H型钢矫直过程残余应力演变机制研究

为在矫直过程中对H型钢的残余应力实施有效地主动控制,对H型钢矫直过程中残余应力演变过程的力学机制进行研究。首先运用弹塑性基本理论对具有初始残余应力的H型钢截面弹塑性反弯过程进行解析分析,论证初始残余应力对截面弹塑性反弯过程的影响方式,证明初始残余应力导致截面弯曲中性轴位移的非对称弯曲状态。在此基础上,利用差分方法建立H型钢矫直过程多次连续弹塑性反弯的数值解法,进而详细研究H型钢矫直过程中残余应力的演变机制。结果表明:截面翼缘与腹板整体拉压应力水平的消减主要依赖矫直前期的非对称弹塑性弯曲过程,而矫直后期的对称弯曲过程则进一步改善H型钢翼缘的残余应力状态;矫直过程前期与后期不同的弹塑性弯曲性质造成了其在矫直过程中对于残余应力演变的不同影响作用。     

基于H型钢残余应力主动控制的矫直工艺设计

针对H型钢辊式矫直过程残余应力的主动控制,基于工程弹塑性理论建立一种矫直过程应力演变的分析模型;采用离散解析实现对模型的快速数值求解;继而基于该分析模型建立一套能够实现残余应力主动控制的工艺参数主动设计方法;运用该方法对典型规格H型钢矫直工艺参数进行工艺设计.建立的分析模型运算结果与有限元结果吻合且计算成本得到有效控制,模型能够实现有限时间内整个矫直工艺参数域内残余应力演变结果的分析;工艺设计方法能够得到一定目标参数和约束条件下的残余应力主动控制工艺参数.     

工程机械用类槽钢矫直工艺有限元模拟

工程机械用类槽钢一引导轮的生产是目前国内类槽钢生产中的空白,其再加工产品主要用于大型机械设备,由于断面形状复杂,产品要求精度高,因此在轧制成型后需要进行冷矫直。采用有限元分析软件ANSYS／LS-DYNA对工程机械用类槽钢矫直工艺进行了模拟研究。研究表明：采用合理的矫直方案确定压下量,能够准确对变形类槽钢进行平直度矫正。矫直过程中的变形主要沿矫直纵向方向上,由于复杂的断面形状使得模拟矫直后应力分布无明显规律,腰部与腿部厚度不同致使产生的应力值不同,同时个别部位存在应力集中。     

电梯导轨矫直压弯挠度理论计算与数值模拟

为使导轨的平直度达到高速电梯的要求,通过应用弹塑性理论,建立了电梯导轨在矫直过程中的数学模型,模型给出了电梯导轨在反弯矫直过程中挠度、弯矩、曲率以及中性层之间的关系,并获得了矫直压下量的取值范围. 通过有限元软件ANSYS分析验证了理论计算得到的矫直压下量取值的可靠性,并证明能够使矫直后的导轨符合使用要求.     

基于ANSYS/LS-DYNA的V150油套管热矫直残余应力

基于有限元分析软件ANSYS/LS-DYNA,建立V150油套管热矫直的三维有限元模型,研究矫直后环向和轴向残余应力的分布规律,并利用X线衍射法测最了矫直管内表面环向残余应力.结果表明:环向和轴向残余应力呈螺旋状分布,螺旋接触带与管体轴向成58°的夹角,与矫直辊倾角互余,相邻的2个螺旋接触带之间的距离约为350 mm,基本等于矫直管的螺距(349 mm);环向残余应力具有外拉内压规律,轴向残余应力外表面以拉应力为主,内表面拉压应力并存,压应力极大值出现在壁厚中部;矫直管内表面环向残余应力的实测值为-189～-489MPa,模拟数值为-130～-480MPa,两者吻合良好,表明建立的矫直模型是可靠的.     

复合重轨矫直机的矫直力计算

钢轨在冷却过程中产生弯曲,为保证钢轨平直度,必须对其进行矫直,因为平直度是钢轨在实际使用中保证安全的重要指标之一.矫直机矫直力的大小,决定了矫直机的设备矫直能力,是矫直机的重要力能参数.本文对辊式钢轨矫直机的矫直力进行计算并与实际数据比较,达到比较满意结果.     

多辊矫直过程中H型钢断面的应力演变规律

采用某厂九辊悬臂式变辊距矫直机的工艺参数,建立了H型钢矫直过程的三维动态有限元仿真模型.分析了矫直过程中型钢横截面上的应力分布变化规律,指出其演变特征类似于应力波从翼缘外侧向内侧、翼缘两端向腹板中部的传播过程.仿真结果表明,腹板连接R角以及腹板和矫直辊圆角接触的部位在多辊矫直的后期处于高应力状态,矫后存在明显的应力残余;纵向正应力水平决定矫直效应,而沿纵向的剪切应力会影响H型钢横截面上等效应力的分布.     

钢轨中残余应力的产生、影响及调控研究现状

近年来随着我国高速、重载铁路的快速发展,列车速度的提升、轴重的加大对钢轨服役性能的可靠性提出了更高的要求。如果钢轨中的残余应力过大且处于不利的分布状态,容易促进疲劳裂纹的形成,并加速扩展,从而严重影响其服役性能。本文汇总了当前针对钢轨中残余应力的测量方法,并论述了钢轨中残余应力的产生原因及其对综合性能的影响机制。同时,依据钢轨生产的工艺流程,从预弯、冷却、矫直、回火等方面出发,综述了国内外研究者在钢轨残余应力演变及其调控领域所取得的成果。最后,对钢轨残余应力演变与调控技术的发展进行了展望。     

考虑包辛格效应的辊式矫直截面反弯特性

基于弹塑性弯曲基本原理,以板材进入矫直机后经历的第2次弯曲为例,建立考虑包辛格效应影响程度(KBa)的辊式矫直复杂弯曲力学模型。采用该模型计算KBa对第2次弯曲时M-C关系和ξ-C关系及残余应力的影响,证明辊式矫直过程中经历多次弹塑性弯曲的截面反弯特性受材料包辛格效应的影响,而且随着材料强化系数的增大,截面弯曲特性所受影响越显著。最后计算相同矫直工况下,KBa不同的材料的残余曲率,得到材料KBa对于残余曲率的影响。研究结果表明:强化系数较大(η0.01)的材料进行矫直仿真时应考虑包辛格效应,在实际生产中确定工艺参数时需要首先确定材料的KBa。     

辊式矫直中H型钢断面畸变的仿真分析

现有的H型钢矫直理论在求解压下量时未考虑断面畸变现象,无法取得理想的矫直效果. 本文应用有限元分析软件ANSYS建立了H型钢辊式矫直时一个矫直单元的有限元仿真模型,研究分析了典型规格H型钢矫直时断面畸变及其主要影响因素和影响规律. 结果表明,H型钢矫直时断面畸变主要是腹板凹陷,其对矫直压下量设定的影响不可忽略;而影响腹板凹陷量的主要因素包括矫直压力、侧向间隙和矫直辊圆角半径等,三者的影响规律均为相应参数的二次函数形式. 最后给出了典型规格H型钢的矫直腹板凹陷量回归公式. 在实际矫直时,实际设定压下量应为理论压下量与腹板凹陷量之和,可取得理想的矫直效果.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that