Ramp loading

The ramp of pressure to about 3 GPa observed in shock-loaded fused quartz has been used very effectively in acceleration-pulse loading studies of viscoelastic responses of polymers by Schuler and co-workers. The loading rates obtained at various thicknesses of fused quartz have been accurately characterized and data are summarized in Fig. 3.6. At higher peak pressures there are no precise standard materials to produce ramp loadings, but materials such as the ceramic pyroceram have been effectively employed. (See the description of the piezoelectric polymer in Chap. 5.)... 

In a different set of tests, medium-speed thrust washer sliding was done on Ti-6A1-4V. ty pe 6061-T6 Al, X-750, type 316 stainless steel, and X-750 samples coated with either a friable or a bonded commercial M0S2 coating. Tests were performed using ramped rotation speed, to assess friction as a function of sliding speed ramped load, to assess friction as a function of load or different atmospheres, to assess the effect of ambient gas on friction. Variable tests were ramped up and down, often more than once, to ascertain the reproducibility of the data. Sliding was stopped during... 

Notice that the TCI controller does not hold the T35 temperamre at 101 °C during the period when the feed is ramping down or up. A PI controller will produce offset when subjected to a ramp disturbance. This offset occurs in all control structures during the ramp load disturbances. This offset problem could be reduced by using a lag-compensated PI controller for TCI. 

Ramp load increase and decrease of 3% per second over the load rang of 70% to 100%... 

The chemical and volume control system provides a means to add and remove mass from the reactor coolant system, as required, to maintain the programmed inventory during normal plant operations. Operations that are accommodated include start-up, shutdown, step load changes, and ramp load changes. 

The eapability to aceept ramp load changes at 5 -percent power per minute while operating in the range of 15-pereent to 100-percent of full power without reactor trip or steam dump system actuation, subject to core power distribution limits. 

Figure 8. Simulation of a ramp loading cycle of viscoelastic spheres in contact (k = 0.1), showing hystereras loops for varying values of rate parameter A..

Show that the effect of the initial ramp loading in a realistic relaxation test as given in Fig. 5.5 d of a material that can be represented by a Maxwell fluid is negligible if the time of the ramp load to is small compared to the relaxation time, x. 

R. M. Guedes, A. T. Marques, and A. Cardon. Analytical and experimental evaluation of nonlinear viscoelastic-viscoplastic composite laminates under creep, creep-recovery, relaxation and ramp loading. Mechanics Time-Dependent Materials 2 (2), 113-128 (1998). 

---