Bending crashworthiness of thin-walled square tubes with multi-cell and double-tube cross-sections

Z. Y. Xie,Z. X. Zhao,C. Li 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.11

For structural bending crashworthiness, previous studies mostly focused on thin-walled tubes with multi-cell cross-sections, while the double-tube configuration was seldom studied. In this paper, the bending crashworthiness of thin-walled tubes with multi-cell and double-tube configurations was compared based on three-point bending tests conducted using the ABAQUS/Explicit code. The numerical results reveal that the reinforcements significantly improve the bending crashworthiness beyond the conventional empty tube according to the two indicators: specific energy absorption (SEA) and crash load efficiency (CLE). For the ratio of cross-sectional width to wall thickness b/t = 100, the double-tube configuration has a similar bending crashworthiness performance to the multi-cell configuration. The asymmetric multi-cell configurations are found to demonstrate more excellent SEA performance than their symmetric counterparts in most cases. For the case b/t = 50, the double-tube configuration significantly prevails over the multi-cell configuration.

실시간 스프링백 예측을 통한 보의 3점굽힘 적응제어기 설계

김승철,정성종 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.3

In order to automate straightening process of deflected beams, an adaptive three-point bending controller is studied, which estimates and controls springback of beams under three-point bending. An analytical load-deflection model for three-point bending of beams with circular cross sections is derived nondimensionally. In spite of variations of material and process parameters, this model can be applied to springback estimation by measuring real-time values of reactive load and deflection of the beam. A hydraulic punch stroke controller is designed to take real-time controls of the permanent deflection of the beam. The validity of the proposed system is verified through experiments.

A virtual experimental approach to evaluate transverse damage behavior of a unidirectional composite considering noncircular fiber cross-sections

Jeong, Gyu,Lim, Jae Hyuk,Choi, Chunghyeon,Kim, Sun-Won Elsevier 2019 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.228 No.-

<P><B>Abstract</B></P> <P>This study investigated the transverse damage behavior of a unidirectional composite containing a complex microstructure having noncircular fiber cross-sections. For this purpose, a finite-element (FE) model based real microscopic images of the M55J/M18 composite was generated with the signed distance function (SDF) by the level-set method and the trimming mesh technique. In addition, the interphase zone was constructed along the interface between the fiber and the matrix. Subsequently, a virtual experiment simulating a three-point bending test was conducted with the generated FE model. Crack propagation analysis was carried out with the cohesive zone model (CZM) by applying transverse tension under plane strain condition. The crack length and propagation directions were compared to those of the three-point bending test. To make a nice correlation between the virtual experiment and actual experiment, the effects of the fiber shape, thermal residual stress, and various fracture toughnesses were investigated on the length and propagation direction of the cracks. It was found that, the fiber shape is vital to the inter-fiber distance and fiber volume fraction (<I>V</I> <SUB>f</SUB>), which strengthen or weaken the stress concentration, thus making the propagation direction of the cracks warped and the length of cracks varied.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A complex microstructure is modelled by the trimming mesh and the level set method. </LI> <LI> The proposed scheme can handle convex and concave shape of fibers accurately. </LI> <LI> A virtual three-point bending simulation propagates cracks in a complex microstructure. </LI> <LI> The crack propagation simulation show excellent agreement with the test results according to the applied displacement. </LI> <LI> The effect of the fiber shape on the length and propagation angle of cracks is investigated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

고온고습환경이 Sn계 무연솔더의 부식 및 기계적 특성에 미치는 영향

김정아(Jeonga Kim),박유진(Yujin Park),오철민(Chul Min Oh),홍원식(Won Sik Hong),고용호(Yong-Ho Ko),안성도(Sungdo Ahn),강남현(Namhyun Kang) 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.3

The effect of high temperature-moisture on corrosion and mechanical properties for Sn-0.7Cu, Sn-3.0Ag-0.5Cu (SAC305) solders on flexible substrate was studied using Highly Accelerated Temperature/Humidity Stress Test(HAST) followed by three-point bending test. Both Sn-0.7Cu and SAC305 solders produced the internal SnO2 oxides. Corrosion occurred between the solder and water film near flexible circuit board/copper component. For the SAC305 solder with Ag content, furthermore, octahedral corrosion products were formed near Ag3Sn. For the SAC305 and Sn-0.7Cu solders, the amount of internal oxide increased with the HAST time and the amount of internal oxides was mostly constant regardless of Ag content. The size of the internal oxide was larger for the Sn-0.7Cu solder. Despite of different size of the internal oxide, the fracture time during threepoint bending test was not significantly changed. It was because the bending crack was always initiated from the three-point corner of the chip. However, the crack propagation depended on the oxides between the flexible circuit board and the Cu chip. The fracture time of the three-point bending test was dependent more on the crack initiation than on the crack propagation

Design and FEM Analysis of Multilayer Ceramic Capacitors with Improved Bending and Thermal Shock Crack Performance

Lee Chang-Ho,Yoon Jung-Rag 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.4

This study presents a fi nite-element-method analysis of the bending and thermal shock crack performance of multilayer ceramic capacitors (MLCCs) used in automobiles. The stress, strain, and heat fl ux values were analyzed for diff erent MLCC structures and material parameters using three-point bending test and thermal shock test simulations. Three-dimensional modeling was performed using the actual design values of an MLCC—1005 size and 1 μF capacitance—and simulations were performed after setting the boundary and analysis conditions for the three-point bending and thermal shock tests. Based on the analyzed simulation results, the stress, strain, and heat fl ux values applicable to the MLCC were compared and analyzed to determine the optimum modeling parameters that could improve its reliability under harsh environmental conditions. This study was able to confi rm the structural stress and strain changes, and the results were found to be useful to optimize the design of automotive MLCC devices

Efficient Prediction of Local Failures for Metallic Sandwich Plates with Pyramidal Truss Cores during the Bending Processes

성대용,정창균,양동열,정완진 한국정밀공학회 2011 International Journal of Precision Engineering and Vol. No.

