Acoustic wave-based sensors using mode conversion in periodic gratings

Using periodic gratings etched into the surface of a piezoelectric plate, surface acoustic waves (SAW) can be converted into bulk waves and vice versa with high efficiency. If parallel grating structures are fabricated on opposite surfaces of a piezoelectric plate, a SAW also can be directed from one surface to the other. Using such structures, acoustic wave-based sensors can be designed that utilize SAW for the detection of chemical analytes on an electrode-free surface, i.e., the back surface. As a result, spurious sensor response and electrode aging that may occur when a chemical analyte comes in contact with the transducers are minimized. The design principles of these grating-based SAW sensors are explained, and the mass sensitivity is investigated using chemical vapor deposited thin polymer films, a type of material used in many practical chemical sensor applications. Experimental results are presented for the detection of nitrogen dioxide (NO(2 )) in sub-ppm concentrations.     

弯矩载荷作用下偏梯形套管连接螺纹参量敏感性分析

井眼弯曲段的套管在承受常规载荷的同时还要承受弯矩载荷作用, 因此导致弯曲段套管连接螺纹失效率较直井段要高, 然而目前对套管连接螺纹在弯矩载荷作用下的力学行为认识尚不明确。针对该问题, 该文基于虚功原理、接触非线性理论及Von Mises 屈服准则, 运用有限元分析软件建立并计算了弯矩载荷作用下套管连接螺纹的三维力学模型, 获得了套管连接螺纹的应力分布规律, 并用实验结果与数值模拟结果对比验证了模型的有效性;在此基础上对螺纹锥度、承载面角度、导向面角度、齿高及螺距五个螺纹参量进行了敏感性分析, 最后总结了弯矩载荷作用下各螺纹参量对其应力分布的影响规律。该文的研究工作为套管偏梯形连接螺纹的优化设计提供了科学依据, 对减少套管连接螺纹失效具有重要的工程价值。     

试验机压辊断裂原因分析

在对10CrNi4MoV钢原始态焊缝板状试样进行四点弯曲疲劳试验的过程中,试验机一上压辊发生了断裂。分别从压辊的材质、受力状态和断口形貌等方面对压辊的断裂原因进行了分析。结果表明：压辊发生断裂是因为试验中改变了压辊设计时的受力状态,使得压辊薄弱部位产生了应力集中,在外载荷周期作用下,最终成为疲劳裂纹源,加之压辊材料对裂纹比较敏感,最终导致了疲劳断裂。提出了重新设计压辊时应采取的措施。     

Development of disc bending fatigue test technique for equi-biaxial loading

The disc bending fatigue test technique was developed to investigate the fatigue life under an equi-biaxial loading condition. In this test, a uniform thickness disc specimen was subjected to a bending load by applying air pressure on the specimen surface. Eleven specimens made of Type 316 stainless steel were tested in a room temperature ambient environment. The crack initiation and growth behaviors during the test were observed through a transparent window. The fatigue life was defined when the peak pressure measured near the specimen surface was reduced to 95% of the supplied air pressure. The fatigue life obtained by the disc bending fatigue test was shorter than that obtained by the uniaxial and plate bending fatigue tests for the same principal strain range. It was confirmed that the equi-biaxial loading condition reduced the fatigue life. The finite element analysis together with test results revealed that the crack was initiated at the edge of the specimen when the specimen thickness was less than 1.0 mm. The specimen thickness should be 1.2 mm in order to maximize the strain range at the specimen center. It was concluded that the disc bending fatigue test can derive the fatigue life under an equi-biaxial loading condition, for which strain range is measured at the specimen center.     

Nonlinear thermal bending response of FGM plates due to heat conduction

Nonlinear thermal bending analysis is presented for a simply supported, shear deformable functionally graded plate without or with piezoelectric actuators subjected to the combined action of thermal and electrical loads. Heat conduction and temperature-dependent material properties are both taken into account. The temperature field considered is assumed to be a uniform distribution over the plate surface and varied in the thickness direction and the electric field considered only has non-zero-valued component E_Z. The material properties of functionally graded materials (FGMs) are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents, and the material properties of both FGM and piezoelectric layers are assumed to be temperature-dependent. The governing equations of an FGM plate are based on a higher order shear deformation plate theory that includes thermo-piezoelectric effects. A two step perturbation technique is employed to determine the thermal load–deflection and thermal load–bending moment curves. The numerical illustrations concern nonlinear bending response of FGM plates without or with surface bonded piezoelectric actuators due to heat conduction and under different sets of electric loading conditions. The results reveal that for the case of heat conduction the nonlinear thermal bending responses are quite different to those of FGM plates subjected to transverse mechanical loads, and the temperature-dependency of FGMs could not be neglected in the thermal bending analysis.     

