Welding & Joining
(Materials Joinig Science and Engineering Lab.)

Welding and Joining technique is an essential basic technology in an industrial field. Therefore, high functionalization requires an innovation of Welding and Joining technique.

Welding and Joining group aims to develop high quality/high efficiency welding process, especially are focusing on developing Hot-wire Laser welding process combination of hot-wire method and laser welding. This process has attractive advantages such as low dilution of base material, low deformation, controllable of chemical composition in weld metal and so on since melting of a filler wire and a base material can control independently and high accuracy. Various applications using Hot-wire Laser welding process has been investigated for practical use.

In addition, in-situ observation system using a high speed camera which has been developed Welding and Joining group are carried out to evaluate metallurgical phenomenon during welding and cracking susceptibility quantitatively. Properties of welded joint such as fatigue strength, corrosion resistance and so on are also investigated.

Topic
  • Development of Hot-wire laser Welding / Blazing process (Narrow gap welding, Fillet welding, Vertical welding for thick steel plate, High speed welding, Dissimilar welds, Overlay welding)
  • Evaluation of metallurgical phenomenon during welding and cracking susceptibility using in-situ observation system
  • Elucidation of fatigue property and fracture mechanism of weld joint

Surface modification and surface treatment
(Strength & Fracture of Materials Lab.)

Our group aim to improve both productivity/performance of materials by high grade surface cleaning (surface treatment), and function/performance of materials by coating new materials with superior properties which can't obtain bulk materials(surface modification). The following technologies are researched and developed in this process.


Surface treatment:

Scene of laser abrasion

Activated surface

By controlling the power density of irradiated pulse laser beam, laser cleaning can be performed without damage for high precision mold, also laser abrasion of strong oxide film and activation of the surface for many kinds of base material can be performed. These laser processes improve the reliability of manufacturing process and added value, and have the features low-emissions and no consumables for example water, acid, solvent and sand. Furthermore these laser processes can add new function to the surface that was laser cleaned.


Surface modification:


Example of nano-wires

Formation technique of nano-wires are being developed using a plasma discharging process. This technique can improve the delamination strength of coatings and heat / electrical properties of materials. If the film is coated on the nanowires, it is expected to significantly improve frictional / mechanical properties of materials.


Research themes
  • Non-contact and no damage cleaning for high precision mold and sensor
  • Simultaneous improvement of surface cleaning and characteristics
    (wetting, adhesive characteristics)
  • Formation of nanowires by plasma processing
  • Development of coatings with superior function
Facilities
  • Tm fiber-laser processing device
  • R.F. plasma discharging apparatus
  • Helicon sputtering apparatus

Metal forming
(Engineering Elasto-Plasticity Lab.)


Incremental sheet forming with local heating by laser irradiation. Forming apparatus, forming process and example of formed AZ31 sheet.
Outline

Metal forming group deals with metal forming technology and accurate numerical simulation of metal forming process for hard-to-form sheet metals such as advanced high strength steel sheets, magnesium alloy sheets or aluminum alloy sheets.

One of the main research subjects is “Incremental sheet forming with local heating by laser irradiation”. This is a novel flexible forming method for hard-to-form sheet metals, where sheet metal is incrementally formed by 3D-motion of simple forming tool while tool contact point of the sheet is dynamically and locally heated by laser irradiation. Since a specific die set is not necessary for this forming method, this technology would offer a great advantage in production of high-variety low-volume products.

Metal forming group also investigates several subjects as listed in the following “Trend of recent study” section to contribute to improvement of sheet metal forming technology and numerical simulation of metal forming process.

Trend of recent study
  • Incremental sheet forming with local heating by laser irradiation
  • Strain-path dependence and temperature dependence of forming limit of sheet metals and its prediction
  • Effect of stress relaxation on suppression of springback in warm forming
  • Material models for sheet metals at large plastic strain and its application to numerical simulation
Research Facilities
  • Incremental sheet forming system with local heating by laser irradiation
  • Warm/hot uniaxial tensile testing apparatus
  • Biaxial tension testing machine
  • Stretch forming apparatus
  • FEA software (LS-DYNA,Pam-Stamp,Marc,Simufact.forming)

Additive Manufacturing & Sintering
(Net Shape Manufacturing Lab.)

