压裂泵阀箱自增强技术仿真研究

基于弹塑性自增强理论,对压裂泵阀箱进行了弹塑性有限元非线性研究,探讨了自增强技术和机械加工精度对阀箱疲劳寿命的影响。分析了不同自增强压力下的阀箱应力,确定了阀箱内腔相贯线处最佳自增强压力为420.6 MPa。对自增强前后阀箱的疲劳寿命进行预测结果表明:阀箱疲劳薄弱区位于内腔相贯线处,自增强后疲劳薄弱区向壁间转移,偏离了疲劳危险区域,阀箱内壁表面材料得到有效保护。自增强技术使阀箱应力峰值降低了30.61%,最低疲劳寿命提高了6.97倍。自增强技术与提高阀箱内腔表面加工精度的方法相比,前者对延长阀箱疲劳寿命效果更佳。     

基于应变硬化模型的复合自增强圆筒的应力分析

自增强是通过提高压力容器的残余应力来增强他们的承载能力和疲劳寿命。自增强复合圆筒可以承受比一个具有相同尺寸的单层圆筒更高的压力。引入了应变硬化模型,对自增强复合圆筒的残余应力进行了分析,并对其分布进行了预测。研究表明:复合圆筒内壁的切向残余应力和应力幅随着超应变度的增大而增大。缩套是提高压缩残余应力的一个非常有效的方法。     

残余应力松弛和自增强处理压力对在役高压容器的安全影响

为了确定残余应力松弛和自增强处理压力对在役高压容器安全性能的影响,通过分析测试结果获得了残余应力的松弛规律,计算了在工作压力、残余应力作用下的当量等效应力沿壁厚分布情况,模拟计算出了不同的工作压力、自增强处理压力下的安全系数,推导出了最佳自增强处理压力。结果表明所研究的高压聚乙烯反应管在使用10年后,环向应力在近内壁区衰减最快,从-600MPa衰减到-333MPa,衰减率达45%;在弹性区衰减较小,残余应力峰值位置外移,但其峰值大小变化不大。对于自增强处理后的压力容器,在工作压力作用下,随着残余应力的松弛,内壁面当量等效应力增大,当量等效应力在弹塑性交界处最大,应该按此处的当量等效应力计算安全系数。依据示例聚乙烯反应管尺寸,模拟计算出在工作压力分别为180、280、380MPa时,经过自增强处理压力分别为606、677、743MPa的最佳自增强处理后,其安全系数比残余应力全部衰减为0时分别高16%、26%、37%。压力容器工作压力越大,经最佳自增强处理后安全系数增大得越多,但残余应力衰减对其安全影响越大。     

泵阀箱材质自增强与疲劳强度研究

以内壁带“Ｖ”型缺口的厚壁圆环为对象,对两种高压泵阀箱常用钢４３ＣｒＮｉ２ＭｏＶａ、４２ＣｒＭｏＡ在自增强处理前后的疲劳寿命进行了理论分析与实验研究。首先用弹塑性有限元法计算了自增强后所形成的残余应力,发现自增强处理后在缺口根部所形成的残余应力有一最大值,有明显的残余应集中现象。     

自增强疲劳寿命的理论分析

自增强处理是化工、石油行业提高高压设备承载能力和疲劳寿命的重要举措。文中利用断裂力学理论和疲劳损伤理论,探讨研究了自增强处理后残余应力对高压设备寿命的影响,得出引入残余压应力能提高高压设备寿命的结论,对今后在自增强处理方面的实验与理论研究具有指导意义。     

爆炸冲击波压应力处理预防水轮机叶片裂纹的可行性

大型混流式水轮机叶片的开裂属疲劳裂纹问题,主要与交变应力过大和残余应力过高有关.研究和应用表明,采用焊后600 ℃(8 h的热处理只能消除少量残余应力,接近屈服强度的剩余拉应力严重降低材料的疲劳性能,加速疲劳裂纹的形成和扩展.在叶片易开裂部位进行压应力处理可大大提高疲劳寿命,爆炸冲击波处理用一次均匀微量塑性变形代替喷丸或锤击的多次不均匀变形实现压应力处理,可以避免表面粗化和微裂纹,其形成的压应力层厚度可提高10倍以上,还能起到治愈缺陷的作用.经爆炸处理的16Mn钢焊接接头疲劳强度提高60 MPa,疲劳裂纹扩展速率降低10倍.在已获得的100多件大型水工结构爆炸处理满意结果的基础上,此法用于水轮机叶片的压应力处理,提高其疲劳寿命是完全可行的.     

前混合水射流喷丸强化表面力学特性及疲劳寿命试验

为获得前混合水射流喷丸强化增益效果,研究前混合水射流喷丸对2A 11铝合金和45钢的表面显微硬度、表面残余压应力和疲劳寿命的影响.采用显微硬度计和X射线应力分析仪分别测定喷丸表面显微硬度和表面残余应力,利用扫描电镜观察疲劳断口形貌,获得喷丸表面显微硬度和表面残余压应力随喷丸压力、扫描速度及靶距的变化规律,指出射流喷丸可以大幅度地提高2A11铝合金和45钢的疲劳寿命,当2A11铝合金和45钢的应力振幅分别为155.7 MPa和282MPa时,喷丸试样疲劳寿命比未喷丸试样疲劳寿命分别提高25.31倍和18.56倍,且未喷丸试样疲劳裂纹萌生于试样表面,喷丸试样疲劳裂纹有的萌生于试样表面,有的萌生于试样内部,当疲劳源在试样内部时,裂纹在夹杂物处萌生.因此,前混合水射流喷丸是一种提高金属零构件疲劳寿命的有效方法.     

金属材料冷变形时预应变增强效应与损伤效应浅析

从残余应力与分子力的变化 2个方面分析了预应变的增强效应和损伤效应的原因。预应变产生的附加内力及残余压应力是其提高疲劳抗力的原因 ;当预应变水平较低时 ,增强效应占优 ,有利于提高疲劳寿命 ;反之 ,损伤效应是主要的 ,将导致疲劳寿命降低。     

超高压泵承压件优化设计方法

针对超高压泵承压件的开裂问题,对承压件的组成、疲劳裂纹产生和扩展的机理进行了分析,通过循环载荷特性分析及影响疲劳寿命的主要因素研究,得出影响承压件的疲劳寿命的两大因素为疲劳强度和承压件内壁受到的交变应力的结论,并进一步提出解决承压件开裂问题及提高寿命的两个关键技术途径为提高材料的疲劳强度和降低承压件内壁的应力水平。对采用改进设计的承压件的超高压泵在280 MPa压力下进行寿命考核试验,承压件寿命从50 h左右提高到250 h以上,提高了4倍。试验结果验证了提高承压件寿命的理论和方法的有效性。该方法可以在类似的超高压设备的设计中得到应用。     

在役超高压反应管的疲劳强度及裂纹扩展寿命的研究

本文根据带内外壁人工缺口高压聚乙烯反应管的内压疲劳试验结果,分析了适用于厚壁管的应力强度因子表达式,研究了残余应力衰减对反应管疲劳裂纹扩展寿命的影响。研究结果表明:厚壁管的疲劳裂纹扩展计算应采用Newman—Raju公式(对外壁裂纹还应进行适当修正);自增强残余应力的作用主要在提高裂纹萌生寿命,而对在役反应管的裂纹扩展寿命影响不大;反应管的裂纹扩展寿命较短,所以应尽量避免内外壁产生裂纹。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.