2.dr:2.3.1.2.1.dmls:3.2.fract_res

This page is the entry point of the future section dedicated to description of fatigue resistance of DMLS/SLM materials. In the initial version, it contains the results of studies of fracture resistance of MS1 steel in the A_MADAM project.

Fracture resistance of MS1 steel is determined experimentally, using the Inclined Edge Cracked Semi-Circular Bend (IACSB) specimen subjected to three-point bend loading.

In order to obtain the various combinations of modes, only the parameters *S _{2}/R* and α were varied in the testing campaign of A_MADAM project, while

Stress intensity factor (SFI) values were determined using two methods:

- Critical Fracture Load (PCR) Method
- Fitting of the displacement field measured by digital image correlation (DIC) method to Williams theoretical model

The following table presents the obtained results for *K _{I}* and

Configuration | PCR | DIC | ||||
---|---|---|---|---|---|---|

α (deg) | S (mm)_{1} | S (mm)_{2} | K (MPa·m_{I}^{-1/2}) | K (MPa·m_{II}^{-1/2}) | K (MPa·m_{I}^{-1/2}) | K (MPa·m_{II}^{-1/2}) |

0 | 42 | 42 | 44.7 | 0.0 | 75.0 | 0.2 |

10 | 42 | 44.7 | 16.6 | 69,0 | 19.0 | |

18 | 34.8 | 37.3 | 42,4 | 43.8 | ||

10.2 | 14.4 | 79.0 | 14.7 | 77.8 |

The obtained results may be explained by the multiaxial fracture model that introduces local stress (LS) criterium. Classical criteria, based on maximum tangential stress, such as the generalized maximum tangential stress (GMTS), can only predict fracture toughness of brittle materials. On the other hand, a major advantage of the LS criterium is that it can be applied to different materials (brittle and ductile), which experience either shear or tensile dominated crack propagation. Therefore, this model can be suitable for the strong, but at the same time ductile, maraging steel MS1. The LS mixed mode criterium is described by the following equation
with *s* = *K _{IIC}/K_{IC}*, then

The material parameter *s* is related to the material ductility and affects the critical plane orientation. If the parameter *s* is higher than 1, as in this case, then *A* = 9(*s*^{2}−1), *B* = *s* and γ = 0. The previous equation represents the implicit curve of the LS criterium, and the coefficient *s* can be determined numerically by fitting the experimental SIFs normalized to the *K _{IC}*=44.7MPa·m

The following figure illustrates the applicability of the criterion, with the red line (*s*=1.05, *K _{IIC}*=46.9MPa·m

2.dr/2.3.1.2.1.dmls/3.2.fract_res.txt · Last modified: 2022/01/09 19:33 by soskicz