Guitar String Failure

 

An ordinary guitar has six strings, usually made up of metal, polymer or animal gut. These strings are under many kilograms of tension. Guitar string failure while turning the strings is a nuisance for guitarists. How these strings fail at the microscopic level is the topic of my final project for OPT 407.

In a 6-string guitar, the first string (lowest) is the E string and has the lowest pitch. It is an obvious assumption that we should expect this string to have a higher rate of failure that the remaining five. However, it turns out that the string G (third from lowest) has the highest rate of failure.

 

Therefore, my study involves the comparison of string failure between the third string and the lower two. I also decided to study the breakage of nylon strings to see how the polymer in these strings would fail compared to metal strings.

 

 

 

 

 

 

 

Experimentation

For my experiments, I used a classical guitar with an additional steel string tuner on top. The metal strings used were EJ16 Phosphor Bronze, Light, 12-53 by D’Addario. Strings A and E were cylindrically extruded out of plain steel. String G has a hexagonal shaped high carbon steel core, wound by Phosphor Bronze. The Phosphor Bronze alloy used was 92% Copper and 8% Tin. Wound strings have a metal winding to increase diameter and mass of the string so that it can be tuned to a lower pitch than a regular string. As seen in the tension chart shown below that was provided by the offical, D'Addario website, the value of tension per unit length is the highest for String G.

 

 

Used Microscopic Techniques

·   Light Microscopy

·   Secondary Electron Microscopy

·   Backscatter Electron Microscopy

 

Used Non-Microscopic Techniques

·   Sputter Coating (for the nylon strings)

·   Image colorization

. Analglyph images

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