• Steel and Composite Structures
• /
• v.38 no.6
• /
• pp.671-690
• /
• 2021

Seismic responses of RC core wall with two outriggers are investigated in this study. In the models analyzed here, one of the outriggers is fixed at the top of the building and the second is placed at different levels along the height of the system. Each of the systems resulting from the placement of the outrigger at different locations is designed according to the prescriptive codes. The location of the outrigger changes along the height. Linear design of all the structures is accomplished by using prescriptive codes. Buckling restrained braces (BRBs) are used in the outriggers and forward directivity near fault and far fault earthquake record sets are used at maximum considered earthquake (MCE) level. Results from nonlinear time history analysis demonstrate that BRB outriggers can change the seismic responses like force distribution and deformation demand of the RC core-walls over the height and lead to the new plastic hinge arrangement over the core-wall height. Plasticity extension in the RC core wall occurs at the base as well as adjacent to the outrigger levels. Considering the maximum inter-story drift ratio (IDR) demand as an engineering parameter, the best location for the second outrigger is at 0.75H, in which the maximum IDR at the region upper the second outrigger level is approximately equal to the corresponding value in the lower region.

• Transactions of Materials Processing
• /
• v.32 no.3
• /
• pp.122-128
• /
• 2023

As electric vehicles (EV) have increasingly replaced the conventional vehicles with internal combustion engines (ICE), most of automotive makers are actively devoting to the technology development of EV parts. Accordingly, the manufacturing process for power source has been also shifting from engine/transmission to EV motor/reducer system. However, lack of experience in developing the EV motor still remains as a technical challenge. In this paper, we employed the forming simulation based on finite element modeling to solve this problem. In particular, in order to increase the accuracy of the forming simulation, we introduced the elastic-plastic constitutive model parameters for polymer-copper hybrid wire by investigating the individual strain-stress curves, and elastic modulus of polymer and copper. Then, the reliability of modeling procedure was confirmed by comparing the simulated results with experiments. Finally, the identified mechanical properties and finite element modeling were applied to a hairpin forming process, which involves multiple deformation paths such as bending, pressing, widening, and twisting. The proposed numerical approach can replace common experience or experiment based trials by reducing production time and cost in the future.

• Corrosion Science and Technology
• /
• v.22 no.4
• /
• pp.297-303
• /
• 2023

This study aimed to evaluate hydrogen permeation behaviors of pre-strained twinning-induced plasticity steel with or without Zn coating using electrochemical permeation technique. In contrast to un-strained and 30% strained samples, permeation current density was measured in the 60% strained sample. Tensile pre-straining at 60% involved microstructural modifications, including a high level of dislocation density and stacking fault with a semi-coherent twin boundary, which might provide a high diffusion path for hydrogen atoms. However, reproducibility of measurements of hydrogen permeation current was low due to non-uniform deformation and localized stress concentration. On the other hand, the permeation current was not measured in pre-strained TWIP steel with Zn coating. Instead, numerous blisters with some cracks were observed on the surface of the coating layer. In locally damaged Zn coating under tensile straining, hydrogen atoms could relatively easily permeate through the coating layer. However, they were trapped at the interface between the coating layer and the substrate, which might delay hydrogen penetration into the steel substrate.

• Journal of the Korean Society for Precision Engineering
• /
• v.11 no.4
• /
• pp.58-68
• /
• 1994

An equilibrium approach is suggested as an effective tool for the analysis of sheet metal forming processes on the basis of force balance together with geometric relations and plasticity theroy. In computing a force balance equation, it is required to define a geometric curve approximating the shape of the sheet metal at any step of deformation from the geometric interaction between the die and the deforming sheet. Then the geometic informations for contacting and non-contacting sections of the sheet metal such as the number and length of both non-contact region, contact angle, and die radius of contact section are known from the geometric forming curve and utilized for optimization by force balance equation. In computation, the sheet material is assumed to be of normal amisotropy and rigid-phastic workhardening. It has been shown that there are good agreements between the equilibrium approach and FEM computation for the benchmark test example and auto-body panels whose sections can be assumed in plane-strain state. The proposed equilibrium approach can thus be used as a robust computational method in estimating the forming defects and forming severity rather quickly in the die design stage.

• Advances in Computational Design
• /
• v.8 no.2
• /
• pp.97-112
• /
• 2023

The Finite Element (FE) modeling of Reinforced Concrete (RC) under seismic loading has a sensitive impact in terms of getting good contribution compared to experimental results. Several idealized model types for simulating the nonlinear response have been developed based on the plasticity distribution alone the model. The Continuum Models are the most used category of modeling, to understand the seismic behavior of structural elements in terms of their components, cracking patterns, hysteretic response, and failure mechanisms. However, the material modeling, contact and nonlinear analysis strategy are highly complex due to the joint operation of concrete and steel. This paper presents a numerical simulation of a chosen RC column under monotonic and cyclic loading using the FE Abaqus, to assessthe hysteretic response and failure mechanisms in the RC columns, where the perfect bonding option is used for the contact between concrete and steel. While results of the numerical study under cyclic loading compared to experimental tests might be unsuccessful due to the lack of bond-slip modeling. The monotonic loading shows a good estimation of the envelope response and deformation components. In addition, this work further demonstrates the advantage and efficiency of the damage distributions since the obtained damage distributions fit the expected results.

