Monday, April 18, 2011

Bolt and Screw Calculations with the Bolted Connection Tool

You have a bolt or screw connection in your design, but you want to know if it will withstand a given load with the current number of fasteners, or if you'll need to add more.

You can use the Calculation tab of the Bolted Connection tool to do this.

 You can find the Bolted Connection tool on the Design tab when working with an assembly file:

Once you've used the Placement tools to place and specify the fastener components you want, you're ready to do the calculations. But you might notice the Calculation tab is not selectable:

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To proceed you can click the Enable/Disable Calculations button at the top right corner of the dialog box:

Once enabled you can click the Calculation tab and choose the Type of Strength Calculation:

Bolt Diameter Design
 Calculates the bolt diameter with respect to the specified load, geometric dimensions of joint, material properties, safety coefficient, and other factors.

Bolt Number Design
 Calculates the necessary number of bolts with respect to the specified load, geometric dimensions of the joint (including the specified bolt dimensions), material properties, safety coefficient, and other factors.

Bolt Material Design
 Select this option if geometric dimensions and number of bolts are fixed by the design, and the loading capacity can only be affected by the change of material.

Check Calculation
 Performs the strength check of a bolt during tightening and during operation, and checks allowable pressure in threads. This option is set as default option.

In this example I'll specify the max Axial and Tangent Force, and then click the Calculate button to show the results. You might need to click the >> buttons to expand the results panes on the right and bottom of the dialog box. Issues revealed by the calculations are denoted in red:

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In this example, I'll change the Number of Bolts to 4,  and then click Calculate to see if that resolves the issues:

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If the nature of the design limits the use of the number of bolts needed to pass the calculation test or is the desired number does not pass the max forces anticipated, you can also choose to change the plate or bolt materials in order to strengthen the connection. Use the check boxes for Plates Material and Bolt Material to do so.

You can also enable the Fatigue Calculation tab in order to run fatigue calculations:

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These calculator tools should provide you with a quick way to calculate the strength of your fastener connections. Keep in mind though, that the accuracy of these calculations is dependent upon the accuracy of the information you provide.