New Elastoplastic Analysis of Two-Dimensional Frames When Some Plastic Hinges Unload Elastically

Fethullah Uslu,Mehmet Tevfik Bayer,Mustafa Haluk Saraçoğlu 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.2

Two-dimensional frames are made of elastic and perfectly plastic materials. Frames are analized by using the step by step elastoplastic analysis method where the applied loads are gradually increased at each step until a plastic hinge is developed. Then an equivalent frame model is generated by placing a mechanical hinge at the location of the plastic hinge and the increased external loads and the reduced plastic moments acting at the plastic hinge sections are applied to this model and elastoplastic analysis is performed. This elastoplastic analysis is repeated by incrementally increasing the external loads and applying the new reduced plastic moments, until the next plastic hinge is developed. Then a new equivalent frame model is generated to search for the following plastic hinge. This step by step elastoplastic analysis continues until the frame partially or totally collapses. When a plastic hinge is developed, it means that the section is at a fully plastic stress state. In the following small load increment: if this fully plastic stress state moves to another fully plastic stress state then this movement is called plastic fl ow. But if this fully plastic stress state moves to an elastic–plastic stress state then this movement is called elastic unloading. During the search of the next plastic hinge if one of the plastic hinges begins to unload elastically then the current equivalent frame model must be revised. For this the frame member which contains the elastically unloading plastic hinge is replaced by the equivalent frame member carrying balancing loads.

Analysis on Elliptic and Parabolic 2-DOF Flexure Hinges for Spatial Positioning Stages

신현표(Hyun-Pyo Shin),문준희(Jun-Hee Moon) Korean Society for Precision Engineering 2023 한국정밀공학회지 Vol.40 No.3

With advancements in semiconductor manufacturing processes and the development of precision processing technology, flexure hinge-based ultra-precision positioning stages are widely used. In the flexure hinge, axial and bending stiffness properties greatly influence positioning performance. This study examined the stiffness properties of elliptic and parabolic 2-degrees-of-freedom (DOF) hinges, which have not been extensively discussed. The Timoshenko beam theory was applied to derive the stiffness equations for the axial and bending directions of each hinge. The stiffness properties were examined in several design conditions by comparing theoretical and finite element analyses. Based on the results of the analyses, an empirical formula in exponential form for the design of an elliptic hinge was constructed through surface-fitting. The elliptic hinge was found to be a better alternative to a circular hinge under certain design conditions by adjusting two design parameters. In the future, we will develop sophisticatedly designed hinges with improved axial and bending stiffness properties compared to the existing circular and elliptic hinges.

Study on the Mechanical Behavior of Composite Special-Shaped Columns under Compression-Bending Without End Rotation Constraints

Jian Zhang,Hongjun Wang,Ting Zhou,Zixuan Wang,Zhihua Chen 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.1

In this study, three double-plate connected L-shaped concrete-filled steel tube composite (LCFST-D) columns were subjected to axial and eccentric loading tests using spherical-hinge supports to relieve the bidirectional rotation constraints. By analyzing the failure phenomenon of the LCFST-D specimen, the rotation of the endplate, and the comparison of similarities and differences between the support of the knife-edge and the support of the spherical-hinge, the bidirectional eccentric loading performance of the LCFST-D column when the bidirectional rotation constraint was released was studied. The test results show that when the spherical-hinge support was loaded, the out-of-the-plane deflection was more evident than the knife hinge. The bearing capacity of the LCFST-D specimen decreases as the eccentricity increased. When the end rotation constraints were relieved, the failure mode of the axial and eccentric loading was nontorsional bidirectional instability. In addition, the loading tests using spherical-hinge supports were verified to effectively release end rotation constraints. A finite element model for the LCFST-D column was established, and its accuracy was confirmed. From the failure mode, deflection, bearing capacity, and rotation of the endplate, the differences between spherical-hinge, knife-edge hinge, and rigid pad loading supports and their influence on bidirectional eccentric loading tests performed on special-shaped columns were investigated. The results show that the bidirectional eccentric loading performance of the LCFST-D column can be reflected by spherical-hinge supports. The theoretical formula was used simultaneously to verify the data from the finite element model and the test.

Min-Max 알고리즘을 이용한 피에조 구동형 스테이지의 최적설계 및 성능평가

최기봉(Kee-Bong Choi),한창수(Chang Soo Han) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.9

This paper presents an optimal design and the performance evaluation of two-axis nano positioning stage with round notched flexure hinges. A flexure hinge mechanism with round notched flexure hinges is to guide the linear motions of a moving plate in the nano positioning stage. A Min-Max algorithm is applied to the design of the flexure hinge mechanism for nano positioning stage. In the design process, the structure of the flexure hinge mechanism is fixed, then the radius of a round hole and the width of two round holes are chosen as design variables, and finally the design variables are calculated by the Min-Max algorithm. The machined flexure hinge mechanism, stack type PZTs for actuation and capacitance type displacement sensors for position measurement are assembled into the nano positioning stage. The experimental results of the manufactured nano positioning stage show the first modal resonance frequency of 197 ㎐, the operating range of 40 ㎛, and the resolution of 3 ㎚.

