scholarly journals Cooling under Applied Stress Rejuvenates Amorphous Alloys and Enhances Their Ductility

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 67
Author(s):  
Nikolai V. Priezjev
Keyword(s):  
Glass Transition ◽  
Tensile Stress ◽  
Potential Energy ◽  
Applied Stress ◽  
Three Dimensional ◽  
Tensile Tests ◽  
Maximum Tensile Stress ◽  
Amorphous Structure ◽  
Glass Transition Point ◽  
Dynamics Simulations

The effect of tensile stress applied during cooling of binary glasses on the potential energy states and mechanical properties is investigated using molecular dynamics simulations. We study the three-dimensional binary mixture that was first annealed near the glass transition temperature and then rapidly cooled under tension into the glass phase. It is found that at larger values of applied stress, the liquid glass former freezes under higher strain and its potential energy is enhanced. For a fixed cooling rate, the maximum tensile stress that can be applied during cooling is reduced upon increasing initial temperature above the glass transition point. We also show that the amorphous structure of rejuvenated glasses is characterized by an increase in the number of contacts between smaller type atoms. Furthermore, the results of tensile tests demonstrate that the elastic modulus and the peak value of the stress overshoot are reduced in glasses prepared at larger applied stresses and higher initial temperatures, thus indicating enhanced ductility. These findings might be useful for the development of processing and fabrication methods to improve plasticity of bulk metallic glasses.

scholarly journals Knitting Technologies And Tensile Properties Of A Novel Curved Flat-Knitted Three-Dimensional Spacer Fabrics

2015 ◽  
Vol 15 (3) ◽  
pp. 191-197 ◽  
Author(s):  
Xiaoying Li ◽  
Gaoming Jiang ◽  
Xiaolin Nie ◽  
Pibo Ma ◽  
Zhe Gao
Keyword(s):  
Tensile Stress ◽  
Tensile Properties ◽  
Dimensional Stability ◽  
Three Dimensional ◽  
Tensile Tests ◽  
Weft Direction ◽  
Aramid Fibres ◽  
Spacer Fabric ◽  
Fabric Deformation ◽  
Spacer Fabrics

AbstractThis paper introduces a knitting technique for making innovative curved three-dimensional (3D) spacer fabrics by the computer flat-knitting machine. During manufacturing, a number of reinforcement yarns made of aramid fibres are inserted into 3D spacer fabrics along the weft direction to enhance the fabric tensile properties. Curved, flat-knitted 3D spacer fabrics with different angles (in the warp direction) were also developed. Tensile tests were carried out in the weft and warp directions for the two spacer fabrics (with and without reinforcement yarns), and their stress–strain curves were compared. The results showed that the reinforcement yarns can reduce the fabric deformation and improve tensile stress and dimensional stability of 3D spacer fabrics. This research can help the further study of 3D spacer fabric when applied to composites.

scholarly journals Finite Element Simulation and Multi-Factor Stress Prediction Model for Cement Concrete Pavement Considering Void under Slab

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5294
Author(s):  
Bangyi Liu ◽  
Yang Zhou ◽  
Linhao Gu ◽  
Xiaoming Huang
Keyword(s):  
Finite Element ◽  
Tensile Stress ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Mesh Size ◽  
Maximum Tensile Stress ◽  
Concrete Pavement ◽  
Slab Thickness ◽  
Void Size ◽  
Tensile Stresses

Uneven support as result of voids beneath concrete slabs can lead to high tensile stresses at the corner of the slab and eventually cause many forms of damage, such as cracking or faulting. Three-dimensional (3D) finite element models of the concrete pavement with void are presented. Mesh convergence analysis was used to determine the element type and mesh size in the model. The accuracy of the model is verified by comparing with the calculation results of the code design standards in China. The reliability of the model is verified by field measurement. The analysis shows that the stresses are more affected at the corner of the slab than at the edge. Impact of void size and void depth at the slab corner on the slab stress are similar, which result in the change of the position of the maximum tensile stress. The maximum tensile stresses do not increase with the increase in the void size for relatively small void size. The maximum tensile stress increases rapidly with the enlargement in the void size when the size is ≥0.4 m. The increments of maximum tensile stress can reach 183.7% when the void size is 1.0 m. The increase in slab thickness can effectively reduce maximum tensile stress. A function is established to calculate the maximum tensile stress of the concrete slab. The function takes into account the void size, the slab thickness and the vehicle load. The reliability of the function was verified by comparing the error between the calculated and simulated results.

