Title: Adaptive Lattice Rejuvenation: A Self-Healing Superelastic Spring Subsystem for Dynamic Pressure Relief in CNG Trucks
Authors: Owei L. Youpele, Blessing Zekieni Yelebe, Kefas Odofori
Volume: 10
Issue: 7
Pages: 109-123
Publication Date: 2026/07/28
Abstract:
We present an Adaptive Lattice Rejuvenation (ALR) spring assembly, a self-healing superelastic subsystem designed to replace the conventional helical compression spring in pressure relief valves for compressed natural gas (CNG) trucks. The motivation for this work stems from the progressive degradation of NiTi superelastic springs under high-frequency dynamic loading, where retained martensite stabilization and dislocation pile-up accumulate over time. The proposed ALR spring is fabricated from a compositionally graded nickel-titanium wire, with a sinusoidal nickel concentration variation along its longitudinal axis that yields a spatially modulated austenite finish temperature. This grading enables localized phase transformations: during a controlled thermal pulse, only specific segments revert from stress-induced martensite to austenite, while neighboring zones remain load-bearing. An embedded lithographically patterned platinum thin-film resistor network, divided into twelve independently addressable segments, delivers precisely timed heating pulses. A conformal piezoresistive silicon nanowire mesh provides real-time strain profiling at twelve measurement points with a gauge factor of approximately two hundred. A model predictive controller processes these strain signals to compute the retained martensite volume fraction in each segment; when the integrated strain deviation exceeds a predefined threshold, a rejuvenation pulse is scheduled. The controller optimally allocates heating currents to achieve ninety-five percent martensite reversion while penalizing excessive power consumption. The novelty of this work lies in the synergistic integration of compositional grading, microscale resistive heating, and embedded sensing within a single spring wire-allowing fatigue mitigation without bulk heating or valve disassembly. Furthermore, the ALR assembly is designed as a direct drop-in replacement for the existing spring in standard direct-acting relief valves, requiring no modification to the valve body, poppet, seat, or venting hardware. This approach significantly extends the operational lifespan of CNG truck pressure relief systems under cyclic loading conditions, thereby enhancing safety and reducing maintenance intervals.