The Computational Mechanics & Design Optimization Lab, located within the School of Mechanical Engineering at Korea University, focuses on computational mechanics and design optimization.

고려대학교 기계공학부 소속 전산역학 및 설계 최적화 연구실에서는 전산 역학 및 설계 최적화 연구를 수행한다.

A generalized direct inverse mass matrix for the method of finite spheres in transient explicit wave propagation analysis

Graph Attention Network-Based Surrogate Model for Acceleration and Generalization of Injection Molding Simulations

Effect of chip-induced powder size distribution on 18Ni maraging steel in hybrid addictive manufacturing

Implicit s-sub-step time integration schemes with (s+1)th-order accuracy and dissipation control

Deep Learning-based Real-Time Estimation of Transcranial Focused Ultrasound Acoustic Field

Progressive DNN-metaheuristics for programmable broadband mechanical metamaterial absorbers design

Impact of considering bone remodelling in risk assessment of mandibular implant-supported bridges

Surrogate-Assisted Kriging Training Utilizing Boxplot and Correlation Coefficient for Large-Scale Data

Multi-modal networks for real-time monitoring of intracranial acoustic field during transcranial focused ultrasound therapy

Fabrication-specific simulation of Mn-Zn ferrite core-loss for machine learning-based surrogate modeling with limited experimental data

Biomechanical analysis of alveolar bones with compromised quality supporting a 4-unit implant bridge; a possible association with implant-related sequestration (IRS)

Explicit dynamics with the method of finite spheres using a modified direct
inverse mass matrix

Stability of the Bathe implicit time integration methods in the presence of physical damping

Auxetic Pattern Design for Concentric-tube Robots Using an Active DNN-Metaheuristics Optimization

Learned Gaussian Quadrature for Enriched Solid Finite Elements

Design of Patterns in Tubular Robots Using DNN-Metaheuristics Optimization

Imposing displacements in implicit direct time integration & a patch test

Automated vector analysis to design implant-supported prostheses: A dental technique

Deep Neural Network for Navigation of a Single-element Transducer during Transcranial Focused Ultrasound Therapy: Proof of Concept

Biomechanical effects of bone quality and design features in dental implants in long-term bone stability

Effects of assessing the bone remodeling process in biomechanical finite elementstability evaluations of dental implants

Time splitting ratio in the rho_infinity-Bathe time integration method for higher-order accuracy in structural dynamics and heat transfer

Effects of implant diameter, implant-abutment connection type and bone density on biomechanical stability of implant components and the surrounding bone: A finite element analysis study

Design optimization of asymmetric patterns for variable stiffness of continuum tubular robots

Design process of patient-specific osteosynthesis plates using topology optimization

Selecting the load at the intermediate time point of the rho_infinity-Bathe time integration scheme

Robotic Camera Calibration to Maintain Consistent Precision of 3D Trackers

Effect of mandibular contouring surgery on the stress distribution during various clenching tasks

Biomechanical effect of implant diameter, connection type and bone density on microgap formation and fatigue failure: A finite element analysis

Implant placement in the implant-supported mandibular advancement device for completely edentulous patients: A finite element study

Biomechanical stress and microgap analysis of bone-level and tissue-level implant abutment structure according to the five different directions of occlusal loads

Three-Dimensional Evaluation of Peri-implant Soft Tissue When Tapered Implants Are Placed: Pilot Study with Implants Placed Immediately or Early Following Tooth Extraction

Effect of passive support of the spinal muscles on the biomechanics of a lumbar finite element model

Designing a mandibular advancement device with topology optimization for a partially edentulous patient

Biomechanical stability of internal bone level implant: Dependency on hexagonal or non-hexagonal structure connection

Practical bending angle calculation for an automated surgical plate bending apparatus

An analysis of implicit time integration schemes for wave propagations

Biomechanical Analysis of a Mandibular Advancement Device (MAD) with Various Implant Placements in Complete Edentulous Patients

Artificial Neural Network-Based Gaussian Quadrature for the Method of Finite Spheres

Biomechanical Effects of Retention Types (Cement and Screw-Cement Retained Prosthesis) in Implant Prosthesis

Effects of cementless fixation of implant prosthesis: A finite element study

For direct time integrations: a comparison of the Newmark and rho_infinity-Bathe schemes

A novel motorized bending apparatus for surgical plates

Biomechanical analysis of 4 types of short dental implants in a resorbed mandible

The Bathe time integration method with controllable spectral radius: the
rho_infinity-Bathe
method

Development and Performance Evaluation of Wireless Optical Position Tracking System

