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Welding and Joining Functional Design Lab [Joining and Welding Research Institute]
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The lab explains how welding and joining work by studying the microstructure of materials.
AboutAbout the lab
Explaining how welding and joining work through materials science
The Welding and Joining Functional Design Lab studies what determines the functions and mechanical properties of joints formed by fusion welding and by liquid-phase and solid-state joining.
The lab examines the microstructure of joints using electron microscopy and X-ray diffraction, and carries out modeling and simulation based on the results.
Its goals are to build the foundations of materials design for producing defect-free joints with excellent functionality, to develop new joining methods, and to evaluate the properties of joined structures.
On the website of the Joining and Welding Research Institute, the lab is introduced under the name "Welding Mechanism Field."
Key terms
- Microstructure
- The arrangement of crystals and phases inside a material, visible under a microscope.
- Friction stir processing (FSP)
- A method that presses a rotating tool against a material and modifies the area near the surface through frictional heat and stirring.
- Fatigue strength
- The strength to withstand repeated loading without breaking.
ResearchResearch themes
The lab examines the microstructure of joints formed by welding and joining, and aims to clarify, from a materials science perspective, the mechanisms that determine their functions and mechanical properties. Research themes include microstructural analysis of welds in structural materials such as steel, elucidating the mechanisms of dissimilar-material joining, and creating functional materials by using welding and joining phenomena.
*Illustrative imageElucidating the phenomenon that improves penetration shape
In tandem pulsed GMAW welding, vibrating the base metal sinusoidally at 250 Hz improves the penetration shape to a pan-bottom shape. The lab reproduces this phenomenon with the thermal fluid analysis software Flow-3D and elucidates its mechanism.
*Illustrative imageImproving the fatigue strength of steel welded joints
The lab investigates how friction stir processing (FSP) with a spherical WC tool improves the fatigue strength of steel welded joints. In addition to improved weld toe geometry, it identifies solid-solution hardening from tool constituent elements dissolving into the steel and the introduction of compressive residual stress.
*Illustrative imageFatigue strength of ultra-high-strength steel welded joints
For lap fillet welded joints of 1.2 GPa-class cold-rolled ultra-high-strength steel, the lab raises fatigue strength with a welding technique that increases the Cr concentration of the welding wire to harden the weld reinforcement and give it a flat, wide shape. Under the same welding conditions, the fatigue life with 15Cr is 10 times that with 1Cr.
*Illustrative imageResidual stress and hardness of the steel surface layer after FSP
Using FSP with a WC tool, the lab investigates how residual stress, hardness, and retained austenite (γ) in the steel surface layer relate to the change in Ms temperature caused by the amount of tool constituent elements in solid solution. It reports that when the dissolved amount increases and the Ms temperature reaches 150°C, the residual stress becomes compressive.
MembersFaculty
- ProfessorKazuhiro Ito
- Lecturer (Concurrent Appointment)Makoto Takahashi
- Project LecturerBingbing ZHAO
- Assistant ProfessorHONG SEONG MIN
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Report an errorAbout the images
The top and research theme images are illustrative and were not taken at the lab. They are cropped from Wikimedia Commons images. Cropped CC BY-SA images are provided under the same CC BY-SA license as the original (version shown on each line).
- Top image: “Shielded Metal Arc Welding” Weldscientist / CC BY-SA 4.0 (cropped)
- Elucidating the phenomenon that improves penetration shape: “Migpipe” Weldscientist / CC BY-SA 4.0 (cropped)
- Improving the fatigue strength of steel welded joints: “Advanced friction stir welding and processing tools by MegaStir” NearEMPTiness / CC BY-SA 4.0 (cropped)
- Fatigue strength of ultra-high-strength steel welded joints: “Parts of a fillet weld” Powerstroker / CC BY-SA 3.0 (cropped)
- Residual stress and hardness of the steel surface layer after FSP: “X-ray test of friction-stir welded tank ESA373005” European Space Agency / CC BY-SA 3.0 igo (cropped)
- Related lab (Materials Informatics Lab): “Microstructure-for-the-annealed-Ti-15-3-3-3-sample” K. V. Sudhakar, Ethan Wood / CC BY 4.0 (cropped)
- Related lab (Joining Interface Mechanisms Lab [Joining and Welding Research Institute]): “Friction stir welding data monitoring at NASA MSFC (Marshall Space Flight Center) in a video by NASA-MSFC 05” NASA/MSFC / Public domain (cropped)
- Related lab (Process Mechanics Lab): “Ultrasonic Welding” NearEMPTiness / CC BY-SA 3.0 (cropped)
- Related lab (Materials Ultrafine Process Engineering Lab): “Transmission electron microscopy (TEM)” Database Center for Life Science (DBCLS) / CC BY 3.0 (cropped)
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