有限要素法による燃料電池用リフォーマ・チューブのクリープ・疲労寿命解析

概要

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The stress-strain behaviour of fuel-cell reformer tubes used in a creep-fatigue condition was analyzed by a finite element method. By applying Manson's strain-range-partitioning method to the stress-strain hysteresis loop obtained in this analysis, the fatigue life was estimated for the tubes made of low C-HP-Nb(0.15C-25Cr-35Ni-Nb steel) and HP-BST-M(0.49C-25Cr-35Ni-Nb-Ti steel), which have excellent creep-fatigue properties. Also, the cost efficiency (life/cost) was compared between these materials and a low cost alloy, HK40(25Cr-20Ni steel). The main results obtained are as follows; (1) The plastic strain range, Δε_p, is negligibly small in these tubes. Therefore, the total strain range, Δε_t, is nearly equal to the sum of the elastic and creep strain ranges, Δε_e+Δε_c. (2) The total strain range, Δε_t, is almost constant for a variety of creep constitutive equations. The creep strain range, Δε_c, therefore, can be decreased by using materials with high creep strength, such as HP-BST-M. (3) A longer tube life can be expected by using HP-BST-M because of its smaller Δε_c and better Δε_<ij>-N_<ij> properties than low C-HP-Nb. (4) The HP-BST-M is more cost-efficient than low cost HK40.
1989-02-15