• Steel and Composite Structures
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• v.5 no.1
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• pp.49-70
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• 2005

This paper reports on finite element analysis techniques that may be applied to the study of circular hollow structural sections and related bearing connection geometries. Specifically, a connection detail involving curved steel saddle bearings and a Structural Tee (ST) connected directly to a large-diameter Hollow Structural Section (HSS) truss chord, near its open end, is considered. The modeling is carried out using experimentally verified techniques. It is determined that the primary mechanism of failure involves a flexural collapse of the HSS chord through plastification of the chord wall into a well-defined yield line mechanism; a limit state for which a shell-based finite element model is well-suited to capture. It is also found that classical metal plasticity material models may be somewhat limited in their applicability to steels in fabricated tubular members.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.4
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• pp.23-29
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• 2001

The compression behavior of semi-solid materials is studied from a viewpoint of yield criteria and analysis methods. To describe the behavior of materials in semi-solid state, several theories have been proposed by extending the concept of plasticity of porous compressible materials. In the present work, the upper-bound method and the finite element method are used to model the simple compression process using yield criteria of Kuhn and Doraivelu. Segregation between solid and liquid which cause defect of product is analysed for Sn-15%Pb and A356 alloys during deformation in semi-solid state. The comparison of analyses is made according to yield criteria and analysis methods. In addition, the analysis result for semi-solid dendritic Sn-15%Pb alloy is compared with the experimental result of Charreyron et al..

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.533-538
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• 2006

A simplified numerical procedure to predict drawbead restraining forces(DBRF) has been developed based on the hybrid membrane/bending method which superposes bending effects onto membrane solutions. As a semi-analytical method, the new approach is especially useful to analyze the effects of various constitutive parameters. The present model can accommodate general anisotropic yield functions along with non-linear isotropic-kinematic hardening under the plane strain condition. For the preliminary results, several sensitivity analyses for the process and material effects such as friction, drawbead depth, hardening behavior including the Bauschinger effect and yield surface shapes on the DBRF are carried out.

• Transactions of Materials Processing
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• v.18 no.8
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• pp.589-595
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• 2009

The hot forming process of an exhaust CAM for vessel engine was designed by finite element(FE) simulation and experimental analysis. An aim of process design was to achieve the near-net shaped CAM forgings by hot forging process. Based on the compression test results of the low alloy steel, power dissipation map was generated using the the dynamic materials model(DMM). From the map, the initial heating temperature was determined as 1200oC. FE analysis was simulated to predict the formation of forging defects and deformed shape with different forging designs. Optimum process design suggested in this work was made by comparing with the CAM for vessel engine manufactured by actual forging process.

• Transactions of Materials Processing
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• v.16 no.1 s.91
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• pp.15-19
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• 2007

This paper presents an integrated machining error compensation method based on captured images of tool deflection shapes in flat end-milling processes. This approach allows us to avoid modeling machining characteristics (cutting forces, tool deflections and machining errors etc.) and accumulating calculation errors induced by several simulations. For this, a high-speed camera captured images of real deformed tool shapes which were cutting under given machining conditions. Using image processes and a machining error model, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool paths. This corrected tool path can effectively reduce machining errors in the flat end-milling process. Experiments are carried out to validate the approaches proposed in this paper. The proposed error compensation method can be effectively implemented in a real machining situation, producing much smaller errors.

• Transactions of Materials Processing
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• v.25 no.2
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• pp.136-140
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• 2016

Although the finite element method is a good tool to analyze skin-pass rolling, it is hard to be applied in the field because of its long calculation time. In the current study, simple numerical models were developed for the prediction of roll force and residual stress profiles along the strip width. These models are based on finite element analysis and a coupled solution of Sims’ equation and Hitchcock’s formula. The results indicate that plastic strains can be represented as in simple equations of the deformed roll profile and the initial thickness of the strip.

• Journal of Mechanical Science and Technology
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• v.18 no.1
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• pp.55-64
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• 2004

Many researchers have made a lot of progress in studying the evaluation of fracture probability of brittle materials. However, studies of fracture probability for elastic-plasticity have not been made yet. An evaluation method for fracture probability which is grafted onto a 2-parameter criterion and statistical probability analysis is not only introduced in this study, but also applied to the simple 2-dimensional model and carbon steel piping to vealuate the effect of statistical variables.

• BMB Reports
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• v.42 no.3
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• pp.131-135
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• 2009

MicroRNAs control gene expression by inhibiting translation or promoting degradation of their target mRNAs. Since the discovery of the first microRNAs, lin-4 and let-7, in C. elegans, hundreds of microRNAs have been identified as key regulators of cell fate determination, lifespan, and cancer in species ranging from plants to humans. However, while microRNAs have been shown to be particularly abundant in the brain, their role in the development and activity of the nervous system is still largely unknown. In this review, we describe recent advances in our understanding of microRNA function at synapses, the specialized structures required for communication between neurons and their targets. We also propose how these advances might inform the molecular model of memory.

• Transactions of Materials Processing
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• v.6 no.6
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• pp.517-526
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• 1997

The purpose of this study is to investigate changes in the wall thickness of tube sinking and working forces by the upper bound method and ABAQUS code. The independent variables are ; workpiece material, original wall thickness of tube, die angle, friction, and reduction of diameter. The results indicate that these five variables are factors of the increase in wall-thickness and working forces. Three variables, a inner tube wall angle and two angles of the velocity discontinuous surfaces, are optimized in this proposed velocity field by the upper bound method. In this method, we can estimate the working forces and final tube thicknesses similar to actual forming process. Optimum process variables which are obtained by upper bound method are used in ABAQUS pre-model.

• Transactions of Materials Processing
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• v.4 no.4
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• pp.335-344
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• 1995

In this paper, an experimental study of a hot forging process is carried out using plasticine and the die set manufactured with the aid of rapid prototyping. In order to manufacture the die set, Stereolithography Apparatus(SLA) which is most widely used rapid prototyping system is introduced. Turbine blade forging is performed using palsticine and the SLA prototype die set. Through the experiment, it has been shown that SLA prototype is suitable to the die set for the plasticine workpiece, and the formability and the forming load of turbine blade forging are predicted.