Dynamic-mechanical load

Dynamic mechanical load on elastomer products is often exerted at small deformations and low deformation rates but over extended time periods. Then part of the mechanical energy is dissipated into heat depending on the value of the loss modulus. As a consequence, a temperature profile is established within the sample. Then the modulus... 

Spectral analysis techniques to study the behavior of pol3rmers subjected to dynamic mechanical loads and/or deformation is called Fourier Transform Mechanical Analysis (FTMA). FTMA measures the complex moduli over a range of frequencies in one test by exciting the sample by a random signal (band limited white noise) (13.14). FTMA overcomes or circumvents problems inherent in other test methods because it measures dynamic mechanical properties over a wide range of frequency with minimal temperature and moisture changes within the sample. 

By means of the combined approach of experiment and simulation, the influence of several parameters, such as membrane layer composition, residual stress, thickness, and particle-related properties, were quantified. An empirical model was deduced which allows design rules to be developed for membranes with increased time to failure under dynamic mechanical loads. 

The exposure of synthetic mbber nanocomposites during service against environmental influences like oxygen, temperature, static and dynamic mechanical load or UV-light effects aging processes. 

Mechanical Load. Static mechanical load by strain leads to stretching of random-coil polymer chains in the direction of sample elongation and chain compression in the orthogonal directions. The value of the residual dipolar and quadrupolar couplings is increased by the mechanical load, and moreover, the distribution of the correlation times is also modifled. Therefore, many NMR parameters sensitive to the residual dipolar couplings and slow motions can be used for characterization of the local strain-stress effects in heterogeneous elastomers (158,160,161,179). Dynamics mechanical load leads to sample heating where the temperature distribution in dynamic equilibrium is determined by the temperature-dependent loss-modulus and the thermal conductivity of the sample. Because transverse relaxation rate (approximated by the T2 relaxation) scales with the temperature for carbon fllled SBR, a T2 map provides a temperature map of the sample. Such temperature maps have been measured for carbon-black filled SBR cylinders for different filler contents and mechanical load (180). 

Villanueva, I., Weigel, C. A., and Bryant, S. J. 2009. Cell-matrix interactions and dynamic mechanical loading influence chondrocyte gene expression and bioactivity in PEG-RGD hydrogels. Acta Biomaterialia, 5, 2832-2846. 

Bian, L. et al.. Dynamic mechanical loading enhances functional properties of tissue-engineered cartilage using matme canine chondrocytes. Tissue Eng Part A, 2010.16(5) 1781-90. 

Solder interconnect reliability is the probability of the solder interconnects to perform the intended functions (electrical, mechanical and thermal), for a prescribed product life, under applicable use conditions (such as temperature, humidity, cyclic temperature variations, voltage, current density, static and dynamic mechanical loading, and corrosion), without failures. Failures may manifest themselves in different modes, such as electrochemical or mechanical, and may occur at various system interconnection locations (components, substrates, and/or solder joints). 

M. Arra, D. Xie, and D. Shangguan, Performance of QFP Lead-Free Solder Joints Under Dynamic Mechanical Loading, International Journal of Microcircuits and Electronic Packaging, Vol 24(4), 2001, p 346-365... 

---