햅틱 렌더링을 위한 거리 영역과 포인트 쉘 기반의 실시간 변형체 충돌 검사

김석(Seok Kim),박진아(Jinah Park) 한국정보과학회 2011 정보과학회논문지 : 소프트웨어 및 응용 Vol.38 No.7

거리 영역(Distance Field)과 포인트 쉘(Point Shell)을 이용한 충돌 검사는 물체들 사이의 충돌 여부를 빠르게 계산할 수 있는 효율적인 방법 중 하나이다. 거리 영역은 물체를 감싸는 3차원 균일 격자로 정의되고, 포인트 쉘은 물체 표면을 샘플링한 점들의 집합으로 정의된다. 이 때, 거리 영역의 각 격자 점은 감싼 물체와의 최단 표면거리 값을 가지고 있으며, 이 값은 해당 격자 점이 물체의 내부 혹은 외부에 위치하느냐에 따라 달라진다. 이러한 값들을 보간하여 포인트 쉘의 각 점들과 거리 영역이 감싸는 물체와의 거리 및 그 값의 부호를 빠르게 계산하고, 이로부터 두 물체의 충돌을 검사한다. 그러나 이 방법은 물체가 변형할 경우 이를 반영하기 위한 거리 영역의 업데이트가 느리다는 단점이 있다. 본 논문에서는 이와 같은 문제점을 해결하고자 느린 업데이트의 원인인 격자 점의 최단 표면거리 값이 아닌 격자 점들이 형성하는 격자 셀을 이용한 충돌 처리 방법을 제안한다. 이 방법은 격자 셀을 감싼 물체와의 상대적 위치에 따라 표면 셀, 내부 셀, 외부 셀의 세 가지로 구분한다. 그렇게 구분된 격자 셀과 포인트 쉘의 점들을 이용하여 변형체들 사이의 충돌 검사를 진행한다. 제안한 방법의 가장 큰 특징은 기존 방법에 비해 충돌 검사 시간은 비슷하면서 물체 변형 시 업데이트가 비약적으로 빠르다는 것이다. 본 논문에서는 이러한 제안 방법을 이용하여 실제 수술 시뮬레이션 중 하나인 담낭 절제 수술을 적용하였다. Collision detection using Distance Field and Point Shell is one of efficient methods to detect collision between objects in interactive simulation. The Distance Field is defined as 3D uniform grid, but the Point Shell denotes the set of points which are sampled from an object. In the Distance Field, each grid point has the signed shortest distance from the surface of an object within the Distance Field. By interpolating the distance of grid points, it is possible to calculate the distance between each sampled point of Point Shell and the object within the Distance Field. The result is used to detect collision fast. However, when the object within the Distance Field is deformed, the update of the Distance Field is too slow because the shortest surface distance of all grid points must be recomputed. In this paper, we present new approach to detect collision of deformable objects using grid cells instead of shortest distance of grid point. In our approach, each grid cell is defined one of three types based on the relative position of the object within the Distance Field; boundary cell, interior cell, and exterior cell. By using the grid cells of Distance Field and sampled points of Point Shell, we introduce fast collision detection for deformable objects. The advantage of our approach is to reduce the time required to update Distance Field. In addition, our approach is applied to Cholecystectomy simulation which is one of common surgeries.

Electric Deformation of a Bubble in a Uniform Electric Field

Kwon, Young Chul,Kwon, Jeong Tae,Cho, Hye Jung,Kim, Dae Hoon,Lee, Sang Heon 한국공업화학회 2005 Journal of Industrial and Engineering Chemistry Vol.11 No.3

Theoretical and numerical analyses have been carried out to investigate the electric deformation of a spherical free bubble in a uniform electric field. In the limit of small deformation, the steady-state deformation of a free bubble in an electric field has been considered. The electric field strength and the electric normal stress at the bubble interface and free energy and volume change of a bubble have been investigated. In addition. the bubble shape and the electric potential in an electric field have been calculated numerically. The boundary-fitted orthogonal coordinate system generated numerically has been employed. The electric normal stress is the largest at the equator (θ = π /2) of the bubble. causing the spherical bubble to deform into an elliptical one. As the electric Weber number increases, the bubble volume decreases linearly. The numerical results also show that the bubble is elongated and becomes more extended as the electric field strength increases. The aspect ratio increases upon increasing the electric Weber number.

