基于嵌入式压电陶瓷的动态应力传感器的开发与标定

发布时间：2018-08-31 17:32

【摘要】：压电陶瓷(PZT,Lead Zirconate Titanate)材料由于具备响应速度快、频率响应范围宽、压电常数大、线性关系好、易切割、价格低廉的优点以及其同时具备传感和作动功能,近年来,在土木工程结构的健康监测和损伤识别中得到成功应用。通过将经过防水和绝缘处理后的压电陶瓷片封装入与混凝土材料相兼容的混凝土砂浆块中然后将其嵌入被测混凝土结构中充当驱动器以及传感器,实现了混凝土结构的裂缝发生发展的监测。对混凝土结构的应力状态进行监测是维持其安全性的重要手段。目前,混凝土结构进行应力测量,一般只注重其表面上的应力分布。通过在混凝土结构表面黏贴电阻式应变片来测量混凝土表面的应变,然后通过假定的混凝土材料的弹性模量换算得到混凝土表面的应力,而对混凝土内部的应力状态无法获得。此外,通过测量所得应变以及弹性模量来换算得到应力时,弹性模量取值对换算结果有影响,特别是混凝土在强动力荷载作用下而进入塑性阶段后,混凝土材料的应力应变关系不再保持线性,不能通过应变测量值获取应力。所以,对工作状态下混凝土结构内部应力的测量对混凝土结构的安全性来说至关重要。开发能够直接嵌入混凝土内部、直接用于混凝土内部应力测量的传感器,特别是在地震、爆炸和冲击等强动力荷载作用下的动态应力的测量具有十分重要的意义。本文提出基于压电材料的混凝土结构内部动态应力测量传感器,并对其进行标定。具体的工作包括以下三个方面:(1)在已有研究的基础上,对嵌入式压电陶瓷动态应力传感器进行了部分改良,使得制作的传感器具有良好的防水绝缘性能,灵敏度更稳定,并且使其更易于绑定于混凝土结构中。(2)制作了基于压电陶瓷的动态剪应力传感器并将该剪应力传感器嵌入混凝土空心薄壁空心圆筒中,且满足空心圆筒的直径与壁厚达到足够比例,利用小型落锤实验机进行冲击荷载加载用以标定其灵敏度,实验结果表明所研制的剪应力传感器之间的灵敏度个体差异性小,所研制的基于压电陶瓷的剪应力传感器表现出良好的线性度。(3)制作了基于剪切型压电陶瓷以及伸缩型压电陶瓷的平面动态应力传感器,通过使用小型落锤实验机施加冲击荷载并对埋置在简支梁中的平面应力传感器的灵敏度进行标定,实验表明基于压电陶瓷的平面动态应力传感器可以较好反映混凝土结构内部的应力情况,为下一步对混凝土结构的定量动态应力监测做好铺垫。
[Abstract]:Piezoelectric ceramics (PZT,Lead Zirconate Titanate) have the advantages of fast response speed, wide frequency response range, large piezoelectric constant, good linear relationship, easy cutting, low price and both sensing and actuating functions. It has been successfully applied in health monitoring and damage identification of civil engineering structures. By encapsulating the waterproof and insulated piezoelectric ceramic pieces into concrete mortar blocks compatible with concrete materials and embedding them into the tested concrete structures as actuators and sensors, The monitoring of crack occurrence and development of concrete structure is realized. Monitoring the stress state of concrete structure is an important means to maintain its safety. At present, the stress distribution on the surface of concrete structure is generally paid attention to in stress measurement. The strain of concrete surface is measured by sticking resistive strain gauge on the surface of concrete structure, and then the stress of concrete surface is obtained by the elastic modulus conversion of the assumed concrete material, but the stress state inside the concrete can not be obtained. In addition, when the strain and elastic modulus are converted to obtain the stress, the value of elastic modulus has an effect on the conversion results, especially when the concrete enters the plastic stage under the strong dynamic load. The stress-strain relationship of concrete is no longer linear, and the stress can not be obtained by strain measurement. Therefore, it is very important for the safety of concrete structure to measure the internal stress of concrete structure. It is of great significance to develop sensors which can be directly embedded in concrete and can be used to measure the internal stress of concrete, especially under strong dynamic loads such as earthquake, explosion and shock. This paper presents a dynamic stress measurement sensor for concrete structure based on piezoelectric materials and calibrates it. The specific work includes the following three aspects: (1) based on the existing research, the embedded piezoelectric ceramic dynamic stress sensor is partially improved, which makes the sensor have good waterproof and insulation performance, and the sensitivity is more stable. And make it easier to bind to concrete structure. (2) the dynamic shear stress sensor based on piezoelectric ceramics is made and embedded in concrete hollow thin-walled hollow cylinder. When the diameter and wall thickness of the hollow cylinder reach enough ratio, the sensitivity is calibrated by impact load loading with a small drop weight test machine. The experimental results show that the sensitivity difference between the developed shear stress sensors is small. The developed shear stress sensor based on piezoelectric ceramics shows good linearity. (3) Planar dynamic stress sensors based on shear piezoelectric ceramics and telescopic piezoelectric ceramics are fabricated. The sensitivity of the plane stress sensor embedded in a simply supported beam is calibrated by applying impact load to a small drop weight experimental machine. The experimental results show that the planar dynamic stress sensor based on piezoelectric ceramics can better reflect the internal stress of concrete structure and pave the way for the quantitative dynamic stress monitoring of concrete structure in the next step.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU37;TU317

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