Artigos de revistas: "Plastic slip"

1

Schmalzer, Andrew M., e A. Jeffrey Giacomin. "Die drool theory". Journal of Polymer Engineering 33, n.º 1 (1 de fevereiro de 2013): 1–18. http://dx.doi.org/10.1515/polyeng-2012-0044.

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Abstract When molten plastic is extruded from a die, it sometimes collects on the open face of the die. Known as die drool, this phenomenon costs plastics manufacturers by requiring die cleaning. This has been attributed to many causes, but none of these has led to an equation for the drool rate. In this work, we provide an exact analytical solution for the drool rate, and we base this solution on a postulate of a cohesive slip layer near the die walls. We thus attribute die drool to cohesive failure within the fluid at an internal surface where the fluid slips on itself. We adimensionalize the drool rate with the production rate, and call this the buildup ratio, BR. We provide an exact analytical solution for BR when the cohesive slip layer either slips at the die wall, or when it does not. We examine two important extrusion geometries: slit (which we then extend to pipe) and tube flow. We identify two new experiments: one to measure BR as a function of pressure drop, and another as a function of the die aspect ratio, and we then use our new theory to design droolometers.

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2

Kawano, Yoshiki, Tsuyoshi Mayama, Ryouji Kondou e Tetsuya Ohashi. "Crystal Plasticity Analysis of Change in Active Slip Systems of α-Phase of Ti-6Al-4V Alloy under Cyclic Loading". Key Engineering Materials 725 (dezembro de 2016): 183–88. http://dx.doi.org/10.4028/www.scientific.net/kem.725.183.

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In this paper, we investigated changes in active slip systems of α-phase of Ti-6Al-4V alloy under a cyclic plastic loading using a crystal plasticity finite element method. In the analyses, a bicrystal model was employed, and the crystallographic orientations were set so as that prismatic <a> or basal slip system was the primary slip system in each grain. The results showed that there was a mechanism where the basal slip systems could reach the stage of activation under the cyclic plastic loading even though the condition was that the prismatic <a> slips initially operate. The reason for the activity changes was due to the changes in the incompatibility between the grains by the work hardening, and the effect of the incompatibility on activities of slip systems appeared even in the perpendicular arrangements of the grains to the loading direction.

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3

Zhu, Xiao Hua, Yu Wang, Fu Cheng Deng, Li Ping Tang e Hua Tong. "Optimal Design of Slip Dog Based on the Elasticoplasticity Contact Analysis". Applied Mechanics and Materials 34-35 (outubro de 2010): 1718–23. http://dx.doi.org/10.4028/www.scientific.net/amm.34-35.1718.

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Based on the elasticoplasticity contact analysis theory, a mechanical model for the whole process of the slip holding fast to the drilling pipe is established and a complete method is proposed to assess the performance of slip dog's structural parameters. For drilling pipe systems of different specifications, the coupling effect among tooth anterior corner, posterior corner, tooth height, tooth spacing of slip dog and the effect of the parameter variation on both the drilling pipe and itself after the slips hold fast to the drilling pipe are analyzed, and the slip dog's plastic damage law on the drilling pipe under different parameter combinations is obtained. Using this law to instruct field slip dog design, it is discovered that this slip dog significantly reduces the drilling pipe's plastic damage by both laboratory and field experiments, which has proved the universality and applicability of this method, effectively reduced the drilling operational risk and drilling costs. The technology has been put into use in Sichuan and Chongqing region and acquired good technical assessment.

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4

Yokogawa, Toshiya, Sachi Niki, Junko Maekawa, Masahiko Aoki e Masaki Fujikane. "Dislocation Formation via an r-Plane Slip Initiated by Plastic Deformation during Nano-Indentation of a High Quality Bulk GaN Surface". MRS Advances 1, n.º 58 (2016): 3847–52. http://dx.doi.org/10.1557/adv.2016.165.

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ABSTRACTBulk GaN substrates are of significant interest because they offer both high quality and low dislocation densities. Our group has previously reported the formation and movement of dislocations in high quality bulk GaN in response to nano-indentation. We have also proposed a mechanism involving an r-plane (-1012) slip initiated by plastic deformation during a pop-in event, a theory that was supported by molecular dynamics simulations. Herein, we present experimental evidence for this r-plane (-1012) slip mechanism in an indented GaN surface using nano-indentation with an indenter having a smaller radius (∼100 nm) and imparting a lower pop-in load (∼400 μN) compared to the values applied in our previous studies. In addition, this study included TEM observations immediately after the plastic deformation, such that cross-sectional TEM images of the indented surface of the c-plane bulk GaN were acquired just after the pop-in event. The pyramidal dislocation line of an r-plane slip was clearly observed and was inclined by 43° relative to the c-plane surface. Neither a basal c-plane slip nor a prism m-plane slip occurred as a result of dislocation multiplication as secondary or tertiary slip systems, even though these slips had been identified when employing a larger radius indenter and a higher pop-in load. From these experimental results, we were able to confirm that plastic deformation in bulk GaN is initiated via an r-plane slip.

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5

Zhu, Eryu, Teng Li, Haoran Liu, Chunqi Zhu, Lei Liu, Yuanyuan Tian, Yujie Li e Wei Yang. "Bond-Slip Behavior between Plastic Bellow and Concrete". Advances in Materials Science and Engineering 2022 (14 de junho de 2022): 1–16. http://dx.doi.org/10.1155/2022/2450503.

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Despite the widespread use of plastic bellows in prestressed channels, their poor bonding with concrete and mortar results in “layering,” which limits their application in practical engineering. In this study, the bonding property between plastic bellows and concrete or grout material was investigated using a single-end compression test on plastic bellow concrete. The slip failure mode, ultimate load, and slip of plastic bellows were obtained. Furthermore, the analysis of the bond-slip properties of plastic bellows indicated that the bond strength decreased with increasing bond length. Moreover, the increase in the loading force was greater than the increase in the contact area. Based on the test data, a bond-slip constitutive relationship model was established, which accurately reflects the bond-slip process. The expressions of bond and slip were derived along with different bond positions of plastic bellow concrete specimens. Finally, a three-dimensional finite element model of a plastic bellow concrete specimen was established. The numerical simulation curve was compared with the experimental and fitting curves. The results indicated that the bond strength of the plastic bellow concrete specimen decreased with increasing bond length. The influence of bond strength on the contact area was comprehensively analyzed. This study effectively combines experimental research, theoretical analysis, and numerical simulation to analyze the bond performance between plastic bellows and concrete or grout material.

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6

Liu, Yun Xi, Wei Chen, Zhi Qiang Li, Liang Liang Liu e Dong Liu. "In Situ Observation on the Deformation Behavior of Primary α-Ti in a Textured Ti-6Al-4V". Materials Science Forum 993 (maio de 2020): 365–73. http://dx.doi.org/10.4028/www.scientific.net/msf.993.365.

