A general theory of plastic deformation and instability in thin-walled tubes under combined loading

Abstract Due to demand of strong toughness of thin walled tube, and good secondary forming properties and high-precision dimension, New plastic forming method should be researched to achieve a complete filling, uniform deformation and microstructure evolution during forming process.To obtain the deformation mechanisms of a new composite extrusion for thin walled tube fabricated by tube corrugated equal channel angular extrusion has been researched which is shorten as “TC-ECAE” in this paper. Finite element DEFORMTM-3D software to investigate the plastic deformation behavior of magnesium billet during TC-ECAE process has been employed. Computed parameters including workpiece material characteristics and process conditions have been taken into consideration. The pridictions of strains distributions and damage distributions and effective stress distributions and flow velocities distributions and microstructures evolutions have been explored. The results proved that the TC-ECAE process is a forming method for magnesium alloy tube which is suitable for large scale industrial application. The TC-ECAE process would cause serve plastic deformation and improve the dynamic recrystallization of magnesium alloy during TC-ECAE process.

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Bending of Pretwisted Beams

Journal of Applied Mechanics ◽

10.1115/1.4011084 ◽

1955 ◽

Vol 22 (3) ◽

pp. 348-352

Author(s):

J. Zickel

Keyword(s):

General Theory ◽

Bending Stiffness ◽

Thin Strip ◽

Principal Directions ◽

Thin Walled ◽

Lateral Deflections

Abstract The general theory of pretwisted beams and columns is applied to the bending of an initially straight and uniformly pretwisted beam of doubly symmetric thin-walled section. Pretwisting brings planes of various bending stiffness into play with a resulting stiffness which in a sense averages the stiffness of the beam in its principal directions. It is shown that compared with bending of an untwisted beam in its most flexible direction a thin strip can have its deflection in the plane of bending reduced 72 per cent by an initial twist of 0.83π. Simultaneously, however, lateral deflections of almost equal magnitude are induced. For pretwists above 2π, the lateral deflections become practically negligible and the deflections in the plane of bending are still reduced as much as 44 per cent. With increasing initial twist, however, the pretwisted beam becomes more flexible, and for an initial twist of 6.5π it is as flexible as the untwisted beam in its most flexible direction. Beams of equal flexibility in all directions simply become more flexible with initial twist, a fact which corresponds to the observations made by Den Hartog in some of his experiments.

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Effects of Prior Plasticity on Subsequent Creep of Type 316 Stainless Steel at Elevated Temperature

Journal of Engineering Materials and Technology ◽

10.1115/1.3225844 ◽

1986 ◽

Vol 108 (1) ◽

pp. 68-74 ◽

Cited By ~ 22

Author(s):

Y. Ohashi ◽

M. Kawai ◽

T. Momose

Keyword(s):

Plastic Deformation ◽

Stainless Steel ◽

Creep Resistance ◽

Tensile Direction ◽

316 Stainless Steel ◽

Plastic Prestraining ◽

Axial Tensile ◽

Thin Walled ◽

Stress States ◽

Tubular Specimens

Interaction between creep and plastic deformation was studied experimentally for type 316 stainless steel at 650°C, with special emphasis on creep behavior subsequent to plastic prestraining. In combined creep-plasticity experiments, thin-walled tubular specimens were first prestrained plastically in the axial tensile direction, and were subsequently subjected to constant stress creep under various multiaxial stress states with an identical effective stress. Furthermore, the variation in creep resistance due to the plastic prestrain was compared with that due to the same amount of creep prestrain. From the experimental results, it was found that creep resistance was markedly enhanced by the plastic prestrain and that the increase in the creep resistance depended on the amount and relative direction of the plastic prestrain. The creep resistance was increased more markedly by creep prestrain than the same amount of plastic strain.

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Analysis and numerical prediction of the delamination behavior of debonded asymmetric sandwich shells with a thin-walled skin considering plastic deformation

Composite Structures ◽

10.1016/j.compstruct.2017.12.078 ◽

2018 ◽

Vol 188 ◽

pp. 220-232 ◽

Cited By ~ 5

Author(s):

Martin Pietrek ◽

Peter Horst

Keyword(s):

Plastic Deformation ◽

Numerical Prediction ◽

Thin Walled ◽

Sandwich Shells ◽

Delamination Behavior

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Influence of Crack on the Instability of GFRP Composite Cylindrical Shells under Combined Loading

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.877.453 ◽

2018 ◽

Vol 877 ◽

pp. 453-459

Author(s):

B. Angelina Catherine ◽

R.S. Priyadarsini

Keyword(s):

Structural Integrity ◽

Cylindrical Shells ◽

Laminated Composite ◽

External Pressure ◽

Industrial Applications ◽

Combined Loading ◽

Finite Element Software ◽

Buckling Behavior ◽

Thin Walled ◽

Composite Cylindrical Shells

Buckling is a prominent condition of instability caused to a shell structure as a result of axial loadings. The process of buckling becomes more complex while analyzing thin walled structures like shells. Today such thin walled laminated composite shells are gaining more importance in many defense and industrial applications since they have greater structural efficiency and performance in relation to isotropic structures. Comprehensive understanding of the buckling response of shell structures is necessary to assure the integrity of these shells during their service life. The presence of defects, such as cracks, may severely compromise their buckling behavior and jeopardize the structural integrity. This work aims in conducting numerical analysis of cracked GFRP (Glass fibre-reinforced polymer) composite cylindrical shells under combined loading to study the effect of crack size on the buckling behavior of laminated composite cylindrical shells with different lay-up sequences. The numerical analyses were carried out using the finite element software, ABAQUS in order to predict the buckling behaviour of cracked laminated composite cylinders subject to different combinations of axial compression, torsion, internal pressure and external pressure from the interaction buckling curves.

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Plastic Deformation of Metal Tubes Subjected to Lateral Blast Loads

Mathematical Problems in Engineering ◽

10.1155/2014/250379 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 4

Author(s):

Kejian Song ◽

Yuan Long ◽

Chong Ji ◽

Fuyin Gao

Keyword(s):

Mathematical Model ◽

Plastic Deformation ◽

Plastic Flow ◽

Cross Section ◽

Circular Tube ◽

Circular Tubes ◽

Simply Supported ◽

Different Dimensions ◽

Thin Walled ◽

Wave Induced

When subjected to the dynamic load, the behavior of the structures is complex and makes it difficult to describe the process of the deformation. In the paper, an analytical model is presented to analyze the plastic deformation of the steel circular tubes. The aim of the research is to calculate the deflection and the deformation angle of the tubes. A series of assumptions are made to achieve the objective. During the research, we build a mathematical model for simply supported thin-walled metal tubes with finite length. At a specified distance above the tube, a TNT charge explodes and generates a plastic shock wave. The wave can be seen as uniformly distributed over the upper semicircle of the cross-section. The simplified Tresca yield domain can be used to describe the plastic flow of the circular tube. The yield domain together with the plastic flow law and other assumptions can finally lead to the solving of the deflection. In the end, tubes with different dimensions subjected to blast wave induced by the TNT charge are observed in experiments. Comparison shows that the numerical results agree well with experiment observations.

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