• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1240-1243
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• 2005

The wrinkling in the flange and wall of a part is a predominant failure mode in stamping of sheet metal parts. In many cases this wrinkling may be eliminated by appropriate control of the blank holding force(BHF), but BHF affects the draw depth. Gotoh had studied the wrinkles under $20{\mu}$ in height. In general, the height of wrinkles could be limited under $200{\mu}$ practically. Therefore small BHF can be allowed so that the depth of drawing could be increased. This paper represents the variation of the wrinkles of flange in the part of cup drawing by using aluminium alloy A1050 and A5052. This simulation is used by the explicit finite elements code $PAM-STAMP^{TM}$. The computed results are compared with the experimental results to show the validity of the analysis.

• Smart Structures and Systems
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• v.15 no.4
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• pp.1019-1039
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• 2015

Shanghai Tower is a composite structure building with a height of 632 m. In order to verify the structural properties and behaviors in construction and operation, a structural health monitoring project was conducted by Tongji University. The monitoring system includes sensor system, data acquisition system and a monitoring software system. Focusing on the health monitoring in construction, this paper introduced the monitoring parameters in construction, the data acquisition strategy and an integration structural health monitoring (SHM) software. The integration software - Structural Monitoring/ Analysis/ Evaluation System (SMAE) is designed based on integration and modular design idea, which includes on-line data acquisition, finite elements and dynamic property analysis functions. With the integration and modular design idea, this SHM system can realize the data exchange and results comparison from on-site monitoring and FEM effectively. The analysis of the monitoring data collected during the process of construction shows that the system works stably, realize data acquirement and analysis effectively, and also provides measured basis for understanding the structural state of the construction. Meanwhile, references are provided for the future automates construction monitoring and implementation of high-rise building structures.

• Transactions of Materials Processing
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• v.12 no.8
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• pp.710-717
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• 2003

The implicit, finite element analysis program for analyzing the springback in the warm forming process of aluminum alloy sheets was developed. For the description of planar anisotropy in warm forming temperatures, Barlat's yield function is employed, and the power law type constitutive equation is used in terms of working temperatures for the depiction of work hardening in high temperatures. Also, Jetture's 4-node shell elements are introduced for reflecting the mechanical behavior of aluminum alloy sheet and the non-steady heat balance equations are solved for considering heat gain and loss during the forming process. For the springback evaluation, Newton-Raphson iteration method is introduced for overcoming the geometric nonlinearlity problem. In order to verify the validity of the FEM program developed, the stretching bending and springback processes are simulated. Though springback analysis results are slightly bigger than experimental ones, they have the same trend of the decreasing springback as the forming temperature increases.

• Steel and Composite Structures
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• v.26 no.3
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• pp.265-272
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• 2018

A detailed study was carried out on the tensile properties of the single-lap joint of a steel panel bolted/bonded to a composite laminate with a flanging. Finite element model (FEM) was established to predict the strength and to analyze the damage propagation of the hybrid joints by ABAQUS/Standard, which especially adopted cohesive elements to simulate the interface between the laminate and adhesive. The strength and failure mode predicted by FEM were in good agreement with the experimental results. In addition, three influence factors including adhesive thickness, bolt preload and bolt-hole clearance were studied. The results show that the three parameters have effect on the first drop load of the load-displacement curve, but the effect of bolt-hole clearance is the largest. The bolt-hole clearance should be avoided for hybrid joints.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.08a
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• pp.13-20
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• 2003

The implicit, finite element analysis program for analyzing the springback in the warm forming process of aluminum alloy sheets was developed. For the description of planar anisotropy in warm forming temperatures, Barlat's yield function is employed, and the power law type constitutive equation is used in terms of working temperatures fur the depiction of work hardening in high temperatures. Also, Jetture's 4-node shell elements are introduced for reflecting the mechanical behavior of aluminum alloy sheet and the non-steady heat balance equations are solved for considering heat gain and loss during the forming process. For the springback evaluation, Newton-Raphson iteration method is introduced for overcoming the geometric nonlinearlity problem. In order to verify the validity of the FEM program developed, the stretching bending and springback processes are simulated. Though springback analysis results are slightly bigger than experimental ones, they have the same trend of the decreasing springback as the forming temperature increases.

• Computers and Concrete
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• v.17 no.1
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• pp.141-156
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• 2016

The search for new structural systems capable of associating performance and safety requires deeper knowledge regarding the mechanical behavior of structures subject to different loading conditions. The Strut-and-Tie Model is commonly used to structurally designing some reinforced concrete elements and for the regions where geometrical modifications and stress concentrations are observed, called "regions D". This method allows a better structural behavior representation for strength mechanisms in the concrete structures. Nonetheless, the topological model choice depends on the designer's experience regarding compatibility between internal flux of loads, geometry and boundary/initial conditions. Thus, there is some difficulty in its applications, once the model conception presents some uncertainty. In this context, the present work aims to apply the Strut-and-Tie Model to nonlinear structural elements together with a topological optimization method. The topological optimization method adopted considers the progressive stiffness reduction of finite elements with low stress values. The analyses performed could help the structural designer to better understand structural conceptions, guaranteeing the safety and the reliability in the solution of complex problems involving structural concrete.

