Modelling and experimental study of fatigue of powder metal steel (FC-0205)

Figures & data

Table 1. Ambient tensile property data for FC-0205 steels

Initial porosity level	Temperature/K	σyield/MPa	σUltimate/MPa	Eyoung/GPa	Elongation to fracture/%
Low	293	466	569	167	1·8
High	293	349	387	143	0·9

1. FC-0205 steel alloy strain–life curve for different porosity levels and R ratios; A–C correspond to fractography analysis presented in Figs. 2, 3 and 4 respectively

2. Fracture surfaces of fatigue specimen A

3. Fracture surfaces of fatigue specimen B

4. Fracture surfaces of fatigue specimen C

5. Monotonic tension specimen reported by Allison et al.³⁶ with microstructural features similar to uniaxial fatigue specimens

Table 2. Macrovoid fatigue fracture surface characteristics

Initial porosity level	Temperature/K	Volume fraction macrovoids	Average NND/μm	Maximum NND/μm	Average pore diameter/μm	Maximum pore diameter/μm
Low	293	0·37	6·08	41·34	4·25	210·54
High	293	0·40	5·13	28·48	3·45	288·84

Table 3. Microvoid fatigue fracture surface characteristics

Initial porosity level	Temperature/K	Volume fraction microvoids	Average NND/μm	Maximum NND/μm	Average pore diameter/μm	Maximum pore diameter/μm	Intervoid ligament distance/μm
Low	293	0·86	0·40	1·27	0·33	7·19	0·07
High	293	0·87	0·25	1·96	0·13	7·14	0·12

6. Strain amplitude versus cycles to failure data and best fit relationships from results of fatigue tests on low and high porosity test specimens

Table

Constant description	Constant name	Constant value
Incubation
Porosity threshold	φth	0·0001
HCF coefficient in modified Coffin–Manson law	CNC	0·48
LCF coefficient in modified Coffin–Manson law	Cm	0·64
Ductility exponent in modified Coffin–Manson law	α	−05
Exponent in remote strain to local plastic shear strain	Q	2·42
Constant in remote strain to local plastic shear strain	y1	293·67
Linear constant in remote strain to local plastic shear strain	y2	300
Geometric factor in micromechanics study	ξpsi	2713·09
Exponent in micromechanics study	r	554·97
Exponent for elastic modulus effect sensitivity	Eexp	0·25
Exponent for particle effect sensitivity	PTexp	0·18
Small crack growth
Omega	ω	2
Initial crack size contribution	ai	0·56
Load path dependent and loading combination parameter	θ	0·25
Exponent in small crack growth	ζ	4·8
HCF constant in small crack growth	CI	80 000
LCF constant in small crack growth	CII	3·66
Crack growth rate constant	G	0·32
Crack tip displacement threshold	CTDTH	0·00029
Final crack size	afnl1	250
Exponent for grain size	DCSexp	0
Exponent for pore size	PRexp	0·5

Allison P. G., Horstemeyer M. F., Hammi Y., Brown H. R., Tucker M. T. and Hwang Y-K: ‘Microstructure–property relations of a powder metallurgy steel (FC-0205) under varying temperatures, strain rates, and stress states’, Mater. Sci. Eng. A, 2011, A529, 335–344.

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