Single sample method for assessing the Baushinger effect

2020 ◽  
Vol 86 (7) ◽  
pp. 55-58
Author(s):  
A. D. Khvan ◽  
D. V. Khvan ◽  
A. A. Voropaev
Keyword(s):  
Plastic Deformation ◽  
Stress State ◽  
Yield Strength ◽  
Bauschinger Effect ◽  
Calculated Data ◽  
Compressive Yield Strength ◽  
Special Device ◽  
Compression Tests ◽  
Traditional Procedure

The Bauschinger effect is one of the fundamental properties of most metal alloys exposed to plastic deformation under non-monotonic loading. Development of the methods for quantifying this effect is one the important issues of the theory of plasticity. Calculation of the parameter characterizing the aforementioned effect is required for determination of the stress state in plastically deformable blanks upon pressure metal treatment. The value of the parameter (determined in standard tensile tests followed by subsequent compression of samples) is defined by the ratio of the conditional yield strength of the sample under compression to the value of the preliminary tensile stress. A series of cylindrical samples (~10 pcs.) is usually taken for tensile-compression tests. According to the traditional procedure, long-size standard specimens are pre-stretched to various degrees of plastic deformation. After that short specimens are cut out from those specimens for compression tests to determine the conditional compressive yield strength with a tolerance of 0.2% for plastic deformation. Such a procedure is rather time consuming and expensive. We propose and develop a new single-model method for estimating the Bauschinger effect which consists in testing of a single long-size specimen for tension followed by compression of the specimen in a special device providing deformation of a previously stretched specimen without flexure under conditions of a linear stress state. The device was designed, manufactured and underwent the appropriate tests. The device contains supporting elements in the form of conical-shaped sectors that prevent flexure of a long cylindrical specimen upon compression, a ratio of the working part length to diameter ranges from 5 to 10. The results of experimental determination of the parameter β characterizing the indicated effect are presented. The results of comparing the values of the parameter β determined by the developed and traditional methods revealed the possibility of determining the parameter β using the proposed method. To reduce the complexity of performing tests related to determination of the parameter β we approximated it in the form of an exponent as a function of the magnitude of plastic deformation and determine the only one value of β0 under plastic deformations exceeding 0.05. In this regard, β0 can be considered a new characteristic of the material. The calculated data are in good agreement with the experimental results. The values of β0 are determined for a number of studied steel grades.

Formability of Explosive Welded Mg/Al Bimetallic Bar

2016 ◽  
Vol 716 ◽  
pp. 114-120 ◽  
Author(s):  
Sebastian Mróz ◽  
Piotr Szota ◽  
Teresa Bajor ◽  
Andrzej Stefanik
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Process Parameters ◽  
Metal Forming ◽  
Explosive Welding ◽  
Physical Modelling ◽  
Main Process ◽  
Compression Tests ◽  
Welding Method

The paper presents the results of physical modelling of the plastic deformation of the Mg/Al bimetallic specimens using the Gleeble 3800 simulator. The plastic deformation of Mg/Al bimetal specimens characterized by the diameter to thickness ratio equal to 1 was tested in compression tests. The aim of this work was determination of the range of parameters as temperature and strain rate that mainly influence on the plastic deformation of Mg/Al bars during metal forming processes. The tests were carried out for temperature range from 300 to 400°C for different strain rate values. The stock was round 22.5 mm-diameter with an Al layer share of 28% Mg/Al bars that had been produced using the explosive welding method. Based on the analysis of the obtained testing results it has been found that one of the main process parameters influencing the plastic deformation the bimetal components is the initial stock temperature and strain rate values.