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The tensile deformation process and dislocation behavior of primary α-Ti of Ti-6Al-4V were studied by the in-situ tensile test combined with EBSD (electron backscatter diffraction). The initiation, evolution and distribution of dislocation slips at different strains were discussed. The results showed that the microtexture of the material had a significant influence on slip behavior. Typically, basal and prismatic <a> slips initiated first, but the dominant slip type was related to the local texture characteristics. Sometimes, the basal and prismatic <a> slips could still initiate when their Schmid factors were relatively low, while the pyramidal slips usually need a higher Schmid factor to initiate. With the increase of strain, the second slip system inside one grain was activated to accommodate the plastic deformation. When the deformation was localized in a specific microtextured region, basal <a> slips were dominant, but eventually the crack initiated from the <c+a> slip bands inside the grain.

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7

Ando, Shinji, Masayuki Tsushida e Hiromoto Kitahara. "Plastic Deformation Behavior in Magnesium Alloy Single Crystals". Materials Science Forum 706-709 (janeiro de 2012): 1122–27. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1122.

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Zn and Al are major alloying elements of Mg alloys. Main slip system of Mg is a basal slip and the CRSS increases with Zn or Al content. According to von-Mises criterion, five kinds of independent slip systems are required for uniform deformation, so it is necessary to activate non-basal slip systems to show good ductility. However, it has not become clear the effect of Zn or Al for non-basal slip systems yet. To investigate deformation behavior of magnesium crystal by non-basal slip, Mg-Zn and Mg-Al single crystals were stretched in the [110] direction and Mg-Zn single crystals were compressed in the [0001] direction. {112}<23> second order pyramidal slip was activated in Mg-0.1at%Zn and Mg-0.5at%Al. On the other hand, {101} twin was mainly activated in Mg-1.0at%Al alloy. Yield stress due to the pyramidal slip of magnesium decreased by 0.1at%Zn addition, however they increased with addition of aluminum..

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8

Ohashi, Tetsuya, Michihiro Sato e Yuhki Shimazu. "Evaluation of Plastic Work Density, Strain Energy and Slip Multiplication Intensity at Some Typical Grain Boundary Triple Junctions". Materials Science Forum 654-656 (junho de 2010): 1283–86. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1283.

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Plastic slip deformations of tricrystals with simplified geometries are numerically analyzed by a FEA-based crystal plasticity code. Accumulation of geometrically necessary (GN) dislocations, distributions of the total slip, plastic work density and GN dislocations on slip systems, as well as some indices for the intensity of slip multiplication are evaluated. Results show that coexistence of GN dislocations on different slip systems is prominent at triple junctions of grain boundaries.

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9

Gerdeen, J. C., W. W. Predebon, P. M. Schwab e A. Shah. "Elastic-Plastic Analysis of Directionally Solidified Lamellar Eutectic Composites". Journal of Engineering Materials and Technology 109, n.º 1 (1 de janeiro de 1987): 53–58. http://dx.doi.org/10.1115/1.3225933.

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Yielding in a crystal structure occurs with plastic slip on preferential planes. It is similar to yielding on maximum shear planes in an isotropic continuum, but in this case the slip is anisotropic. The anisotropic slip is described by 24 piecewise, continuous yield functions, also known as the generalized Schmid’s law for FCC crystals. The plastic strain increment for any one slip mechanism is assumed given by the potential flow law of plasticity. However, there are combined slip situations where two or more slip mechanisms are activated simultaneously. In this paper, the plastic strains for all the possible intersections in FCC crystals are derived, i.e., for intersections of two, four, and eight yield surfaces of compatible stress states. A strain hardening modulus H′ is included by defining an equivalent shear stress τ and an equivalent plastic shear strain γp for each slip system. The analysis is programmed for finite-element solution on the computer, by defining a strain “vector” {dε}, a stress “vector” {dσ}, and an elastic-plastic compliance [C] for each element, relating the strain and stress vectors. The analysis is applied to the elastic-plastic yielding of directionally solidified eutectic systems of Co-CoAl which solidify into a lamellar structure. A plane strain analysis is compared with experiments and good correlation is found for the stress concentration effect when the lamellae have termination points.

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10

Liu, Conghui, Rhys Thomas, João Quinta da Fonseca e Michael Preuss. "Early slip activity and fatigue crack initiation of a near alpha titanium alloy". MATEC Web of Conferences 321 (2020): 11040. http://dx.doi.org/10.1051/matecconf/202032111040.

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For titanium alloys, crack initiation as a result of plastic strain accumulation has been shown to govern fatigue life under the high cycle fatigue regime. In this study, the early plastic slip activity and fatigue crack initiation was studied using a cyclic four point bending test at 10 Hz with a load ratio of 0.1, up to 90% of the proof stress. The plastic slip in the high stress area was monitored by interrupting the test and performing optical microscopy. Following fatigue crack initiation, scanning electron microscopy (SEM) combined with electron backscatter diffraction (EBSD) was used to identify the slip and crack initiation mode in a 600 x 600 μm2 area. Using slip trace analysis, it was shown that primary alpha grains offered dominant plastic deformation with basal slip activation. Cracking along basal planes was determined to be the dominant damage mode.

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11

Anguige, Keith, e Patrick W. Dondl. "Relaxation of the Non-Convex, Incremental Energy-Minimization Problem in Single-Slip Strain-Gradient Plasticity". Key Engineering Materials 651-653 (julho de 2015): 963–68. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.963.

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We consider a variational formulation of gradient elasto-plasticity, as they arise in the incremental formulation of the plastic evolution problem, subject to a class of single-slip side conditions. Such side conditions typically render the associated boundary-value problems non-convex. We first show that, for a large class of plastic deformations, a given single-slip condition (specification of Burgers' vectors and slip planes) can be relaxed by introducing a lamination microstructure. This yields a relaxed side condition which allows for arbitrary slip in a prescribed family of slip planes. This relaxed model can be thought of as an aid to simulating macroscopic plastic behavior without the need to resolve arbitrarily fine spatial scales. We also discuss issues of existence of solutions for the relaxed model.

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12

Ortiz, M. "Plastic Yielding as a Phase Transition". Journal of Applied Mechanics 66, n.º 2 (1 de junho de 1999): 289–98. http://dx.doi.org/10.1115/1.2791048.

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A statistical mechanical theory of forest hardening is developed in which yielding arises as a phase transition. For simplicity, we consider the case of a single dislocation loop moving on a slip plane through randomly distributed forest dislocations, which we treat as point obstacles. The occurrence of slip at the sites occupied by these obstacles is assumed to require the expenditure of a certain amount of work commensurate with the strength of the obstacle. The case of obstacles of infinite strength is treated in detail. We show that the behavior of the dislocation loop as it sweeps the slip plane under the action of a resolved shear stress is identical to that of a lattice gas, or, equivalently, to that of the two-dimensional spin-1/2 Ising model. In particular, there exists a critical temperature Tc below which the system exhibits a yield point, i.e., the slip strain increases sharply when the applied resolved shear stress attains a critical value. Above the critical temperature the yield point disappears and the slip strain depends continuously on the applied stress. The critical exponents, which describe the behavior of the system near the critical temperature, coincide with those of the two-dimensional spin-1/2 Ising model.

