Ultimate crushing strength

For regeneration to be technically viable, it must be able to remove deposited vanadium and nickel quantitatively as well as the carbonaceous coke which was co-deposited. The catalyti-cally active metals should remain unaffected in amount, chemistry, and state of dispersion. The alumina support should remain intact, with the surface area, pore-size distribution and crush strength after treatment comparable to that of the original. To be economically viable, the process should be accomplished in a minimum of steps at nearly ambient temperatures and preferably in aqueous solution. The ultimate proof of any such scheme is for the catalytic activity of the regenerated catalyst to be equal to that of a fresh one. 

Compressive strength, or ability of a specimen to resist a crushing force, is measured by crushing a cylindrical specimen (ASTM-D-695) as shown in Figure 14.14. Here a sample of specified dimensions is placed between two heads, one movable and one set. Force is applied to the movable head moving it at a constant rate. The ultimate compression strength is equal to the load that causes failure divided by the minimal cross-sectional area. Since many materials do not fail in compression, strength reflective of specific deformation is often reported. 

The unit stress represented by the maximum ordinate is the ultimate (maximum) strength (Figure 2, Point B). This point estimates the maximum stress at the time of failure. Many of the mechanical properties of interest to the engineer, such as maximum crushing strength or ultimate bending strength, describe this point of maximum stress. 

Examples of wood in compression parallel to the grain are wooden columns or the top chord of a roof truss. Compression-par-allel-to-the-grain strength or the maximum crushing strength is derived at the ultimate limit value of a standard stress-strain curve. 

The hydraulic crush point of a foam is also important in determining to what maximum hydrostatic pressure it can be subjected without rapid failure via high water absorption. Water absorption is another important factor. A high-quality syntactic foam displayed less than 3% water absorption after six weeks of exposure to its ultimate hydrostatic strength for 1-in-diameter by 2-in-long test specimens. The test pressure employed should be not greater than 75 to 80% of the crush point. 

This comparison illustrates that the lateral drift in the lower part of the wall has more flexibility and ductility in MDFEA than in the ZEUS-NL analysis. This is mainly due to the much larger shear deformation contributions that are captured in the continuum model of the MDFEA. At higher load levels, the ZEUS-NL model exhibits lower stiffness and ultimately less strength than the MDFEA model. This is mainly because, the plane section assumption in the fiber approach leads to concrete crushing at wall s base earlier than the concrete compressive capacity is reached in the continuum model. 

The crush resistance of paper under compressive stress is measured as the short span compression strength. To prevent the sample kinking, the free span length must be very small (typically 0.7 mm). The resistance measured according to DIN 54 518 gives the ultimate crushing load per unit width. 

Special precautions must be taken regarding end bearing for these members to avoid crushing of the web at peak response. If end bearing controls, the allowable response is limited to reduce the chance for non-ductile failure. Connections for these members also present difficulty because of the thin web material. To develop the ultimate strength of a member, multiple fasteners may be required so that the shear strength of the materia is not exceeded. 

Strain is the physical distortion of the sample from its equilibrium dimensions and is a vector quantity. The extension or compression of the sample causes stress, the force of opposition to the distension of the sample from its equilibrium shape. When an extensional strain is applied to the sample, a tensile strength or force needed to rip the sample apart can be measured. When a compression strain is applied to the sample, a compressive strength or force needed to crush the sample can be measured. The yield stress of a sample is the force at which the polymer begins to rapidly extend, producing a pronounced increase in strain but a lowered rate of inerease in stress in the sample. A sample s ultimate strength is the stress that eauses it to break. 

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