This study presents a physics-based parametric optimization framework for thermoelastic energy harvesting from cyclic temperature variations using a cylindrical AISI 4340 steel rod. The model couples thermoelastic force and displacement, Euler buckling and yielding constraints, lumped-capacitance heat transfer, and mass-power multi-objective optimization. The feasible design space was evaluated as a function of rod diameter, length, temperature change, and load-transfer parameter. The results show that Euler buckling governs the practically relevant portion of the design space at moderate temperature changes, whereas yielding becomes increasingly restrictive at higher thermal loads. The Pareto-optimal solutions exhibit a clear mass-power scaling law, with the analytical prediction P<SUB>avg</SUB> ∝ m<SUP>2/3</SUP> closely reproduced by the numerical fit (n = 0.66717, R² = 0.999999). Under the baseline condition λ = 0.50, the maximum-power design produces approximately 0.16624 W, while a distance-to-ideal criterion identifies a substantially lighter compromise design with m = 223.0 kg and P<SUB>avg</SUB> = 0.09231 W. Refined optimization gives λ<SUB>opt</SUB> = 0.473 and P<SUB>max</SUB> = 0.170454 W, indicating a power penalty of only 2.47% when the simpler λ = 0.50 condition is used. Grid-refinement tests show changes below 0.006% in maximum power and below 0.5% in the compromise-design mass between the 250 × 250 and 500 × 500 grids. The results establish compact scaling and optimization rules for balancing structural stability, thermal response, mass, and average mechanical power in thermoelastic energy-harvesting elements.

The Heat-Affected Zone (HAZ) is one of the major parameters which determines the structural integrity in welded API 5L X52 pipelines, especially in a sour gas service containing Hydrogen Sulphide (H2S) [1]. This thorough review paper performed the analysis of different international standards including Det Norske Veritas Germanischer Lloyd DNVGL-ST-F101, American Petroleum Institute API 1104, National Association of Corrosion Engineers NACE MR0175 and American Society of Mechanical Engineers ASME B31.8. The researcher analysed the governing and regulation of Heat Affected Zone microstructure and associated properties including strength, hardness and toughness through the specifications like heat values, time between passes and Post Weld Heat Treatment (PWHT), welding specifications and qualification of welding procedures, welders and consumables [2]. By collecting and analysing the data from recent studies (2018-2025), the researchers found out that the standards focusing on prescribing strict recipes for welding and qualification procedures like DNVGL-ST-F101, including explicit heat input limits (typically 1.0-2.0 kJ/mm), obligatory post-weld heat treatment (PWHT), and rigorous consumable qualifications, perform well in Heat Affected Zone in sour gas service. The maximum hardness retirement i.e. 22 HRC (248 HV) obligated for sour media creates a critical limitation that forces optimization of welding procedures. The standards which focus on final quality or the end results rather than prescribing any specific method for producing the weld (Performance-based standards) like API 1104 remains less stringent which results in greater variation in properties around the weld i.e. the HAZ area impacting the service reliability in a worse manner during the sour media [3]. Contemporary world adopting new digital welding techniques for monitoring during weld production, prediction of the microstructural properties of HAZ based on machine learning and other advanced methods like hybrid welding processes which combines different precision welding techniques provide promising results for production of high quality and reliable welds which offer enhanced safety and reliability during sour service [4].