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Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 7 febbraio 2022

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1

Chukkan, Jazeel R., Guiyi Wu, Michael E. Fitzpatrick, Elvin Eren, Xiang Zhang e Joe Kelleher. "Residual stress redistribution during elastic shake down in welded plates". MATEC Web of Conferences 165 (2018): 21004. http://dx.doi.org/10.1051/matecconf/201816521004.

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Residual stresses are a consequence of welding in various structures such as ships and offshore structures. Residual stresses can be relaxed or redistributed according to the load levels during operation. The elastic shakedown phenomenon can be considered as one of the reasons for this change. This paper studies the relaxation/redistribution of weld residual stress during different levels of shakedown in a butt-welded plate chosen according to ship design and welding procedures. Welding was performed on DH36, a ship structural steel. Neutron diffraction was used to measure residual stresses in these plates in the as-welded state and after different levels of shakedown. A mixed hardening model in line with the Chaboche model is determined for both weld and base material. A numerical model is developed to estimate the shakedown limit on butt-welded plate. Further, the redistribution of residual stress in a numerical weld model according to the different levels of shakedown limit is studied. Based on the shakedown limit of the butt-welded plate, a shakedown region is determined, where the structure will undergo elastic shakedown in the presence of an existing residual stress field if the maximum stress on the load section after a few initial cycles is in the shakedown region.

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2

Wang, Kangyu, Yan Zhuang e Hanlong Liu. "Shakedown analysis for the evaluation of strength and bearing capacity of multilayered railway structures". Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 232, n. 9 (29 marzo 2018): 2324–35. http://dx.doi.org/10.1177/0954409718766952.

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Shakedown analysis is a robust approach for solving the strength problem of a structure under cyclic or repeated loading, e.g. railway structures subject to rolling and sliding traffic loads. Owing to the traffic loads, which are higher than the “shakedown limit”, railway structures may fail due to the excessive permanent deformation. This paper develops the analytical shakedown solutions based on Melan’s shakedown theorem, which is then applied for the evaluation of the strength and bearing capacity of multilayered railway structures. The shakedown solutions utilize the elastic stress fields obtained from the fully three-dimensional finite/infinite model, and calculate the shakedown multiplier for each layer of railway structures by means of a self-equilibrated critical residual stress field. The shakedown limits are then determined as the minimum shakedown multiplier among all layers. Parametric studies are also conducted, which indicate how the frictional coefficient, strength and stiffness of the materials, and the thickness ratio of ballast to subballast influence the shakedown limit and the stability condition of railway structures. The critical points of shakedown occur at the rail for low values of rail’s yield stress and large frictional coefficient, while they occur at the ballast layer when the frictional coefficient is relatively small. The shakedown limits are found to decrease with the increase in the strength and thickness of the ballast for a relatively small frictional coefficient. For the engineering design, there is an optimum combination of material properties and layer thickness, which provides the maximum bearing capacity of the railway structure based on this research. The results obtained from this study can provide a useful reference for the engineering design of railway structures.

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3

Abdalla, Hany F., Mohammad M. Megahed e Maher Y. A. Younan. "Determination of Shakedown Limit Load for a 90-Degree Pipe Bend Using a Simplified Technique". Journal of Pressure Vessel Technology 128, n. 4 (9 febbraio 2006): 618–24. http://dx.doi.org/10.1115/1.2349575.

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In this paper a simplified technique is presented to determine the shakedown limit load of a 90-degree pipe bend subjected to constant internal pressure and cyclic in-plane closing bending moment using the finite element method. The simplified technique determines the shakedown limit load without performing time consuming full elastic-plastic cyclic loading simulations or conventional iterative elastic techniques. Instead, the shakedown limit load is determined by performing two finite element analyses namely; an elastic analysis and an elastic-plastic analysis. By extracting the results of the two analyses, the shakedown limit load is determined through the calculation of the residual stresses developed in the pipe bend. In order to gain confidence in the simplified technique, the output shakedown limit moments are used to perform full elastic-plastic cyclic loading simulations to check for shakedown behavior of the pipe bend. The shakedown limit moments output by the simplified technique are used to generate the shakedown diagram of the pipe bend for a range of constant internal pressure magnitudes. The maximum moment carrying capacity (limit moment) the pipe bend can withstand and the elastic limit are also determined and imposed on the shakedown diagram of the pipe bend. In order to get acquainted with the simplified technique, it is applied beforehand to a bench mark shakedown problem namely, the Bree cylinder (Bree, J., 1967, J. Strain Anal., 3, pp. 226–238) problem. The Bree cylinder is subjected to constant internal pressure and cyclic high heat fluxes across its wall. The results of the simplified technique showed very good correlation with the analytically determined Bree diagram of the cylinder.

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4

Hamilton, R., J. T. Boyle, J. Shi e D. Mackenzie. "A Simple Upper-Bound Method for Calculating Approximate Shakedown Loads". Journal of Pressure Vessel Technology 120, n. 2 (1 maggio 1998): 195–99. http://dx.doi.org/10.1115/1.2842240.

