## 3 Results and Discussion  
In the 1 st ALT, we found the failure time of the following stress levela--0.088 kN (9 kgf), 0.117 kN (12 kgf), and 0.137 kN (14 kgf). For 0.088 kN (9 kgf), the cover of the drawer fractured at 14,000 cycles, 19,000 cycles, and 21,000 cycles. For 0.117 kN (12 kgf), it fractured at 3800 cycles and 4800 cycles. For 0.137 kN (14 kgf), it fractured at 550 cycles,  
Figure 8: ALT apparatus and duty cycles of repeated food load F. (**a**) Apparatus; (**b**) Controller; (**c**) Duty cycles of repeated food load F.  
650 cycles, and 800 cycles. To investigate the fracture surfaces, they were observed by SEM. We found the voids produced because of falling out particles (Figure 9). Finally, we determined the stress level as 0.117 kN (12 kgf) for the parametric ALT because it had a relatively acceptable data--linearity, contrasted with the other stress level. It also can be seen that increasing the repeated food weight has the effect of shifting the left of failure time as stress range (or intensity range \(\Delta\)\(K\)) increased and the crack growth rate moved up, but it did not influence the gradient of the growth rate curve and shape parameter, \(\beta\) (Figure 10). Initially, when 1.17 kN (12 kgf), as the accelerated weight in drawer was loaded, the left/right rollers on the rail were taken away and the center support rail was deformed so that the drawer system no longer slid. Because of insufficient strength due to design flaws, the draw system was modified by extending the roller support to 7 mm (C2) on the guide rail, as well as adding up strengthened ribs on the center support rail (C1) (Figure 11 and Table 3). Figure 10: Result of the step-stress life test on a Weibull plot. Figure 9: SEM micrographs of fracture surfaces. When carefully observing the returned drawers from the marketplace and the first ALT, failure locations were found to be in the junction regions of the drawer cover and its body structure, as a consequence of high repeated stress and expected high da/dN. Figure 10 also provides a Weibull plot of the ALT results, compared to the data from the market. As two patterns had similar slopes on its plot, it was recognized that each loading of the first ALT and the market was similar for the operation conditions. For the shape parameter, \(\beta\), the final shape parameter from the chart was affirmed to be 4.2 (Figure 10), compared with the estimated value--2.0. Based on both test consequences and the Weibull plot, the ALT was effective because it identified the design flaws that were accountable for the field failures. Based on the pictures from the ALT and the field and Weibull plot, the tests helped in identifying the problems in the design responsible for market failures and the poor product lifetime. Due to design defects such as no corners in the high stress areas of intersection (A), the repeated loading of the drawers in conjunction with these structural defects may have been fracturing the drawer cover. These design defects can be altered by: (1) making thicker reinforced ribs, Rib1, C3, from T2.0 mm to T3.0 mm; (2) applying the fillets, Filet1, C4, from R0.0 mm to R1.0 mm (Figure 12). Figure 11: Design issues of drawer system in (static) loading. \begin{table}
\begin{tabular}{c|c} \hline
**Center Support** & **Rail** \\ \hline
**Two additional reinforced ribs (C1)** & **T  mm** \\ \hline \end{tabular}
\end{table} 
Table 3: Altered designs of center support and rail in initial loading. Stress analysis, which may be integrated with fatigue analysis and parametric ALT, was performed by utilizing a finite element analysis (FEA). As the drawer system was attached against the wall, the uncomplicated food loads, as seen in Figure 7, were exerted. Using materials and processing conditions similar to those of the drawer, the constitutive properties of the materials such as polypropylene (drawer structure) were decided. For the old and new designs, we individually evaluated the maximum stresses.