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  • Open Access


    Shear Localization in Polycrystalline Metal at High-Strain Rates with Dynamic Recrystallization: Crystal Plasticity Modeling and Texture Effect

    Qilin Xiong1,2,*, Wen An1,2, Chuanzhi Liu1,2

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.25, No.3, pp. 1-1, 2023, DOI:10.32604/icces.2023.010044

    Abstract Shear localization is an important failure mode, or even the dominant mode in metals at high-strain rates. However, it is a great challenge to accurately predict the occurrence and evolution of shear localization in metals at the high-strain rate deformation. Here, a dislocation-based crystal plasticity constitutive model with a crucial mechanism of shear instability, namely dynamic recrystallization, was developed. The evolution equations of dislocation density and grain size in the process of dynamic recrystallization were proposed and incorporated into the new constitutive model. The threshold of the stored energy in crystals was used as the criterion for the occurrence of… More >

  • Open Access


    Influence of the Processing Parameters on the Electrospinning of Biopolymeric Fibers

    Alicia Mujica-Garcia1,2, Iván Navarro-Baena1, José Maria Kenny1,2, Laura Peponi2,*

    Journal of Renewable Materials, Vol.2, No.1, pp. 23-34, 2014, DOI:10.7569/JRM.2013.634130

    Abstract The main aim of this research is the production of different biopolymeric fi bers by electrospinning and the determination of the optimum working parameters for each polymer analyzed. In particular, three different biopolymers have been studied: poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL) and a synthesized poly(ester-urethane) based on a synthesized PLA-b-PCL-b-PLA tri-block copolymer. This research is focused on the analysis of the infl uence of the processing parameters, such as the concentration and fl ow-rate of the polymer solution and the applied voltage, as well as the physico-chemical properties of the polymers used, on the fi ber formation and crystallization behavior.… More >

  • Open Access


    Optimization Design of an Embedded Multi-Cell Thin-Walled Energy Absorption Structures with Local Surface Nanocrystallization

    Kang Xu, Tong Li, Gaofei Guan, Jianlong Qu, Zhen Zhao, Xinsheng Xu*

    CMES-Computer Modeling in Engineering & Sciences, Vol.130, No.2, pp. 987-1002, 2022, DOI:10.32604/cmes.2022.018128

    Abstract By means of the local surface nanocrystallization that enables to change the material on local positions, an innovative embedded multi-cell (EMC) thin-walled energy absorption structures with local surface nanocrystallization is proposed in this paper. The local surface nanacrystallization stripes are regarded as the moving morphable components in the domain for optimal design. Results reveal that after optimizing the local surface nanocrystallization layout, the specific energy absorption (SEA) is increased by 50.78% compared with the untreated counterpart. Besides, in contrast with the optimized 4-cell structure, the SEA of the nanocrystallized embedded 9-cell structure is further enhanced by 27.68%, in contrast with… More >

  • Open Access


    Crystallization and Dynamic Mechanical Behavior of Coir Fiber Reinforced Poly(Butylene Succinate) Biocomposites

    Xu Yan1, Changheng Liu2, Liang Qiao1, Kaili Zhu2, Hongsheng Tan1,*, Shuhua Dong1, Zhitao Lin1

    Journal of Renewable Materials, Vol.10, No.4, pp. 1039-1048, 2022, DOI:10.32604/jrm.2022.017239

    Abstract The crystallization behavior, crystal morphology and form, and viscoelastic behavior of poly(butylene succinate) (PBS) and coir fiber/PBS composites (CPB) were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), X-ray diffraction (XRD) and dynamic mechanical analysis (DMA). The results of DSC measurement show that the crystallization temperature increases with the filling of coir fibers. POM images reveal that the spherulitic size and crystallization behavior of PBS are influenced by the coir fibers in the composites. XRD curves show that the crystal form of pure PBS and CPB are remaining almost identical. In addition, the storage modulus of CPB significantly… More >

  • Open Access

    Examination of a Biobased Carbon Nucleating Agent on Poly(lactic acid) Crystallization

    Michael R. Snowdon1,2, Amar K. Mohanty1,2, Manjusri Misra1,2*

    Journal of Renewable Materials, Vol.5, Suppl.1, pp. 94-105, 2017, DOI:10.7569/JRM.2017.634134

    Abstract This article assesses the performance of a biobased carbon as a nucleator using common techniques to stimulate poly(lactic acid) crystallization and enhance the thermal stability of PLA during injection molding. The combination of a biodegradable plasticizer, poly(ethylene glycol) (PEG), along with biobased carbon-rich pyrolyzed biomass char residue and an industrially available microcrystalline talc, were tested for nucleating agent capabilities at additions of 10 wt%. Differential scanning calorimetry (DSC) data demonstrated that the inclusion of the plasticizer could increase the PLA crystalline content with further improvements when nucleating agent was present. With a higher mold temperature, the PLA crystallinity surpassed 40%… More >