Finite Element Analysis of Wrist Orthosis with 3D printing

Change in density of peri-implant bone due to bone remodeling according to implant structure and initial conditions

Which plate results in better stability after segmental mandibular resection and fibula free flap reconstruction? : Biomechanical analysis

Biomechanical effect of a mandibular advancement device with different protrusion positions for the treatment of obstructive sleep apnea on the tooth and facial bones: A finite element study

Effects of moderate intensity static magnetic fields on osteoclastic differentiation in mouse bone marrow cells

Experimental evaluation of particle separation efficiency for dielectrophoretic flows passing through a microfluidic device

Further insights into an implicit time integration scheme for structural dynamics

Design of a mandibular advancement device for patients with partial dentures

Enhanced markerless surgical robotic guidance system for keyhole neurosurgery

On the stability of the permanently bent mini-plate in reconstructive surgery

Anisotropic patterning to reduce instability of concentric-tube robots

An explicit time integration scheme for the analysis of wave propagations

Performance of an implicit time integration scheme in the analysis of wave propagations

Insight into an implicit time integration scheme for structural dynamics

경두개 집속초음파 음압장 예측 장치, 경두개 집속초음파 음압장 예측 프로그램 및 음압장 생성 인공지능 구현 방법

초음파 변환기 위치 설정 장치, 초음파 변환기 위치 설정 프로그램 및 초음파 변환기 위치 설정 인공지능 구현 방법

척추 케이지

척추뼈 침강 방지를 위한 2중 구조의 3D 프린팅 척추케이지 임플란트

환자 맞춤형 수술용 가이드 디자인 스프트웨어

The Bathe time integration method with controllable spectral radius: The ρ∞-Bathe method

Biomechanical effects of dental implant diameter, connection type, and bone density on microgap formation and fatigue failure: A finite element analysis

For direct time integrations: A comparison of the Newmark and ρ∞-Bathe schemes

Effects of implant diameter, implant-abutment connection type, and bone density on the biomechanical stability of implant components and bone: A finite element analysis study

Which plate results in better stability after segmental mandibular resection and fibula free flap reconstruction? Biomechanical analysis

Biomechanical effect of mandibular advancement device with different protrusion positions for treatment of obstructive sleep apnoea on tooth and facial bone: A finite element study

Effects of assessing the bone remodeling process in biomechanical finite element stability evaluations of dental implants

Deep neural network for navigation of a single-element transducer during transcranial focused ultrasound therapy: proof of concept

Selecting the load at the intermediate time point of the ρ∞-Bathe time integration scheme

Time splitting ratio in the ρ∞-Bathe time integration method for higher-order accuracy in structural dynamics and heat transfer

Gunwoo Noh

In Refs. [1,2], an effective implicit time integration scheme was proposed for the finite element solution of nonlinear problems in structural dynamics. Various important attributes were demonstrated. In particular, it was shown that the scheme remains stable, without the use of adjustable parameters, when the commonly used trapezoidal rule results in unstable solutions. In this paper we focus on additional important attributes of the scheme, and specifically on showing that the procedure can also be effective in linear analyses. We give, in comparison to other methods, the spectral radius, period elongation, and amplitude decay of the scheme and study the solution of a simple ‘model problem’ with a very flexible and stiff response.

A new explicit time integration scheme is presented for the solution of wave propagation problems. The method is designed to have small solution errors in the frequency range that can spatially be represented and to cut out high spurious frequencies. The proposed explicit scheme is second-order accurate for systems with and without damping, even when used with a non-diagonal damping matrix. The stability, accuracy and numerical dispersion are analyzed, and solutions to problems are given that illustrate the performance of the scheme.

We consider the Bathe implicit time integration method and focus on the time step splitting ratio and the spectral radius at large time steps to improve and generalize the scheme. The objective is to be able to prescribe the amplitude decay (dissipation) and period elongation (dispersion) for the numerical integration, and to achieve this aim in a direct and optimum manner with the minimum number of parameters. We show that the use of the time step splitting ratio and spectral radius is effective to prescribe in a smooth manner no amplitude decay to very large amplitude decays, with correspondingly small period elongation to very large period elongations while maintaining second-order accuracy. We analyze the effects of the splitting ratio and spectral radius on the stability and accuracy of the scheme and illustrate the use of these parameters in comparison with previously published methods. Furthermore, we show …

In earlier work an effective implicit time integration scheme was proposed for the finite element solution of nonlinear dynamic problems [1,2]. The method, referred to as the Bathe method, was shown to possess unusual stability and accuracy characteristics for the solution of problems in linear and nonlinear structural dynamics [1–3]. In this paper we study the dispersion properties of the method, in comparison to those of the widely used Newmark trapezoidal rule, and show that the desired characteristics of the Bathe method for structural dynamics are also seen, and are very important, in the solution of wave propagation problems. A dispersion analysis is given and problems are solved to illustrate the capabilities of the scheme for the solution of wave propagation problems.

