Self-pierce riveting (SPR) is one of the commonly used joining technologies in the automotive industry. Compared to other joining approaches, the SPR could deliver permanent connections by piercing in a single operation, which is particularly useful to assembly dissimilar materials that are difficult to weld, such as aluminum with steel. However, SPR joint results in the direct contact between two different materials, e.g. Al-Fe, which will greatly increase the potential of corrosion phenomena in the presence of electrolyte, due to the galvanic effect between dissimilar metals. The crevices between joining metals and metal-rivet, serve as the active sites for the initiation of the corrosion phenomena in corrosive environments. The corrosion often plays an important role in fatigue failures of the joints and reduces their useful life; the corrosion products could also cover the metal surface, leading to the change of the geometry and internal loading of the joint, causing unexpected stress concentrations and damages.

A comprehensive understanding on localized corrosion is necessary for both corrosion prognosis and corrosion protection for the SPR joint. The initiation and propagation of localized corrosion have been extensively investigated through experimental methods. However, it can be challenging to accurately detect the electrochemical kinetics of the localized corrosion using experimental methods due to the practical limitations of measurements, especially when considering the micro/crystal structures of the metals. Numerical simulation methods have been adopted in the recent decades to rationalize and quantify the corrosion phenomena. The numerical simulation models can be used to estimate the dissolution of metals and investigate the effects of various influencing factors and environmental conditions, e.g. geometric structures, microstructures and pH value, etc., based on the chemical and electrochemical theories. Nevertheless, in these models, the spatial and time dependences of the corrosion nucleation need to be provided prior to the simulation, which can be difficult to be predetermined sometimes.

In this study, a hybrid model is developed to simulate the corrosion process of the Al-Fe SPR joints, which consists of both stochastic corrosion nucleation information and finite element (FE) model-based corrosion evaluating prediction. The stochastic corrosion nucleation variables, including the location of the nucleation sites and their corrosion trigger time, are obtained through statistical analysis of the experimental samples. Then, these variables are imported into the physics-based FE model, and various corrosion scenarios are generated. The simulation results are statistically analyzed and validated with experiments. It is found that, the proposed hybrid model can reasonably predict the localized corrosion results of the SPR joints. In addition, parametric studies are conducted on different geometric and environmental parameters, e.g. width of the crevice gap and the diffusivities of ions in the electrolyte, etc., to provide insights to mitigate the corrosion and improve the reliability of the joint.  


Corrosion Modeling and Prognosis of the Al-Fe Self-Pierce Riveting Joints

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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