Creating a 2d load envelope with python

Acting loads on a part or an aircraft component could be huge numbers. Therefore in initaial sizing process the load cases with low magnitudes would not size any parts. In order to detect these low load cases 2d load envelopes help to reduce load cases.

In pyhton ConvexHull method helps you in a way below to detect critical loads in envelope.

import pandas as pd

import matplotlib.pyplot as plt

from scipy.spatial import ConvexHull

from tkinter import Tk, filedialog

# === Use file dialog to select CSV file ===

Tk().withdraw()  # Hide the root Tkinter window

file_path = filedialog.askopenfilename(title="Select your CSV file", filetypes=[("CSV files", "*.csv")])

# === Load CSV ===

df = pd.read_csv(file_path)

# === Helper function to plot and get convex hull points ===

def plot_and_get_boundary(x_col, y_col):

    points = df[[x_col, y_col]].values

    # Convex Hull

    hull = ConvexHull(points)

    boundary_indices = hull.vertices

    boundary_points = df.iloc[boundary_indices][['Case ID', x_col, y_col]]

    # Plot

    plt.figure()

    plt.scatter(df[x_col], df[y_col], label='All Points', color='blue')

    plt.plot(points[hull.vertices, 0], points[hull.vertices, 1], 'r--', lw=2, label='Convex Hull')

    plt.fill(points[hull.vertices, 0], points[hull.vertices, 1], 'r', alpha=0.1)

    plt.scatter(boundary_points[x_col], boundary_points[y_col], color='red', label='Boundary Points')

    plt.xlabel(x_col)

    plt.ylabel(y_col)

    plt.title(f'{x_col} vs {y_col} with Convex Hull')

    plt.legend()

    plt.grid(True)

    plt.show()

    return boundary_points

# === Plot 1: Nx vs Ny ===

boundary_nx_ny = plot_and_get_boundary('Nx', 'Ny')

print("\nBoundary Points (Nx vs Ny):")

print(boundary_nx_ny)

# === Plot 2: Nx vs Nz ===

boundary_nx_nz = plot_and_get_boundary('Nx', 'Nz')

print("\nBoundary Points (Nx vs Nz):")

print(boundary_nx_nz)

# === Plot 3: Ny vs Nz ===

boundary_ny_nz = plot_and_get_boundary('Ny', 'Nz')

print("\nBoundary Points (Ny vs Nz):")

print(boundary_ny_nz)