다구찌 방법을 활용한 Rear Center-Hinge Bracket 강건 설계

정세빈(Sebin Jung),김민호(Minho Kim) 한국자동차공학회 2014 한국 자동차공학회논문집 Vol.22 No.3

The rear center-hinge bracket is designed for supporting and folding the rear-seat backrest. This bracket needs to be strong enough to be able to rigidly hold the rear-seat backrest and to withstand luggage loads from the car trunk that are generated when a vehicle is driving on the roads. Particularly, current accident studies report that many serious occupant injuries occurred when the rear-seat back easily folded inward toward the car interior, driven by the luggage loads in the trunk. Given this fact, the robust design of the rear center-hinge bracket that mainly supports the rear backrest has become more important for providing customer safety and preventing high warranty and durability problems. However, none of the studies have emphasized its significant role and considered its robust optimization. Therefore, this paper presents how the hinge-bracket design is optimized based on an application of the finite-element method coupled with the parameter design using Taguchi’s design experiment. Finally, Taguchi method’s application optimizes a robust center-hinge bracket that shows more rigid performance although it has lighter weight and thinner thickness.

An optimization approach for black-and-white and hinge-removal topology designs

Yongqing Fu,Xianmin Zhang 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2

An optimization approach for black-and-white and hinge-removal topology designs is studied. To achieve this motive, an optimal topologyallowing grey boundaries is found firstly. When a suitable design has been obtained, this solution is then used as a starting pointfor the follow-up optimization with the goal to free unfavorable intermediate elements. For this purpose, an updated optimality criterionin which a threshold factor is introduced to gradually suppress elements with low density is proposed. The typical optimality method andnew technique proposed are applied to the design procedure sequentially. Besides, to circumvent the one-point hinge connection problemproducing in the process of freeing intermediate elements, a hinge-removal strategy is also proposed. During the optimization, the binaryconstraints on design variables are relaxed based on the scheme of solid isotropic material with penalization. Meanwhile, the meshindependencyfilter is employed to ensure the existence of a solution and remove well-known checkerboards. In this way, a solution thathas few intermediate elements and is free of one-point hinge connections is obtained. Finally, different numerical examples including thecompliance minimization, compliant mechanisms and vibration problems demonstrate the validity of the proposed approach.

압전소자와 변위 확대 기구를 이용한 마이크로 펀칭 시스템 개발

최종필(Jong Pil Choi),이광호(Kwang Ho Lee),이혜진(Hye Jin Lee),이낙규(Nak Gyu Lee),김병희(Byeong Hee Kim) 한국생산제조학회 2007 한국생산제조시스템학회 학술발표대회 논문집 Vol.2007 No.5

This paper presents the design of micro punching system using PZT actuator and displacement amplification device. The micro punching system consists of precision guide and PZT module. A precision guide module includes the ball guided LM and micro step. motor with 30㎜ stroke and 0.5 ㎛ resolution. A PZT module consists of PZT and displacement amplification device with flexure hinge mechanism. The flexure hinge consists of two levers and leaf type spring mechanisms in three-dimensional structure. The flexure hinge module consists of three flexure hinge. Therefore, it can be improved the mechanical stiffness, frequency response, and characteristic of assemble by symmetric structure with the circular pattern. The detailed design of the flexure hinge was performed using finite element analysis. Its output displacement can produce about 5 times larger than input displacement.

압전소자와 변위 확대 기구를 이용한 마이크로 펀칭 시스템 개발

최종필(Jong Pil Choi),이광호(Kwang Ho Lee),이혜진(Hye Jin Lee),이낙규(Nak Gyu Lee),김병희(Byeong Hee Kim) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-

This paper presents the design of micro punching system using PZT actuator and displacement amplification device. The micro punching system consists of precision guide and PZT module. A precision guide module includes the ball guided LM and micro step. motor with 30㎜ stroke and 0.5 ㎛ resolution. A PZT module consists of PZT and displacement amplification device with flexure hinge mechanism. The flexure hinge consists of two levers and leaf type spring mechanisms in three-dimensional structure. The flexure hinge module consists of three flexure hinge. Therefore, it can be improved the mechanical stiffness, frequency response, and characteristic of assemble by symmetric structure with the circular pattern. The detailed design of the flexure hinge was performed using finite element analysis. Its output displacement can produce about 5 times larger than input displacement.

도어용 한 방향 회전 댐퍼 개발 및 성능실험

김기환(Gi-hwan Kim),박창순(Chang-soon Park),이응석(Eung-suk Lee) 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.5

The quality door hinge has various functions for smooth opening and slow closing . Some commercial and expensive hinges have adjusting methods of the time to close and the power to open . To achieve this purpose, damper and spring units are combined dynamically and structural design is required. We designed a single-way rotary damper and spring door hinge system. A testing device for acquiring performance data, such as closing time and damping/spring force during door opening and closing, is required for the standardization of commercial door hinges. Single-way rotary dampers include a check valve with a hole in the vane assembled on the rotating shaft. The experimental result showed that the damping forces in the opening and closing directions are low and high, respectively. The damping coefficient was obtained for performance verification purposes.

비전을 이용한 자동차 Support Hinge의 너트용접 검사 시스템 개발

김성민(Seong-Min Kim),이영춘(Young-Choon Lee),이성철(Seong-Cheol Lee) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월

This paper is about the development of automatic inspection system of welded nuts on Support hinge using machine vision for the improvement of working condition. Until now, projection welding process was performed by operator. Also, inspection of welded nuts is performed manually and recorded by the operator’s naked eye. So these processes caused the produce of poorly-made articles. To improve this manual operation, inspection system using machine vision is introduced. Test algorithm, lighting system and program showed good results to the designed inspection system and led to the increment of productivity.