Hi,

I am simulating a bracket to hold up an object of 10kg on one side and is fixed on the other side. The bracket is mounted by 4 socket head alloy steel bolts. I first tried to create the connector bolts myself in SolidWorks with inputting the thread count and bolt strength of the selected bolts in the strength data menu. I then inputted the pre-load as an axial force using F=K(At)(Sp) (where: K=constant, At=tensile stress area, Sp=proof strength) for each bolt. All values found were from the textbook Fundamentals of Machine Component Design by Robert C. Juvinall. When I ran the simulation I was getting ridiculously high stresses that did not make sense. Then I realized that SolidWorks has a tool to convert Toolbox fasteners to bolt connections. So, I inputted the 4 socket head bolts from the SolidWorks toolbox and used the tool to convert them to bolt connections in the simulation menu. The software automatically inputted the tensile stress area, bolt strength, and pre-load. All the values that I previously inputted in my first try matched what the software assumed, expect for the pre-load. I did some research on how SolidWorks calculates the pre-load and I found that in the equation specified above, they only use 20% of the yield strength in their calculation. I was wondering if anyone knew the reasoning of why they assume 20% of the yield strength as the proof strength in the calculation for pre-load?

Thanks