这项工作得到了项目的支持: "Žilina 大学研究中心-2nd阶段", 斯洛伐克共和国教育部、科学和体育部的 ITMS 313011D011, 斯洛伐克科学院, 赠款号: 1/0045/17、1/0951/17 和 1/0123/15 和斯洛伐克研究开发署, 批准号。APVV-16-0276。

注: 每个试样的几何必须根据所测材料的力学和物理特性进行选择和计算, 使其具有与超声波检测系统相同的共振频率。

1. 疲劳试验试样尺寸的测定
注意:标准的 "沙漏" 拉伸-压缩试样几何具有定义的主尺寸, 如图 1所示。维度d、 d、和r是用户定义的 (独立), 而l和l维度必须根据正确的共振频率 (依赖) 的条件计算。标尺长度l仅在d、 r、和d、之间的几何比率中产生, 并且可以很容易地计算或从组件模型中获得;因此, 它不会成为进一步讨论的对象。
<ol><li>
独立尺寸的测定 注意:根据材料参数和测试条件选择试样的主要尺寸 (d、 d、 r)。<ol>
<li>根据所需的材料体积来确定测量直径d 。在无内部缺陷的均质显微组织情况下, 更倾向于使用较小的量规直径。对于具有很大内部缺陷的材料 (如铸造材料中的空隙和收缩), 需要更大的量规直径。标尺直径d通常从3毫米到5毫米。</li>
		<li>根据可用的实验材料大小确定头直径D 。使用的头直径D通常从10毫米到15毫米。 注意:D越大, 头长度 (L) 就越短。</li>
	</ol>
</li>
	<li>根据试样长度中所需的机械应力分布, 确定测量半径r 。规格直径为r越大, 机械应力分布越平滑。常用的测量半径为r = 20 毫米或r = 32 毫米。 注意:r越大, 样本就越长。</li>
	<li>
相关尺寸的测定
	<ol>
<li>根据以下公式9,18确定波形编号K : <img alt="Equation 1" src="/files/ftp_upload/57007/57007eq1.jpg"> 注意:这里的fr 是超声波系统 (Hz) 的共振频率, ρ是体积密度 (千克 m-3), Ed 是动态弹性模量 (千克 m-3)。</li>
		<li>根据下面的公式9,19, 确定测量半径的双曲逼近: <img alt="Equation 2" src="/files/ftp_upload/57007/57007eq2.jpg"> 注意:这里的l是标尺长度 (m), d是头直径 (m), D是标尺直径 (m) (图 1)。</li>
		<li>根据以下公式确定有效偏心度9,18: <img alt="Equation 3" src="/files/ftp_upload/57007/57007eq3.jpg"> 注意:这里的A是由等式 (2) 确定的双曲逼近 (m-1), K是根据表达式 (1) 确定的波形号 (-)。</li>
		<li>根据下面的公式9,18, 确定头的长度 (L): <img alt="Equation 4" src="/files/ftp_upload/57007/57007eq4.jpg"> 注意:这里的K是根据表达式 (1) 确定的波形号 (-), 在点1.2.1 中, β是由等式 (3) 确定的有效偏心 (m-1), 而l是标尺长度 (m) (图 1)。</li>
	</ol>
</li>
</ol>2. 试样长度的机械应力计算
<ol><li>根据以下公式确定规范几何因子<img alt="Equation 5" src="/files/ftp_upload/57007/57007eq5.jpg"> 918: <img alt="Equation 6" src="/files/ftp_upload/57007/57007eq6.jpg">
</li>
	<li>根据以下公式确定变形振幅ɛ9,18: <img alt="Equation 7" src="/files/ftp_upload/57007/57007eq7.jpg"> 注意:这里的是几何因子 (-), 而<img alt="Equation 5" src="/files/ftp_upload/57007/57007eq5.jpg"> u是试样 (m) 自由端所需的位移振幅。</li>
	<li>确定机械应力振幅σa根据以下等式9,18: <img alt="Equation 8" src="/files/ftp_upload/57007/57007eq8.jpg"> 注意:这里ɛ是根据表达式 (5) 确定的变形振幅 (-), Ed 是动态弹性模量 (千克 m-3)。如果计算的机械应力过低, 则需要增加位移振幅u (m), 反之亦然。</li>
</ol>3. 用加工工序制造试样
<ol><li>由于加工试样的各种小偏差从理想的形状, 制造标本用更长的头, 通常 L + 0.5 毫米。</li>
</ol>4. 用超声波系统协调试样的共振频率
注意:协调是从理想的、计算的形状中补偿真实试样的各种小偏差的过程, 得到正确的共振频率, 与超声声 sonotrode 相协调。