Background and Objective Understanding fatigue failure and microgap formation in dental implants, abutments, and screws under various clinical circumstances is clinically meaningful. In this study, these aspects were evaluated based on implant diameter, connection type, and bone density. Methods Twelve three-dimensional finite element models were constructed by combining two bone densities (low and high), two connection types (bone and tissue levels), and three implant diameters (3.5, 4.0, and 4.5 mm). Each model was composed of cortical and cancellous bone tissues, the nerve canal, and the implant complex. After the screw was preloaded, vertical (100 N) and oblique (200 N) loadings were applied. The relative displacements at the interfaces between implant, abutment, and screw were analyzed. The fatigue lives of the titanium alloy (Ti–6Al–4V) components were calculated through repetitive …

As a steerable needle or robotic manipulator, the concentric-tube robot shows good potential for use in minimally invasive medical procedures. However, the torsional deformation of the precurved tubes comes at the price of instability, which not only limits the workspace and tool path but also potentially creates danger of tissue rupture when external load is applied. In this paper, we propose anisotropic patterning of tubes to solve the instability problem. Hole-patterning can tune the mechanical properties of the tubes so that the ratio of the torsional rigidity to the bending rigidity becomes higher. This study investigates the effect of pattern design parameters by building a lumped analytical model and examining it with finite-element analysis. The pattern is engraved via laser machining and we experimentally verify that material anisotropy reduces instability.

The objective in this paper is to present some new insights into an implicit direct time integration scheme, the Bathe method, for the solution of the finite element equations of structural dynamics. The insights pertain to the use of the parameters in the method, and in particular the value of the time step splitting ratio. We show that with appropriate values of this ratio large amplitude decays can be obtained as may be desirable in some solutions. We give the theoretical analysis of the method for the parameters used, including for very large time steps, and illustrate numerically the new insights gained.

We consider the unconditionally stable Newmark and ρ∞-Bathe methods for the direct time integration of the finite element equations in structural dynamics and wave propagations. In our evaluation of the Newmark method we consider the parameters δ and α, and in the ρ∞-Bathe method we consider the parameters γ and ρ∞, with 0< γ<∞, γ≠ 1 and ρ∞∈[-1,+ 1]. We show that the Newmark method as usually used with its δ and α parameters, α= 0.25 (δ+ 0.5) 2 and δ⩾ 0.5, is a special case of the ρ∞-Bathe method. We also show that the β 1/β 2-Bathe method is a special case of the ρ∞-Bathe scheme. The study of the curves of numerical dissipation and dispersion shows that the ρ∞-Bathe method provides effective dissipation and dispersion whereas the Newmark method lacks in that regard. To illustrate our theoretical findings we give the results of some example solutions of structural dynamics and wave …

Statement of problem Short implants have been increasingly used in the aging society. However, studies which explain the difference of stress distribution according to different connections in short implant treatment are scarce. Purpose The purpose of this finite element (FE) analysis was to evaluate the stress and strain distribution of short implants and surrounding bone under static and cyclic loading conditions with 4 different connections. Material and methods Three-dimensional models of 4 types of implant systems were considered: internal tissue level, internal tissue level wide, internal bone level (IB), and external bone level. Each system had different types of abutment, implant, and screw with the resorbed mandibular segment of the bone block. Static FE analysis was performed under external loads of 200 N (vertical or 30-degree oblique) to each cusp tip. The strain distributions of the peri-implant bone and von …

The objective of this paper is to investigate the optimal use of some time integration schemes for the solution of transient wave propagation problems. We study the accuracy characteristics of the trapezoidal rule and the ρ∞-Bathe scheme considering various parameter sets (ρ∞, γ, CFL) with both consistent and lumped mass matrices. The ρ∞-Bathe scheme includes also the standard-, β 1/β 2-Bathe methods, the Newmark method and the trapezoidal rule. The study of the numerical dispersion shows that in the case of the consistent mass matrix, the ρ∞-Bathe scheme with a proper setting of (ρ∞, γ) and standard Bathe scheme provide similar dispersion errors and outperform the trapezoidal rule. The optimal CFL number of the ρ∞-Bathe scheme is about 25% larger than for the standard Bathe scheme. In addition, we show that using a lumped mass matrix and proper values of ρ∞< 0, γ and CFL in the ρ∞-Bathe …