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A simple approach for calculating upper-bound shakedown loads is described. The method is based on a series of iterative elastic finite element analyses (the elastic compensation procedure) applied to Koiter’s upper-bound shakedown theorem. The method is demonstrated for a typical pressure vessel application; an axisymmetric nozzle in a spherical shell. Several geometrical configurations are investigated. The calculated upper-bound shakedown loads are compared with lower-bound results obtained by the authors, simple shakedown criteria, and various results given in the literature.

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5

Jappy, Alan, Donald Mackenzie e Hao Feng Chen. "A Multi-Surface Plasticity Method for Lower Bound Shakedown Load". Key Engineering Materials 795 (marzo 2019): 458–65. http://dx.doi.org/10.4028/www.scientific.net/kem.795.458.

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A new direct method for calculation of lower bound shakedown limits based on Melan’s theorem and a novel, non-smooth multi-surface plasticity model is proposed and implemented in a Finite Element environment. The load history is defined by a finite number of extreme points defining the load-envelope of a periodic load set. The shakedown problem is stated as a plasticity problem in terms of a finite number of independent yield conditions, solved for a residual stress field that satisfies a piecewise, non-smooth yield surface defined by the intersection of multiple yield surfaces. The implemented Finite Element procedure is applied to two shakedown problems and the results compared with lower and upper bound elastic shakedown solutions given by the Linear Matching Method, LMM. The example analyses show that the proposed Elastic-Shakedown Multi Surface Plasticity (EMSP) method defines robust lower bound shakedown limits between the LMM lower and upper bound limits, close to the LMM upper bound.

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6

Shiau, S. H., e H. S. Yu. "Load and Displacement Prediction for Shakedown Analysis of Layered Pavements". Transportation Research Record: Journal of the Transportation Research Board 1730, n. 1 (gennaio 2000): 117–24. http://dx.doi.org/10.3141/1730-14.

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A complete shakedown assessment of pavement behavior under repeated loading requires a shakedown load analysis as well as a displacement evaluation. Both load and displacement bounding calculations at shakedown are presented, and the pavement subjected to repeated loading is analyzed as a plane strain problem. The proposed shakedown load formulation is verified by using numerical results for a homogeneous isotropic half space. To illustrate the relevance of the numerical formulations, the numerically determined residual stresses are compared with available experimental data. The variation of shakedown loads with different material properties for two-layered pavements is investigated in detail. The results of permanent displacement bounds are presented and compared with the displacement finite element calculation. Simple design charts for the layered pavements are presented.

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7

Shiau, Jim S. "A Shakedown Limit under Hertz Contact Pressure". Advanced Materials Research 291-294 (luglio 2011): 1506–10. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1506.

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In his "Contact Mechanics" book, Professor K. L. Johnson described an analytical lower bound shakedown approach to predict the shakedown load limit under repeated Hertz moving surface loads. Based on Bleich-Melan shakedown theorem, this problem will be revisited in this paper using finite element techniques and mathematical programming.

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8

Abdalla, Hany F., Mohammad M. Megahed e Maher Y. A. Younan. "Shakedown Limits of a 90-Degree Pipe Bend Using Small and Large Displacement Formulations". Journal of Pressure Vessel Technology 129, n. 2 (17 settembre 2006): 287–95. http://dx.doi.org/10.1115/1.2716433.

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In this paper the shakedown limit load is determined for a long radius 90-deg pipe bend using two different techniques. The first technique is a simplified technique which utilizes small displacement formulation and elastic–perfectly plastic material model. The second technique is an iterative based technique which uses the same elastic–perfectly plastic material model, but incorporates large displacement effects accounting for geometric nonlinearity. Both techniques use the finite element method for analysis. The pipe bend is subjected to constant internal pressure magnitudes and cyclic bending moments. The cyclic bending loading includes three different loading patterns, namely, in-plane closing, in-plane opening, and out-of-plane bending. The simplified technique determines the shakedown limit load (moment) without the need to perform full cyclic loading simulations or conventional iterative elastic techniques. Instead, the shakedown limit moment is determined by performing two analyses, namely, an elastic analysis and an elastic–plastic analysis. By extracting the results of the two analyses, the shakedown limit moment is determined through the calculation of the residual stresses developed in the pipe bend. The iterative large displacement technique determines the shakedown limit moment in an iterative manner by performing a series of full elastic–plastic cyclic loading simulations. The shakedown limit moment output by the simplified technique (small displacement) is used by the iterative large displacement technique as an initial iterative value. The iterations proceed until an applied moment guarantees a structure developed residual stress, at load removal, equal to or slightly less than the material yield strength. The shakedown limit moments output by both techniques are used to generate shakedown diagrams of the pipe bend for a spectrum of constant internal pressure magnitudes for the three loading patterns stated earlier. The maximum moment carrying capacity (limit moment) the pipe bend can withstand and the elastic limit are also determined and imposed on the shakedown diagram of the pipe bend. Comparison between the shakedown diagrams generated by the two techniques, for the three loading patterns, is presented.

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9

Yu, H. S. "Three-dimensional analytical solutions for shakedown of cohesive-frictional materials under moving surface loads". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 461, n. 2059 (23 maggio 2005): 1951–64. http://dx.doi.org/10.1098/rspa.2005.1445.