<ol><li>根据所需的位移范围选择合适的声学 sonotrode 类型, 在试样中能提供适当的机械应力。 注意:针对不同的位移范围设计和标定了每种类型的 sonotrode, 从而根据2节计算出的所需位移振幅选择合适的 sonotrode。</li>
	<li>
在压电变流器上安装 sonotrode。
	<ol>
<li>拧紧 sonotrode 中心孔内的连接螺钉, 直到它到达底部。</li>
		<li>在 sonotrode 表面传播声学凝胶。 注意:使用少量的凝胶, 刚好足以填补表面的不平顺, 这就改善了压电变流器和 sonotrode 之间的机械波的传递。</li>
		<li>将 sonotrode 拧入压电转换器中。</li>
	</ol>
</li>
	<li>用装有 sonotrode 的压电转换器运行超声波系统, 在实际温度下测量特定系统的共振频率。<ol>
<li>运行超声波测试软件 (例如, Win20k)。</li>
		<li>在 "模型" 框的下拉菜单中选择所用 sonotrode 的类型。</li>
		<li>输入 "振幅" 框中特定 sonotrode 的最小可能位移振幅。</li>
		<li>单击 "开始" 按钮。</li>
		<li>在 "频率" 框中读取系统的实际共振频率。</li>
		<li>单击 "停止" 按钮。</li>
	</ol>
</li>
	<li>在 sonotrode 的末端装上标本。<ol>
<li>将连接螺钉拧入试样的中心孔, 直到到达底部。</li>
		<li>把标本拧到 sonotrode 上。</li>
	</ol>
</li>
	<li>用装有 sonotrode 和试样的压电转换器运行超声波系统, 在实际温度下测量特定系统的共振频率。<ol>
<li>运行超声波检测软件。</li>
		<li>选择 "模型" 框中下拉菜单中使用的 sonotrode 类型。</li>
		<li>输入 "振幅" 框中特定 sonotrode 的最小可能位移振幅。</li>
		<li>单击 "开始" 按钮。</li>
		<li>在 "频率" 框中读取系统的实际共振频率。</li>
		<li>单击 "停止" 按钮。</li>
	</ol>
</li>
	<li>当装有试样的系统的共振频率低于无试样时, 通过切断试样头部的表面来减少试样的质量。 注意:如果带装入试样的共振频率较高, 则有必要减少测量直径d, 这将改变测试的条件。这就是 0.5 mm 被添加到制造过程中的头部长度的原因。<ol>
<li>从 sonotrode 中卸去标本。</li>
		<li>将试样装入车床, 并将头的0.1 毫米的脸向下翻转。</li>
		<li>将试样装入车床中, 并将第二头的表面的0.1 毫米翻转。</li>
		<li>重复步骤 4.6, 直到共振频率在10赫兹的耐受范围内。</li>
	</ol>
</li>
</ol>5. 试样在疲劳试验前的最后安装 Sonotrode
<ol><li>在脸部上应用声学凝胶, 在 sonotrode 和标本之间建立连接。<ol>
<li>将连接螺钉拧入试样的中心孔, 直到到达底部。</li>
		<li>将声学凝胶涂在试样表面。 注意:只有少量的声学凝胶用于填充表面的不规则, 以改善声波从 sonotrode 到试样的传输。</li>
		<li>把标本拧到 sonotrode 上。</li>
	</ol>
</li>
</ol>6. 运行试样冷却系统
<ol><li>如果使用空气冷却, 直接将气流集中在试样长度的中间, 等待大约二十年代, 气流流使试样饱和。</li>
	<li>如果使用水冷, 请将喷嘴放在试样顶部, 调整水流强度, 使水流沿轨距长度平稳地流动, 避免空化。 注意:将试样浸入水中或油中是可能的, 然而, 由于明显的空化效应, 这只能用于短时间试验, 加速了疲劳裂纹萌生过程。</li>
</ol>7. 运行压电变流器冷却系统
<ol><li>打开气流的阀门, 调整0.5 至1巴之间间隔的压力。</li>
</ol>8. 按所需位移振幅运行测试
<ol><li>运行超声波检测软件。</li>
	<li>在 "模型" 框的下拉菜单中选择所用 sonotrode 的类型。</li>
	<li>在 "振幅" 框中输入特定 sonotrode 的请求位移振幅。</li>
	<li>单击 "开始" 按钮。</li>
</ol>9. 疲劳裂纹的萌生和传播
<ol><li>观察到在疲劳裂纹萌生和通过部分截面的传播后, 系统被移出共振频率, 测试自然终止。</li>
	<li>如果测试不以断开结束, 在达到请求的加载周期数之后 (测试是一个耗尽的), 使用超声波测试软件中的 "停止" 按钮终止。</li>
</ol>10. 从 Sonotrode 中卸除标本
<ol><li>把样品从超声波 sonotrode 上拧下来。</li>
</ol>11. 静载力压裂
<ol><li>使用静态加载机, 用静态加载力来断开截面的其余部分。 注意:静力断裂载荷的矢量和类型应与疲劳载荷的类型相对应, 使断口具有一致的性质。</li>
</ol>

