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R.D.K. Misra

Bio: R.D.K. Misra is an academic researcher from University of Texas at El Paso. The author has contributed to research in topics: Austenite & Martensite. The author has an hindex of 35, co-authored 338 publications receiving 5188 citations.

Papers published on a yearly basis

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Journal ArticleDOI
TL;DR: The results indicated that the underlying fatigue mechanism for the three kinds of meshes is the interaction of cyclic ratcheting and fatigue crack growth on the struts, which is closely related to cumulative effect of buckling and bending deformation of the strut.
Abstract: Additive manufacturing technique is a promising approach for fabricating cellular bone substitutes such as trabecular and cortical bones because of the ability to adjust process parameters to fabricate different shapes and inner structures. Considering the long term safe application in human body, the metallic cellular implants are expected to exhibit superior fatigue property. The objective of the study was to study the influence of cell shape on the compressive fatigue behavior of Ti-6Al-4V mesh arrays fabricated by electron beam melting. The results indicated that the underlying fatigue mechanism for the three kinds of meshes (cubic, G7 and rhombic dodecahedron) is the interaction of cyclic ratcheting and fatigue crack growth on the struts, which is closely related to cumulative effect of buckling and bending deformation of the strut. By increasing the buckling deformation on the struts through cell shape design, the cyclic ratcheting rate of the meshes during cyclic deformation was decreased and accordingly, the compressive fatigue strength was increased. With increasing bending deformation of struts, fatigue crack growth in struts contributed more to the fatigue damage of meshes. Rough surface and pores contained in the struts significantly deteriorated the compressive fatigue strength of the struts. By optimizing the buckling and bending deformation through cell shape design, Ti-6Al-4V alloy cellular solids with high fatigue strength and low modulus can be fabricated by the EBM technique.

181 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive study on the effect of cellular structure and melt pool boundary (MPB) condition on the mechanical properties, deformation and failure behavior of AlSi10Mg alloy processed by selective laser melting (SLM).
Abstract: We describe here a comprehensive study on the effect of cellular structure and melt pool boundary (MPB) condition on the mechanical properties, deformation and failure behavior of AlSi10Mg alloy processed by selective laser melting (SLM). The morphology of melt pool (MP) on the load bearing face of tensile samples was significantly different with build directions. It resulted in different mechanical properties of the samples with different build directions. Furthermore, the microstructure analysis revealed that the MP in the SLM AlSi10Mg alloy mainly consisted of columnar α-Al grains which were made of ultra-fine elongated cellular structure. Electron back-scatter diffraction (EBSD) analysis revealed that the long axis of cellular structure and columnar grains were parallel to , which resulted in fiber texture in SLM AlSi10Mg alloy. However, Schmid factor calculation demonstrated that the anisotropy of mechanical properties of the SLM AlSi10Mg alloy built with different direction was mainly dependent on the distribution of MPB on the load bearing face, and not texture. The defects including pores, residual stress and heat affected zone (HAZ) located at MPB made it the weakest part in the SLM AlSi10Mg. The sample built along horizontal direction exhibited good combination of strength and plasticity and is attributed to the lowest fraction of MPBs that withstand load during tensile. MPB had strong influence on the mechanical properties and failure behavior of SLM AlSi10Mg built with different directions.

