If you work with rubber and plastic materials frequently, you more than likely have access to a stress-strain curve for use in Simulation. What can you do, though, if you don’t have all the required material properties for analysis? If you’ve ever searched for material properties via MatWeb, IDES or other sources, you’ll likely find the hardness of plastics and rubbers listed in Shore-A or Shore-D – and no Young’s Modulus. Fear not! There is a simple calculation to convert a Shore durometer to Young’s Modulus, which is sufficient to get you started with your analysis work.
Before I show you the calculation, you should be aware that there is not a direct relationship between a Shore scale and Young’s Modulus! The calculation allows you to approximate ‘E’ based on a range of Shore-A (20 to 80) or Shore-D (30 to 85) durometers for simple static analysis.** If you routinely work with plastic and rubber materials, you should be using SolidWorks Simulation Premium with the actual stress-strain curve for the material(s) you design with!
For a durometer given in Shore-A, multiply this value by 0.0235. Then subtract 0.6403 from this result. The next step is to find the inverse base-e logarithm of this new result. The answer is an approximation for Young’s Modulus in megapascals (MPa). To convert this to pounds per square inch (psi), simply multiply this number by 145.0377. If you’re like me, word problems were never a strong suit! Here are the equations to input into Excel for a Shore-A or Shore-D durometer.
Shore-A to Young’s Modulus (in MPa):
Shore-D to Young’s Modulus (in MPa):
=EXP((Shore-D Durometer + 50)*0.0235-0.6403)
Replace the ‘Shore-A Durometer’ or ‘Shore-D Durometer’ with either a number or the cell location of the value.
** Making Engineering decisions based upon analysis results with this "material property conversion" is not recommended.
I have since written an updated blog post comparining Shore durometer and Finite Element Analysis comparing the workaround to the correct method for analyzing flexible, stretchy materials.