The Influence of the Bauschinger Effect on the Yield Stress, Young’s Modulus, and Poisson’s Ratio of a Gun Barrel Steel

2005 ◽  
Vol 128 (2) ◽  
pp. 179-184 ◽  
Author(s):  
J. Perry ◽  
M. Perl ◽  
R. Shneck ◽  
S. Haroush
Keyword(s):  
Plastic Deformation ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Bauschinger Effect ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
Compression Tests ◽  
Residual Stress Field ◽  
Gun Barrel

The Bauschinger effect (BE) was originally defined as the phenomenon whereby plastic deformation causes a loss of yield strength restraining in the opposite direction. The Bauschinger effect factor (BEF), defined as the ratio of the yield stress on reverse loading to the initial yield stress, is a measure of the magnitude of the BE. The aim of the present work is to quantitatively evaluate the influence of plastic deformation on other material properties such as Young’s modulus and Poisson’s ratio for gun barrel steel, thus extending the definition of the Bauschinger effect. In order to investigate the change in this material’s properties resulting from plastic deformation, several uniaxial tension and compression tests were performed. The yield stress and Young’s modulus were found to be strongly affected by plastic strain, while Poisson’s ratio was not affected at all. An additional result of these tests is an exact zero offset yield point definition enabling a simple evaluation of the BEF. A simple, triphase test sufficient to characterize the entire elastoplastic behavior is suggested. The obtained experimental information is readily useful for autofrettage residual stress field calculations.

Collapse Resistance Under Combined External Pressure and Bending Deformation of Coated Linepipe

2020 ◽  
Author(s):  
Takahiro Sakimoto ◽  
Hisakazu Tajika ◽  
Tsunehisa Handa ◽  
Yoshiaki Murakami ◽  
Satoshi Igi ◽  
...  
Keyword(s):  
Yield Strength ◽  
Deep Water ◽  
Thermal Cycle ◽  
Bauschinger Effect ◽  
Heating Temperature ◽  
External Pressure ◽  
Compressive Yield Strength ◽  
Heat Cycle ◽  
Bending Deformation ◽  
Collapse Resistance

Abstract As offshore pipeline projects have expanded to deeper water regions with depths of more than 2 000 m, higher resistance against collapse by external pressure is now required in linepipe. Collapse resistance is mainly controlled by the pipe geometry and compressive yield strength. In UOE pipe, the compressive yield strength along the circumferential direction changes dramatically due to tensile pre-strain that occurs in pipe forming processes such as the expansion process. In order to improve the compressive yield strength of pipes, it is important to consider the Bauschinger effect caused by pipe expansion. As the mechanism of this effect, it is understood that internal stress is generated by the accumulation of dislocations, and this reduces reverse flow stress. Compressive yield strength is also changed by the thermal cycle associated with application of fusion-bond epoxy in pipe anti-corrosion coating by induction heating. In the typical thermal heat cycle of this coating process, the maximum heating temperature is from 200 °C to 250 °C. In this case, compressive yield strength increases as an effect of the thermal cycle, resulting in increased collapse resistance. Thus, for deep water application of UEO linepipe, it is important to clarify the conflicting effects of the Bauschinger effect and the thermal heat cycle on compressive yield strength. During installation of deep water pipelines by a method such as J-lay, curvature is imposed on the pipe axis, but the circumferential bending that leads to ovalization is determined by the interaction of the curvature of bending deformation. This bending deformation decreases collapse resistance. The interaction of external pressure and bending is also important when evaluating collapse. Against this background, this study discusses the collapse criteria for coated linepipe and their bending interaction against collapse based on a full-scale collapse test under external pressure with and without bending loading. The effect of the thermal heat cycle on linepipe collapse criteria is also discussed based on the results of tensile pre-strain tests with simulation of the thermal cycle and a collapse calculation by FEA.

Determination of the compressive yield strength for nano-grained YAG transparent ceramic by XRD analysis

2016 ◽  
Vol 671 ◽  
pp. 527-531 ◽  
Author(s):  
H.M. Wang ◽  
J.S. Jiang ◽  
Z.Y. Huang ◽  
Y. Chen ◽  
K. Liu ◽  
...  
Keyword(s):  
Yield Strength ◽  
Xrd Analysis ◽  
Transparent Ceramic ◽  
Compressive Yield Strength

scholarly journals Controlling shear band instability by nanoscale heterogeneities in metallic nanoglasses

