The residual stresses adjacent to a long butt weld between two deck plates of a ship were found by x-rays. The average values of the lattice parameter, a, were a = 2.8619 parallel to the weld bead and a = 2.86106 perpendicular to the weld bead. For unstrained material, a = 2.8610. Find the values of the residual stresses parallel and perpendicular to the weld. Assume E = 30 × 106 psi, υ = 0.29, and that the stress normal to the plate is zero.