scholarly journals Development of Deformation Textures in Polycrystalline Copper Experiments and Model Predictions

1987 ◽  
Vol 7 (2) ◽  
pp. 149-170 ◽  
Author(s):  
H. Naaman ◽  
R. Talreja ◽  
D. Juul Jensen ◽  
N. Hansen
Keyword(s):  
Flow Stress ◽  
Strain Range ◽  
Large Strains ◽  
Polycrystalline Copper ◽  
Taylor Model ◽  
Broad Agreement ◽  
Model Predictions ◽  
Deformation Textures ◽  
Strain Relationship ◽  
Textural Development

The textural development and flow stress have been determined in compression and tension of copper (99.999%). For strains below 1.4 (compression) and 1.0 (tension) the textural development is in qualitative agreement with Taylor-model predictions, i.e. a maximum concentration at the 〈110〉 and 〈111〉 + 〈100〉 orientations for compression and tension, respectively. The grain size (23 and 125 μm) has only a relatively small effect on the textural development. For large strains 1.4–2.9 (compression) the textural development is in broad agreement with relaxed-constraints (RC) model predictions. In the strain range where the Taylor-model is prevalent the textural development has only a small effect on the M-factor, i.e. on the flow stress–strain relationship.

Polycrystalline Model Predictions of Flow Stress and Textural Hardening during Monotonic Deformation

2013 ◽  
Vol 554-557 ◽  
pp. 1157-1163 ◽  
Author(s):  
Qing Ge Xie ◽  
Philip Eyckens ◽  
Henk Vegter ◽  
Jaap Moerman ◽  
Bert van Bael ◽  
...  
Keyword(s):  
Flow Stress ◽  
Texture Evolution ◽  
Quantitative Agreement ◽  
Mechanical Tests ◽  
Taylor Model ◽  
Dislocation Hardening ◽  
Grain Interaction ◽  
Model Predictions ◽  
Strain Relationship ◽  
Polycrystalline Model

A series of mechanical tests in different specimen orientations was performed to study the anisotropic behavior of an IF steel (DC06). State-of-the-art polycrystalline models Alamel [1], VPSC [2], as well as the classical FC Taylor model were employed to predict flow stress curves. A two-stage Voce law was used to describe the single crystal shear stress-accumulated shear strain relationship. In this approach, the textural hardening and the dislocation hardening are effectively modeled separately. Results demonstrate that both the Alamel and VPSC models could reproduce the flow stress curves adequately. Also, the quantitative agreement of texture prediction is used to validate the model predictions. It is concluded that the better performance of grain interaction models compared to the FC Taylor model is mainly due to an improved prediction of the slip inside the constituting grains, and not in particular due to an improved prediction of texture evolution.

Methods for measuring friction-independent flow stress curve to large strains using hyperbolic shaped compression specimen

2021 ◽  
pp. 030932472199567
Author(s):  
Junfu Chen ◽  
Zhiping Guan ◽  
Jingsheng Xing ◽  
Jiawang Song ◽  
Dan Gao ◽  
...  
Keyword(s):  
Flow Stress ◽  
Analytical Method ◽  
Inverse Method ◽  
Strain Range ◽  
True Stress ◽  
Correction Function ◽  
Large Strains ◽  
N Value ◽  
Stress Curve ◽  
Flow Stress Curve

The accurate measurement of flow stress curve to large strains using cylindrical compression specimen is always a great challenge due to the influence of friction. Recently, the present authors designed a hyperbolic shaped compression (HSC) specimen which can yield an average true stress- strain curve independent of friction and proposed a stress correction function for fast estimation of flow stress curve to large strains. The aim of this paper is threefold. Firstly, to investigate whether the analytical method for stress correction of tensile necking can, or cannot, be extended to HSC specimen for correcting average true stress into flow stress. Secondly, to develop an inverse method based on Kriging surrogate model for identifying the optimal parameters of modified Voce model using HSC specimen. Lastly, the advantages and disadvantages of these three methods were compared and the recommendations for application were also discussed. The results show that the analytical method is more suitable to the stress correction for material with higher n-value but shows worse capability for correcting flow stress related to large strains for material with lower n-value. For Q420 steel, the maximum strain achieved by HSC specimen (0.8) is far higher than that achieved by cylindrical tension specimen (0.55). The analytical method can correct the flow stress in the strain range of 0–0.5 effectively but underestimating the flow stress in the strain range of 0.5–0.8 due to its low n-value. Both inverse method and stress correction function can determine the flow stress in the strain range of 0–0.8 successfully. Thus, for isotropic material with tension–compression yield symmetry, it is recommended to use the HSC specimen instead of conventional tension and compression tests of cylindrical specimens to determine the flow stress curve to large strains.