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13

Sung, T. H., J. C. Huang, J. H. Hsu, S. R. Jian e T. G. Nieh. "Yielding and plastic slip in ZnO". Applied Physics Letters 100, n.º 21 (21 de maio de 2012): 211903. http://dx.doi.org/10.1063/1.4720169.

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14

Huang, Houxu, Jie Li e Jiuqi Wei. "Analytical Solution of Displacements Around Circular Openings in Generalized Hoek-Brown Rocks". Journal of Theoretical and Applied Mechanics 47, n.º 3 (26 de setembro de 2017): 81–95. http://dx.doi.org/10.1515/jtam-2017-0015.

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AbstractThe rock in plastic region is divided into numbers of elements by the slip lines, resulted from shear localization. During the deformation process, the elements will slip along the slip lines and the displacement field is discontinuous. Slip lines around circular opening in isotropic rock, subjected to hydrostatic stress are described by the logarithmic spirals. Deformation of the plastic region is mainly attributed to the slippage. Relationship between the shear stresses and slippage on slip lines is presented, based on the study of Revuzhenko and Shemyakin. Relations between slippage and rock failure are described, based on the elastic-brittle-plastic model. An analytical solution is presented for the plane strain analysis of displacements around circular openings in the Generalized Hoek-Brown rock. With properly choosing of slippage parameters, results obtained by using the proposed solution agree well with those presented in published sources.

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15

Hayroyan, S. G., e H. S. Hayroyan. "Methods for determining shear resistance by a system of cracks and old slip surfaces with the purpose to evaluate the stability of landslides". Journal of Physics: Conference Series 2231, n.º 1 (1 de abril de 2022): 012017. http://dx.doi.org/10.1088/1742-6596/2231/1/012017.

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Abstract On slopes, landslide displacements mainly occur along bedding boundaries, lithogenetic and tectonic fractures, as well as along existing ancient slip surfaces, which are the weak zones and potential slip surfaces for new landslides. According to experimental studies to determine the shear resistance by the standard and double cut test methods: a) without wetting the sliding surface, and b) by the wetting the sliding surface, we can conclude: when double- cutting the clay soils of a solid, semi-solid and tight-plastic consistency, the cohesion is mainly reduced, but the internal friction factor is slightly changed. Double-cut tests of soft-plastic and flow-plastic clay soils have shown the cohesion and the internal friction factors are being changed insignificantly. At the same time, taking into account the fact that under the condition τ > σ tan φ the soft-plastic and flowing-plastic clay soils undergo viscous-plastic deformations, we come to the following conclusion. When developing the anti-landslide measures, independent of the consistency of the soils forming the slope, the τf = σ tan φ component should be taken as the slip resistance index in the formula for calculating the slip resistance taking into account the condition Cc + Σ w = 0.

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Hayroyan, S. G., e H. S. Hayroyan. "Methods for determining shear resistance by a system of cracks and old slip surfaces with the purpose to evaluate the stability of landslides". Journal of Physics: Conference Series 2231, n.º 1 (1 de abril de 2022): 012017. http://dx.doi.org/10.1088/1742-6596/2231/1/012017.

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Abstract On slopes, landslide displacements mainly occur along bedding boundaries, lithogenetic and tectonic fractures, as well as along existing ancient slip surfaces, which are the weak zones and potential slip surfaces for new landslides. According to experimental studies to determine the shear resistance by the standard and double cut test methods: a) without wetting the sliding surface, and b) by the wetting the sliding surface, we can conclude: when double- cutting the clay soils of a solid, semi-solid and tight-plastic consistency, the cohesion is mainly reduced, but the internal friction factor is slightly changed. Double-cut tests of soft-plastic and flow-plastic clay soils have shown the cohesion and the internal friction factors are being changed insignificantly. At the same time, taking into account the fact that under the condition τ > σ tan φ the soft-plastic and flowing-plastic clay soils undergo viscous-plastic deformations, we come to the following conclusion. When developing the anti-landslide measures, independent of the consistency of the soils forming the slope, the τf = σ tan φ component should be taken as the slip resistance index in the formula for calculating the slip resistance taking into account the condition Cc + Σ w = 0.

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17

Yu, Qin, Jian Wang e Yanyao Jiang. "Inverse Slip Accompanying Twinning and Detwinning during Cyclic Loading of Magnesium Single Crystal". Journal of Materials 2013 (17 de setembro de 2013): 1–8. http://dx.doi.org/10.1155/2013/903786.

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In situ, observation of twinning and detwinning in magnesium single crystals during tension-compression cyclic loading was made using optical microscopy. A quantitative analysis of plastic strain indicates that twinning and detwinning experience two stages, low and high work hardening de-twinning, and pure re-twinning and fresh twinning combined with retwinning. Slip is always activated. For the first time, inverse slip accompanying with pure retwinning and high work hardening detwinning was experimentally identified, which provides insights in better understanding of the activity of twining, detwinning, and slips.

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18

Lian, Yong, Li Hu, Tao Zhou, Mingbo Yang e Jin Zhang. "Numerical Investigation of Secondary Deformation Mechanisms on Plastic Deformation of AZ31 Magnesium Alloy Using Viscoplastic Self-Consistent Model". Metals 9, n.º 1 (5 de janeiro de 2019): 41. http://dx.doi.org/10.3390/met9010041.

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Uniaxial tension and compression of AZ31 magnesium alloy were numerically investigated via the viscoplastic self-consistent (VPSC) model to shed a light on the effect of secondary deformation mechanisms (prismatic <a> slip, pyramidal <c+a> slip, and { 10 1 ¯ 1 } contraction twinning) during plastic deformation. The method adopted in the present study used different combinations of deformation mechanisms in the VPSC modeling. In terms of the pyramidal <c+a> slip, it served as the first candidate for sustaining the extra plastic strain during the plastic deformation. The improvement of activity in the pyramidal <c+a> slip contributed to the increase in the mechanical response and the splitting of pole densities in { 0002 } pole figure during uniaxial tension. As for the prismatic <a> slip, its increasing activity was not only conducive to the improvement of flow stress in mechanical response, but also responsible for the splitting of pole densities in { 0002 } pole figure during uniaxial compression. With respect to the { 10 1 ¯ 1 } contraction twinning, it had a negligible influence on the plastic deformation of AZ31 magnesium alloy in terms of the mechanical response as well as the slip and the twinning activities. However, it is better to include the { 10 1 ¯ 1 } contraction twinning in the VPSC modeling to more accurately predict the texture evolution.

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19

Eterashvili, Tamaz, T. Dzigrashvili e M. Vardosanidze. "Initial Aspects of Low-Cycle Fatigue Fracture of Martensitic Steels". Key Engineering Materials 348-349 (setembro de 2007): 385–88. http://dx.doi.org/10.4028/www.scientific.net/kem.348-349.385.

