High-Capacity Internal Balance

TECHNOLOGY AREAS: Sensors; Materials The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Develop the capability to design internal balances that increase the load capacity of internal balances while maintaining the form factor, sensitivity, measurement uncertainty, and an adequate safety factor. DESCRIPTION: Current internal strain gage balance technology has reached the limit of strength and sensitivity within the required form factors. A new step in measurement technology is required to increase the load capacity of internal balance measurements while maintaining the form factor, sensitivity, measurement uncertainty, and an adequate safety factor. The balance must maintain a 2.5-inch diameter or comparable form factor and be compatible with current tunnel installation hardware. The balance should be designed to the resolved loads described here within 0.1% measurement uncertainty (Normal Force: 10,000 lb, Pitching Moment: 32,500 in-lb, Side Force: 5,000 lb, Yawing Moment: 16,250 in-lb, Rolling Moment: 24,000 in-lb, Axial Force: 850 lb ). The internal balance needs to support aerodynamic models in a high load and dynamic wind tunnel environment. The safety of the facility and related systems requires a minimum safety factor of 3 on yield or 4 on ultimate on all components and areas of concentrated stress. Fatigue life is also a concern, and the design should strive for maximum life span using cyclic loadings at the intended loads stated. The operating range is 60-140 F with pressures between 10 and 4,000 psfa and the balance should be insensitive to environmental changes, or able to be calibrated over this range. The design methodologies of this high-capacity internal balance will be used to update balance designs of all shapes and capacity ranges. PHASE I: Provide a preliminary design and stress analysis that proves the feasibility of the increased load capacity with the appropriate safety factor. Highlight areas of high stress concentration and hardware limitations and provide detailed plans to mitigate any limiting factors. Instrumentation details and data system requirements should be investigated and reported. Provide estimates of the other balance metrics to show that the proposed the internal balance concept will be capable of meeting test requirements. PHASE II: Develop a prototype internal balance that meets the design criteria described. Deliver and demonstrate the prototype internal balance and perform a preliminary set of loadings and calibrations to validate acceptable performance and uncertainty requirements as outlined in Phase I. Provide a detailed stress analysis and documentation of the health monitor requirements to maintain safe operation within the capability of the internal balance. PHASE III DUAL USE APPLICATIONS: Use the design methodologies and technology developed and present possible applications to other balance designs, sizes, environments and load ranges for other facility applications. REFERENCES: 1. Calibration and Use of Internal Strain Gage Balances with Applications to Wind Tunnel Testing (AIAA R-091A-2020) https://doi.org/10.2514/4.106019.001; 2. Wind Tunnel Balances (Klaus Hufnagel), https://doi.org/10.1007/978-3-030-97766-5 KEYWORDS: 6-component balance; internal balance; high-capacity