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Nan Song - One of the best experts on this subject based on the ideXlab platform.
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constitutive modeling and the effects of Strain rate and temperature on the formability of ti 6al 4v alloy sheet
Materials & Design, 2014Co-Authors: Guiqiang Guo, Junjie Xiao, Nan SongAbstract:Abstract The constitutive model considering the Strain-rate and temperature effects was presented by fitting the true stress–Strain curves of Ti–6Al–4V alloy over a wide range of Strain-rates (0.0005–0.05 s −1 ) and temperatures (923–1023 K). The Forming Limit Curve (FLC) of Ti–6Al–4V alloy at 973 K was measured by conducting the hemispherical dome test with specimens of different widths. The forming limit prediction model of Ti–6Al–4V alloy, which takes Strain-rate and temperature sensitivity into account, was predicted based on Marciniak and Kuczynski (M–K) theory along with Von Mises yield criterion. The comparison shows that the limit Strain decreases with temperature lowering but Strain-rate increasing. The comparison between theoretical analysis and experiment of FLC verifies the accuracy and reliability of the proposed methodology, which considers the Strain-rate and temperature effects, to predict limit Strains in the positive Minor Strain region of Forming Limit Diagram (FLD).
Guiqiang Guo - One of the best experts on this subject based on the ideXlab platform.
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constitutive modeling and the effects of Strain rate and temperature on the formability of ti 6al 4v alloy sheet
Materials & Design, 2014Co-Authors: Guiqiang Guo, Junjie Xiao, Nan SongAbstract:Abstract The constitutive model considering the Strain-rate and temperature effects was presented by fitting the true stress–Strain curves of Ti–6Al–4V alloy over a wide range of Strain-rates (0.0005–0.05 s −1 ) and temperatures (923–1023 K). The Forming Limit Curve (FLC) of Ti–6Al–4V alloy at 973 K was measured by conducting the hemispherical dome test with specimens of different widths. The forming limit prediction model of Ti–6Al–4V alloy, which takes Strain-rate and temperature sensitivity into account, was predicted based on Marciniak and Kuczynski (M–K) theory along with Von Mises yield criterion. The comparison shows that the limit Strain decreases with temperature lowering but Strain-rate increasing. The comparison between theoretical analysis and experiment of FLC verifies the accuracy and reliability of the proposed methodology, which considers the Strain-rate and temperature effects, to predict limit Strains in the positive Minor Strain region of Forming Limit Diagram (FLD).
Junjie Xiao - One of the best experts on this subject based on the ideXlab platform.
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constitutive modeling and the effects of Strain rate and temperature on the formability of ti 6al 4v alloy sheet
Materials & Design, 2014Co-Authors: Guiqiang Guo, Junjie Xiao, Nan SongAbstract:Abstract The constitutive model considering the Strain-rate and temperature effects was presented by fitting the true stress–Strain curves of Ti–6Al–4V alloy over a wide range of Strain-rates (0.0005–0.05 s −1 ) and temperatures (923–1023 K). The Forming Limit Curve (FLC) of Ti–6Al–4V alloy at 973 K was measured by conducting the hemispherical dome test with specimens of different widths. The forming limit prediction model of Ti–6Al–4V alloy, which takes Strain-rate and temperature sensitivity into account, was predicted based on Marciniak and Kuczynski (M–K) theory along with Von Mises yield criterion. The comparison shows that the limit Strain decreases with temperature lowering but Strain-rate increasing. The comparison between theoretical analysis and experiment of FLC verifies the accuracy and reliability of the proposed methodology, which considers the Strain-rate and temperature effects, to predict limit Strains in the positive Minor Strain region of Forming Limit Diagram (FLD).
G P Riley - One of the best experts on this subject based on the ideXlab platform.
