Bolt Calculator

Bolt Calculator (bolts)

Purpose

Analyze threaded fasteners including power screw efficiency, bolt pattern stiffness, and VDI 2230 single-bolt preloaded joint worksheet. Computes tensile, shear, bearing utilization and preload margin for mechanical joints.

Physics & theory

Bolted joints clamp parts together with initial preload $F_i$ from torque $T=K{F}_{i}d$, where $K$ is nut factor. External tensile load $F_e$ shares between bolt and members by stiffness: bolt load increment $\Delta F_b=F_e{k}_b/(k_b+k_m)$. Separation occurs when preload is lost.

Shear may be carried by friction (when clamped) or bolt shank/threads in bearing. Combined tension and shear uses interaction criteria per AISC J3 or VDI 2230. Power screws convert torque to axial force with efficiency $\eta =\tan \lambda /\tan (\lambda +\varphi )$ for square/Acme threads.

Connections transfer load through bearing, shear, tension, and friction paths depending on joint configuration. Preload in bolted joints reduces joint separation and can allow friction to carry shear; without adequate preload, bolts carry full shear in bearing against hole walls.

FEM-based bolt analysis resolves member and bolt stiffness for load sharing; VDI 2230 provides a systematic worksheet for high-fidelity preloaded joints including embedding loss and tightening scatter.

Governing equations

Numerical method

Dual paths: (1) Power screw and pattern analysis via FEA stiffness (femSolver); (2) VDI 2230 worksheet for high-fidelity single-bolt joints with embedding, thermal, and tightening scatter. Validators enforce thread and geometry consistency.

Inputs

Outputs

• Bolt and member load sharing, tensile/shear/bearing utilization, preload safety margin, torque recommendation
• VDI 2230 assembly preload range.

Design codes & checks

• Indicative: Tensile, shear, bearing utilization
• US: AISC 360-22 Chapter J3
• EU: EN 1993-1-8, VDI 2230 Part 1

Assumptions & limitations

• Linear elastic joint behavior; no gasket creep long-term model unless VDI embedding used.
• VDI 2230 is single-bolt centric; patterns use simplified stiffness superposition.
• Power screw FEA validated against Shigley benchmarks.
• Does not replace licensed pressure vessel or nuclear QA bolt procedures.

References

1. VDI 2230 Part 1:2015. Systematic calculation of highly stressed bolted joints.
2. Shigley, J. E., & Budynas, R. G. Mechanical Engineering Design, 11th ed., Ch. 8.
3. AISC. Specification for Structural Steel Buildings (ANSI/AISC 360-22), Chapter J3.
4. EN 1993-1-8:2005. Design of joints.
5. PhyCalcPro verification benchmarks in src/data/verification/ where available for this module.
6. Beer, F. P., et al. Mechanics of Materials, 8th ed. McGraw-Hill — foundational stress and deformation theory.