Finite Element Analysis and Factorial Optimization of Heat Treatment Flaws in CNG Pressure Vessels: Implications for Structural Integrity and Safety

This study investigates the critical impact of heat treatment flaws on the structural integrity and safety of compressed natural gas (CNG) pressure vessels made from Al 6061 and AISI 4130 steel through finite element analysis (FEA) in SolidWorks 2023 and factorial design optimization via Design Expert 13. Simulations were conducted under pressures of 20, 25, and 30 N/mm² with varying flaw severities (none, minor, major), revealing that AISI 4130 steel at 25 N/mm² exhibited a maximum stress of 2.998E+10 N/m², deformation of 15.14 mm, and a safety factor of 0.01534, while Al 6061 at 20 N/mm² showed 1.412E+4 N/mm² stress, 14.70 mm deformation, and a safety factor of 0.01948. At 30 N/mm², AISI 4130 steel demonstrated increased risk with stress reaching 1.814E+4 N/mm², deformation of 18.30 mm, and a safety factor of 0.01516, accompanied by a strain of 1.511E-01. ANOVA results indicated that pressure significantly influenced deformation (p = 0.0382) and safety factor (p = 0.0051), while heat treatment flaws impacted stress (p = 0.0381). Fatigue life varied from 8.00E+05 cycles (AISI 4130 steel, 30 N/mm², minor flaws) to 3.1E+06 cycles (Al 6061, 25 N/mm², no flaws), with all factors showing high significance (p < 0.0001). The optimal configuration—Al 6061, no flaws, and 30 N/mm²—yielded a stress of 3.41E+10 Pa, fatigue life of 2.5E+06 cycles, deformation of 32.366 mm, and a desirability score of 1.000. These findings underscore the importance of minimizing heat treatment flaws and controlling operational pressures below 30 N/mm² to enhance vessel safety and durability, offering valuable insights for design optimization and regulatory standards in sustainable energy applications.