주조공정에서의 효율적인 열응력 해석을 위한 이종해석기법의 연계

곽시영(Si Young Kwak),임채호(Chae Ho Lim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.8

본 논문에서 유한차분법(FDM)과 유한요소법(FEM)을 연계하여 주조공정 해석을 수행하는 이종해석기법을 제안하였다. 수치해석기법으로는 FDM, FEM, BEM 등 다양한 기법이 있으며, 대부분의 공학문제는 각각의 현상에 적합한 수치해석기법을 사용하여 해석을 수행하고 있다. 일반적으로, FDM 또는 FVM 은 유동 및 열전달 해석에, FEM 은 열응력 해석에 많이 적용되고 있지만 복합적인 공학 문제를 해결하기 위해서 각각 수치해석기법을 연동한 해석의 필요성이 점점 증가하고 있다. 따라서, 본 논문에서는 3 차원 공간에서 FDM 을 사용하여 응고 및 열 전달 해석을 수행하고, 계산된 온도 데이터를 FEM 해석장에 적합하게 변환하여 열응력 해석을 수행하는 FDM/FEM연계해석 방법을 제시하였다. 그리고 제시한 해석방법을 주조 공정 해석에 적용한 결과, 요소생성 등의 해석작업과 해석속도 면에서 효율적으로 해석을 수행할 수 있었다. This paper proposes a method that involves a combination of FDM and FEM for analyzing casting process. At present, many numerical analysis methods such as FDM, FEM, and BEM are used for solving engineering problems. For a given problem, a specific method that is suited to the problem is adopted; in general, FDM or FVM is favored for problems related to fluid flow or heat transfer, and FEM is adopted in stress analysis. However, there is an increasing need for using a combined method for complex and coupled phenomena analysis. Hence, we proposed a method in which FDM and FEM are coupled in three-dimensional space, and we applied this method to analyze casting process. In the proposed method, solidification and heat transfer was analyzed by using FDM. The field data such as temperature distribution were converted into a format suitable for FEM analysis that was used for calculating thermal stress distribution. Using the proposed method, we efficiently analyzed the analysis process from the viewpoints of work and time.

Tensile Properties and Stiffnesses of 3D-printed Lace/Voile Composite Fabrics Manufactured by Various Roller Processes

이선희 한국섬유공학회 2019 한국섬유공학회지 Vol.56 No.1

The objective of this study was to develop lace-style 3D printed textiles using thermoplastic polyurethane filaments for 3D printing by fused deposition modeling. Composite voile textiles with lace motifs of different sizes were produced by various roller press processes. The textiles were characterized according to their tensile behaviors, tensile characteristics, and stiffnesses. The analysis of tensile characteristics revealed that the 3dLaceM1 textile with a big pattern had a maximum load of 13.2 kgf and an elongation of 274.3%. Moreover, as the size of the lace motif decreased, the maximum load value tended to decrease, while the elongation value tended to increase. The composite 3D-printed lace/voile textile (3dLaceM1/voile), which was produced by a roller press, had a maximum load of 35.4 kgf and an elongation of 383.9%. The initial modulus of 3dLaceM1/voile was 20.56 kgf/mm2, which was more than six times that of the 3D-printed lace textile that was produced by the roller press process. The stiffness of the 3D-printed lace textile tended to decrease with the size of the lace motif. In addition, the 3D-printed lace that was produced with the roller press process exhibited more flexible characteristics. Furthermore, the stiffness of the composite 3D-printed lace/voile textile was higher than that of the conventional 3D-printed lace textile. Thus, the tensile characteristics and stiffnesses of textiles could be customized for specific uses through process control of the 3D-printed lace.

Morphology and Compressive Property of 3D-printed 3-pointed Star Shape Prepared Using Lightweight Thermoplastic Polyurethane

Xiaokui Chen,이선희 한국섬유공학회 2022 Fibers and polymers Vol.23 No.7

In this study, a 3-pointed star shape was manufactured using lightweight thermoplastic polyurethane under FDM3D printing process conditions. Specifically, we modeled 3-pointed star-shaped auxetic structures with different thicknessesand samples obtained through a FDM 3D printing process using LW-TPU materials. Their morphologies, specific gravities,thermal properties, and compression characteristics were investigated under the nozzle temperatures of 200 ℃, 220 ℃, and240 ℃. The results of LW-TPU filaments analysis confirmed the presence of microspheres with foaming performance atextrusion temperatures above 200 ℃. Regarding the compression characteristics of the 3-pointed star-shaped materials, itwas found that higher printing temperatures were associated with lower compressive deformation rates and highercompressive strengths. This study shows that 3-pointed star-shaped structures having various compression characteristics canbe 3D printed using LW-TPU material and specific nozzle temperatures.

