluated by implementing the press stiffness matrix formulation into the 3D forging simulation using a user subroutine. An industrial-based 3D blade forging case study was carried out to assess the robustness and efficiency of this approach in the forging of 3D complex shapes. Compared with cases without press elasticity, the results show that the press elasticity has less effect on forging force requirements, material deformation, and stress and strain distributions. However, the effect of press elasticity is more apparent on the dimensional and shape accuracy of the forged blade with the initial guideway clearance as a major source for dimensional errors compared with the press elastic deformation. The case study also shows that this approach can be easily implemented for evaluating press tool-related effects in forging simulation and design.

Modelling feeding flow related shrinkage defects in aluminum castings

The process modelling of shape casting is geometrically complex and computationally very challenging. Besides the three-dimensional complex shapes with multiple domains, the defects of interest to industry arise as a consequence of the interaction amongst a range of phenomena. Conventionally, the key phenomena and defect prediction are modelled through empirical relations applied to the simulation results. Such approaches are neither comprehensive nor reliable. This paper presents a 3-D model that is capable of predicting the formation of shrinkage defects explicitly as a function of the interacting continuum phenomena, i.e. free surface flow, heat transfer, and solidification, in complex three-dimensional geometries which allows to identify the distinction between surface depression, surface connected cavities and internal cavities.The model solves the coupled macroscopic conservation equations for mass, momentum, and energy with a phase change during solidification. In the model, the volume deficit due to solidification can either be compensated by depression of the outside surface or by creating a cavity that initiates either on the surface or in the interior of the casting. The solidification morphology is taken into account by using a parameter, which depends on the fraction solid, in the momentum equation. By using an adapted free surface algorithm, it is suitable to predict surface connected defects: depressed surfaces and caved surfaces. A critical pressure serves as a criterion to open internal shrinkage cavities. The model does not need to search for connected zones to feed shrinkage, but the shrinkage distribution will automatically emerge from the continuity equation.This advanced shrinkage model has experimentally been validated successfully using two Al–Si alloys, a skin freezing eutectic alloy and a mushy freezing hypo-eutectic alloy.

RTM法によるFRP成形における電磁超音波センサを用いた樹脂硬化モニタリング

Electromagnetic acoustic transducer (EMAT) is applied to resin cure monitoring in manufacturing process of fiber reinforced plastic (FRP) by resin transfer molding (RTM) method. The RTM is suitable for fabrication of FRP products of three-dimensional complex shape. In order to reduce the cost by minimizing the cycle time, cure monitoring is required. Authors have already ensured that the EMAT can detect the resin flow front in RTM process by monitoring the change in reflection coefficient at mold surface due to resin impregnation. The reflection factor is also affected by the resin viscosity. In this study, during the curing process, we measure the attenuation coefficient of standing wave introduced in the mold. Results are compared with impedance of dielectric sensor located inside the mold, showing that the degree of cure can be evaluated by EMAT at outer surface of the mold.

Corrosion Behavior of Pure Titanium Produced by MIM Process under SSRT Condition

Metal injection molding (MIM) process has the advantage of better formability of three dimensional complex shape products with high density and high performance properties compared to the ingot metallurgy (I/M) process. Two kinds of pure titanium specimens, i.e., the first one is prepared by the I/M process and the second one is prepared by MIM process are used in this experiment, and their corrosion behavior under stress has been investigated in several aqueous solutions by Slow Strain Rate Tensile (SSRT) test. Both I/M and MIM specimens showed good corrosion resistance in the aqueous solution composed of 2.5 kmol/m3 H2SO4 and 0.2 kmol/m3 NaCl as well as saline solution. This aqueous solution is noted one in which Type 304 stainless steel showed SCC. In the aqueous solution composed of CH3OH and 0.1 kmol/m3 HCl containing 8.6kg/m3 H2O, the elongation of MIM specimen was slightly higher than that of I/M specimen though both specimens indicated the remarkable decrease in elongation.