179 citations

Journal ArticleDOI
TL;DR: In this article, two different morphologies of martensite in dual phase (DP) steel were obtained using two different processing routes: intermediate quenching and inter-critical annealing.
Abstract: Two different morphologies of martensite in dual phase (DP) steel were obtained using two different processing routes. In one case, intermediate quenching (IQ) was adapted, where DP steel was water-quenched to obtain martensite phase, followed by inter-critical annealing. In the second case, the steel was cold rolled, followed by inter-critical annealing (CR-IA). For IQ and CR-IA steels, the inter-critical temperatures varied from 750 °C to 850 °C to obtain different volume fractions of martensite. An understanding of structure–property was obtained using a combination of scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile tests. It was observed that fibrous martensite presented in IQ samples, gradually transformed to blocky martensite with increase in inter-critical temperature, resembling the CR-IA steels. The fibrous martensite encouraged martensite cracking, however, the martensite cracking was dramatically decreased in the IQ samples with increase in martensite fraction. The strain hardening behavior studied using the differential C – J model indicated multistage depending on the fraction of martensite. The low volume fraction of martensite in the DP steel provided high ductility–toughness combination and improved strain hardening ability due to the presence of soft ferrite phase in DP steel. Fibrous martensite in DP steel resulted in less strain hardening than blocky martensite, prior to exceeding a threshold volume fraction. The threshold value was significantly smaller for DP steel with blocky martensite.

165 citations

Journal ArticleDOI
TL;DR: Interestingly, osteoblasts cultured within hydrogel using bone morphogenetic protein (BMP)-2 demonstrated the capability for encapsulation of cells and induced cell differentiation, and the nanocrystalline cellulose significant impacted degradation and interaction between hydrogels and cells.

160 citations

Journal ArticleDOI
TL;DR: In this article, the effect of prior austenite grain size on martensite-austenite (M-A) constituent during the second pass reheating and its consequent influence on impact toughness was investigated.
Abstract: Structure–mechanical property relationship studies were carried out on Gleeble simulated intercritically reheated coarse-grained heat affected zone (ICCGHAZ) of 700 MPa linepipe steel microalloyed with Nb. The design of experiments was aimed at varying reheat temperature in the first pass to obtain different coarse grain size in the HAZ. This enabled the study of the effect of prior austenite grain size on martensite–austenite (M–A) constituent during the second pass reheating and its consequent influence on impact toughness. We elucidate here the role of phase transformation and the fraction, size, shape, distribution, and carbon content of M–A constituent on impact toughness. The data suggests that the fraction of M–A constituent is not influenced by grain size, but the size of M–A constituent is influenced by the prior austenite grain size, which consequently governs toughness. Coarse austenite grain size increases the size of M–A constituent and lowers the HAZ toughness. Coarse austenite grain associated with coarse M–A constituent along grain boundary is the dominant factor in promoting brittle fracture. The combination of fine prior austenite grain size and smaller M–A constituent is favorable in obtaining high toughness. Good toughness is obtained on refining the prior austenite grain size in the CGHAZ during first pass and hence ICCGHAZ in the second pass.

142 citations


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Reference EntryDOI
31 Oct 2001
TL;DR: The American Society for Testing and Materials (ASTM) as mentioned in this paper is an independent organization devoted to the development of standards for testing and materials, and is a member of IEEE 802.11.
Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

3,792 citations

01 Jun 2005

3,154 citations

Journal ArticleDOI
TL;DR: A review of the field of hydrogels and aerogels incorporating nanocelluloses can be found in this paper, where over 200 references are summarized in comprehensive tables and a discussion of the challenges and benefits of using CNCs and CNFs as reinforcing agents in conventional plastics is presented.
Abstract: Naturally derived cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) are emerging nanomaterials that display high strength, high surface area, and tunable surface chemistry, allowing for controlled interactions with polymers, nanoparticles, small molecules, and biological materials. Industrial production of nanocelluloses is increasing rapidly with several companies already producing on the tons-per-day scale, intensifying the quest for viable products across many sectors. While the hydrophilicity of the nanocellulose interface has posed a challenge to the use of CNCs and CNFs as reinforcing agents in conventional plastics, it is a significant benefit for creating reinforced or structured hydrogel composites (or, when dried, aerogels) exhibiting both mechanical reinforcement and a host of other desirable properties. In this context, this Review describes the quickly growing field of hydrogels and aerogels incorporating nanocelluloses; over 200 references are summarized in comprehensive tables ...

952 citations