High cycle fatigue behavior and life prediction for additively manufactured 17-4 PH stainless steel: Effect of sub-surface porosity and surface roughness

Romano, Simone; Nezhadfar, P.D.; Seifi, Mohsen; Beretta, Stefano

doi:10.1016/j.tafmec.2020.102477

Cited by 125 publications

(50 citation statements)

References 55 publications

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“…Having created an automated scheme for generating geometry, it is necessary to test that geometries created this way are similar to the geometries observed in real materials. Figure 1, taken from a paper by Romano et al, 13 shows porosity in additively manufactured 17‐4 PH stainless steel. The parts of the figure that are of most interest are (A) and the enlargement (C), which illustrate the as‐manufactured sub‐surface.…”

Section: Modeling Approachmentioning

confidence: 99%

Combined effect of both surface finish and sub‐surface porosity on component strength under repeated load conditions

McMillan

Jones

2020

Engineering Reports

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High duty engineering component life is usually demonstrated through extensive testing and statistical analysis applied to empirical curve-fit equations. Because of this, the extent of the testing required is huge and costly: it must consider the load cycle range and test to high numbers of cycles. Additive Manufacturing (AM) for high duty components has brought to the fore the question of the effect of porosity and surface roughness on fatigue life, and how the true life of a critical component can be assessed conservatively. The authors propose the first step toward the development of a fatigue model based on well-established engineering physics principles, by creating computational specimens with modeled surface roughness and porosity, and subjected to cyclic loading using Finite Element Analysis. They show that the combination of roughness features and sub-surface pores leads to an equivalent plastic strain distribution pattern that suggests an emergent physical process that has not been reported before, and which indicates that the component strength and life reduction arising from surface roughness can be made significantly worse by the presence of porosity. The development of such phenomenological understanding should lead to improved life prediction techniques, more cost effective test procedures, and the development of better AM methods.

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Section: Modeling Approachmentioning

confidence: 99%

Combined effect of both surface finish and sub‐surface porosity on component strength under repeated load conditions

McMillan

Jones

2020

Engineering Reports

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“…The primary origin for crack initiation in powder bed AM materials is the rough, as-produced, surface [ 3 , 4 ]. For a material for which the surface is treated or removed in order to smoothen it, volumetric defects such as a lack of fusion, gas porosity, keyhole porosity, or inclusions are the primary sources for crack initiation [ 4 , 5 , 6 ]. In 2016, Seifi et al [ 7 ] highlighted the need to account for AM defect populations in fatigue life modeling.…”

Section: Introductionmentioning

confidence: 99%

“…Fracture mechanical models (Kitagawa–Takahashi-type diagrams) have been shown to yield good results for fatigue strength predictions [ 8 , 9 , 10 , 11 , 12 ]. For deterministic modeling of fatigue life, fatigue crack growth (FCG) methods have been used [ 6 , 12 , 13 , 14 ]. These models are based on defect size measurements.…”

Section: Introductionmentioning

confidence: 99%

Defects in Electron Beam Melted Ti-6Al-4V: Fatigue Life Prediction Using Experimental Data and Extreme Value Statistics

et al. 2021

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Electron beam melting is a powder bed fusion (PBF) additive manufacturing (AM) method for metals offering opportunities for the reduction of material waste and freedom of design, but unfortunately also suffering from material defects from production. The stochastic nature of defect formation leads to a scatter in the fatigue performance of the material, preventing wider use of this production method for fatigue critical components. In this work, fatigue test data from electron beam melted Ti-6Al-4V specimens machined from as-built material are compared to deterministic fatigue crack growth calculations and probabilistically modeled fatigue life. X-ray computed tomography (XCT) data evaluated using extreme value statistics are used as the model input. Results show that the probabilistic model is able to provide a good conservative life estimate, as well as accurate predictive scatter bands. It is also shown that the use of XCT-data as the model input is feasible, requiring little investigated material volume for model calibration.

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“…[20][21][22][23] Taking advantage of the design freedom in AM, parts are likely to contain notched regions and in addition manufacturing defects. Due to this, it is important to address issues related to size effects, both for determining the critical size and location of the defects 24,25 and for determining the appropriate dimensions of testing specimens 22,23 In this work, the fatigue behaviour of AM Inconel 718 are investigated in the AB and the heat-treated (HT) states. This was done for both notched and unnotched specimens.…”

Section: Introductionmentioning

confidence: 99%

Fatigue assessment of as‐built and heat‐treated Inconel 718 specimens produced by additive manufacturing including notch effects

Solberg

Wan

2020

Fatigue Fract Eng Mat Struct

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The fatigue behaviour of notched and unnotched specimens produced by additively manufactured Inconel 718 were analysed in the as‐built and heat‐treated conditions. The surfaces display high roughness and defects acting as fatigue initiation sites. In the as‐built condition, fine subgrains were found, while in in the heat‐treated state, the subgrains were removed and the dislocation density recovered. SN‐curves are predicted based on tensile properties, hardness and defects obtained by fractography, using the area‐method.

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High cycle fatigue behavior and life prediction for additively manufactured 17-4 PH stainless steel: Effect of sub-surface porosity and surface roughness

Cited by 125 publications

References 55 publications

Combined effect of both surface finish and sub‐surface porosity on component strength under repeated load conditions

Combined effect of both surface finish and sub‐surface porosity on component strength under repeated load conditions

Defects in Electron Beam Melted Ti-6Al-4V: Fatigue Life Prediction Using Experimental Data and Extreme Value Statistics

Fatigue assessment of as‐built and heat‐treated Inconel 718 specimens produced by additive manufacturing including notch effects

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