TECHNOLOGY AREAS: Materials/Processes

ACQUISITION PROGRAM: PMA-264 Littoral ASW Multistatic Project and PEO IWS5 Deep Water Active Dis

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Twofold, to develop materials, devices, and techniques to dissipate heat generated in the interior of high powered underwater acoustic transducers and to develop an understanding of nonlinearity in underwater acoustic projectors. These two concepts can be related or they may be treated separately with only one of the objectives being addressed. The intent of the first objective is to efficiently dissipate heat generated by the transducer driving mechanism to the water medium as a means to control heat build-up within the transducer and thus optimize device performance. The second objective strives to understand nonlinearity in high power transducers with the end goal of designing devices that will minimize this effect that limits performance.

DESCRIPTION: The performance of naval systems for Anti-Submarine Warfare (ASW) is limited by the size and power of current sensor systems. Although current systems are adequate for current missions, improved sensors, and specifically active projectors, are required for maintaining tactical advantage against future adversaries. This STTR topic will address two topical problems of high power projectors: overheating that results in decreased performance and/or catastrophic failure and nonlinearity caused by excessive electrical, mechanical or thermal stresses that limits the output power capability of the projector. There is a real need for designing underwater acoustic projectors that are capable of very high acoustic output powers at high duty cycles while maintaining a small profile. Addressing the topic area of heat dissipation in transducers (which may or may not be combined with the second issue of nonlinearities in transducers) it has been observed that in the majority of high power underwater projectors the active driver assembly that produces the force to translate to displacement in the transducer for acoustic output has finite losses that result in generation of heat that ends up being contained within the transducer since the typical transducer, designed to keep water out of its interior and to protect the device from physical or environmental damage, has no easy thermal path for the dissipation of heat to the water medium. In the case of the second topic issue it is understood that under high drive conditions electrical stresses in the active drive material along with mechanical overstressing in both the active driver and the other components of the transducer produce nonlinearities that are seen as acoustic distortion. The addition of heat build-up under these conditions complicates the situation. These stresses can combine and result in the transducer exceeding its operational limit and this then results in reduced performance or failure. The ability to understand the constitutive components of nonlinearity and distortion will assist in developing designs and techniques that can temper the root causes and thus open the opportunity to design a transducer that can work harder and be more reliable.

PHASE I: For the case of effects of heat on transducer performance, analyze candidate projector designs that utilize either piezoelectric ceramic or magnetostrictive material as the active driver and determine possible means to extract heat from the driver assembly without impairing the performance or reliability of the device. It should be assumed that the transducer�s duty cycle will be 100% and thus the extracted heat needs to be able to be efficiently dissipated to the water medium in either a passive or active means. Develop a useable thermal model to analyze the proposed method. If the effort is focused strictly on nonlinearity effects analyze the transducer components and their use that contribute to the creation of nonlinearities. Conceptualize a means to predict this behavior and determine how it may be quantified.

PHASE II: For the specific focus on heat remediation develop a complete thermal model to couple with an appropriate transducer model to permit a complete evaluation of the approach at the predictive level. Develop prototype components and after evaluation integrate into a prototype transducer for tests and evaluation and validation of the model. Determine the performance parameters of the candidate transducer and predict efficiencies for a variety of other transducer types. For the focus of nonlinearity in transducers develop a complete analytical/numerical model to predict the inception of nonlinear operation in an underwater acoustic projector and the means to identify, isolate and analyze where the distortion begins and the mechanisms involved. Develop prototype components of a notional transducer and test its linear and nonlinear behavior as a means to evaluate and validate the model. Determine the performance parameters of the notional transducer and undertake parametric studies to determine a component�s sensitivity to nonlinear operation. Phase II efforts may require the need for access to classified information.

PHASE III: For both areas of interest utilize the design approach and mechanisms developed to adapt advanced transducer developments to be able to operate more reliably and at high drive levels than originally planned by vastly improving the thermal limits of the device and understanding the contribution of nonlinearity on the performance limitation of the device.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The broad applicability and market for this technology across the Navy for both transducers and actuators should lead to a commercially successful result in the oil and natural gas exploration industries and to a variety of commercial products that now operate �hot� and/or distorted and are limited because of that.

REFERENCES:
1. C.H. Butler & J.L. Butler, Transducers and Arrays for Underwater Sound, Springer 2007

2. R.S. Woollett, "Power Limitations of Sonic Transducers", IEEE Trans. Sonics and Ultrasonics, SU-15, 218-229 (1968)

3. D.A. Berlincourt, D.R. Curran, and H. Jaffe, Ch. 3, Piezoelectric and Piezomagnetic Materials, Physical Acoustics, Vol. I, Part A, W.P. Mason, Ed. (Academic Press, N.Y., 1964)

KEYWORDS: ASW; sonar; projectors; heat dissipation; nonlinearity; underwater

TPOC: Jan Lindberg
Phone: (703)696-7116
Fax: (703)696-3390
Email: [email protected]
2nd TPOC: John Blottman
Phone: (401) 832-5112
Fax: (401) 832-6401
Email: [email protected]