Software analyzes one-bolt joints

April 1, 2004
Analyzing one-bolt joints with FEA would usually call for modeling a small assembly, friction, and contact. And unless the design is for a limited life, the complex effort is overkill. Boltcalc software may be a better way.

The software lets users study bolted joints in tension and shear. It works in just four steps: size the bolt, examine the bolt and tightening details, select a value for thread friction, and examine the finished bolt and joint. The software calculates values at each step, makes selections, and provides assistance. Users simply work through the steps, each represented by a red icon at the screen top.

Users first calculate a size of the needed bolt. They should know the clamping force, shear load, and clamp length or thickness of the bolted materials. The software can process up to six parameters for thorough analyses, but applying just the three mentioned tells it to assume values for the others so the analysis may proceed. Results for the first step produces two bolts that work in the proposed joint, their mechanical characteristics, and a few comments.

If uncertain what an input field is asking for, hitting the button next to the field cues up an explanation. Residual force, for instance, is a minimal clamp load needed to maintain joint integrity. This is frequently required when joints contain gaskets.

A screen with torque-tightening details include hole dimensions and allows assigning a grade or property class for bolts. A comment tells what assumptions the software makes. For instance, it uses the 0.2% permanent set stress because many materials do not have definite yield points.

One of several databases allows selecting material as defined by ISO, SAE, ASTM, or all of these. Another database for bolt threads include clearance dimensions for holes and has details on hundreds of different bolt threads. Others have information on torque ranges in metric and English, and friction coefficients.

Picking on the Fastener Head Marking Details tells how to read bolt qualities from the head markings. Often, there are just two markings: One to identify the manufacture and another to identify the property class or grade mark, essentially a strength indicator. In addition to calculations, the software tells whether or not the bolt will fail by an insufficient clamp load, bolt overload, fatigue failure, excess bearing stress, or thread shearing.

The software comes from Bolt Science Ltd., 15 Isleworth Dr., Chorley, Lancashire, United Kingdom PR7 2PU, +44 (0)1257 411503,


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