Wongsangam, Jittraporn

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Wongsangam, Jittraporn
Alternative Name
Wongsa-Ngam, Jittraporn
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Email
jittraporn.wo@kmitl.ac.th

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    Advances in Superplasticity from a Laboratory Curiosity to the Development of a Superplastic Forming Industry
    (2022-11-01)
    Wongsa-Ngam, Jittraporn
    ;
    Langdon, Terence G.
    Superplasticity refers to the ability of some materials to pull out to tensile elongations of 400% or more when the strain rate sensitivity is ~0.5. The first report of true superplastic flow was published in 1934 in experiments conducted in England. However, this remarkable result attracted little interest among western scientific researchers and the result remained a laboratory curiosity for many years. Later, following extensive research on superplasticity in the Soviet Union, interest developed in the west, and superplasticity became a topic of extensive scientific research. This research was further enhanced with the demonstration that the application of severe plastic deformation provided an opportunity for achieving grain refinement to the submicrometer or even the nanometer level, and these small grains were especially attractive for achieving good superplastic properties. It is now recognized that superplastic alloys provide an excellent forming capability, especially in making high quality curved parts that are not easily fabricated using more conventional processes. This has led to the development of a large superplastic forming industry that currently processes many thousands of tons of sheet metals. This report traces these developments with an emphasis on the scientific principles behind the occurrence of superplastic flow.
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    The influence of HPT on microstructure and wear resistance of Al-7wt%Si-2wt%Fe Alloy
    (2021-01-01)
    Wongsa-Ngam, Jittraporn
    ;
    Xu, Jie
    ;
    Phongphisutthinan, Chakkrist
    ;
    Langdon, Terence G.
    An aluminum silicon-based alloy (Al-7wt%Si-2wt%Fe) was subjected to severe plastic deformation by the high-pressure torsion (HPT) method. This HPT processing was conducted at room temperature up to five revolutions under a pressure of 6.0 GPa and rotation speed of 1.0 rpm. Observations of microstructure evolution, especially intermetallic phases, was carried out by an optical microscope (OM) and a scanning electron microscope (SEM). It was found that the ironintermetallic particles decreased in size with numbers of turns. This is due to the large strain introduced during HPT processing which produced a degree of fragmentation of intermetallic phases which increased with the imposed strain. In addition, wear behaviors of the as-cast and samples deformed by HPT were also investigated using micro-tribometer UMT-2 (CETR Co., USA) following the ASTM G99-05 (2010) standard. The friction coefficient and wear volume loss were measured to evaluate the effect of imposed strain during HPT processing on wear resistance. It was found that the values of the average friction coefficient were slightly lower in deformed samples and the wear volume loss decreased with increasing numbers of turns.
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    A study of die parameters influencing the plastic deformation for 3D finite element simulations of equal-channel angular pressing
    (2025-08-01)
    Wongsa-Ngam, Jittraporn
    ;
    Noraphaipaksa, Nitikorn
    ;
    Kanchanomi, Chaosuan
    ;
    Langdon, Terence G.
    Equal-channel angular pressing is an effective method of severe plastic deformation that is employed to produce materials with ultrafine grain structures. This study aimed to systematically investigate the influence of the die parameters, specifically the channel angle and the outer curvature angle, on the induced plastic strain, strain inhomogeneity and the reaction force during processing of a round section copper-zirconium alloy workpiece. Three-dimensional finite element simulations were developed using ABAQUS/ Explicit to model single-pass deformation with varying channel angles of 90°, 110°, 120° and 150° and outer curvature angles of 20°, 30° and 60°. The results demonstrate that the channel angle is the dominant factor controlling the average equivalent plastic strain, which decreased from approximately 1.04 at 90° channel angle with 20° outer curvature angle to about 0.31 at 150° channel angle regardless of the outer curvature. In contrast, the outer curvature angle significantly influences the strain homogeneity at low channel angles, with the coefficient of variance increasing from 0.06 to 0.22 when the outer curvature angle increases from 20° to 60° at a 90° channel angle. Additionally, the maximum reaction force declined markedly with an increasing channel angle, dropping from 58 kN at 90° to 12 kN at 150°, thereby highlighting a strong interplay between imposed strain and forming load. These findings provide clear guidelines for optimizing the die design to balance high strain, uniform deformation and manageable pressing forces in the industrial processing of ultrafine-grained materials.
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    Numerical investigation of plastic strain homogeneity during equal-channel angular pressing of a Cu-Zr Alloy
    (2021-12-01)
    Wongsa-Ngam, Jittraporn
    ;
    Noraphaiphipaksa, Nitikorn
    ;
    Kanchanomai, Chaosuan
    ;
    Langdon, Terence G.
    A three-dimensional finite element method (3D FEM) simulation was carried out using ABAQUS/Explicit software to simulate multi-pass processing by equal-channel angular pressing (ECAP) of a circular cross-sectional workpiece of a Cu-Zr alloy. The effective plastic strain distri-bution, the strain homogeneity and the occurrence of a steady-state zone in the workpiece were investigated during ECAP processing for up to eight passes. The simulation results show that a strain inhomogeneity was developed in ECAP after one pass due to the formation of a corner gap in the outer corner of the die. The calculations show that the average effective plastic strain and the degree of homogeneity both increase with the number of ECAP passes. Based on the coefficient of variance, a steady-state zone was identified in the middle section of the ECAP workpiece, and this was numerically evaluated as extending over a length of approximately 40 mm along the longitudinal axis for the Cu-Zr alloy.