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1.
为了解决高应变率条件下剪切测试的困难,拟利用压电晶体作为剪应力的传感器.综合比较了能产生理想的纯振动模式的特殊晶体的各项参数和性质,然后对镓酸锂和钛酸钡晶体的纯模方向进行了计算验证.考虑到与霍普金森压剪杆(SHPSB)的铝杆的阻抗匹配问题,计算了晶体中压缩波传播波阻抗.研究结果表明镓酸锂和钛酸钡晶体能满足SHPSB实验对剪应力计的要求,单独测出剪切信号,这将大大提高实验装置的性能.  相似文献   

2.
为了研究典型功能脆性材料钽酸锂和硅片的磨削特性,建立了端面磨削模型来计算晶片的比磨削能及其表面的磨削力的分布,并通过实验分析脆性材料的磨削特性。以进给速度作为变量,选取砂轮端主轴磨削过程中功率增加率作为评价磨削特性的指标进行磨削实验,同时采集砂轮端主轴的功率值信号,滤波后计算晶片比磨削能和磨削力的分布。通过端面磨削模型计算可得:钽酸锂的比磨削能是147.46J/mm~3,比硅的大44%,表明磨削去除相同体积的钽酸锂需要更多的能量,钽酸锂晶片表面分布的磨削力比硅片大。磨削过程的主轴功率增加率是预测钽酸锂加工结果的重要指标,在本实验中一旦增加率大于临界值0.6W/s,钽酸锂表面就会产生裂纹。而在相同加工条件下,无论进给速度如何变化,硅片的磨削主轴的功率增加率始终保持稳定,而钽酸锂的主轴磨削过程的功率增加率则与进给速度呈现线性增加关系,这一现象与钽酸锂的机械性质无关,而与物理性质有关系。  相似文献   

3.
铌酸锂作为一种优良的人造非线性光学晶体,在光学频率变换、参量振荡和微纳结构制备等方面得到了研究人员的广泛关注。基于高压针尖极化法,在铌酸锂晶体表面制备了微畴结构,通过点畴和线畴结构制备试验,探究了铌酸锂畴结构制备的工艺条件。对于厚度为0.5mm、掺镁浓度为5%的z切铌酸锂晶体,在极化电压为2.7kV、占空比为25%、移动速度为15μm/s的条件下,制备出了均匀的线状畴结构。  相似文献   

4.
韩志仁  陶华 《机械强度》2006,28(4):611-615
对于三维屈服函数,正交异性材料异性参数的确定需要单拉(或单压)、纯剪切等六个简单试验。基于周维贤提出的屈服函数,针对无法进行纯剪切试验的情况,可以采用六个简单压缩试验间接地确定纯剪切屈服曲线。并由此得到等效屈服曲线和材料的异性参数,同时推导出确定剪切屈服曲线、材料的异性参数的公式。根据这种方法,对材料LD2CS进行实验,给出试验和计算结果。此方法解决了常规方法中因无法进行纯剪切试验而无法确定材料异性参数的困难。  相似文献   

5.
本文报道了对手掌骨、指骨进行剪切、冲击实验研究的结果。得出了指骨冲击功和冲击韧性值及剪切力、剪应力值,并对指骨的损伤机制进行分析讨论。  相似文献   

6.
《衡器》2017,(11)
本文在分析采用圆孔形工字截面的剪切式电阻应变式负荷传感器的腹板中心线上剪应力分布规律的基础上,提出了基于用三条直线线段拟合剪应力曲线来计算圆孔形工字截面腹板最大剪应力的近似方法。针对实际应用中常会用到的不同工字截面形状,建立了使用本文方法的基本参数K值表,介绍了相应的应用方法。通过与实测结果及三维有限元数值结果的比较,验证了本文方法不仅计算简便而且具有很高的计算精度,更有能广泛适用于各种复杂的圆孔形工字截面上最大剪应力计算的特点。  相似文献   

7.
针对高周疲劳损伤局部化,基于连续介质损伤力学,将临界域均布全寿命内禀损伤耗散作为等寿命条件,导出考虑平均剪应力效应的纯扭疲劳强度预测模型。新建预测模型揭示了纯扭疲劳强度与材料属性和平均剪应力的关联性,给出了该课题学术争议的合理解释。利用常见的三种不同金属材料的叠加平均剪应力纯扭疲劳实验数据,对比论证了新建预测模型与现有预测模型的差异。预测结果表明,新建预测模型预测精度明显优于现有模型。  相似文献   