Temperature and Strain Rate Effects on Mechanical Behavior of a PMMA

2007 ◽  
Vol 340-341 ◽  
pp. 1079-1084 ◽  
Author(s):  
Tao Suo ◽  
Yu Long Li ◽  
Yuan Yong Liu
Keyword(s):  
Flow Stress ◽  
High Strain Rate ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
High Strain ◽  
Strain Range ◽  
Testing Temperature ◽  
Strain Rate Effects ◽  
Rate Effects ◽  
Increasing Temperature

In this paper, the mechanical behavior of a PMMA used as the windshield of aircraft was tested. The experiments were finished under two quasi-static strain rates and a high strain rate with the testing temperature from 299K to 373K. The results show that the mechanical property of this PMMA depends heavily on the testing temperature. The Young’s modulus and flow stress were found to decrease with increasing temperature at low strain rate. At the strain rate of 10-1 1/s, strain softening was observed under all experiment temperatures. At high strain rate, with the temperature increasing, the flow stress decreases remarkably while the failure strain increases, and the strain soften was also observed at the temperature above 333K. Comparing the experiments results at same temperature, it was found the flow stress increases with the rising strain rate. The predictions of the mechanical behavior using the ZWT theoretical model have a good agreement with experimental results in the strain range of 8%.

Fracture Assessment of Pipes Having Multiple Flaws Based on Ramberg–Osgood-Type Stress–Strain Relationships

2011 ◽  
Author(s):  
Hideo Machida ◽  
Tetsuya Hamanaka ◽  
Yoshiaki Takahashi ◽  
Katsumasa Miyazaki ◽  
Fuminori Iwamatsu ◽  
...  
Keyword(s):  
Flow Stress ◽  
Stress Concentration ◽  
Fracture Strength ◽  
Strain Curve ◽  
Assessment Method ◽  
Experimental Results ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Relationship ◽  
Fracture Assessment

This paper describes a fracture assessment method for a pipe having multiple circumferential flaws. According to Fitness-for-Service (FFS) codes for nuclear facilities published by the Japanese Society of Mechanical Engineers (JSME), the fracture strength of a high-ductility pipe having a circumferential flaw is evaluated using the limit load assessment method assuming the elastic–perfectly-plastic stress–strain relationship. In this assessment, flow stress is used as a proportional stress. However, previous experimental results [1, 2, 3] show that a crack penetrates before the entire flawed pipe section reaches the flow stress. Therefore, stress concentration at a flaw was evaluated on the basis of the Dugdale model [4], and the fracture strength of the crack-ligament was evaluated. This model can predict test results with high accuracy when the ligament fracture strength is assumed to be tensile strength. Based on this examination, a fracture assessment method for pipes having multiple flaws was developed considering the stress concentration in the crack-ligament by using the realistic stress–strain relationship (Ramberg–Osgood-type stress–strain curve). The fracture strength of a multiple-flawed pipe estimated by the developed method was compared with previous experimental results. When the stress concentration in the crack-ligament was taken into consideration, the fracture strength estimated using the Ramberg–Osgood-type stress–strain curve was in good agreement with experimental results, confirming the validity of the proposed method.

Limitations in Measuring the Flow Stress

2013 ◽  
Vol 752 ◽  
pp. 85-94 ◽  
Author(s):  
György Krállics ◽  
András Reé ◽  
Kristóf Bobor ◽  
Viktor Szombathelyi
Keyword(s):  
Flow Stress ◽  
Plane Strain ◽  
Working Conditions ◽  
Cold Working ◽  
High Strain ◽  
Strain Range ◽  
Experimental Methods ◽  
Equivalent Strain ◽  
Stress And Strain ◽  
Fe Modeling

In designing of plastic metalworking technologies, one determining amount used is the flow stress (kf ) of the material to be formed. A few experimental methods are used to measure it, but in all case it is intended to establish a specific stress and strain state in the whole volume of the specimen, or at least in its majority. In our work the limitations of upsetting in axial symmetrical and plane strain states were investigated by FE modeling and experimental methods within cold working conditions. Both methods were executed on traditional testing machines and Gleeble 3800 thermo-mechanical simulator. It was intended to determine the flow stress up to as high strain values as possible. The processing of the experimental results showed, reliable flow stress values were obtainable in the equivalent strain range of 0 to 3 using the step-by-step upsetting in plane strain, and in the 0 to 1.2 range by cylindrical upsetting.