Reduction of Energy Comsumptiuon and Thermal Deformation in WEDM by Magnetic Field Assisted Technology

Yanming Zhang,Zhen Zhang,Guojun Zhang,Wenyuan Li 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.2

Energy consumption and machining accuracy are considered to be two important attributes of performance indicators for green operations of wire electric discharge machining (WEDM). However, there is a paucity of studies that focus on the energy consumption and geometric error caused by thermal deformation. In this paper, a hybrid technique of WEDM with assisted magnetic field (MF) is proposed for enhancing machining performance to reduce energy consumption and thermal deformation. Based on the principles of thermal deformation, energy consumption, and magnetic field-assisted WEDM, a set of experiments is conducted to investigate thermal deformation and energy consumption of MF-assisted WEDM and conventional WEDM machining of Inconel 718. The effects of magnetic field on thermal deformation, discharge waveforms, surface integrity, and energy consumption are analyzed, and it is concluded that the proposed hybrid technique of MF-assisted WEDM offers numerous advantages and potential for applications in the green precision manufacturing field.

Identification of Dynamic Flow Stress Curves using the Virtual Fields Methods: Theoretical Feasibility Analysis

Dohyun Leem,Jin‑Hwan Kim,Frédéric Barlat,Jung Han Song,Myoung‑Gyu Lee 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2

An inverse approach based on the virtual fields method (VFM) is presented to identify the material hardening parametersunder dynamic deformation. This dynamic-VFM (D-VFM) method does not require load information for the parameteridentification. Instead, it utilizes acceleration fields in a specimen’s gage region. To investigate the feasibility of the proposedinverse approach for dynamic deformation, the virtual experiments using dynamic finite element simulations were conducted. The simulation could provide all the necessary data for the identification such as displacement, strain, and accelerationfields. The accuracy of the identification results was evaluated by changing several parameters such as specimen geometry,velocity, and traction boundary conditions. The analysis clearly shows that the D-VFM which utilizes acceleration fields canbe a good alternative to the conventional identification procedure that uses load information. Also, it was found that properdeformation conditions are required for generating sufficient acceleration fields during dynamic deformation to enhance theidentification accuracy with the D-VFM.

Weight Functions for Notched Structures with Anti-plane Deformation

Deuk-Man An,In-Ho Son 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.3

Weight functions in Facture mechanics represent the stress intensity factors as weighted averages of the externally impressed boundary tractions and body forces. We extended the weight function theory or cracked linear elastic materials to calculate the notch stress intensify factor of a notched structure with anti-plane deformation. The well-known method of deriving weight functions by differentiation cannot be used for notched structures. By combining an appropriate singular field with a regular field. we derived weight functions for the notch stress intensity factor. Closed expressions of weight functions for notched cylindrical bodies are given as examples.

Numerical study of the residual stress and welding deformation of mid-thick plate of AA6061-T6 in the multi-pass MIG welding process

Shusen Zhao,Yanmin Li,Rui Huang,Zhanshu He 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.11

In this paper, three methods of adding and activating weld bead elements, i.e., adding and activating the weld bead segment by segment (case A), adding and activating one weld pass after another (case B), and modified adding and activating one weld pass after another (case C), were employed to establish the corresponding simulation model of a butt joint of AA6061-T6 mid-thick plate with a double-pass weld by ABAQUS. The welding temperature field, residual stress field, and welding deformation were simulated. The heat loss of three methods in the welding simulation was tested by theoretical calculation. To verify the simulation results, the metal-inert gas (MIG) welding experiment was also performed, and the molten pool dimensions, residual stress, and welding deformation were measured. The results show both cases A and C can be effectively employed to predict residual stress, and case C can also save computing time. Case A can more accurately predict the welding deformation.