"利乐包"塑木托盘的有限元分析

采用塑木挤出成型技术,将打碎的"利乐包"挤压成型,选择其板材加工成托盘。根据林派检测报告相关数据:弹性模量、静曲强度以及塑木材料弯曲强度,基于ANSYS有限元分析软件,对托盘板材在静态承重与叉车叉起时的力学性能和承载性能进行分析。结果表明:1.1 t的承载下,板材不会开裂,满足实际使用要求。     

动物骨折治疗用金属骨板局部增量成形新工艺

目的目前动物骨折常用的锁定骨板内固定技术(Point-contact Reconstruction Compress Locking, PRCL)需要采用多个工具配合手动完成骨板成形,针对该过程中精度不可控、效率低等问题,提出一种弯扭复合成形模具,发展一种局部增量成形金属骨板的方法。方法 PRCL骨板固定治疗中,为了贴合受伤骨骼,治疗前骨板需经过面内弯曲、弯曲以及扭转3类变形。通过调整弯扭复合成形模具的空间位置及模具不同组成部分的相对位置,实现不同区域内不同变形量的面内弯曲、弯曲或扭转。应用数值方法分析验证弯扭复合成形模具及成形方法的适用性,基于DEFORM软件建立工业纯钛TA2骨板局部增量成形过程有限元模型,分析具有两个成形区的TA2骨板局部增量成形特征。结果塑性变形仅发生在复合模具附近,对已变形区无影响,会引起未成形区的刚性位移;骨板长度方向受力小于其宽度和厚度方向受力,面内弯曲需要较大的成形载荷。结论所发展的模具和方法可实现预期的骨板成形,也适用于其他PRCL金属骨板的成形。     

Micromechanical precision pressure sensor incorporating SAW delay lines

Summary We have developed a wireless surface acoustic wave (SAW) pressure sensor operating in the pressure range of 0 Pa to 250 kPa. In order to minimize the temperature sensitivity the pressure sensor is made of on an all-quartz package (AQP), which has been designed with the Finite Element Method. The package of the pressure sensor consists of a diaphragm and a cover, both made of conventional Y-cut quartz. A blind-hole was structured into the sensor cover. By attaching the cover and the diaphragm with an epoxy-adhesive, this blind-hole forms a closed cavity. The SAW element is a reflective delay line (RDL), working at 434 MHz. The RDL consists of ten reflectors and extends over the whole diaphragm. The pressure is determined by evaluating the change of the carrier phase shifts of the reflected impulses at the reflectors. We show that it is possible to minimize the temperature sensitivity and to achieve good linearity by proper positioning of the SAW reflectors. The measurements of the SAW pressure sensor show a deviation from linearity of less than ±0,7%. The temperature dependence is almost negligible in the range from-20°C to 100°C.The objective of this paper is to provide a deeper insight into the behaviour of SAW propagation on pre-stressed substrates. To do so, we start with investigating the behavior of SAWs on stress-free substrates followed by an analysis of SAW propagation on pre-stressed substrates. Further, the requirements on suitable substrate materials for the AQP are specified. Finally, we take advantage of the method of differences to compensate for the temperature dependence of our pressure sensor.     

Analysis of stationary deformation behavior of a semi-infinite rigid-perfect plastic beam subjected to moving distributed loads of finite width

The problem of projection of a flyer plate with a traveling distributed load and subsequent collision of it to a base plate, as applied to explosive welding, is addressed in this paper. A semi-infinite solid-perfectly plastic beam is employed to model the flyer plate subject to two transverse pressure profiles, traveling at constant speed on its top and bottom surfaces, which represent the explosion and collision loads, respectively. A steady state deformation process is considered and the analysis is developed for the pure bending and combined shear and bending deformation conditions. It follows from analysis that two plastic bending hinges form ahead and at the rear end of each pressure profile and travel at constant velocity. Furthermore, when the width of the pressure is small, the shearing deformation region is generated within the loaded area. The state of the deformation in the collision stage in contrast to the propulsion stage is discussed.     