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我们没有什么可透露的。

超声疲劳试验是允许在超高循环区进行结构材料测试的几种方法之一。然而, 在共振频率方面, 试样的形状和尺寸是非常有限的。例如, 在轴向加载模式下的薄板的测试一般是不可能的。此外, 大型试样的测试通常是不可能的, 因为测试机器没有提供这样的功率, 它需要设计一个特殊的超声波系统。
即使现代超声波发生器能够对超声波进行调制, 并成功地共振具有细微不同尺寸的...

结构材料的疲劳损伤与工业化有着密切的联系, 主要是利用蒸汽发动机和蒸汽机车进行铁路运输, 其中大量的金属部件, 主要以铁为主, 已被使用并承受各种循环加载的类型。最早的一次测试是由阿尔伯特 (德国 1829)1在矿井提升机的焊接链上进行的。加载频率为每分钟10弯, 所记录的最大测试达到10万加载周期1。另一项重要工作是由威廉费尔贝恩在1864年进行的。在锻铁梁上进行了试验, 使用静态载荷, 通过杠杆提升, 然后下降造成振动。荷载作用下, 梁的加载应力幅度逐渐增大。在对各种荷载应力振幅进行了上千次循环后, 最终梁在大约5000加载周期的载荷振幅2/5 的极限抗拉强度的情况下失败。8月弗里德里希·维勒在 1860-18701中首次对结构材料的反复应力影响进行了全面系统的研究。对于这些测试, 他使用扭力, 弯曲和轴向加载模式。弗里德里希·维勒设计了许多独特的疲劳试验机, 但他们的缺点是低操作速度, 例如最快的旋转折弯机操作在 72 rpm (1.2 Hz), 因而实验程序的完成花费了12年1。在进行这些测试之后, 人们认为, 在达到材料承受 107周期的加载振幅后, 疲劳退化是微不足道的, 材料可以经受无限数量的加载周期。这一加载幅值被命名为 "疲劳极限", 并成为多年工业设计的主要参数2,3。
进一步开发新的工业机器, 需要更高的效率和成本节约, 必须提供更高的负载, 更高的运行速度, 更高的工期, 高可靠性和低维护要求的可能性。例如, 高速列车 Shinkanzen 的组件经过10年的运行后, 必须承受大约10个9循环, 主组件的故障可能会产生致命后果4。此外, 喷气引擎的部件通常运行在 1.2万 rpm, 涡轮鼓风机的组件往往超过 1.7万 rpm。这些高操作速度增加了在所谓的超高循环区域的疲劳寿命测试的要求, 并评估了材料的疲劳强度是否真的被认为是恒定的超过1000万个周期。在第一次试验超过了这种耐力后, 很明显, 即使在应用应力振幅低于疲劳极限的情况下, 疲劳失效也会发生, 在许多循环超过 107之后, 损伤和破坏机制可能与通常的5不同。
创建一个旨在调查超高循环区域的疲劳测试程序, 需要开发新的测试设备以强烈增加加载频率。1998年6月在巴黎举行了一次专题讨论会, 该研讨会的实验结果是由 Stanzl-Tschegg6和 Bathias7在20赫加载频率下获得的, 由里奇8使用1赫闭环伺服液压试验机, 并由戴维森8与1.5 赫磁 strictive 测试机4。从那时起, 许多解决方案被提出, 但仍然最常用的机器为这类测试是基于曼森的概念从1950年和使用频率接近20赫9。这些机器在应变率、周期数的确定精度和疲劳试验的时间 (1010周期达到大约6天) 之间表现出良好的平衡。其他设备能提供更高的装载频率, 象 Girald 使用的一个在 1959年-92 赫和菊在 1965年-199 赫;然而, 这些很少被使用, 因为它们造成极高的变形率, 而且, 由于测试只持续了几分钟, 预计周期计数的一个显著误差。影响疲劳试验的共振器件加载频率的另一个重要因素是试样的尺寸, 它与共振频率直接相关。所要求的加载频率越大, 试样越小。这就是为什么40赫以上的频率很少使用10的原因。