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This study deals with the SEM and optical microscopic characterization of fatigue plastic deformation process during fatigue crack initiation to understand where, why and how cracks initiate under conditions of low cycle fatigue. Samples were prepared from the 13Х11Н2В2МФ high-chromium stainless steel used for fusion power applications. The low-cycle tests were conducted at room temperature with the standard V-notched samples prepared from conventional stainless steel. The following characteristics were studied during fatigue tests: 1 macrocrack propagation, 2. interaction between macrocrack and isolated microcracks, 3. interaction between macrocrack and slip bands, 4. interaction between macrocrack and microstructure elements of the steel. The above experiments show that during macrocrack propagation a plastic zone is formed around it, where isolated microcracks and slip bands of 2-3 different directions are observed. Measurement of plastic zone dimensions after different number of cycles of deformation show that plastic zone size increases during the first stage of cyclic deformation (until definite number of cycles are completed), and then remains unchanged. The observations show that main crack is composed of individual micro-components, the lengths of which are in a good correlation with the dimensions of microstructure elements of the steel (former austenite grains, martensite crystals). It was revealed that during growth, as a rule, macrocrack rarely propagates along isolated microcracks and slip bands. Direction of macrocrack propagation changes while passing from one microstructure element to another, so that main direction is the same. No preferable transcrystalline or intercrystalline propagation of macrocrack has been observed in the investigated steel. It is shown that after subsequent fatigue tests, dimensions of the previously created slip bands increase, and additional new slip band are also formed. The sites and frequency of slip bands’ formation in plastic zone are also studied. It was observed that the boundaries and mainly the sites of intersection of martensite crystals are the sites of isolated (rough) microcracks’ formation. The dimensions of slip bands are comparable with those of martensite crystals. The angles between the main crack propagation direction and slip bands varied from 30o to 60o, however, most of the slip bands were oriented at 45o to the main crack. Based on the obtained results a conclusion is made that plastic deformation in samples go inhomogeneously. In plastic zones, along with the heavily deformed areas, almost non-deformed areas are also observed. The speed of fatigue fracture increases with the increase in frequency and amplitude of deformations. Generally, the annealed samples are destructed prematurely in comparison with non-annealed ones of the investigated steel.

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Man, Jiří, Anja Weidner, Petr Klapetek e Jaroslav Polák. "Slip Activity of Persistent Slip Bands in early Stages of Fatigue Life of Austenitic 316L Steel". Key Engineering Materials 592-593 (novembro de 2013): 785–88. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.785.

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Flat specimen of 316L steel was cyclically pre-deformed with constant plastic strain amplitude to early stage of fatigue life relevant to the period of cyclic strain localization and fatigue crack initiation. To document slip activity and reversibility/irreversibility of persistent slip bands (PSBs) in situ experiments in the high-resolution SEMFEG under special imaging conditions were performed. The half-and full-cycle slip activity and distribution of plastic strain within PSBs in individual grains were investigated via slip steps generated in half-and full-cycle deformation after intermediate vibration polishing. After completion of in situ tests the surface topography in identical locations was quantitatively documented using atomic force microscopy (AFM).

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21

Zaiser,, M., e E. C. Aifantis,. "Avalanches and Slip Patterning in Plastic Deformation". Journal of the Mechanical Behavior of Materials 14, n.º 4-5 (setembro de 2003): 255–70. http://dx.doi.org/10.1515/jmbm.2003.14.4-5.255.

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Muñoz, A., A. Domínguez-Rodríguez e J. Castaing. "Slip Systems and plastic anisotropy in CaF2". Journal of Materials Science 29, n.º 23 (dezembro de 1994): 6207–11. http://dx.doi.org/10.1007/bf00354561.

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23

Tabatabaei Mirhosseini, Ramin, Ehsan Araghizadeh e Soroush Rashidi. "Approximate Relationship for the Bond-Slip Using a Concrete Damage-Plastic Model". Advances in Materials Science and Engineering 2023 (17 de abril de 2023): 1–15. http://dx.doi.org/10.1155/2023/1320192.

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This paper presents an approximate multicontact model to study dynamic bond stress-slip based on the concrete damage-plastic model. To establish the bond stress-slip between rebar and concrete, an elastic-plastic steel cylinder contact element was used as the tube (ring contact element), and then, by reducing the bond strength, the amount of slip between rebar and concrete and its effect on concrete damage-plastic parameters were considered. When concrete cracks, the parameters of concrete cracking, the plasticity of rebar and concrete fracture, and the pull-out of rebar from concrete are used to consider the bond-slip relationship between rebar and concrete. Meanwhile, an external constraint in the cylinder model is taken into account. The bond strength calculated by the presented model is compared with the pull-out test specimen results, and the errors are generally within 15%. Finally, using the results obtained from the amount of slip in models, an approximate mathematical relationship between the slip of the rebar inside the concrete can be obtained in terms of the resistance of the ring contact element (instead of the concrete surrounding). This formula can be used to calculate the bond-slip rate of all the rebars of a structure. The results of the mentioned model using the ABAQUS software demonstrated that by reducing the strength of the ring contact element by 20%, slip increased by 4.2%. Also, with an 80% reduction in ring strength, the bond-slip rate increases by 45%. The proposed approximate relationship has reasonable accuracy and lower computational cost.

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Uehara, Takuya. "An Atomistic Study on the Slip Deformation Mechanism of Crystalline Materials Using a Weak-Plane Model". Applied Mechanics and Materials 197 (setembro de 2012): 321–26. http://dx.doi.org/10.4028/www.scientific.net/amm.197.321.

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Molecular dynamics simulations were carried out to investigate the plastic deformation mechanism of fcc crystalline materials using the conventional Lennard-Jones potential. An fcc structure with square cross-section was prepared, and a tensile load was applied in the longitudinal direction. A weak potential was assigned to a specific (111) plane to induce a slip on the specified plane. Accordingly, a slip was initiated in the weak plane following an elastic deformation. The step-by-step motion of the atoms on the slip plane was studied, and a detailed trajectory is presented. The slip then expanded to other planes, and plastic deformation progressed in the whole model. The weak plane was also set as (110) or (100) plane, where different deformation modes were observed: not only slip but also gradual distortion or brittle fracture occurred.

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25

Serre, Ingrid, Daniel Salazar e Jean Bernard Vogt. "Plastic Deformation Quantified by Atomic Force Microscopy Measurements for Duplex Stainless Steel under Monotonic and Cyclic Loading". Applied Mechanics and Materials 13-14 (julho de 2008): 163–72. http://dx.doi.org/10.4028/www.scientific.net/amm.13-14.163.

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By atomic force microscopy, the plastic deformation marks resulting from monotonic and cyclic plastic deformation were analysed to study the plasticity in each phase of Duplex Stainless Steels. In austenite, straight slip bands were observed after monotonic loading. These straight slip bands seem to serve as fatigue extrusion nucleation sites, which are the marks of the accommodation of the cyclic plasticity by the austenite. In ferrite, after monotonic loading, slip bands, could be classified into two different groups depending on whether they result from the bulk activities of ferrite or whether their formation is assisted by the plastic deformation of austenite. It was found that the crystallographic misorientation based on a Kurdjomov-Sachs relationship is the factor controlling one or the other type. After the first 5 loading cycles, the ferrite presents only monotonic plastic marks. This suggests no direct contribution of the ferrite to the accommodation of the cyclic plasticity.

