钢管冷斜轧成形过程的有限元分析

冷斜轧是一种适应中小型无缝钢管企业改进工艺的新型钢管冷加工工艺.在钢管冷斜轧工艺试验室研究的基础上开展了钢管冷斜轧理论的研究,建立了考虑应变、应变率、润滑条件等因素的钢管冷斜轧过程的数学模型,利用塑性成形问题的刚塑性有限元算法计算了钢管冷斜轧过程中塑性变形区的各种分布量,如速度场、应力、应变场等,其结果对辊形设计、选择合理的工艺参数、生产高精度冷轧钢管具有重要的指导意义.     

钢管三辊冷斜轧的轧辊辊型设计

根据钢管冷斜轧过程的变形特点，建立了辊型设计系统。把辊型设计的结果作为初始参数，由刚塑性有限元分析成型过程，将速度场、应变和应力反馈到辊型设计系统，调整辊型设计的初始参数，绘制出适应钢管冷斜轧工艺要求辊型图。     

斜轧钢管缺陷的有限元分析

根据钢管斜轧过程的变形特点,利用ANSYS/LS-DYNA软件进行三维热力耦合弹塑性有限元分析,建立了二辊斜轧钢管有限元模型及其摩擦、传热和接触等重要边界条件。通过仿真计算,获得了二辊斜轧过程中的应力场、应变场、温度场参数的变化特点,并阐述了二辊斜轧过程中出现的多边形效应、前卡现象和扭钢现象以及产生的原因。     

二辊斜轧延伸大口径P92厚壁管分层缺陷倾向性研究

为研究不同轧辊转速、送进角、轧辊人口锥角等工艺参数对大VI径厚壁P92钢管二辊斜轧延伸过程分层缺陷形成倾向性的影响,借助于商用有限元软件MSC．SuperForm,对不同工艺条件下大口径厚壁P92钢管二辊斜轧延伸过程进行了三维热力耦合模拟;采用Oyane韧性断裂准则分析了轧件损伤场及钢管分层缺陷的倾向性。研究结果表明：钢管内表邻近顶头接触区存在破裂高危带,轧件最大损伤特征值随轧辊转速的降低、送进角和轧辊入口锥角的增大而减小,发生分层缺陷的倾向性降低。此研究为揭示钢管分层缺陷形成机制,确定缺陷发生的敏感工况,制定防止或减轻分层缺陷的有效措施提供科学依据。     

超高强度弹簧钢冷变形性能及其仿真模拟

摘要：针对60Si2CrVAT超高强度弹簧钢实际冷卷成形工况，采用准静态拉伸试验和不同微观表征手段研究了经Q&T (Quenching&Tempering)和Q-I-Q-T(Quenching-Isthothermal Quenching-Tempering)工艺热处理后试验钢的组织形貌及冷变形前后力学性能的差异，并利用Deform-3D有限元数值模拟软件分析了2种工艺参数下的弹簧钢在冷卷成形过程中的应力、应变等场量参数的变化特征，预测了其冷卷成形过程中的断裂损伤概率。结果表明，Q-I-Q-T工艺复相组织弹簧钢的塑性更好，冷变形后的断面收缩率和伸长率比Q&T工艺马氏体中温回火组织弹簧钢分别高出了65%和66%。模拟结果显示，不同组织状态下的超高强度弹簧钢在卷制过程中的等效应力和等效应变分布规律近似，但Q-I-Q-T工艺复相组织弹簧钢在卷制过程中产生的等效应力和等效应变值更小，产生断裂的概率更低。     

管成形顶头前伸量对应等效应变率分析

斜轧穿孔是无缝管生产中穿孔工艺的主要生产方法。穿孔质量与效率的好坏直接影响着轧制钢管的产品质量。本文就三辊穿孔过程中顶头前伸量的变化,用刚塑性有限元方法对其进行分析。在理论上分析了前伸量对变形的变化关系。     

斜轧穿孔机与斜轧延伸机轧辊旋转方向的合理配置

从减少钢管在斜轧变形过程中的反向扭转次数出发，研究了辊型对扭转的影响以及斜轧穿孔机和斜轧延伸机轧辊旋转方向的合理配置。研究结果对轧机设计、车间平面布置和提高产品质量有重要意义     

