Ultrasonic Phased Arrays for Nondestructive Evaluation of Cementitious Materials and Structures

用于水泥材料和结构无损评估的超声相控阵

• 批准号: 9903535
• 负责人: Shi-Chang Wooh
• 金额: --
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-10-01 至 2002-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9903535&HistoricalAwards=false
• 关键词: Ultrasonic; Phased; Arrays; Nondestructive; Evaluation

CMS9903535PI: Shi-Chang WoohMITUltrasonic Phased Arrays for Nondestructive Evaluation of CementitiousMaterials and StructuresThis is a threeyear research proposal challenging the problems associated withthe nation's aging infrastructure. It is aimed to study and develop ultrasonicphased array transducers most effective for assessing concrete structures andcementitious materials.Deterioration of civil infrastructure systems (CIS) has become a central issuein reference to both safety and socioeconomic concerns. Deterioration itself isinevitable, but nondestructive evaluation (NDE) may offer a solution forpreventing more serious consequences by detecting damage in its earlier stage.Development of reliable, expeditious and effective NDE methods facilitatesearly warnings of deterioration and structural integrity. Consequently, ithelps making decision of priorities on repair, retrofitting and replacement,thus making contribution to assurance of public safety. Concrete structures aremajor building blocks of CIS. As the impact of their degradation is widelyrecognized, there are growing demands for efficient condition assessmenttechnology. NDE of structural concrete is a relatively undeveloped disciplineas compared with that of steel and other metals. The main mode of difficulty isthe heterogeneous and attenuating nature of concrete.Ultrasonic phased array systems, widely employed in the area of medicaldiagnostics, provide both quantitative measurement and imaging by means ofelectronic scanning of a target object with an acoustic beam. This featureeliminates the need of mechanical scanning and enhances nondestructiveinspection capabilities, which cannot be realized by static methods usingsingle element transducers. The potential advantages of the arrays include (1)increased maneuverability of the ultrasonic beam, (2) greater area ofinsonification from a fixed position, (3) high signal-to-noise-ratio, (4)reduced inspection time and automated testing procedure, and (5) expeditiousimaging capability.Phased arrays are recently extending their applications to metals and compositematerials as well. However, these arrays cannot be utilized for concrete sincethey are designed without considering relevant aspects of importance. Thisresearch program intends to deal with innovative low frequency phased arrayultrasonic sensors and their applications to cementitious materials.It was observed from our previous study that acoustic focusing is moreeffective in dealing with inhomogeneous materials, and the feasibility testsdemonstrated promising results that phased arrays can be utilized for concreteif properly designed. Nevertheless, the analysis raised a potential problem ofenlarged "dead" zone that subsequently reduces effective inspectable area. Thisis a serious deficiency from a practical standpoint, while our previous studysuggests an approach to resolve this challenging problem as presented in thisproposal. We would like to explore the possibilities of extending the study inthe proposed program.The main objective of the proposed research is to examine the benefits andlimitations of using ultrasonic arrays for detecting cracks and other defectswithin concrete structures. For this, a threephase research plan is proposed:(1) modeling and optimization, (2) system development, and (3) implementationand performance evaluation. It is anticipated that phased arrays will offerextreme flexibility in transforming the data into useful informationpresentable in either quantitative forms or imaging of defects in concrete.

这是一项为期三年的研究计划，旨在解决与国家老化的基础设施相关的问题。它的目的是研究和开发超声相控阵换能器，最有效地评估混凝土结构和水泥材料。民用基础设施系统(CIS)的破坏已经成为一个涉及安全和社会经济问题的中心问题。劣化本身是不可避免的，但无损评估(NDE)可以提供一种解决方案，通过在早期阶段检测损伤来防止更严重的后果。可靠、快速和有效的无损评估方法的发展有助于对劣化和结构完整性进行早期预警。因此，它有助于确定维修、改造和更换的优先顺序，从而为确保公共安全做出贡献。混凝土结构是独联体的主要组成部分。随着它们退化的影响被广泛认识，对有效的状态评估技术的需求越来越大。与钢和其他金属的NDE相比，结构混凝土的NDE是一个相对不发达的学科。超声相控阵系统被广泛应用于医学诊断领域，它通过利用声束对目标对象进行电子扫描来提供定量测量和成像。这一特点消除了机械扫描的需要，并增强了非破坏性检测能力，这是使用单元件传感器的静态方法无法实现的。这种阵列的潜在优点包括：(1)提高了超声波束的可操作性，(2)从固定位置发出的声学面积更大，(3)高信噪比，(4)缩短了检测时间和自动化测试程序，以及(5)快速成像能力。然而，这些阵列不能用于混凝土，因为它们在设计时没有考虑到重要的相关方面。本研究旨在研究新型低频相控阵超声传感器及其在胶凝材料中的应用。从我们先前的研究中观察到，声聚焦在处理非均匀材料方面更有效，可行性测试表明，如果设计合理，相控阵可以用于混凝土。然而，分析提出了一个潜在的问题，即扩大了“死亡区”，从而减少了有效检查区域。从实践的角度来看，这是一个严重的缺陷，而我们之前的研究建议了一种方法来解决这一具有挑战性的问题，如本提案所示。我们希望探讨在拟议的计划中扩展这项研究的可能性。拟议的研究的主要目标是检查使用超声波阵列检测混凝土结构内的裂缝和其他缺陷的好处和局限性。为此，提出了三个阶段的研究计划：(1)建模和优化；(2)系统开发；(3)实现和性能评估。预计相控阵将提供极大的灵活性，将数据转换为有用的信息，以量化的形式或对混凝土中的缺陷进行成像。