## 3 Cushion Compression and Offset Test Based on Short-Circuit Force Simulation
### Analysis of Three-Point Bending Test
Figure 8: Example of cushion block offset structures. Figure 10: Graphical determination of non-proportional bending stress. Figure 9: Schematic diagram of three-point bending test. Through point C, make CA parallel to the elastic straight line segment to intersect the curve at point A. The force corresponding to point A is the measured prescribed non-proportional bending force \(F_{pd}\). \(b\) is the width of the wire, and the prescribed non-proportional bending stress \(\sigma_{pd}\) of the wire can be calculated from Equation (27). \[\sigma_{pd}=\frac{3F_{pd}L}{2 bh^{2}} \tag{27}\]  
Apply a pre-bending force of less than 10% \(\sigma_{pd0,01}\) to the wire and record the force and deflection at the midpoint of the span. Then, continue loading the applied force until it reaches 50% \(\sigma_{pd0,01}\). Record the incremental bending force and deflection at this point. Finally, calculate the bending modulus of elasticity using Equation (28). Figure 6:0  
where \(\Delta F\) denotes the bending force increment and \(\Delta f\) denotes the deflection increment. Firstly, the effect of unbalanced height of cushion blocks is studied and unbalanced support structures are set up at both ends of the wire. Set up the wire with two, three, four, and five pieces of cushion blocks support at one end and five pieces of cushion blocks support at the other end with a span of 17 cm. A total of five tests were carried out in each case and the average of the measurements was taken. As can be seen from the Figure 11, there is a clear correlation between the cushion block unbalanced height and the force-deflection curve. With the increase in the unbalanced height of the neighboring cushion blocks, the bending force of the wire samples all show a decreasing trend, but the magnitude is not large. When the deflection reaches 5.8 mm, the bending force is 1.14 kN, 1.19 kN, 1.25 kN, and 1.25 kN in order when the cushion block unbalanced heights at both ends of the samples are 6, 4, 2, and 0 mm. Similarly, the force-deflection curves of wires under different cushion block offsets are recorded, as shown in Figure 12, and, finally, the bending modulus of elasticity of multiple parallel-wound wires under different cushion block unbalanced heights and different cushion block offsets are obtained by the bending modulus of elasticity calculation method of Equation (26); the results are shown in Tables 3 and 4. Figure 6:1 Force–deflection curves under different unbalanced heights of cushion blocks. Based on the data in the table, it can be observed that, as the height of adjacent cushion block unbalances increases, the bending elastic modulus of the wire decreases. When the cushion block unbalanced height increases from 0 mm to 2 mm or from 4 mm to 6 mm, the average decrease in the bending elastic modulus of the samples is approximately 6.37 MPa. When the cushion block unbalanced height increases from 2 mm to 4 mm, the change in the bending elastic modulus of the samples is 25.00 MPa, representing a decrease of 29.46%. Under the same offset angle, the wire's bending elastic modulus is lowest for the cushion block's crosswise offset structure, indicating the poorest mechanical performance. The cushion block's same-direction offset structure follows. For both 30\({}^{\circ}\) and 45\({}^{\circ}\) offset angles, the bending elastic modulus of the wire under these three offset structures decreases as the offset angle increases, indicating deteriorating mechanical performance. When the cushion block offset angle is 45\({}^{\circ}\), the bending elastic modulus of the wire decreases by 54.7% and 79.3% for same-direction and crosswise offsets, respectively. This may be attributed to the reduced contact area between the cushion blocks and the winding due to cushion block offset, leading to weakened bending resistance.