Statement of problem Various kinds of implants of different diameters and connection types are used for patients with a range of bone densities and tooth sizes. However, comprehensive studies simultaneously analyzing the biomechanical effects of different diameters, connection types, and bone densities are scarce. Purpose The purpose of this 3-dimensional finite element analysis study was to evaluate the stress and strain distribution on implants, abutments, and surrounding bones depending on different diameters, connection types, and bone densities. Material and methods Twelve 3-dimensional models of the implant, restoration, and surrounding bone were simulated in the mandibular first molar region, including 2 bone densities (low, high), 2 implant-abutment connection types (internal tissue level, internal bone level), and 3 implant diameters (3.5 mm, 4.0 mm, and 4.5 mm). The occlusal force was 200 N …

Objective This study investigated the biomechanical stability of 2 plate systems—mini-plates and reconstruction plates—in reconstruction with fibular free flaps. Study Design The reconstruction models were constructed by using 2 types of plates in representative cases with segmental mandibular defect (C, L, LC1, LC2). In each model, a masticatory simulation approximating 3 clenching tasks was conducted, using the muscle forces adjusted to the mandible structure used in this study. In addition, to evaluate the sensitivity of the 2 plate systems for masticatory load changes, a sensitivity analysis was also performed by using finite element analysis. Results The risks of plate fracture and screw loosening measured by stress concentrations were higher in the cases using mini-plates compared with those using reconstruction plates. Moreover, the mini-plate was more sensitive to varied loads compared with the …

Background The mandibular advancement device (MAD) is widely used for obstructive sleep apnoea (OSA) treatment, and several studies have demonstrated its effectiveness. However, no comprehensive studies have yet examined the biomechanical safety of the MAD. Objectives The objective of this study was to analyse the biomechanical effect of different protrusion positions of a MAD on the teeth and facial bones. Methods The posterior restorative forces due to the stretched mandibular muscles were measured by pressure sensors attached to the experimental mandibular advancement device for mandibular protrusions of 10‐70% of the maximum protrusion of the subject. A detailed three‐dimensional biomechanical model of the study subject, constructed from computed tomography scans, was used in finite element analysis, with loading conditions calculated from the measured posterior restorative forces …

Background and objective While an accurate assessment of the biomechanical stability of implants is essential in dental prosthesis planning and associated treatment assurance, the bone remodeling process is often ignored in biomechanical studies using finite element (FE) analysis. In this study, we aimed to analyze the significance of assessing the bone remodeling process in FE analysis for evaluating the biomechanical stability of dental implants. We compared the FE results considering the bone remodeling process with FE results simulated using commonly used conditions, with no considerations of the bone remodeling process. Methods The mathematical model proposed by Komarova et al. was used to calculate cell population dynamics and changes in bone density at a discrete site. The model was implemented in the FE software ABAQUS, using the UMAT subroutine. Three-dimensional FE models were …

Transcranial focused ultrasound (tFUS) has gained attention in the field of brain stimulation owing to its non-invasive neurotherapeutic potentials. However, complex interactions between acoustic waves and the cranium may introduce misalignment of the acoustic focus from a geometric target location, thus, necessitate on-site feedback of real-time navigational information of the transducer (spatial coordinates and angular orientation) for the operators to accurately place the acoustic focus to the desired brain area. In this study, we propose a deep-learning-based network model that can provide spatial navigational information of a single-element FUS transducer with respect to the targeted brain region. The training dataset were acquired through forward simulations that reflect the different tFUS transmissions for each skull structure using cranial computed tomography (CT) image data. The performance of the network …

The objective of this paper is to identify the optimal load selection at the intermediate time point of the ρ ∞ -Bathe time integration method. We study the truncation errors of the scheme in homogeneous and forced responses for various parameters. The optimal load at the sub-step is determined by minimizing the global truncation errors of forced responses. A numerical impulse analysis shows that the optimal load at the sub-step thus established actually corresponds to numerical impulses at the three- and four-point Newton-Cotes formulas for the second- and third-order accuracy cases, respectively. We illustrate the findings of our theoretical study in example solutions of two-dimensional structural dynamics and wave propagation problems. With the optimally selected load at the sub-step, more accurate solutions can be obtained in some analyses.

