scholarly journals Technological inheritance in metal forming

2020 ◽  
pp. 28-32
Author(s):  
V. А. Ogorodnikov ◽  
T. F. Arkhipova
Keyword(s):  
Stress State ◽  
Metal Forming ◽  
Mechanical Characteristics ◽  
Deformation Gradient ◽  
Practical Significance ◽  
Cold Plastic Deformation ◽  
Ultimate Deformation ◽  
Technological Inheritance ◽  
Technological Heredity ◽  
Stress States

Ogorodnikov V., Arkhipova T. Technological inheritance in metal forming. Material working by pressure. 2020. № 1 (50). Р. 28-32. Technological heredity in metal forming processes is accompanied by hardening, the appearance of residual stresses, a deformation gradient, residual plasticity and a number of other factors that determine the operational properties of the product. The influence of most factors of technological heredity on the mechanical properties of the material of products has been studied, however, the plasticity of a pre-deformed workpiece remains insufficiently studied. For a quantitative assessment, a calculation method is proposed, with the help of which it seems possible to determine the plasticity resource of pre-deformed blanks. The developed calculation apparatus is based on a fracture model based on a tensor description of damage accumulation. It allows for the known mechanical characteristics to predict the plasticity characteristics of pre-deformed blanks at any type of stress state. The proposed method assumes the use of plasticity diagrams, which describe the change in ultimate deformation depending on the stress state indicators. Plasticity diagrams are constructed for materials tested under conditions of linear or plane stress states (tension, compression, torsion). The practical significance of the results is evidenced by the assessment of the plasticity of steeply curved elbows obtained by the method of cold plastic deformation according to a combined scheme, including deforming pulling of a pre-willed workpiece. In this case, the workpiece in the form of a pipe was subjected to plastic bending. The proposed method makes it possible to assess the residual plasticity of the finished bend. A satisfactory convergence of the calculated and experimental data has been revealed.

Short Stress State Questionnaire

2015 ◽  
Vol 31 (1) ◽  
pp. 20-30 ◽  
Author(s):  
William S. Helton ◽  
Katharina Näswall
Keyword(s):  
Stress State ◽  
Factor Structure ◽  
Human Performance ◽  
Self Report ◽  
Confirmatory Factor ◽  
Stress States ◽  
Related Stress ◽  
Using Data ◽  
Task Conditions ◽  
Multiple Samples

Conscious appraisals of stress, or stress states, are an important aspect of human performance. This article presents evidence supporting the validity and measurement characteristics of a short multidimensional self-report measure of stress state, the Short Stress State Questionnaire (SSSQ; Helton, 2004 ). The SSSQ measures task engagement, distress, and worry. A confirmatory factor analysis of the SSSQ using data pooled from multiple samples suggests the SSSQ does have a three factor structure and post-task changes are not due to changes in factor structure, but to mean level changes (state changes). In addition, the SSSQ demonstrates sensitivity to task stressors in line with hypotheses. Different task conditions elicited unique patterns of stress state on the three factors of the SSSQ in line with prior predictions. The 24-item SSSQ is a valid measure of stress state which may be useful to researchers interested in conscious appraisals of task-related stress.

scholarly journals A Study of Yielding and Plasticity of Rapid Prototyped ABS

Mathematics ◽  
2021 ◽  
Vol 9 (13) ◽  
pp. 1495
Author(s):  
Dan-Andrei Șerban ◽  
Cosmin Marșavina ◽  
Alexandru Viorel Coșa ◽  
George Belgiu ◽  
Radu Negru
Keyword(s):  
Experimental Data ◽  
Stress State ◽  
Plastic Flow ◽  
Plane Stress ◽  
Yield Criterion ◽  
Numerical Analyses ◽  
Flow Potential ◽  
Stress States ◽  
State Configuration

In this article, the yielding and plastic flow of a rapid-prototyped ABS compound was investigated for various plane stress states. The experimental procedures consisted of multiaxial tests performed on an Arcan device on specimens manufactured through photopolymerization. Numerical analyses were employed in order to determine the yield points for each stress state configuration. The results were used for the calibration of the Hosford yield criterion and flow potential. Numerical analyses performed on identical specimen models and test configurations yielded results that are in accordance with the experimental data.

