超声纵波法测量紧固螺栓的应力

论述了螺栓应力测量的重要性,建立了用超声纵波对紧固螺栓进行应力测量的实验系统和方法,实验结果表明其具备很好的可行性和有效性。     

声弹性螺栓应力测量影响因素

为了分析声弹性法螺栓应力测量中的影响因素,从固体质点声弹性理论入手,在模型中加入质点受力形变因素,建立质点时差法应力测量模型;针对螺栓结构建立不同轴向预紧力下应力分布,获得超声传播路径上的应力分布表达式,建立不均匀应力下的螺栓声弹性测量模型;设计应力不均匀区占超声路径比例不同的实验,采用基于ZnO压电薄膜的方式激发超声,压电薄膜溅射于螺栓表面,避免使用超声耦合层引入的测量误差,得到应力不均匀区与测试误差的关系;进行螺栓反复拉伸后声弹性测量的重复性实验,验证材料性质与螺栓应力测量的关系。研究结果表明,超声时差与应力呈线性关系;声弹性系数由螺栓的弹性模量、泊松比以及螺栓长度决定;不同应力非均匀区占比的螺栓应力测量误差相同,初始误差小于2%;螺栓反复拉伸后,声弹性螺栓应力测量误差变大;应力分布不会产生测量误差,测量误差来源于材料的非均匀性;经过拉伸后的螺栓,材料中的缺陷和错位增大,增强高频超声的散射,引起应力测量误差变大。     

螺栓超声波探伤工艺方法研究

以小角度纵波为主,横波为辅,配合涡流探伤仪进行验证的螺栓超声波探伤工艺方法,具有灵敏度高、信噪比高、能对螺栓缺陷定位、定量的优势,改变了传统探伤试验方法中采用纵波直探头的惯例,为在役高温高压紧固螺栓的安全运行提供了有效的检测手段.     

超声纵波法测试铝合金的内部应力

声各向同性的金属材料在应力作用下表现出声各向异性,这是用声弹性法分析材料内部应力的基础。用垂直于应力方向传播的超声纵波对LY11型铝合金进行测试。实验结果表明:材料在拉、压单轴应力作用下,超声纵波声速都发生了变化:声速随拉应力的增大而增大,随压应力的增大而减小;且声速相对变化率与应力呈线性关系,并拟合出相应的直线方程,直线斜率为铝合金纵波声弹性系数。通过实验提供了一种无损检测材料内部应力的方法。实验中用回振法测量声速,时间测试精确度可达10-11s,可精确测量声速的微小变化量。     

相控阵纵波超声法检测铝合金内部应力的实验研究

铝合金材料在航空航天、汽车制造、船舶制造等领域广泛应用，其制造和装备过程中的载荷应力和残余应力会直接影响铝合金构件的机械性能和疲劳寿命。为评估铝合金的内部应力，文中基于声弹性原理，研究相控阵纵波检测技术，应用纵波传播时差法构建铝合金内部应力的检测方法；搭建相控阵纵波超声检测应力的实验系统，开展标定实验，获得铝合金内部应力与纵波传播声时差的关系式，得到超声传播声时差与内部应力之间的线性关系，在0～286 MPa的拉伸应力范围内，5 mm和3 mm厚铝合金板平均应力的标定绝对误差不超过2.85 MPa和10.82 MPa，相对误差不超过2.36%和13.93%，两种规格铝合金板的最大相对误差都出现在应力小于28.58 MPa的范围内，表明在小应力测量时需提高超声测量的分辨率和精度；应用相控阵纵波检测系统对5 mm厚铝合金板试样进行检测，平均应力误差为（1.174±4.567）MPa，绝对误差小于9.42 MPa，估算得到初始残余应力为3.329 MPa。实验结果表明，相控阵纵波超声法对5 mm厚铝合金板平均应力的检测效果好，应用纵波传播时差法可以对应力类型、应力大小、残余应力进行检测，该技...     

声发射信号通过螺栓紧固联接界面的试验研究

在声发射的实际应用中,采集的声发射信号很多都是经过不同界面传输的,其传播特性也受到不同程度的影响,其中通过螺栓紧固联接平面界面传播是最常见的一种。分析了引起声发射信号衰减的各种原因,采用成都动科信号采集卡及其相应的分析系统,模拟设计几组螺栓紧固联接平面试件来进行声发射信号传播特性研究。初步分析研究了在表面粗糙度、压力、接合面介质等不同条件下声发射信号通过螺栓紧固联接平面界面传播后的衰减情况,为声发射检测复杂结构设备具有重大参考意义。     

核电紧固螺栓的超声速度和衰减

本文报道了对秦山30万千瓦核电厂紧固螺栓的超声波纵波和横波的速度和衰减所进行的实验研究．并对测量结果进行耦合层修正和衍射修正。实验结果表明：用于制作核电紧固螺栓的高强度低合金钢．具有低超声衰减特性．其声速略小于普碳钢．是一种理想的超声检测媒质。     

声弹性法及其应用

本文在论述常用金属材料声弹性法则的基础上,着重介绍了作者用超声法测定螺栓预紧应力、岩石弹性常数、聚氨酯组合梁相当动弹横方面的试验工作与结果.试验结果表明:超声法测岩石弹性常数具有迅速、准确、方便之优点,是量测聚氨酯之类低弹模材料力学性质的理想方法,量测短螺栓预紧应力的精度较高,其量测精度为±9.8MPa.     

超声临界折射纵波测量应力的温度影响

超声临界折射纵波(LCR波)法是无损检测工作状态下结构应力的有效方法.超声LCR波法是敏感测量方法,温度直接影响超声波的传播速度,也会引起超声换能器的尺寸变化.根据超声波测量应力的基础理论-声弹性理论,分析声弹性系数和零应力下飞行时间与温度的定量关系,得到超声波测量应力的温度补偿公式,通过试验测量不同温度下超声LCR波...     

螺栓紧固铝板的微动疲劳寿命分析

以螺栓紧固铝板为研究对象,应用固体力学中的有限元分析理论对疲劳荷载作用下的螺栓紧固铝板进行分析计算,找出最大应力和最大位移所在位置,并在此基础上分别采用Miner疲劳损伤理论和有限元软件中的疲劳分析模块进行疲劳寿命分析及裂纹扩展寿命分析,且与已有实验进行对比,从而为螺栓紧固铝板的正确和安全使用提供了可靠的依据。     

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