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This paper develops analytical solutions for shakedown limits of a cohesive-frictional half-space under a three-dimensional moving surface load. Melan's lower-bound shakedown theorem has been adopted as the theoretical basis for deriving shakedown limits. Rigorous lower-bound solutions are obtained for shakedown limits by establishing a self-equilibrated residual stress field that, together with the applied elastic stress fields, lies within the Mohr–Coulomb yield criterion throughout the half-space. By searching through the half-space, this study shows that the most critical location for satisfying the yield condition lies on the central plane. The analytical solutions derived in the paper can be used to benchmark numerical shakedown results, as well as to serve as a theoretical basis for the development of an analytical design method for pavements under moving traffic loads.

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10

Zhang, Yang, Wei Zhang, Yi He Qi e Jian Wang. "Element Bearing Ratio Based Shakedown Analysis for Branch Pipe". Advanced Materials Research 842 (novembre 2013): 586–90. http://dx.doi.org/10.4028/www.scientific.net/amr.842.586.

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Shakedown analysis is important for branch pipe because it is often damaged under various water pressure. In this paper, an element bearing ratio (EBR) based shakedown analysis method is employed for shakedown analysis of branch pipe. The EBR is used to replace the stress term in classical optimization problem in the procedure, and series of residual EBR fields can be generated by the D-value of the elastic-plastic EBR fields and the elastic EBR fields at every incremental loading step. The shakedown load is determined by performing an incremental non-linear static analysis when the yield criterion is arrived either by the elastic-plastic EBR fields or residual EBR fields. By introducing the EBR, the proposed procedure can be easily used to shakedown analysis of branch pipe with multi-material and complicated configuration. Numerical examples validate the method and demonstrate its performance.

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11

Peng, Heng, e Ying Hua Liu. "Stress Compensation Method for Structural Shakedown Analysis". Key Engineering Materials 794 (febbraio 2019): 169–81. http://dx.doi.org/10.4028/www.scientific.net/kem.794.169.

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This paper presents a novel direct method called the stress compensation method (SCM) for structural shakedown analysis. Being different from the popular direct method of mathematical programming, the SCM just carries out some iterative calculations. Making full use of static shakedown theorem, the residual stress field is constructed via solving the modified global equilibrium equations. An effective and robust iteration control technique is adopted to generate a sequence of decreasing load multipliers. The numerical procedure is incorporated into the ABAQUS platform via some user subroutines. The shakedown problems for a cantilever beam, a symmetric continuous beam and a practical shell with nozzles are effectively solved and analyzed. These results are compared to the analytical solutions and those found in literatures. Both the incremental collapse mechanism and the alternating plasticity mechanism are revealed to determine the shakedown boundaries. Numerical examples show that the SCM is of numerical stability, good accuracy, high computational efficiency, and can effectively perform shakedown analysis of large-scale practical engineering structures.

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12

Yuan, Yuan, Kai Liu e Kun Shi. "Shakedown on Thermal Barrier Coating and Simply Analytic Model". Applied Mechanics and Materials 160 (marzo 2012): 200–205. http://dx.doi.org/10.4028/www.scientific.net/amm.160.200.

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A simply analytic model is developed base on wrinkle geometry model. The three concentric circles are adopted to represent top coat, oxide coat and bond coat of thermal barrier coating, and then shakedown analysis is established based on the model. A numerical model has been given base on wrinkle geometry model in a thermal barrier coating system, and the model on static shakedown analysis is developed by finite element method. Shakedown limit of thermal barrier coating is calculated for various undulation shape and thermal grown oxide. The simply analytic results and numerical results are approximate for undulation shape is not very irregular. The simply analytic model is convenient for calculating shakedown limit of thermal barrier coating.

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13

Muscat, Martin, e Donald Mackenzie. "Elastic-Shakedown Analysis of Axisymmetric Nozzles". Journal of Pressure Vessel Technology 125, n. 4 (1 novembre 2003): 365–70. http://dx.doi.org/10.1115/1.1613301.

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An investigation of the shakedown behavior of axisymmetric nozzles under internal pressure is presented. The analysis is based on elastic-plastic finite element analysis and Melan’s lower bound shakedown theorem. Calculated shakedown pressures are compared with values from the literature and with the ASME Boiler and Pressure Vessel Code Section VIII Division 2 primary plus secondary stress limits. Results obtained by the lower bound method are also verified by cyclic elastic-plastic finite element analysis.

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14

Arakawa, Jinta, Tatsuya Hanaki, Yoshiichirou Hayashi, Hiroyuki Akebono e Atsushi Sugeta. "Effect of surface compressive residual stress introduced by surface treatment on fatigue properties of metallic material". MATEC Web of Conferences 165 (2018): 18006. http://dx.doi.org/10.1051/matecconf/201816518006.

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This study considers shakedown in evaluating the fatigue limit of metals with compressive residual stress at the surface. We begin by applying tension-compression fatigue tests to ASTM CA6NM under conditions of controlled load and displacement to obtain fatigue limit diagram in compressive mean stress. The results imply that shakedown occurs under the condition of controlled displacement, therefore, shakedown should be considered when evaluating the fatigue limit of metals with compressive residual stress at the surface.