由于位移振幅通常限制在3和80µm 之间的间隔内, 所以超声波疲劳测试可以成功地应用于大多数金属材料, 尽管在高分子材料 (如 PMMA11 ) 的测试技术和此外, 还开发了复合材料12 。一般情况下, 超声波疲劳试验可以在轴向加载模式下执行: 拉伸压缩对称循环13,14, 张力-张力周期15, 三点弯曲15, 还有一些研究与系统的特别修改为扭力测试15,16和双轴弯曲17。这是不可能使用任意标本, 因为对于这种方法, 几何是严格的关系, 以达到共振频率的20赫。对于轴向载荷, 几种类型的试样已被常用, 通常有一个小时玻璃形状与规格长度直径从3到5毫米。对于三点弯曲, 薄板是常用的, 为其他方法设计了特殊类型的试样, 根据方法类型和测试条件。该方法设计用于评价高、超高循环区域的疲劳寿命, 这意味着在五十年代获得20赫负载, 100万个周期;因此, 这通常被认为是负荷周期的下限, 可以用合理的精度来研究, 关于周期确定的数量。每个试样必须通过改变试样的质量来与超声波喇叭协调, 以提供系统的正确共振频率: 带试样的超声波喇叭。

<table border="0" cellpadding="0" cellspacing="0" width="665">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ultrasonic fatigue testing device</td>
			<td style="width:71px;">Lasur</td>
			<td style="width:119px;">-</td>
			<td style="width:259px;">20 kHz, used for fatigue tests</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Nyogel 783</td>
			<td style="width:71px;">Nye Lubricants</td>
			<td style="width:119px;">-</td>
			<td>Used as acoustic gel for connection of the parts of the ultrasonic system</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Win 20k software</td>
			<td style="width:71px;">Lasur</td>
			<td style="width:119px;">-</td>
			<td>Software for operation of the Lasur fatigue testing machine</td>
		</tr>
	</tbody>
</table>

ultrasonic fatigue testing in the tension-compression mode

超声疲劳试验是研究超高循环区域疲劳性能的几种方法之一。该方法的基础是将试样暴露在共振频率接近20赫的纵向振动上。使用此方法, 可以大大减少测试所需的时间, 与通常工作在200赫兹以下频率的常规测试设备相比。它也被用来模拟在运行中的材料加载在高速条件下, 如那些由喷气引擎或汽车涡轮泵的组件经验。由于极高的变形速率可能会对试验结果产生显著影响, 因此必须在高、超高循环区内进行操作。试样的形状和尺寸必须经过仔细的选择和计算, 以满足超声系统的共振条件;因此, 不可能对任意形状的完整元件或试样进行测试。在每次试验前, 必须将试样与超声波系统的频率进行协调, 以补偿实际形状与理想的偏差。这是不可能的, 直到一个完全断裂的标本, 因为测试是自动终止后, 裂纹的启动和传播到一定的长度, 当系统的刚度改变足以转移系统的共振频率.本文介绍了在高频超声疲劳载荷作用下, 利用近20赫频率的机械共振来评价材料疲劳性能的过程。该协议包括对正确测试所需的所有步骤的详细描述, 包括试样设计、应力计算、与共振频率的协调、执行测试和最终的静态断裂。

