Load/deflection characteristics

There is also growing interest in multi-phase systems in which hard phase materials are dispersed in softer polyether diols. Such hard phase materials include polyureas, rigid polyurethanes and urea melamine formaldehyde condensates. Some of these materials yield high-resilience foams with load deflection characteristics claimed to be more satisfactory for cushioning as well as in some cases improving heat resistance and flame retardancy. 

The equivalence of K and (7, which strictly holds for elastic materials with linear load-deflection characteristics, is referred to as linear-elastic fracture mechanics (LEFM). Subsequently this basic concept has been modified to describe also the behavior of ductile materials. For instance. Wells [3] considered the plastic strain at the crack tip as the crack... 

The piles and pile groups must have acceptable load deflection characteristics in all modes for the anticipated loading conditions. 

In addition to the standard consideration of axial and lateral foundation capacity, load-deflection characteristics, settlement, slope stability, and earth pressures, there are a number of subsurface conditions that can affect foundation design and performance. Those conditions include the following ... 

We have now looked at the more common types of single-axis load-deflection characteristics possible with elastomeric products, as well as various methods to change the stiffness in one direction while maintaining an initial stiffness in a plane that is 90 degrees from the reference plane. The angular considerations in different directions can now yield an unlimited number of design-configuration options. 

Figure 5-78 is similar to Figure 5-77 except that its metal components have a spherical contour, allowing for torsion about the center line and radial axis. For each of these directions the radial-load deflection characteristic is quite stiff. The axial characteristic is indeed stiffer than the shear in the previous configuration. The torsion about the axial axis is also similar, but the torsion about the radial axial axis is soft. 

Figure 5-80 shows another variation of Figure 5-79, which produces high radial and axial load-deflection characteristics but maintains a soft torsional nature. This design is basically a combination of the flat, high shape-factor part described in Figure 5-76, and the circular part described in Figure 5-77. 

An elastomer is ideal in the vessel environment because it will not corrode. Metal components are protected by being totally encapsulated in an elastomer and then bonded to all-metal surfaces. In examining the load-deflection characteristics of shear, compression, and buckling systems, the one that results in the lowest reaction force generally also produces the lowest-cost structure. Figs 2.13 to 2.15 show six results... 

Figure 1.1 shows two idealized load/deflection characteristics for fibres. In the case (a) the behaviour is linear to failure, while in (b) the fibre stiffens as it is extended. This type of behaviour is exhibited by some... 

Figure 1.1(a) Idealized load/deflection characteristic for a fibre linear to failure. 

A simple test was devised to study load-deflection characteristics of molded and extruded articles under parallel plate loading. A crush tester such as the one illustrated in Figure 12-11 is employed. It consists of a variable speed drive, two parallel plates, one of which is stationary, and a load cell to measure applied force. A dial indicator is used to measure deflection. More sophisticated compression testers such as the one shown in Figure 2-21 can also be used. 

The load deflection characteristics of these types of component are often critical for their application. Natural rubber and the high cis-polyisoprenes have load/deflection properties which are not dissimilar, however, the uniformity of the synthetic polymer is always greater than for the natural product and reproducibility of properties is assured. Since engineering components such as railway locomotive suspension units are often complex and extremely expensive to produce, this uniformity of product ensures a lower incidence of rejection. 

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