Other Worst-case Stresses

Having validated our choice of inductor, we can look a little more closely at the important issue of how the wide-input range impacts the other key parameters and stresses in our proposed converter. This also helps in correctly selecting the other power components. 

Note If for the boost, the input range of the given application does not include the D = 0.5 point, we need to identify which voltage end of the range provides a duty cycle closest to D = 0.5. And we need to then do the worst-case core loss calculation at that end (if so desired). 

Generally, the core loss term, being such a small component of the total loss, is of no great concern to us, so we won t even bother to do a numerical calculation here. But the general procedure to handle such cases will become apparent as we study the other worst-case loss terms of the converter below. 

But first let us now start annotating (or subscripting) some of the terms derived so far, just for gaining clarity in the discussion to follow. We should be clear that 

We need to keep these distinctions in mind, otherwise the following discussion can become confusing to no end  

---

The worst-case scenario related to a single tank can be mitigated by using a number of smaller tanks to store a given amount of liquid. This approach, however, increases the likelihood of a smaller leak by multiplying the number of accessories that accompany the tanks (GEST 72/10). On the other side of the question, the maximum size of a tank depends on capabilities in shop fabrication, stress relief, and transportation to the site. 

The valve s stress history and other relevant terms (temperature, volume, material properties, element number, etc.) were subsequently read into CARES/Li/e. Figure 9 shows the predicted failure probability as a function of the number of cycles for various scenarios. None of the tested valves failed, 8 of the 15 of which were tested to 1000 hours (which corresponds to approximately 1.1 x 10 cycles). Thus the failure rate of the tested valves was less than 1 out of 8 at 1000 hours of operation. From Figure 9 it can be seen that in fast-fracture (at one cycle with no SCG) about 5 out of 100,000 valves are predicted to fail from the loading. With SCG and the power law about 20 out of 100,000 valves fail after 1000 hours operation. If we conservatively assume that a worst-case load (time step 6) is applied over the whole engine cycle (static loading), then about 40 out of 100,000 valves fail after 1000 hours. Using the combined Walker power law with the hypothetical parameters from Table 1 this rate increases to 70 out of 100,000 valves at 1000 hours. All of these rates were well... 

To what extent the stress is carried by the fibers depends on the grip the matrix has on the reinforcement. In the worst case, due to a total lack of adhesion between the fiber and the matrix, there is no grip at all. The matrix solely then governs the properties, and consequently the composite shows a poor mechanical performance. The perfect grip , on the other hand, results from infinitely long fibers with an excellent adhesion to the matrix. In this ideal case the strain (a) in the fibers is equal to that of the matrix (iso-strain conditions). Knowing that for a material with a linear elastic behavior a = Es, wherein E is the stiffness or Young s modulus, we can derive Eq. (3) from Eq. (2). 

Children and family social work services in the UK are chronically understaffed the remaining staff are often demotivated and stressed by the volume of work, and the strain of working with difficult, frequently highly conflictual and chronic child protection cases. Many of the drug workers and health visitors expressed their sense of social work as a service in crisis, with extremely limited capacity to respond to anything other than the worst child protection cases, triggered usually by incidents rather than the chronic accumulation of problems ... 

---