We substituted the measured values of the amplitude d and the half-wavelength w, obtained from Figure 6d, in Equation (3) and calculated the SCS formation angle 2α. The fold angle  was calculated from Equation (4). Figure 7b shows the relationship between  and L. Based on a linear approximation of the plot in Figure 7b,  and L are defined from the fold coefficient m by the following equation.
\(θ=mL\ [°]\)                   (5)
This linear relationship between linewidth and fold angle has been confirmed in our previous research.[28] Figure 7c shows that the coefficient of determination R2 values are close to 1 for all numbers of lines, and so the triangle approximation can be considered reasonable. Although even for the same linewidth, θ differs according to n. The value of m decreases as n increases. When the linewidth is low (L = 5 mm), as shown in Figure 7d, the error of the triangle approximation is small because the creases are far from each other. However, as the lines become thicker (L =15 mm), the effect of the approximation increases, and  decreases. As shown in Figure 7e, the more the number of lines, the closer the folds, and the shorter the straight-line parts. Consequently, if the distance between the lines is small, the change in the gradient of the straight-line parts caused by the linewidth is difficult to observe, and the observed value is smaller than the actual value. Thus, although some errors occur in this case, we can successfully relate the fold angle to the corrugated structure parameters by modeling.
 
Next, we derived the relationship between L and d and L and from the fold angle. The diagonal side i/2+L/2 of the right triangle shown in Figure 7a is defined from Equation (1) as follows.
\(\frac{i}{2}+\frac{L}{2}=\frac{105}{n}\)                (6)
Therefore, the amplitude d and half-wavelength w are obtained from Equations (4) and (5).