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26

Polák, Jaroslav, e Jiří Man. "Cyclic Slip Localization and Crack Initiation in Crystalline Materials". Advanced Materials Research 891-892 (março de 2014): 452–57. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.452.

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Cyclic plastic straining in crystalline materials is localized to persistent slip bands (PSBs) and results in formation of persistent slip markings (PSMs) consisting of extrusions and intrusions. Intensive plastic strain in PSBs results in dislocation interactions and formation of point defects. The extended model based on point defect formation, migration and annihilation is presented describing surface relief formation in the form of extrusion-intrusion pairs. Point defect migration and resulting mass transfer is the principle source of cyclic slip irreversibility leading to crack-like defects - intrusions. Fatigue cracks start in the tip of sharp intrusions.

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Eterashvili, Tamaz, T. Dzigrashvili e M. Vardosanidze. "TEM Study of Microstructure Changes, Formation and Distribution of Slip Bands in Austenitic Steels after Low-Cycle Fatigue (LCF) Deformation - II". Key Engineering Materials 665 (setembro de 2015): 141–44. http://dx.doi.org/10.4028/www.scientific.net/kem.665.141.

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The microstructure changes, development of micro plastic deformation and formation and distribution of slip bands were studied. It is shown that development of micro deformation during LCF depends on loading conditions (amplitude and number of cycles) and microstructureIt is shown that as non-localized as well as localized micro plastic deformation takes place because of structural inhomogeneity. Supposedly, the localized deformation is related to the sites of internal stress concentration accumulated during the LCF.The effect of microstructure of structural steels on the rate of local cyclic deformation, leading to nucleation and growth of slip bands of fatigue cracks, was studied. The interaction of slip bands with precipitates, grain boundaries and low-angle boundaries were also analyzed.The sites of nucleation of primary and secondary slip bands were identified, and the following aspects were considered: 1. the possibility of microcrack nucleation on (or in) slip bands, 2. The kind of slip bands the slip bands may nucleate in, 3. The potential sites (except the slip bands) and reasons of nanocrack formation are specified.

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Xu, Biqiang, e Yanyao Jiang. "Elastic-Plastic Finite Element Analysis of Partial Slip Rolling Contact". Journal of Tribology 124, n.º 1 (26 de março de 2001): 20–26. http://dx.doi.org/10.1115/1.1395630.

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The finite element model with the implementation of a robust cyclic plasticity theory was used to simulate the elastic-plastic stresses for the partial slip (stick-slip) line rolling contact. Detailed rolling contact stresses and strains were obtained for up to 40 rolling passes. The partial slip condition greatly affects the residual stress in the rolling direction and the residual shear strain within a thin layer of material near the contact surface. The residual stress in the axial direction was not significantly influenced by the partial slip condition. An increase in friction coefficient drives the location of maximum shear strain to the contact surface. In addition, a comparison was made between the finite element results and the results obtained from an approximate method.

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Xu, Shuang, e Ya Fang Guo. "Effects of Strain Rate on the Tensile Deformation of Single-Crystal Copper Films". Materials Science Forum 675-677 (fevereiro de 2011): 671–73. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.671.

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Molecular dynamics (MD) simulations with an EAM potential are carried out to study the strain rate effects on the tensile deformation of single-crystal copper films. The stress, the atomic energy, as well as the atomic configurations of the systems are presented to explore the strain rate effects on copper films. It is found that yield stress increases with loading rate. Meanwhile, deformation mechanisms with different strain rates are analyzed in the present work. At lower strain rate, slips along {111} planes are primarily responsible for the plastic deformation in nano-Cu films. As strain rate increased, the motion of dislocations becomes easier, a transition of the deformation mechanism from sequential propagation of slips along well-defined slip planes to complex cross-slip.

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Matsugaki, Aira, Gento Aramoto, Takuya Ishimoto e Takayoshi Nakano. "Control of Osteoblastic Cell Behavior by Surface Topography Introduced by Plastic Deformation of Ti Single Crystal with h.c.p. Structure". Materials Science Forum 706-709 (janeiro de 2012): 549–52. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.549.

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Cells are known to sense the topographic features of the substrate and align along the direction of the surface pattern, and this is believed to be an important aspect in the formation and regeneration of anisotropic biological tissues. In this study, a unique and anisotropic stepped pattern was produced on single crystals of α-Ti with the h.c.p. lattice by plastic deformation in compression to demonstrate the effect of the pattern on cell behavior. Because the Schmid factor for the operative slip system of prismatic (100)[110] was set to be 0.5, the slip traces with an acute angle of 45° appeared on the surface. A smooth substrate without plastic deformation was used as a control. MC3T3-E1 osteoblastic cells were cultured on the substrate for 24 h, followed by observation of the morphology and alignment of the cells by Giemsa staining. On stepped substrates, cells aligned along the slip traces, and the filopodia of the aligned cells were found to extend parallel to the slip traces. The slip traces induced by plastic deformation of a single crystal was successfully proven to be a potent substrate to control the alignment of cells.

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Matsuno, Hiroshi. "Characteristics of Complementary Plastic Energy Produced by Hysteresis Curves and Analyses of Microstructures in Fatigued Metals". Key Engineering Materials 340-341 (junho de 2007): 513–18. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.513.

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Experimental characteristics of complementary plastic energy produced by a stress-strain hysteresis curve at a saturated stage in low cycle fatigue are investigated for some steels, and mechanical models for analyzing microstructures of fatigued metals are discussed. As a result, it is found that volume of a cell is varied in inverse proportion to plastic strain range: the density of cells is in proportion to plastic strain range. Consequently, the total number of cells is proportional to plastic strain range. This final conclusion is similar to Winter's opinion concerning persistent slip band structures in high cycle fatigue [1] where, although wall spacing of a cell is invariable and inde-pendent of plastic strain range, a region occupied by persistent slip bands increases proportionally to plastic strain range and consequently the number of cells is in proportion to plastic strain range.

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Zhang, Xin Ming, e Yang Xiao. "Fracture Mechanism Analysis of Mg-9Gd-4Y-0.6Zr Alloy". Materials Science Forum 546-549 (maio de 2007): 261–66. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.261.

