水下爆炸气泡射流载荷阵列测量技术探索

On an array-sensor technology for measuring bubble jet load generated by underwater explosion

水下爆炸气泡射流载荷测量目前存在两个难点:(1)气泡射流载荷是非均匀的面载荷,但其作用半径仅为气泡最大半径的1/10,限于传感器尺寸及安装空间,敏感元密度较低,难以准确获取气泡射流载荷空间分布规律;(2)气泡射流载荷测量时传感器所处的力学环境非常复杂,传感器容易损坏,导致无法测得完整时程。因此现有测量手段难以获取气泡射流载荷的时空分布特性。鉴于此,设计了一种阵列传感器,在一张PVDF(聚偏氟乙烯)压电薄膜上采用特殊工艺加工多个小型敏感元,敏感元尺寸为5 mm×5 mm,呈8×8矩阵排列,敏感元密度≥1 cm^(-2),同时在揭示传感器损坏机理的基础上设计了传感器防护装置。在小型观测水槽内开展了小当量炸药水下爆炸试验,采用阵列传感器测量获取了气泡射流载荷的时空分布特性。研究结果表明:(1)设计的防护装置可保证传感器在气泡射流载荷测量过程中不损坏;(2)气泡射流载荷中心最大,向四周逐渐减小,中心处气泡射流载荷峰压约35.6 MPa,约为冲击波峰压的1.16倍。建立的阵列测量技术可为水下爆炸气泡射流的深入研究提供技术支撑。

There are two difficulties in the measurement of underwater explosion bubble jet load:(1) the bubble jet load is a non-uniform surface load, but its radius of action is only 1/10 of the maximum radius of the bubble, the density of sensitive elements which is limited to the size and installation space is low, so it is difficult to accurately obtain the spatial distribution of bubble jet load;(2) the mechanical environment of the sensor is very complex when measuring the bubble jet load, so the sensor is easy to be damaged, which makes it impossible to obtain the complete time history. Therefore, it is difficult to obtain the spatiotemporal distribution characteristics of bubble jet load by existing measurement methods. In view of this, an array sensor was designed. Several small sensitive elements were processed on a piece of PVDF piezoelectric film by special technology. The size of sensitive elements is 5 mm×5 mm, arranged in 8×8 matrix, and the density of sensitive elements is≥1 cm^(-2). At the same time, the sensor protection device was designed on the basis of revealing the damage mechanism of the sensor. The underwater explosion test of small equivalent explosive was carried out in a small observation tank, and the spatiotemporal distribution characteristics of bubble jet load were measured by using array sensor. The results show that:(1) the designed protection device can ensure that the sensor will not be damaged in the process of measuring the bubble jet load;(2) the load in the bubble jet center is the highest and decrease to the surrounding gradually. The peak pressure of the bubble jet load is about 35.6 MPa, which is about 1.16 times of the shock wave peak pressure. The array measurement technology can provide technical support for the in-depth study of underwater explosion bubble jet.