Deformation Behavior Of Metals Research Articles

Suitability Analysis of the Deformation Behavior of Metal Corrugated Casing in High-Temperature Wellbore

The stability of the casing is a crucial prerequisite for implementing the in situ high-temperature steam injection method in oil shale reservoirs. In order to address the issues of substantial expansion, concentrated thermal stresses, and susceptibility to damage observed in traditional straight casings under high temperatures, this paper proposes the utilization of a corrugated casing structure. In this regard, to investigate the impact of the shape and structure of the wellbore casing on its mechanical properties, identical corrugated and straight casings were selected and studied. Uniaxial compression and tensile tests were conducted on the casings, along with coordination deformation experiments between the casing and cement sheath under varying temperatures. Numerical simulations were employed to obtain the deformation characteristics of the corrugated and straight casings under axial compression and tension loads, as well as the stress distribution on the outer casing wall. The results showed that when subjected to the same amount of deformation under axial loading, the corrugated casing experienced lower compressive and tensile loads compared to the straight casing. Moreover, under the sole constraint of cement sheath, increasing the temperature led to lower vertical strains (perpendicular to the ground) at all measuring points of the corrugated casing as compared to the corresponding strains in the straight casing. Numerical simulations revealed that, under the same temperatures, the deformation at the interface between the corrugated casing and the cement sheath was smaller, while the vertical stress at the interface of the corrugated casing was also lower than the straight casing. Overall, the corrugated casing, with its corrugated structure that enabled micro-deformation, effectively mitigated the axial deformation of the casing caused by thermal expansion. Consequently, the corrugated casing reduced the extrusion of wellbore casing on the cement sheath, thereby preserving the integrity and stability of the wellbore cementing structure.

A Lie-algebra-based description of disclination densities and the quantification of partial disclinations in deformed polycrystalline metals

Crystalline defects (e.g., dislocations, disclinations and grain boundaries) play a critical role in determining the mechanical and functional properties of metallic materials. From a physical point of view, dislocations and disclinations are the two fundamental types of topological defects in crystals, which originate from the breaking of translational symmetry and rotational symmetry, respectively. In spite of extensive studies on dislocations in the literature, the effects of disclinations on mechanical properties of metals have not been well recognized, partially due to the lack of an appropriate description for the rotational nature of disclinations. Here we suggest a Lie-algebra-based method to quantify the rotational properties of disclinations, which leads to a convenient way to determine disclination density distribution directly from Electron Backscatter Diffraction data. Through quasi-in-situ Electron Backscatter Diffraction characterizations, three major formation mechanisms of disclinations have been identified in deformed polycrystalline Mg alloys, i.e., dislocation-grain boundary interaction, dislocation redistribution and twin-twin reaction, all of which can be treated as topological reactions among various types of defects under a general framework. Our work not only suggests a new mathematical tool to investigate the interactions and reactions among multiple types of crystalline defects, but also provides a new insight to understand the deformation behaviors of metals and alloys based on dislocation/disclination theory.

Predicting High Temperature Flow Stress of Nickel Alloy A230 Based on an Artificial Neural Network

The high-temperature deformation behavior of metals and alloys undergoes complex mechanisms depending on the deformation conditions. The microstructure and mechanical properties after deformation are important factors that determine the strength and durability of the final product. Therefore, many studies to predict the microstructure and mechanical properties have been conducted. In this regard, numerous mathematical approaches for predicting microstructure and flow stress have been proposed over the past half century. Accordingly, many advances have been made in the field of material science. Nevertheless, there are limitations in the mathematical modeling method as there is a complex relationship between the deformation conditions and the mechanical properties. Therefore, in this study, flow stress prediction was performed by applying conventional constitutive equation and artificial intelligence technology, which is known to be effective in modeling complex relationships. As a result, it was confirmed that the flow stresses modeled by the artificial neural network showed a higher accuracy than the flow stresses modeled by the conventional Arrhenius hyperbolic sine equation.