8.
为了分析新一代光电子材料氧化镓晶体在超精密磨削、研磨加工过程中的裂纹成核位置及扩展方向,建立了单颗磨粒刻划氧化镓(010)晶面的弹性应力场模型,分析了氧化镓(010)晶面的脆塑性转变临界切削深度。通过MATLAB软件分析预测刻划氧化镓晶体过程中表面径向裂纹的成核位置及扩展方向,分析结果表明:当切削深度小于临界切削深度时,径向裂纹成核位置在磨粒的后方,裂纹扩展方向与切削方向之间的夹角在33°左右;当切削深度超过临界切削深度时,径向裂纹成核位置进一步向磨粒后方移动,裂纹生成方向与刻划方向之间的夹角在51°左右。为验证理论分析结果,对氧化镓晶体进行了纳米刻划试验,对比分析表明,氧化镓应力场的解析结果与试验数据高度一致。在线性加载条件下,Cube金刚石压头在氧化镓晶体(010)晶面上产生的径向裂纹偏转角在33.37°~51.45°之间。  相似文献   

9.
电缆摆杆不仅承受脱插、电缆的重力,而且还承受脱插脱落后的冲击载荷。文中利用UGNX4对电缆摆杆建模及有限元分析,并校核了电缆摆杆的强度刚度,在此基础上对其受到的冲击载荷进行了分析计算,利用此冲击载荷进行了强脱气缸缸座连接螺钉剪应力校核、钢丝绳强度校核及电缆摆杆锁紧机构受力校核,为电缆摆杆的设计开发提供了设计依据。  相似文献   

10.
带环向切口金属杆的扭转剪切断裂   总被引:1,自引:1,他引:0  
扭转圆杆的环向切口根部存在高度集中的剪切应力,Ⅲ型应力强度因子是裂纹端部应力场奇异性的度量.为探求带环向切口的受扭金属圆杆最大承载力的计算方法,通过对不同切口尺寸杆件的扭转剪切断裂实验,由各试件的预制切口尺寸和实验中测到的最大转矩分别计算相应的应力强度因子;利用非线性断裂理论推导出计算带环向切口裂纹扭转杆承载转矩的计算公式,将理论计算数值与实验结果进行比较,表明铸铁比碳钢试验结果更接近理论计算值.  相似文献   

11.
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...  相似文献   

12.
The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...  相似文献   

13.
黑棣  郑美茹 《机电工程》2016,(11):1315-1321
针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。  相似文献   

14.
马立新  王宏宇 《机电工程》2015,32(1):118-122
针对传统的电力系统多目标粒子群优化算法采用权重系数法将多目标转化为单目标,从而忽视了各目标函数间的竞争关系这一问题,提出将非支配解提取法运用到电力系统多目标无功优化中,并设定了一套提取规则,以电力系统中的有功网损、电压偏差和电压稳定裕度为目标,使目标在充分竞争的情况下得出Pareto最优解,利用IEEE-14节点系统对多目标非支配解提取法的电力系统无功优化进行了仿真测试。研究结果表明,该算法一次运行可以得出多组非支配解,既有偏向单个目标的解也有兼顾所有目标的解,克服了权重系数法的盲目性和单一性,可使电力决策者根据实际问题选择最优解,具有较好的灵活性与多样性。  相似文献   

15.
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.  相似文献   

16.
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....  相似文献   

17.
The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...  相似文献   

18.
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.  相似文献   

19.
This article describes designing, implementation and tuning processes of multiple-tapped-delay-line (MTDL). Obtained MTDL can be implemented in various field-programmable-logic-devices (FPGA) devices and applied for time-to-digital-converters (TDC) construction. The task of tuning process is the tapped-delay-line (TDL) linearisation, and consists of two stages. The first stage depends on selecting an appropriate configurable-logic-block (CLB) for particular delay-segment realization and selecting proper connection between these blocks. The second tuning stage, that is essential from this article viewpoint, depends on inter CLBs connecting wires delay regulation realized directly by load regulation. The Load regulation depends on connecting an appropriate number of unused three-state-buffers or CLB inputs to the wire which delay is adjusted. Depending on the number of inputs connected to the wire its capacitance changes that influences its time-constant and finally changes its time-delay.The MTDL mathematical model, obtained characteristics and results of time-interval (TI) measurements are also presented. The derived TDL model provides information about how the particular wire delay should be changed and in which order the changes should be executed. This makes the designing process predictable and easy to carry out. Presented characteristics confirm the proper operation of presented linearisation technique. The proper operation of the whole measuring module is confirmed by obtained TIs histograms presentation.  相似文献   

20.
Giannuzzi LA  Utlaut M 《Ultramicroscopy》2011,111(11):1564-1573
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.  相似文献   

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