Parametric Optimization of Thermoelastic Energy Harvesting Systems under Low-Grade Thermal Cycling

Table 1. Material properties and baseline modelparameters used in the numerical analysis.

Parameter	Symbol	Value	Unit	Basis
Young’s modulus	E	210	GPa	AISI 4340 [13]
Thermal expansion coefficient	α	1.13x10^-5	K^-1	AISI E4340, normalized at 870 °C (MatWeb)
Yield strength	σ_y	860	MPa	AISI E4340, normalized at 870°C (MatWeb)
Specific heat capacity	c_p	475	J∙kg^-1∙K^-1	Typical 4000-series steel
Thermal conductivity	k	44.5	W∙m^-1∙K^-1	Typical steel
Baseline convection coefficient	h	50	W∙m^-2∙K^-1	Baseline model assumption; sensitivity tested
Load-transfer parameter	λ	0.50	-	Baseline value; sensitivity tested
Rod temperature-response fraction	ϕ	0.90	-	Model criterion
Yield safety factor	SF_y	1.5	-	Design assumption
Buckling safety factor	SF_b	1.5	-	Design assumption
Effective-length factor	K	1.0	-	Pinned-pinned Euler model
Reservoir temperature change	ΔT_R	120	K	Baseline operating condition
Rod temperature change	ΔT_rod	108	K	ϕ ΔT_R