Optimization of a Connecting Rod (Stress Analysis)

A connecting rod is a rigid member which connects a piston to a crank or crankshaft. The connecting rod is best known because of its use in internal combustion (IC) piston engines, such as vehicle engines. You can also find connecting rods in some compressor and pump designs. Connecting rods are an important part of the automotive industry. Engines today need more power and greater reliability; therefore the connecting rod should be of higher strength and stiffness but at the same time should be lighter in weight and dimensions.

Much R&D has been performed on connecting rods in the last several decades, but there is still a lot that needs to be accomplished. Stress analysis is an important factor for selection of the proper material, design validation, validation of the fabrication process, and fatigue life. Metal foil strain gage plays an important role in design of connecting rods, helping to reduce stress, weight and optimize selection of the raw material.

Failure of connecting rods, usually called throwing a rod, is one of the most common causes of catastrophic engine failure in cars. The connecting rod is subjected to different kinds of loads. The dominant stress induced in each connecting rod during its normal operation is a combination of axial and bending stress.

In this iNotes Video , Mike is explaining how to analyze various stresses acting on a connecting rod during its operation. Mike  shows an example of using several different foil strain gages such as a strip gage, stacked rosette and a single strain gage to measure  a strain gradient, peak strain, principles strains and there directions and last but not least, to monitor tensile and compression load. It can also be observed by using strain gages where material can be removed from minimum stressed areas and can be added to sections of higher stress.  Stress analysis using strain gages can be accomplished on any structural material; carbon steel, mild steel, powered metal, brass and aluminum.

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