Direct measurement of transverse residual strains in aorta

1996 ◽  
Vol 270 (2) ◽  
pp. H750-H759 ◽  
Author(s):  
H. C. Han ◽  
Y. C. Fung
Keyword(s):  
Stress State ◽  
Outer Layer ◽  
Residual Strain ◽  
Longitudinal Axis ◽  
Outer Wall ◽  
Residual Strains ◽  
Stress States ◽  
Sectional Surface ◽  
Thoracic And Abdominal ◽  
Load State

Residual strains were measured in the porcine aorta. Segments were cut from the aorta perpendicular to its longitudinal axis. Microdots of water-insoluble black ink were sprinkled onto the transverse sectional surface of the segments in the no-load state. The segments were then cut radially, and sectional zero-stress states were approached. The coordinates of selected microdots (2-20 microns) were digitized from photographs taken in the no-load state and the zero-stress state. Residual strains in the transverse section were calculated from the displacement of the microdots. The circumferential residual strains on the inner wall and outer wall were calculated from the circumferential lengths in the no-load state and the zero-stress state. Results show that the circumferential residual strain is negative (compressive) in the inner layer of the aortic wall and positive (tensile) in the outer layer, whereas the radial residual strain is tensile in the inner layer and compressive in the outer layer. This residual strain distribution reduces the stress concentration in the aorta under physiological load. The experimental results compared well with theoretical estimations of a cylindrical model. Regional difference of the residual strain exists and is significant (P < 0.01), e.g., the circumferential residual strains on the inner wall of the ascending, descending thoracic, and abdominal regions of the aorta are -0.133 +/- 0.019, -0.074 +/- 0.020, and -0.046 +/- 0.017 (mean +/- SD), respectively. More radial cuts of a segment produced no significant additional strains. This means that an aortic segment after one radial cut can be considered as the zero-stress state.

scholarly journals Stress Triaxiality and Lode Angle Parameter Characterization of Flat Metal Specimen with Inclined Notch

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1627
Author(s):  
Jian Peng ◽  
Peishuang Zhou ◽  
Ying Wang ◽  
Qiao Dai ◽  
David Knowles ◽  
...  
Keyword(s):  
Stress State ◽  
Notch Root ◽  
Stress Triaxiality ◽  
Image Correlation ◽  
Notch Angle ◽  
Strain Evolution ◽  
Metal Specimen ◽  
Lode Angle ◽  
Stress States ◽  
Angle Parameter

The stress state has an important effect on the deformation and failure of metals. While the stress states of the axisymmetric notched bars specimens are studied in the literature, the studies on the flat metal specimen with inclined notch are very limited and the stress state is not clearly characterized in them. In this paper, digital image correlation and finite element simulations are used to study the distribution of strain and stress state, that is stress triaxiality and Lode angle parameter. Flat specimen with inclined notch was tested to extract the full field strain evolution and calculate stress state parameters at three locations: specimen centre, notch root and failure starting point. It is found that compared with the centre point and the notch root, the failure initiation point can better characterize the influence of the notch angle on the strain evolution. Conversely, the centre point can more clearly characterize the effect of the notch angle on stress state, since the stress states at the failure point and the notch root change greatly during the plastic deformation. Then the calculated stress state parameters of the flat metal specimen with inclined notch at the centre point are used in Wierzbicki stress state diagram to establish a relationship between failure mode and stress state.

Investigation of the effect of stress states on hydro-mechanical behaviors of reservoir rock under fluid injection

2021 ◽  
Author(s):  
Qi Li ◽  
Miao He ◽  
Michael Kühn ◽  
Xiaying Li ◽  
Liang Xu
Keyword(s):  
Stress State ◽  
Mechanical Behavior ◽  
Triaxial Compression ◽  
Reservoir Rock ◽  
Fluid Injection ◽  
Differential Stress ◽  
Mechanical Coupling ◽  
Injection Process ◽  
The Difference ◽  
Stress States

&lt;p&gt;Injecting fluid into the formation is an effective solution for improving the permeability and production of a target reservoir. The evaluation of economy and safety of injection process is a challenging issue faced in reservoir engineering [1-2]. As known, the relative magnitude and direction of the principal stresses significantly influence the hydro-mechanical behavior of reservoir rock during fluid injection. However, due to the limitations of current testing techniques, it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions, e.g. triaxial extension stress states [3]. To this end, a series of numerical simulations were carried out on reservoir rock to study the hydro-mechanical changes under different stress states during fluid injection. In this modelling, the saturated rock is first loaded to the target stress state under drainage conditions, and then the stress state is maintained and water is injected from the top end to simulate the reservoir injection process. Particular attention is paid to the difference in hydro-mechanical changes under triaxial compression and extension stresses. This includes the difference of the pore pressure propagation, mean effective stress, volumetric strain, and stress-induced permeability. The numerical results demonstrate that the differential stress will significantly affect the hydro-mechanical behavior of target rock, but the degree of influence is different under the two triaxial stress states. The hydro-mechanical changes caused by the triaxial compression stress states are generally greater than that of extension, but the difference decreases with increasing differential stress, indicating that the increase of the differential stress will weaken the impact of the stress state on the hydro-mechanical response. This study can deepen our understanding of the stress-induced hydro-mechanical coupling process in reservoir injection engineering.&lt;/p&gt;&lt;p&gt;Keywords: Reservoir injection; Subsurface flow; Hydro-mechanical coupling; Stress state; Triaxial experiment modelling&lt;/p&gt;&lt;p&gt;[1] Li, X., Lei, X. &amp; Li, Q. 2016. Injection-induced fracturing process in a tight sandstone under different saturation conditions. Environmental Earth Sciences, 75, 1466, http://doi.org/10.1007/s12665-016-6265-2&lt;/p&gt;&lt;p&gt;[2] Yang, D., Li, Q. &amp; Zhang, L. 2016. Propagation of pore pressure diffusion waves in saturated dual-porosity media (II). Journal of Applied Physics, 119, 154901, http://doi.org/10.1063/1.4946832&lt;/p&gt;&lt;p&gt;[3] Xu, L., Li, Q., Myers, M., Tan, Y., He, M., Umeobi, H.I. &amp; Li, X. 2021. The effects of porosity and permeability changes on simulated supercritical CO&lt;sub&gt;2&lt;/sub&gt; migration front in tight glutenite under different effective confining pressures from 1.5 MPa to 21.5 MPa. Greenhouse Gases: Science and Technology, http://doi.org/10.1002/ghg.2043&lt;/p&gt;

