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Proof Load Formula:
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Proof load is the maximum tensile force that a bolt can withstand without permanent deformation. It represents the load at which the bolt begins to yield but hasn't yet failed.
The calculator uses the proof load formula:
Where:
Explanation: The proof stress is a material property that indicates the stress at which a material begins to deform plastically, while the cross-sectional area determines how much force the bolt can withstand.
Details: Calculating proof load is essential for ensuring bolt integrity in structural applications, preventing joint failure, and meeting safety standards in engineering designs.
Tips: Enter proof stress in Pascals and cross-sectional area in square meters. Both values must be positive numbers. For standard bolts, refer to manufacturer specifications for proof stress values.
Q1: What's the difference between proof load and ultimate load?
A: Proof load is the maximum load before permanent deformation begins, while ultimate load is the maximum load before complete failure.
Q2: How do I determine the cross-sectional area of a bolt?
A: For standard bolts, use the tensile stress area which is slightly smaller than the nominal area. Refer to engineering tables for specific bolt sizes.
Q3: What are typical proof stress values for common bolt materials?
A: Grade 5 bolts typically have proof stress around 585 MPa, while Grade 8 bolts have about 825 MPa. Stainless steel bolts range from 210-550 MPa depending on grade.
Q4: Why is proof load important in bolted connections?
A: It ensures that bolts will not permanently deform under expected service loads, maintaining clamping force and joint integrity.
Q5: Should safety factors be applied to proof load calculations?
A: Yes, engineering designs typically apply safety factors to proof load values to account for uncertainties in loading conditions and material properties.