疲劳试验结果包括加载应力、加载周期数和测试终止字符 (断开或耗尽) 可以在表 1中看到, 其中提供了50CrMo4 淬火和回火钢的疲劳寿命结果。对疲劳寿命试验结果最常见的解释是所谓的 s-N 地块 (s 应力, N-周期数), 也称为弗里德里希·维勒的剧情。疲劳寿命对施加载荷应力的依赖性在历史上给定的倒轴图中绘制, 其中独立值 (加载应力) 位于y轴上, 而相关值 ...

Watch this Scientific Journal Video about Ultrasonic Fatigue Testing in the Tension-Compression Mode at JoVE.com

Ultrasonic Fatigue Testing in the Tension-Compression Mode

一种在高超高循环区域轴向拉压加载模式下的超声疲劳试验协议。

拉伸压缩模式下的超声疲劳试验

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...

ultrasonic-fatigue-testing-in-the-tension-compression-mode

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10.6K 次观看.  University of Žilina. 一种在高超高循环区域轴向拉压加载模式下的超声疲劳试验协议。

视频: Ultrasonic Fatigue Testing in the Tension-Compression Mode

Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The optical modes are frequently referred to as "whispering gallery modes" (WGM) or "morphology dependent resonances" (MDR) and exhibit high optical quality factors. Some proposed applications of micro-cavity optical resonators are in spectroscopy1, micro-cavity laser technology2, optical communications3-6 as well as sensor technology. The WGM-based sensor applications include those in biology7, trace gas detection8, and impurity detection in liquids9. Mechanical sensors based on microsphere resonators have also been proposed, including those for force10,11, pressure12, acceleration13 and wall shear stress14. In the present, we demonstrate a WGM-based electric field sensor, which builds on our previous studies15,16. A candidate application of this sensor is in the detection of neuronal action potential.
The electric field sensor is based on polymeric multi-layered dielectric microspheres. The external electric field induces surface and body forces on the spheres (electrostriction effect) leading to elastic deformation. This change in the morphology of the spheres, leads to shifts in the WGM. The electric field-induced WGM shifts are interrogated by exciting the optical modes of the spheres by laser light. Light from a distributed feedback (DFB) laser (nominal wavelength of ~ 1.3 &mu;m) is side-coupled into the microspheres using a tapered section of a single mode optical fiber. The base material of the spheres is polydimethylsiloxane (PDMS). Three microsphere geometries are used: (1) PDMS sphere with a 60:1 volumetric ratio of base-to-curing agent mixture, (2) multi layer sphere with 60:1 PDMS core, in order to increase the dielectric constant of the sphere, a middle layer of 60:1 PDMS that is mixed with varying amounts (2% to 10% by volume) of barium titanate and an outer layer of 60:1 PDMS and (3) solid silica sphere coated with a thin layer of uncured PDMS base. In each type of sensor, laser light from the tapered fiber is coupled into the outermost layer that provides high optical quality factor WGM (Q ~ 106). The microspheres are poled for several hours at electric fields of ~ 1 MV/m to increase their sensitivity to electric field.

A high-sensitivity photonic micro sensor was developed for electric field detection. The sensor exploits the optical modes of a dielectric sphere. Changes in the external electric field perturb the sphere morphology leading to shifts in its optical modes. The electric field strength is measured by monitoring these optical shifts.

回音壁模式聚合物微光学电场传感器的发展

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The ...

科研

工程学

Microwave Photonics Systems Based on Whispering-gallery-mode Resonators

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency.

