Multi-Scale Stereolithography Using Shaped Beams

2017 ◽  
Author(s):  
Huachao Mao ◽  
Yuen-Shan Leung ◽  
Yuanrui Li ◽  
Pan Hu ◽  
Wei Wu ◽  
...  
Keyword(s):  
Laser Beam ◽  
Tool Path ◽  
Three Dimensional ◽  
Laser Exposure ◽  
Micro Scale ◽  
Multi Scale ◽  
Good Surface ◽  
Single Scale ◽  
Macro Scale ◽  
Micro Patterns

Current Stereolithography (SL) can fabricate three-dimensional (3D) objects in a single scale level, e.g. printing macro-scale or micro-scale objects. However, it is difficult for the SL printers to fabricate a 3D macro-scale object with micro-scale features. In the paper a novel SL-based multi-scale fabrication method is presented to address such a problem. The developed SL process can fabricate multi-scale features by dynamically changing the shape and size of a laser beam. Different shaped beams are realized by switching apertures with different micro-patterns. The laser beam without using any micro-patterns is used to fabricate the macro-scale features, while the shaped laser beams with smaller sizes are used to fabricate micro-patterned features. Accordingly, the tool path planning method for the multi-scale fabrication process are developed so that macro-scale and micro-scale features can be built by using different layer thicknesses, laser exposure time, and scanning paths. Compared with the conventional SL process based on a fixed laser beam size, our process can fabricate multi-scale features in a 3D object. It also has fast fabrication speed and good surface quality.

scholarly journals Multiscale Stereolithography Using Shaped Beams

2017 ◽  
Vol 5 (4) ◽  
Author(s):  
Huachao Mao ◽  
Yuen-Shan Leung ◽  
Yuanrui Li ◽  
Pan Hu ◽  
Wei Wu ◽  
...  
Keyword(s):  
Laser Beam ◽  
Tool Path ◽  
Three Dimensional ◽  
Laser Beams ◽  
Laser Exposure ◽  
Beam Size ◽  
Scale Level ◽  
3D Objects ◽  
Good Surface ◽  
Single Scale

Current stereolithography (SL) can fabricate three-dimensional (3D) objects in a single-scale level, e.g., printing macroscale or microscale objects. However, it is difficult for the SL printers to fabricate a 3D macroscale object with microscale features. In the paper, a novel SL-based multiscale fabrication method is presented to address such a problem. The developed SL process can fabricate multiscale features by dynamically changing the shape and size of a laser beam. Different shaped beams are realized by switching apertures with different micropatterns. The laser beam without using micropatterns is used to fabricate macroscale features, while the shaped laser beams based on small apertures are used to fabricate micropatterned features. Accordingly, a tool path planning method for the multiscale fabrication process is presented to build macroscale and microscale features using different layer thicknesses, laser exposure time, and scanning paths. Compared with the conventional SL process using a fixed laser beam size, our process can manufacture multiscale features in a 3D object with fast fabrication speed and good surface quality.

scholarly journals On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 78 ◽  
Author(s):  
Gregory de Boer ◽  
Andreas Almqvist
Keyword(s):  
Surface Topography ◽  
Load Capacity ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Multiscale Methods ◽  
Operating Conditions ◽  
Real Surface ◽  
Micro Scale ◽  
Macro Scale ◽  
Heterogeneous Multiscale

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies.

Multi-scale density detection for yarn-dyed fabrics with deformed repeat patterns

2016 ◽  
Vol 87 (20) ◽  
pp. 2524-2540 ◽  
Author(s):  
Dejun Zheng ◽  
Lingheng Wang
Keyword(s):  
Computation Time ◽  
Registration Method ◽  
Decomposition Approach ◽  
Micro Scale ◽  
Detection Model ◽  
Multi Scale ◽  
Fabric Density ◽  
Macro Scale ◽  
Dyed Fabrics ◽  
Dyed Fabric

A new method combining the characteristics of macro-scale texture repeat patterns and micro-scale interwoven yarns of fabric images was proposed for yarn-dyed fabric density detection. The method was formulated in a research framework of multi-scale image processing and analysis. Firstly, a structure–texture decomposition approach was used to extract texture information and woven pattern details from the macro-scale fabric image. Secondly, a texture unit detection model was proposed to extract the texture units and to detect the yarn skewness in these texture units. Thirdly, a simple yet effective image registration method and a lightness gradient projection method were adopted to analyze the micro-scale fabric image and obtain the yarn locations in a texture unit. Finally, the average fabric density was calculated by coupling the near-regular features of texture units and yarn locations. The experiments showed that the proposed method was effective in detecting hundreds of yarns in the fabric samples and the computation time was very reasonable.

