A plastic component of a polycarbonate household electrical appliance was tested. A Young’s modulus of 2650 MPa, a Poisson’s ratio of 0.37 and a tensile strength of 80 MPa were considered for this material.
The following testing conditions were adopted for the automatic measurement system:
- Maximum depth: 2mm
- Drilling step: 0.05 mm
- Number of drilling steps: 40
- Drilling step trend: linear
- Feed rate: 0.1 mm/min
- Delay time: 90 sec.
- Strain gauge rosette: HBM K-RY61-1.5/120R-3 prewired, 3-wire connection
- HBM Spider 8.30 strain gauge amplifier
Three measuring points were set up. The positions are shown in figure 9 and two drilling stages can be seen in figure 10.
By way of example, figure 11 shows the results obtained for measurement of residual stresses at measuring point 1. The graphs show the trends of the strains, the principal stresses and the alpha angle, which were measured in accordance with the provisions of standard ASTM E837. Similar results were obtained at the other measuring points but are not provided solely for the sake of brevity.
|Figure 11a. Strains versus||Figure 11b. Uniformity test (ASTM E837-08)|
|Figure 11c. Principal stresses and ideal stress versus||Figure 11d. Alpha angle versus depth.|