Effect of Additional Shear Stress on Microstructure Evolution of AZ31 Sheet by Differential Speed Rolling

2015 ◽  
Vol 816 ◽  
pp. 433-438 ◽  
Author(s):  
Yu Teng Shen ◽  
Xin Ran Ou ◽  
Ze Jun Chen
Keyword(s):  
Shear Stress ◽  
Magnesium Alloys ◽  
Microstructure Evolution ◽  
Speed Ratio ◽  
Stress And Strain ◽  
Asymmetric Rolling ◽  
Az31 Sheet ◽  
Differential Speed Rolling ◽  
Shear Stress And Strain ◽  
Differential Speed

Asymmetric rolling of deformed magnesium alloys sheet can accelerate refine the grain size, reduce the basal texture, and improve the subsequent formability. This happens because the additional shear stress and strain are introduced during the differential speed rolling. This paper investigates the relationship of shear stress and microstructure evolution by the experiment in conjunction with the FEM (Finite Element Method) simulation. The differential speed ratio (1, 1.2 and 1.5) and rolling reduction (8% and 15%) were executed at room temperature. The additional shear strain field is simulated for corresponding asymmetric rolling conditions. The results showed that the additional shear stress and strain were the essential influence factors of microstructure evolution and formability of AZ31 sheet for the differential speed rolling. It is helpful in enhancing and improving the formability of rolled magnesium alloys.

An Energy Approach to the Mechanics of Discontinuous Chip Formation

1964 ◽  
Vol 86 (2) ◽  
pp. 157-162 ◽  
Author(s):  
W. K. Luk ◽  
R. C. Brewer
Keyword(s):  
Shear Stress ◽  
Shear Strain ◽  
Normal Stress ◽  
Chip Formation ◽  
Strain Energy ◽  
Energy Condition ◽  
Stress And Strain ◽  
Rupture Plane ◽  
Shear Stress And Strain ◽  
Shear Strain Energy

After briefly reviewing previous work in this field, the authors propose that rupture of the chip work contact (to give a discontinuous chip) is governed by a limiting shear strain energy condition. Assuming that shear stress and strain at rupture are dependent on the compressive normal stress, a criterion for the direction of the rupture plane is deduced. Using some results given by Field and Merchant, the authors then compare their calculated direction of rupture with that experimentally observed. Some indication that the agreement is not entirely fortuitous is afforded by checking the calculated shear strain energy at fracture with that calculated from force and chip measurements.

Influences of Rolling Conditions on Texture and Mechanical Properties of AZ31 Magnesium Alloy Processed by Differential Speed Rolling

2007 ◽  
Vol 561-565 ◽  
pp. 287-290
Author(s):  
Kazutaka Suzuki ◽  
Xin Sheng Huang ◽  
Akira Watazu ◽  
Ichinori Shigematsu ◽  
Naobumi Saito
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Rolling Direction ◽  
Rolling Temperature ◽  
Az31 Magnesium Alloy ◽  
Speed Ratio ◽  
Shear Direction ◽  
Differential Speed Rolling ◽  
Press Formability ◽  
Differential Speed

It was reported that the cold and warm press formability of the magnesium alloy was improved by the application of a differential speed rolling (DSR). However, it can be considered that the microstructure and the texture of the DSR processed sheets greatly change with the rolling conditions. In this study, commercial AZ31B magnesium alloy extrusions were processed by DSR at a differential speed ratio of 1.167 and a reduction per pass of 10% or less, and the effects of the rolling temperature, the number of rolling passes and reversal of the rolling direction on texture and mechanical properties were examined. As a result, it was found that the optimal rolling temperature in terms of the workability and formability of the material was 573 K. And the elongation and formability were maximal in sheets processed by 4–6 passes of DSR. Moreover, reversing the shear direction made the microstructure more homogeneous and finer than unidirectional shear, and improved the mechanical properties and formability. This improvement was greater in samples where the shear direction was reversed once in the middle than where it was reversed for each pass.

