EFFECT OF Mo AND Cr ON THE FRACTURE TOUGHNESS AND FATIGUE CRACK GROWTH RESISTANCE OF A COMPLEX-PHASE C-Mn-V STEEL

Godefroid, Leonardo Barbosa; Lima, Ana Paula da Silva; Vilela, Tamara Caroline Guimarães; Martins, Charles de Abreu; Fonstein, Nina

doi:10.20906/cps/cob-2015-0902

Cited by 1 publication

(3 citation statements)

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“…The values found for volume fraction of the phases/constituents agree with values commonly used in steels for the automotive industry [1][2][3]. It is interesting to note that up to a certain value of martensite volume fraction, usually 50%, the value of the threshold ΔK th will tend to increase, according to literature data [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] , improving the fatigue resistance of the material. However, these high values of martensite cannot be industrially considered, due to operational losses in the stamping stage for the manufacture of automotive components.…”

Section: Comparison Among the Steels Performancesupporting

confidence: 79%

“…Dual-phase steels, such as FB and FM, have good resistance to FCG, with greater values of ΔK th in comparison to FP steels. This resistance is attributed to the hard phase (bainite or martensite), which alters the crack path in the ferrite, causing tortuosity and branching, decreasing the driving force and the crack growth rate [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: /15mentioning

confidence: 99%

“…Due to the type of mechanical loads involved in the use of materials for the automotive industry, research on fatigue crack growth (FCG) has received great attention of the scientific community [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Studies carried out to estimate the life of a material under fatigue from concepts of Fracture Mechanics provide sigmoidal logarithmical da/dN versus ΔK curves, where da/dN is the FCG rate and ΔK (= K max -K min ) is the applied driving force for FCG.…”

Section: Introductionmentioning

confidence: 99%

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Effect of R load ratio on fatigue crack growth resistance of steels used in automotive applications: experimental results and use of performance prediction models

Godefroid¹,

Bernardes²,

Muniz³

et al. 2023

Tecnol. Metal. Mater. Min.

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This research consisted in comparing the fatigue crack growth (FCG) performance of four HSLA/ AHSS steels used in automotive applications and with different microstructures, and the application of some prediction models for the da/dN versus ΔK traditional sigmoidal curve as a function of the R load ratio. FCG tests were carried out on C(T) test specimens with R-ratios varying between 0.03 and 0.7. Using the original and empirical methodology proposed by Paris and Erdogan to describe the da/dN-ΔK relationship, the results showed significant differences in function of microstructure, and a deleterious effect of R-ratio increase on the crack growth rate. In order to check existing methodologies based on physical considerations for predicting the fatigue behavior of materials and the effect of the R-ratio mainly in the fatigue threshold ΔK th region, the well-known crack closure model proposed by Elber, an approach using two parameters as a driving force for the crack growth proposed by Vasudevan and co-authors and a combination of these two models recently proposed by Zhu and co-authors were compared. The manifestation of crack closure and its qualitatively expected dependence on the R-ratio were verified for the studied steels, but the Elber model was not able to provide a master curve that accurately summarized the effect of the R-ratio on the sigmoidal fatigue curve of steels. The combined use of two critical thresholds, ΔK th * and K max *, for predicting fatigue crack growth according to the Vasudevan model also did not provide accurate results in evaluating the effect of the R-ratio. Regardless of the verified dispersions, there is a connection between the two-parameter methodology and crack closure, hence the model by Zhu and co-authors could be a promising alternative. However, this model also showed significant dispersions and was unable to create a master curve to adequately predict the effect of R-ratio on crack growth. Thus, it can be concluded that this research topic is still open, requiring a more in-depth phenomenological knowledge to predict the effect of the R-ratio on FCG.

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