scholarly journals On the use of the criterion of maximum reduced stresses in temperature problems of plane deformation

2021 ◽  
pp. 32-39
Author(s):  
Анастасия Валерьевна Ткачева
Keyword(s):  
Yield Strength ◽  
Residual Stresses ◽  
Heating Rate ◽  
Plastic Flow ◽  
Thin Plate ◽  
Plastic Material ◽  
Plane Deformation ◽  
Temperature Deformation ◽  
Finite Width ◽  
Elastic Plastic Material

Работа посвящена решению задачи температурного деформирования тонкой пластины конечной ширины, выполненной из упруго-пластичного материала. В качестве условий наступления пластического течения используется условие максимальных приведенных напряжений, с зависимостью предела текучести от температуры. Именно использование зависимости предела текучести от температуры делает невозможным получение решения с условием пластического течения Треска - Сен-Венана. Показывается, что в зависимости от скорости нагрева распределение остаточных напряжений может быть разным. Rabat is devoted to solving the problem of temperature deformation of a thin plate of finite width made of an elastic plastic material. As conditions for the onset of plastic flow, the condition of maximum reduced stresses is used, with the dependence of the yield strength on temperature. It is the use of the dependence of the yield strength on temperature that makes it impossible to obtain a solution with the condition of the plastic flow of Treska - Saint-Venant. It is shown that, depending on the heating rate, the distribution of residual stresses can be different.

Damage Accumulation and Fracture of Weld Joints under Low-Cyclic Loading Conditions

2015 ◽  
Vol 784 ◽  
pp. 179-189 ◽  
Author(s):  
V.M. Kornev
Keyword(s):  
Cyclic Loading ◽  
Plastic Material ◽  
Finite Width ◽  
Loading Conditions ◽  
Structured Materials ◽  
Weld Joints ◽  
Layer Composite ◽  
Average Crack ◽  
Elastic Plastic Material ◽  
Process Diagrams

Failure of weld joints under single and cyclic pulsating loading conditions is under consideration. A weld joint is modeled by three-layer composite. Stepwise propagation of the internal I mode crack under cyclic loading is investigated. Delamination of bimaterial composed of two structured materials is considered when a crack is located at the interface between two media. Loads under pulsating loading conditions are studied for elastic-plastic material. For analysis of this process, diagrams of quasi-brittle fracture of solids under cyclic loading conditions are proposed to be used. One of curves of the proposed diagram bears resemblance to the Kitagawa-Takahashi diagram. Estimates of average dimensionless velocity of stepwise crack propagation per loading cycle have been obtained in an explicit form for plain specimens of finite width. The relations derived for the average crack growth rate can be considered as structural expressions for plotting Paris’ curves.

Hole-Drilling Method for Residual Stress Measurement - Consideration of Elastic-Plastic Material Properties

2013 ◽  
Vol 768-769 ◽  
pp. 174-181 ◽  
Author(s):  
David von Mirbach
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Yield Stress ◽  
Material Properties ◽  
Plastic Material ◽  
Hole Drilling ◽  
Hole Drilling Method ◽  
Drilling Method ◽  
Elastic Plastic Material ◽  
Ring Core

Two commonly used mechanical methods for the determination of residual stresses are the hole-drilling method and the ring-core method, which can be regarded as semi-destructive. The most restricting limitation for the general applicability of both methods, according to the current state of science and technology, is the fact that the scope for relatively low residual stress under 60% of the yield stress is limited.This is a result of the notch effect of the hole or ring core, which leads to a plastification around and on the bottom of the hole and ring shaped groove already at stresses well below the yield stress of the material. The elastic evaluation of the resulting plastic strains leads consequently to an overestimation of the delineated residual stresses. In this paper the influence of elastic-plastic material properties no the specific calibration function for the hole-drilling method using the differential method is studied, and the method of adaptive calibration functions is presented.

