Work recovery

For a long time, the fiber industry had been aware of PTT having desirable properties for fiber applications. In a 1971 patent [3], Fiber Industries, Inc. found PTT fiber to have a lower modulus, better bending and work recoveries than PET, and was therefore more suitable than PET for making fiberfill and carpets. Ward et al. [4] compared the mechanical properties of the three polyester fibers, and found PTT indeed had a better tensile elastic recovery and a lower modulus than both PET and PBT. These two properties are very desirable and are valued... 

Predictability provides an individual with the opportunity to plan, whether for work, recovery requirements, or home activities. When possible, schedule stability provides more consistent circadian cues and the opportunity to create individual patterns and habits that minimize the physiological disruptions. Modem work demands, especially 24/7 requirements, are often associated with overtime, which may be elective or on occasions required. Extending work has the potential to increase the continuous hours awake, be affected by circadian factors by working through a window of circadian low, and contribute to both acute sleep loss and a cumulative sleep debt. The timing and amount of overtime and whether it is elective or required, can all affect the level of physiological disruption. 

The load schedule performance is assessed in terms of how well temperatures on the hot side of the combined plant are maintained constant. Also of interest are the pressures on the helium side for assessment of creep under pressure load. The pressures in the HTSE plant were maintained at 5 MPa over the load schedule from the point downstream of where the reactant water is fed in up to the point where the products enter the pressure-work recovery turbine. 

Physical recovery tends to occur earlier than psychological or work recovery. Full recovery usually takes several years, and about two-thirds of patients do not have major limitations by 5 years. 

Figure 7. Effect of temperature on work recovery of PET fibers...

Tensile work recovery can be considered a dynamic-loss modulus obtained at very low cycling rates. A fiber Is stressed to 3 g/den. and Immediately allowed to recover. The work recovered exhibits a marked reduction at the glass transition temperature (Figure 7). 

Russek SL, Knopf JA, Taylor DM. Oxygen production by ion-transport membranes with non-permeate work recovery. U.S. Patent 5,753,007, 19 May 1998. 

The tensile strain recovery and the work recovery % are also calculated. The procedure for crimped specimens is much the same, except that the test specimen is first pretensioned to take out the crimp and the extension shown on the recording chart eliminated by rezeroing the recorder. The location of the cross-head is locked in the memory at this point, so that on recovery the cross-head does not reenter the crimp range. 

When a specimen is stretched less than the breaking elongation and allowed to relax by removal of the strain according to a predetermined procedure. ( = tensile recovery curve, work recovery curve, and strain recovery curve.)... 

Recovery time, including regularly scheduled work breaks, usually provided in jobs where heavy physical work or exposure to environmental extremes occurs. Rest allowances are built into the job standard so that productivity ratings recognize the need for additional recovery time in these jobs. See also Work Recovery Cycles. 

Work recovery The ratio of recoverable work to the total work required to strain a fiber a specified amount under a given program of strain rate. 

Typical Conditions. Titanium-nickel is most commonly used in a cold worked and partially annealed condition. This partial armeal does not recrystallize the material, but does bring about the onset of recovery processes. The extent of the postcold worked recovery depends on many aspects of the application, such as the desired stiffiiess, fatigue life, ductility, recovery stress, etc. Fully annealed conditions are used almost exclusively when a maximum Mg is needed. Although the cold worked condition does not transform and does not exhibit shape memory, it is highly elastic and has been considered for many applications (Ref 6). 

In addition to dimensional recoveiy, work recoveiy often is studied for tensile deformation. While stretching a fiber, the total work done is either stored in chemical bonds or is lost, typically in the form of heat. The work stored in the chemical bonds is recoverable, but the work lost is not. In Figure 15.23, the area under the stretch curve is the total work per unit volume done during stretching. The area under the recovery curve is the work per unit volume returned during recovery. Work recovery can then be defined as ... 

Table 15.4 shows the work recoveiy of some fibers under different strains and in different humidities. Inorganic fibers, such as glass, have very high work recovery at a low strain of 1%. However, they break at moderate and high strains, and no work recoveiy can be measured. The work recovery of polymer fibers is lower than their elastic (strain) recoveiy due to the non-linear stress-strain behavior. In addition, the work recovery also is affected by both strain and humidify. 

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