Establishing the ratios between the components of the plastic-strain deviator and the components of the stress deviator in a state of plane stress

1980 ◽  
Vol 12 (6) ◽  
pp. 806-812
Author(s):  
T. N. Mozharovskaya
Keyword(s):  
Plastic Strain ◽  
Plane Stress ◽  
Stress Deviator ◽  
Strain Deviator

scholarly journals Spatiotemporal Evolution of Stress Field during Direct Laser Deposition of Multilayer Thin Wall of Ti-6Al-4V

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 263
Author(s):  
Sergei Ivanov ◽  
Antoni Artinov ◽  
Evgenii Zemlyakov ◽  
Ivan Karpov ◽  
Sergei Rylov ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Plastic Strain ◽  
Plane Stress ◽  
Laser Deposition ◽  
Momentum Balance ◽  
Residual Stress Field ◽  
Direct Laser Deposition ◽  
Simulation Procedure ◽  
Direct Laser

The present work seeks to extend the level of understanding of the stress field evolution during direct laser deposition (DLD) of a 3.2 mm thick multilayer wall of Ti-6Al-4V alloy by theoretical and experimental studies. The process conditions were close to the conditions used to produce large-sized structures by the DLD method, resulting in specimens having the same thermal history. A simulation procedure based on the implicit finite element method was developed for the theoretical study of the stress field evolution. The accuracy of the simulation was significantly improved by using experimentally obtained temperature-dependent mechanical properties of the DLD-processed Ti-6Al-4V alloy. The residual stress field in the buildup was experimentally measured by neutron diffraction. The stress-free lattice parameter, which is decisive for the measured stresses, was determined using both a plane stress approach and a force-momentum balance. The influence of the inhomogeneity of the residual stress field on the accuracy of the experimental measurement and the validation of the simulation procedure are analyzed and discussed. Based on the numerical results it was found that the non-uniformity of the through-thickness stress distribution reaches a maximum in the central cross-section, while at the buildup ends the stresses are distributed almost uniformly. The components of the principal stresses are tensile at the buildup ends near the substrate. Furthermore, the calculated equivalent plastic strain reaches 5.9% near the buildup end, where the deposited layers are completed, while the plastic strain is practically equal to the experimentally measured ductility of the DLD-processed alloy, which is 6.2%. The experimentally measured residual stresses obtained by the force-momentum balance and the plane stress approach differ slightly from each other.

Ductile Tearing Instability of a Center-Cracked Panel of an Elastic-Plastic Strain Hardening Material

1981 ◽  
Vol 103 (1) ◽  
pp. 46-54 ◽  
Author(s):  
Akram Zahoor ◽  
Paul C. Paris
Keyword(s):  
Plastic Strain ◽  
Strain Hardening ◽  
Plane Strain ◽  
Plane Stress ◽  
Hardening Material ◽  
Ductile Tearing ◽  
Elastic Plastic ◽  
Linear Elastic ◽  
Tearing Instability ◽  
Crack Stability

An analysis for crack instability in an elastic-plastic strain hardening material is presented which utilizes the J-integral and the tearing modulus parameter, T. A center-cracked panel of finite dimensions with Ramberg-Osgood material representation is analyzed for plane stress as well as plane strain. The analysis is applicable in the entire range of elastic-plastic loading from linear elastic to full yield. Crack instability is strongly influenced by the elastic compliance of the system, the conditions of plane stress or plane strain, and the hardening characteristics of the material. Numerical results indicate that if crack stability is ensured in a plane strain situation, then under the same circumstances a geometrically identical but plane stress panel will be stable.

On Proportional Combined Loading Tests of an Aluminum Alloy and Its Analytical Formulation

1976 ◽  
Vol 98 (3) ◽  
pp. 282-288 ◽  
Author(s):  
Y. Ohashi ◽  
K. Kawashima ◽  
N. Mori
Keyword(s):  
Aluminum Alloy ◽  
Plastic Strain ◽  
Equivalent Stress ◽  
Strain Curve ◽  
Experimental Results ◽  
Combined Loading ◽  
Stress Deviator ◽  
Third Invariant ◽  
Simple Tension ◽  
Loading Tests

Proportional combined loading tests using axial load and torque were conducted on thin-walled tubular specimens of annealed isotropic aluminum alloy 5056. The experimental results showed that the third invariant of stress deviator affects considerably the plastic deformation of the material; that is, an equivalent stress-equivalent strain curve for simple tension or compression appears higher than that for pure torsion and the plastic strain vector is generally noncoaxial with the deviatoric stress vector. These results were formulated in the form of a nonlinear tensor relation between stress deviator and plastic strain on the basis of the general relation between coaxial tensors. The tensor equation derived was found to represent well the experimental results.

Forming Limit Evaluation with Perturbation Approach Considering Through-Thickness Normal Stress

2019 ◽  
Vol 794 ◽  
pp. 48-54
Author(s):  
Qi Hu ◽  
Xi Feng Li ◽  
Jun Chen
Keyword(s):  
Plastic Strain ◽  
Normal Stress ◽  
Plane Stress ◽  
Fluid Pressure ◽  
Equivalent Plastic Strain ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Perturbation Approach ◽  
Thin Sheets ◽  
Forming Limit Curves

To predict material’s formability in the hydroforming processes, the plane stress assumption would be invalid. The instability perturbation approach proposed by Hu et al. [1] is extended with the through-thickness normal stress by combining Hill’48 and Hosford’s yield criteria. The influences of through-thickness normal stress on the predicted forming limit strains in the forms of traditional Forming Limit Diagram (FLD) and equivalent plastic strain (EPS) based FLD (epFLD) are investigated. The results show that forming limit curves (FLCs) in both forms of FLD enhance with increasing through-thickness normal stress under proportional and non-proportional loadings. This new model can be utilized to study the effects of fluid pressure on the formability of orthotropic thin sheets.

Plastic Deformation in Microtomed Sections

1971 ◽  
Vol 29 ◽  
pp. 458-459
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Applied Stress ◽  
Elastic Strain ◽  
High Strain ◽  
Tool Material ◽  
Cutting Edge ◽  
Material Structure ◽  
Geometrical Constraints

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.

Comparison of Substructures Between Uniaxial and Biaxial Deformation in 1100-0 Aluminum

1981 ◽  
Vol 39 ◽  
pp. 52-53
Author(s):  
D. L. Rohr ◽  
S. S. Hecker
Keyword(s):  
Plastic Strain ◽  
Cell Walls ◽  
Room Temperature ◽  
Mechanical Response ◽  
Biaxial Tension ◽  
Initial Deformation ◽  
Uniaxial Deformation ◽  
Biaxial Deformation ◽  
Stress States ◽  
Comprehensive Study

As part of a comprehensive study of microstructural and mechanical response of metals to uniaxial and biaxial deformations, the development of substructure in 1100 A1 has been studied over a range of plastic strain for two stress states.Specimens of 1100 aluminum annealed at 350 C were tested in uniaxial (UT) and balanced biaxial tension (BBT) at room temperature to different strain levels. The biaxial specimens were produced by the in-plane punch stretching technique. Areas of known strain levels were prepared for TEM by lapping followed by jet electropolishing. All specimens were examined in a JEOL 200B run at 150 and 200 kV within 24 to 36 hours after testing.The development of the substructure with deformation is shown in Fig. 1 for both stress states. Initial deformation produces dislocation tangles, which form cell walls by 10% uniaxial deformation, and start to recover to form subgrains by 25%. The results of several hundred measurements of cell/subgrain sizes by a linear intercept technique are presented in Table I.

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