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首页> 外文学位 >Ultrasonic wave propagation model for nondestructive evaluation of solid rocket motor propellant.
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Ultrasonic wave propagation model for nondestructive evaluation of solid rocket motor propellant.

机译：固体火箭发动机推进剂无损评估的超声波传播模型。

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The detection of voids in SRM propellant is critical to the safety of Launch Vehicles. Currently this is done with the use of x-rays as an NDE technique. It is hoped to supplant this technique with the use of ultrasonic NDE methods for reasons of reduced cost, increased mobility of the NDE set-up, automated accept/reject criteria, to name a few. To be feasible the ultrasonic NDE methods must be able to differentiate between a through-transmission signal from an SRM propellant segment with a void, and a signal from a segment without a void. The ability of ultrasonic NDE to penetrate one meter of propellant has already been demonstrated with sufficient signal-to-noise ratio. The crux of the ultrasonic NDE method will be in using the information present in the received signal to detect, locate, and size voids. This research embarks in this direction by showing the ultrasonic NDE technique received signal indicates a viscoelasticity of the SRM propellant, and therefore viscoelasticity must be included in any wave propagation model of the SRM propellant.; Ultrasonic NDE was used on a sample of inert propellant at the fifth and eleventh month after casting. A matched pair of 50 kHz transducers, wavelength in the material of 3.2 cm, were used in over 100 tests. Attenuation and velocity versus frequency profiles were obtained. A simple numerical simulation, based on the Kelvin-Voigt mechanical approximation of the stress-strain relationship, guided by a scalar expression, determined a viscoelastic damping coefficient, which is a measure of viscosity. This characterized the propellant sample for bulk viscoelastic material properties, and matched the experimental attenuation over the limited frequency band of the transducer.; Ultrasonic NDE on specimen with inclusions showed excess attenuation over what one would expect without inclusions. Numerical simulations showed like excess attenuation.; Ultrasonic NDE on SRM propellant segments shows promise as a technique for future use to detect, locate, and size voids. Further, as an ancillary benefit, the characterization of propellant sample for bulk viscoelastic material properties also allows the periodic tracking of attenuation, velocity and VDC to determine the changes over time. This should provide a quantitative means of determining service life in SRM propellant and possibly in other viscoelastic material.
机译：SRM推进剂中空隙的检测对于运载火箭的安全至关重要。当前，这是通过使用X射线作为NDE技术来完成的。希望使用超声波NDE方法代替该技术，以降低成本，增加NDE设置的灵活性，自动接受/拒绝标准等。为了可行，超声NDE方法必须能够区分来自带有空隙的SRM推进剂段的直通信号和来自没有空隙的段的信号。超声波NDE能够穿透一米推进剂并具有足够的信噪比。超声波NDE方法的关键在于利用接收信号中存在的信息来检测，定位和调整空隙。这项研究通过显示超声NDE技术接收到的信号表明SRM推进剂的粘弹性而朝着这个方向迈进，因此，在SRM推进剂的任何波传播模型中都必须包括粘弹性。铸造后第五个月和第十一个月，将超声波NDE用于惰性推进剂样品。超过100个测试中使用了一对配对的50 kHz换能器，波长为3.2 cm。获得了衰减和速度与频率的关系曲线。在标量表达式的指导下，基于应力-应变关系的开尔文-沃格（Kelvin-Voigt）机械逼近的简单数值模拟确定了粘弹性阻尼系数，该系数是粘度的量度。这说明了推进剂样品的整体粘弹性材料特性，并与换能器有限频带上的实验衰减相匹配。带有夹杂物的样品上的超声波NDE表现出的衰减比没有夹杂物的情况要大。数值模拟显示出过度衰减。 SRM推进剂段上的超声波NDE有望作为一种将来用于检测，定位和确定空隙大小的技术。进一步，作为辅助益处，对于块状粘弹性材料特性的推进剂样品的表征还允许衰减，速度和VDC的周期性跟踪以确定随时间的变化。这应该提供一种定量方法来确定SRM推进剂以及可能的其他粘弹性材料的使用寿命。

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