Photoelast Method and Possible Applications of Mathematical Statistics in Prediction of Stress State of Structural Elements

2014 ◽  
Vol 611 ◽  
pp. 405-411 ◽  
Author(s):  
Oskar Ostertag ◽  
Eva Ostertagová ◽  
Peter Frankovský
Keyword(s):  
Stress State ◽  
Stress Concentration ◽  
Stress Field ◽  
Statistical Methods ◽  
Mathematical Statistics ◽  
Structural Elements ◽  
State Development ◽  
Stress States ◽  
Structural Parts

The presented article is dedicated to stress state development while assessing the concentration of stresses in samples with continuously changing notches. These samples represent connecting elements of structural parts. The stress states of selected samples were determined experimentally by means of reflection photoelasticity. This method is suitable mainly for determination of stress state in the whole area in question, predominantly though for the analysis of stress concentration and its gradient in the notched area. Within the method of reflection photoelasticity, a layer was used to analyse the stress field. When loaded, this layer exhibits the ability of temporal birefringence. One of the statistical methods was selected in order to predict the stress state of other samples with bigger notches.

Time Response Stress Analysis of Solid and Reinforced Thin-Walled Structures by Component-Wise Models

2020 ◽  
pp. 2043010
Author(s):  
R. Azzara ◽  
E. Carrera ◽  
M. Filippi ◽  
A. Pagani
Keyword(s):  
Stress State ◽  
Complex Stress ◽  
Time Response ◽  
Modeling Technique ◽  
Integration Scheme ◽  
Structural Domain ◽  
Mode Superposition ◽  
Thin Walled Structures ◽  
Thin Walled ◽  
Stress States

This paper deals with the evaluation of time response analyses of typical aerospace metallic structures. Attention is focussed on detailed stress state distributions over time by using the Carrera Unified Formulation (CUF) for modeling thin-walled reinforced shell structures. In detail, the already established component-wise (CW) approach is extended to dynamic time response by mode superposition and Newmark direct integration scheme. CW is a CUF-based modeling technique which allows to model multi-component structures by using the same refined finite element for each structural component, e.g. stringers, panels, ribs. Component coupling is realized by imposing displacement continuity without the need of mathematical artifices in the CW approach, so the stress state is consistent in the entire structural domain. The numerical results discussed include thin-walled open and closed section beams, wing boxes and a benchmark wing subjected to gust loading. They show that the proposed modeling technique is effective. In particular, as CW provides reach modal bases, mode superposition can be significantly efficient, even in the case of complex stress states.

scholarly journals Limiting stress states in granular avalanches

1998 ◽  
Vol 26 ◽  
pp. 272-276 ◽  
Author(s):  
Y.C. Tai ◽  
J.M.N.T. Gray
Keyword(s):  
Stress State ◽  
Numerical Methods ◽  
Granular Material ◽  
Laboratory Experiments ◽  
Complex Geometry ◽  
The Other ◽  
Two Dimensional ◽  
Singular Surfaces ◽  
Rapid Convergence ◽  
Stress States

The Savage-Hutter theory for granular avalanches assumes that the granular material is in either of two limiting stress states, depending on whether the motion is convergent or divergent. At transitions between convergent and divergent regions, a jump in stress occurs, which necessarily implies that there is a jump in the avalanche velocity and/or its thickness. In this paper, a regularizaron scheme is used, which smoothly switches from one stress state to the other, and avoids the generation of such singular surfaces. The resulting algorithm is more stable than previous numerical methods but shocks can still occur during rapid convergence in the run-out zone. Results are presented from two-dimensional calculations on complex geometry which illustrate that some necking features observed in laboratory experiments can be explained by the regularized Savage-Hutter model.

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