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The fractographs of Mg-9Gd-4Y-0.6Zr alloy specimens which were tensioned at different temperatures were investigated by optical and scanning electron microscopy, respectively. The results showed that different slip systems were activated at different temperatures, which were responsible for varied deformation mechanisms and fracture mechanisms. At 25 °C, the enabled slip systems were few and only the slip systems on basal plane were able to be activated, so cleavage fracture was observed. At −196°Cthe number of enabled slip systems increased, prismatic or pyramidal slip maybe occurred, so that an obvious low-temperature plasticity was observed, while fracture mechanisms were mainly microvoid coalescence fracture with cleavage fracture in local areas. At 250 °C, 300 °C and 350 °C, the multisystem slips on the basal planes, the prismatic planes and the pyramidal planes were able to be activated, while fracture mechanisms were also microviod coalescence fracture. At 400 °C, recrystallization happened, grain-boundary sliding in new fine recrystallized grains made the plastic deformation easy, showing coarse-grain superplasticity phenomenon, and an intergranular shear fracture took place.

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Setz, Luiz Fernando Grespan, Laís Koshimizu, Sonia Regina Homem de Mello-Castanho e Márcio Raymundo Morelli. "Rheological Analysis of Ceramics Suspensions with High Solids Loading". Materials Science Forum 727-728 (agosto de 2012): 646–51. http://dx.doi.org/10.4028/www.scientific.net/msf.727-728.646.

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The pure oxides (yttria, zirconia, titania, alumina, etc.) pastes ceramics production by concentrate suspensions is interesting because differently than plastic ceramics (clays), where these behaviours are often empirical available, the rheological suspensions behaviour are extensively studied. Thus, controlling the concentrate slips rheological parameters, is possible extend these analysis for better understand and control the plastic pastes production, providing subsidies to obtain after shaping process, such as extrusion and calendering, suitable products for the desired application. Thus, alumina suspensions rheological behaviour, with high solids loading (> 50 vol.%) adequately stabilized, slip cast shaped are available in this work. High solids loading suspensions, up to 60 vol.%, presents adequate flow for thickeners/plasticizers elements adds to produce ceramic plastic pastes.

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Polák, Jaroslav. "Role of Persistent Slip Bands and Persistent Slip Markings in Fatigue Crack Initiation in Polycrystals". Crystals 13, n.º 2 (25 de janeiro de 2023): 220. http://dx.doi.org/10.3390/cryst13020220.

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The cyclic plastic deformation of polycrystals leads to the inhomogeneous distribution of the cyclic plastic strain. The cyclic plastic strain is concentrated in thin bands, called persistent slip bands (PSBs). The dislocation structure of these bands generally differs from the matrix structure and is characterized by alternating dislocation-rich and dislocation-poor regions. The mechanisms of the dislocation motion in the PSBs and the formation of the point defects and their migration are quantitatively described. It is shown that, due to localized cyclic plastic straining in the PSBs, persistent slip markings (PSMs) are produced where the PSBs emerge on the surface. They typically consist of a central extrusion accompanied by one or two parallel intrusions. The deep intrusion is equivalent to the crack-like surface defect. The concentration of the cyclic strain in the tip of an intrusion leads to intragranular fatigue crack initiation. The mechanism of the early crack growth in the primary slip plane is proposed and discussed. Numerous PSMs are produced on the surface of the cyclically loaded materials. PSMs contribute to the formation of the surface relief, as well as the relief on the grain boundary. PSMs from one grain impinging the grain boundary are sufficient to create sharp relief on the grain boundary. Void-like defects weaken the grain boundary cohesion and extra material push both grains locally apart. The conditions necessary for the weakening of the grain boundary are enumerated and examples of grain boundary crack initiations are shown. The relevant parameters affecting grain boundary initiation are identified and discussed. The collected experimental evidence and analysis is mostly based on the papers published by the author and his colleagues in the Institute of Physics of Materials in Brno.

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Celik, Alptekin, Fabian Willems, Mustafa Tüzün, Svetlana Marinova, Johannes Heyn, Markus Fiedler e Christian Bonten. "Compounding, Rheology and Numerical Simulation of Highly Filled Graphite Compounds for Potential Fuel Cell Applications". Polymers 15, n.º 12 (6 de junho de 2023): 2589. http://dx.doi.org/10.3390/polym15122589.

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Highly filled plastics may offer a suitable solution within the production process for bipolar plates. However, the compounding of conductive additives and the homogeneous mixing of the plastic melt, as well as the accurate prediction of the material behavior, pose a major challenge for polymer engineers. To support the engineering design process of compounding by twin-screw extruders, this present study offers a method to evaluate the achievable mixing quality based on numerical flow simulations. For this purpose, graphite compounds with a filling content of up to 87 wt.-% were successfully produced and characterized rheologically. Based on a particle tracking method, improved element configurations were found for twin-screw compounding. Furthermore, a method to characterize the wall slip ratios of the compounded material system with different filler content is presented, since highly filled material systems often tend to wall slip during processing, which could have a very large influence on accurate prediction. Numerical simulations of the high capillary rheometer were conducted to predict the pressure loss in the capillary. The simulation results show a good agreement and were experimentally validated. In contrast to the expectation, higher filler grades showed only a lower wall slip than compounds with a low graphite content. Despite occurring wall slip effects, the developed flow simulation for the design of slit dies can provide a good prediction for both low and high filling ratios of the graphite compounds.

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Wang, Hongbo, Bowen Huang, Wangyu Hu e Jian Huang. "Studying Plastic Deformation Mechanism in β-Ti-Nb Alloys by Molecular Dynamic Simulations". Metals 14, n.º 3 (10 de março de 2024): 318. http://dx.doi.org/10.3390/met14030318.

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Using molecular dynamics (MD) simulations, the transition of the plastic deformation mechanism of Ti-Nb alloys during the tensile process was studied, and the effects of temperature, Nb composition, and strain rate on the deformation mechanism were also investigated. The results show that the deformation process of Ti-Nb alloys involves defect formation, followed by twinning and ω-phase transition, and ultimately, dislocation slip occurs. The <111>{112} slip makes the ω-phase easily overcome the transition energy barrier, inducing the phase transition in the twinning process. Increasing temperature will enhance the plasticity and reduce the strength of the material, while increasing Nb composition will have the opposite effect on the deformation. The simulations show a competition between twinning and dislocation slip mechanisms. With the increase in Nb content, the plastic deformation mechanism of the alloy will change from twinning to dislocation slip. In addition, the plastic strain range increases with the increase in the deformation rate in Ti-Nb alloys. At a higher strain rate, the alloy’s plastic strain range is affected by various deformation mechanisms, which significantly influence the plasticity of the material. The findings of this study provide further insights into the design of Ti-Nb-based alloys.

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Zeng, Bo, Hongwei Liu, Hongzhou Song, Zhe Zhao, Shaowei Fan, Li Jiang, Yuan Liu et al. "Design and slip prevention control of a multi-sensory anthropomorphic prosthetic hand". Industrial Robot: the international journal of robotics research and application 49, n.º 2 (30 de dezembro de 2021): 289–300. http://dx.doi.org/10.1108/ir-07-2021-0133.