Our objective in this paper is to investigate the use of the splitting ratio, γ, in the ρ∞-Bathe method to reach a higher-order accuracy in the finite element solutions of structural dynamics and heat transfer problems. We study the order of accuracy of the method for both types of analyses, and identify a real-valued γ p resulting into third-order accuracy with ρ∞=(-1, 1-3] and a complex-valued γ i with ρ∞∈[0, 1] providing at least third-order accuracy but γ i with ρ∞= 1 gives fourth-order accuracy. In both types of analyses, structural and heat transfer solutions, the γ values result into the same orders of convergence. To illustrate our theoretical findings, we give the results of some example solutions of structural dynamics and heat flow problems. These solutions show that more accurate response predictions can be obtained when using the more effective γ values.

Variable stiffness mechanisms have become popular for improving the performance of meso/microscale robots due to their ability to enable safe, effective, and versatile operation without additional actuators. In minimally invasive surgery (MIS), they can provide low stiffness for adaptability and an extended workspace and high stiffness for stable manipulation. This study aims to optimize the pattern design that maximizes the stiffness ratio while preventing buckling. Longitudinal slits are identified as the ideal shape for maximizing the ratio using topology optimization. The effects of the design parameters are investigated by analytical modeling and finite-element analysis (FEA). Finally, we established a design optimization process to maximize the variable stiffness ratio while ensuring safety. The load and buckling tests of 19 cases are verified in both the experiment and FEA. Buckling occurred in eight cases …

Although we recently demonstrated that static magnetic fields (SMFs) of 3, 15, and 50 mT stimulate osteoblastic differentiation, the effects of SMFs on osteoclastogenesis are still poorly understood. This study focused on the suppressive effects of SMFs on receptor activator of nuclear factor κB ligand (RANKL)‐induced osteoclastogenesis and bone resorption. Direct SMFs inhibit RANKL‐induced multinucleated osteoclast formation, tartrate‐resistant acid phosphatase activity, and bone resorption in mouse bone marrow‐derived macrophage cells. The conditioned medium from osteoblasts treated with SMFs also resulted in the inhibition of osteoclast differentiation as well as resorption. The RANKL‐induced expression of osteoclast‐specific transcription factors, such as c‐Fos and NFATc1, was remarkably downregulated by SMF at 15 mT. In addition, SMF inhibited RANKL‐activated Akt, glycogen synthase kinase …

PURPOSE A novel retentive type of implant prosthesis that does not require the use of cement or screw holes has been introduced; however, there are few reports examining the biomechanical aspects of this novel implant. This study aimed to evaluate the biomechanical features of cementless fixation (CLF) implant prostheses. MATERIALS AND METHODS The test groups of three variations of CLF implant prostheses and a control group of conventional cement-retained (CR) prosthesis were designed three-dimensionally for finite element analysis. The test groups were divided according to the abutment shape and the relining strategy on the inner surface of the implant crown as follows; resin-air hole-full (RAF), resin-air hole (RA), and resin-no air hole (RNA). The von Mises stress and principal stress were used to evaluate the stress values and distributions of the implant components. Contact open values were calculated to analyze the gap formation of the contact surfaces at the abutment-resin and abutment-implant interfaces. The micro-strain values were evaluated for the surrounding bone. RESULTS Values reflecting the maximum stress on the abutment were as follows (in MPa): RAF, 25.6; RA, 23.4; RNA, 20.0; and CR, 15.8. The value of gap formation was measured from 0.88 to 1.19 µm at the abutmentresin interface and 24.4 to 24.7 µm at the abutment-implant interface. The strain distribution was similar in all cases. CONCLUSION CLF had no disadvantages in terms of the biomechanical features compared with conventional CR implant prosthesis and could be successfully applied for implant prosthesis.

Computational Mechanics & Design Optimization Lab

교수님 소개

노건우

연구실 소개

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

Graph Attention Network-Based Surrogate Model for Acceleration and Generalization of Injection Molding Simulations

Effect of chip-induced powder size distribution on 18Ni maraging steel in hybrid addictive manufacturing

Implicit s-sub-step time integration schemes with (s+1)th-order accuracy and dissipation control

연구실 보유 특허

대학별 입시끈

우리 연구실 모집

교수님 소개

노건우

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

Graph Attention Network-Based Surrogate Model for Acceleration and Generalization of Injection Molding Simulations

Effect of chip-induced powder size distribution on 18Ni maraging steel in hybrid addictive manufacturing

Implicit s-sub-step time integration schemes with (s+1)th-order accuracy and dissipation control

연구실 보유 특허

최근 3년간 연구실적 높은 연구실

대학별 입시끈

우리 연구실 모집