Investigation of the Semisolid Rheological Characteristics of AZ91D Alloy

2015 ◽  
Vol 723 ◽  
pp. 742-746
Author(s):  
Xiao Ping Zheng ◽  
Hong Bin Li ◽  
Ze Sheng Ji
Keyword(s):  
Shear Stress ◽  
Solid Fraction ◽  
Rheological Model ◽  
Maximum Shear Stress ◽  
Critical Shear Stress ◽  
Rheological Characteristic ◽  
Solid Particles ◽  
Rheological Characteristics ◽  
Az91d Alloy ◽  
Rheological Test

The semisolid shear rheological characteristic of AZ91D alloy were investigated. The results show that: during the shear rheological test at 570 °C, a critical shear stress and a maximum shear stress are happened. And with holding time increasing, the solid fraction decreasing and the solid particles distributing more uniformly, the rheological rate increases but the critical and maximum shear stress decrease. At last, based on rheological theory, a five-component rheological model of the semisolid AZ91D alloy is established, which is H1 - (N1 / H2) - (N2 / S).

Effect of Holding Time on Rheological Characteristics of the Semisolid Magnesium Alloy

2015 ◽  
Vol 713-715 ◽  
pp. 2663-2666
Author(s):  
Xiao Ping Zheng ◽  
Wei Wen Zhang ◽  
Ming Shao
Keyword(s):  
Shear Stress ◽  
Magnesium Alloy ◽  
Rheological Properties ◽  
Maximum Shear Stress ◽  
Critical Shear Stress ◽  
Solid Particles ◽  
Holding Time ◽  
Rheological Characteristics ◽  
Az91d Alloy ◽  
Rheological Test

The semisolid shear rheological properties of AZ91D alloy were tested. The effect of holding time on the rheological characteristics was investigated. The results show that: during the shear rheological test at 570 °C, a critical shear stress and a maximum shear stress are happened. And with the holding time increasing, solid fraction decreasing and solid particles distributing more uniformly, the rheological rate increases, but the critical shear stress and the maximum shear stress decrease.

Cracking Stress of Nano-Fibers Composite Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 2432-2435 ◽  
Author(s):  
Xin Hua Ni ◽  
Zhan Jun Yao ◽  
Xie Quan Liu ◽  
Jun Ying Wang
Keyword(s):  
Shear Stress ◽  
Tensile Stress ◽  
Volume Fraction ◽  
Slenderness Ratio ◽  
Tensile Force ◽  
Maximum Shear Stress ◽  
Critical Shear Stress ◽  
Composite Ceramics ◽  
The Matrix ◽  
Applied Tensile Stress

Recent experiment showed that nano-fibers composite ceramics, fabricated through SHS process, could acquire high toughening and strengthening. Composite ceramics are mainly composed of fiber eutectic with random orientation, in which nanometer sized zirconia fibers are dispersed within the alumina matrix. First, it can be visualized that tensile force is transmitted from the matrix to the nano-fiber by means of shear stress that develop along the fiber- matrix interface. Then the shear stress on the surface of the fiber eutectic is obtained. It related to the volume fraction and slenderness ratio of the nano-fibers, and external strain of the fiber eutectic. The maximum shear stress is at the ends of the fiber eutectic perpendicular to applied tensile stress. As maximum shear stress on the surface of the fiber eutectic is equal to the critical shear stress, the composite ceramics would crack. So the applied tensile stress on composite ceramics arousing the surface crack of the fiber eutectic is gotten.

Numerical Simulation and Analysis of Interior Shear Stress in Centrifugal Cardio Pump

2013 ◽  
Vol 732-733 ◽  
pp. 426-431
Author(s):  
Xue Bing Dai ◽  
Jian Pu Xu ◽  
Liang Zhang
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Stress Distribution ◽  
Geometric Modeling ◽  
Optimization Design ◽  
Maximum Shear Stress ◽  
Critical Shear Stress ◽  
Flow Distribution ◽  
Shear Stress Distribution ◽  
Recirculation Region