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Purpose The purpose of this paper is to design a multi-sensory anthropomorphic prosthetic hand and a grasping controller that can detect the slip and automatically adjust the grasping force to prevent the slip. Design/methodology/approach To improve the dexterity, sensing, controllability and practicability of a prosthetic hand, a modular and multi-sensory prosthetic hand was presented. In addition, a slip prevention control based on the tactile feedback was proposed to improve the grasp stability. The proposed controller identifies slippages through detecting the high-frequency vibration signal at the sliding surface in real time and the discrete wavelet transform (DWT) was used to extract the eigenvalues to identify slippages. Once the slip is detected, a direct-feedback method of adjusting the grasp force related with the sliding times was used to prevent it. Furthermore, the stiffness of different objects was estimated and used to improve the grasp force control. The performances of the stiffness estimation, slip detection and slip control are experimentally evaluated. Findings It was found from the experiment of stiffness estimation that the accuracy rate of identification of the hard metal bottle could reach to 90%, while the accuracy rate of identification of the plastic bottles could reach to 80%. There was a small misjudgment rate in the identification of hard and soft plastic bottles. The stiffness of soft plastic bottles, hard plastic bottles and metal bottles were 0.64 N/mm, 1.36 N/mm and 32.55 N/mm, respectively. The results of slip detection and control show that the proposed prosthetic hand with a slip prevention controller can fast and effectively detect and prevent the slip for different disturbances, which has a certain application prospect. Practical implications Due to the small size, low weight, high integration and modularity, the prosthetic hand is easily applied to upper-limb amputees. Meanwhile, the method of the slip prevention control can be used for upper-limb amputees to complete more tasks stably in daily lives. Originality/value A multi-sensory anthropomorphic prosthetic hand is designed, and a method of stable grasps control based on slip detection by a tactile sensor on the fingertip is proposed. The method combines the stiffness estimation of the object and the real-time slip detection based on DWT with the design of the proportion differentiation robust controller based on a disturbance observer and the force controller to achieve slip prevention and stable grasps. It is verified effectively by the experiments and is easy to be applied to commercial prostheses.

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Carrez, Philippe, Patrick Cordier, David Mainprice e Andrea Tommasi. "Slip systems and plastic shear anisotropy in Mg2SiO4 ringwoodite: insights from numerical modelling". European Journal of Mineralogy 18, n.º 2 (11 de maio de 2006): 149–60. http://dx.doi.org/10.1127/0935-1221/2006/0018-0149.

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Wang, Jiwei, Bin Shao, Debin Shan, Bin Guo e Yingying Zong. "The Effect of Hydrogen on Plastic Anisotropy of Mg and α-Ti/Zr from First-Principles Calculations". Materials 16, n.º 8 (11 de abril de 2023): 3016. http://dx.doi.org/10.3390/ma16083016.

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Mg and α-Ti/Zr exhibit high plastic anisotropy. In this study, the ideal shear strength across the basal, prismatic, pyramidal I, and pyramidal II slip systems in Mg and α-Ti/Zr with and without hydrogen was computed. The findings indicate that hydrogen reduces the ideal shear strength of Mg across the basal and pyramidal II slip systems, as well as of α-Ti/Zr across all four systems. Moreover, the activation anisotropy of these slip systems was analyzed based on the dimensionless ideal shear strength. The results suggest that hydrogen increases the activation anisotropy of these slip systems in Mg, while decreasing it in α-Ti/Zr. Furthermore, the activation possibility of these slip systems in polycrystalline Mg and α-Ti/Zr subjected to uniaxial tension was analyzed by utilizing the ideal shear strength and Schmidt’s law. The results reveal that hydrogen increases the plastic anisotropy of Mg/α-Zr alloy while decreasing that of α-Ti alloy.

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Fu, Ge Yan, e Shi Hong Shi. "Mechanism Research of Low-Stress Threshold of Plastic Accumulation under Super-Low Repeated Impact Stress". Key Engineering Materials 464 (janeiro de 2011): 605–8. http://dx.doi.org/10.4028/www.scientific.net/kem.464.605.

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It is discovered that, if material has been applied with super-low impact stress that for certain times, macroscopic plastic deformation may be happen. The stress can be far below the static yield limit of material. The strain rate will decrease with impact times and distance from the surface. For exploring the micro-mechanism of the new deformation phenomena, the paper presents the theory of dislocation slip based on the principle of superposed dislocation vibration and the microscopic dislocation slip model under low-stress repeated impact. Analysis showed that the stress threshold is related to not only material damping, but also the frequency of repeated impact. Lower material damping and higher frequency of repeated impact are favorable to dislocation slip and, consequently, favorable to macroscopic plastic accumulation. Stress threshold being closely related to impact frequency is an important feature of repeated-impact plastic accumulation.

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Zeng, Xiang Guo, Qing Yuan Wang, Jing Hong Fan, Zhan Hua Gao e Xiang He Peng. "A Cyclic Stress-Strain Constitutive Model for Polycrystalline Magnesium Alloy and its Application". Materials Science Forum 546-549 (maio de 2007): 81–88. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.81.

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The stress-strain behavior of cast magnesium alloy (AM60) was investigated by strain-controlled cyclic testing carried out on MTS. In order to describe the cyclic stress and strain properties of AM60 by means of the energy storing characteristics of microstructure during irreversible deformation, a plastic constitutive model with no yielding surface was developed for single crystal by adopting a spring-dashpot mechanical system. Plastic dashpots reflecting the material transient response were introduced to describe the plasticity of slip systems. By utilizing the KBW self-consistent theory, a polycrystalline plastic constitutive model for Magnesium alloy was formed. The numerical analysis in the corresponding algorithm is greatly simplified as no process of searching for the activation of the slip systems and slip directions is required. The cyclic stress-strain behavior, based on this model, is discussed. The simulation results show good agreement with the experimental data for AM60.

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Alharbi, Hamad F., Monis Luqman, Ehab El-Danaf e Nabeel H. Alharthi. "Experimental and Numerical Study of Texture Evolution and Anisotropic Plastic Deformation of Pure Magnesium under Various Strain Paths". Advances in Materials Science and Engineering 2018 (2018): 1–12. http://dx.doi.org/10.1155/2018/2867281.

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The deformation behavior and texture evolution of pure magnesium were investigated during plane strain compression, simple compression, and uniaxial tension at room temperature. The distinctive stages in the measured anisotropic stress-strain responses and numerically computed strain-hardening rates were correlated with texture and deformation mechanisms. More specifically, in plane strain compression and simple compression, the onset of tensile twins and the accompanying texture-hardening effect were associated with the initial high strain-hardening rates observed in specimens loaded in directions perpendicular to the crystallographic c-axis in most of the grains. The subsequent drop in strain-hardening rates in these samples was correlated with the exhaustion of tensile twins and the activation of pyramidal <c+a> slip systems. The falling strain-hardening rates were observed in simple compression and plane strain compression with loading directions parallel to the c-axis where the second pyramidal <c+a> slip systems were the only slip families that can accommodate deformation. For uniaxial tension with the basal plane parallel to the tensile axis, the prismatic <a> and second pyramidal <c+a> slips are the main deformation mechanisms. The predicted relative slip and twin activities from the crystal plasticity simulations clearly showed the effect of texture on the type of activated deformation mechanisms.