2021 ◽  
Author(s):  
Sree Harsha Nandam ◽  
Ruth Schwaiger ◽  
Aaron Kobler ◽  
Christian Kübel ◽  
Chaomin Wang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Yield Strength ◽  
Shear Band ◽  
Metallic Glasses ◽  
Strain Localization ◽  
Catastrophic Failure ◽  
Compression Tests ◽  
Medium Range ◽  
Shear Transformation ◽  
Shear Transformation Zones

Abstract Strain localization during plastic deformation drastically reduces the shear band stability in metallic glasses, ultimately leading to catastrophic failure. Therefore, improving the plasticity of metallic glasses has been a long-standing goal for several decades. In this regard, nanoglass, a novel type of metallic glass, has been proposed to exhibit differences in short and medium range order at the interfacial regions, which could promote the formation of shear transformation zones. In the present work, by introducing heterogeneities at the nanoscale, both crystalline and amorphous, significant improvements in plasticity are realized in micro-compression tests. Both amorphous and crystalline dispersions resulted in smaller strain bursts during plastic deformation. The yield strength is found to increase significantly in Cu–Zr nanoglasses compared to the corresponding conventional metallic glasses. The reasons for the mechanical behavior and the importance of nanoscale dispersions to tailor the properties is discussed in detail. Graphic Abstract

Enhancement of Collapse Resistance of UOE Pipe Based on Systematic Exploitation of Thermal Cycle of Coating Process

2008 ◽  
Author(s):  
Andreas Liessem ◽  
Johannes Groß-Weege ◽  
Steffen Zimmermann ◽  
Gerhard Knauf
Keyword(s):  
Plastic Deformation ◽  
Thermal Treatment ◽  
Yield Strength ◽  
Thermal Cycle ◽  
Compressive Yield Strength ◽  
Coating Process ◽  
Cold Plastic Deformation ◽  
Production Route ◽  
Collapse Strength ◽  
Collapse Resistance

The present paper discusses recent results of an ongoing study on the effect of thermal treatment on collapse strength of cold formed pipes, for instance those following the UOE production route. It has been recognized that thermal treatment as encountered during thermal cycle of pipe coating processes may compensate the reduction of compressive yield strength owing to cold plastic deformation induced during forming. This effect has been systematically analyzed. Enhancement of collapse resistance exploiting the thermal cycle of coating process was studied based on experimental evidence, Finite Element simulations as well as theoretical analysis. It is herein shown that appropriate thermal treatment manifests itself positively with respect to compressive yield strength, leading to significantly improved collapse pressures. As a result fabrication factors of one and even higher may be applicable.

Simulation of Aluminium Foam Compressive Properties

2010 ◽  
Vol 97-101 ◽  
pp. 3033-3037
Author(s):  
Ming Juan Zhao ◽  
Long Zhi Zhao ◽  
De Ying Li ◽  
Xiao Qing Zuo ◽  
Jian Sheng Lu
Keyword(s):  
Plastic Deformation ◽  
Compressive Strength ◽  
Yield Strength ◽  
Aluminum Foam ◽  
Metal Foam ◽  
Compressive Yield Strength ◽  
Compressive Behavior ◽  
Compressive Properties ◽  
Al Foam ◽  
Simulation Results

In this paper, the simulation of the commpress properties of Al foam was investigated by finite element methods. The simulation results show that the compressive yield strength of Al foam is consistent with the theoretical model of Gibson and Ashby. The yield strength of Al foam decrease with the increase of porosity, and the yield strength decreases significantly with the increase of porosity. The density of Al foam is proportional to the compressive strength. At a certain porosity, the ratio of sample size and the aperture have an extremely important effects on compressive behavior of aluminum foam. When 4 ≤ D / d <8, with the increase of the ratio of D / d, the plastic deformation plateau and the compressive strength of metal foam is increasing ; on the contrary ,when the ratio> 8, with the increase of the ratio, the plastic deformation plateau is decreasing, the compressive strength keeps constant.

Sign in / Sign up

Export Citation Format

Share Document