Creep and Deformation of Metals and Alloys at Elevated Temperatures

Various aspects of creep and deformation behaviors of metals and alloys at elevated temperatures are of great interest to materials scientists [...]

State of the art methods to post-process mechanical test data to characterize the hot deformation behavior of metals

Materials engineering and science rely heavily on the indirect measurement of plastic stress and strain by post-processing of mechanical test data, including tension, torsion, and compression test. There is no consensus among researchers regarding the best test or the post-processing theory nor do adequate standards exist on the characterization methods. The tests are typically performed as customized tests, discrepancies exist in the flow curves obtained by different methods and the chosen mechanical test. More critically, the curves are dominantly treated (perceived) as a set of measured data rather than calculated values. The plasticity-based calculated flow curves and their gradients are, in turn, the basis for several second-tier indirect measurements, such as stacking fault energy and recrystallization. Such measurements are quite prone to errors due to oversimplified post-processing of the tests’ data and can only be experimentally verified in a qualitative or in an average fashion. Therefore, their findings are highly restricted by the limitations of each test, data type and post-processing method, and should be used carefully. This review examines some of the most commonly used data conversion methods and some recent developments in the field followed by recommendations. It will highlight the need to develop test rigs that can provide new data types and to provide advanced post-processing techniques for the indirect measurement.

Analysis of Tensile Deformation Behaviour of Dual Phase -590 Steel at Different Temperatures and Strain Rates

ABSTRACT An accurate uniaxial constitutive model is necessary to analyse the plastic deformation behaviour of metal and for reliable finite element simulations in sheet metal forming operations. In the present study, the hot uniaxial tensile flow stress analysis of dual phase (DP590) steel thin sheet has been carried out under a quasi-static strain rates of 0.1–0.001/s at the temperature range of 723–1073 K. The flow stress behaviour is significantly affected by test temperatures, strain rates and sheet orientations. Further, the Fields–Backofen constitutive flow relationship has been used to investigate the flow stress behaviour. This predicted flow stress curves shows a good fit to the experimentally measured stress at the work-hardening stage. Furthermore, a modified Fields–Backofen constitutive equation with a softening term has been considered to predict the flow behaviour. The capability of models has been evaluated based on the correlation coefficient (R), average absolute error AAE (Δavg) and root mean square error (RMSE). A better prediction of flow stress behaviour is observed by modified modified Fields–Backofen model with R = 0.9552, Δ = 0.034 and s = 0.0564.

A new development of four-point method to measure the electrical resistivity in situ during plastic deformation

The presented study introduces a new test method to measure the change of the electrical resistivity in situ during plastic deformation to characterize the deformation behaviour of metals. This investigation is based on a specially developed four- point method, which determines the change in electrical resistance of sheet samples of an aluminium alloy 6062, a copper alloy CW024A and steel DC04 in situ during deformation in a tensile test. Results show that the strain path, the deformation history, the plastic anisotropy as well as the plastic deformation have a significant influence on the electrical resistivity of all investigated materials. Therefore, this technique is universally applicable for all sheet metals, independent of the crystal structure, the electrical and mechanical properties to characterize structural changes during forming. The obtained data can be used for simulations of metal forming processes, e. g. to predict forming limit curves and damage monitoring under service loading.

Study of Mechanical Properties and Microstructural behaviour of alpha- beta brass at elevated temperature

Deformation behaviour of metal can be analyzed by determining mechanical properties for optimizing workability. In the present investigation hot uniaxial tensile test for alpha - beta brass material have been performed by considering parameters like temperature (RT, 6000C and 7000C), strain rate (0.1/s, 0.01/s and 0.001/s) and orientation (RD, ND and TD). The various material properties such as ultimate tensile strength (σu), yield stress (σy), total elongation(%) have been evaluated over the range of temperatures, strain rates and orientation. It have been observed that changes in material properties with respect to temperature, strain rate than orientation. The material properties has been analyse the mechanical characteristics of the material. The fractured specimens at various temperatures are studied and analyzed the failure modes in the material using Scanning Electron Microscope (SEM). SEM study confirms carbides and shear band which indicate predominantly ductile fracture in all the cases.

