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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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Journal ArticleDOI
TL;DR: In this article, the authors measured the temperature-dependent onset of strain relief in metastable Si/sub x/Ge/sub 1-sub 1 − 1 − sub x/ strained layers grown on Ge substrates and proposed that strain breakdown is most directly determined not by thickness and lattice mismatch, but rather by an ''excess'' stress (the difference between the strain due to misfit strain and that due to dislocation line tension).
Abstract: We have measured the temperature-dependent onset of strain relief in metastable Si/sub x/Ge/sub 1-//sub x/ strained layers grown on Ge substrates. On the basis of these measurements, and physical arguments, we propose that strained-layer breakdown is most directly determined not by thickness and lattice mismatch, but rather by (1) an ''excess'' stress (the difference between that due to misfit strain and that due to dislocation line tension) and (2) temperature. With use of these parameters, observed regimes of stability and metastability are shown to be described within a simple, unified framework.

173 citations

Journal ArticleDOI
TL;DR: In this article, a broad range of experiments on carbon black filled polystyrene melts is presented, which represents one of the most extensive investigations of a series of highly filled polymer melts.
Abstract: A broad range of experiments on carbon black filled polystyrene melts shows the reinforcing effect of the filler. This study represents one of the most extensive investigations of a series of highly filled polymer melts. Stress relaxation and dynamic experiments characterize the small strain behavior while the steady state shear viscosity, normal stresses, and elongational flow experiments describe the large strain deformation rate response. Extrudate swell and unconstrained shrinkage of extrudates are also measured. Highly filled systems exhibit yield values. This is seen in the dynamic experiments and in the shear and elongational viscosities. Viscosity does not level off at finite values with decreasing deformation rate but continues to increase in an approximately inverse manner. This corresponds to yield values of order 5 × 105 dynes/cm2. The storage modulus also does not tend to zero at low frequencies. The small strain dynamic properties and stress relaxation results suggest high memories for small strain experiments. Txtrudate swell values are however small and the systems exhibit minimal delayed recovery. The implications of this are considered. Generally it is argued that at volume loadings between 10 and 20 percent, the system takes on the characteristics of a gel and the response is similar to that of a Schwedoff body.

172 citations

Journal ArticleDOI
D. Lee1, E. W. Hart1
01 Apr 1971
TL;DR: Stress relaxation tests have been made in the temperature range 200° to 400°C on two materials, the Mg-Al eutectic alloy and commercial purity zirconium.
Abstract: Stress relaxation tests have been made in the temperature range 200° to 400°C on two materials, the Mg-Al eutectic alloy and commercial purity zirconium. The materials represent respectively high and low homologous temperature regimes. The novel features of the tests are the use of high speed, high sensitivity digital measurement techniques and the direct reduction of the data to stress-strain rate curves. It was possible in this way to obtain phenomenological information on the material behavior over a very large range of strain rate with very few specimens. Comparison was made with results obtained by more conventional differential strain rate tests. The test lends itself well to establishing the phenomenology of mechanical behavior of metals.

172 citations

Journal ArticleDOI
TL;DR: In this article, the authors show that the relaxation of stress birefringence around the fiber fragment may not be an unambiguous measure of fiber-resin adhesion.
Abstract: Microscale (25 mm gauge length) “dogbone” resin specimens with single carbon fibers embedded through the length of the specimen have been studied as a method for determining the fiber-resin interphase strength. The specimens are pulled in tension until the fiber fragments to a critical length, lc . Evidence is presented here, based primarily on the relaxation of stress birefringence around the fiber fragment, that this test may not be an unambiguous measure of fiber-resin adhesion. Data obtained for various production lots of AS-4, AS-6, and IM-6 fibers indicate an increase in lcd with laminate tensile strength. Although there is theoretical justification for this correlation, it requires that the interphase shear strength is relatively constant. In those instances where interfacial adhesion was expected to be low, i.e., surface contamination or unsurface treated fiber, there was a significant increase in lc/d and usually a distinct difference in stress birefringence compared to “good” adhesion. ...

172 citations

Journal ArticleDOI
TL;DR: In this article, the viscoelastic properties of an associative polymer with a backbone consisting of methacrylic acid and ethyl acrylate were determined using the technique of superposition of oscillations upon steady shear flow, enabling the structure of the polymer to be investigated.
Abstract: The viscoelastic properties over a range of steady shear conditions of an alkali-swellable associative polymer have been determined using the technique of superposition of oscillations upon steady shear flow, thus enabling the structure of the polymer to be investigated. The associative polymer studied consists of a backbone of methacrylic acid and ethyl acrylate to which is attached macromolecules containing C20 hydrophobes via an ethylene oxide−isocyanate linkage. A 1 wt % solution with its pH adjusted to 9.5 was used. At high pHs, the polymer solubilizes to form a network of both intra- and intermolecular associating hydrophobic junctions. The solution shows a non-power-law shear-thinning behavior: the viscosity flow curve, when plotted against shear stress, shows two distinct regions where network rupture is prominent, at stress of 2 Pa and between 40 and 50 Pa. By superimposing small amplitude oscillations on to shear flow at constant stresses, the network structure of the polymer is unperturbed and...

170 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023145
2022390
2021266
2020276
2019270
2018281