Welding Residual Stress Analysis Using Axisymmetric Modeling for Shroud Support Structure

2008 ◽  
Author(s):  
Kazuo Ogawa ◽  
Yukihiko Okuda ◽  
Toshiyuki Saito ◽  
Takahiro Hayashi ◽  
Rie Sumiya
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Large Scale ◽  
Structural Integrity ◽  
Plastic Material ◽  
Welding Residual Stress ◽  
Stress Distributions ◽  
Surface Residual Stress ◽  
Actual Structure ◽  
Elastic Plastic Material

Recently, several cracks caused by stress corrosion cracking (SCC) have been found on welds of shroud supports in Boiling Water Reactor (BWR) plants. The major cause of SCC in a weld joint is considered due to welding residual stress generated in the fabrication processes of the components. For continuous safety operations, it is necessary to estimate the structural integrity of such shroud supports with cracks based on the distribution of residual stresses induced by welding. In order to know and to validate the numerical method of residual stresses induced by welding of large scale and complex shaped components, a BWR shroud support mock-up with a hemispherical base of reactor pressure vessel (RPV) was fabricated by Japan Nuclear Energy Safety Organization (JNES) as a national project. The mock-up has a 32° section of actual BWR shroud supports with approximately the same configurations, materials and welding conditions of an actual component. During welding in the fabrication process of the mock-up, temperature was measured and after completion of the mock-up fabrication, surface residual stress distributions for each weld were also measured by the sectioning method. In addition, through-thickness residual stress distributions were investigated. Residual stress for each weld was calculated by using axisymmetric models considering temperature dependent elastic-plastic material properties. Though the actual structure of shroud supports is essentially complex, we simplified axisymmetric models in the center of the cross section. The analysis results show a similar profile and good agreement with the measured results on the surface of all the welds and through the welds at the upper and lower joints of the shroud support leg.

Analysis of the spherical indentation cycle for elastic–perfectly plastic solids

2004 ◽  
Vol 19 (12) ◽  
pp. 3641-3653 ◽  
Author(s):  
L. Kogut ◽  
K. Komvopoulos
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Elastic Modulus ◽  
Yield Strength ◽  
Material Properties ◽  
Deformation Behavior ◽  
Plastic Material ◽  
Elastic Plastic ◽  
Loading And Unloading ◽  
Elastic Plastic Material

A finite element analysis of frictionless indentation of an elastic–plastic half-space by a rigid sphere is presented and the deformation behavior during loading and unloading is examined in terms of the interference and elastic–plastic material properties. The analysis yields dimensionless constitutive relationships for the normal load, contact area, and mean contact pressure during loading for a wide range of material properties and interference ranging from the inception of yielding to the initiation of fully plastic deformation. The boundaries between elastic, elastic–plastic, and fully plastic deformation regimes are determined in terms of the interference, mean contact pressure, and reduced elastic modulus-to-yield strength ratio. Relationships for the hardness and associated interference versus elastic–plastic material properties and truncated contact radius are introduced, and the shape of the plastic zone and maximum equivalent plastic strain are interpreted in light of finite element results. The unloading response is examined to evaluate the validity of basic assumptions in traditional indentation approaches used to measure the hardness and reduced elastic modulus of materials. It is shown that knowledge of the deformation behavior under both loading and unloading conditions is essential for accurate determination of the true hardness and reduced elastic modulus. An iterative approach for determining the reduced elastic modulus, yield strength, and hardness from indentation experiments and finite element solutions is proposed as an alternative to the traditional method.

scholarly journals Model Of Relaxation Of Residual Stresses In Hot-Rolled Strips

2015 ◽  
Vol 60 (3) ◽  
pp. 1935-1940 ◽  
Author(s):  
A. Milenin ◽  
R. Kuziak ◽  
V. Pidvysots'kyy ◽  
P. Kustra ◽  
Sz. Witek ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Plastic Material ◽  
Material Model ◽  
Creep Model ◽  
Creep Theory ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Hot Rolled

Abstract Residual stresses in hot-rolled strips are of practical importance when the laser cutting of these strip is applied. The factors influencing the residual stresses include the non uniform distribution of elastic-plastic deformations, phase transformation occurring during cooling and stress relaxation during rolling and cooling. The latter factor, despite its significant effect on the residual stress, is scarcely considered in the scientific literature. The goal of the present study was development of a model of residual stresses in hot-rolled strips based on the elastic-plastic material model, taking into account the stress relaxation. Residual stresses in hot-rolled strips were evaluated using the FEM model for cooling in the laminar cooling line and in the coil. Relaxation of thermal stresses was considered based on the creep theory. Coefficients of elastic-plastic material model and of the creep model for steels S235 and S355 were obtained from the experiments performed on the Gleeble 3800 simulator for the temperatures 35-1100°C. Experiments composed small tensile deformations of the sample (0.01-0.02) and subsequent shutter speed without removing the load. Model of the thermal deformation during cooling was obtained on the basis of the dilatometric tests at cooling rates of 0.057°C/s to 60°C/s. Physical simulations of the cooling process were performed to validate the model. Samples were fixed in the simulator Gleeble 3800, then heated to the temperature of 1200°C and cooled to the room temperature at a rate of 1-50°C/s. Changes of stresses were recorded. Good agreement between calculated and experimental values of stresses was observed. However, due to neglecting the effect of stress relaxation the stress at high temperatures was overestimated. Due to the change of their stress sign during the unloading process the resulting residual stresses were underestimated. Simulation of residual stresses in rolling and cooling were performed on the basis of the developed model. It was shown that the effect of stress relaxation and phase transformations on the distribution of residual stresses in strips is essential and neglecting these factors could lead to an underestimation of residual stresses.