An efficient method that employs the virtual equivalent projected model (VEPM) is introduced and formulated in this study to simulate local failures in face sheets and cores of sandwich plates with pyramidal truss cores. This approach is based on two-dimensional FE-analysis that uses the projected shapes of 3D pyramidal truss cores and utilizes virtual properties from the homogenized equivalent elastic-plastic properties of the original material and geometries. To establish the validity of this approach, virtual equivalent projected models are applied to three-point bending, clamped bending and U-bending analyses. The results of simulations have shown that the load-displacement curves and deformed shapes with local failures of the VEPM are analogous to 3D pyramidal cores in three types of bending processes irrespective of the materials and core geometries. In addition, the computational time was greatly reduced. The practicality of this approach has been shown through comparison with the experimental results.

프레스 도어 임팩트 빔 경사각이 굽힘 강도에 미치는 영향

이상민(Sangmin Lee),강성종(Sungjong Kang) 한국자동차공학회 2019 한국 자동차공학회논문집 Vol.27 No.6

The bending strength of the inclined press door impact beam was numerically evaluated. First, three-point bending analyses were carried out with a changing beam inclination angle. Next, using the system model, including spring elements, which represent the body stiffnesses at the door mounting areas, the modeling simplification was discussed, and the effects of the impact beam inclination was examined. Finally, the structure reinforcement methods required for achieving the strain energy of the horizontal impact beam were inspected. The beam thickness and body mounting stiffness increases were separately considered. Prior to optimizing the beam section shape and increasing the material strength, it is critical to minimize the inclination angle of the door impact beam at the initial design stage.

Plastic collapse and energy absorption of empty circular aluminum tube under transverse quasi-static loading

Yeo Kiam Beng,Mohd Noh Dalimin,Muaz Abdul Wahab,Hu Lai 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8

This paper presents an experimental investigation on plastic collapse and energy absorption of empty circular aluminum tubes under quasi-static transverse loading. Tubular structures being a critical demand as material saving, high energy absorption and good strength characteristics were of major concerns due to its wall thinness, and so, its various diameter-to-thickness (D/t) ratios and span lengths. Studies found that empty circular Al-tube structure subjected to transverse standard three-point bending loading undergone three plastic deformation phases, starting with crumpling phase, crumpling and buckling phase, and lastly the structural collapse. The results found that energy absorption of empty aluminum tubes for a constant D/t ratio decreases as span length. On the contrary, the energy absorption of empty aluminum tubes for a given constant span length increases with the increase in D/t ratio.

Bending Performance of a Jute Fiber and Epoxy Resin Composite Sandwich Structure with a Bi-directional Corrugated Truss Core

Shuguang Li,Yanxia Feng,Jiankun Qin,Shuai Li,Gaoyuan Ye,Yingcheng Hu 한국섬유공학회 2019 Fibers and polymers Vol.20 No.10

In this study, a bi-directional corrugated lattice sandwich structure was fabricated from jute fibers and epoxy resin. Die casting was used to prepare the core struts and face sheets and two fiber composites were designed to produce structuralstruts. The configuration and the relative density of the core layer were altered. In addition, the three-point bending propertiesof each configuration were investigated to explore the various modes of failure, destruction processes, and mechanicalproperties. Results of the experiments show that failure mainly occurs via three modes: face sheet crushing, face sheetwrinkling, and core member crushing. Moreover, the failure mode is related to the strength of the core struts. Theoreticalcalculations and finite element analysis were carried out, and the simulation results were in good agreement withexperimental results, the relative errors of displacement and load are all within 20 %. In conclusion, the proposed sandwichbeam configuration composed of jute fibers could be highly useful for enhancing engineering structurer owing to the simplefabrication process, moreover, the materials are environmentally friendly and inexpensive.

Generalized fracture toughness for specimens with re-entrant corners: Experiments vs. theoretical predictions

Carpinteri, Alberto,Cornetti, Pietro,Pugno, Nicola,Sapora, Alberto,Taylor, David Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.5

In this paper the results of a series of experimental tests upon three-point bending specimens made of polystyrene and containing re-entrant corners are firstly described. Tests involved different notch angles, different notch depths and finally different sizes of the samples. All the specimens broke at the defect, as expected because of the material brittleness and, hence, the generalized stress intensity factor was expected to be the governing failure parameter. Recorded failure loads are then compared with the predictions provided by a fracture criterion recently introduced in the framework of Finite Fracture Mechanics: fracture is assumed to propagate by finite steps, whose length is determined by the contemporaneous fulfilment of energy balance and stress requirements. This fracture criterion allows us to achieve the expression of the generalized fracture toughness as a function of the tensile strength, the fracture toughness and the notch opening angle. Comparison between theoretical predictions and experimental data turns out to be more than satisfactory.