• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.288-291
• /
• 2006

Piercing or blanking process is widely used to manufacture most of lead frame parts, but it is difficult to analyze the real process by the actual shape through progressive dies. In this paper several stages in progressive punching are modeled by 2D and 3D configurations using $DEFORM^{TM}$ 2D/ 3D code. During the progressive stage some state variables and deformed configurations are analyzed in each model. There are three stages in the process, the deformations at each stage are cumulative. The advantages and disadvantages of these two type modeling are discussed and analyzed. The experiments are performed as a working material copper alloy through manufactured die. Computed results in load by two types are compared to experiments.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.2 no.2
• /
• pp.45-51
• /
• 2003

The multi-piloting type progressive die for U-bending sheet metal production part is a very specific division. This study reveals the sheet metal forming process with multi-forming die by center carrier type feeding system. Through the FEM simulation by DEFORM, it was accepted to u-bending process as the first performance to design of strip process layout. The next process of die development was studied according to sequence of die development, i.e die structure, machining condition for die making, die materials, heat treatment of partially die components, know-how and so on. The feature of this study is the die development of scrapless progressive die of multi-stage through the modeling on the I-DEAS program, components drawing on the Auto-LISP, CAD/CAM application, ordinary machine tool operating and revision by tryout.

• Structural Engineering and Mechanics
• /
• v.59 no.1
• /
• pp.59-82
• /
• 2016

Simplifier assumptions which are used in numerical studies of progressive collapse phenomenon in structures indicate inconsistency between the numerical and experimental full-scale results. Neglecting the effects of infill panels and two-dimensional simulation are some of these assumptions. In this study, an existing seismically code-designed steel building is analyzed with alternate path method (AP) to assess its resistance against progressive collapse. In the AP method, the critical columns be removed immediately and stability of the remaining structure is investigated. Analytical macro-model based on the equivalent strut approach is used to simulate the effective infill panels. The 3-dimentional nonlinear dynamic analysis results show that modeling the slabs and infill panels can increase catenary actions and stability of the structure to resist progressive collapse even if more than one column removed. Finally, a formula is proposed to determine potential of collapse of the structure based on the quantity and quality of the produced plastic hinges in the connections.

• Structural Engineering and Mechanics
• /
• v.37 no.1
• /
• pp.79-93
• /
• 2011

A simple mechanical model is proposed to demonstrate qualitatively the pancake progressive collapse of multi-storey structures. The impact between two collapsed storeys is simulated using a simple algorithm that builds on virtual mass-spring-damper system. To analyze various collapse modes, columns and beams are considered separately. Parametric studies show that the process of progressive collapse involves a large number of complex mechanisms. However, the proposed model provides a simple numerical tool to assess the overall behavior of collapse arising from a few initiating causes. Unique features, such as beam-to-beam connection failure criterion, and beam-to-column connection failure criterion are incorporated into the program. Besides, the criterion of local failure of structural members can also be easily incorporated into the proposed model.

• Journal of Computing Science and Engineering
• /
• v.6 no.3
• /
• pp.219-226
• /
• 2012

Recently, shape analysis of human organs has achieved much attention, owing to its potential to localize structural abnormalities. For a group-wise shape analysis, it is important to accurately restore the shape of a target structure in each subject and to build the inter-subject shape correspondences. To accomplish this, we propose a shape modeling method based on the Laplacian deformation framework. We deform a template model of a target structure in the segmented images while restoring subject-specific shape features by using Laplacian surface representation. In order to build the inter-subject shape correspondences, we implemented the progressive weighting scheme for adaptively controlling the rigidity parameter of the deformable model. This weighting scheme helps to preserve the relative distance between each point in the template model as much as possible during model deformation. This area-preserving deformation allows each point of the template model to be located at an anatomically consistent position in the target structure. Another advantage of our method is its application to human organs of non-spherical topology. We present the experiments for evaluating the robustness of shape modeling against large variations in shape and size with the synthetic sets of the second cervical vertebrae (C2), which has a complex shape with holes.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.2 s.173
• /
• pp.455-463
• /
• 2000

In order to develop nondestructive techniques for the quantitative estimation of creep damage a series of crept copper samples were prepared and their ultrasonic velocities were measured. Velocities measured in three directions with respect to the loading axis decreased nonlinearly and their anisotropy increased as a function of creep-induced porosity. A progressive damage model was described to explain the void-velocity relationship, including the anisotropy. The comparison of modeling study showed that the creep voids evolved from sphere toward flat oblate spheroid with its minor axis aligned along the stress direction. This model allowed us to determine the average aspect ratio of voids for a given porosity content. A novel technique, the back propagation neural network (BPNN), was applied for estimating the porosity content due to the creep damage. The measured velocities were used to train the BP classifier, and its accuracy was tested on another set of creep samples containing 0 to 0.7 % void content. When the void aspect ratio was used as input parameter together with the velocity data, the NN algorithm provided much better estimation of void content.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.233-238
• /
• 1999