Computer Simulation of Residual Stresses in Welding Process Using Finite Element Method

2008 ◽  
Vol 580-582 ◽  
pp. 439-442
Author(s):  
Shou Ju Li ◽  
Ying Xi Liu ◽  
Li Juan Cao ◽  
Zi Chang Shangguan
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Residual Stresses ◽  
Plastic Material ◽  
Yield Criterion ◽  
Welding Process ◽  
Material Model ◽  
Elastic Plastic Material ◽  
Von Mises ◽  
Element Method

The prediction procedures of the residual stresses in welding process were presented by using finite element techniques. Owing to localized heating by the welding process and subsequent rapid cooling, the residual stresses can arise in the weld itself and in the base metals. The bilinear elastic-plastic material model based on Von Mises yield criterion was developed. The material nonlinearity of weldment and welding fluid was dealt with using an incremental technique. Inside each step, the Newton-Raphson iteration method was utilized. A fully coupled thermo-mechanical twodimensional analysis was performed with finite element method. The model applied in this study adopts the technique of element birth and death to simulate the weld filler variation with time in multi-pass welded joints. The effects of welding speed on residual stresses are discussed.

Finite Element Simulation for Residual Stresses in Weling Process

2007 ◽  
Vol 353-358 ◽  
pp. 1915-1918
Author(s):  
He Yu ◽  
Shou Ju Li ◽  
Ying Xi Liu
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Plastic Material ◽  
Yield Criterion ◽  
Welding Process ◽  
Material Model ◽  
Element Simulation ◽  
Elastic Plastic Material ◽  
Von Mises ◽  
Raphson Iteration

Owing to localized heating by the welding process and subsequent rapid cooling, the residual stresses can arise in the weld itself and in the base metals. The prediction procedures of the residual stresses in welding process were presented by using finite element techniques. The bilinear elastic-plastic material model based on Von Mises yield criterion was developed. The material non-linearity of weldment and welding fluid was dealt with using an incremental technique. Inside each step, the Newton-Raphson iteration method was utilized. A fully coupled thermo-mechanical two-dimensional analysis was performed with finite element method. The model applied in this study adopts the technique of element birth and death to simulate the weld filler variation with time in multi-pass welded joints. The effects of welding speed on residual stresses are discussed.

Evaluation of the residual stress in stainless steel 304L hydraulically expanded joints

2020 ◽  
pp. 095440892096401
Author(s):  
Ying Hong ◽  
Xuesheng Wang ◽  
Yan Wang ◽  
Zhao Zhang ◽  
Yong Han
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Yield Strength ◽  
Residual Stresses ◽  
Heat Exchangers ◽  
Nuclear Power ◽  
The Finite Element Method ◽  
Power Stations ◽  
Stainless Steel 304 ◽  
Initial Clearance

Stainless steel 304 L tubes are commonly used in the fabrication of heat exchangers for nuclear power stations. The stress corrosion cracking (SCC) of 304 L tubes in hydraulically expanded tube-to-tubesheet joints is the main reason for the failure of heat exchangers. In this study, 304 L hydraulically expanded joint specimens were prepared and the residual stresses of a tube were evaluated with both an experimental method and the finite element method (FEM). The residual stresses in the outer and inner surfaces of the tube were measured by strain gauges. The expanding and unloading processes of the tube-to-tubesheet joints were simulated by the FEM. Furthermore, an SCC test was carried out to verify the results of the experimental measurement and the FEM. There was good agreement between the FEM and the experimental results. The distribution of the residual stress of the tube in the expanded joint was revealed by the FEM. The effects of the expansion pressure, initial tube-to-hole clearance, and yield strength of the tube on the residual stress in the transition zone that lay between the expanded and unexpanded region of the tube were investigated. The results showed that the residual stress of the expanded joint reached the maximum value when the initial clearance was eliminated. The residual stress level decreased with the decrease of the initial tube-to-hole clearance and yield strength. Finally, an effective method that would reduce the residual stress without losing tightness was proposed.

