bolt-pattern-elastic-method 1.0.1

Bolt pattern force distribution analysis

Implements the methodology from NASA RP-1228.

Given a bolt pattern (positions + areas) and applied loads at arbitrary locations, this module computes the axial and shear force on each bolt.

Outputs verified against the calulator here: https://mechanicalc.com/reference/bolt-pattern-force-distribution 3d plotting currently does not display the moments, but they are handled correctly for calculations.

Example usage:

if name == "main": import os import bolt_pattern_elastic_method

HERE = os.path.dirname(os.path.abspath(__file__))

positions_1 = [(-3.5, 15), (3.5, 15), (-3.5, -15), (3.5, -15)
               , (10, -15), (18.82, -12.14), (24.27, -4.635)
               , (24.27, 4.635), (18.82, 12.14), (10, 15)
               , (-10, 15), (-18.82, 12.14), (-24.27, 4.635)
               , (-24.27, -4.635), (-18.82, -12.14), (-10, -15)] #[x,y]

# ------------------------------------------------------------------
# Example 1: 4-bolt rectangular pattern, in-plane eccentric shear
# A 1000 N force applied in X at (y=5) – creates torsion about Z
# ------------------------------------------------------------------
print("\nEXAMPLE 1 – General 3-D loading")
save_path="bolt_pattern_ex1.png"
analysis_1 = BoltPatternAnalysis(
    bolts=[Bolt(x, y) for (x, y) in positions_1],
    loads=[AppliedLoad(Fx=1500.0, Fy=500.0, Fz=5000.0, z=15.0),
           AppliedLoad(Mz=1000.0)],
)
results_1 = analysis_1.solve()
print_results(results_1, analysis_1)
plot_bolt_pattern_3d(
    analysis_1, results_1,
    title="Example 1 - General 3-D loading",
    show=False,
    save_path=os.path.join(HERE, "save_path"),
)
print(f"  → saved {save_path}")


# ------------------------------------------------------------------
# Example 2: general 3-D loading using the convenience function
# ------------------------------------------------------------------
print("\nEXAMPLE 2 - General 3-D loading (convenience function)")
analysis_2 = BoltPatternAnalysis(
    bolts=[Bolt(x, y, label=lbl) for (x, y), lbl in zip(
        [(-3, -3), (3, -3), (3, 3), (-3, 3)], ["TL", "TR", "BR", "BL"]
    )],
    loads=[AppliedLoad(Fx=200, Fy=-150, Fz=300,
                       Mx=500, My=-400, Mz=1000,
                       x=1.0, y=2.0, z=50.0)],
)
results_2 = analysis_2.solve()
print_results(results_2, analysis_2)
plot_bolt_pattern_3d(
    analysis_2, results_2,
    title="Example 2 - General 3-D Loading",
    show=False,
    save_path=os.path.join(HERE, "bolt_pattern_ex2.png"),
)
print("  → saved bolt_pattern_ex2.png")
# ------------------------------------------------------------------
# Example 2: general 3-D loading using the convenience function
# ------------------------------------------------------------------



import os
import bolt_pattern_elastic_method as bp
HERE = os.path.dirname(os.path.abspath(__file__))
save_path="bolt_pattern_ex1.png"

r_y_c, r_x_c = (3)/2, (4)/2   # bolt cardinal spacing from centroid of bolt pattern, in, as viewed from a given axis.
    Fx=F_xz_c
Fy=100
Fz=42
Mx=500
My=37
Mz=0

positions_1 = [(r_x_c, r_y_c), (r_x_c, -r_y_c), (-r_x_c, r_y_c), (-r_x_c, -r_y_c)]

analysis_1 = bp.BoltPatternAnalysis(
    bolts=[bp.Bolt(x, y) for (x, y) in positions_1],
    loads=[bp.AppliedLoad(Fx=Fx, Fy=Fy, Fz=Fz, Mx=Mx, My=My, Mz=Mz, x=0, y=0, z=0)],
    )
results_1 = analysis_1.solve()
#bp.print_results(results_1, analysis_1)
max_tension  = max(results_1, key=lambda r: r.Fz_total)
min_tension  = min(results_1, key=lambda r: r.Fz_total)
max_shear    = max(results_1, key=lambda r: r.F_shear)
min_shear    = min(results_1, key=lambda r: r.F_shear)
print(f"    Max tension (lbf):  {max_tension.bolt.label:>6}  Fz = {max_tension.Fz_total:+.2f}")
print(f"    Min tension (lbf):  {min_tension.bolt.label:>6}  Fz = {min_tension.Fz_total:+.2f}")
print(f"    Max shear (lbf):    {max_shear.bolt.label:>6}  Fs = {max_shear.F_shear:.2f}")
print(f"    Min shear (lbf):    {min_shear.bolt.label:>6}  Fs = {min_shear.F_shear:.2f}")