Machine Component Design: Analysis of Failure Points of a Connecting Rod of an Internal Combustion E

Project 4 of ME 480, Machine Component Design, focused on the ability to use given load information to trace the force flow through a machine, calculate stress components and apply appropriate failure criteria (both static and dynamic) to evaluate the possibility of part failure. A standard 2-stroke internal combustion engine operates at high speeds. The dynamic loads in the connecting rod become important in the failure analysis. In this project, a script was provided to calculate the parallel and transverse forces that the engine crank and piston apply to each end of the connecting rod. A free body diagram is illustrated below for reference, with inertial forces FIP, FIT, and the inertial moment, MI, labeled.

For the "Basic" Level of this project, the crank angle was identified for the following:

1. The greatest axial tensile stress

2. The greatest axial compressive stress

3. The greatest bending stress

4. The least bending stress

For each of these conditions, a FBD shows the magnitudes and directions of the loads along with shear, moment, and axial load diagrams underneath. Conservation of linear and angular momentum was applied to the rod, along with an analysis of statics of mechanics. This created a system of equations that was then used to determine the forces applied to the rod. The angles were found and the load diagrams were sketched accordingly (shown below.)

The "Medium" Level requires that for each of the four cases in the basic level, the location and magnitude of the critical stresses be determined and identified. In addition to this requirement, the analysis must show the stress range for the connecting rod and where it is most likely to fail. By using the equations for shear, normal, and bending stress, Tau = F/A, Sigma = F/A, and Sigma = Mc/I respectively, The area at the diameters of the rod is used for both the stresses in tearout and bearing shear. By dividing the connecting rod in six sections the moment can be found and the bending stresses at each point can be determined. Below are the final locations and stresses for this analysis. My full approach to this problem can be found under class projects on the main Portfolio page.