stresses_strains.py

import numpy as np
from Q_and_Qbar import transform_Q

# Function returns the stress in primary material directions as a column vector
# Transformation matrix T1 inverse (primary strain --> principal strain)


def transform_T1(principal_stress, ply_angle):
    m = np.cos(ply_angle)
    n = np.sin(ply_angle)
    T1 = [[m**2, n**2, 2*m*n], [n**2, m**2, -2*m*n], [-m*n, m*n, m**2-n**2]]
    primary_stress = np.dot(T1, principal_stress)

    return primary_stress

# Calculate 2 values of strain and stress for every height element, excluding
# the first and last heights which only result in 1 value of strain and stress because they're on the surface
# There's an opportunity to remove the inner loop but when I try to make height a column vector the dimensions are mismatched


def global_ply(Q0, stack, estrain_glob, kstrain_glob, height):
    plystrain_glob = np.zeros(shape=(3, 2*len(height)-2))
    plystress_glob = np.zeros(shape=(3, 2*len(height)-2))

    for k in range(len(height)-1):
        for i in range(5):
            plystrain_glob[i, 2*k] = estrain_glob[i] + \
                height[np.ceil(k/2)]*kstrain_glob[i]
            # Shirely pls check this trick here works on some test data kk thx
        Qbar = transform_Q(Q0, stack[k])
        plystress_glob[:, 2*k] = np.dot(Qbar, plystrain_glob[:, 2*k])
        Qbar = transform_Q(Q0, stack[k])
        plystress_glob[:, 2*k+1] = np.dot(Qbar, plystrain_glob[:, 2*k+1])

    return (plystrain_glob, plystress_glob)


def local_ply(plystrain_glob, plystress_glob, height, stack):
    plystrain_loc = np.zeros(shape=(3, 2*len(height)-2))
    plystress_loc = np.zeros(shape=(3, 2*len(height)-2))

    for k in range(len(height)-1):
        plystrain_loc[:, 2*k] = transform_T1(plystrain_glob[:, 2*k], stack[k])
        plystrain_loc[:, 2*k +
                      1] = transform_T1(plystrain_glob[:, 2*k+1], stack[k])
        plystress_loc[:, 2*k] = transform_T1(plystress_glob[:, 2*k], stack[k])
        plystress_loc[:, 2*k +
                      1] = transform_T1(plystress_glob[:, 2*k+1], stack[k])

    return (plystrain_loc, plystress_loc)