碳纤维经编针织复合材料钻孔过程有限元建模与实验研究

为了研究碳纤维经编针织复合材料的钻削加工过程,通过分析经编针织物的细观结构,利用有限元分析软件ABAQUS建立复合材料钻削有限元模型,并联合用户子程序VUMAT定义复合材料的本构模型,模拟钻削加工过程.仿真结果表明:Z向轴向力与进给速度呈正相关,与主轴转速呈负相关.通过对碳纤维经编针织复合材料进行钻削实验,将实验结果与仿真结果进行对比,验证了有限元模型的正确性.为碳纤维经编针织复合材料钻削加工过程的优化提供了理论依据.     

钻头形状对TC4材料制孔切削力影响的有限元分析

针对钻削TC4时存在摩擦大、钻头磨损快等问题,基于有限元软件建立了三维有限元钻削模型,通过试验验证模型准确性。研究结果表明,轴向力与转矩的仿真值和试验值的相对误差分别为13.5%和10.8%,这表明有限元方法预测的轴向力和转矩与试验结果基本吻合,该有限元模型可以用来预测钻削TC4时的轴向力和转矩。然后基于该有限元模型,研究钻头几何参数(顶角和螺旋角)对轴向力及转矩的影响趋势。研究结果表明,随着顶角的减小,轴向力呈下降趋势,转矩呈上升趋势;随着螺旋角的增大,轴向力和转矩都呈下降趋势。     

碳纤维增强复合材料纵扭复合超声振动钻削试验

碳纤维增强复合材料(CFRP)以其优越的性能被广泛应用于航空航天领域,然而其作为典型难加工材料,采用传统钻削加工时极易出现毛刺、撕裂、分层及加工表面质量差等现象,严重制约了CFRP的应用。采用纵扭复合超声振动钻削和普通钻削两种钻削方式加工CFRP板材,对比了两种钻削方式下的轴向力、扭矩及钻孔质量,研究了单向型和编织型CFRP板材的钻削轴向力特性,分析了转速、进给速度对钻削轴向力的影响规律。试验表明:纵扭复合超声振动辅助钻削可以更加有效切削CFRP,降低轴向力和扭矩,降低撕裂因子,抑制分层现象;钻削轴向力随着进给速度提高而增大,随着钻速的提高而降低,且当Vc/Vf增大时,钻削轴向力随之下降,试验拟合得到轴向力经验公式。     

小角度螺旋槽钻头加工复合材料的模拟研究

针对碳纤维复合材料制孔时易产生毛刺、撕裂、分层等难题,首次提出了一种螺旋角为10°且顶角为83°的小角度螺旋槽钻头加工碳纤维复合材料的方法,并进行了钻削过程的有限元模拟分析.给出了主轴转速、进给速度、钻头几何角度等对加工过程中产生的钻削轴向力的影响,对比分析了两种钻头加工碳纤维复合材料的轴向力和加工出口质量.结果表明:复合材料的钻削轴向力受主轴转速的影响大于进给速度,并随主轴转速的增大而减小,随进给速度的增大而增大;同时,小角度螺旋槽钻头加工碳纤维复合材料时产生的轴向力小于麻花钻,破坏区域小,加工质量好,更适合碳纤维复合材料的制孔加工.     

基于ABAQUS/Explicit的SiC_p/Al复合材料三维微孔钻削有限元仿真

应用ABAQUS中Explicit显式求解器,基于微观尺度下的Johnson-Cook本构方程,对高体积分数SiC_p/Al复合材料微孔钻削过程进行了三维有限元仿真。研究了钻孔过程中钻削轴向力和扭矩的变化特性以及不同主轴转速和进给速度下钻削轴向力和扭矩的变化规律。此外,对不同主轴转速下钻屑形态的变化特性进行了分析。研究结果为颗粒增强金属基复合材料的微孔钻削工艺参数制定提供了参考。     

轴向振动钻削过程的有限元动态仿真

针对钻削工艺特点,分析了轴向振动钻削的有限元动态特性。利用有限元分析软件DEFORM建立了轴向振动钻削的有限元数学模型,进行了动态仿真分析,同时,建立了相应的普通钻削系统的有限元模型,对两种加工过程中的切屑、轴向力与钻削扭矩等进行了比较。结果表明,与普通钻削相比,轴向振动钻削过程具有较好的断屑效果,轴向力小,钻削扭矩小。研究结果可对轴向振动钻削机理与特点的研究提供参考。     

轴向超声振动钻削的钻削力和切屑形态研究

建立了钻削加工仿真模型,并采用麻花钻对钛合金进行振动钻削试验。利用ABAQUS软件进行轴向超声振动钻削仿真,试验验证和对比分析了轴向超声振动钻削在不同加工参数下的切屑形态和钻削力。仿真与试验结果表明:随着进给量和振幅增加,钻削力增大,但进给量对钻削力的影响大于振幅;无论是进给量还是振幅的改变,对切屑形态均有影响。     

基于Deform-3D轴向振动钻削P20有限元仿真

针对机械特种加工振动钻削过程的工艺选择对加工效率及表面质量的影响等问题,基于有限元分析软件Deform-3D模拟振动钻削P20模具钢的加工过程.通过单因素试验法分析主轴转速、进给速度和振幅对于轴向力和转矩的影响,并与普通钻削加工进行对比;通过正交试验法验证了钻削参数对轴向力和转矩的影响规律.研究表明:振动钻削相比普通钻削可以降低轴向力和转矩,具有更好的钻削工艺特性.     

SiC_p/Al复合材料薄壁圆弧板钻削加工的有限元仿真分析

SiC_p/Al复合材料薄壁钻孔与厚壁钻孔相比有特殊性,本文应用ABAQUS软件对SiC_p/Al复合材料薄壁圆弧板钻削过程进行有限元仿真,研究钻削过程中切削力的变化特征及切削用量对钻削力的影响。研究结果表明:在钻削壁厚小于钻尖高度的薄壁圆弧板时,根据钻尖相对薄壁孔的位置,钻削过程可分为三个过程,在不同阶段钻削力变化特点不同;随钻削速度的增加轴向力略有增加而扭矩有所下降,但是变化幅度均不大;轴向力和扭矩均随进给量的增大而增大。     

高速钻削芳纶纤维复合材料轴向力预测模型研究

采用超细微碳化钨晶粒麻花钻YG6对双向编织黑色芳纶纤维复合材料(AFRP)进行高速钻削试验研究。综合考虑钻头螺旋角β、顶尖角θ、主轴转速n、每齿进给量f对钻削轴向力Fz的影响,设计了正交试验表L27(3~(13))。采用多元回归方程建立钻削轴向力的模型,并利用SPSS软件对试验数据进行迭代运算最终得到轴向力模型。最后对轴向力模型进行回归分析和实验验证,得出该模型预测值与实际钻削轴向力误差最大值小于7. 86%。本文为芳纶纤维复合材料高速钻削加工参数的选取提供有效的参考依据。     

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.