scholarly journals Room-temperature deformation of single crystals of ZrB2 and TiB2 with the hexagonal AlB2 structure investigated by micropillar compression

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhenghao Chen ◽  
Bhaskar Paul ◽  
Sanjib Majumdar ◽  
Norihiko L. Okamoto ◽  
Kyosuke Kishida ◽  
...  
Keyword(s):  
Single Crystals ◽  
Plastic Flow ◽  
Room Temperature ◽  
Resolve Shear Stress ◽  
Temperature Deformation ◽  
Slip Systems ◽  
Compression Tests ◽  
Plastic Deformation Behavior ◽  
Bulk Single Crystals ◽  
Micropillar Compression

AbstractThe plastic deformation behavior of single crystals of two transition-metal diborides, ZrB2 and TiB2 with the AlB2 structure has been investigated at room temperature as a function of crystal orientation and specimen size by micropillar compression tests. Although plastic flow is not observed at all for their bulk single crystals at room temperature, plastic flow is successfully observed at room temperature by the operation of slip on {1$${\bar{1}}$$ 1 ¯ 00}<11$${\bar{2}}$$ 2 ¯ 3> in ZrB2 and by the operation of slip on {1$${\bar{1}}$$ 1 ¯ 00}<0001> and {1$${\bar{1}}$$ 1 ¯ 00}<11$${\bar{2}}$$ 2 ¯ 0> in TiB2. Critical resolve shear stress values at room temperature are very high, exceeding 1 GPa for all observed slip systems; 3.01 GPa for {1$${\bar{1}}$$ 1 ¯ 00}<11$${\bar{2}}$$ 2 ¯ 3> slip in ZrB2 and 1.72 GPa and 5.17 GPa, respectively for {1$${\bar{1}}$$ 1 ¯ 00}<0001> and {1$${\bar{1}}$$ 1 ¯ 00}<11$${\bar{2}}$$ 2 ¯ 0> slip in TiB2. The identified operative slip systems and their CRSS values are discussed in comparison with those identified in the corresponding bulk single crystals at high temperatures and those inferred from micro-hardness anisotropy in the early studies.

Theory and Application of the Parallel-Plate Plastimeter. Part 2

1935 ◽  
Vol 8 (4) ◽  
pp. 587-596 ◽  
Author(s):  
J. R. Scott
Keyword(s):  
Plastic Flow ◽  
Parallel Plate ◽  
Plastic Material ◽  
Compressive Load ◽  
Flow Equation ◽  
Simple Type ◽  
Plastic Properties ◽  
Further Development ◽  
Rubber Stock ◽  
Existing Data

Abstract In Part I (loc. cit.) the behavior of a plastic material in the parallel-plate (Williams) plastimeter was studied, and an expression was deduced showing how the rate of decrease in thickness of the sample during compression depends on the volume of the sample, its plastic properties, the compressive load, and the thickness itself. Subsequently, observations were published which showed that the basic principle adopted in this study was incorrect in certain particulars. Peek (loc. cit.), using these observations as a basis, deduced a new expression for the rate of decrease in thickness, though this is too complex for convenient practical use, except in an approximate simplified form. It has now been shown that the expression deduced in Part I, in spite of the inaccurate basis used, is sufficiently near to the truth to render substantially correct the conclusions there stated concerning the plastic properties of unvulcanized rubber stocks. By adopting the more accurate basis used by Peek, moreover, expressions for the rate of decrease in thickness can be deduced for materials showing more complex types of plastic flow than that considered in Part I or by Peek; this had proved impossible by the method previously used. The expression obtained by Peek for the simple type of plastic flow, as well as those now deduced for the more complex types, can be expressed in a form that furnishes a simple and rapid method of examining and analyzing experimental results. As a result of the work described in this paper, it is thus possible to determine, from results obtained with the parallel-plate plastimeter, whether or not a material such as unvulcanized rubber stock exhibits any of the types of plastic flow represented in the general form by Equation 1, and, if so, to find the values of the plastic constants of the material. The procedure is similar to that described in Part I, and consists simply in comparing, by superposition, a set of standard curves drawn on transparent paper with the curve plotted from experimental data. This further development of the method of studying plastic properties by means of the parallel-plate plastimeter should greatly increase its utility as an instrument of research. It has not yet been possible to apply the new method to a systematic study of rubber stocks, but from an examination of existing data it appears that these stocks, tested at 90° C., agree approximately with various forms of the generalized plastic flow equation already referred to.

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