高阶剪切变形板理论下FG-GRC板的屈曲和弯曲分析

基于三阶剪切变形板理论(TSDPT)和正弦剪切变形板理论(SSDPT),研究了功能梯度石墨烯增强复合材料(FG-GRC)板的屈曲和弯曲行为,并通过与一阶剪切变形板理论(FSDPT)计算结果的比较,分析了TSDPT、SSDPT与FSDPT在FG-GRC板屈曲和弯曲力学行为研究过程中的差异。材料的有效杨氏模量通过修正的Halpin-Tsai微观力学模型估算,有效泊松比通过混合律确定。利用最小势能原理推导出了包含五个未知量的控制方程,并获得了简支FG-GRC矩形板弯曲挠度和临界屈曲载荷Navier形式的解析解。数值结果表明：与TSDPT和SSDPT相比,FSDPT明显高估了FG-X型FG-GRC板的临界屈曲载荷而明显低估了其弯曲挠度,且略微低估了FG-O型FG-GRC板的临界屈曲载荷而略微高估了其弯曲挠度,而UD型和FG-A型FG-GRC板在三种理论下的计算结果几乎完全一致;TSDPT和SSDPT在计算FG-GRC板的弯曲挠度和临界屈曲载荷时结果十分相近;当板的总层数NL小于10层～15层时,弯曲载荷比率和临界屈曲载荷比率的变化非常显著,当总层数NL超过10层～15层时,弯曲载荷比率和临界屈...     

钢‒CFRP异质复合B柱的弯曲实验分析

目的 为提高B柱的抗弯性能,通常会在B柱上额外焊接补丁板,但同时也增加了B柱的重量。在原始B柱上铺设碳纤维增强复合材料(CFRP),获得钢?CFRP异质复合B柱,取消B柱的钢制加强板,实现B柱的轻量化。方法 通过热冲压制备原始B柱及带补丁板B柱,并以原始B柱为凹模,采用真空袋压工艺制备钢?CFRP异质复合B柱。基于2018版C?NCAP侧面碰撞实验要求,设计B柱三点弯曲夹具,进行原始B柱、带补丁板B柱及钢?CFRP异质复合B柱的三点弯曲实验,并对其重量及弯曲性能进行分析。结果 原始B柱重量4.1 kg,三点弯曲实验测得其刚度为0.763 kN/mm,最大载荷为21.59 kN,平均力为14.52 kN;带补丁板B柱质量为5.6 kg,三点弯曲实验测得其刚度为1.095 kN/mm,最大载荷为31.08 kN,平均力为18.38 kN;钢?CFRP异质复合B柱总质量4.7 kg,三点弯曲试验测得其刚度为1.071 kN/mm,最大载荷为31.76 kN,平均力为19.58 kN。结论 在保持刚度、最大载荷及平均力等弯曲力学性能不变的前提下,相对于带补丁板B柱,钢?CFRP异质复合B柱可以减轻质量0.9 kg,并且吸能更优,实现了B柱的轻量化。     

基于模型试验的船-冰碰撞载荷空间分布演变历程研究

针对船-冰碰撞载荷空间分布的演变历程,通过一系列的冰水池模型试验,分别从"整体"与"局部"的角度,对船-冰碰撞载荷沿船体表面的空间移动轨迹,及局部冰压力空间分布形态随时间的变化过程进行了研究。结果表明:船-冰碰撞过程中的冰载荷沿船体外板的整体作用呈现出近抛物线的轨迹;同时,冰压力的局部空间分布也呈现出与冰载荷时程曲线中"峰-谷"循环波动特征相对应的"单-双"高压力区周期性的动态演变过程,极端冰载荷只存在于"单高压力区"型的局部空间分布形态下。基于多个载荷板对船-冰接触轨迹进行覆盖的理念,提出一种移动冰载荷的构建方法。相邻载荷板之间的载荷时程存在重叠以更好地模拟载荷的空间"移动",而各载荷板上的非均布冰压力则通过高斯函数进行拟合。     

Pressure and flow in fluid films constrained between translating and vibrating flexible surfaces

In this paper, the dynamic pressure and flow developed in a two-dimensional, viscous fluid film constrained between flexible surfaces are analyzed. The problem formulation assumes that the response of the flexible surface is governed by linear equations of motion, and the fluid motion is governed by linearized momentum equations including the unsteady inertia. Three states of the model are developed to describe the coupled fluid-structural response problem. The fluid dynamic pressure is derived in the frequency domain as a function of the fluid impedances and the surface transverse vibrations. The perturbed, coupled problem is described by an integral equation (in state vector form) that governs the coupled responses of the flexible surfaces. The integral equation is solved by a discretization method. The analysis is applied to a rigid slider bearing with a flexible, translating plate surface under the excitation of a harmonic point load. The accuracy of the discretization method is evaluated, and numerical results for the dynamic pressure and the plate response are presented.     

