DON26BZ01-DV044 — DIRECT TO PHASE II: Advanced Damage Criticality Analysis

Award Maximum: $2,000,000 Period of Performance: 12 months (Base) + 24 months (Option) Phase Type: Direct to Phase II (DP2)

OBJECTIVE: Develop a passive Structural Health Monitoring (SHM) system to identify, locate, and characterize the severity of defects and cracks due to fatigue loading or impacts based on novel or advanced technologies with a basis in physics and avoiding qualitative assumptions.

DESCRIPTION: The Navy seeks an effective passive Structural Health Monitoring (SHM) system for Navy ship hulls and other structures that can monitor defects, such as crack growth from fatigue or impacts, and provide actionable information about the severity of the defect in an automated manner, i.e., in real time. Such fatigue cracks develop and grow in Navy ship hull welds and plating from cyclical life-cycle stresses and event-driven forces from severe sea states, collisions, and groundings.

The U.S. Navy and other navies around the world have installed SHM systems to monitor hull structural health but almost all are based on using strain gauges to monitor stresses on the hull and inferring crack growth based on fatigue life calculations. For example, the Military Sealift Command (MSC) has worked with the American Bureau of Shipping (ABS) and installed SHM systems consisting of strain gauges and accelerometers on several ships in the T-EPF class, which monitor hull deflection and dynamic movement due to the ship's loading and the sea states encountered. The data from these sensors is being fed into a digital twin model developed to calculate structural stresses for managing vessel survivability and to minimize operating risk.

There have been some attempts to develop fiber optics sensors to measure strain or Acoustic Emission (AE) sensors to monitor fatigue cracks directly. These approaches have seen varying levels of success, yet, better systems are needed. There may even be some applications for LiDAR use to improve success probability. The Navy is particularly interested in locating and characterizing the severity or criticality of a defect if one is detected. Currently there is not a system available on the commercial market.

The Navy's need for such hull monitoring capability has become more important with the introduction of high-speed and catamaran vessels, which are more prone to hull cracking due to the designs of the ships, materials of the hull, and stresses experienced in high seas. An ideal system would be capable of monitoring large areas of the ship's hull with sensing devices that provide cost effective coverage with the following capabilities:

• Detect and identify the location of crack growth signals in the hull if they exist in the presence of ship's background noise without producing false positives or negatives.

• Produce results in an automated manner, i.e., real time, so they are immediately available to the operating crew.

• Provide insight as to the severity of the crack growth considering the complex geometries found in hull structures with varying thicknesses and stiffeners.

The Navy would benefit from understanding structural risks in real time with the goal of minimizing the possibility of incurring structural damage at sea. The SHM system the Navy needs should provide meaningful information on ship structural health and reduce inspection and maintenance costs during repair availabilities by identifying areas of concern or damage in advance.

PHASE I: For a Direct to Phase II topic, the Government expects that the small business has accomplished the following in a Phase I-type feasibility effort and developed a concept for a workable prototype or design to address, at a minimum, the basic requirements for identifying, locating, and characterizing crack growth in ship hull structures in an automated, real-time manner.

PHASE II: Develop and deliver a passive SHM prototype solution (hardware/software/firmware) using novel or advanced technologies for use by the Navy in demonstrating the ability to monitor large area hull structures and identify, locate, and characterize crack growth in ship hull structures in an automated, real-time manner.

PHASE III DUAL USE APPLICATIONS: Assist the Navy in transitioning the technology for Navy use. Provide and field a passive SHM capability based on advanced technologies that will be used for identifying, locating, and characterizing crack growth in ship hull structures in an automated, real-time manner. Provide Navy personnel with training on how to utilize the system for the collection of data. Work with Navy personnel on how to install and operate the system until such time as they intend to assume that role.

In a manner like shipboard hull structural monitoring, the advanced passive SHM system could be employed in other useful applications, such as the following:

• Monitor ship hulls covered with acoustic tiles or other coatings/coverings for loose or missing tiles due to failure of the tile adhesive or other material defects.

• Monitor ship hulls with known areas of cracking or corrosion to determine when repairs are dictated and when other maintenance should occur.

• Monitor large Aboveground Storage Tanks (AST), common to both military and civilian petrochemical storage, to identify and locate AST bottom plate leaks.

This technology would also apply to commercial ship hull monitoring and SHM of offshore platform structures, such as oil drilling and production rigs.