Joint Stress Analysis

Performing a structural analysis on a dovetail joint to determine both the locations of maximum stress and magnitude of the maximum tensile load.

While completing a solid mechanics course, Nathan and a group of colleagues were tasked with analyzing the stress patterns over a dovetail joint as it was subjected to several increasing nominal loads. This dovetail joint was to be within a compressor of a turbine engine. Based on the material properties of the dovetail, as well as the stress and strain levels measured under each successive loading, they were able to calculate where and when the joint would fail.

The dovetail joint was first fitted with strain gauges to record physical results based on the responses received under the set loadings. This data was then compared to the results obtained from using ANSYS Engineering Simulation Software.

Dovetail Strain Gauges
Von Mises Stress Diagram

Next, material properties of the dovetail, such as the Poisson’s ratio and elastic modulus were recorded. Using ANSYS, Nathan performed a finite element analysis of the dovetail configuration. The image to the left shows a plotted von Mises stress contour, representing the levels of stress at various locations on the joint when subjected to a 1 kN nominal load. 

The team also conducted a photo-elastic stress analysis, resulting in the isochromatic stress diagram and plot shown to the right. This allowed for further calculation of the maximum principal stress based on the highest fringe value, which was then compared to the maximum principal stress value calculated in the finite element analysis.

Nathan and his team used the strain gauges to confirm the results obtained from the finite element and photoelasticity analysis. This determined the maximum tensile load that the dovetail joint could handle. It also showed that the maximum stress areas on the joint were below the contact area on the curvature of the aerodisc, and the edge that lies above the contact area on the blades