![Sample our Physical Sciences journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/110819/TOC-Subject-Sample-2021-Physical-Sciences.jpg"})
ABSTRACT
In this paper, a numerical simulation method based on the camshaft casting process and crack expansion was proposed to study the propagation characteristics of casting hot cracks. The dynamic visualisation process of hot crack growth indicates that the formation of hot tear is dominated by opening mode cracks. And during the propagation process, the equivalent stress intensity factor at the crack front first decreases and then increases. Furthermore, the propagation characteristics of the crack under different hot tear initiation conditions were studied by this method. The results reveal that the expansion ability of a hot crack is affected by the equilibrium solidification scale, solidification sequence, and solidification path of the casting. Finally, using the microscopic morphology of the cracks, the semi-quantitative analysis of the elements illustrates that the carbon content decreases sharply at the crack formation site, while manganese and sulphur are relatively rich.
Nomenclature
| ρ | = | Density (kg/m3) |
| cp | = | Specific heat (J/(kg·K)) |
| T | = | Temperature (K) |
| t | = | Time (s) |
| λ | = | Heat conductivity coefficient (W/(m·K)) |
| Q | = | Latent heat (J) |
| nx, ny, nz | = | Normal direction cosine |
| h | = | Interface heat transfer coefficient (W/(m2·K)) |
| Tw | = | Boundary temperature (K) |
| Tf | = | Ambient temperature (K) |
| σ | = | Stress (MPa) |
| Dep | = | Elastic-plastic matrix of the elastic modulus, plastic modulus, and Poisson’s ratio |
| εe, εp, εT | = | Elastic strain, plastic strain, thermal strain |
| tcoh | = | Dendrite coherence time (s) |
| = | Effective plastic strain rate (s−1) | |
| ts | = | Solidus temperature time (s) |
| Γ | = | Integral loop around the crack tip |
| σij | = | Stress tensor |
| δij | = | Strain tensor |
| W | = | Strain energy density factor (MPa/m3) |
| q | = | Function with values between 0 and 1 in Γ |
| E | = | Young’s modulus (MPa) |
| ν | = | Poisson’s ratio |
| KI, KII, KIII | = | Mode I, II, III stress intensity factor (MPa·m1/2) |
| σαα | = | Tangential stress (MPa) |
| α | = | Kink angle of crack propagation (rad) |
| r | = | Distance from the crack tip (mm) |
| ∆ai | = | Expansion increment of node i (mm) |
| ∆amedian | = | Specified expansion increment at the median node of the stress intensity factor (mm) |
| ∆Ki | = | Equivalent stress intensity factor at node i (MPa·m1/2) |
| ∆Kmedian | = | Median of all equivalent stress intensity factors at the crack front (MPa·m1/2) |
| fs | = | Solid phase fraction |
| Keq | = | Equivalent stress intensity factor (MPa·m1/2) |
| R | = | Crack radius (mm) |
| d | = | Crack depth (mm) |
| θ | = | Crack inclination angle (°) |
| Abbreviations | = |
|
| CSC | = | Cracking Susceptibility Coefficient |
| RDG | = | Rappaz-Drezet-Gremaud (criteria) |
| SEM | = | Scanning Electron Microscope |
| SIF(s) | = | Stress Intensity Factor(s) |
| HTI | = | Hot Tearing Indicator |
| MTS | = | Maximum Tangential Stress |
| EDS | = | Energy Dispersive Spectrometer |
Acknowledgments
The authors greatly appreciate the financial support from the Zhejiang Provincial Natural Science Foundation of China (LZ23E060002, LZ23E050002), the Key R&D Program Project of Zhejiang Province (2019C01128, 2021C01053, 2023C01163), the Natural Science Foundation of China (52175257), and the General Research Project of Zhejiang Provincial Education Department (Y202147809).
Disclosure statement
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Data availability statement
Data will be made available on request.