Mechanical Behavior of Segmented Lining Structure of Tunnel under Acting Ground Fractures in Xi’an Zone

2011 ◽  
Vol 261-263 ◽  
pp. 1778-1783
Author(s):  
Sheng Jun Shao ◽  
Fang Tao She ◽  
Juan Fang
Keyword(s):  
Tensile Stress ◽  
Mechanical Behavior ◽  
Compressive Stress ◽  
Three Dimensional ◽  
Vertical Displacement ◽  
Maximum Tensile Stress ◽  
Internal Force ◽  
Subway Tunnel ◽  
Lining Structure ◽  
Pass Through

Xi’an ground fracture, caused by the extraction of groundwater and the movement of fault under soil strata, is a geo-hazard. The movement of ground fracture originates the uneven settlement of upward block and downward block. In Xi’an ground fracture region, the segmented lining structure was adopted in subway tunnel to pass through the ground fracture, so as to adapt for the uneven settlement. Three-dimensional elastic-plastic finite difference method was applied to simulate the initial lining structure, second segmented lining structure, surrounding soils and ground fracture. The horizontal and vertical displacement of segmented lining structure, surrounding soils pressure and internal force of segmented lining structure in subway tunnel were analyzed by the calculation results. The knowledge on mechanical behavior of segmented lining structure passing through an active ground fracture and surrounding soils was shown as following. The relative vertical displacement between segmented lining structure sects beside the ground fracture increases remarkably with the movement of ground fracture, and the segmented lining structure located in upward displaceent block near ground fracture originates notable rotary. Tension or compression deformation occured in the deformation joint between adjacent segmented lining structures near the ground fracture.There was a significant change in the contact pressure of the first sect of lining structure in the upward displace block. Under the same uniform settlement at the bottom of upward diaplacement block, the relativly vertical displacemtn on the surfaceof ground fracture strata without tunnel equals 50cm, but the relativly vertical displacement between adjacent segmented lining structure at ground fracture is 18.2cm on the design level of arch top of lining strcutre. the maximum tensile stress of segmented lining structure is 2.02MPa, the maximum compressive stress of segmented lining is 3.49MPa. In conclusion, segmented lining structure can adapts to the uneven settlement caused by the movement of ground fracture. Though maximum tensile and compressive stress of sengmented lining structure passing through the active ground fracture is bigger than the general lining structure located in soils strata without the ground fracture, the segmented lining structure constructed by the steel fibre concrete can bear with the maximum tensile stress.

scholarly journals Finite element simulation and multi-factor stress prediction model for cement concrete pavement considering void under slab

2021 ◽  
Author(s):  
Liu Bangyi ◽  
Huang Xiaoming
Keyword(s):  
Finite Element ◽  
Tensile Stress ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Maximum Tensile Stress ◽  
Concrete Pavement ◽  
Slab Thickness ◽  
Void Size ◽  
Tensile Stresses ◽  
The Impact

Uneven support as result of voids beneath concrete slabs can lead to high tensile stresses at the corner of the slab and eventually cause many forms of damage, such as cracking or faulting. Three-dimensional (3D) finite element models of the concrete pavement with void are presented. The accuracy of the model is verified by two methods. The analysis shows that the impact of void size and void depth at the slab corner on the slab stress are similar, which result in the change of the position of the maximum tensile stress. The maximum tensile stresses do not increase with the increase of the void size for relatively small void size. The maximum tensile stress increases rapidly with the enlargement in the void size when the size≥0.4m. The increments of maximum tensile stress can reach 183.7% when the void size are 1.0m. The increase of slab thickness can effectively reduce maximum tensile stress. A function is established to calculate the maximum tensile stress of the concrete slab. The function takes into account the void size and the slab thickness. The reliability of the function was verified by comparing the error between the calculated and simulated results.

