Compression programs

Released in 1993 to excellent sales (and a lawsuit for patent infringement), DOS 6.0 offered a number of new commands and configurable options. Another enhancement in DOS 6.0 was EMM386.EXE, which allowed the system to pool extended and expanded memory. DOS 6.0 has subsequently been revised a number of times—once (DOS 6.2 to 6.21) because of a court order. Microsoft was found to have violated Stac Electronics patent rights in the creation of the DoubleSpace utility for 6.0 and 6.1, and the only real difference between 6.2 and 6.21 is that DoubleSpace is removed. Never to be denied, Microsoft soon released DOS 6.22 with a disk compression program called DriveSpace. 

Figure 3.3 Fabrication process (a) measuring the resin (b) the mold (c) the vacuum chamber (d) the closed mold with clamps in the oven for curing (e) block specimens (left - cut specimen right - after compression programming)...

Figure 3.13 Schematic of cold-compression programming (steps 1 to 3), free shape recovery (step 4), and fully constrained stress recovery (step 5)...

One-Dimensional Stress-Controlled Compression Programming and Shape Recovery... 

In order to determine the thermomechancial behavior of the SMP and SMP based syntactic foam programmed using the classical method, the 1-D stress-controlled compression programming method (stress is constant) was conducted. Two stress levels were chosen 47 kPa and 263 kPa. The experimental setup shown in Figure 3.14 was used to conduct the stress-controlled programming. Additional weight was added as neeessary to reaeh the desired stress... 

The 3-D strcss-strain-time behaviors for the entire themomechanical cycle, which include the three-step cold-compression programming process and the one-step heating recovery, are shown in Figure 3.35, for both the 10% and 30% pre-strain levels. An extremely nonlinear, and time and temperature dependent constitutive behavior is revealed. In-depth understanding of... 

Cold-Compression Programming of Thermosetting SMP Based Syntactic Foam... 

The Hitachi S-3600N VP-Scanning Electron Microscope was used to examine the micro-stmcture change due to programming (see Figure 3.37). From Figure 3.37 (b), some of the microballoons have been cmshed after cold-compression programming by 30% pre-strain, which contributed to the irreversible strain after free shape recovery. 

Figure 3.37 SEM observation of (a) a pristine specimen and (b) a specimen after 30% cold-compression programming. Source [45] Reproduced with permission from ASME...

Because Figure 3.44 is a stress-strain-temperature plot, step 2 (30 minutes of holding or relaxation) during cold-compression programming cannot be visualized. To have a better understanding of the stress-strain evolution with time, a typical thermomechanical cycle in terms of stress-strain-time for the four groups of specimens is shown in Figure 3.45 (a) to (d), respectively. In order to have both tension and compression direction in the same quadrant, the compression stress and compression strain are also treated as positive. 

Figure 3.49 Schematic showing the shape memory mechanism involved in the two-stage biaxial programming and recovery. Note the contribution of the compression programming to the further segmental alignment along the tension direction. Source [59] Reproduced with permission from the American Society of Civil Engineers...

The veloeity gradient is essential in analyzing path dependent materials such as plastic deformation of cold-compression programmed SMP. It is also useful in determining the energetically conjugate stress and strain, as will be demonstrated in the section on stress definition. 

Constitutive Modeling of Cold-Compression Programmed Thermosetting SMP... 

In continuum mechanics, constitutive modeling of materials follows certain steps, including deformation response, stress response, as well as other particular steps based on materials studied, such as structural relaxation for polymers and a plastic flow mle, and a hardening rule for materials with plastic deformation. In the following, we will present the deformation response, structural relaxation, stress response, and flow rule for the thermosetting SMP programmed by cold-compression programming. 

Other parameters such as the glass transition temperature, programming temperamre, relaxation time during cold-compression programming, and glassy shear modulus can be found from the test results presented in Chapter 3. The determined model parameters for the polystyrene based thermosetting SMP arc summarized in Table 4.2. 

---