# Healing of Fatigue Crack in 1045 Steel by Using Eddy Current Treatment

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

_{max}= 53 KN and a frequency of ƒ = 10 Hz for 10

^{4}cycle, while all of the tests in group B were performed at a stress ratio of R = 0.14, a maximum force of F

_{max}= 21 KN and a frequency of ƒ = 10 Hz for 5 × 10

^{3}cycle. The fatigue cracks initiated and propagated along the cutting lines during the fatigue tests. The morphologies of the fatigue cracks before and after the eddy current treatment were observed on an OLYPUS optical microscope and the fatigue crack photographs taken through the OLYMPUS optical microscope were stitched together to get full views of the fatigue cracks.

## 3. Results and Discussion

#### 3.1. Axial Crack

_{max}≈ 351 MPa, wherein the Young’s modulus E of 1045 steel was 210 GPa. For the specimens A2 and A3, we had ΔT ≈ 224 °C and 331 °C, respectively, and then the maximum theoretical thermal compressive stress σ

_{max}≈ 644 MPa and 861 MPa, respectively. Obviously, the thermal compressive stress around the crack tip increased gradually with the increased duration. Under the action of high compressive stress, the two sides of the crack would be pushed toward each other, and would close when their distance was small enough and the higher temperature existed around the crack, indicating that the crack tip had a high probability of being closed during the eddy current treatment. However, the crack healing in the crack tip area may not result only from the temperature change, it may also be related to the profile of the crack tip and the temperature of the metal matrix, etc., since different healing levels were achieved in specimens A1, A2 and A3. For example, the long treatment time would increase the temperature of the specimen matrix; but some studies found that high temperatures probably caused shrinkage and the smoothing of crack edges when the specimens were subject to hot isostatic pressing treatment, and thus led to the healing failure of the cracks [21].