We are developing net-shape manufacturing technology for complex shaped parts which are difficult to be fabricated by conventional processes. To accomplish such target, namely, to get net-shaped high strength and high reliable ceramic/metallic parts, we combine “UV hardening resin 3D printer” and “high speed centrifugal compaction process of powders”, since these processes have high shape adaptability, accuracy. The products made by our technology have dense and flawless microstructures over one-process 3Dprinting, so that it can be adopted to critical safety parts. We also are developing microwave / plasma hybrid sintering and so on.

Resent researches

  • Development of clean diesel nossle tips by additive manufactureing (AM) & high-speed centrifugal compaction process (HCP)
  • On-demand all ceramic artificial teeth made by AM & HCP
  • Development of new processing technology under high temperature centrifuge
  • Sintering of metallic parts by microwave / plasma hybrid heating
Principal apparates:
  • UV hardening resin 3D printer
  • mills for powder (ball mill, turbular mill, planetary mill)
  • hydraulic press (6 t)
  • high-speed refrigerating centrifuge (10,000G)
  • vacuum / atmospheric furnaces (1800 K)
  • thermal analyzer (TG / DTA)
  • SEM
  • OM etc.

New material manufacturing process
(Materials Physics Lab.)
(Property Control of Materials Lab.)

Optimization of alloy composition, manufacturing process and microstructure will be the key technology for development of high performance and multi-functional materials.

Therefore, chemical composition control and microstructure control of materials for high performance of mechanical material are positively necessary for material`s upgrading and various purposes.

Material control is divided into machinery field in machine dynamic, thermal and material field in control of alloy, several phases and composite materials. However, these two fields are mutually related.

New material manufacturing process is being studied widely. For example, Modeling of transitional phenomenon for Materials optimization for machine structural use and functional materials, and development of measuring, control, new control process in material production process. Trend of the study will be as follows.

Trend of the study
  • By melting, solidification, sintering and solid phase transformation to achieve material control of metallic materials by multi-scale
  • Design and development of high performance, multi-functional materials by chemical composition and manufacturing process optimization
  • Development to processing and characteristic evaluation by various manufacturing process optimization
  • Material optimization of chemical composition, manufacturing, a series of study of characteristic evaluation and development
Main equipment
  • CCLM(Cold crucible levitation melting)
  • SPS(Spark plasms sintering )
  • LPI(Low pressure infiltration)

Amputating & Cutting process
(Machining and Machining System Lab.)

Clarifying the machining mechanism to propose the novel high-yield process for advanced materials

Our group propose and provide elemental techniques to achieve high added-value, high efficient and cost-reduced manufacturing, as well as reducing the environmental impact, for industries in Japan. The performance and durability of products depend highly on the level of manufacturing techniques to embody the design drawings. Therefore, we conduct researches concerning the machining mechanism and the precision and high-yield processes for a wide variety of methods such as cutting, grinding, abrasive process and laser machining. And research interests are not only for general-purpose materials such as carbon steels and aluminum alloys but also for the advanced materials such as electric device materials, biomaterials and aerospace materials. Especially, the development of composite process consisting of laser process paid attention to as newly processing technology and machining process is aggressively pushed forward.

Main research subject
  • The sensing technology and the components for machine tools
  • Machining for the difficult-to-cut materials
  • Development of the free-cutting steels and the new cutting tools
  • Laser assisted machining process
  • Laser processing of brittle materials
Main equipment
  • Parallel mechanism machining center(OKUMA PM600)
  • Ultraprecision lathe(TOSHIBA MACHINE ULC-100A)
© 2015 Hiroshima University. All rights reserved.