aterials Forming and Processing Lab.(FURUSHIMA Lab.), Institute of Industrial Science, The University of Tokyo

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Research

About MFPL

We are conducting research on deformation process on the theme of "material deformation" related to plastic processing and plasticity engineering, which is the basic technology of "manufacturing" in Japan.

In our lab., we cover both experimental and theoretical approaches such as stamping process, tube forming, material modeling, dieless forming without using any dies and tools, micro metal forming by focusing on “permanent deformation of materials” from a standpoint of cross-cutting issues from micro to macro-scale..

In addition, we also perform international collaborated research with Russian Academy of Science (Russia), University of Wollongong (Australia), Northeastern University (China), AGH Science and Technology (Poland), Czech Technical University in Prague, (Czech) and University of New Hampshire (USA).

Our main researches are as follows;

Main topics

1. Micro Precision Stamping Process for Medical and Electrical Products

In recent year, miniaturization and high precision of product part with development of medical and electrical fields are required. The demand of scaling down of stamping forming is also needed. However, it is not easy to scale down to micro-scale due to “size effect”. For example, the relative surface roughness becomes large at micro-scale compared with macro-scale. We can regards the surface roughness as inhomogeneity of the materials, which may lead to early fracture, may affect tribological behavior and formability in micro stamping process. Furthermore, the effect of microstructure on formability at micro stamping process also become large compared with macro-scale.

From these issues, development of micro precision stamping process, material modeling considering microstructure and surface roughness and formability prediction by considering above phenomenon.

Experimental Study on Micro Precision Stamping Process

Desktop-size servo press was developed for micro precision stamping which stamping motion can be controlled by servo motor. The very small dies and tools are used for the micro stamping. Very tiny cups with diameter of 0.5mm which are smaller than an ant were fabricated successfully. We are investigating the effect of relative surface roughness and microstructure on formability such as occurrence of wrinkling and fracture.

微細精密プレス成形
Development of Material Modeling Considering Microstructure and Surface Roughness

At the scale of micro precision stamping, the relative microstructure size and surface roughness for material size becomes large. In addition, it is known that the surface roughness increases with plastic deformation on free surface without contact condition. We call this phenomenon as "Free surface roughening". The free surface roughening may affect origin of fracture and tribological behavior under contact condition with die and tool. The instable deformation such as free surface roughening is caused by material inhomogeneity such as variation in crystal orientation of grain. In particular, the material inhomogeneity cause the instable deformation during plastic deformation in micro stamping. In this study, we consider the material inhomogeneity into finite element simulation (FEM). We can predict instable deformation such as free surface roughening and fracture in the micro precision stamping successfully and can clarify its effect on tribological behavior and formability.

不均質性FEM

In-situ Observation and Visualization of Surface Roughening Using Laser Microscope

The objective of this study is to investigate the effect of surface roughening on the ductile fracture behavior. Moreover, biaxial tensile state was focused on in this study because it can be seen well in practical metal forming processes such as press-forming. To reach the objective, a hand-size stretching testing apparatus was newly developed. Owing to this apparatus, it is expected that in-situ observation of surface roughening of metal foil can be conducted. In this paper, structure of the apparatus such as efficiency of the apparatus, die dimensions and experimental setup are reported. In addition, performance tests such as measurement of strain distribution and strain paths and surface roughening observation for developed apparatus are reported using metal foils. This study was supported by JKA.

Insitu

2. Dieless Forming

In general metal forming process, we need dies and tools. However, the manufacturing dies and tools with high cost is not always needed in the case of manufacturing of a wide variety of products in small quantities. Thus, a novel dieless forming process without using any dies and tools for metal forming is focused on. The dieless forming process was effective for micro metal forming process and ultra-high temperature forming. In this study, we develop novel dieless forming process without using any dies and tools.

Fabrication of Micro Microtubes by Dieless Drawing Process

The demand of metal microtubes are needed for painless injection needle micro heat exchanger and micro nozzle in the field medical, chemical and electric fields. However, it is difficult to fabricate micro dies and tools in microtubes fabrication. In case of conventional die drawing, the miniaturization of die, mandrel and plug are needed. In this study, we developed the novel fabricating method of dieless drawing process with tensile deformation and local heating. In this study, we use the induction heating and laser as a heating source. We can fabricate successfully various metal microtubes such as Zn-22Al superplastic alloy, stainless steel, be-ta titanium. In addition, we fabricated not only circular tube but also non-circular tubes by the characteristic of geometrical similarity law in cross section during dieless drawing process.