The Application of Multiscale Modelling for the Prediction of Plastic Anisotropy and Deformation Textures

2005 ◽  
Vol 495-497 ◽  
pp. 31-44 ◽  
Author(s):  
Paul van Houtte ◽  
Albert Van Bael ◽  
Marc Seefeldt ◽  
Laurent Delannay
Keyword(s):  
Metal Forming ◽  
Aluminium Alloys ◽  
Dislocation Substructure ◽  
Plastic Anisotropy ◽  
Microscopic Level ◽  
Finite Element Models ◽  
Taylor Model ◽  
Deformation Textures ◽  
Level Model ◽  
Multi Level

The paper focuses on the multi-level character of existing or currently developed models for polycrystal deformation. A general multilevel frame is presented, which can be applied to models for the simulation of plastic anisotropy to be implemented in FE codes for the simulation of metal forming processes, or to models for the simulation of deformation textures. A short overview is presented of two-level models ranging from the full-constraints Taylor model to the crystalplasticity finite element models, including the description of a few recent and efficient models (GIA and ALAMEL). Validation efforts based on experimental cold rolling textures obtained for steel and aluminium alloys are discussed. Finally a recent three-level model which also takes the microscopic level (dislocation substructure) is discussed.

scholarly journals Practical and Durable Flexible Strain Sensors Based on Conductive Carbon Black and Silicone Blends for Large Scale Motion Monitoring Applications

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4553 ◽  
Author(s):  
Yun Xia ◽  
Qi Zhang ◽  
Xue E. Wu ◽  
Tim V. Kirk ◽  
Xiao Dong Chen
Keyword(s):  
Carbon Black ◽  
Large Scale ◽  
Low Cost ◽  
Strain Range ◽  
Human Motion ◽  
Flexion Angle ◽  
Gauge Factor ◽  
Large Strains ◽  
Human Motion Detection

Presented is a flexible capacitive strain sensor, based on the low cost materials silicone (PDMS) and carbon black (CB), that was fabricated by casting and curing of successive silicone layers—a central PDMS dielectric layer bounded by PDMS/CB blend electrodes and packaged by exterior PDMS films. It was effectively characterized for large flexion-angle motion wearable applications, with strain sensing properties assessed over large strains (50%) and variations in temperature and humidity. Additionally, suitability for monitoring large tissue deformation was established by integration with an in vitro digestive model. The capacitive gauge factor was approximately constant at 0.86 over these conditions for the linear strain range (3 to 47%). Durability was established from consistent relative capacitance changes over 10,000 strain cycles, with varying strain frequency and elongation up to 50%. Wearability and high flexion angle human motion detection were demonstrated by integration with an elbow band, with clear detection of motion ranges up 90°. The device’s simple structure and fabrication method, low-cost materials and robust performance, offer promise for expanding the availability of wearable sensor systems.

scholarly journals Enhancing Constitutive Models for Soils: Adding the Capability to Model Nonlinear Small Strain in Shear

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
S. Seyedan ◽  
W. T. Sołowski
Keyword(s):  
Yield Surface ◽  
Constitutive Models ◽  
Strain Range ◽  
Small Strain ◽  
Deviatoric Stress ◽  
Triaxial Tests ◽  
Engineering Practice ◽  
Model Parameters ◽  
Highly Nonlinear ◽  
Strain Relationship

The deviatoric stress-deviatoric strain relationship in soils is highly nonlinear, especially in the small strain range. However, the constitutive models which aim to replicate the small strain nonlinearity are often complex and rarely used in geotechnical engineering practice. The goal of this study is to offer a simple way for updating the existing constitutive models, widely used in geotechnical practice, to take into account the small strain shear modulus changes. The study uses an existing small strain relationship to derive a yield surface. When the yield surface is introduced to an existing soil model, it enhances the model with the nonlinear deviatoric stress-deviatoric strain relationship in the small strain range. The paper also gives an example of such a model enhancement by combining the new yield surface with the Modified Cam Clay constitutive model. The validation simulations of the undrained triaxial tests on London Clay and Ham River sand with the upgraded constitutive models replicate the experiments clearly better than the base models, without any changes to existing model parameters and the core source code associated with the base model.

Stress–Strain Relationship for Metal Hollow Sphere Materials as a Function of Their Relative Density

2006 ◽  
Vol 74 (5) ◽  
pp. 898-907 ◽  
Author(s):  
D. Karagiozova ◽  
T. X. Yu ◽  
Z. Y. Gao
Keyword(s):  
Relative Density ◽  
Hollow Sphere ◽  
Deformation Energy ◽  
Large Strains ◽  
Test Results ◽  
Stress Strain ◽  
Hexagonal Packing ◽  
Element Simulation ◽  
Theoretical Predictions ◽  
Strain Relationship

The stress–strain relationship for uniaxial compression of a metal hollow sphere material in large strains is obtained using a simplified model for the spheres’ deformation within a 3D block assuming a hexagonal packing pattern. The yield strength and material strain hardening are obtained as functions of the relative density in two characteristic loading directions. The expression for the stress–strain relationship consisting of quadratic and linear terms with respect to the relative density is linked to the partitioning of the deformation energy during compression. The theoretical predictions are compared with limited test results on mild steel hollow sphere material and finite element simulation results obtained by our group.

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