Question

AISI 1045 steel can be assumed to have an S-N curve of the form ơa-AN . Some test data for unnotched specimens under axial cyclic stress with zero mean are a) Plot these data on log-log coordinates and determine the approximate b) Obtain refined values for A and B using a linear least-squares fit to log Nf provided beloww. values for the constants A and B. versus log σα 524 459 410 352 315 270 241 Nf, cycles 257 1494 6 749 19 090 36 930 321 500 2 451 000

Answer 1

σa	Nf	U=log(X)	V=log(Y)	U2	UV
524	257	2.409933	2.719331	5.807778	6.553407
459	1494	3.174351	2.661813	10.0765	8.449527
410	6749	3.829239	2.612784	14.66307	10.00497
352	19090	4.280806	2.546543	18.3253	10.90125
315	36930	4.567379	2.498311	20.86095	11.41073
270	321500	5.507181	2.431364	30.32904	13.38996
241	2451000	6.389343	2.382017	40.82371	15.21952
		30.15823	17.85216	140.8864	75.92938
		∑U	∑V	∑U2	∑UV

1000 T o,-865.09N f-0.09 100 Series1 10 Power (Se riesi1) 10000 100oo 100 Nf

NA Tapimn beth sidas a t 30 . I 58 23D = 17-85216--(2) 30,15323 a t ічо.88648-7592938- Scanned with CamScanner

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