Characterization of “Bulk Lithography” Process for Fabrication of Three-Dimensional Microstructures

2013 ◽  
Vol 1 (4) ◽  
Author(s):  
Prasanna Gandhi ◽  
Kiran Bhole
Keyword(s):  
Laser Beam ◽  
Spatial Variation ◽  
Three Dimensional ◽  
Single Layer ◽  
Exposure Dose ◽  
Laser Exposure ◽  
Experimental Characterization ◽  
Gaussian Laser Beam ◽  
Lithography Process

Various ways of fabricating a three-dimensional (3D) component in a single-layer exposure using spatial variation of exposure dose have been presented in the literature. While some of them are based on dynamic mask process, more recently, a process based on varying intensity of a scanning Gaussian laser beam termed as “bulk lithography” has been proposed. In bulk lithography, the entire varying depth 3D microstructure gets fabricated because of spatial variation of intensity of laser imposed at every point in single layer scan. For the bulk lithography process, this paper first presents experimental characterization of unconstrained depth photopolymerization of resin upon exposure to Gaussian laser beam. Experimental characterization carried out for two resins systems: namely 1,6 hexane diol-diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA), over relatively wider range of Ar+ laser exposure dose and time, show behavior well beyond Beer–Lambert law. A unified empirical model is proposed to represent the nondimensional depth variation with respect to the time and energy of exposure for both resins. Finally, using these models, successful fabrication of several microstructures including micro-Fresnel lens, textured curved surface, otherwise difficult or impossible to fabricate, is demonstrated. Several advantages of the bulk lithography as compared to other similar processes in the literature are highlighted.

Degradation Modeling Research of Biodegradable Tissue Engineering Scaffold

2013 ◽  
Vol 873 ◽  
pp. 642-651
Author(s):  
Tao Hong Zhang ◽  
Shou Gang Xu ◽  
De Zheng Zhang ◽  
Aziguli Wulamu
Keyword(s):  
Tissue Engineering ◽  
Initial Step ◽  
Tissue Engineering Scaffold ◽  
Multi Scale ◽  
Modeling Methods ◽  
Degradation Modeling ◽  
Scale Modeling ◽  
Single Scale ◽  
Macro Scale ◽  
Scale Models

Although the degradation modeling of tissue engineering scaffold is in its initial step, it can direct the design, optimization of scaffold and help the application in medical case of illness. This paper analyzes the modeling methods and gives the speciality of every model which is put forward by researchers in China and abroad about the degradation of tissue engineering scaffold. These models are divided into micro scale, macro scale and two scale models based on the modeling scales. The recent research is belonging to single scale modeling. Some researchers abroad probed to two scale modeling. The future model is prospected in multi scale coupling macro, micro, and meta-macro model.

Multi-scale finite element modeling of 3D printed structures subjected to mechanical loads

2018 ◽  
Vol 24 (1) ◽  
pp. 177-187 ◽  
Author(s):  
Dalia Calneryte ◽  
Rimantas Barauskas ◽  
Daiva Milasiene ◽  
Rytis Maskeliunas ◽  
Audrius Neciunas ◽  
...  
Keyword(s):  
Finite Element ◽  
Composite Structures ◽  
Computational Models ◽  
Three Dimensional ◽  
Structural Response ◽  
Content Type ◽  
Multi Scale ◽  
Macro Scale ◽  
Internal Constitution ◽  
3D Printed

Purpose The purpose of this paper is to investigate the influence of geometrical microstructure of items obtained by applying a three-dimensional (3D) printing technology on their mechanical strength. Design/methodology/approach Three-dimensional printed items (3DPI) are composite structures of complex internal constitution. The buildup of the finite element (FE) computational models of 3DPI is based on a multi-scale approach. At the micro-scale, the FE models of representative volume elements corresponding to different additive layer heights and different thicknesses of extruded fibers are investigated to obtain the equivalent non-linear nominal stress–strain curves. The obtained results are used for the creation of macro-scale FE models, which enable to simulate the overall structural response of 3D printed samples subjected to tensile and bending loads. Findings The validation of the models was performed by comparing the computed results against the experimental ones, where satisfactory agreement has been demonstrated within a marked range of thicknesses of additive layers. Certain inadequacies between computed against experimental results were observed in cases of thinnest and thickest additive layers. The principle explanation of the reasons of inadequacies takes into account the poorer quality of mutual adhesion in case of very thin extruded fibers and too-early solidification effect. Originality/value Flexural and tensile experiments are simulated by FE models that are created with consideration to microstructure of 3D printed samples.