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15

Wang, Li Ping, Ying Qiang Xu e Yuan Yuan. "The Analysis of Gear Contact under Cyclical Load". Applied Mechanics and Materials 86 (agosto 2011): 809–12. http://dx.doi.org/10.4028/www.scientific.net/amm.86.809.

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Shakedown analysis of gear contact is very important. Local coordinates are constructed on different meshing points because curvature of gear profile is not constant and then distributions of residual stresses and strains are given. Upper and lower bounds for the shakedown limits have been obtained. The steady-state residual stresses of gear under repeat meshing are calculated and relations between shakedown limits and frictional coefficient/meshing position are given. The results are useful information for the strength design of gear.

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16

Jiang, W. "The Elastic-Plastic Analysis of Tubes—III: Shakedown Analysis". Journal of Pressure Vessel Technology 114, n. 2 (1 maggio 1992): 229–35. http://dx.doi.org/10.1115/1.2929034.

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This paper presents an investigation of the shakedown behavior of tubes subjected to cyclic centrifugal force and temperature, and sustained internal and external pressures. It is found that the steady states can always be attained as a result of the kinematic hardening. Then, when shakedown occurs, the stresses and strains will cycle between the cooling state and the heating state. The steady-state solutions for the cases of elastic shakedown and reversed plasticity are discussed and given in this paper.

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17

Wang, Xian Feng, Feng Xing, Ming De Xue e Bing Ye Xu. "Shakedown Analysis of Cylindrical Shells Containing Part-Through External Pit". Advanced Materials Research 156-157 (ottobre 2010): 1680–83. http://dx.doi.org/10.4028/www.scientific.net/amr.156-157.1680.

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A lower-bound shakedown analysis for cylindrical shells containing defects is performed based on the static shakedown theorem in a finite element computational form. To overcome the numerical difficulties, the pseudo-temperature field is applied to a structure and the resulting thermo-elastic stress is considered as the self-equilibrium residual-stress field. The pseudo temperature is assumed as a harmonic function satisfying the uniqueness theorem, therefore the nodal temperature matrix of the whole structure can be expressed by the boundary nodal temperature matrix. The nonlinear yield condition is piece-wise linearized so that the shakedown analysis is transformed into a linear programming problem in which the strategic variable is boundary nodal temperature and objective variable is the loading multiplier. The relations of limit and shakedown pressures to geometric parameters of various defects are presented.

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18

Boulbibane, Mostapha, e Abdullahi Ali Mohamed. "Design of Unbound Pavement Layer Materials Based Upon the Shakedown Concept". Applied Mechanics and Materials 174-177 (maggio 2012): 726–32. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.726.

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This study aims to introduce an alternative design method for unbound pavement layer materials based upon shakedown theory. The kinematic shakedown theorem that describes the ultimate response of an elastic/plastic structure to cyclic loads is used to predict whether stable behaviour in the unbound granular materials layer occurs or excessive rutting will develop. This method seeks the mechanism, from within a class of mechanisms that minimises the shakedown limit load for pavements consisting of layers of Mohr-Coulomb material obeying the associated flow rule. The basic concepts are outlined together with the most recent calculations of the critical design shakedown load. The influence of the of design parameters such as, the strength, stiffness and depth of the base-course material as well as the consequences of load distribution are discussed.

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19

Reinhardt, W., R. Kizhatil e G. H. McClellan. "Analysis of a Tubesheet Undergoing Rapid Transient Thermal Loading". Journal of Pressure Vessel Technology 122, n. 4 (7 marzo 2000): 476–81. http://dx.doi.org/10.1115/1.1286018.

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Some Class I CANDU heat exchanger tubesheets experience very high in-plane thermal gradients under Level A/B transients. If the thermal stresses exceed the ratcheting limit of the ASME Boiler and Pressure Vessel Code, shakedown has to be demonstrated by an elastic-plastic analysis. The choice of the plasticity model and its parameters must ensure that shakedown is predicted only if it occurs in reality. Differences to uniaxial modeling are discussed, and a conservative way of predicting shakedown is presented. The perforated region of the tubesheet is replaced by an equivalent solid plate with anisotropic yield properties (Hill’s yield criterion). A lower-bound shakedown limit for this material is derived. An example analysis is presented that has been performed using a commercial finite element code. [S0094-9930(00)00303-6]

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20

Polizzotto, Castrenze. "On the Conditions to Prevent Plastic Shakedown of Structures: Part II—The Plastic Shakedown Limit Load". Journal of Applied Mechanics 60, n. 1 (1 marzo 1993): 20–25. http://dx.doi.org/10.1115/1.2900750.

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Following the results of a companion paper, the concept of plastic shakedown limit load is introduced for an elastic-perfectly plastic material structure subjected to combined cyclic (mechanical and/or kinematical) loads and steady (mechanical) load. Static and kinematic approaches are available for the computation of this load, in perfect analogy with the classic (elastic) shakedown limit load. The plastic shakedown limit state of the structure being in an impending alternating plasticity collapse is studied and a number of interesting features of it are pointed out.

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21

Weichert, D., A. Hachemi e F. Schwabe. "Shakedown analysis of composites". Mechanics Research Communications 26, n. 3 (maggio 1999): 309–18. http://dx.doi.org/10.1016/s0093-6413(99)00029-4.