マイクロダイレス引抜き

Microstructure Control of Biodegradable Magnesium Alloy Tube By Dieless Drawing

The dieless drawing process includes heating, cooling and plastic deformation. Thus, the microstructure after the dieless drawing may be controlled by heating and cooling temperature, strain and strain rate. In this study, we are focusing on the dieless drawing process for biodegradable magnesium alloy. Normally, the magnesium alloy is poor ductility at room temperature. However, the reduction in area in a single pass dieless drawing of 60% can be accomplished. In addition, we show the possibility of microstructure control by controlling heating temperature and reduction in area. With the support of the JKA program, we further developed this research and succeeded in manufacturing ultra-thin tubes of 3.49 mm in outer diameter and 0.48 mm in wall thickness for ZM21 magnesium alloy, and achieved high corrosion resistance by controlling the microstructure.

Mgダイレス引抜き Mgダイレス引抜き

Mgダイレス引抜き

Fabrication of Metal Tubular Microneedles with Ultra-Small Tip Diameter by Novel Dieless Drawing Using Superplastic Deformation and Fracture

Recently, microneedles with an ultrafine tip diameter have been desired as a tool for manipulating single cells in Live Cell Atlas (LCA). However, microneedles have been made of glass until now, and glass microneedles with a tip diameter of several tens of microns are difficult to apply due to their low strength and brittleness. Therefore, metal microneedles with high strength and ductility are desired to replace glass microneedles, but it is very difficult to fabricate metal microneedles with a tip diameter of several tens of microns. In this study, we developed a new method for the fabrication of metallic microneedles by applying dieless drawing technique. The conventional dieless drawing process has focused on stable drawing without breakage, but we have taken a reversal approach and fabricate a metal microneedle with a tip diameter of several tens of microns while the root diameter is 1 mm by breaking the tip at a stretch. This study was supported by JKA.

金属製マイクロニードル

Dieless Metal Bellows Forming

Metal bellows are a structural component in which a wavy bellows shape is formed on the surface of circular tubes to induce an elastic property. In this study, we developed a method of generating a difference in flow stress between the heated and cooled areas by locally heating the metal tube to induce buckling at the locally heated area with low flow stress without using any tools outside tube. In addition, we can fabricate micro metal bellows by using dieless bellows forming with laser as a heating source.

ダイレスベローズ成形

Superplastic Dieless Forming for Ceramics Tubes

In recent years, the development of fuel-cell cars has been focused on to reduce emissions of certain gases alleged to contribute to a greenhouse effect. However, the fuel-cell cars face the problem which is heavy weight of the fuel cell per of the car per power and energy. Thus, miniaturized fuel cells with high efficiency and compact are task of processing urgency to advance fuel-cell cars. As a case of miniaturization of the fuel cell, a solid-oxide fuel cell (SOFC). In general, ceramics are brittle materials so that it cannot be applied to plastic forming with mass production and low cost. However, Wakai et al. have found that the ceramics indicate superplastic deformation at an elevated temperature. However, dies and tools used in the plastic forming cannot be proof due to a high temperature, because temperature range required for superplastic deformation is from 1400 to 1700oC. Thus, it is difficult to achieve the practical use of superplastic forming of ceramics. In this study, we set fabrication of the micro ceramic tubes by using the superplastic dieless drawing process. We designed and developed a superplastic dieless drawing apparatus with acetylene burner for high temperature over 1500oC for achieving superplastic deformation of ceramic tubes. As a fundamental superplastic ceramic, 3Y-TZP zirconia ceramic tube was used to demonstrate the effectivity of proposed superplastic dieless drawing process.

セラミックスダイレス成形

3. Plasticity Evaluation with High Accuracy and Performance

High accurate simulation of metal forming has been requred recently. For that, the evaluation of plastic behavior with high accuracy is important. In this research, we aim to develop novel evaluation methods of plastic deformation characteristics by using a special evaluation technology with high accuracy and performance.

Full-field Strain Measurement using Digital Image Correlation with Laser Speckles

Digital image correlation (DIC) uses image processing techniques to obtain displacement and strain fields in a region of interest (ROI) of an objective deformed in real time. To do the correlation between two captured images, artificial speckle patterns are usually prepared by spraying paints on the sample surface. However, the peeling off issue of the paints results in the difficulty of obtaining the deformation behavior of the material in large plastic deformations, especially at elevated temperatures. Furthermore, the thickness of the paints may result in an inaccurate measurement of the true strains for thin foils. Therefore, laser speckles, formed by reflection and scattering of laser irradiation onto a rough surface, are proposed to be used in DIC.

Laser_speckle_DIC

Research

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