Damping specific capacity

Modtilus Measurements Another SCC test technique is the use of changes of modulus as a measure of the damping capacity of a metal. It is known that a sample of a given test material containing cracks will have a lower effec tive modulus than does a sample of identical material free of cracks. The technique provides a rapid and reliable evaluation of the susceptibility of a sample material to SCC in a specific environment. The so-called internal friction test concept can also be used to detect and probe nucleation and progress of cracking and the mechanisms controlling it. 

Damping is often expressed in terms of quantities conveniently obtained with the type of instrument used. Since there are so many kinds of instruments, there are many damping terms in common use, such as the logarithmic decrement A, the half-width of a resonance peak, the half-power width of a resonance peak, the Q factor, specific damping capacity i <, the resilience R, and decibels of damping dB. 

Notation, k is the wavenumber, Us the sound velocity, F the damping coefficient (11), r the shear viscosity, po the uniform mass density, k the heat conductivity, and Cp the specific heat capacity at constant pressure [4]. 

Specific bulk modulus, 792 Specific conductivity, 287 Specific damping capacity, 411 Specific entropy of fusion, 791 Specific expansivity, 791 Specific heat, 791... 

The specific damping capacity At//t/ of a system is obtained by normalizing to the maximum strain energy of the system ((r ejl) to give... 

The reciprocal of the phase angle is called the quality factor Q and is often used in the description of electric circuits. The inverse of Q, i.e., Q, is often called the loss factor. The specific damping capacity of the SLS can, therefore, be expressed as AUIU=2tt8=2ttQ. Although these factors depend on frequency, they should be independent of the stress amplitude. In order to characterize the loss peak in Fig. 5.16, it is common practice to measure the peak width at 1/V2 of the maximum loss, which is approximately equal ioQ. ... 

Assume an SLS is being subjected to sinusoidal stress cycling with ,=75 GPa, 2=70 GPa and 17 = 14 MPa s. Plot the phase difference, storage modulus and loss modulus as a function of frequency. At what frequency does the maximum energy dissipation occur What is the specific damping capacity of the material at this frequency ... 

The DNA-binding domain of mPARP-2 (aa 1-65 Fig. 2) was identified on the basis of its capacity to bind damped DNA in a Southwestern assay. Using precisely defined DNA ends, we demonstrated that purified mPARP-2 binds specifically to a gap of one nucleotide (F. 3A) and protects about 10 nucleotides. In contrast to PARP-1, PARP-2 does not bind to a break (Fig. 3B). The affinity of PARP-2 for the inside of the double helix can also be visualized by electron microscopy (Fig. 3C) where the protein accumulates and seems to displace one of the two DNA strands (arrows) when a break is present. 

Fig. 23.7 Specific damping capacity versus applied maximum load (10 load cycles/load level) for (a) polypropylene-based composites with MAH-PP-treated jute wovens (b) epoxy-based composites with alkali-treated (shrinkage = 0%) unidirectional jute fibre [47]...

Why are cold, damp air and hot, humid air more uncomfortable than dry air at the same temperatures (The specific heat capacities of water vapor and air are approxirmtely 1.9 and... 

Sometimes, the specific damping capacity, denoted D, is used instead of the loss coefficient ... 

It has been shown that heat rise during fatigue is directly proportional to the damping capacity of the material. Heat rise is specifically proportional to damping as measured by loss compli-... 

Since ceramics have a non-negligible relative humidity is expected that the material contains a certain percentage of water (3-4%). Thus, this water contributes to the heat capacity of the material. If the medium in which the ceramic is immersed is wet, due to the permeability of the same, a certain percentage of water will be present in the porous ceramic. Water therefore contributes, with a specific heat. In the evaporation temperature (T=100 °C), we get a peak related to the latent heat of evaporation (Figure 18.3). The specific heat in the ceramic shows a slight increase with the temperature and a peak associated with the evaporation of the capillary water that is easily identifiable depending on the absolute dampness of the masonry [2,23, 32]. 

In a vibrating structure, the overall damping level for a particular mode of vibration will depend on the materials, the geometric form, and the mode of vibration. For most structures, it is unlikely that a single damping value exists which applies to all modes of vibration especially if (anisotropic) composite materials are used (Lin et al. 1984 Maheri et al. 2008). It is convenient to use the specific damping capacity (SDC), which was defined above, as the unit of damping. For a structure, we have... 

Specific damping capacity values for 25 mm overlap joints (OR is 0.125)... 

Guild FJ, Adams RD (1981) A new technique for the measurement of the specific damping capacity of beams in flexure. J Phys E Sci Instrum 14 355-363... 

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