Sulfide Solid Electrolyte Viscoplasticity and Interface Contact Mechanics
Sulfide solid-state cells require continuous external stack pressure between 5 and 10 MPa to overcome viscoplastic voiding and maintain intimate interface contact.
Greenwood-Williamson Contact Mechanics
Meaning
Statistical models describing the contact between a smooth plane and a nominally flat surface covered in spherical asperities provide the basis for calculating electrical and thermal conductivity at interfaces. The greenwood-williamson contact mechanics model assumes that each microscopic peak deforms independently under an applied load. This approach allows engineers to estimate the true contact area without needing a full map of the surface texture.
Asperity Distribution
Height variations across a surface follow a Gaussian or exponential distribution in most industrial materials. Applying greenwood-williamson contact mechanics requires knowing the density and average radius of these peaks. When the surfaces move closer together, more peaks come into contact and the load is shared among them.
Higher standard deviations in peak height result in fewer initial contact points and higher initial resistance. This mathematical treatment links macroscopic pressure to microscopic contact events.
Elastic Deformation
Individual peaks are assumed to behave elastically according to Hertzian theory until a specific pressure threshold is reached. Under greenwood-williamson contact mechanics, the total contact area is directly proportional to the applied force in many practical scenarios. This linear relationship simplifies the prediction of joint performance in battery connectors.
Contact Conductance
Electrical current passes only through the established spots where the asperities touch. The principles of greenwood-williamson contact mechanics show that increasing the clamping force improves conductance by creating more pathways. This calculation helps in sizing fasteners for high current busbars.