ZnO nanowire lines and bundles: Template-deformation-guided alignment for patterned field-electron emitters

Jizhong Song,Xue Ning,Haibo Zeng 한국물리학회 2015 Current Applied Physics Vol.15 No.11

One-dimensional ZnO materials have been promising for field-emission (FE) application, but how to facially control the alignment of ZnO emitters is still a great challenge especially for patterned display application. Here, we report the fabrication of novel ZnO nanowire (NW) line and bundle arrays for patterned field-electron emitters. The effects of PS template size and heating time on the resulted ZnO nanoarrays were systematically studied. The deformation degree of PS templates was controlled and hence utilized to adjust the alignment of electrochemically deposited ZnO arrays. It was found that the length of NW lines and the density of NW bundles can effectively tuned by the PS template heating time. The optimal FE performance with turn-on electric field as low as of 4.4 V μm-1 and the fieldenhancement factor as high as of 1450 were achieved through decreasing the screening effect among the patterned field-electron emitters.

Cut out effect on nonlinear post-buckling behavior of FG-CNTRC micro plate subjected to magnetic field via FSDT

Jamali, M.,Shojaee, T.,Mohammadi, B.,Kolahchi, R. Techno-Press 2019 Advances in nano research Vol.7 No.6

This research is devoted to study post-buckling analysis of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) micro plate with cut out subjected to magnetic field and resting on elastic medium. The basic formulation of plate is based on first order shear deformation theory (FSDT) and the material properties of FG-CNTRCs are presumed to be changed through the thickness direction, and are assumed based on rule of mixture; moreover, nonlocal Eringen's theory is applied to consider the size-dependent effect. It is considered that the system is embedded in elastic medium and subjected to longitudinal magnetic field. Energy approach, domain decomposition and Rayleigh-Ritz methods in conjunction with Newton-Raphson iterative technique are employed to trace the post-buckling paths of FG-CNTRC micro cut out plate. The influence of some important parameters such as small scale effect, cut out dimension, different types of FG distributions of CNTs, volume fraction of CNTs, aspect ratio of plate, magnitude of magnetic field, elastic medium and biaxial load on the post-buckling behavior of system are calculated. With respect to results, it is concluded that the aspect ratio and length of square cut out have negative effect on post-buckling response of micro composite plate. Furthermore, existence of CNTs in system causes improvement in the post-buckling behavior of plate and different distributions of CNTs in plate have diverse response. Meanwhile, nonlocal parameter and biaxial compression load on the plate has negative effect on post-buckling response. In addition, imposing magnetic field increases the post-buckling load of the microstructure.

게임환경에서 이용 가능한 프랙탈 오브젝트 변형에 관한 연구

송행숙,한영덕 한국게임학회 2005 한국게임학회 논문지 Vol.5 No.1

게임환경에서 자연물의 표현에 프랙탈을 이용한 경우, 주변의 힘 등에 의한 자연스러운 변형이 구현되어야 보다 사실감을 느낄 수 있다. 일반적인 연속적 변형의 특징과 프랙탈적 특징을 모두 갖는 변형을 코드변환을 도입하여 생성하는 다양한 방법을 예시하였다. To get the realistic deformation of fractal objects in computer games, fractal-like deformation property should be added to ordinary continuous deformations. We, here, suggest a fractal-like vector fields producing method using the code and its modification, and some examples are given.

Numerical and Experimental Study on Effect of Different Types of Field-Shaper on Electromagnetic Terminal-Wire Crimping Process

Ashish K. Rajak,Ramesh Kumar,Hirak Basumatary,Sachin D. Kore 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.3

Electromagnetic terminal-wire crimping (EMTWC) is a type of mechanical joining process. In EMTWC, the terminal is deformed over the wire strands plastically to enhance the mechanical strength by increasing the contact area. A well-crimped electrical interconnection helps to avoid harmful configurations by reducing sparks, overheating, power losses etc. Subsequently, the challenge to minimize various disadvantages of conventional mechanical terminal-wire crimping process like non-uniform deformation, decreased durability, cracks, etc., can be overcome by the electromagnetic crimping process. In this work, application of the fieldshaper has been proposed to concentrate the magnetic pressure at the desired location for effective wire crimping. Numerical analysis was carried out using LS-DYNATM on three different types of field-shaper namely single-step, double-step and tapered. In all the three field-shaper, the total length, the outer diameter and the effective working length were constant. The samples used was an aluminum terminal and seven strands of aluminum wires which are commercially used for making electrical inter connections. Experiments were carried out based on the results obtained through numerical analysis. Experimental and numerical results were in agreement and the error was less than 10%. The efficiency of single-step field-shaper was found to be better compared to double-step and tapered fieldshaper.