Two centrifugal cardio pumps with recirculation region and anti-recirculation region are designed by speed coefficient method. We can obtain the flow distribution of impeller and inside the shell at design conditions from geometric modeling and numerical simulation of two cardio pumps by using related software, and compared the interior shear stress distribution of two cardio pumps at the same condition. The results show that the maximum shear stress in the cardio pump with the recirculation region is lower about 10% than the pump with the anti-recirculation region and the region of the shear stress is exceed the critical shear stress (150Pa) which produced hemolytic is less about 2/3 than the cardio pump with the anti-recirculation region from the shear stress distribution. As a result a tiny destroys are caused to the blood cell and the pump with the anti-recirculation region model correspond with the demand of the haemophysiology, the research results provide the theory reference and basis in the optimization design for such artificial cardio pump.

Effect of Isothermal Holding Parameters on the Solid Particles Evolution of Semisolid AZ91D Alloy Produced by SIMA

2011 ◽  
Vol 311-313 ◽  
pp. 1901-1905 ◽  
Author(s):  
Qian Qian Zhang ◽  
Zhan Yi Cao
Keyword(s):  
Particle Size ◽  
Solid Particle ◽  
Solid Fraction ◽  
Compression Ratio ◽  
Ostwald Ripening ◽  
Isothermal Holding ◽  
Solid Particles ◽  
Az91d Alloy ◽  
Concentration Gradients ◽  
Increasing Temperature

The paper researched the isothermal time and temperature affects the solid particles evolution of semisolid AZ91D alloy, and the alloy be produced by the method of strain induced melt activation (SIMA) ,and the method of compression ratio is 40%. The research demonstrated that the solid fraction decreased and solid particle size increased when increasing temperature and time. The isothermal coarsening of solid particles obeys Ostwald ripening which depending on the curvature of the interface, thus creating concentration gradients and the diffusion transport of material. As a result, the large particles coarsening and little particles minish even dissolved and creating change of distribution frequency of solid particle size. The fitting curves reveal that the experimental data are well fitted to the coarsening equation. The quantitative analysis of solid fraction and solid particle size demonstrated that the appropriate isothermal holding temperature is 550°C -590°C and corresponding isothermal holding time is (45-60min)-(6-20min) in 40% compression ratio.

scholarly journals Design and Application of an In Situ Test Device for Rheological Characteristic Measurements of Liquefied Submarine Sediments

2021 ◽  
Vol 9 (6) ◽  
pp. 639
Author(s):  
Hong Zhang ◽  
Xiaolei Liu ◽  
Anduo Chen ◽  
Weijia Li ◽  
Yang Lu ◽  
...  
Keyword(s):  
Yellow River ◽  
Rheological Characteristic ◽  
Yellow River Delta ◽  
Turbidity Currents ◽  
Rheological Characteristics ◽  
Submarine Landslides ◽  
Test Device ◽  
Offshore Area ◽  
In Situ Test

Liquefied submarine sediments can easily lead to submarine landslides and turbidity currents, and cause serious damage to offshore engineering facilities. Understanding the rheological characteristics of liquefied sediments is critical for improving our knowledge of the prevention of submarine geo-hazards and the evolution of submarine topography. In this study, an in situ test device was developed to measure the rheological properties of liquefied sediments. The test principle is the shear column theory. The device was tested in the subaqueous Yellow River delta, and the test results indicated that liquefied sediments can be regarded as “non-Newtonian fluids with shear thinning characteristics”. Furthermore, a laboratory rheological test was conducted as a contrast experiment to qualitatively verify the accuracy of the in situ test data. Through the comparison of experiments, it was proved that the use of the in situ device in this paper is suitable and reliable for the measurement of the rheological characteristics of liquefied submarine sediments. Considering the fact that liquefaction may occur in deeper water (>5 m), a work pattern for the device in the offshore area is given. This novel device provides a new way to test the undrained shear strength of liquefied sediments in submarine engineering.

scholarly journals Studying the performance of fully encapsulated rock bolts with modified structural elements