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22

Zouain, Nestor, e José Luı́s Silveira. "Bounds to shakedown loads". International Journal of Solids and Structures 38, n. 10-13 (marzo 2001): 2249–66. http://dx.doi.org/10.1016/s0020-7683(00)00165-7.

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23

Boulbibane, M., I. F. Collins, A. R. S. Ponter e D. Weichert. "Shakedown of Unbound Pavements". Road Materials and Pavement Design 6, n. 1 (gennaio 2005): 81–96. http://dx.doi.org/10.1080/14680629.2005.9690000.

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24

Klebanov, J. M., e J. T. Boyle. "Shakedown of creeping structures". International Journal of Solids and Structures 35, n. 23 (agosto 1998): 3121–33. http://dx.doi.org/10.1016/s0020-7683(97)00359-4.

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25

Stoffel, M., R. Schmidt e D. Weichert. "Pseudo-Shakedown viskoplastischer Flächentragwerke". ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik 80, S2 (2000): 303–4. http://dx.doi.org/10.1002/zamm.20000801423.

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26

Zhang, J., W. Q. Shen, A. Oueslati e G. De Saxcé. "Shakedown of porous materials". International Journal of Plasticity 95 (agosto 2017): 123–41. http://dx.doi.org/10.1016/j.ijplas.2017.04.003.

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27

Alwis, W. A. M., e P. Grundy. "Shakedown analysis of plates". International Journal of Mechanical Sciences 27, n. 1-2 (gennaio 1985): 71–82. http://dx.doi.org/10.1016/0020-7403(85)90067-0.

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LIEPA, Liudas, Gediminas BLAŽEVIČIUS, Dovilė MERKEVIČIŪTĖ e Juozas ATKOČIŪNAS. "STRUCTURAL SHAKEDOWN: A NEW METHODOLOGY FOR ESTIMATING THE RESIDUAL DISPLACEMENTS". JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 22, n. 8 (25 novembre 2016): 1055–65. http://dx.doi.org/10.3846/13923730.2016.1217924.

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Abstract (sommario):

A vector of residual forces of the ideally elastic-plastic structure at shakedown is obtained by solving the static analysis problem. A unique distribution of the residual forces is determined if the analysis is based on the minimum complementary deformation energy principle. However, the residual displacements developing in the shakedown process of ideally elastic-plastic structures under variable repeated loads can vary non-monotonically. Nevertheless mathematical models for the optimization problems of steel structures at shakedown must include the conditions for strength (safety) and stiffness (serviceability). Residual displacements determined by the plastic deformations are included in the stiffness conditions; therefore to improve the optimal solution it is necessary to determine upper and lower bounds of the residual displacement variations. This paper describes an improved methodology for estimating the variation bounds of the residual displacements at shakedown.

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29

Churchman, C. M., A. M. Korsunsky e D. A. Hills. "The Application of Plasticity Principles to Friction". Journal of Strain Analysis for Engineering Design 41, n. 4 (1 maggio 2006): 323–28. http://dx.doi.org/10.1243/03093247jsa96.

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This paper presents a compelling analogy between the ideas of plastic shakedown and frictional shakedown. It introduces the frictional equivalent of the Bree diagram and classifies the different possible responses of a simple system to typical periodic or cyclic loading.

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Jia, Xiao Liang, Yi Liang Zhang, Jing Wang e Chun Bo Wang. "True Stress and Shakedown Analysis of Pressure Vessel which under Cyclic Loading to Plastic Deformation". Applied Mechanics and Materials 590 (giugno 2014): 8–12. http://dx.doi.org/10.4028/www.scientific.net/amm.590.8.

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The aim of this study is to discuss the plastic shakedown and true stress of the cyclically loaded pressure vessel. A thin-walled cylinder pressure vessel is made according to actual working state and a water pressure test system is built. The vessel is loaded to different strain levels of plastic deformation first. Then it is loaded cyclically to shakedown state. The relationship between plastic strain and shakedown range is given based on numerous experiments. The constitutive model of the true stress-true strain of the vessel is obtained. The experimental results show that the ratcheting obviously occurred when the vessel is cyclically loaded to plastic deformation. The true stress-strain constitutive model which is presented in this paper can show appropriately the constitutive relation of the vessel when it is under multi-axial stress state. The application of uniaxial shakedown constitutive model has been demonstrated in this study.

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Jarmolajeva, Ela, e Juozas Atkočiūnas. "SHAKEDOWN LOADING OPTIMIZATION UNDER CONSTRAINED RESIDUAL DISPLACEMENTS—FORMULATION AND SOLUTION FOR CIRCULAR PLATES". JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 8, n. 1 (31 marzo 2002): 54–67. http://dx.doi.org/10.3846/13923730.2002.10531250.

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The adapted plate load optimization problem is formulated applying the non-linear mathematical programming methods. The load variation bounds satisfying the optimality criterion in concert with the strength and stiffness requirements are to be identified. The stiffness constraints are realized via residual displacements. The dual mathematical programming problems cannot be applied directly when determining actual stress and strain fields of plate: the strained state depends upon the loading history. Thus the load optimization problem at shakedown is to be stated as a couple of problems solved in parallel: the shakedown state analysis problem and the verification of residual deflections bounds. The Rozen project gradient method is applied to solve the cyclically loaded non-linear shakedown plate stress and strain evaluation and that of the load optimization problems. The mechanical interpretation of Rozen optimality criterions allows to simplify the shakedown plate optimization mathematical model and solution algorithm formulations.

