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272 results on '"Woo, Wanchuck"'

9. Effect of interlayers and scanning strategies on through-thickness residual stress distributions in additive manufactured ferritic-austenitic steel structure

Author

Woo, Wanchuck, Kim, Dong-Kyu, Kingston, Ed J, Luzin, Vladmir, Salvemini, Floriana, and Hill, Michael R

Subjects
Directed energy deposition, Functionally graded material, Residual stress, Neutron diffraction, Deep hole drilling, Neutron tomography, Manufacturing Engineering, Materials Engineering, Mechanical Engineering, Materials
Abstract

A total of five different types of specimens were additively manufactured by directed energy deposition (DED) process. The specimens have a functionally graded material (FGM) structure, which has been deposited with variation of chemical composition of ferritic and austenitic steel powders in each interlayer on a steel substrate. Residual stress distributions were experimentally measured through the thickness of the specimens by the contour method, neutron diffraction, and deep/incremental center hole drilling. Neutron diffraction provided three orthogonal stress components in each FGM part and the results were compared to the two-dimensional stress map obtained by the contour method and confirmed its criticalities from the highly spatial resolved depth profile by the hole drilling method. Significant variations from tension to compression (up to 950 MPa) in the sine-wave stress profile were alleviated to about 430 MPa when the FGM were deposited with orthogonal or island DED scanning strategies with interlayers. Gradual changes (16.3–12.1 × 10−6/°C) of the thermal expansion coefficient were measured among the inserted DED FGM parts and grain structure with defects along the interface was three dimensionally examined by neutron tomography.

Published
2019

17. Two-dimensional mapping of residual stresses in a thick dissimilar weld using contour method, deep hole drilling, and neutron diffraction

Author

Woo, Wanchuck, An, Gyu Baek, Truman, Christopher E, Jiang, Wenchun, and Hill, Michael R

Subjects
Chemical Sciences, Engineering, Materials
Abstract

Residual stress variations were determined through the thickness of a 70-mm-thick ferritic–austenitic dissimilar steel weld using contour method, deep hole drilling, and neutron diffraction. The result shows that significant tensile stresses were distributed distinctly along the interface between ferritic and austenitic phases. The band of the large tensile stresses was about 8 mm wide and the magnitude reached 400 MPa, which is approaching 100 % of the yield strength of the base metal, near the top surface (about 15 % of the depth). It is attributed to the large difference (5.8 × 10−6 1/°C) of the thermal expansion coefficient between ferritic and austenitic steels of the interface. The microstructure analysis elucidates that the martensitic phase prevailed near the interface and results in microhardness increases.

Published
2016

49. Comparison of Brazed Residual Stress and Thermal Deformation between X-Type and Pyramidal Lattice Truss Sandwich Structure: Neutron Diffraction Measurement and Simulation Study

Author

Jiang Wenchun, Wei Zhiquan, Luo Yun, Zhang Weiya, and Woo Wanchuck

Subjects
lattice truss sandwich structure, brazed residual stress, deformation, 81.20.vj joining, welding, 47.11.fg finite element methods, Technology, Chemical technology, TP1-1185, Chemicals: Manufacture, use, etc., TP200-248
Abstract

This paper uses finite element method and neutron diffraction measurement to study the residual stress in lattice truss sandwich structure. A comparison of residual stress and thermal deformation between X-type and pyramidal lattice truss sandwich structure has been carried out. The residual stresses are concentrated in the middle joint and then decreases gradually to both the ends. The residual stresses in the X-type lattice truss sandwich structure are smaller than those in pyramidal structure. The maximum longitudinal and transverse stresses of pyramidal structure are 220 and 202 MPa, respectively, but they decrease to 190 and 145 MPa for X-type lattice truss sandwich structure, respectively. The thermal deformation for lattice truss sandwich panel structure is of wave shape. The X-type has a better resistance to thermal deformation than pyramidal lattice truss sandwich structure. The maximum wave deformation of pyramidal structure (0.02 mm) is about twice as that of X-type (0.01 mm) at the same brazing condition.

Published
2016
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