A stress compatible finite element for implant/cement interface analyses.

Area of Science:

• Computational mechanics
• Materials science
• Biomedical engineering

Background:

• Conventional displacement finite element methods often predict inaccurate, discontinuous stresses at bimaterial interfaces.
• This limitation is particularly problematic when analyzing components made of dissimilar materials.

Purpose of the Study:

• To develop and validate a new finite element capable of enforcing normal and shear stress continuity at bimaterial interfaces.
• To address the shortcomings of traditional methods in predicting interface stress distributions.

Main Methods:

• Development of a novel five-node isoparametric quadrilateral finite element with an interface node.
• Validation through stress distribution tests at dissimilar material interfaces, comparing results with analytical solutions and conventional finite element methods (SAP-IV).
• Application to an axisymmetric model of a knee tibial implant to demonstrate practical utility.

Main Results:

• The proposed element accurately enforces stress continuity at bimaterial interfaces.
• Validation tests showed superior reliability compared to conventional methods, which struggled with interpretable interface stress values.
• Convergence studies confirmed the new element's effectiveness in analyzing the knee tibial implant model.

Conclusions:

• The new interface finite element provides a reliable solution for accurate stress analysis at bimaterial interfaces.
• It overcomes the significant limitations of conventional methods, offering interpretable and accurate stress predictions.
• Demonstrated superiority in biomechanical applications, such as knee implant analysis, highlights its practical value.