Correlation area size of excess dislocations of the same sign as a new mesoscopic characteristic of the dislocation substructure

The conception of correlation area size (CAS) of excess dislocations of the same sign (EDSS) as a new characteristic of deformation substructure of metals and alloys has been developed. CAS plays important role in elevated temperature creep deformation behavior of metals along with such substructure characteristics as subgrain size and misorientation angle. The main reasons of appearance and some features of CAS of EDSS have been considered. It is shown that CAS can be considered as feature determining the critical grain size. When grain size is less than CAS the creep rate becomes depending on grain size and mechanism changes from high temperature recovery to grain-boundary glide one.

Comparison of sub-grain scale digital image correlation calculated using commercial and open-source software packages

High-resolution strain mapping is an increasingly prominent technique for characterising the deformation behaviour of metals. In this study, HRDIC analysis was performed on materials exhibiting either more or less intense planar slip, using different software packages to highlight any issues that might arise depending on the algorithm that is used to calculate the displacements. The differences between the algorithms were investigated using frequency distributions, strain profiling and Burgers vector direction analysis to determine their significance in terms of any subsequent interpretation of the data. A dilute zirconium alloy showed maximum strain concentrations of <4.5 and similar to previous comparison studies of different software packages on optical images, little difference was observed in the resulting strain maps. However, in a more highly alloyed two-phase titanium alloy with significant planar slip and strain values of up to 20 times the applied strain, one of the algorithms had difficulty tracking the features particularly at low strains when the difference between the strain in a slip trace is markedly higher than that in the neighbouring region. The consequences of inaccurate displacement data around a slip trace region were highlighted by an incorrect prediction of the Burgers vector when using the relative displacement ratio for slip system identification.

Evaluation of metals deformability

The laws of the deformation behavior of metals, determined by carrying out standardized uniaxial tensile tests are studied. The distribution of various strength class metals by strain resistance is analyzed. It is taken into account that in the thermodynamic aspect the deformation process is dissipative effect, therefore, the deformation work, determined by the area of the tension diagram, serves as basis for assessing of the metals deformability criteria. It is found that the normalized specific work of deformation increases linearly with increasing strength. In the applied aspect, the numerical values of the compliance criterion can be used to predict the behavior of various strength class materials during mechanical processing (metal forming and cutting) or operation.

Determination of Constitutive Relationships of Tubular Materials at Various Strain Rates Using Hydro-Bulging Experiments

Liquid impact forming (LIF) is a rapid tube hydroforming technique. The deformation behaviour of a metal tube may be different in LIF from that in tube hydroforming. A constitutive equation or equivalently an equivalent stress-strain relationship is generally used to describe the deformation behaviour of metals. The purpose of this work is to model the deformation behaviour of tubular materials in LIF using the Johnson-Cook (JC) structural model. LIF hydro-bulging experiments combined with the analytical approach based on the membrane theory and the force equilibrium equation were used to determine the model coefficients A, B, C, and n in the equations for SS304 stainless steel tubular materials. Finite element (FE) simulations of hydro-bulging under various impact velocities were carried out to validate the resultant JC model. The relationship between the strain rates and impact velocities was determined, the bulging heights between the equivalent stress-strain curves at different impact velocities were analysed, and the bulging heights obtained by FE simulations and experimental results were compared. The results show that the proposed approach using the JC model is suitable to define the stress-strain behaviour of tubular materials in LIF.

Estimates of Metal Deformability

This paper is devoted to the study of the laws of the deformation behavior of metals, determined by carrying out standardized uniaxial tensile tests. The distribution of various strength grade metals by strain resistance was analyzed. It was taken into account that in the thermodynamic aspect the deformation process is a dissipative effect. In that regard, the magnitude of deformation work, determined by the area of the tension diagram, serves as a basis for assessing the deformability criteria of metals. It was found, that the normalized specific work of deformation linearly increases with strength. As well as it was established that localization of plastic flow is related directly to the characteristics of the tension diagram under solid deformation. In the applied aspect, the numerical values of the compliance criterion can be used to predict the materials behavior of different strength grade during mechanical processing (metal forming and cutting) or operation.