A Study on the Effects of the Corrugated Angle on Low Velocity Impact Characteristics of the Lightweight Sandwich Plate with Corrugated Cores Produced by FDM Process

장용훈(Yong Hun Jang),안동규(Dong-Gyu Ahn),신보성(Bo Sung Shin) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.12

The development of the lightweight sandwich plate with periodically repeated cores is one of hot issues to reduce the weight of the part. The behavior of the sandwich plate under static and dynamic loads is greatly influenced by the design of the cores. The aim of this paper is to investigate the effects of the corrugated angle on low velocity impact characteristics of the lightweight sandwich plate with corrugated cores. The corrugated core with the fold surface is designed to improve the joining characteristics between cores and skin sheets. The corrugated angle of the corrugated cores ranges from 45o to 90o. Specimens are manufactured from the fused deposition modeling (FDM) process. The characteristics of the fabricated specimen are investigated. Impact experiments are performed using a drop impact tester with a stretching type of fixture and the hemispherical nose of the impact head. From the results of the experiments, the influence of the impact energy and corrugated angle on the failure pattern of the lightweight sandwich plate is examined. The effects of the corrugated angle on critical impact energies for different failure patterns are investigated. Finally, the failure map of the lightweight sandwich plate with corrugated cores is estimated.

Effect of Process Parameters on Mechanical Strength of Fabricated Parts using the Fused Deposition Modelling Method

Lan P. T. Huynh,Huy A. Nguyen,Huy Q. Nguyen,Loc K. H. Phan,Thanh T. Tran 한국정밀공학회 2019 한국정밀공학회지 Vol.36 No.8

This study investigated the effects of process parameters on mechanical properties of fabricated parts of the Polylactic acid (PLA) materials using fused deposition modeling (FDM) in 3D printing Technology. First, Taguchi method in the design of experiment (DOE) approach was applied to generate a design matrix of three process parameters namely; printing speed, extrusion temperature and layer thickness. A L9 array with 9 specimens was used for fabrication under various process parameters by the Builder 3D printer. Tensile test was implemented and recorded in accordance with ASTM D368 standard. Achieved data were analyzed using the Minitab software to show the effect of each process parameter on mechanical properties. Secondly, a regression model was developed to predict the trend of response in case of change in setting of parameters and estimating the optimal set of process parameters which creates the strongest FDM parts. The achieved optimum parameters were used to validate the fabricated samples for tensile testing. According to the results, the best mechanical strength of fabricated parts was achieved with printing speed of 48 mm/s, extrusion temperature of 220 degree of celsius (C) and the layer thickness of 0.15 mm. Also, the extrusion temperature was the most influencing factor on ultimate tensile stress.

Development of Hybrid-FDM Process Using Automatic Tool Changer for Multi-Material Production and Post-Processing

최성민(Sung Min Choi),샤오젠(XiaoJian),박인백(In Baek Park),이석희(Seok Hee Lee) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.3

The purpose of this study is an attempt to improve the functionality of a conventional Fused Deposition Modeling (FDM) process using the Automatic Tool Changer (ATC) to perform multimaterial production and post-processing. Hybrid-FDM means a fusion of an Additive Manufacturing process and grinding process using the ATC system. In order to enhance the potentiality of production capacity for multi-material fabrication and surface roughness improvement, two extrusion tools and one grinding tool system are suggested. A pneumatic chuck is attached on a moving platform in the XY axes plane and an extrusion head and grinding head are placed in a docking station, allowing for a quick changeover with each other. Therefore, the manufacturing lead time can be reduced efficiently for the fabrication of a product.

Methodology to quantify rock behavior around shallow tunnels by Analytic Hierarchy Process and Fuzzy Delphi Method

유영일,송재준 한국자원공학회 2008 Geosystem engineering Vol.11 No.2

For the quantitative identification of rock behavior in shallow tunnels, we recommend using the rock behavior index (RBI) by combining the analytic hierarchy process (AHP) and the fuzzy Delphi method (FDM). AHP can aid engineers in effectively determining complex and un-structured rock behavior utilizing a structured pair-wise comparison matrix. FDM can assist them to overcome the uncertainty in the expert judgment. Rock behavior types are categorized as rock fall, cave-in, and plastic deformation. Seven parameters influencing rock behavior are determined: uniaxial compressive strength (UCS), rock quality designation (RQD), joint surface condition, stress, ground water, earthquake, and tunnel span. They are classified into rock mass intrinsic, rock mass extrinsic, and design parameters. An advantage of this procedure is its ability to obtain each parameter’s weighting. We applied the proposed method to the basic design of Seoul Metro Line 9 and quantified the rock behavior into RBI on rock fall, cave-in, and plastic deformation. The study results demonstrate that AHP can give engineers quantitative information on rock behavior. For the quantitative identification of rock behavior in shallow tunnels, we recommend using the rock behavior index (RBI) by combining the analytic hierarchy process (AHP) and the fuzzy Delphi method (FDM). AHP can aid engineers in effectively determining complex and un-structured rock behavior utilizing a structured pair-wise comparison matrix. FDM can assist them to overcome the uncertainty in the expert judgment. Rock behavior types are categorized as rock fall, cave-in, and plastic deformation. Seven parameters influencing rock behavior are determined: uniaxial compressive strength (UCS), rock quality designation (RQD), joint surface condition, stress, ground water, earthquake, and tunnel span. They are classified into rock mass intrinsic, rock mass extrinsic, and design parameters. An advantage of this procedure is its ability to obtain each parameter’s weighting. We applied the proposed method to the basic design of Seoul Metro Line 9 and quantified the rock behavior into RBI on rock fall, cave-in, and plastic deformation. The study results demonstrate that AHP can give engineers quantitative information on rock behavior.

