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Stress relaxation
About: Stress relaxation is a research topic. Over the lifetime, 12959 publications have been published within this topic receiving 270815 citations.
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TL;DR: In this article, it was shown that the bombardment of high quality cubic (c-) BN films with 300 keV Ar+ ions leads to a strong relaxation of their compressive stresses without destroying the cubic phase if the total ion fluence is kept below an upper limit.
Abstract: It is shown that the bombardment of high quality cubic (c-) BN films with 300 keV Ar+ ions leads to a strong relaxation of their compressive stresses without destroying the cubic phase if the total ion fluence is kept below an upper limit. In addition, it was found that on top of such a stress-relieved film a further pure c-BN layer can be grown, but it builds up compressive stress again. Based on both results, a procedure is developed to grow thick (>1 μm) c-BN films (>80% c-BN) exhibiting low residual stress and long term stability under ambient conditions.
83 citations
TL;DR: In this article, Johnson et al. were the first to identify peculiar rate effects in resonant bar experiments on various earth materials, and they were also seen in both sedimentary and crystalline rocks, and have since been seen in geomaterials like concrete.
Abstract: In 1996 Johnson
et al. were the first to identify peculiar rate effects in resonant bar experiments on various earth materials. The effects were evident on time scales of minutes to hours. They were also seen in both sedimentary and crystalline rocks, and have since been seen in geomaterials like concrete. Although these effects resemble some aspects of creep and creep recovery, they can be induced by a sinusoidal acoustic drive at strains three orders of magnitude below typical creep experiments. These strains are only a few tenths of a microstrain. Moreover, unlike most creep behavior, the effects have been shown to be macroscopically reversible and repeatable, over hundreds of experiments spanning nearly a year. The unique excitation and character of these rate effects cause them to be called slow dynamics. A review and discussion of slow dynamics is presented, pointing out similarities and differences with ordinary creep and focusing on laboratory experiments. A brief description of some possible mechanisms is included, and a new experiment on a sample of Berea sandstone in ultra high vacuum is shown to point out new research that hopes to help ascertain the role of water as a potential mechanism.
83 citations
TL;DR: By molecular-dynamics simulations of a model polymer system, one shows the virtual absence of correlations between the instantaneous elasticity and the structural relaxation, and a well-defined scaling is evidenced by considering the elastic response observed at intermediate times after the initial fast stress relaxation.
Abstract: The elastic models of the glass transition relate the increasing solidity of the glassforming systems with the huge slowing down of the structural relaxation and the viscous flow. The solidity is quantified in terms of the instantaneous shear modulus G(∞), i.e., the immediate response to a step change in the strain. By molecular-dynamics simulations of a model polymer system, one shows the virtual absence of correlations between the instantaneous elasticity and the structural relaxation. Instead, a well-defined scaling is evidenced by considering the elastic response observed at intermediate times after the initial fast stress relaxation. The scaling regime ranges from sluggish states with virtually pure elastic response on the picosecond time scale up to high-mobility states where fast restructuring events are more apparent.
82 citations
TL;DR: Chang and Zoback as mentioned in this paper examined the viscoplastic deformation of room-dried unconsolidated Gulf of Mexico (GOM) shale from the South Eugene Island field.
82 citations
TL;DR: The morphology of solution cast films of butadiene and styrene block polymers in both stretched and unstretched state has been studied by electron microscopy, and has been related to the mechanical behavior of these materials as mentioned in this paper.
Abstract: The morphology of solution cast films of butadiene and styrene block polymers in both stretched and unstretched state has been studied by electron microscopy, and has been related to the mechanical behavior of these materials. These micrographs confirm the indications from dynamic properties that this material consists of a two-phase system in which the relationship between the phases is sensitive to the solvent system used in casting. Although the basic morphological unit is a polystyrene sphere of 100 A diameter dispersed in a matrix of polybutadiene, the interaction between spheres is complex. These spheres are more deformable than would be predicted from their glass transition temperature. The dynamic mechanical properties, stress-strain properties, and stress relaxation properties of block polymers of styrene and dienes can be explained in terms of the morphology and changes of morphology on stretching in the electron microscope.
82 citations