Topoloji Optimizasyonunda Eleman Silme Metodunun Uygulanmasi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Makine parçalarında en iyi malzeme dağılımını sağlayabilmek için çeşitli optimizasyon yöntemleri geliştirilmiştir. Bu yöntemlerden birisi de topoloji optimizasyonudur. Topoloji optimizasyonunda en önemli sorun, çözüm için gereken uzun süredir. Bu çalışmada topoloji optimizasyonunda eleman silme metodu irdelenmiş ve metodun, topoloji optimizasyonunda uzun çözüm süresi için bir çıkış yolu olabileceği gösterilmiştir.To obtain the best material distribution in machine parts, some optimization techniques are developed by many researchers. Among these techniques topology optimization algorithms are discussed. These algorithms are useful for determining initial possible shape of structures. An important drawback of the topology optimization is time consumption. In this study, element deletion during topology optimization is discussed and it is shown that the method may be a solution to time consumption problem of topology optimization

Hybrid seven-bar press mechanism: link optimization and kinetostatic analysis

An optimization study with kinetostatic analysis is performed on hybrid seven-bar press mechanism. This study is based on previous studies performed on planar hybrid seven-bar linkage. Dimensional synthesis is performed, and optimum link lengths for the mechanism are found. Optimization study is performed by using genetic algorithm (GA). Genetic Algorithm Toolbox is used with Optimization Toolbox in MATLAB®. The design variables and the constraints are used during design optimization. The objective function is determined and eight precision points are used. A seven-bar linkage system with two degrees of freedom is chosen as an example. Metal stamping operation with a dwell is taken as the case study. Having completed optimization, the kinetostatic analysis is performed. All forces on the links and the crank torques are calculated on the hybrid system with the optimized link lengths

Design of a robot-assisted exoskeleton for passive wrist and forearm rehabilitation

This paper presents a new exoskeleton design for wrist and forearm rehabilitation. The contribution of this study is to offer a methodology which shows how to adapt a serial manipulator that reduces the number of actuators used on exoskeleton design for the rehabilitation. The system offered is a combination of end-effector- and exoskeleton-based devices. The passive exoskeleton is attached to the end effector of the manipulator, which provides motion for the purpose of rehabilitation process. The Denso VP 6-Axis Articulated Robot is used to control motion of the exoskeleton during the rehabilitation process. The exoskeleton is designed to be used for both wrist and forearm motions. The desired moving capabilities of the exoskeleton are flexion–extension (FE) and adduction–abduction (AA) motions for the wrist and pronation–supination (PS) motion for the forearm. The anatomical structure of a human limb is taken as a constraint during the design. The joints on the exoskeleton can be locked or unlocked manually in order to restrict or enable the movements. The parts of the exoskeleton include mechanical stoppers to prevent the excessive motion. One passive degree of freedom (DOF) is added in order to prevent misalignment problems between the axes of FE and AA motions. Kinematic feedback of the experiments is performed by using a wireless motion tracker assembled on the exoskeleton. The results proved that motion transmission from robot to exoskeleton is satisfactorily achieved. Instead of different exoskeletons in which each axis is driven and controlled separately, one serial robot with adaptable passive exoskeletons is adequate to facilitate rehabilitation exercises.</p

A hybrid press system: Motion design and inverse kinematics issues

A hybrid machine (HM) is a system integrating two types of motor, servo and constant velocity with a mechanism. The purpose is to make use of the energy in the system efficiently with a flexible system having more than one degree of freedom (DOF). A review is included on hybrid press systems. This study is included as a part of an industrial project used for metal forming. The system given here includes a 7 link mechanism, one of link is driven by a constant velocity motor (CV) and the other is driven by a servo motor (SM). Kinematics analysis of the hybrid driven mechanism is presented here as inverse kinematics analysis. Motion design is very crucial step when using a hybrid machine. So motion design procedure is given with motion curve examples needed. Curve Fitting Toolbox (CFT) in Matlab® is offered as an auxiliary method which can be successfully applied. Motion characteristics are chosen by looking at requirements taken from metal forming industry. Results are then presented herein

A new species of Tephritis from Turkey, with a key to the species of the Tephritis pulchra group

