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Title: Fracture analysis in marine batteries by peridynamic theory
Author: Wang, Hanlin
ISNI:       0000 0004 7967 2247
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2018
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Hybrid propulsion system (HPS) has become popular in marine industry due to increasingly strict emission control standards. Hence, as one component in the system, marine batteries become attractive in marine design. Solid Oxide Fuel Cells (SOFCs) and lithium ion battery are the most promising energy storage devices in the electric propulsion system or HPS. Since silicon particles expand around 400% in volume during lithation, the battery electrodes will experience large volumetric change during normal battery cycling. As a result, misdistribution of stress may form inside the battery electrode. Therefore, degradation and delamination may occur in the battery electrode after many cycling process of marine battery. Many efforts have been devoted to investigate the damage in the marine battery. Majority of numerical simulation methods nowadays are based on classical continuum mechanics (CCM). Partial differential equations (PDEs) are applied in CCM to describe the motion of material structure. However, due to the limitation of PDEs, most of numerical techniques based on this theory have difficulties in describing the motion of material body with discontinuous fields, such as cracks and kinks. In order to have a better understanding of the fracture mechanics in marine battery, the peridynamic theory is applied in this thesis. Different from classical theory, peridynamic theory has applied spatial integral equations to describe the motion of material structure. Therefore, it has great advantage on fracture analysis of material structure. Based on the nonlocality of peridynamic theory, the peridynamic differential operator is introduced and studied in this thesis. Peridynamic differential operator has transformed the PDE into spatial integral equation under the framework of peridynamic theory. Hence, the governing equations of thermomechanical deformation and the coupled diffusive-mechanical deformation can be reformed in the framework of peridynamic theory which benefit the relative numerical simulations. In this thesis, the electrode models of SOFC and lithium ion battery in both two and three dimensions are selected. In order to validate the peridynamic theory, some results are compared with CCM. They have shown good agreement with each other. In the fracture analysis of SOFC, we have found out that fracture formation and evolution depend on the strength of interactions between electrode and electrolyte particles. For weak connection, the cracks will propagate along the interface of electrode and electrolyte. For uniform and strong connection, the cracks will start to propagate at regions with high geometrical singularity, such as pores or sharp corner regions. High hydrostatic stress is also located in these regions. In the fracture analysis of lithium ion battery, we have found out that facture formation and evolution depend on the hydrostatic stress and material properties. High hydrostatic stress generally reflects on high bond stretch value. Once the bond stretch value has exceed the critical value, cracks may form and propagate. Lithiated silicon, on the other hand, has decreased the critical bond stretch value. Hence, in some situations, crack propagation may not always be led by hydrostatic stress. Besides, the high hydrostatic stress will also increase the lithium ion concentration. Finally, peridynamic theory has shown excellent performance in the numerical estimation of damage formation and evolution in the marine batteries without pre-defined crack path or cohesive element as compared with classical techniques. It has provided an efficient and reliable tool in the design, manufacture, failure detection and life prediction of the marine battery in the real life.
Supervisor: Oterkus, Erkan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral