十字横向承载焊接接头疲劳裂纹扩展寿命估算

利用一种新的计算模型，用有限元法计算了十字焊接接头疲劳裂纹尖端的应力强度因子值，并拟合了裂纹在焊根和焊趾处扩展的应力强度因子表达式。据此利用Ｆｏｒｍａｎ疲劳模型，考虑显微金相组织的影响，估算了裂纹扩展寿命，与实验值比较，结果合理。     

焊接接头疲劳评定的等效应力强度因子法

等效应力强度因子 (equivalentstressintensityfactor,简称E SIF)法是近年来提出的一种新的疲劳评定方法 ,文中采用 16Mn钢的非承载角焊缝十字接头的疲劳试验结果对E SIF法的有效性进行研究 ,并分析讨论影响这种方法的有关因素。结果表明 ,采用等效应力强度因子法能对 16Mn钢非承载角焊缝十字接头的疲劳性能作出合理的评定 ,并能预测焊接接头的疲劳断裂位置 ,且该方法适合于焊态接头和较小焊趾半径的疲劳评定。等效应力强度因子法对应力集中区单元尺寸有一定的依赖性 ,对实际焊接接头的焊趾半径变化范围 (在 0 .15mm～ 0 .8mm内 ) ,选择焊趾半径与最小单元尺寸的比值 ρ/emin>1.7时 ,可以获得合理有效的等效应力强度因子ΔKⅠ 值计算结果 ;当焊接接头的焊趾半径较小 ( 0 .15mm～ 0 .40mm)时 ,等效应力强度因子法更为合理     

局部法评定铝合金搅拌摩擦焊接头疲劳性能

三种不同的局部法,临界距离法、应力平均法和等效应力强度因子法,用于评估Al6082-T6铝管搅拌摩擦焊焊接接头的疲劳性能。结果表明,3种疲劳评定方法都能对铝合金搅拌摩擦焊接头做出合理的评定。运用临界距离法时采用Peterson修正公式计算临界距离参数L,结果表明该方法能够精确预测出Al6082-T6铝管搅拌摩擦焊焊接接头的疲劳极限,预测误差仅4%,并能预测出接头疲劳薄弱区域;应力平均法的预测结果偏保守,预测结果较试验值低7.46%,其将焊趾视为尖锐缺口的做法具有工程应用价值。等效应力强度因子法通过将接头模拟成带标准裂纹的构件来计算焊接接头等效应力强度因子范围,并通过与接头裂纹扩展门槛值比较来判断焊接件是否发生疲劳失效,结果表明等效应力强度因子法能够对Al6082-T6搅拌摩擦焊接头做出合理的疲劳评定。     

汽车下摆臂断裂失效分析

采用OM、SEM、 光谱仪等设备对下摆臂焊合件的焊接接头及母材显微组织、 断口显微形貌和材料的化学成分进行了分析,发现焊缝中存在根部裂纹及焊缝边缘存在未熔合缺陷.由于焊接工艺不当,导致下摆臂在焊接接头中形成冷裂纹,在服役应力的作用下,疲劳裂纹扩展,最终导致下摆臂断裂失效.结果表明:通过焊接工艺的改进,增加焊后去应力退火...     

基于ANSYS的裂纹尖端应力强度因子研究

通过ANSYS建立焊接接头三区域模型。分别定义了不同的力学性能参数来模拟焊接接头各个区域力学性能的不均匀性,分别计算裂纹处在焊接接头各个区域的应力强度因子。计算结果表明：焊缝应力强度因子最低,母材次之,热影响区最高。说明材料的屈服强度与裂纹尖端的应力强度因子有密切的关系。屈服强度越高,应力强度因子越低。     