Localized failure analysis of concrete structures can be carried out effectively by modeling fracture process zone of concrete during crack initiation and propagation. But, the analysis techniques are still insufficient for crack modeling because of difficulties in numerical analysis procedure which describe progressive crack. In this paper, a finite element with embedded displacement discontinuity is introduced to remove the difficulties of remeshing for crack propagation in discrete crack model during progressive failure analysis of concrete structures. The performance of this so-called embedded crack approach for concrete failure analysis is verified by several analysis examples. The analysis results show that the embedded crack approach retains mesh size objectivity and can simulate localized failure under mixed mode loading. It can be concluded that the embedded crack approach cab be an effective alternate to the smeared and discrete crack approaches.

• Earthquakes and Structures
• /
• v.18 no.5
• /
• pp.649-665
• /
• 2020

One of the most important issues in structural systems is evaluation of the margin of safety in low and mid-rise buildings against the progressive collapse mechanism due to the earthquake loads. In this paper, modeling of collapse propagation in structural elements of RC frame buildings is evaluated by tracing down the collapse points in beam and column structural elements, one after another, under earthquake loads and the influence of column removal is investigated on how the collapse expansion in beam and column structural members. For this reason, progressive collapse phenomenon is studied in 3-story and 5-story intermediate moment resisting frame buildings due to the corner and edge column removal in presence of the earthquake loads. In this way, distribution and propagation of the collapse in progressive collapse mechanism is studied, from the first element of the structure to the collapse of a large part of the building with investigating and comparing the results of nonlinear time history analyses (NLTHA) in presence of two-component accelograms proposed by FEMA_P695. Evaluation of the results, including the statistical survey of the number and sequence of the collapsed points in process of the collapse distribution in structural system, show that the progressive collapse distribution are special and similar in low-rise and mid-rise RC buildings due to the simultaneous effects of the column removal and the earthquake loads and various patterns of the progressive collapse distribution are proposed and presented to predict the collapse propagation in structural elements of similar buildings. So, the results of collapse distribution patterns and comparing the values of collapse can be utilized to provide practical methods in codes and guidelines to enhance the structural resistance against the progressive collapse mechanism and eventually, the value of damage can be controlled and minimized in similar buildings.

• Earthquakes and Structures
• /
• v.18 no.6
• /
• pp.691-707
• /
• 2020

One of the most important issues in structural systems is evaluation of the margin of safety in low and mid-rise buildings against the progressive collapse mechanism due to the earthquake loads. In this paper, modeling of collapse propagation in structural elements of RC frame buildings is evaluated by tracing down the collapse points in beam and column structural elements, one after another, under earthquake loads and the influence of column removal is investigated on how the collapse expansion in beam and column structural members. For this reason, progressive collapse phenomenon is studied in 3-story and 5-story intermediate moment resisting frame buildings due to the corner and edge column removal in presence of the earthquake loads. In this way, distribution and propagation of the collapse in progressive collapse mechanism is studied, from the first element of the structure to the collapse of a large part of the building with investigating and comparing the results of nonlinear time history analyses (NLTHA) in presence of two-component accelograms proposed by FEMA_P695. Evaluation of the results, including the statistical survey of the number and sequence of the collapsed points in process of the collapse distribution in structural system, show that the progressive collapse distribution are special and similar in low-rise and mid-rise RC buildings due to the simultaneous effects of the column removal and the earthquake loads and various patterns of the progressive collapse distribution are proposed and presented to predict the collapse propagation in structural elements of similar buildings. So, the results of collapse distribution patterns and comparing the values of collapse can be utilized to provide practical methods in codes and guidelines to enhance the structural resistance against the progressive collapse mechanism and eventually, the value of damage can be controlled and minimized in similar buildings.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.32 no.4
• /
• pp.233-240
• /
• 2019

Open-hole tensile tests are usually performed to measure the tensile strengths of composites as they are an essential parameter for designing composite structures. However, correctly modeling the tensile test is extremely challenging as it involves various damages such as fiber and matrix damage, delamination, and debonding damage between the fiber and matrix. Therefore, a progressive damage model was developed in this study to estimate the in-plane failure and delamination between the fiber and matrix. The Hashin damage model and cohesive zone approach were used to model ply and delamination failures. The results of the present model were compared with previously published experimental and numerical findings. It was observed that neglecting delamination during finite element analysis led to overestimation of tensile strength.