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Jang, Min Gyu, Chul Hee Lee e Seung Bok Choi. "Stick-Slip Compensation of Micro-Positioning Using Elastic-Plastic Static Friction Model". Advanced Materials Research 47-50 (junho de 2008): 246–49. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.246.

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In this paper, a stick-slip compensation for the micro-positioning is presented using the statistical rough surface contact model. As for the micro-positioning structure, PZT (lead(Pb) zirconia(Zr) Titanate(Ti)) actuator is used to drive the load for precise positioning with its high resolution incorporating with the PID (Proportional Integral Derivative) control algorithm. Since the stick-slip characteristics for the micro structures are highly nonlinear and complicated, it is necessary to incorporate more detailed stick-slip model for the applications involving the high precision motion control. Thus, the elastic-plastic static friction model is used for the stick-slip compensation considering the elastic-plastic asperity contact in the rough surfaces statistically. Mathematical model of the system for the positioning apparatus was derived from the dynamic behaviors of structural parts. Since the conventional piezoelectric actuator generates the short stroke, a bridge-type flexural hinge mechanism is introduced to amplify the linear motion range. Using the proposed smart structure, simulations under the representative positioning motion were conducted to demonstrate the micro-positioning under the stick-slip friction.

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Abe, Takeji. "On the Relation between R-Value of a Grain and the Operating Slip Systems of the Grain". Key Engineering Materials 626 (agosto de 2014): 566–69. http://dx.doi.org/10.4028/www.scientific.net/kem.626.566.

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The r-value is defined as the ratio of the width strain to the thickness strain under uniaxial tensile loading. The r-value can be defined for each grain in polycrystalline metal during plastic deformation. It was pointed out that r-value of a grain affects the surface roughening of polycrystalline metal, and hence also affects the formability of thin sheet metal. On the other hand, it was shown that by using a rate-type constitutive relation for crystal slips the effect of the number of active slip systems on the yield curves is clarified. In the present paper, the relation between r-value of a grain and its operating slip systems in polycrystalline metals is studied.

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Lance, Gary L., e S. Nemat-Nasser. "Slip-induced plastic flow of geomaterials and crystals". Mechanics of Materials 5, n.º 1 (março de 1986): 1–11. http://dx.doi.org/10.1016/0167-6636(86)90011-6.

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Lance, Gary L., e S. Nemat-Nasser. "Slip-induced plastic flow of geomaterials and crystals". Mechanics of Materials 6, n.º 2 (junho de 1987): 175. http://dx.doi.org/10.1016/0167-6636(87)90007-x.

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Brown, Donald W., Sean R. Agnew, S. P. Abeln, W. R. Blumenthal, Mark A. M. Bourke, M. C. Mataya, Carlos Tomé e Sven C. Vogel. "The Role of Texture, Temperature and Strain Rate in the Activity of Deformation Twinning". Materials Science Forum 495-497 (setembro de 2005): 1037–42. http://dx.doi.org/10.4028/www.scientific.net/msf.495-497.1037.

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Plastic deformation in cubic metals is relatively simple due to the high crystallographic symmetry of the underlying structure. Typically, one unique slip mode can provide arbitrary deformation. This is not true in lower symmetry hexagonal metals, where prismatic and basal slip (the usual favored modes) are insufficient to provide arbitrary deformation. Often, either pyramidal slip and/or deformation twinning must be activated to accommodate imposed plastic deformation. The varied difficulty of activating each of these deformation mechanisms results in a highly anisotropic yield surface and subsequent mechanical properties. Further, the relative activity of each deformation mode may be manipulated through control of the initial crystallographic texture, opening new opportunities for the optimization of mechanical properties for a given application.

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A. Shubbar, Sawsan D., e Aqeel S. Al-Shadeedi. "UTILIZATION OF WASTE PLASTIC BOTTLES AS FINE AGGREGATE IN CONCRETE". Kufa Journal of Engineering 8, n.º 2 (17 de julho de 2017): 132–46. http://dx.doi.org/10.30572/2018/kje/821171.

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As human communities grow larger and larger, the problem of waste management becomes one of urgent need that should be solved. Recycling and reusing of the waste materials is an efficient measure in management of the waste materials, which in addition to preventing the pollution, it conserves natural resources. Plastic bottles made of polyethylene terephthalate (PET), constitutes a major fraction of household wastes. They are classified as non- biodegradable waste materials which are harmful for public health. So making use of PET in concrete production can be useful method to get rid of plastics solid waste damage on environment. In this research, effect of using waste PET that was converted to granules in concrete has been studied experimentally. Different proportion of sand ranging from 1% to 8%, were replaced by granulated plastic. The resulting concrete was compared with normal concrete without any addition of granulated plastic. Then the specimen were tested at 7 and 28 days after curing, and some engineering properties of the mixtures including slump test, fresh and dry density, compressive, and slip strength have been investigated. Analyzing experimental results of this work indicated that optimum dosage of waste bottles replacement is 2% as fine aggregate- substitution aggregate to get maximum compressive strength and slip strength.

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Eterashvili, Tamaz, Temur Dzigrashvili e M. Vardosanidze. "SEM Study of the Influence of Microstructure on Low Cycle Fatigue Crack Growth in Martensitic Steel I". Key Engineering Materials 774 (agosto de 2018): 96–100. http://dx.doi.org/10.4028/www.scientific.net/kem.774.96.

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Distribution of fatigue cracks in chromium martensitic steel after low cycle fatigue (LCF) tests at room temperature has been studied using SEM, and the experimental evidences of localized plastic flow (LPF) are presented. The influence of the location of LPF and the microstructure elements on the trajectory and growth of microcracks is also considered. The dimensions of plastic zones ahead of macrocrack tip as well as at its edges were measured in the process of crack propagation inside of the sample. The processes occurring in plastic zone, particularly ahead of macrocrack tip, were analyzed. Distribution, orientation and the reasons of slip bands’ formation as well as the microstructure elements at which they were nucleated have been studied. The impact of the slip bands’ orientation on the process of macrocrack growth was also analyzed. In addition the interactions of a crack with the boundaries of former austenite grains, martensitic packets, martensitic laths, slip bands and precipitates have been discussed.

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Tawfik, M. S., e T. D. O’Rourke. "Load-Carrying Capacity of Welded Slip Joints". Journal of Pressure Vessel Technology 107, n.º 1 (1 de fevereiro de 1985): 36–43. http://dx.doi.org/10.1115/1.3264401.

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Welded slip joints, which are used in many high-pressure water transmission pipelines, are vulnerable during earthquakes to axial compressive loads generated by ground movements. This paper analyzes two failure modes associated with: 1) yielding in the vicinity of welded connections, and 2) plastic flow in the curvilinear, belled ends of the joints. The analyses indicate that the axial load causing plastic deformation is from three to five times smaller than that causing yield in straight sections of pipe. Typical slip-joint dimensions are studied, and recommendations are made for improving the axial load-carrying capacity by 50 to 100 percent.

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