scholarly journals Stability Characteristics and Mechanism of U-Shaped Metal Bellows under Symmetrical Cyclic Tension and Compression Process

Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2451
Author(s):  
Zengliang Hao ◽  
Biao Yao ◽  
Yuhang Chen ◽  
Junting Luo
Keyword(s):  
Grain Boundary ◽  
Testing Machine ◽  
Axial Stiffness ◽  
Compression Process ◽  
Forward Movement ◽  
Boundary Area ◽  
Wave Trough ◽  
Cyclic Tension ◽  
Tension And Compression ◽  
Metal Bellows

The U-shaped metal bellows expansion joint compensates for the pipeline displacement by its own deformation. The compensation performance of the metal bellows in the initial stage of tension and compression deformation is unstable. In this paper, the symmetrical cyclic tension and compression (SCTC) process of metal bellows was simulated by ABAQUS software. Then, the SCTC process experiment of metal bellows was completed on the universal material testing machine. The distribution law of axial load with displacement and that of axial stiffness and yield load with cycles of metal bellows were obtained. Finally, the X-ray diffraction peak confirmed the deformation-induced martensite in the wave trough and proved that the plastic strain and hardness values of metal bellows increased with the displacement amplitude. The microstructure in the wave trough area was observed by a Zeiss microscope, and the stability characteristics mechanism of the metal bellows was revealed. The martensite in the wave trough increases the grain boundary area under SCTC loading. The forward movement of the slip band in the grain caused by large deformation reached an equilibrium state with the resistance at the grain boundary, which promotes the macroscopic mechanical properties of the metal bellows to be stable characteristics under SCTC loading.

Mechanical Properties Comparison of Different La Content in AZ91

2014 ◽  
Vol 620 ◽  
pp. 67-72 ◽  
Author(s):  
Yan Yan Zhang ◽  
Chun Xia He ◽  
Hang Song Yang ◽  
Jian Xiu Liu
Keyword(s):  
Magnesium Alloy ◽  
Mechanical Performance ◽  
Testing Machine ◽  
Powder Metallurgy Method ◽  
Az91 Magnesium Alloy ◽  
Compression Performance ◽  
Hardness Tester ◽  
Mechanics Performance ◽  
Tension And Compression ◽  
Az91 Magnesium

In order to improve the comprehensive mechanics performance of AZ91 magnesium alloy which is used as car's material, the La element was added in AZ91 magnesium alloy and specimens was prepared by powder metallurgy method. The influence of La on microstructure, hardness and compression performance of AZ91 a magnesium alloy specimen was studied using metallographic electronic microscope, hardness tester, universal tension and compression testing machine. The experimental results show that when amount of La's addition is 1.2%, its mechanical performance is best, hardness is 67.1 HV, compressive strength is 115.8 MPa, increased respectively by 20.0% and 29.5% compared the AZ91 magnesium alloy substrate, and the grain refinement effect of AZ91 magnesium alloy is the best at this time.

Rapid cycle-dependent softening of equal channel angularly pressed Sn–Ag–Cu alloy

2008 ◽  
Vol 23 (10) ◽  
pp. 2630-2638 ◽  
Author(s):  
Q.S. Zhu ◽  
Z.G. Wang ◽  
Q.L. Zeng ◽  
S.D. Wu ◽  
J.K. Shang
Keyword(s):  
Grain Boundary ◽  
Cast Alloy ◽  
Intermetallic Phase ◽  
Crack Density ◽  
Sharp Decrease ◽  
Surface Damage ◽  
Cyclic Stress ◽  
Grain Boundary Sliding ◽  
Cyclic Softening ◽  
Boundary Area

Cyclic stress–strain response of an equal channel angularly pressed Sn-3.8Ag-0.7Cu alloy was investigated to seek a mechanistic understanding of cyclic softening in Sn-rich alloys. The equal channel angular pressing (ECAP) was applied to modify the microstructure of the solder alloy by breaking up the needlelike Ag3Sn intermetallic phase into fine granules and by reducing the large β-Sn dendrites into smaller and equiaxed grains. The extruded alloys were subjected to strain-controlled fatigue test at various strain amplitudes. It was found that the extruded alloy exhibited a sharp decrease of the stress amplitude within the initial few cycles compared with the as-cast alloy. After only a few cycles, the alloy suffered from noticeable surface damage. In situ scanning electron microscopy observations of the cyclic bending specimens revealed an approximately logarithmic relationship between crack density and the number of cycles. A theoretical model of microcrack accumulation was constructed to explain the rapid cyclic softening behavior. The predicted results, based on the model, agreed well with the experimental data and indicated that the rapid softening had resulted from an increased tendency for grain boundary cracking in the ECAPed microstructure due to the increase in the grain boundary area per unit volume and the reduced resistance of Ag3Sn to grain boundary sliding.