Tephritis merzi n. sp., reared from flowerhead galls on Scorzonera kotschyi Boiss., is described from Turkey and placed in the T. pulchra species group. The T. pulchra group is redefined and a key to the seven included species is provided. The best characters for defining the group are the preapical step in the female aculeus and the taxonomic affiliation of the host plants, all in Scorzonera and Tragopogon. All species appear to induce galls, either in the flower heads, or in the upper or lower stem, depending on the species. The galls are unilocular, although several individuals usually develop in them

A Finite Element Removal Method for 3D Topology Optimization

Topology optimization provides great convenience to designers during the designing stage in many industrial applications. With this method, designers can obtain a rough model of any part at the beginning of a designing stage by defining loading and boundary conditions. At the same time the optimization can be used for the modification of a product which is being used. Lengthy solution time is a disadvantage of this method. Therefore, the method cannot be widespread. In order to eliminate this disadvantage, an element removal algorithm has been developed for topology optimization. In this study, the element removal algorithm is applied on 3-dimensional parts, and the results are compared with the ones available in the related literature. In addition, the effects of the method on solution times are investigated

Çalışma Yükleri Altında Ekskavatör Ön Ataşmanın Analizi ve Optimizasyonu

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015İş makinesinin mekanizması tüm çalışma koşullarında güvenilir bir şekilde çalışmalıdır. Yüksek yüklerin etkisi altında mukavemet analizi, iş makinelerinin tasarım aşamasında oldukça önemli bir adımdır. [1] Bu çalışma, kazıcı iş makinesinin, bom ve kol tasarımında, çalışma kuvvetlerine bağlı olarak oluşan gerilmelerin incelenmesi ve parçaların iyileştirilmesi üzerinedir. Amaç, ürünün maruz kaldığı kuvvetlere bağlı olarak istenilen sınır gerilme değerinin (kullanılan malzeme cinsine göre sınır değeri 150 MPa kabul edilmiştir) altında kalmasının sağlanmasının yanı sıra, ürünün bu yükleri optimum malzeme kullanımı ile karşılamasının sağlanmasıdır. Kuvvet analizi tamamlandıktan sonra ön ataşman, makinenin kritik [2] konumuna göre simule edilmiştir ve modellenmiştir. Bu mühendislik problemine sayısal bir çözüm yöntemi olarak Sonlu Elemanlar Yöntemi (SEY) uygulanmıştır. Bu şekilde hedeflenen diğer bir amaç, tasarım ve imalat sürecindeki zamanı kısaltmak ve son kullanıcıya daha uzun ömürlü ve güvenilir bir ürün verebilmektir.Construction machines mechanisms must run safely under even worst conditions. Stress analyzes of the machines under high load values is an important step for design of these machines [1]. Present paper is aimed to analyzes and optimization of boom and arm of an excavator under working conditions. During design stage it is observed that stress values on each part of beam and arm is under allowed value (changing according to used material but generally allowed valu is 150 MPa) material optimization also performed meanwhile. After force analyzes of the front attachment the parts are modeled and analyzed for critical position [2]. Finite element analyzes is applied as a numerical method. Use of this method is shortening the time consumed for design and analyzes and also more reliable and long life products are offered to end users

Experimental Finite Element Approach for Stress Analysis

This study aims to determining the strain gauge location points in the problems of stress concentration, and it includes both experimental and numerical results. Strain gauges were proposed to be positioned to corresponding locations on beam and blocks to related node of elements of finite element models. Linear and nonlinear cases were studied. Cantilever beam problem was selected as the linear case to approve the approach and conforming contact problem was selected as the nonlinear case. An identical mesh structure was prepared for the finite element and the experimental models. The finite element analysis was carried out with ANSYS. It was shown that the results of the experimental and the numerical studies were in good agreement

A hybrid press system: Motion design and inverse kinematics issues

A hybrid machine (HM) is a system integrating two types of motor; servo and constant velocity with a mechanism. The purpose is to make use of the energy in the system efficiently with a flexible system having more than one degree of freedom (DOF). A review is included on hybrid press systems. This study is included as a part of an industrial project used for metal forming. The system given here includes a 7 link mechanism, one of link is driven by a constant velocity motor (CV) and the other is driven by a servo motor (SM). Kinematics analysis of the hybrid driven mechanism is presented here as inverse kinematics analysis. Motion design is very crucial step when using a hybrid machine. So motion design procedure is given with motion curve examples needed. Curve Fitting Toolbox (CFT) in Matlab® is offered as an auxiliary method which can be successfully applied. Motion characteristics are chosen by looking at requirements taken from metal forming industry. Results are then presented herein