• Computers and Concrete
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• v.34 no.1
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• pp.1-14
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• 2024

The design of disturbed regions in reinforced concrete structures usually applies the well known Strut and Tie Method (STM). As an alternative, the Stringer-Panel Method (SPM), an intermediate model between STM and the Finite Element Method (FEM), consists in dividing a structure into two distinct elements: the stringers (which carry axial forces) and panels (which carry shear forces). SPM has already showed good applicability in manual calculations and computer implementations, and its most known application was SPanCAD, an AutoCAD plugin for linear and nonlinear analysis by SPM. Unfortunately, SPanCAD was discontinued by the developers, and it's not compatible with the most recent versions of AutoCAD. So, this paper aims to present a computer program that was developed as an upgrade to the latter: the Stringer Panel Modelling Tool (SPMTool), which is intended to be an auxiliary design tool and it presents improvements, in comparison to SPanCAD. It is possible to execute linear and nonlinear analysis by three distinct formulations: Modified Compression Field Theory (MCFT), Disturbed Stress Field Model (DSFM) and Softened Membrane Model (SMM). The nonlinear results were compared to experimental data of reinforced concrete elements that were not designed by SPM; these elements were also analyzed in SPanCAD. On overall, SPMTool made more realistic predictions to the behavior of the analyzed structures than SPanCAD. Except for DSFM predictions for corbels (1.24), in overall average, the ultimate load predictions were conservative (0.85 to 0.98), which is a good aspect for a design tool. On the other hand, the cracking load predictions presented overestimations (1.06 to 1.47) and higher variations (25.59% to 34.25%) and the post-cracking behavior could not be accurately predicted; for this use case, a more robust finite element software is recommended.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.4
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• pp.310-323
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• 2013

In this paper, the aeroelastic static response of flexible wings with arbitrary cross-section geometry via a coupled CUF-XFLR5 approach is presented. Refined structural one-dimensional (1D) models, with a variable order of expansion for the displacement field, are developed on the basis of the Carrera Unified Formulation (CUF), taking into account cross-sectional deformability. A three-dimensional (3D) Panel Method is employed for the aerodynamic analysis, providing more accuracy with respect to the Vortex Lattice Method (VLM). A straight wing with an airfoil cross-section is modeled as a clamped beam, by means of the finite element method (FEM). Numerical results present the variation of wing aerodynamic parameters, and the equilibrium aeroelastic response is evaluated in terms of displacements and in-plane cross-section deformation. Aeroelastic coupled analyses are based on an iterative procedure, as well as a linear coupling approach for different free stream velocities. A convergent trend of displacements and aerodynamic coefficients is achieved as the structural model accuracy increases. Comparisons with 3D finite element solutions prove that an accurate description of the in-plane cross-section deformation is provided by the proposed 1D CUF model, through a significant reduction in computational cost.

• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.235-243
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• 2017

Carbonation of concrete is being occurred due to interaction of atmospheric carbon dioxide with hydroxides. Reinforce concrete (RC) structure is getting collapse or accident due to corrosion of embedded steel rebar. The maintenance of reinforced concrete structure recently has the attention of researchers regarding durability of structure and its importance day by day is increasing. In order to study the carbonation progress of pre-repaired concrete, present study was carried out to measure the carbonation velocity for different repair materials up to 100% of carbonation. The obtained results have predicted the carbonation progress of repair materials in service condition. These results have been verified by FEM and FDM analysis. As a result, the carbonation depth can be predicted by using the carbonation prediction formula after the repair, and the analytical and the experimental values are almost similar when the initial $Ca(OH)_2$ concentration is assumed to be 40%.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.4
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• pp.397-404
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• 2010

The use of equivalent circuit models of piezoelectric energy harvesters is inevitable when power circuitry including rectifying and smoothing circuit elements is connected to them for evaluating DC electrical outputs. This is because it is difficult to incorporate the electro-mechanical coupling resulting from the additional circuitry into the conventional finite element analysis. Motivated by this observation, we propose a method to accurately extract the equivalent circuit parameters by using commercially available FEM software such as ANSYS which provides three-dimensional AC piezoelectric analysis. Then the equivalent circuit can be analyzed by circuit simulators such as $SimPowerSystems^{TM}$ of MATLAB. While the previous works have estimated the circuit parameters by experimental measurements or by analytical solutions developed only for limited geometries and boundary conditions, the proposed method has no such limitation because piezoelectric energy harvesters of any shapes and boundary conditions can be treated in FEM software. For the verification of the proposed method, multi-modal AC electrical power output by using a corresponding equivalent circuit is compared with that by ANSYS. The proposed method is then shown to be very useful in the subsequent evaluation of DC electrical output which is obtained by attaching a bridge diode and a storage capacitor to a piezoelectric energy harvester.