Methodology to quantify rock behavior around shallow tunnels by Analytic Hierarchy Process and Fuzzy Delphi Method

Yoo, Young-Il,Song, Jae-Joon 한국암반공학회 2008 Geosystem engineering Vol.11 No.2

For the quantitative identification of rock behavior in shallow tunnels, we recommend using the rock behavior index (RBI) by combining the analytic hierarchy process (AHP) and the fuzzy Delphi method (FDM). AHP can aid engineers in effectively determining complex and un-structured rock behavior utilizing a structured pair-wise comparison matrix. FDM can assist them to overcome the uncertainty in the expert judgment. Rock behavior types are categorized as rock fall, cave-in, and plastic deformation. Seven parameters influencing rock behavior are determined: uniaxial compressive strength (UCS), rock quality designation (RQD), joint surface condition, stress, ground water, earthquake, and tunnel span. They are classified into rock mass intrinsic, rock mass extrinsic, and design parameters. An advantage of this procedure is its ability to obtain each parameter s weighting. We applied the proposed method to the basic design of Seoul Metro Line 9 and quantified the rock behavior into RBI on rock fall, cave-in, and plastic deformation. The study results demonstrate that AHP can give engineers quantitative information on rock behavior.

An additive manufacturing benchmark artifact and deviation measurement method

Nikola Vorkapic,Milos Pjevic,Mihajlo Popovic,Nikola Slavkovic,Sasa Zivanovic 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7

Additive manufacturing (AM) is established as a new class for fabricating 3D physical prototypes layer by layer. Given that a large number of different 3D printers (AM machines) are present now (as a product of renowned manufacturers or custom-made products), the design of a benchmark artifact for evaluation of the AM processes is very important. This implies quality evaluation of the capabilities and limitations of each AM process and also the geometrical testing of the 3D printers. The paper proposes a benchmark artifact, according to the criteria for modeling of the benchmark artifact, with a large number of basic features for its geometrical evaluation. Although there are a large number of commercial software packages, this paper also proposes a low-cost developed measurement method of geometrical deviation that could be also adjustable for requirements in an easy way. Verification of the proposed deviation measurement method has been done by several experiments. The experiments include fabrication of the proposed benchmark artifact on available 3D printers by an FFF (fused filament fabrication) process also known as FDM (fused deposition modeling), and after that its scanning. Verification is done by comparing quality evaluation of each fabricated part by developed method and commercial software.

Hydration Deformation Behaviors of Scaffolds of Tricalcium Silicate/Tricalcium Aluminate Mixtures Printed Using the Fused Deposition Modelling (FDM)

구영진,이명현,윤석영,이윤주 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.4

3D printing technology has advanced rapidly over the last decade. However, for ceramic materials, drying and sintering steps are required after printing, and excessive shrinkage that occurs during these steps is a major factor that has hindered the development of the ceramic 3D printing technology. In this study, a non-sintering ceramic 3D printing method was developed using a hydraulic material to overcome the size deformation issue encountered during the post-processing of a scaffold-type printed green body. The deformation characteristics occurring during the curing process were confirmed. Tricalcium silicate (C3S) and tricalcium aluminate (C3A), which are well-known hydraulic materials, were selected. They were prepared into a printable paste by mixing with a viscous hydrophilic oil such as polyethylene glycol and polypropylene glycol, which helped the printout survive without collapse while it was cured. The scaffold was printed by Fused Deposition Modelling (FDM), which is the simplest and most economical printing method, and was cured by immersion in a water bath. The hydrated scaffold of the C3S/C3A mixture exhibited a smaller strain than the scaffold of the single materials, and the deformation amount depended on the printing direction. Remarkably, a scaffold with the smallest deformation, of less than 1%, and the highest compressive strength was obtained with a C3S/C3A mixing ratio of 65/35.