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Nondestructive Testing and Evaluation Methods for Composite Hydrogen Tanks 复合材料储氢罐无损检测与评价方法
发布日期: 2008-11-01
本报告包括对用于气态氢基础设施应用的复合材料包覆压力容器的各种无损评估(NDE)技术的研究。大部分研究集中在模型声发射(MAE)技术上。对各种复合储罐设计进行了测试,包括设计用于便携式、固定式或车载储存的小型高压塑料内衬全包裹复合压力容器,以及设计用于散装运输和固定储存的大型钢衬环包裹压力容器。MAE测试由Digital Wave Corp.执行。 林肯复合材料公司和TransCanada公司提供的船只上。2007年4月,林肯工厂对林肯复合材料塑料内衬全包裹10000 psi复合材料压力容器进行了MAE测试。通过钻孔、薄膜切割和跌落试验模拟储罐损坏,随后进行验证和爆破试验,同时使用MAE技术进行监测。MAE确认了制造一致性。一般而言,观察到这些船只在受损地点发生故障。贯穿复合材料的钻孔产生的爆破压力最低,其次是6.5%的冲击- 滴到混凝土上,最后切下纤维。损伤发生后,MAE在第一次加压时很好地拾取了新引入的损伤。排放没有完全稳定下来,这表明在压力保持期间,损害确实继续增加。在更高的灵敏度设置下,MAE摩擦发射(FRAE)在损伤后的每个循环中都被检测到。使用MAE技术,损伤位置在声学上非常清晰。 2007年10月,对六个TransCanada大型钢衬环包裹复合材料压力容器进行了MAE测试。试验程序包括循环试验、压力/自增强试验和爆破试验,同时使用MAE技术进行监测。 在循环试验期间,在容器两端的金属封头至壳体焊缝中检测到裂纹扩展。由于该裂纹导致疲劳失效之前持续的循环次数超过了所需的10000次循环。这是由泄漏源产生的声音信号确定的。在压力(自增强)试验期间,累积事件-时间曲线显示出一个特征?翻滚?在所有情况下,AE测试中的压力负荷保持不变。在负载保持期间,事件很少或没有,在AE测试期间,事件很少。这与断裂力学推理一致,因为AE试验压力远低于自增强压力。 有人观察到,在1.5倍工作压力下的自增强循环(用于AE检测)将限制在1.1倍工作压力下的AE循环。这一结论与之前在各种其他压力容器上的经验一致。2008年2月,Digital Wave Corp.对由压电材料聚偏二乙烯薄膜(PVDF)构成的MAE传感器阵列进行了研究和实验室测试。本研究着眼于两种提高PVDF薄膜传感器灵敏度的方法,1)传感器堆叠和传感器输出的模拟求和,以及2)传感器输出的数字求和。 据观察,堆叠传感器提高了检测灵敏度,没有因堆叠而产生的相位失真,减小传感器尺寸可以减少孔径影响并增加带宽。用于模态声发射(MAE)的相控阵配置可以确定声源的方向,并可能确定距离。源位置信号的相位调整是可能的,并有助于模式识别和源位置,这对到达时间差的变化非常敏感。传感器的布置也非常重要,必须研究对阵列几何形状的敏感性。本报告还包括对其他相关NDE和分析技术的额外讨论,包括对复合材料储罐水压试验要求的研究、对复合材料增强压力容器的有限元分析(FEA)和断裂力学分析,预测试验期间观察到的故障,并使用声发射技术进行指示,以及对光子诱导正电子湮没(PIPA)的讨论,PIPA是一种潜在的无损检测过程,可以在近距离评估材料损伤- 分子水平。
This report includes a study of various nondestructive evaluation (NDE) techniques for composite overwrapped pressure vessels intended for gaseous hydrogen infrastructure applications. The majority of the study focuses on Model Acoustic Emissions (MAE) techniques. Testing was performed on various composite tank designs including small high pressure plastic-lined fully-wrapped composite pressure vessels designed for portable, stationary or vehicular storage and large steel-lined hoop-wrapped pressure vessels designed for bulk transport and stationary storage. MAE testing was performed by Digital Wave Corp. on vessels provided by Lincoln Composites and TransCanada.MAE testing of Lincoln Composites plastic-lined fully-wrapped 10,000 psi composite pressure vessels was performed at the Lincoln facilities in April 2007. Tank damage was simulated through drilled holes, membrane cuts and a drop test, and subsequent proof and burst testing was performed while monitoring with MAE techniques. The manufacturing consistency was confirmed by MAE.Generally, it was observed that the vessels failed at damage sites. Drilled holes all the way through the composite resulted in lowest burst pressure, followed by impact from 6-ft. drop onto concrete, and finally the cut fibers. MAE picked up the newly introduced damage very well on first pressurization after damage occurred. Emission did not completely stabilize, indicating that the damage did continue to grow during the pressure holds. At the higher sensitivity setting, MAE Frictional Emission (FRAE) was picked up on every cycle after damage. Location of damage was very clear acoustically using MAE techniques. MAE testing of six TransCanada large steel-lined hoop-wrapped composite pressure vessels was performed in October 2007. The test program included cyclic testing, pressure/autofrettage and burst testing while monitoring using MAE techniques. During cycle testing crack growth was detected in the metallic head to shell welds at both ends of the vessel. The number of cycles sustained before fatigue failure due to this cracking exceeded the required 10,000 cycles. This was determined from the acoustical signal produced by a leak source. During the pressure (autofrettage) tests, the cumulative events versus time curves showed a characteristic?roll over?during pressure load holds in the AE test in all cases. There were few or no events during the load holds and very few events during the AE test. This is consistent with fracture mechanics reasoning since the AE test pressure is so much lower than the autofrettage pressure. It was observed that autofrettage cycles at 1.5 x operating pressure instrumented for AE detection would bound an AE cycle at 1.1 x operating pressure. This conclusion is in agreement with previous experience on various other pressure vessels.A study and laboratory testing of MAE sensor arrays constructed of piezoelectric material, polyvinylidene film (PVDF), was performed by Digital Wave Corp. in February 2008. This study looked at two ways to enhance the sensitivity of the PVDF film transducers, 1) sensor stacking and analog summation of the sensor outputs, and 2) digital summation of the sensor outputs. It was observed that stacked sensors increased sensitivity of detection, there was no phase distortion due to stacking and reducing sensor size can reduce aperture affects and increase bandwidth. A phased array configuration for modal acoustic emission (MAE) can determine direction of source and possibly distance. Phasing of signals for source location is possible and aids in mode identification and source location, which is very sensitive to variations in arrival time differences. Sensor placement is also extremely important, and the sensitivity to array geometry must be studied.This report also includes additional discussion of other relevant NDE and analysis techniques including a study of composite tank hydrostatic test requirements, a finite element analysis (FEA) and fracture mechanics analysis on composite reinforced pressure vessels predicting failures observed during testing and indicated using AE techniques, and a discussion of photon induced positron annihilation (PIPA) which is a potential NDE process that can assess material damage at the near-molecular level.
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发布单位或类别: 美国-美国机械工程师协会
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