scholarly journals Out-of-plane instability of reinforced masonry uniaxial specimens under reversed cyclic axial loading

2017 ◽  
Vol 44 (5) ◽  
pp. 367-376 ◽  
Author(s):  
Nazli Azimikor ◽  
Svetlana Brzev ◽  
Kenneth J. Elwood ◽  
Donald L. Anderson ◽  
William McEwen
Keyword(s):  
Axial Loading ◽  
Shear Walls ◽  
Reinforcement Ratio ◽  
Design Parameters ◽  
Key Factors ◽  
Cyclic Tension ◽  
Reinforced Masonry ◽  
Out Of Plane ◽  
Tension And Compression ◽  
Reversed Cyclic

Results of a study performed on the out-of-plane instability of reinforced masonry shear walls (RMSW) under seismic loading are presented. The study was conducted to gain understanding of the out-of-plane instability mechanism and the key factors influencing its development through the testing of five reinforced masonry uniaxial specimens under reversed cyclic tension and compression. The specimens represented the end zone of a RMSW. The design parameters considered in the study included longitudinal reinforcement ratio and height-to-thickness ratio for the test specimens. It was found that onset of out-of-plane instability is strongly influenced by the level of tensile strains developed in the specimens, the reinforcement ratio, and the bar size. In this case, out-of-plane instability occurred when out-of-plane displacements exceeded the critical value equal to half the wall thickness. A study on full-scale RMSW specimens subjected to reversed cyclic loading, also undertaken under this research program, is expected to verify the findings of this study and contribute towards development of design criteria for out-of-plane stability of RMSW.

scholarly journals Influence of Inter-Pass Cooling on Microstructural Evolution and Plastic Deformation of Heavy EH47 Plates

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1686
Author(s):  
Junyu Wu ◽  
Bin Wang ◽  
Bingxing Wang ◽  
R. D. K. Misra ◽  
Zhaodong Wang
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Microstructural Evolution ◽  
Volume Fraction ◽  
Uniform Elongation ◽  
Hexagonal Structure ◽  
Tensile Fracture ◽  
Boundary Area ◽  
Plastic Deformation Behavior ◽  
Deformation Pass

Herein, the influence of inter-pass cooling (IC) and conventional two-stage rolling (CTR), on microstructural evolution and plastic deformation behavior of ultra-heavy EH47 plates, is demonstrated. It is reported that the deformation amount and deformation rate, in every deformation pass during rough rolling, at 1/4- and 1/2-thickness of IC steel were higher than the CTR steel. The volume fraction of ferrite and acicular ferrite was 45% and 18%, at 1/4-thickness, and 35% and 50% at 1/2-thickness of IC steel, respectively, whereas the sum of both ferrite phases was smaller than 25% in the CTR steel. The austenite grain boundary area and high-angle grain boundary fraction in the IC steel were higher than the CTR steel. The high density of fine and shapeless pearlite has been observed in IC steel, whereas large-size carbides, with hexagonal structure, have been observed in CTR steel. Compared to the CTR steel, the density of precipitates was apparently lower in IC steel. Two kinds of Nb containing precipitates, such as (Ti, Nb)(C, N) and (Nb, Ti)C, were observed in the tested steels. Total ductility and uniform elongation of the IC steel were higher than the CTR steel. During the tensile process, the crack initiation energy and crack propagation energy of the IC steel were higher than the CTR steel. Moreover, the volume fraction of retained austenite (FCC) was reduced from 7.71% to 0.42% near the tensile fracture in IC steel at 1/4-thickness. In additon, the strain of synergetic plastic deformation of the IC steel was higher than the CTR steel. Meanwhile, compared to the CTR steel, the synergetic plastic deformation of the IC steel occurred at low stress after the yield point, which can be ascribed to the presence of fewer microcracks in the IC steel. Hence, a delayed fracture has been observed in the IC steel plate.

Grain Size and Chemical Composition Effects on the Grain Boundary Resistance of Ceria

2002 ◽  
Vol 730 ◽  
Author(s):  
Xiao-Dong Zhou ◽  
Harlan U. Anderson ◽  
Wayne Huebner
Keyword(s):  
Electrical Conductivity ◽  
Grain Size ◽  
Grain Boundary ◽  
Boundary Resistance ◽  
Impedance Spectra ◽  
Total Resistance ◽  
Boundary Area ◽  
Oxygen Ions ◽  
Composition Effects ◽  
Increasing Temperature