T形焊接接头根部裂纹应力强度因子研究

建立T形焊接接头根部裂纹的半椭圆裂纹模型,定义裂纹模型的构形参数以及边界条件,分析裂纹尖端的应力强度因子。采用奇异单元法,通过有限元计算,模拟裂纹尖端的应力奇异性。并通过收敛性检验确定裂纹尖端的单元尺寸。在此基础上,计算裂纹尖端量纲一应力强度因子,并分析其受几何参数影响的变化规律。计算结果表明,对于给定的载荷条件下,不同初始裂纹尺寸时,裂纹尖端的应力强度因子存在一定的规律性,且不同几何参数对应力强度因子的影响程度存在一定差异,因此,对焊接结构疲劳强度研究时需要有一定的侧重点。采用多重线性回归方法拟合仿真计算结果,这些结果为进一步研究T形焊接接头根部裂纹扩展和疲劳寿命预测提供参考。     

2195铝锂合金火箭贮箱焊接接头强度分析

为确定火箭贮箱搅拌摩擦焊(FSW)焊接接头疲劳寿命,完成对贮箱结构的疲劳分析,对2195铝锂合金母材标准试件与搅拌摩擦焊焊接接头标准试验件进行静力试验与常幅疲劳试验,得出母材与FSW焊接接头的拉伸强度等力学性能参数,同时绘制其S-N曲线。在试验数据基础上,应用ABAQUS软件对贮箱进行静力分析,联合NCODE软件估算贮箱模型在给定工况载荷下的疲劳寿命。结果表明：应力最严重位置为筒段焊缝处,最先破坏位置发生在筒段横竖焊缝交接处。在疲劳寿命分析的基础上应用ABAQUS-FRANC3D软件联合仿真,在焊缝破坏位置处插入角裂纹,模拟三维裂纹扩展,当裂纹扩展为穿透裂纹时,计算终止。计算了三维表面裂纹的应力强度因子和裂纹扩展寿命,为贮箱损伤容限提供了评估思路。     

铸造起重机金属结构的疲劳评定方法研究

铸造起重机金属结构的疲劳裂纹源主要位于构造形状突变区域的焊趾部位,裂纹从焊趾处萌生并扩展,因此必须引入局部应力概念对其进行疲劳评定。针对某在役铸造起重机金属结构,分别采用基于中值主S-N曲线的等效结构应力法和基于等效结构应力强度因子的断裂力学法,估算了端梁结构4条主焊缝危险点的疲劳寿命。结合铸造起重机实测裂纹数据进行了反推计算,获得了等效结构应力法的适用S-N曲线和断裂力学法的适用初始裂纹表面长度。研究表明,常规参数的等效结构应力法和断裂力学法是一般焊接结构疲劳评定的有效方法,但针对焊缝质量有特殊要求的重要焊接结构,必须采用合理的参数才能获得较准确的估算结果。     

核电汽轮机转子焊缝金属原奥氏体尺寸对疲劳裂纹稳定扩展区和近门槛区临界点的影响规律研究

研究了25Cr2Ni2MoV核电汽轮机低压焊接转子模拟件埋弧焊焊缝金属疲劳裂纹扩展速率和应力强度因子幅关系曲线,发现了不同试样疲劳裂纹稳定扩展区和近门槛区临界点对应的应力强度因子幅不同的现象。使用逆推法在金相中确定了临界点位置,并进一步研究了临界点处的原奥氏体晶粒尺寸,发现其与裂纹尖端单向塑性区最大尺寸有较好的对应关系。而模拟件多层多道焊焊缝金属组织不均匀性带来的临界点位置的差异是造成门槛值测试结果分散的重要原因之一。     

起重机承轨梁翼缘焊缝受力分析

起重机承轨梁翼缘焊缝受力分析大连理工大学张晓丽，屈福政，高顺德本溪钢铁公司二钢厂吴成民，杜小平冶金起重机较多采用的偏轨箱形主梁及空腹四柜架工字主梁都是小车轨道的承轨梁。它们的主梁翼缘焊缝损坏较多，主要由于这类焊缝的受力为双向应力状态。当构件同一计算点...     

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。     

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....     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.