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Secondary Processing Development and Prototyping of Cast Single-Piece Vehicle

Description:

OBJECTIVE: Develop and prototype highly scalable processes to fabricate single-piece underbody structures to achieve a combination of high strength and high toughness. DESCRIPTION: The Army is interested in the production of large single-piece underbody structures for combat vehicles. The structure must possess an outstanding combination of strength and toughness for it to survive battlefield threats. In general single-piece structures are produced by casting and followed by subsequent secondary processing to achieve the desired mechanical properties in the structure. It has been demonstrated that a cast steel material after appropriate post-cast secondary processing exhibits a combination of strength and toughness as high as 180 ksi tensile yield strength, 230 ksi ultimate tensile strength, 12% tensile elongation, and 30 ft-lb Charpy V Notch (CVN) toughness at -40 degrees F[1,2]. Unfortunately such remarkable mechanical properties are achievable only in relatively small cast structures. Suitable scalable secondary processing techniques are not currently available which could be applied to large single-piece cast structures to achieve the aforementioned mechanical properties. The challenge here is to establish scalable secondary processes for very large single-piece structure to achieve the required combination of strength and toughness. Additional challenge is to achieve uniformity of the properties throughout the entire large single-piece structure including through thicknesses. Army is inviting proposals to develop and prototype highly scalable processes to fabricate large single-piece underbody structures with a combination of high strength and high toughness throughout the entire structure and thickness. The process must be scalable and be able to integrate relatively smoothly to very large scale fabrication or production under the standard manufacturing practices without needing nonconventional manufacturing equipments or processes beyond what are currently used. Army is seeking proposals that address novel processing techniques, such as innovative casting, robust post-cast processing, or other equally innovative and robust processes, that can be easily integrated with the existing manufacturing bases to enable smooth transition to large scale processing of large single-piece structure. PHASE I: Design processes to produce plates having nominal dimension of 4 ft wide x 4 ft long x 3 in thick. Demonstrate that the designed structure is able to achieve the Phase I threshold properties of 180 ksi tensile yield strength, 230 ksi ultimate tensile strength, 12% tensile elongation, and 30 ft-lb Charpy V Notch (CVN) toughness at -40 degrees F. Two (2) 4 ft width x 4 ft length x 3 in thickness plates meeting the aforementioned threshold properties shall be produced. Verification and validation of the uniformity of the properties throughout the entire structure is critical and one (1) of the two (2) identically processed plates shall be destructively evaluated accordingly following the ASTM standards [3-5]. Uniformity of the properties throughout the entire plate including the thickness must be evaluated. For example, it may be evaluated in x, y, and z reference orientations within every 1 ft x 1 ft spacing in the x and y reference orientation at two positions in the z-direction: one at the mid-point of the plate and the other half-way between the mid-point and the surface. The plate not destructively tested shall be delivered to U.S. Army Research Laboratory for blast tests. The secondary process design preferably be suitable not only for processing simple structures but also for processing complex shape large structures. Additionally, the secondary process design must be sufficiently adaptable such that it can be directly integrated into the existing conventional manufacturing infrastructures or foundry processes without needing nonconventional manufacturing equipments or processes beyond what are currently available and used commercially. Numerical methodologies in process model and simulation are highly desirable in demonstrating the Phase I secondary process predictability. PHASE II: The Phase II program will be to scale up and optimize the process to produce larger plates and subsequently to an entire single-piece vehicle underbody tub (i.e., lower hull and underbelly). Two (2) plates having nominal dimension of 6 ft wide x 10 ft long x 3 in thick shall be fabricated and achieved the same threshold properties of the Phase I. Verification and validation of the uniformity of the properties throughout the entire structure and through the thickness is critical and one (1) of the two (2) identically processed plates shall be destructively evaluated accordingly following the ASTM standards [3-5]. Uniformity of the properties throughout the entire plate and thickness must be evaluated. For example, it may be sampled at every 2 ft in the x-y plane. The plate not destructively tested shall be delivered to U.S. Army Research Laboratory for blast tests. Following successful validation of the plate properties, one (1) full single-piece vehicle tub (i.e., lower hull and underbelly) having nominal dimension of 12 ft wide x 30 ft long x 5 ft high and thickness between 2 in and 3 in shall be fabricated and delivered to U.S. Army Research Laboratory for blast tests. The process shall be validated to be sufficiently predictable, adaptable, flexible, and robust such that it can be directly integrated into the existing conventional manufacturing infrastructures or foundry processes without needing nonconventional manufacturing equipments or processes beyond what are currently available and used commercially. Numerical methodologies of Phase II processes shall be developed and the model and simulation shall be demonstrated to be highly predictable. PHASE III: The manufacturing technology shall be transitioned to civil and military sector applications. . Successful Phase II validation facilitates immediate single-piece vehicle hull and cap fabrication, and integration of demonstrated technology. The manufacturing technology and force protection capability information will be transitioned to both Tank Automotive Research and Development (TARDEC) and Tank Automotive Command (TACOM) for immediate implementation and integration into existing and future platform design and engineering efforts. Deliverables and technical data packages (TDPs) resulting from this SBIR will support a variety of Army PEOs and PMs in Army major acquisition programs. The manufacturing technology to civilian application enable very-large-scale complex-shape cast structural part in ship hulls, transportation vessels, and energy infrastructures where unnecessary joining are critical design requirements.
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