Research On Uncertainty Of Underwater Explosion Pressure Measurement

The pressure measurement is very important to the research on the underwater explosion.By the accurately pressure measurement, the severity of load for the ship suffering to UNDEXcan be determined, and the power of various explosives can also be evaluated. So it plays animportant role on the ship anti-shock research and weapon design. But the major researchworks on underwater explosion pressure measurements are just focused on the level ofapplication technology now. It is not sufficiently investigated on the theory of UNDEXpressure measurement that makes it difficult to correctly access the error of the measuringdata, and also hinders the development of this technique. Accordingly, this investigationaddresses on the subject of transfer characteristics of pressure signal with theory andexperiment, and the uncertainty of underwater explosion pressure measurement will also beevaluated.The theory analysis on the underwater explosion pressure measurement is a importantpart of the thesis. The rational evaluation to the uncertainty of underwater explosion pressuremeasurement should be built on the well understanding the establish mechanism of pressuresignal. Based on the analysis of the establishment process of the underwater explosionpressure signal, the inputs and outputs of the pressure signal are divided three phases namedas the pressure field establishment, the pressure field transform and the signal transmission bycircuit. For the first phase, the aberration of pressure field due to the delaying time forshockwave overlaying the sensing crystal and the scattering effect is investigated. For thesecond phase, the problem of piezoelectric vibration is handled when the pressure is thetransformed to the electric signal. And the influence of damping ratio and nature frequency ofthe sensing item on the pressure signal is investigated. For the third phase, the characteristicsof transmission and coupling of electric circuit elements are analyzed, especially for the leadand amplifier, and a total transmission function of measuring electric circuit is obtainedfinally.A key matter of this thesis is to establish an uncertainty evaluation method on theunderwater explosion pressure measurements. On the base of the theoretical analysis to threemeasurement phases, a transfer function is put forward to character the uncertainty ofunderwater explosion pressure measurement. The theory model of dynamic uncertainty isestablished which relates to the frequency and time that embody the core nature of theevaluation of the UNDEX pressure measurement technique. Subsequently, the synthetic method of dynamic uncertainty and static uncertainty and the denoting form of totaluncertainty are presented. A total uncertainty evaluating indicator is calculated by bandingtogether the uncertainty belong to measuring system with the weights belong to thecomponents of the measured pressure signal. With the evaluating indicator, we can evaluatethe measuring ability of system to a given pressure more explicitly.The mathematic model of the uncertainty of underwater explosion pressuremeasurements is built on the theory analysis, and its practical utility should be validated byexperiment. The influences of key factors contained in the measuring system on the UNDEXpressure wave are investigated with the self-developed pressure transducers and amplifiers,and the pressure waves for PCB transducer are also investigated by tests and theoreticalanalysis. Then the mathematic models of the uncertainty are validated by experiment results.The uncertainty is evaluated of the two systems that are involved in the underwater explosionpressure measurement.In this thesis, the uncertainty sources of the UNDEX pressure measurement are exploredfrom the conversion process of mechanical signal to electric signal in essence. The conversionis expressed by a transfer function, and the frequency characteristics of dynamic uncertaintyof underwater explosion pressure measurement are presented. This method can be used for thevalidation of applicability and reliability to a measuring system, and can also promote thetechnical development of underwater explosion pressure measurement.