AbstractStudies related to the effects of grain size (30nm – 5.0μm) on the electrical conductivity of undoped CeO2 and Ce0.90Gd0.10O1.95 were performed. A series of impedance spectra as a function of temperature and grain size were analyzed. It was found that the ratio of the grain boundary resistance to the total resistance became lower with decreasing grain size, increasing temperature or increasing Gd content. For the case of Gd doped CeO2, the source of the grain boundary resistance may be due to the trapping of oxygen ions in the grain boundary area.

scholarly journals Modeling of Linear and Non-linear Compression Processes of Sunflower Bulk Oilseeds

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2999 ◽  
Author(s):  
Abraham Kabutey ◽  
David Herak ◽  
Himsar Ambarita ◽  
Riswanti Sigalingging
Keyword(s):  
Testing Machine ◽  
Processing Parameters ◽  
Screw Press ◽  
Small Scale ◽  
Compression Process ◽  
Deformation Curves ◽  
Universal Compression ◽  
Oil Expression ◽  
Theoretical Pressure ◽  
Linear Compression

The present study aimed at describing the experimental and theoretical force-deformation curves of sunflower bulk oilseeds at varying initial pressing heights and vessel diameters as well as determining the theoretical pressure and energy along the screw press FL 200 pressing chambers. The design of efficient oil expression systems for industry and small-scale application remains a major challenge to engineers and researchers. In attempting to solve the problem, it is important to understand the linear compression process and to transfer the knowledge to the industry involving mechanical screw presses. The universal compression testing machine at a preset load of 200 kN and a speed of 5 mm·min−1, tangent curve model and the screw press FL 200 geometry parameters were applied. The obtained results of pressure and energy along the screw pressing chambers (1–7) ranged from 0.31 to 101.653 MPa and 12.616 to 1231.228 J. Applying the tangent model at n = 1 and n = 2, the cumulative pressure decreased with increasing vessel diameters while energy increased. The study provides useful information for the analysis of other bulk oilseeds and optimizing the processing parameters of screw press FL 200 and the design and development of new oil presses.

Effect of Hydrostatic Pressure on Nano Crystalline Materials Behavior

2012 ◽  
Vol 18-19 ◽  
pp. 27-42 ◽  
Author(s):  
Reza Jafari Nedoushan ◽  
Mahmoud Farzin
Keyword(s):  
Grain Size ◽  
Hydrostatic Pressure ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Crystalline Materials ◽  
Nano Crystalline ◽  
Tension And Compression ◽  
Boundary Sliding ◽  
Tension Compression Asymmetry ◽  
Effect Of Hydrostatic Pressure

One of the Remarkable Differences between Mechanical Behavior of Nano-Crystalline and Coarse-Grained Materials Is Tension Compression Asymmetry that Has Been Experienced in Nano-Crystalline Materials. In this Paper a Constitutive Model Is Proposed which Considers Dominant Operative Deformation Mechanisms of Nano-Crystalline Materials Including Grain Interior Plasticity, Grain Boundary Diffusion and Grain Boundary Sliding. A Grain Size Dependent Taylor Type Polycrystalline Model Is Used to Predict Grain Interior Deformation. Three Dimensional Relationships Are Proposed to Relate Macro Stress and Strain Rate in Grain Boundary Mechanisms. The Effect of Normal Stress Acting on a Boundary Is Also Considered in Grain Boundary Sliding, Therefore, Effect of Hydrostatic Pressure Is Included in the Model. The Proposed Model Is Used to Predict Strength of Nano-Crystalline Copper in both Tension and Compression and Good Results Are Obtained Comparing with Experimental Data. The Model Also Predicts Various Behaviors of Nano-Crystalline Materials Observed in Literature's Experiments and Molecular Dynamic Simulations. Some Examples Are: Inverse Hall-Petch Effect; Tension and Compression Maximum Strength Grain Sizes; Tension Compression Asymmetry and its Change Vs. Grain Size and Strain Rate and the Yield Locus Shape.

Simulation of the Kinetics of Grain-Boundary Nucleated Phase Transformations

2011 ◽  
Vol 172-174 ◽  
pp. 1128-1133 ◽  
Author(s):  
Eric A. Jägle ◽  
Eric J. Mittemeijer
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Phase Transformations ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Kinetic Models ◽  
Micro Structure ◽  
Boundary Area ◽  
Random Nucleation ◽  
Kinetics Of

The kinetics of phase transformations for which nucleation occurs on parent-micro-structure grain boundaries, and the resulting microstructures, were investigated by means ofgeometric simulations. The influences of parent microstructure grain-boundary area density,parent grain-size distribution and parent→product kinetics were analysed. Additionally, thesimulated kinetics were compared with predictions from two kinetic models, namely a modelproposed for spatially random nucleation and a model proposed for grain-boundary nucleation.It was found that the simulated transformed fraction as function of time lies in between the twomodel predictions for all investigated parent microstructures and parent→product kinetics.

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