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Aleksandrov, Anatoly, Gennadiy Dolgih, Vitaly Ignatov e Aleksander Kalinin. "The application of the principles of the theory of shakedown to the calculation of pavement layers of granular materials in shear". MATEC Web of Conferences 239 (2018): 05019. http://dx.doi.org/10.1051/matecconf/201823905019.

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In the report ways of application of the theory of shakedown of material to calculation of coverings and the bases of pavements from the granulated materials are considered. The basic limits of shakedown are given, which include the limits of resilient, elastic and plastic shakedown. The results of three-axis tests are given, on the basis of which the character of accumulation of residual deformation is divided into damped, steady and progressive. These data allow to predict the nature of deformation and provide damped deformation of the granular material, limiting the stress at the most dangerous point.

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33

Boulbibane, M., I. F. Collins, D. Weichert e L. Raad. "Shakedown analysis of anisotropic asphalt concrete pavements with clay subgrade". Canadian Geotechnical Journal 37, n. 4 (1 agosto 2000): 882–89. http://dx.doi.org/10.1139/t00-007.

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The essence of a shakedown analysis is to determine the critical shakedown load for a given pavement. Pavements operating above this load are predicted to exhibit increased accumulation of plastic strains under long-term repeated loading conditions that eventually lead to incremental collapse (e.g., deep ruts). Those pavements operating at loads below this critical level may exhibit some initial distress, but will eventually settle down to a steady state in which no further mechanical deterioration occurs. Conventional pavement design procedures assume that the pavement deteriorates indefinitely. However, there is now ample field evidence that this is not always true and that steady-state conditions are frequently achieved. The materials in the various layers of the pavement are modeled as elastic-plastic Mohr-Coulomb materials. Anisotropic strength effects are studied as well as the influences of variable temperature, stiffness, strength, and thickness of the asphalt concrete layer. A lower bound approach is used to provide safe estimates of the critical shakedown load.Key words: shakedown theory, multilayered pavements, anisotropy.

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34

Muscat, M., R. Hamilton e J. T. Boyle. "Shakedown analysis for complex loading using superposition". Journal of Strain Analysis for Engineering Design 37, n. 5 (1 luglio 2002): 399–412. http://dx.doi.org/10.1243/030932402760203865.

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Bounding techniques for calculating shakedown loads are of great importance as design criteria since these eliminate the need for performing full cyclic loading programs either numerically or experimentally. The classical Melan theorem provides a way to recognize whether or not elastic shakedown occurs under a specified loading. Polizzotto extended Melan's theorem to the case where a combination of steady and cyclic loads are acting on the structure. The purpose of this paper is to present a finite element method, based on Polizzotto's theorem, to estimate elastic shakedown for a structure subjected to loads resulting from a combination of steady and cyclic mechanical loads. This method, called non-linear superposition, is then applied to investigate the shakedown behaviour of a biaxially loaded square plate with a central hole. Results obtained for the plate with a hole problem are compared with those available in the literature and are verified by means of cyclic elastoplastic finite element analysis.

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35

Shen, Wei Qin, e Norman Jones. "The Pseudo-Shakedown of Beams and Plates When Subjected to Repeated Dynamic Loads". Journal of Applied Mechanics 59, n. 1 (1 marzo 1992): 168–75. http://dx.doi.org/10.1115/1.2899423.

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A conjecture is derived in this paper for the pseudo-shakedown phenomenon of beams and plates which strengthen with finite displacements when subjected to repeated dynamic transverse loads causing material plastic flow and permanent deflections. This behavior is illustrated for a fully clamped, rigid, perfectly plastic beam which is subjected to a repeatedly applied, rectangular-shaped pressure-time history at the midspan. It transpires that a curve divides the dynamic load magnitude-pulse duration time area into two regions where pseudo-shakedown may or may not occur. Another curve in the region where pseudo-shakedown does not occur identifies when the dynamic problem may be studied with a static analysis.

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36

Yazdani, Hosein, e Ali Nayebi. "Elastoplastic analysis of a thin-walled tube under cyclic bending and constant internal pressure: A simplified model". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, n. 4 (28 maggio 2014): 591–602. http://dx.doi.org/10.1177/0954406214538008.

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In this study, the elastoplastic analysis of thin-walled tubes under cyclic bending and internal pressure is presented. A simple method is presented and verified. In order to predict ratcheting or shakedown behavior in the cyclic loading, von-Mises yield criterion as the yield surface and Chaboche’s nonlinear kinematic hardening model are used. The stress–strain variation is obtained with the help of return mapping algorithm. The present solution is in good agreement with experimental results. Shakedown or ratcheting behavior of the tube under various combinations of applied constant internal pressure and cyclic curvature is considered, Bree’s interaction diagram is obtained and the boundary between shakedown and ratcheting zone is determined.