• Transactions of Materials Processing
• /
• v.32 no.4
• /
• pp.180-190
• /
• 2023

This study deals with residual stress prediction and hardness evaluation within cross ball grooved inner race fabricated by cold upsetting process consisted of upsetting and ejection steps. A raw workpiece material of AISI 5120H (SCr420H) is first spheroidized and annealed, then phosphophyllite coated to form solid lubricant layer on its outer surface. To investigate influences of the heat treatment, uni-axial compression tests and Vickers micro-hardness measurements are conducted. Three-dimensional elasto-plastic FE simulations on the upsetting step and the ejection one are performed to visualize the residual stress and the ductile (plastic deformation) damage. External feature of the fabricated inner race is fully captured by using an optical 3D scanner, and the micro-hardness is measured on internal cross-sections. Consequently, the dimensional compatibility between the simulated inner race and the fabricated one is ensured with a difference of under 0.243mm that satisfied permissible error range of ±0.50mm on the grooved surface, and the predicted residual stress is verified to have similar distribution tendency with the measured Vickers micro-hardness.

• Transactions of Materials Processing
• /
• v.32 no.1
• /
• pp.5-11
• /
• 2023

The aim of this study is to manufacture an aluminum pipe yoke of automotive steering system for lightweight. In a multistage cold forging process for aluminum pipe yoke, the surface defects frequently occur due to excessive deformation or friction during extrusion process for forming hollow pipe part. It is import to reduce the friction between the material and the forging die. This study investigated a multistage forging process with sliding die to reduce friction for aluminum pipe yoke. After evaluating by FE analysis, the forging experiment with the sliding die was carried out. As a result, it was possible to manufacture a sound aluminum pipe yoke.

• Transactions of Materials Processing
• /
• v.33 no.1
• /
• pp.5-11
• /
• 2024

The development of a next-generation hydrogen compressor, a key component in the expansion of hydrogen charging infrastructure, is in progress. In order to improve compression efficiency and durability, it is important to optimize the precision forming and shearing processes of the diaphragm, which is the bellows unit cell, as well as the optimization of diaphragm shape itself. In this study, we aim to show that die and process design technology that can synchronize the inner and outer shearing points of the diaphragm for the precision forming of product can be constructed based on a numerical simulation. First, the damage model that can predict the fracture points will be determined using the shear load and shear zone measurements obtained by performing a blanking test of AISI-633 stainless steel. Next, we will explain the overall procedure based on numerical analysis model how to determine the shearing points according to the deformation pattern of urethane die for various shearing die design.

• Transactions of Materials Processing
• /
• v.33 no.1
• /
• pp.50-54
• /
• 2024

In this paper, the process of extruding Cu-10Fe alloy using a finite element analysis (FEA) was theoretically analyzed. To achieve this, the dependence of strain rate and temperature of the alloy required for the extrusion process was secured by utilizing databases for Cu and Fe and the KHL model. For microstructure analysis, FE-SEM with EDS was used to distinguish the phases present in Cu-10Fe alloy. The mechanical characteristics of Cu-10Fe alloy were secured using the results of fitting the mechanical properties of Copper and Steel from the Deform database to the KHL model. The deformation behavior within the alloy during hot extrusion was analyzed, providing insights into effective stress, effective strain, effective strain rate, and temperature. It was observed that the strain distribution was non-uniform. These research findings contribute to an improved understanding of the hot extrusion process of Cu-10Fe alloy and can aid in predicting the mechanical properties of the material.

• Computers and Concrete
• /
• v.11 no.2
• /
• pp.123-148
• /
• 2013

The nonlinear finite element method with eight noded isoparametric quadrilateral element for concrete and two noded element for reinforcement is used for the prediction of the behavior of reinforcement concrete structures. The disturbed state concept (DSC) including the hierarchical single surface (HISS) plasticity model with associated flow rule with modifications is used to characterize the constitutive behavior of concrete both in compression and in tension which is named DSC/HISS-CT. The HISS model is applied to shows the plastic behavior of concrete, and DSC for microcracking, fracture and softening simulations of concrete. It should be noted that the DSC expresses the behavior of a material element as a mixture of two interacting components and can include both softening and stiffening, while the classical damage approach assumes that cracks (damage) induced in a material treated acts as a void, with no strength. The DSC/HISS-CT is a unified model with different mechanism, which expresses the observed behavior in terms of interacting behavior of components; thus the mechanism in the DSC is much different than that of the damage model, which is based on physical cracks which has no strength and interaction with the undamaged part. This is the first time the DSC/HISS-CT model, with the capacity to account for both compression and tension yields, is applied for concrete materials. The DSC model allows also for the characterization of non-associative behavior through the use of disturbance. Elastic perfectly plastic behavior is assumed for modeling of steel reinforcement. The DSC model is validated at two levels: (1) specimen and (2) practical boundary value problem. For the specimen level, the predictions are obtained by the integration of the incremental constitutive relations. The FE procedure with DSC/HISS-CT model is used to obtain predictions for practical boundary value problems. Based on the comparisons between DSC/HISS-CT predictions, test data and ANSYS software predictions, it is found that the model provides highly satisfactory predictions. The model allows computation of microcracking during deformation leading to the fracture and failure; in the model, the critical disturbance, Dc, identifies fracture and failure.