纤维增强复合材料波纹蒙皮基体的承载能力

本文以一种可作为变体机翼蒙皮的复合材料波纹结构为对象,研究了其横向承载能力,为其结构参数优化提供理论基础。提出了一个理论分析模型,计算了试件横向的抗弯刚度及三点弯曲载荷下的挠曲线,并计算了同等材料厚度、宽度的平板结构的抗弯刚度,比较发现,波纹结构在纵向有远大于平板结构的承载能力。模仿蒙皮实际受载情况,计算了均布载荷作用下波纹试件弯曲的挠曲线方程。制作了波纹基体承载试件及平板试件,用三点弯曲法对两种试件进行了弯曲测试,测试结果表明,在弯曲的弹性变形段内,理论计算值与测试值基本吻合,误差小于10%,证明了理论分析模型的正确性。     

水面上弹性浮板在外载荷作用下的动力学特性研究

基于线性水波理论和Mindlin厚板动力学理论,采用Wiener-Hopf方法,研究了水面上浮动弹性平板局部受动载荷(周期分布载荷)作用下的动力学特性。首先将分析计算结果与采用其他方法得到的计算结果进行了对比和分析;其次,采用本文方法研究了三种周期载荷激励下浮板上挠度和动弯矩幅值的分布情况;最后,对浮板挠度幅值分布与不同周期载荷的中心位置及其分布宽度的关系进行了研究。     

Two-way bending behavior of 3-D GFRP sandwich panels with through-thickness fiber insertions

This paper presents the details of a research program that was conducted to evaluate the two-way bending behavior of 3-D glass fiber reinforced polymer (GFRP) sandwich panels. The panels consist of GFRP skins with a foam core and through-thickness fiber insertions. While the behavior of these panels under one-way bending is relatively well understood the behavior under two-way bending has not yet been investigated. An experimental program was conducted to evaluate the effect of the fiber insertion pattern and the panel thickness on the two-way bending behavior under the effect of a concentrated load. The experimental results were used to verify a non-linear, static finite element model which was used to introduce a simplified method to predict the behavior. The measured and predicted responses indicate that at lower deflections the panel behavior is dominated by plate bending action while for higher deflections membrane action dominates. The finite element analysis was extended to study the effect of different parameters which were not tested in the experimental program. The parametric study indicates that increasing the relative flexural or shear rigidities of the panel alters the behavior towards the plate bending mechanism thereby reducing the percentage of load carried by membrane action.     

多次水下爆炸作用下钢板与焊接钢板冲击损伤特性

为了研究舰船结构在多次水下爆炸载荷作用下的抗爆抗冲击能力,基于水下爆炸鼓胀试验分别开展了5 mm、12 mm的船用A32背空钢板及焊接板的多次水下爆炸试验,得到了钢板与焊接板的塑性变形历程,测量并计算了钢板与焊接板受冲击区域沿半径各点处的挠度及厚度减薄率,分析了钢板与焊接板的塑性变形规律。结果表明:多次水下爆炸载荷作用下,焊接板与钢板的塑性变形形貌呈类球冠形,二者的厚度减薄率从中心位置到边界处呈先减小再增大的趋势,但焊接板的挠度小于钢板的挠度。A32钢板的变形模式主要为弯曲和拉伸变形,焊接板以弯曲变形为主。持续增加的水下爆炸载荷导致钢板中心位置与边界处拉伸断裂,而焊接板的焊缝及其热影响区发生脆性断裂。     

Bending of simply-supported,antisymmetrically laminated rectangular plate under transverse loading

The deformation of antisymmetric angle-ply laminated plate under transverse loading is analysed using the bending theory of laminated plate presented by Ren.^1,2 By expanding the load in a double Fourier series, a closed-form solution is obtained for special types of simply-supported boundary condition. The results are compared with similar results from the classical laminated plate theory and Mindlin theory. This shows that the theory presented by Ren is suitable not only for cylindrical bending but also for general bending problems.     

基于高阶剪切理论的复合材料格栅夹层板弯曲特性

基于高阶剪切弯曲理论,对含有软质芯材的复合材料格栅夹层板的弯曲特性进行了理论研究。基于能量法,推导了含有软质芯材的复合材料格栅的等效弹性参数计算式;基于高阶剪切弯曲理论,推导了夹层板的弯曲平衡微分方程,并采用Navier方法,给出了分布载荷作用下四边简支、上下表层为对称正交铺层的夹层板弯曲问题的理论解;用算例对典型格栅夹层板的理论解和有限元仿真解进行了对比,两者误差为7.1%,验证了本文理论方法的正确性;并分析了夹层板跨厚比、格栅厚度、格栅复合材料铺层角度、格栅间距等参量对含有软质芯材的典型复合材料格栅夹层板弯曲挠度的影响规律。      

基于激光激发声表面波新型气体传感器的研究

提出了一种利用激光激发声表面波,通过气体吸附性薄膜对被测气体进行检测的传感原理.激光在覆有选择性气体吸附膜的铝块表面激发出声表面波,后者沿铝块表面传播.在吸附性薄膜与被测气体发生反应后,声表面波的强度被改变;然后利用PMT(光电倍增管),通过单芯光纤耦合的反射式光束偏转法探测由半导体激光器发出的探测光束,所检测的光强的变化反映了被检测气体的浓度,从而实现被测气体的浓度测量.