#### 3.2. Radial Crack

## 4. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

- Griffith, A.A. Phenomena of rupture and flow in solids. Philos. Trans. R. Soc. Lond. Ser. A
**1920**, 221, 163–198. [Google Scholar] [CrossRef] - Rohatgi, P.K. Al-shape memory alloy self-healing metal matrix composite. Mater. Sci. Eng. A
**2014**, 619, 73–76. [Google Scholar] [CrossRef] - Tittelboom, K.V.; Belie, N.D. Self-healing in cementitious materials. Materials
**2013**, 6, 2182–2217. [Google Scholar] [CrossRef] - Lucci, J.M.; Ruzek, A.; Misra, S.K.; Rohatgi, P.K.; Amano, R.S. Self-healing in Metal Castings; Transactions of the American Foundry Society: Schaumburg, IL, USA, 2011. [Google Scholar]
- Wei, D.; Han, J.; Jiang, Z.Y.; Lu, C.; Tieu, A.K. A study on crack healing in 1045 steel. J. Mater. Process. Technol.
**2006**, 177, 233–237. [Google Scholar] [CrossRef] - Yu, H.L.; Liu, X.H.; Li, X.W.; Godbole, A.R. Crack healing in a low-carbon steel under hot plastic deformation. Metal. Mater. Trans. A
**2014**, 45, 1001–1009. [Google Scholar] [CrossRef] - Zhou, Y.Z.; Qin, R.S.; Xiao, S.H.; He, G.H.; Zhou, B.L. Reversing effect of electropusing on damage of 1045 steel. J. Mater. Res.
**2000**, 15, 1056–1061. [Google Scholar] [CrossRef] - Barnak, J.P.; Sprecher, A.F.; Conrad, H. Colony (grain) size reduction in eutectic Pb-Sn castings by electroplusing. Scr. Metall. Mater.
**1995**, 32, 879–884. [Google Scholar] [CrossRef] - Golovin, Y.I.; Finker, V.M.; Sletkov, A.A. Effects of current pulses on crack propagation kinetics in silicon iron. Problemy Prochnosti.
**1977**, 2, 86–91. [Google Scholar] [CrossRef] - Levitin, V.V.; Loskutov, S.V. The effect of a current pulse on the fatigue of titanium alloy. Solid State Commun.
**2004**, 131, 181–183. [Google Scholar] [CrossRef] - Zhou, Y.Z.; Guo, J.D.; Gao, M.; He, G.H. Crack healing in a steel by using electropulsing technique. Mater. Lett.
**2004**, 58, 1732–1736. [Google Scholar] [CrossRef] - Zhou, Y.Z.; You, Z.; He, G.H.; Zhou, B.L. The healing of quenched cracks in 1045 steel under electropulsing. J. Mater. Res.
**2001**, 16, 17–19. [Google Scholar] - Tang, Y.P.; Hosoi, A.; Morita, Y.; Ju, Y. Restoration of fatigue damage in stainless steel by high-density. Int. J. Fatigue
**2013**, 56, 69–74. [Google Scholar] [CrossRef] - Tang, Y.P.; Hosoi, A.; Morita, Y.; Ju, Y. Effect of high-density electric current on the microstructure and fatigue crack initiation of stainless steel. Mater. Trans.
**2013**, 54, 2085–2092. [Google Scholar] - Yu, T.; Deng, D.W.; Wang, G.; Zhang, H.W. Crack healing in SUS304 stainless steel by electropulsing. J. Clean Prod.
**2016**, 113, 989–994. [Google Scholar] [CrossRef] - Gallo, F.; Satapathy, S.; Chandar, K.R. Plastic deformation in electrical conductors subjected to short-duration current pulse. Mecha. Mater.
**2012**, 55, 146–162. [Google Scholar] [CrossRef] - Zhu, Y.H.; To, S.; Lee, W.B.; Liu, X.M.; Jiang, Y.B.; Tang, G.Y. Effects of dynamic eletropulsing on microstructure and elongation of Zn-Al alloy. Mater. Sci. Eng. A
**2009**, 501, 125–132. [Google Scholar] [CrossRef] - Whitaker, J.C. The Electronics Handbook, 2nd ed.; CRC Press: Boca Raton, FL, USA, 2005; pp. 164–167. [Google Scholar]
- Lieberman, M.A.; Lichtenberg, A.J. Principles of Plasma Discharges and Materials Processing, 2nd ed.; Wiley-Interscience: Hoboken, NJ, USA, 2005; pp. 544–546. [Google Scholar]
- Tang, D.W.; Zhou, B.L.; Cao, H.; He, G.H. Thermal stress relaxation behavior in thin films under transient laser-pulse heating. J. Appl. Phys.
**1993**, 73, 3749–3752. [Google Scholar] [CrossRef] - Zhang, Y.J.; Han, J.T.; Duan, L.H. Physical simulation for crack healing in metal component. In Proceedings of the CSM 2003 Annual Meeting Proceedings, Beijing, China, October 2003.
- Lai, X.P. Chinese Aeronautical Material Manual (Structural Steel and Stainless Steel), 2nd ed.; Standard Press of China: Beijing, China, 2001; p. 40. [Google Scholar]
- George, E.T. Steel Heat Treatment Equipment and Process Design, 2nd ed.; CRC Press: Boca Raton, FL, USA, 2006; p. 312. [Google Scholar]

