Experimental study on fatigue properties of Q420C steel welded joints at room temperature

Yang, Liguo; Xing, Yongming

doi:10.1590/1679-78256808

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Latin American Journal of Solids and Structures

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ORIGINAL ARTICLE • Lat. Am. j. solids struct 19 (1) • 2022 • https://doi.org/10.1590/1679-78256808 copy

Experimental study on fatigue properties of Q420C steel welded joints at room temperature

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

To evaluate the fatigue life of Q420C steel welded joints, fatigue tests were performed on butt-welded joints, cross-butt-welded joints and cross-fillet-welded joints. The fatigue strength S-N curves of the joints were fitted. Then the formation and development of fatigue cracks were analyzed by fracture morphology. The fatigue properties of joints were compared with literature data and standard curves. The results showed that the fatigue test data of the three types of welded joints were roughly above the standard curves. Moreover, the fatigue strength of butt-welded joint was significantly higher than the calculated values of standards, indicating a large safety margin. The test value of cross-butt-welded joint was close to the calculated values of standards, so it is suggested to moderately reduce the standard values. In addition, all the three standards could well predict the fatigue life of cross-fillet-welded joint. The fracture morphology of the specimens showed the development process of fatigue damage, and the fatigue displacement curve and damage curve proved the formation of the fatigue fracture in specimens.

Keywords
Butt-welded joint; Cross-butt-welded joint; Cross-fillet-welded joint; Fatigue damage; S-N curve

Graphical Abstract

Chemical compositions	C	Si	Mn	Cr	Mo	B	V	C_eq
Measured value	0.14	0.042	0.8	0.015	0	-	0	0.278
Factory value	0.07	0.19	1.08	0.02	0.004	-	0	-
Product standard	0.20	0.50	1.7	0.30	0.20	-	0.20	0.45

Welding method	Diameter of electrode /mm	Welding current/A	Welding voltage/V	Welding speed/cm·min^-1
Manual arc welding	3.2	110	40	20~25

Connection type	Test type	Group type	Number
Butt-welded joint	Mechanical test	MDD	3
Butt-welded joint	Fatigue test	MDX	12
Cross-butt-welded joint	Mechanical test	SDD	3
Cross-butt-welded joint	Fatigue test	SDX	12
Cross-fillet-welded joint	Mechanical test	SJD	3
Cross-fillet-welded joint	Fatigue test	SJX	12

Connection type	Classes	Parameter C0	SD	m
Butt-welded joint	E	3.289×1012	0.2509	3
Cross-butt-welded joint	F2	1.231×1012	0.2279	3
Cross-fillet-welded joint	W1	2.5×1011	0.2140	3

Connection type	Classes	Parameter C	Parameter β
Butt-welded joint	Z2	861×1012	4
Cross-butt-welded joint	Z6	1.46×1012	3
Cross-fillet-welded joint	Z8	0.72×1012	3

Connection type	BS7608: 2014	GB50017-2017	ANSI/AISC360-10
Butt-welded joint	S=14857.29N^(-1/3)	S=5419.92N^-0.25	S=15652.89N^-0.333
Cross-butt-welded joint	S=10707.39N^(-1/3)	S=11333.88N^(-1/3)	S=11187.54N^-0.333
Cross-fillet-welded joint	S=6294.15N^(-1/3)	S=8954.64N^(-1/3)	S=6917.13N^-0.333

Connection type	Specimen number	F_y/kN	F_u/kN	f_y/MPa	f_u/MPa	F_y/F_u
Butt-welded joint	MDD-1	54.5	63.2	454.2	526.7	0.86
	MDD-2	57.5	63.1	479.2	525.8	0.91
	MDD-3	60.5	69.7	504.2	580.8	0.87
	average	57.5	65.3	479.2	544.2	0.88
Cross-butt-welded joint	SDD-1	54.0	62.3	450.0	519.2	0.87
	SDD-2	55.2	63.4	460.0	528.3	0.87
	SDD-3	58.0	65.4	483.3	545.0	0.89
	average	55.7	63.7	464.2	530.8	0.87
Cross-fillet-welded joint	SJD-1	55.0	63.3	458.3	527.5	0.87
	SJD-2	56.3	63.6	469.2	530.0	0.89
	SJD-3	55.2	63.9	460.0	532.5	0.86
	average	55.5	63.6	462.5	530.0	0.87

Specimen number	K	S_max /MPa	F /Hz	S /MPa	N/cycle
MDX-1	0.62	297.08	10	267.38	1625182
MDX-2	0.70	335.42	10	301.88	157084
MDX-3	0.68	325.92	10	293.33	380915
MDX-4	0.60	287.50	10	258.75	1432011
MDX-5	0.65	311.46	10	280.31	458116
MDX-6	0.58	277.92	10	250.13	1828264
MDX-7	0.62	297.08	10	267.38	703875
MDX-8	0.60	287.50	10	258.75	1669477
MDX-9	0.55	263.54	10	237.19	1953255
MDX-10	0.70	335.42	10	301.88	241907
MDX-11	0.66	316.25	10	284.63	382975
MDX-12	0.63	301.88	10	271.69	945216

Specimen number	K	S_max /MPa	F /Hz	S/MPa	N /Cycle
SDX-1	0.70	335.42	10	301.88	26561
SDX-2	0.60	287.50	10	258.75	58686
SDX-3	0.55	263.54	10	237.19	38878
SDX-4	0.45	215.63	10	194.06	120228
SDX-5	0.40	191.67	10	172.50	241913
SDX-6	0.30	143.75	10	129.38	662669
SDX-7	0.28	134.17	10	120.75	456426
SDX-8	0.25	119.79	10	107.81	1052318
SDX-9	0.22	105.42	10	94.88	2000000
SDX-10	0.24	115.00	10	103.50	2000000
SDX-11	0.27	129.38	10	116.44	1075740
SDX-12	0.23	95.83	10	86.25	980012

Specimen number	K	S_max /MPa	F /Hz	S/MPa	N /Cycle
SJX-1	0.25	119.79	10	107.81	515925
SJX-2	0.22	105.42	10	94.88	379449
SJX-3	0.20	95.83	10	86.25	2000000
SJX-4	0.28	134.17	10	120.75	186346
SJX-5	0.19	91.04	10	81.94	2000000
SJX-6	0.21	100.63	10	90.56	1734188
SJX-7	0.24	115	10	103.50	1094757
SJX-8	0.26	124.58	10	112.13	914886
SJX-9	0.27	129.38	10	116.44	1184697
SJX-10	0.30	143.75	10	129.38	277720
SJX-11	0.29	138.96	10	125.06	322692
SJX-12	0.23	110.21	10	99.19	480348

Type	General form		Logarithmic form
Type	S-N equation	95% S-N equation	S-N equation	95% S-N equation
MDX series	S=748.69N-0.07582	S=694.541N-0.07582	logS=2.8743-0.07582logN	logS=2.8417-0.07582logN
SDX series	S=3794.90N-0.2521	S=3531.83N-0.2521	logS=3.792-0.2521logN	logS=3.5480-0.2521logN
SJX series	S=1035.86N-0.1684	S=883.08N-0.1684	logS=3.0153-0.1684logN	logS=2.9460-0.1684logN

Connection type	S /MPa
Connection type	Fitted value	95% survival	BS7608: 2014	GB50017-2017	ANSI/AISC360-10
Butt-welded joint	249.2	231.2	117.9	144.1	124.8
Cross-butt-welded joint	97.9	91.1	85	90	89.2
Cross-fillet-welded joint	90	76.7	50	71.1	55.2

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