2021 ◽  
Author(s):  
Jianhang Chen ◽  
Hongbao Zhao ◽  
Fulian He ◽  
Junwen Zhang ◽  
Kangming Tao
Keyword(s):  
Shear Stress ◽  
Load Transfer ◽  
Maximum Shear Stress ◽  
Coupling Model ◽  
Numerical Approach ◽  
Rock Bolt ◽  
Structural Elements ◽  
Rock Bolts ◽  
Two Stage ◽  
Bolt Diameter

AbstractNumerical simulation is a useful tool in investigating the loading performance of rock bolts. The cable structural elements (cableSELs) in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical issues. In this study, the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling model. Furthermore, the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current cableSELs. Comparison was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock bolts. Based on the modified cableSELs, the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were studied. The simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter apparently. With the bolt diameter increasing, the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle behaviour. Moreover, after the rock bolt was loaded, the position where the maximum shear stress occurred was variable. Specifically, with the continuous loading, it shifted from the rock bolt loaded end to the other end.

Flow and Thermal Fields in a Pendant Droplet Moving on Lyophobic Surface

2010 ◽  
Author(s):  
Basant Singh Sikarwar ◽  
K. Muralidhar ◽  
Sameer Khandekar
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Reynolds Number ◽  
Shear Stress ◽  
Heat Transfer Coefficient ◽  
Wall Shear Stress ◽  
Transfer Coefficient ◽  
Maximum Shear Stress ◽  
Computational Domain ◽  
Wall Shear

Clusters of liquid drops growing and moving on physically or chemically textured lyophobic surfaces are encountered in drop-wise mode of vapor condensation. As opposed to film-wise condensation, drops permit a large heat transfer coefficient and are hence attractive. However, the temporal sustainability of drop formation on a surface is a challenging task, primarily because the sliding drops eventually leach away the lyophobicity promoter layer. Assuming that there is no chemical reaction between the promoter and the condensing liquid, the wall shear stress (viscous resistance) is the prime parameter for controlling physical leaching. The dynamic shape of individual droplets, as they form and roll/slide on such surfaces, determines the effective shear interaction at the wall. Given a shear stress distribution of an individual droplet, the net effect of droplet ensemble can be determined using the time averaged population density during condensation. In this paper, we solve the Navier-Stokes and the energy equation in three-dimensions on an unstructured tetrahedral grid representing the computational domain corresponding to an isolated pendant droplet sliding on a lyophobic substrate. We correlate the droplet Reynolds number (Re = 10–500, based on droplet hydraulic diameter), contact angle and shape of droplet with wall shear stress and heat transfer coefficient. The simulations presented here are for Prandtl Number (Pr) = 5.8. We see that, both Poiseuille number (Po) and Nusselt number (Nu), increase with increasing the droplet Reynolds number. The maximum shear stress as well as heat transfer occurs at the droplet corners. For a given droplet volume, increasing contact angle decreases the transport coefficients.

Field evidence of resuspension in a mine tailings pond

2001 ◽  
Vol 38 (4) ◽  
pp. 796-808 ◽  
Author(s):  
Celestina Adu-Wusu ◽  
Ernest K Yanful ◽  
Mohammed H Mian
Keyword(s):  
Shear Stress ◽  
Mine Tailings ◽  
Critical Shear Stress ◽  
Field Measurements ◽  
Shear Stresses ◽  
Wind Speeds ◽  
Tailings Pond ◽  
Field Evidence ◽  
Water Cover ◽  
Solubility Of Oxygen

Flooding of tailings under shallow water covers is an effective method of decommissioning potentially acid generating mine tailings. The low diffusivity and solubility of oxygen in water are attractive features of this technology. However, wind-induced waves can resuspend flooded tailings and expose them to greater contact with dissolved oxygen, thereby increasing the potential for oxidation and acid generation. Field measurements of wind activity and waves under different water cover depths and associated resuspension for a mine tailings pond in Ontario are presented and discussed. The results show that wind speeds greater than 8 m/s above water covers that are shallower than 1 m create waves of height greater than 10 cm and bottom shear stresses greater than 0.2 Pa. Under these conditions the critical shear stress of the mine tailings was exceeded, resulting in erosion and subsequent resuspension.Key words: mine tailings, water cover, wind-induced waves, resuspension, wind speed, shear stress.

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