The customized techniques developed in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators are presented. The protocols to obtain and characterize these resonators are detailed, and an explanation of some of their applications in microwave photonics is given.

基于微波光子系统回音壁模式谐振器

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various ...

Fabrication of VB2/Air Cells for Electrochemical Testing

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.

Fabrication of VB2/Air Cells for Electrochemical Testing

A protocol is presented to study multi-electron metal/air battery systems by using previous technology developed for the zinc/air cell. Electrochemical testing is then performed on fabricated batteries to evaluate performance.

VB制作<sub&gt; 2</sub&gt; /空气电池电化学测试

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for ...

Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

使用超声波润滑实验一压电辅助摩擦试验机和光学轮廓

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at ...

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints.

A straightforward procedure for ultrasonic welding of thermoplastic composite coupons for basic mechanical testing is described. Key characteristics of this ultrasonic welding process are the use of flat energy directors for simplified process preparation and the use of process data for the fast definition of optimum processing conditions.

通过单搭接剪切试验的热塑性复合材料优惠券焊接接头的力学特性的超声波焊接

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

锁模自动化的非线性偏振旋转光纤激光器通过输出偏振测量

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Characterization of Anisotropic Leaky Mode Modulators for Holovideo

Holovideo displays are based on light-bending spatial light modulators. One such spatial light modulator is the anisotropic leaky mode modulator. This modulator is particularly well suited for holographic video experimentation as it is relatively simple and inexpensive to fabricate1-3. Some additional advantages of leaky mode devices include: large aggregate bandwidth, polarization separation of signal light from noise, large angular deflection and frequency control of color1. In order to realize these advantages, it is necessary to be able to adequately characterize these devices as their operation is strongly dependent on waveguide and transducer parameters4. To characterize the modulators, the authors use a commercial prism coupler as well as a custom characterization apparatus to identify guided modes, calculate waveguide thickness and finally to map the device's frequency input and angular output of leaky mode modulators. This work gives a detailed description of the measurement and characterization of leaky mode modulators suitable for full-color holographic video.

This work describes fabrication and characterization of anisotropic leaky mode modulators for holographic video.

各向异性泄漏模式调制器用于Holovideo的表征

Holovideo displays are based on light-bending spatial light modulators.  One such spatial light modulator is the anisotropic leaky mode modulator.  This ...

Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres can be thought as a store of energy with a huge variety of applications: compact laser sources, highly sensitive biochemical sensors and nonlinear phenomena. A protocol for the fabrication of both the microspheres and coupling system is given. The couplers described here are tapered fibers. Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility &#935;(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS). A proof of the cavity-enhanced phenomenon is given by the lack of correlation among the pump, signal and idler: a resonant mode has to exist in order to obtain the pair of signal and idler. In the case of hyperparametric oscillations (four wave mixing and stimulated anti-stokes Raman scattering), the modes must fulfill the energy and momentum conservation and, last but not least, have a good spatial overlap.

Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility &#935;(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS).

刺激斯托克斯和反斯托克斯拉曼散射在微球形回音壁模式谐振器

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

使用激光投射光热法构造加热的地下缺陷定位

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is known about the effects of high pressure hydrogen on the polymer sealing and barrier materials also found within these components. More study is required in order to determine the compatibility of common polymer materials found in the components of the hydrogen fuel delivery infrastructure with high pressure hydrogen. As a result, it is important to consider the changes in physical properties such as friction and wear in situ while the polymer is exposed to high pressure hydrogen. In this protocol, we present a method for testing the friction and wear properties of ethylene propylene diene monomer (EPDM) elastomer samples in a 28 MPa high pressure hydrogen environment using a custom-built in situ pin-on-flat linear reciprocating tribometer. Representative results from this testing are presented which indicate that the coefficient of friction between the EPDM sample coupon and steel counter surface is increased in high pressure hydrogen as compared to the coefficient of friction similarly measured in ambient air.

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

A test methodology for quantifying tribological properties of polymers used in hydrogen infrastructure service is demonstrated and characteristic results for a common elastomer are discussed.

就地氢气输送基础设施用普通高分子材料的高压氢摩擦学试验

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is ...