Finite Element Modeling of Multi-Scale Thermal Contact Resistance

2008 ◽  
Author(s):  
M. K. Thompson
Keyword(s):  
Finite Element ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Unit Area ◽  
Thermal Contact ◽  
Contact Model ◽  
Micro Scale ◽  
Multi Scale ◽  
Macro Scale ◽  
Scale Surface

Many traditional macro scale finite element models of thermal contact systems have incorporated the effect of micro scale surface topography by applying a constant value of thermal contact conductance (TCC) per unit area to the regions in contact. However, it has been very difficult to determine an appropriate TCC value for a given system and analysts typically had to rely on experimental data or values from the literature. This work presents a method for predicting micro scale TCC per unit area by incorporating micro scale surface roughness in a multi-scale iterative thermal/structural finite element contact model. The resulting TCC value is then used in a macro scale thermal/structural contact model with apparent surface form to predict the thermal contact resistance and overall thermal resistance for a commercial power electronics module.

scholarly journals Micro- and Macro-Scale Measurement of Flow Velocity in Porous Media: A Shadow Imaging Approach for 2D and 3D

Optics ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 71-87 ◽  
Author(s):  
Reza Sabbagh ◽  
Mohammad Amin Kazemi ◽  
Hirad Soltani ◽  
David S. Nobes
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Flow Pattern ◽  
Flow Measurement ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Detailed Knowledge ◽  
Micro Scale ◽  
Macro Scale

Flow measurement in porous media is a challenging subject, especially when it comes to performing a three-dimensional (3D) velocimetry at the micro scale. Volumetric flow measurement techniques such as defocusing and tomographic imaging generally involve rigorous procedures, complex experimental setups, and multi-part data processing procedures. However, detailed knowledge of the flow pattern at the pore and subpore scales is important in interpreting the phenomena that occur inside the porous media and understanding the macro-scale behaviors. In this work, the flow of an oil inside a porous medium is measured at the pore and subpore scales using refractive index matching (RIM) and shadowgraph imaging techniques. At the macro scale, flow is measured using the particle image velocimetry (PIV) method in two dimensions (2D) to confirm the volumetric nature of the flow and obtain the overall flow pattern in the vicinity of the flow entrance and at the far field. At the micro scale, the three-dimensional (3D) flow within an arbitrary volume of the porous medium was quantified using 2D particle-tracking velocimetry (PTV) utilizing the law of conservation of mass. Using the shadowgraphy method and a single camera makes the flow measurement much less complex than the approaches using laser light sheets or multiple cameras with multiple viewing angles.

scholarly journals Three-dimensional laser printing of macro-scale glass objects at a micro-scale resolution

2020 ◽  
Author(s):  
Peng Wang ◽  
Wei Chu ◽  
Xiaolong Li ◽  
Zijie Lin ◽  
Jian Xu ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Micro Scale ◽  
Laser Printing ◽  
Macro Scale

scholarly journals Homogenization of fully nonlinear rod lattice structures: on the size of the RVE and micro structural instabilities

2021 ◽  
Author(s):  
Ludwig Herrnböck ◽  
Paul Steinmann
Keyword(s):  
Large Deformations ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Homogenization Method ◽  
Volume Element ◽  
Lattice Structures ◽  
Micro Scale ◽  
Macro Scale ◽  
Unit Cells ◽  
Structural Instabilities

AbstractThis work investigates the possibility of applying two-scale computational homogenization to rod lattice structures emerging, for instance, from additive manufacturing. The influence of the number of unit cells within the representative volume element (RVE), thus, the RVE’s size on the homogenized mechanical response is studied for occurring microscopic structural instabilities. Therein, the macro-scale, described in terms of three-dimensional continuum mechanics, is coupled to the micro-scale described by geometrically exact rods, enabling arbitrary large deformations and rotations. A special feature of the presented framework is that the rods building the lattice structures are not restricted to deform purely elastically but may deform inelastically. The mechanical response of lattice structures is investigated by applying the developed homogenization method to an exemplary lattice. Under special loads the structure reaches an instable state and may buckle. The appearance of instabilities depends on the geometric properties of the lattice’s underlying rods and the RVE’s size.

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