Research on new float polishing technique with the magnetic compound fluid

This paper is a continuation of a previous paper. The report demonstrates the various possibilities of float polishing utilising the present improved Magnetic Compound Fluid (MCF). The MCF developed by K. Shimada, in 2001, was improved by the addition of α-cellulose, thereby achieving a clearance as great as 8 mm as given in another paper. This paper describes the possibility of the application of the MCF float polishing technique with α-cellulose. Firstly, the results obtained under various polishing conditions of the MCF float polishing technique are described. Secondly, many applications of proposed MCF float polishing technique are described. Finally, through experiments, we confirm that the proposed technique is very useful in the polishing field, especially, to polish some three-dimensional complex shapes. [Received 18 April 2007; Accepted 28 June 2007]

A 70-GHz Electron Cyclotron Resonance Heating System for Heliotron J

A 70-GHz electron cyclotron resonance heating (ECRH) system has been constructed in a helical-axis heliotron device, Heliotron J, in order to realize localized heating and current drive experiments. Since the Heliotron J plasma has a three-dimensional complex shape, the ECRH system is designed to satisfy the requirement of wide steering capability in both the toroidal and poloidal directions. The low-power transmission test shows that the beam radius of the focused Gaussian beam is 22 mm at the magnetic axis, which is small enough compared to the averaged minor plasma radius (170 mm), and the launching system covers a wide toroidal steering range from perpendicular to tangential injection by replacing the steering plane mirror. Since these characteristics satisfy the condition for controlling the power localization in the three-dimensional helical-axis configuration, it is possible to explore the on- and off-axis heating over most of the plasma radius (0 < r/a < 0.7) and the electron cyclotron current drive. In the high-power transmission test, the transmission efficiency of the 20-m corrugated waveguide is 92%, and the available output power to the vacuum vessel is up to 0.4 MW. Plasma production and heating are successfully performed using this ECRH system.

Experimental study on a high-temperature superconducting helical coil

High temperature superconductors (HTS) are expected to improve small-sized superconducting magnetic energy storage (SMES) systems. On the other hand, HTS conductors are extremely brittle so that the SMES with HTS coils requires special structural considerations to limit tensile stresses. We propose the concept of the force-balanced coil (FBC) which is a helically wound toroidal coil applied to SMES. The FBC can minimize the working stresses and reduce the mass of the structure for energy storage. However, the winding of the FBC is a three-dimensional complex shape so that it may be difficult to manufacture the helical windings without a decrease in the critical current of HTS conductors. To estimate the helical winding technique problems, we designed and fabricated a small helical coil using 340 m of Ag sheathed Bi-2223 HTS tapes. This paper describes the experimental results with liquid nitrogen cooling and a solution to the helical winding technique problems in order to prevent a drop in the critical current of HTS conductors.

Development of Helically Winding Machine for Force-Balanced Coil and Winding Technique

Strong electromagnetic force caused by high magnetic fields and coil current is a serious problem in Superconducting Magnetic Energy Storage (SMES) systems and magnetically confined fusion devices. In facing this problem, we proposed the concept of Force-Balanced Coil (FBC) applied to SMES and fusion devices. The FBC is a helically wound toroidal coil which balances the centering force with the hoop force. The helical winding of the FBC is modulated in order to reduce the torsional force. However, the winding of the FBC is a three-dimensional complex shape so that it may be difficult to manufacture the modulated helical windings. To overcome this difficulty, we developed a helically winding machine. In this paper, we discuss the winding techniques by using the winding machine and improve the shape of the helical windings from the view point of the reduction of the time consumed in winding the coil.

Application of the Free Mesh Method to Three-Dimensional Complex Shape.

The Free Mesh Method (FMM) is simple, accurate, and suitable for parallel processing. In this method, the connectivity between nodes and elements, that is essential in usual Finite Element Analysis, is not required. This paper describes a more efficient processing with local Voronoi diagram for preprocessing at the stage of creating a set of temporary local elements in the FMM. Adopting the surface patch model to describe analysis model, the present FMM was applied to three-dimensional complex shape. In the analysis of three-dimensional steady thermal conduction problems of complex geometry, the present method was shown to work in reasonable calculation time.