#round 3 "Bolt Torque and Preload Analysis 'This calculator determines the required tightening torque for a bolted connection using the torque-tension relationship. It evaluates bolt preload capacity, applied clamping force, and resulting bolt stress against the proof strength. "References 'Ref 1: Bickford, J.H., 2007, Introduction to the Design and Behavior of Bolted Joints, 4th Edition, CRC Press 'Ref 2: VDI 2230, 2003, Systematic Calculation of High Duty Bolted Joints "Inputs '

Bolt Geometry

' Nominal bolt diameter -'d = ? {20}mm ' Tensile stress area -'A_s = ? {245}mm^2 '

Material Properties

' Proof stress of bolt material -'σ_proof = ? {600}MPa 'Typical values: Grade 8.8 = 600 MPa, Grade 10.9 = 830 MPa, Grade 12.9 = 970 MPa '

Nut Factor (Torque Coefficient)

' Nut factor -'K_nut = ? {0.2} '

Typical K values:

K = 0.20 - Dry steel-on-steel (no lubrication)

K = 0.15 - Lubricated (oil or grease)

K = 0.10 - Anti-seize compound or MoS2

Ref: Bickford Table 7.1

Applied Clamping Force

' Required clamping force -'F_clamp = ? {100000}N "Calculations '

'Click to expand/collapse detailed calculations '

Proof Load

F_proof = σ_proof*A_s ' Proof load of bolt -'F_proof '

[Ref 1, Ch. 3]

Recommended Preload (75% of Proof)

F_i_75 = 0.75*F_proof ' Recommended preload at 75% of proof -'F_i_75 '

[Ref 2, Section 5.4]

Maximum Preload (90% of Proof)

F_i_90 = 0.90*F_proof ' Maximum preload at 90% of proof -'F_i_90 '

Required Tightening Torque

T_req = K_nut*d*F_clamp ' Required tightening torque -'T_req '

[Ref 1, Eq. 7.1: T = K x d x F]

Bolt Stress Under Clamping Force

σ_bolt = F_clamp/A_s|MPa ' Bolt tensile stress -'σ_bolt '

Utilization Against Proof Strength

util_proof = F_clamp/F_proof ' Utilization ratio (clamping force / proof load) -'util_proof '

"Results 'Proof Load: F_proof 'Recommended Preload (75% Proof): F_i_75 'Maximum Preload (90% Proof): F_i_90 'Required Tightening Torque: T_req 'Bolt Stress: σ_bolt 'Utilization: util_proof '

Assessment

#if util_proof ≤ 0.9 '

PASS - Bolt Preload Check

Utilization = 'util_proof' is less than or equal to 0.9

Clamping force of 'F_clamp' is within the proof capacity of 'F_proof'

#else if util_proof ≤ 1 '

WARNING - Bolt Preload Check

Utilization = 'util_proof' is between 0.9 and 1.0

Clamping force of 'F_clamp' exceeds 90% of proof load 'F_proof'

Consider reducing clamping force or using a higher grade bolt.

#else '

FAIL - Bolt Preload Check

Utilization = 'util_proof' is greater than 1.0

Clamping force of 'F_clamp' exceeds proof load of 'F_proof'

Increase bolt grade, increase bolt diameter, or reduce clamping force.

#end if "Conclusion 'The M'(d/1mm)' bolt with proof stress 'σ_proof' has a proof load of 'F_proof'. The recommended preload range is 'F_i_75' (75%) to 'F_i_90' (90%). For a clamping force of 'F_clamp' with nut factor K = 'K_nut', the required tightening torque is 'T_req'. The bolt stress is 'σ_bolt' giving a utilization of 'util_proof' against the proof load.

Bolt Torque and Preload Analysis

About This Calculator

Referenced Standards