Strain distribution over plaques in human coronary arteries relates to shear stress

2008 ◽  
Vol 295 (4) ◽  
pp. H1608-H1614 ◽  
Author(s):  
Frank J. H. Gijsen ◽  
Jolanda J. Wentzel ◽  
Attila Thury ◽  
Frits Mastik ◽  
Johannes A. Schaar ◽  
...  
Keyword(s):  
Shear Stress ◽  
Coronary Arteries ◽  
Plaque Rupture ◽  
Stress And Strain ◽  
Shear Stresses ◽  
High Shear ◽  
High Shear Stress ◽  
Plaque Composition ◽  
Downstream Region ◽  
Shear Stress And Strain

Once plaques intrude into the lumen, the shear stress they are exposed to alters with hitherto unknown consequences for plaque composition. We investigated the relationship between shear stress and strain, a marker for plaque composition, in human coronary arteries. We imaged 31 plaques in coronary arteries with angiography and intravascular ultrasound. Computational fluid dynamics was used to obtain shear stress. Palpography was applied to measure strain. Each plaque was divided into four regions: upstream, throat, shoulder, and downstream. Average shear stress and strain were determined in each region. Shear stress in the upstream, shoulder, throat, and downstream region was 2.55 ± 0.89, 2.07 ± 0.98, 2.32 ± 1.11, and 0.67 ± 0.35 Pa, respectively. Shear stress in the downstream region was significantly lower. Strain in the downstream region was also significantly lower than the values in the other regions (0.23 ± 0.08% vs. 0.48 ± 0.15%, 0.43 ± 0.17%, and 0.47 ± 0.12%, for the upstream, shoulder, and throat regions, respectively). Pooling all regions, dividing shear stress per plaque into tertiles, and computing average strain showed a positive correlation; for low, medium, and high shear stress, strain was 0.23 ± 0.10%, 0.40 ± 0.15%, and 0.60 ± 0.18%, respectively. Low strain colocalizes with low shear stress downstream of plaques. Higher strain can be found in all other plaque regions, with the highest strain found in regions exposed to the highest shear stresses. This indicates that high shear stress might destabilize plaques, which could lead to plaque rupture.

scholarly journals Energy dissipation and liquefaction at Port Island, Kobe

1998 ◽  
Vol 31 (1) ◽  
pp. 33-50 ◽  
Author(s):  
R. O. Davis ◽  
J. B. Berrill
Keyword(s):  
Shear Stress ◽  
Energy Dissipation ◽  
Shear Strain ◽  
Pore Pressure ◽  
Calculation Method ◽  
Horizontal Plane ◽  
Dissipated Energy ◽  
Stress And Strain ◽  
Shear Stress And Strain ◽  
Reclaimed Soils

The Port Island, Kobe downhole records from the Hyogo-ken Nanbu earthquake are analysed to obtain approximate histories of shear stress, shear strain and dissipated energy at a range of depths. Our calculation method relies on measured accelerations in the horizontal plane to produce horizontal components of shear stress and strain using instantaneous modal superposition. A simple dissipated energy-dynamic pore pressure relationship is used to model the development of pore pressure leading to liquefaction. The results show a rapidly developing zone of liquefaction which initiates at a depth of roughly 15 metres in the Port Island reclaimed soils.

A Simplified Approach to Joint Shear Behavior Prediction of RC Beam-Column Connections

2012 ◽  
Vol 28 (3) ◽  
pp. 1071-1096 ◽  
Author(s):  
Jaehong Kim ◽  
James M. LaFave
Keyword(s):  
Shear Stress ◽  
Parameter Estimation ◽  
Estimation Method ◽  
Stress And Strain ◽  
Rc Beam ◽  
Peak Response ◽  
Experimental Database ◽  
Key Points ◽  
Shear Stress And Strain ◽  
Joint Shear

An extensive experimental database of reinforced concrete (RC) beam-column connections subjected to cyclic lateral loading has been constructed. All cases within the database experienced joint shear failure, either in conjunction with or without yielding of longitudinal beam reinforcement, representing damage within a joint panel that was the main contributor to total lateral deformation. (Cases having damage within a joint panel caused by other premature failure modes (e.g., anchorage failure) are not included in the database.) Using the experimental database, envelope curves of joint shear stress vs. strain behavior were developed by connecting key points such as cracking, yielding, and peak loading. Joint shear stress and strain models at peak response have been developed by a Bayesian parameter estimation method based on the experimental database. At other key points, important influence parameters are also identified by constructing joint shear stress and strain models in conjunction with the Bayesian parameter estimation method. Then, a complete RC joint shear stress vs. strain model (including post-peak behavior) is suggested using simplified joint shear stress and strain models at peak response; effects of key parameters on the suggested behavior models are evaluated. Finally, the ASCE/SEI 41 joint shear behavior model has been examined using the constructed database—specific joint shear strength factors and plastic joint shear deformation values are recommended for use when following that approach.

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