  • Open Access


    Assessment of Severe Shot Peening on Surface Characteristics of Al Alloys

    M. Guagliano1,2, S. Bagherifard2, I. Fernandez Parienete3, R. Ghelichi2

    Structural Durability & Health Monitoring, Vol.6, No.1, pp. 31-42, 2010, DOI:10.3970/sdhm.2010.006.031

    Abstract Surface grain refinement is a relatively new process aimed to enhance mechanical material properties. In this study Al7075-T6 bars have been shot peened with parameters (shot speed and treatment duration) much stronger from those of conventional shot peening (SP). Residual stress state and microstructure gradient have been observed by means of transmission electron microscopy (TEM), X-ray diffraction (XRD) and nano indentation tester. Formation of a fine grained layer of material on top surface of the specimens was confirmed by TEM and also XRD measurements. XRD results show significant depth affected both in terms of residual stress and full width half… More >

  • Open Access


    Enhanced surface mechanical properties of structural steels by a surface nano-crystallization based duplex treatment processing

    T. Fu, C.P. Wang, B. Hou, X.D. Zhu, Z.F. Zhou, K.Y. Li, J. Lu

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.20, No.3, pp. 91-92, 2011, DOI:10.3970/icces.2011.020.091

    Abstract Structural steels are widely used in engineering fields. Generally, they have the advantage of lower prices due to less precious alloy elements contained; however, their properties, especially the surface properties are inferior to high alloy steels. Surface engineering are of importance in improving surface properties of steels, and even a 'new' surface layer with high performances can be produced by surface technologies on low cost structural steels with ordinary properties.
    The researches of last decade have shown that surface nanocrystallization (SNC) can markedly improve surface mechanical properties of metallic materials and accelerate thermal diffusion of N, Cr, etc atoms. In… More >

  • Open Access


    Molecular-dynamics Study on Crack Growth Behavior Relevant to Crystal Nucleation in Amorphous Metal

    R. Matsumoto1, M. Nakagaki1, A. Nakatani2, H. Kitagawa3

    CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.1, pp. 75-84, 2005, DOI:10.3970/cmes.2005.009.075

    Abstract In this paper, the internal structure-changes around the crack-tip and the pertinent crack growth behavior in an amorphous metal were studied by a molecular dynamics (MD) simulation. In order to perform a large scale calculation, the domain decomposition method was used for parallel calculation. The Finnis-Sinclair potential for$\alpha$-iron was used to describe the interatomic potential. Computed results show that nano-scaled crystalline phase grows around the crack-tip. The distribution of deformation zones and deformation mechanism are significantly altered. While grains are relatively small, they are not deformed, and the most amorphous-crystal interfaces have a large strain for phase transition. The emission… More >

  • Open Access


    PHBV Crystallization under Injection Molding Conditions: Influence of Packing Pressure and Mold Temperature

    G. El hajj Sleiman1, G. Colomines1, R. Deterre1, I. Petit1, E. Leroy2, S. Belhabib1,*

    Journal of Renewable Materials, Vol.6, No.3, pp. 270-276, 2018, DOI:10.7569/JRM.2017.634179

    Abstract Poly(3-hydroxy butyrate)-co-(3-hydroxy valerate) (PHBV) is a biobased and biodegradable polyester. This semicrystalline bioplastic could be a good candidate for the replacement of some commodity plastics derived from oil. However, the control of the conditions of its processing in order to obtain optimal properties of the finished products remains a current research subject. The objective of this work is to better understand the crystallization under injection molding conditions by inline measurements during the process. We focused on the influence of two key processing parameters, namely, mold temperature and packing pressure. The modeling of inline temperature measurements allowed an inverse estimation of… More >

  • Open Access


    Cellulose Nanocrystals versus Polyethylene Glycol as Toughening Agents for Poly(Lactic Acid)-Poly(Acrylic Acid) Graft Copolymer

    Jose Luis Orellana, Michael Mauhar, Christopher L. Kitchens*

    Journal of Renewable Materials, Vol.4, No.5, pp. 340-350, 2016, DOI:10.7569/JRM.2016.634126

    Abstract Polylactic acid (PLA) is one of the most widely used biodegradable polymers due to the ability to synthesize it economically at industrial scale and its favorable properties for many consumer products. However, the rigid nature of PLA is not desirable for specific applications, requiring the incorporation of effective bioderived additives in order to enhance the PLA toughness and broaden applications. In this work, PLA was modified by graft polymerization of polyacrylic acid (PLA-g-PAA) to increase the hydrophilicity to promote compatibilization of cellulose nanocrystals (CNCs) or high molecular polyethylene glycol (PEG). CNCs were found to act as a nucleating agent for… More >

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