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37

Leonavičius, Mindaugas, e Marijonas Sušukšta. "SHAKEDOWN OF BOLTS WITH A ONE-SIDED PROPAGATING CRACK". JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 8, n. 2 (30 giugno 2002): 104–7. http://dx.doi.org/10.3846/13923730.2002.10531260.

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Cyclic strains of joints may cause formation of a crack or cracks in a bolt thus changing its loading conditions. After crack appearance in a bolt it can be used if its length does not exceed a critical one. Modification of the shakedown theorem—the method of additional load—was applied in the investigation. The results—the analytical expressions of shakedown conditions are in a sufficiently good agreement with those achieved by other methods. Differences occur due to failure to get an accurate analytic expression. Solution of the shakedown problem plays an essential role in determining the safety factor of bolts subjected to cyclic strains.

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38

Ghadimi, Behzad, Ainalem Nega e Hamid Nikraz. "Simulation of Shakedown Behavior in Pavement’s Granular Layer". International Journal of Engineering and Technology 7, n. 3 (giugno 2015): 198–203. http://dx.doi.org/10.7763/ijet.2015.v7.791.

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39

Zhang, Guichen, Hongtao Zhang, Heng Peng e Yinghua Liu. "Dynamical shakedown analysis of high-rise tower structure". Engineering Computations 38, n. 3 (4 febbraio 2021): 1432–51. http://dx.doi.org/10.1108/ec-07-2020-0368.

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Purpose High-rise tower structures supported by side frame structure and viscous damper in chemical industry can produce plasticity under dynamic loads, such as wind and earthquake, which will heavily influence the long-term safety operation. This paper aims to systematically study the optimization design of these structures by free vibration and dynamic shakedown analysis. Design/methodology/approach The transfer matrix method and Euler–Bernoulli beam vibration are used to study the free vibration characteristic of the simplified high-rise tower structure. Then the extended stress compensation method is used to construct the self-equilibrated stress by using the dynamic load vertexes and the lower bound dynamic shakedown analysis for the structure with viscous damper. Using the proposed method, comprehensive parametric studies and optimization are performed to examine the shakedown load of high-rise tower with various supported conditions. Findings The numerical results show that the supported frame stiffness, attached damper or spring parameters influence the free vibration and shakedown characters of high-rise tower very much. The dynamic shakedown load is lowered down quickly with external load frequency increasing to the fundamental natural frequency of the structure under spring supported condition, while changed little with the damping connection. The optimized location and parameter of support are obtained under dynamical excitations. Research limitations/implications In this study, the high-rise tower structure is simplified as a cantilever beam supported by a short cantilever beam and a damper under repeated dynamic load, and linear elasticity for solid is assumed for free vibration analysis. The current analysis does not account for effects such as large deformation, stochastic external load and nonlinear vibration conditions which will inevitably be encountered and affect the load capacity. Originality/value This study provides a comprehensive method for the dynamical optimization of high-rise tower structure by combining free vibration and shakedown analysis.

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40

Polizzotto, C. "A Study on Plastic Shakedown of Structures: Part I—Basic Properties". Journal of Applied Mechanics 60, n. 2 (1 giugno 1993): 318–23. http://dx.doi.org/10.1115/1.2900795.

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Abstract (sommario):

For a continuous elastic-perfectly plastic solid body subjected to a combination of cyclic (mechanical and/or kinematical) load and of a steady (mechanical) load such as to produce plastic shakedown (i.e., alternating plasticity), a number of characterizing properties are established and discussed. The conditions for the body’s transition from plastic shakedown to ratchetting are also addressed.

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41

Polizzotto, Castrenze. "A Study on Plastic Shakedown of Structures: Part II—Theorems". Journal of Applied Mechanics 60, n. 2 (1 giugno 1993): 324–30. http://dx.doi.org/10.1115/1.2900796.

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Abstract (sommario):

For a continuous elastic-perfectly plastic solid body subjected to a combination of cyclic (mechanical and/or kinematical) load and of a steady (mechanical) load, two theorems of plastic shakedown are presented, one stating a necessary condition, another stating a sufficient condition. The problem of the direct determination of the plastic shakedown boundary is also briefly addressed.

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42

Huang, Y. J., e E. Stein. "Shakedown of a CT specimen with St52 steel—experimental, analytical and numerical investigations". Journal of Strain Analysis for Engineering Design 30, n. 4 (1 ottobre 1995): 283–89. http://dx.doi.org/10.1243/03093247v304283.

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Abstract (sommario):

The paper deals with the shakedown behaviour of a CT (compact tension) specimen consisting of St52 steel under cyclical loading. Experiments have been carried out for determining the shakedown limit load. For comparison, the analytical and numerical methods are used to study the same problem. Satisfactory agreement has been achieved between the results from these different methods.

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43

Hawksbee, SJ, GJ Tucker e M. Burstow. "Use of shakedown maps to assess plastic flow in railway curves". Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 234, n. 4 (14 ottobre 2019): 417–25. http://dx.doi.org/10.1177/0954409719881518.