**Figure 2.**Photographs of the copper coil and specimen: (

**a**) specimen within copper coils; (

**b**) infrared temperature image of the surface of specimen; (

**c**) measurement points on the surface of specimens.

**Figure 4.**Schematics of eddy current within tubular specimens: (

**a**) specimen without cracks; (

**b**) specimen with axial cracks.

**Figure 5.**Optical microscope images for fatigue cracks of A1: (

**a**) fatigue crack before the eddy current treatment; (

**b**) fatigue crack after the eddy current treatment; (

**c**) crack initiation zone of specimen A1 before the eddy current treatment; (

**d**) crack initiation zone of specimen A1 after the eddy current treatment.

**Figure 6.**Optical microscope images for fatigue cracks of specimen A2: (

**a**) fatigue crack before the eddy current treatment; (

**b**) fatigue crack after the eddy current treatment; (

**c**) crack initiation zone of specimen A2 before the eddy current treatment; (

**d**) crack initiation zone of specimen A2 after the eddy current treatment; (

**e**) marked area E in Figure 6b; (

**f**) marked area F in Figure 6b.

**Figure 7.**Optical microscope images for fatigue crack of specimen A3: (

**a**) fatigue crack before the eddy current treatment; (

**b**) fatigue crack after the eddy current treatment; (

**c**) crack initiation zone of specimen A3 before the eddy current treatment; (

**d**) crack initiation zone of specimen A3 after the eddy current treatment; (

**e**) marked area E in Figure 7b; (

**f**) marked area F in Figure 7b; (

**g**) marked area G in Figure 7b; (

**h**) marked area H in Figure 7b.

**Figure 8.**Schematics of eddy current around a crack: (

**a**) whole crack; (

**b**) the right end of whole crack.

**Figure 9.**Optical microscope images for fatigue cracks of A1: (

**a**) fatigue crack before the eddy current treatment; (

**b**) fatigue crack after the eddy current treatment; (

**c**) crack tip area of specimen A1 before the eddy current treatment; (

**f**) crack tip area of specimen A1 after the eddy current treatment.

**Figure 10.**Optical microscope images for fatigue cracks of A2: (

**a**) fatigue crack before the eddy current treatment; (

**b**) fatigue crack after the eddy current treatment; (

**c**) crack tip area of specimen A2 before the eddy current treatment; (

**d**) crack tip area of specimen A2 after the eddy current treatment.

**Figure 11.**Optical microscope images in local area of specimen A3: (

**a**) fatigue crack before the eddy current treatment; (

**b**) fatigue crack after the eddy current treatment; (

**c**) crack tip area of specimen A3 before the eddy current treatment; (

**d**) crack tip area of specimen A3 after the eddy current treatment.

**Figure 12.**Schematics of the fatigue crack healing process. (

**a**) the detour of eddy current; (

**b**) the appearance of the compressive stress and the bridging; (

**c**) the appearance of breakdown and crack tip healing; (

**d**) continuous crack healing.

**Figure 14.**Optical micrographs of specimens B1, B2, and B3 after the eddy treatment: (

**a**) B1; (

**b**) B2; (

**c**) B3.

Group | Specimen | Duration/Second | T_{max} of O/°C | T_{max} of M/°C | T_{max} of N/°C | T_{max} of K/°C | T_{max} of L/°C | T_{average} of M, N, K, L/°C |
---|---|---|---|---|---|---|---|---|

Group A | A1 | 1 | 226 | 103 | 112 | 75 | 68 | 90 |

A2 | 2 | 376 | 205 | 187 | 110 | 105 | 152 | |

A3 | 3 | 781 | 552 | 572 | 356 | 324 | 451 | |

Group B | B1 | 1 | 155 | 154 | 160 | 151 | 162 | 157 |

B2 | 2 | 194 | 193 | 182 | 200 | 189 | 191 | |

B3 | 3 | 496 | 498 | 486 | 502 | 483 | 492 |

**Table 2.**Thermal expansion coefficients α of 1045 steel [22].

T/°C | 20–200 | 20–300 | 20–400 | 20–500 | 20–600 | 20–700 | 20–800 |
---|---|---|---|---|---|---|---|

α/(10^{−6}mm/°C) | 12.32 | 13.09 | 13.71 | 14.18 | 14.67 | 15.08 | 12.50 |

© 2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Yang, C.; Xu, W.; Guo, B.; Shan, D.; Zhang, J.
Healing of Fatigue Crack in 1045 Steel by Using Eddy Current Treatment. *Materials* **2016**, *9*, 641.
https://doi.org/10.3390/ma9080641

**AMA Style**

Yang C, Xu W, Guo B, Shan D, Zhang J.
Healing of Fatigue Crack in 1045 Steel by Using Eddy Current Treatment. *Materials*. 2016; 9(8):641.
https://doi.org/10.3390/ma9080641

**Chicago/Turabian Style**

Yang, Chuan, Wenchen Xu, Bin Guo, Debin Shan, and Jian Zhang.
2016. "Healing of Fatigue Crack in 1045 Steel by Using Eddy Current Treatment" *Materials* 9, no. 8: 641.
https://doi.org/10.3390/ma9080641