Ultrasonic vibration-assisted metal forming: Constitutive modelling of acoustoplasticity and applications

This paper presents a new physics-based constitutive model to accurately describe the deformation behaviour of metals during ultrasonic vibration assisted (UVA) forming. Dislocation dynamics and acoustic energy transformation mechanisms in materials under ultrasonic vibration were considered in the modelling. A user defined subroutine was also developed for modelling the UVA forming processes using the finite element method. To assess the proposed model, upsetting forming, press forming, and incremental forming were simulated separately, and the predicted results were compared with their corresponding experiments. It was found that the application of the ultrasonic vibration can significantly decrease the material flow stress, making the material softer in forming. A large vibration amplitude results in a large reduction in flow stress. Relevant experimental measurements showed that the model has captured the material behaviour and the major mechanics in UVA forming. Different forming processes, due to their difference in tool-workpiece contact condition, would have different acoustic energy and stress transformation efficiency.

Research on Constitutive Relation of Metals under High Strain Rate

The deformation behavior of materials under high strain rate environment is often accompanied by complex physical conditions such as high temperature, high pressure and shock waves. In order to describe the deformation behavior of materials accurately, the external extreme conditions and internal micro-deformation mechanisms of the material must be considered fully. The constitutive relationship of materials is related to the relationship between stress and strain, strain rate, temperature, deformation history, etc. Different constitutive models are based on different conditions and assumptions. This paper summarizes the microscopic deformation mechanisms, constitutive models and physical test methods of the deformation behavior of metals under high strain rate. These three aspects are interrelated and inseparable to explain the deformation behavior of metals under high strain rate.

Finite element simulation of the T-shaped ECAP processing of round samples

Grain refinement is the only mechanism that increases the yield strength and toughness of the materials simultaneously. Severe plastic deformation is one of the promising methods to refine the microstructure of materials. Among different severe plastic deformation processes, the T-shaped equal channel angular pressing (T-ECAP) is a relatively new technique. In the present study, finite element analysis was conducted to evaluate the deformation behavior of metals during T-ECAP process. The study was focused mainly on flow characteristics, plastic strain distribution and its homogeneity, damage development, and pressing force which are among the most important factors governing the sound and successful processing of nanostructured materials by severe plastic deformation techniques. The results showed that plastic strain is localized in the bottom side of sample and uniform deformation cannot be possible using T-ECAP processing. Friction coefficient between sample and die channel wall has a little effect on strain distributions in mirror plane and transverse plane of deformed sample. Also, damage analysis showed that superficial cracks may be initiated from bottom side of sample and their propagation will be limited due to the compressive state of stress. It was demonstrated that the V shaped deformation zone are existed in T-ECAP process and the pressing load needed for execution of deformation process is increased with friction.