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Plastic deformation of rails can occur on tight curves, which can significantly reduce the rail life. This paper investigated the phenomena of gross plastic deformation, or plastic flow, using multibody vehicle–track interaction and simplified finite element analysis. The focus is on understanding the contact conditions on the low rail of curves and how these differ from those in shakedown maps. To this end, two trial sites are simulated using multibody vehicle–track software. The contact conditions are then compared against several criteria assumed in the derivation of the shakedown maps. A further assumption implicit in the shakedown maps is also investigated by a non-linear finite element analysis. In this case, a more realistic Chaboche material model is used as opposed to the simple linear elastic–perfectly plastic model in the shakedown theory. The results of the finite element analysis are combined with a bespoke indicator of plastic flow to assess the influence of distance to shakedown limits on the likely plastic flow. Finally, a simple interpolation scheme is used to map the finite element results back to the trial sites. The interpolated results for the sites are used to evaluate the influence of running speed and different levels of wheel profile wear. Results suggest that the bespoke indicator defined in this work can be used as an effective measure of plastic flow; this measure is then used to quantify the influence of cant excess on the rates of plastic flow.

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44

Mohamed, A. I., M. M. Megahed, L. S. Bayoumi e M. Y. A. Younan. "Applications of Iterative Elastic Techniques for Elastic-Plastic Analysis of Pressure Vessels". Journal of Pressure Vessel Technology 121, n. 1 (1 febbraio 1999): 24–29. http://dx.doi.org/10.1115/1.2883663.

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The paper presents an application of iterative elastic techniques for the determination of elasto-plastic stress-strain fields, limit and shakedown loads. The iterative elastic method relies on iterative modification of elastic modulus in regions at which elastically calculated effective stress exceeds material yield strength. The technique is applied first to thick spherical and cylindrical shells under combined pressure and thermal gradient. Results showed good correlation with analytical elasto-plastic solutions. The elastic compensation technique is then applied to predict elasto-plastic stresses and shakedown loads of thin spherical shell with cylindrical nozzle subjected to internal pressure or end-thrust loading. Predicted shakedown loads were found to be in good agreement with the well-known Leckie and Penny results adopted in pressure vessel codes.

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45

Uetani, K., e Y. Araki. "Steady-State Limit of Elastoplastic Trusses for the Plastic Shakedown Region". Journal of Applied Mechanics 67, n. 3 (21 aprile 1999): 581–89. http://dx.doi.org/10.1115/1.1285837.

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Abstract (sommario):

For elastoplastic trusses under quasi-static cyclic loading, a method is presented for finding the steady-state limit that bounds the plastic shakedown and ratchetting regions. In the plastic shakedown region, an assumption employed in the previous approaches for finding the steady-state limit can be invalid in many circumstances. Although strain reversals were assumed to occur only at load reversals, yielding of an element exhibiting plastic shakedown may cause strain reversals in other elements. This difficulty is overcome by relaxing this assumption so that the strain reversals due to yielding are taken into account. Numerical examples showed that the present method can find the steady-state limit even when strong effects of geometrical nonlinearity exist. [S0021-8936(00)01201-0]

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46

Williams, J. A., I. N. Dyson e A. Kapoor. "Repeated Loading, Residual Stresses, Shakedown, and Tribology". Journal of Materials Research 14, n. 4 (aprile 1999): 1548–59. http://dx.doi.org/10.1557/jmr.1999.0208.

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Abstract (sommario):

Protective residual stresses may be developed in the near surface layers of tribological contacts which enable loads sufficiently large to cause initial plastic deformation to be accommodated purely elastically in the longer term. This is the process of shakedown and, although the underlying principles can be demonstrated by reference to relatively simple stress systems, the situation is complex under a moving Hertzian pressure distribution. Bounding theorems can be used to generate appropriate load or shakedown limits not only for uniform half-spaces but also those with plastic and/or elastic properties which vary with depth. In this way, shakedown maps, which delineate the boundaries between potentially safe and unsafe operating conditions, can be generated for both hardened and coated surfaces.

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47

Polizzotto, Castrenze. "On the Conditions to Prevent Plastic Shakedown of Structures: Part I—Theory". Journal of Applied Mechanics 60, n. 1 (1 marzo 1993): 15–19. http://dx.doi.org/10.1115/1.2900739.

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Abstract (sommario):

For a structure of elastic perfectly plastic material subjected to a given cyclic (mechanical and/or kinematical) load and to a steady (mechanical) load, the conditions are established in which plastic shakedown cannot occur whatever the steady load, and thus the structure is safe against the alternating plasticity collapse. Static and kinematic theorems, analogous to those of classical shakedown theory, are presented.

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48

Wong, S. K., A. Kapoor e J. A. Williams. "Shakedown limits on coated surfaces". Thin Solid Films 292, n. 1-2 (gennaio 1997): 156–63. http://dx.doi.org/10.1016/s0040-6090(96)08938-9.

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49

McCARRON, KIM. "The shakedown on Parkinsonʼs disease". Nursing Made Incredibly Easy! 4, n. 6 (novembre 2006): 40–49. http://dx.doi.org/10.1097/00152258-200611000-00011.

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50

&NA;. "The shakedown on Parkinsonʼs disease". Nursing Made Incredibly Easy! 4, n. 6 (novembre 2006): 50. http://dx.doi.org/10.1097/00152258-200611000-00012.

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