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Post-Processing of Laser Additive Manufactured Inconel 718 Using Laser Shock Peening
A. N. Jinoop,S. Kanmani Subbu,C. P. Paul,I. A. Palani 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.9
The components built using new generation feature based design and manufacturing process, called laser additive manufacturing (LAM) is inherited with tensile residual stress due to rapid heating and cooling during material processing. Laser shock peening (LSP) is an advanced surface engineering process that imparts beneficial compressive residual stresses into materials yielding longer product life by increasing the resistance to many surface-related failures, such as wear. LSP is widely used by various industries including aerospace, power generation, chemical processing, etc. to increase the life of engineering components. This paper reports LSP of LAM built Inconel 718 and the parametric study is conducted by varying peak laser power and number of shots at three different levels. Optimum laser power and number of shots derived using grey relational analysis is found to be 170 mW and 7, respectively for maximum hardness and minimum depth of profile. The investigation show that LSP changed the surface morphology and mechanical properties of the LAM built structure. The surface investigation using optical profilometer and Vickers micro-hardness shows a maximum profile depth of 10 μm and hardness of 360 HV. Residual stress measurement indicates compressive residual stress of 214.9–307.9 MPa on the LAM sample surface after LSP. The wear studies show an improvement by a factor of 1.70 for LSP treated LAM samples as compared to that of as-built condition. This study unwrap avenues for using LSP as property enhancement post-processing technique LAM fabricated structures with geometrical complexities.
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R. Seetharam,Pagidi Madhukar,G. Yoganjaneyulu,S. Kanmani Subbu,M. J. Davidson 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4
Mathematical models are among the new approaches employed to predict the properties of any material under various conditions. Mathematical models are essential for not only understanding the material properties but also estimating the costof design, product life, and failure criteria of the product. Therefore, in the current investigation, the hot deformation (HD)behaviour and microstructure alteration of deformed AA7150-5 wt% B4Ccomposite was studied through a mathematicalmodel. The new AA7150-5 wt% B4C composite was fabricated through an ultrasonic-probe assisted (20 KHz, 1000 W)stir casting process. The hot compression test was performed on a hydraulic press for various deformation temperatures(623–773 K) and strain rates (0.01–1 s−1). Based on the outcome, it is inferred that the flow stresses and microstructuresof AA7150-5 wt% B4Ccomposite was significantly altered during the hot compression test under various deformationconditions. The constitutive and dynamically recrystallized grain (DRXed) models were developed as a function of variousdeformation conditions of deformed AA7150-5 wt% B4Ccomposite, which was then applied to forecast the flow stress andgrain size behaviour for different deformation conditions. The flow stress and DRXed grain size were obtained through theproposed constitutive and DRXed models are correlated with experimental results, with excellent accuracy. The modelsdeveloped are reliable to predict the AA7150-5 wt% B4Cproperties for various conditions.
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VAULT PROTEIN-TEMPLATED ASSEMBLIES OF NANOPARTICLES
XIAO-YING QI,XIAO HUANG,HAI LI,YUSONG WANG,Yun Xia,MEENUBHARATHI NATARAJAN,JUN WEI,Subbu S. Venkatraman,HUA ZHANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.1
Recombinant vault nanoparticles are used as stable nanoscale platforms for controlled self-assembly of various kinds of nanoparticles into the predefined multidimensional architectures. High-yield and uniform discoidal assemblies templated by vaults are constructed from gold nanospheres and quantum dots, while dimeric assemblies are formed from relatively-large gold nanocubes. The vault-templated approach appears to be mainly mediated by the surface and dimensional properties of nanoparticles while less affected by the chemical composition of nanoparticles, making it a universal strategy for fabrication of nanoassemblies with designed properties for potential applications.
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Boon Chin Heng,Yun Xia,Xiaobo Shang,Peter Rainer Preiser,S. K. Alex Law,Freddy Yin-Chiang Boey,Subbu S. Venkatraman 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.1
Endothelial cell coverage of blood-contacting devices is crucial to their eventual success in the clinic. Two established human cell lines derived from HUVEC (human umbilical vascular endothelial cells), CRL 2922and CRL 2873, have been widely utilized to study and model endothelial cell biology. However, it is not clear if these two cell lines would be useful for modeling primary endothelial cell interaction with newly-formulated biomaterials in tissue engineering applications. Hence, this study was conducted to compare the adhesion and proliferation characteristics of HUVEC grown on seven different substrata, tissue culture polystyrene (TCPS), gelatin,chitosan, poly-L-lysine, hyaluronan, poly-L-lactic acid (PLLA), and polylactic-co-glycolic acid (PLGA). The short-term adhesive behavior (2 h) of HUVEC on the various substrata was not closely-replicated by either CRL 2873 or CRL 2922. This was likely because the 2 h timeframe is too short for identification of differences in the interaction among the three cell types grown on various substrata. There was much faster proliferation of CRL 2922 on all seven substrata when compared to HUVEC and CRL 2873. Moreover, the proliferation rates of CRL 2922 on the various substrata showed little variation. In contrast, HUVEC and CRL 2873 displayed similar trends in proliferation rates, with gelatin and TCPS yielding the highest rates, and PLLA and PLGA yielding the lowest rates. Hence, CRL 2873 is better suited for modeling primary endothelial cell interaction with newly-formulated biomaterials than CRL 2922. The advantage of using CRL 2873 over HUVEC for biomaterial screening is that it is immortalized and displays much less inter-batch variability than primary culture.
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