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tendinopathy from basic science to treatment
Nature Reviews Rheumatology, 2008Co-Authors: G P RileyAbstract:Chronic tendon pathology (tendinopathy), although common, is difficult to treat. Tendons possess a highly organized fibrillar matrix, consisting of type I collagen and various 'Minor' collagens, proteoglycans and glycoproteins. The tendon matrix is maintained by the resident tenocytes, and there is evidence of a continuous process of matrix remodeling, although the rate of turnover varies at different sites. A change in remodeling activity is associated with the onset of tendinopathy. Major molecular changes include increased expression of type III collagen, fibronectin, tenascin C, aggrecan and biglycan. These changes are consistent with repair, but they might also be an adaptive response to changes in mechanical loading. Repeated Minor Strain is thought to be the major precipitating factor in tendinopathy, although further work is required to determine whether it is mechanical overstimulation or understimulation that leads to the change in tenocyte activity. Metalloproteinase enzymes have an important role in the tendon matrix, being responsible for the degradation of collagen and proteoglycan in both healthy patients and those with disease. Metalloproteinases that show increased expression in painful tendinopathy include ADAM (a disintegrin and metalloproteinase)-12 and MMP (matrix metalloproteinase)-23. The role of these enzymes in tendon pathology is unknown, and further work is required to identify novel and specific molecular targets for therapy.
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tendinopathy from basic science to treatment
Nature Reviews Rheumatology, 2008Co-Authors: G P RileyAbstract:Tendinopathy, although common, is difficult to treat, and most currently available treatments are not effective or evidence-based. As outlined in this Review, the molecular pathology of the tendon is being elucidated and could lead to the identification of novel therapeutic agents for the treatment of chronic tendinopathies. Chronic tendon pathology (tendinopathy), although common, is difficult to treat. Tendons possess a highly organized fibrillar matrix, consisting of type I collagen and various 'Minor' collagens, proteoglycans and glycoproteins. The tendon matrix is maintained by the resident tenocytes, and there is evidence of a continuous process of matrix remodeling, although the rate of turnover varies at different sites. A change in remodeling activity is associated with the onset of tendinopathy. Major molecular changes include increased expression of type III collagen, fibronectin, tenascin C, aggrecan and biglycan. These changes are consistent with repair, but they might also be an adaptive response to changes in mechanical loading. Repeated Minor Strain is thought to be the major precipitating factor in tendinopathy, although further work is required to determine whether it is mechanical overstimulation or understimulation that leads to the change in tenocyte activity. Metalloproteinase enzymes have an important role in the tendon matrix, being responsible for the degradation of collagen and proteoglycan in both healthy patients and those with disease. Metalloproteinases that show increased expression in painful tendinopathy include ADAM (a disintegrin and metalloproteinase)-12 and MMP (matrix metalloproteinase)-23. The role of these enzymes in tendon pathology is unknown, and further work is required to identify novel and specific molecular targets for therapy.
Anil K Sachdev - One of the best experts on this subject based on the ideXlab platform.
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an analysis of localized necking in aluminium alloy tubes during hydroforming using a continuum damage model
International Journal of Mechanical Sciences, 2007Co-Authors: Siva Prasad N Varma, R Narasimhan, Alan A Luo, Anil K SachdevAbstract:In this work, localized necking in aluminium alloy tubes subjected to free hydroforming is analyzed. The main objective is to study the influence of loading conditions, such as prescribed fluid pressure or volume flow rate in conjunction with axial end feed, on the nature of the forming limit curve (FLC). To this end, the Strain histories experienced at the tube mid-length, which were computed in an earlier investigation [14] [Varma NSP, Narasimhan R. A numerical study of the effect of loading conditions on tubular hydroforming, Journal of Materials Processing Technology 2005; [Submitted for publication]], are analyzed using the Marciniak–Kuczynski (M–K) method along with an anisotropic version of the Gurson model. The Gurson constitutive parameters are determined following an inverse approach using the sheet FLC for the chosen alloy. The predicted FLC for combined pressure and axial contraction corroborates well with the experimental data obtained in [12] [Kulkarni A, Biswas P, Narasimhan R, Luo A, Stoughton T, Mishra R, Sachdev AK. An experimental and numerical study of necking initiation in aluminium alloy tubes during hydroforming. International Journal of Mechanical Sciences 46:2004;1727–46] and is almost flat, whereas it is akin to the sheet FLC and increases with negative Minor Strain when fluid volume is specified. The forming limit Strains for loading with specified fluid volume are in general higher when compared to those with prescribed fluid pressure. Finally, it is demonstrated that a transition from axial to circumferential necking occurs when high ratios of axial extension to volume flow rate are applied to the tube.