P92无缝钢管内表面裂纹分析及工艺优化

采用斜轧穿孔工艺生产大口径P92铁素体耐热无缝钢管过程中,钢管内表面易产生细小裂纹。通过金相分析、高温相变计算和高温加热试验等研究表明,内表面裂纹产生的主要原因是：中心有通孔的P92管坯在坯料加热过程中,由于加热温度过高和在炉时间过长(即表面氧化脱碳加重),导致管坯通孔近内壁产生大量的高温δ-铁素体相,管坯在随后的斜轧穿孔中,裂纹在塑性较差的高温δ-铁素体处产生和扩展。根据内表面裂纹的产生机制,通过对P92钢管化学成分的铬当量、镍当量按Cr_eq<13%、Ni_eq>4%进行控制,坯料保温温度由原工艺的1220～1250℃降为1190～1220℃,对穿孔机轧辊转速、辊距和顶伸量参数优化等工艺改进措施,有效地解决了大口径P92无缝钢管内表面易产生裂纹的问题,提高了P92无缝钢管的成材率和生产效率。     

斜轧螺纹过程的数值模拟

对螺旋孔型斜轧螺纹过程进行了非线性有限元分析，得到了轧件内部应力－应变分布情况，为模具的设计和工艺参数的确定提供了重要依据。     

技术信息

技术信息新型锥形辊钢管斜轧延伸工艺ＮＥＷＴＥＣＨＮＯＬＯＧＹＦＯＲＴＵＢＥＥＬＯＮＧＡＦＩＯＮＷＩＴＨＣＲＯＳＳＲＯＬＬＩＮＧＢＹＣＯＮＥＲＯＬＬＥＲＳ江苏省诚德钢管集团公司与北京科技大学、武汉钢铁设计研究院共同研究成功新型锥形辊钢管斜轧延伸工艺。采...     

论从实践理解世界的物质性和自然世界的先在性

马克思主义唯物论是一种物本主义形态的唯物论,还是一种超越物本主义形态、从实践理解世界的本质相关问题的实践的唯物主义的唯物论?这是一个我们必须搞清楚的有关马克思主义唯物论的本质规定性和精神实质的重大问题.在考察物本主义的唯物论及其思维方式的局限性的基础上,揭示了马克思主义唯物论是现代的、实践的唯物主义,并重点研讨了马克思主义唯物论关于从实践理解世界的物质性和自然世界的先在性的原理,以期为马克思主义唯物论进一步阐明人类世界的实践性原理奠定基础.     

Effect of cyproheptadine on the ultrastructure of the neurons of the arcuate nucleus in the hypothalamus of the rat

The data are presented on changes in the rat arcuate nuclear neuron ultrastructure after using cyproheptadine (peritol, Egyt Pharmaceutical Works, Hungary) in a water suspension at a dose of 20 mg/kg once daily during 7 successive days and twice a day within 10 days. It was shown that cyproheptadine decreases the functional activity of the arcuate nuclear neurons, depending on the total amount of the drug used. Cyproheptadine-induced inhibition of the forming neurohormone release from neurons is likely to be one of the mechanisms of its therapeutic effect in Itsenko-Cushing's disease.     

Characteristics of the sympathetic innervation of the nictitating membrane and of the vasculature of the nose and tongue of the cat

Vasomotor responses from the nasal mucosa and tongue, and contractions of the nictitating membrane, were recorded on stimulation of the cervical sympathetic or internal carotid nerves. Preganglionic sympathetic nerve fibres which elicited a membrane response possessed a lower threshold than those which evoked nasal vasoconstriction, while the latter displayed a lower threshold than fibres which evoked tongue vasoconstriction. The sympathetic vasodilator fibres to the tongue whose activity was revealed after alpha-receptor blockade, had a similar threshold to the vasoconstrictor fibres. Membrane contraction, nasal vasoconstriction and occasionally tongue vasoconstriction could be evoked by stimulating the internal carotid nerve. The postganglionic fibres innervating the nasal mucosa had a similar threshold to those of the nictitating membrane, which may indicate that there are small myelinated fibres innervating the mucosa. The preganglionic compound nerve action potential had four major components, S1-S4. S1, S2 and usually S3 fibres were associated with membrane contraction; S2, S3 and sometimes S1 fibres were associated with nasal vasoconstriction; and S3, usually S2 and occasionally S1 fibres were associated with vasoconstriction in the tongue. It is concluded that each of these three groups of nerve fibres, but not S4 fibres, may include fibres associated functionally with the three effectors. There was a considerable difference between the relative amplitude of the responses of the three effectors elicited by stimulation of the cervical sympathetic nerve at frequencies between 0.2 and 2 Hz. Vasoconstrictor responses were relatively larger than membrane contractions suggesting differences in the mechanisms of neurotransmission at the neuroeffector junctions.