采用DEFORM-3D三维大变形热力耦合弹塑性有限元软件对Ф21.5 mm GCr15轴承钢坯料在四架KOCKS轧机连轧成Φ16 mm棒材工艺过程进行了数值模拟。分析了棒材在KOCKS轧机孔型中轧制时的等效应力、等效应变、温度场以及轧制力等轧制工艺参数...采用DEFORM-3D三维大变形热力耦合弹塑性有限元软件对Ф21.5 mm GCr15轴承钢坯料在四架KOCKS轧机连轧成Φ16 mm棒材工艺过程进行了数值模拟。分析了棒材在KOCKS轧机孔型中轧制时的等效应力、等效应变、温度场以及轧制力等轧制工艺参数。结果表明,棒材在KOCKS机组中的变形主要发生在延伸孔型,精轧孔型的变形量较小,尤其在最后一道次;棒材在KOCKS机组中的宽展是不均匀,在靠近轧辊的区域宽展较小,在辊缝处宽展较大并产生鼓形;棒材在KOCKS机组中等效应变已达到芯部渗透,这对保证组织致密度和成品内部质量是非常有利的,现场各道次轧制力的实测值与模拟值的相对误差<2%。展开更多
Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural applications.The present work is aimed at nullifying...Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural applications.The present work is aimed at nullifying the tension to compression asymmetry problem and strain hardening anomalies in a Magnesium–Silver–Rare Earth alloy by engineering different levels of microstructural conditions via friction stir processing and post process annealing.The existence and extent of yield asymmetry ratio in the range of microstructural conditions was experimentally obtained through quasistatic tensile and compression tests.The yield asymmetry problem was profoundly present in specimens of coarse grained microstructures when compared to their fine grained and ultra fine grained counterparts.The impact of the microstructure and associated mechanisms of plasticity on the macroscopic strain hardening behavior was established by Kock–Mecking’s analysis.Crystal plasticity simulations using Viscoplastic Self Consistency approach revealed the consequential role of extension twinning mechanism for the existence of yield asymmetry and anomalies in strain hardening behavior.This was especially dominant with coarsening of grain size.Electron Microscopy and characterization were conducted thoroughly in partially deformed specimens to confirm the predictions of the above simulations.The role of crystallographic texture for inducing the polarity to Tension–Compression yield asymmetry was corroborated.A critical grain size in Magnesium–Silver–Rare earth alloy was hereby established which could nullify influences of extension twinning in yield asymmetry ratio.展开更多
Continent ileostomy can be defined as a surgical procedure that facilitates planned intermittent evacuation of a bowel reservoir through an ileostomy.It was devised by Nils Kock in 1969.Subsequently,continent ileostom...Continent ileostomy can be defined as a surgical procedure that facilitates planned intermittent evacuation of a bowel reservoir through an ileostomy.It was devised by Nils Kock in 1969.Subsequently,continent ileostomy (or Kock pouch) became a viable alternative in the management of patients who had traditionally required an end ileostomy.Kock pouch appeared to provide substantial physical and psychosocial benefits over a conventional ileostomy.The procedure became popular until ileal pouch anal anastomosis (IPAA) was introduced in 1980.Despite its benefits,continent ileostomy had many short term complications including intubation problems,ileus,anastomotic leaks,peritonitis and valve problems.Operative mortalities have also been reported in the literature.Most of these problems have been eliminated with increasing experience;however,valverelated problems remain as an "Achilles' heel" of the technique.Many modifications have been introduced to prevent this problem.Some patients have had their pouch removed because of complications mainly related to valve dysfunction.Although revision rates can be high,most of the patients who retain their reservoirs are satisfied with regard to their health status and quality of life.Today,this procedure is still appropriate for selected patients for whom pouch surgery is not possible or for patients who have failed IPAA.Both the patient and their physician must be highly motivated to accept the risk of failure and the subsequent need for revisional operations.展开更多
文摘采用DEFORM-3D三维大变形热力耦合弹塑性有限元软件对Ф21.5 mm GCr15轴承钢坯料在四架KOCKS轧机连轧成Φ16 mm棒材工艺过程进行了数值模拟。分析了棒材在KOCKS轧机孔型中轧制时的等效应力、等效应变、温度场以及轧制力等轧制工艺参数。结果表明,棒材在KOCKS机组中的变形主要发生在延伸孔型,精轧孔型的变形量较小,尤其在最后一道次;棒材在KOCKS机组中的宽展是不均匀,在靠近轧辊的区域宽展较小,在辊缝处宽展较大并产生鼓形;棒材在KOCKS机组中等效应变已达到芯部渗透,这对保证组织致密度和成品内部质量是非常有利的,现场各道次轧制力的实测值与模拟值的相对误差<2%。
基金Department of Science and Technology,India[grant number of DST/TDT/AMT/2017/211(G)(MEE/18-19/412/DSTX/SUSH)for the financial supportFIST grant,Department of Science and Technology,India[grant number SR/FST/ET11-059/2012(G)]for funding electron microscope facility。
文摘Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural applications.The present work is aimed at nullifying the tension to compression asymmetry problem and strain hardening anomalies in a Magnesium–Silver–Rare Earth alloy by engineering different levels of microstructural conditions via friction stir processing and post process annealing.The existence and extent of yield asymmetry ratio in the range of microstructural conditions was experimentally obtained through quasistatic tensile and compression tests.The yield asymmetry problem was profoundly present in specimens of coarse grained microstructures when compared to their fine grained and ultra fine grained counterparts.The impact of the microstructure and associated mechanisms of plasticity on the macroscopic strain hardening behavior was established by Kock–Mecking’s analysis.Crystal plasticity simulations using Viscoplastic Self Consistency approach revealed the consequential role of extension twinning mechanism for the existence of yield asymmetry and anomalies in strain hardening behavior.This was especially dominant with coarsening of grain size.Electron Microscopy and characterization were conducted thoroughly in partially deformed specimens to confirm the predictions of the above simulations.The role of crystallographic texture for inducing the polarity to Tension–Compression yield asymmetry was corroborated.A critical grain size in Magnesium–Silver–Rare earth alloy was hereby established which could nullify influences of extension twinning in yield asymmetry ratio.
文摘Continent ileostomy can be defined as a surgical procedure that facilitates planned intermittent evacuation of a bowel reservoir through an ileostomy.It was devised by Nils Kock in 1969.Subsequently,continent ileostomy (or Kock pouch) became a viable alternative in the management of patients who had traditionally required an end ileostomy.Kock pouch appeared to provide substantial physical and psychosocial benefits over a conventional ileostomy.The procedure became popular until ileal pouch anal anastomosis (IPAA) was introduced in 1980.Despite its benefits,continent ileostomy had many short term complications including intubation problems,ileus,anastomotic leaks,peritonitis and valve problems.Operative mortalities have also been reported in the literature.Most of these problems have been eliminated with increasing experience;however,valverelated problems remain as an "Achilles' heel" of the technique.Many modifications have been introduced to prevent this problem.Some patients have had their pouch removed because of complications mainly related to valve dysfunction.Although revision rates can be high,most of the patients who retain their reservoirs are satisfied with regard to their health status and quality of life.Today,this procedure is still appropriate for selected patients for whom pouch surgery is not possible or for patients who have failed IPAA.Both the patient and their physician must be highly motivated to accept the risk of failure and the subsequent need for revisional operations.
