Cushion curves

The parameters C7j and G of the cushion curve can be calculated from the energy density function [/(c7 ,), using Equations (13) and (14). These equations only contain the ratio t/h of the foam dimensions, so the resulting cushion curves can be labelled with the reduced foam thickness = t/h. 

GENERATION OF CUSHION CURVES FROM ONE SHOCK PULSE... 

Cellular Polymers II. Conference proceedings. Edinburgh, 23-25th March 1993, paper 21. 6124 PREDICTION OF PACKAGING CUSHION CURVES AND HELMET LINER RESPONSES... 

A method for the prediction of cushion curves for polymer packaging foams from a single impact stress-strain curve is proposed. The method is valid if there is a master curve for the increasing stress part of the stress-strain curve. For closed-cell polymer foams that deform by yielding... 

Details are given of the change in cell structure of a closecell foam due to multiple impacts and the range of application of cushion curves as they relate to reusable packaging. Cushion curves and stress-strain curves for up to 15 compressions were generated for three different moulded closed-cell PE foams. 

The information about cushion performance is most often transmitted in the form of characteristic cushion curves that relate the average deceleration to the static loading as a function of drop height, cushion thickness, temperature, and number of impacts (see Fig. 13.2). Computer programs that contain mathematical models of cushion curves for various types of foams, sometimes along with cost information, are also available. Relatively simple calculations then permit selection of an appropriate cushion thickness and load-bearing area that can reasonably be expected to provide adequate protection for a given product. 

For the cushion with a characteristic cushion curve shown in Fig. 13.2, caicuiate the load-bearing area that will provide adequate protection for a product measuring 20 cm by 30 cm, with a mass of 10 kg, and with a fragility of 50 G. The maximum expected drop height for the product is 1 m. 

Figure 13.2 A typical cushion curve for a hypothetical packaging foam, for the second to fifth drops from 1 m, for 2.5-cm thick, 5.0-cm thick, and 7.5-cm thick foam...

What is the minimum fragility required for a product to be sufficiently protected if it is cushioned with 1-in foam with cushion curves as shown in Fig. 13.2, and if the static loading is 0.5 What if a larger cushion is provided, so the static loading decreases to 0.4 A smaller cushion, increasing the static loading to 0.8 ... 

Three-layer dual-chamber cushion, curved middle layer... 

The estimation of cushion curves from a few impact tests. 

Cushion curves are used in the industry to select the most appropriate foams and geometry for a given packaging application. In these diagrams, the maximum deceleration during the impact is presented as a fimction of the static stress used in the experiment (Fig. 11). Loveridge and Mills [78] proposed a method for the prediction of cushion curves from a single-impact... 

Fig. 11 Cushion curves for a LDPE foam 45 kg/m and 50 mm thickness. The deceleration values are measured in the first impact and for different drop heights...

Compressive Behavior. The most kiformative data ki characterising the compressive behavior of a flexible foam are derived from the entire load-deflection curve of 0—75% deflection and its return to 0% deflection at the speed experienced ki the anticipated appHcation. Various methods have been reported (3,161,169—172) for relating the properties of flexible foams to desked behavior ki comfort cushioning. Other methods to characterize package cushioning have been reported. The most important variables affecting compressive behavior are polymer composition, density, and cell stmcture and size. 

The weight of the particles builds up with time and is proportional to 1/d. If we assume spherical particles, then we can convert the above curve to particle diameter from Stokes Law. Although we have added the pcurticle suspension to a "water cushion" as shown above, it might not seem that the settling of the particles would strictly adhere to Stokes Law, which assumes the terminal velocity to be constant. 

Within the experimental error, the raw data points of cushioned and initial 10% fines curves of South Blackwater coal dropped on conveyor surface differ from model data points by 3% and the raw data points of initial 30% fines curve differ from model data points by 1% on 30 m total drops (six drops at 5 m) shown in Fig. 18. 

Raw data points of cushioned and initial 10% fines curve of South Blackwater coal dropped on coal surface differ... 

Maintenance of Proper Antimony Concentration. Close monitoring of the antimony concentration on the catalyst will assure that maximum benefits are derived from a metals passivation program. The antimony-to-nickel ratio on the equilibrium catalyst has been correlated with hydrogen production in commercial operations (Figure 5), The non-linear shape of the hydrogen production curve has been confirmed in pilot plant tests (Figure 1), The recommended antimony concentration corresponds to a point beyond the breakpoint of the curve, A "cushion" is desired to allow fluctuations in the system without major increases in the yields of hydrogen and coke. 

One of the most important properties of flexible urethane foams is cushioning. Figure 6 shows a comparison of hysteresis curves among polyester-, polyether- and HR-foams, respectively. 

Fig. 5 Surface-plasmon resonance curves, i.e., reflectivity-vs-incident angle scans of the bare substrate, a Ag coated glass slide with a thin SiC>2 layer evaporated on top (A), after the self-assembly of a reactive monochlorosilane derivative (cf. Fig. 4a) (B), after the adsorption (from solution), covalent binding, and soxhlet extraction of the polymer cushion (C), and after the deposition of a model lipid monolayer (a layer of reactive ester derivatives of a fatty acid) (D)...

SIT ISIT. Array is flat. Curved formats are not available. Electrostatic focusing causes pin-cushion distortion and a loss of geometric resolution at the detector s edges. 

---