Using neural networks to predict the low curves and processing maps of TNM-B1

The ability to predict the behavior of a material is vital in both science and engineering. Traditionally, this task has been carried out using physics-based mathematical modeling. However, material behavior is dependent on a wide range of interconnected phenomena, properties and conditions. During deformation processes, work hardening, softening, microstructure evolution and generation of heat all occur simultaneously, and can either cooperate or compete. In addition, they can vary with the deformation temperature, applied force and process speed. As the complete picture of material behavior from the macroscopic scale to the atomic scale is not yet fully understood, deformation processes such as hot forg-ing can be difficult to handle using physics-based modeling. Usually, modeling the high temperature deformation behavior of metals consists of extracting characteristic points from the experimental flow curve data, and use them to fit the model equations through regression analysis. This is called phenomenological modeling, as it is based on the observations of a phenomena rather than being derived from fundamental theory. Alternatively, the data obtained from experiments could be used for a data-driven or machine learning (ML) approach to model the material behavior. An ML model would require no knowledge of the underlying physical phenomena governing a deformation process, as it can learn a mapping function which connects input to output based purely on the experimental data. In this work, the application of machine learning to modeling the flow curves of two different states of the titanium aluminide (TiAl) TNM-B1; hot isostatically pressed (HIPed) and heat treated, is investigated. Neural networks were used to learn a mapping function which predicted flow stress based on the inputs temperature, strain and strain rate. In addition, strain rate sensitivity maps and processing maps based on the experimental and the predicted data are analysed and compared. The results revealed that the neural networks were able to produce realistic and accurate flow curves, which fitted to the underlying behavior of the experimental data rather than the noise. The strain rate sensitivity and processing maps showed conflicting results. Good correlation was found for the HIPed material state between the ones based on experimental data and the ones based on predicted values, while there was a significant difference for the heat treated state.

A constitutive model for metal plastic deformation at micro/meso scale with consideration of grain orientation and its evolution

Traditional metal forming theories are not accurate in the analysis of micro/meso scale metal deformation behavior due to the so-called size effect. As the deformation process scales down to micro/meso level, the characteristics of grain orientation and its evolution play an important role in the plastic deformation which leads to the significant size effect. In this study, the tensile tests of pure copper sheet metal specimens with different grain sizes were first conducted. The flow stress is found to decrease with the increase of grain size. In addition, the specimens with coarse grain show greater scatter in flow stress and higher surface roughness due to the grain orientation effect. Furthermore, the volume fractions for three main grain orientations (<111>, <100> and <110>) were measured by electron backscatter diffraction (EBSD) both before and after the tensile tests. It is revealed that <111> is a stable orientation while the grains with the orientation of <110> tend to rotate to the orientation of <111> after deformation.Based on the experimental observations, a constitutive model with the consideration of grain orientation and its evolution was established to analyze the size effect induced. The new constitutive model was then applied in finite element (FE) simulations to characterize the influences of grain orientation and its evolution on the plastic deformation. To consider the grain heterogeneity, Voronoi tessellation was employed in the FE model establishment to simulate the polycrystalline aggregate of material. The computed results of flow stress, scatter of data and surface roughness for different grain sizes are revealed to be in accordance with the experimental results, which verify the applicability of the model established in this work.

Plastic deformation of FCC alloys at cryogenic temperature: the effect of stacking-fault energy on microstructure and tensile behaviour

The deformation behaviour of metals and alloys is significantly affected by both stacking-fault energy and processing temperature. By lowering the former, deformation twinning is favoured over dislocation slip, whilst cryogenic processing partially suppresses dynamic recovery. Three materials having different stacking-fault energies, that is, Al AA1050 (high), pure Cu (medium) and Cu–15Zn alloy (low) were rolled at room (RTR) and at cryogenic (CR) temperatures up to a true strain equal to 1.5. Annealed coarse-grained samples were tested in tension at room and cryogenic temperatures. The processed samples were characterized by optical and transmission electron microscopy, hardness measurements and room-temperature tensile tests. CR increases the tensile strength with respect to RTR for the three materials; elongation to failure is decreased for AA1050, whilst for Cu and Cu–15Zn the CR effectively increases the ductility. Cu–15Zn sample after CR exhibits a microstructure relatively heterogeneous, suggesting static recrystallization events in the temperature excursion from 77 to 298 K. Finally, it was concluded that cryogenic deformation increases strength, whilst low SFE increases the ability to absorb plastic deformation, an effect strongly increased at cryogenic temperatures. The present investigation gives some basis for the development of cryogenic severe plastic deformation processes.

中性子線による金属材料の組織と弾塑性変形挙動の解析(III)&lt;br/&gt;─弾塑性変形その場測定─

中性子線による金属材料の組織と弾塑性変形挙動の解析(III)&lt;br/&gt;─弾塑性変形その場測定─