Measuring and Testing Composite Materials Used in Aircraft Construction

2021 ◽  
Vol 904 ◽  
pp. 161-166
Author(s):  
Tomasz Lusiak ◽  
Andrej Novák ◽  
Michal Janovec ◽  
Martin Bugaj
Keyword(s):  
Composite Materials ◽  
Tensile Stress ◽  
Maximum Stress ◽  
Tensile Tests ◽  
Maximum Tensile Stress ◽  
Aircraft Structure ◽  
Strength Limit ◽  
Reinforced Composite ◽  
Materials Used ◽  
Composite Samples

This paper is focused on the use of special composite materials for the construction of aircraft components. It focuses on measuring and testing the strength of reinforced composite materials used in damaged aircraft parts repairs. To determine the layer required to repair a part of the aircraft, it is necessary to know the strength limit of the material and its parts. The article describes experimental measurements of manufactured composite samples that have been subjected to tensile stress. Aim of the performed tensile tests was to determine the maximum tensile stress that the composite materials are able to transmit until they are damaged. Measurement determining the maximum stress level is important to ensure the required safety of the aircraft structure on which the composite structure was repaired.

scholarly journals Strengthening of columnar-grained freshwater ice through cyclic flexural loading

2020 ◽  
Vol 66 (258) ◽  
pp. 556-566 ◽  
Author(s):  
Andrii Murdza ◽  
Erland M. Schulson ◽  
Carl E. Renshaw
Keyword(s):  
Cyclic Loading ◽  
Flexural Strength ◽  
Tensile Stress ◽  
Applied Stress ◽  
Stress Amplitude ◽  
Crack Nucleation ◽  
Back Stress ◽  
Maximum Tensile Stress ◽  
Reversed Cyclic ◽  
Fundamental Requirement

AbstractSystematic experiments reveal that the flexural strength of freshwater S2 columnar-grained ice loaded normal to the columns increases upon cyclic loading. Specifically, over the range of stress amplitudes 0.1–2.6 MPa the flexural strength increases linearly with increasing stress amplitude. The experiments were conducted upon both reversed and non-reversed cyclic loading over ranges of frequencies from 0.03 to 2 Hz and temperatures from −25 to −3°C. Strengthening can also be imparted through bending-induced creep. The fundamental requirement for strengthening is that the surface that undergoes maximum tensile stress during failure must have been pre-stressed in tension. Flexural strength is governed by crack nucleation. We suggest that the process is resisted by an internal back-stress that opposes the applied stress and builds up through either crystal dislocations piling up or grain boundaries sliding.

DYNAMIC MECHANISM OF LIQUID–GLASS TRANSITION FOR Mg7Zn3 ALLOY

2013 ◽  
Vol 27 (10) ◽  
pp. 1350071 ◽  
Author(s):  
ZHAO-YANG HOU ◽  
RANG-SU LIU ◽  
CHUN-LONG XU ◽  
XIAO-TING LI
Keyword(s):  
Glass Transition ◽  
Potential Energy ◽  
Liquid Glass ◽  
Dynamic Properties ◽  
Dynamic Mechanism ◽  
Relaxation Processes ◽  
Potential Energy Landscape ◽  
Temperature Dependences ◽  
Lower Mobility ◽  
Dynamics Simulations

The dynamic mechanism of liquid–glass transition for Mg 7 Zn 3 alloy is studied by the molecular dynamics simulations. The temperature dependences of dynamic properties during the liquid–glass transition are investigated. Two relaxation processes are clearly observed near the glass transition temperature. The diffusivity deviates from the Arrhenius law after the melting temperature Tm and satisfies the power law before the dynamic singularity temperature Tc owing to the cage effect. The solid- and liquid-like atoms are defined according to the vibration characteristic of atoms. It is found that the solid-like atoms have higher local packing density, lower mobility and potential energy than the liquid-like ones. Based on the evolutions of solid- and liquid-like atoms, the atomic mechanism of dynamic liquid–glass transition is systematically elucidated, which is consistent with the potential energy landscape.

Application of a chamfer slab technology to reduce internal cracks of continuous casting bloom during soft reduction process

2019 ◽  
Vol 116 (6) ◽  
pp. 608 ◽  
Author(s):  
Nanfu Zong ◽  
Hui Zhang ◽  
Minglin Wang ◽  
Zhifang Lu
Keyword(s):  
Shear Stress ◽  
Tensile Stress ◽  
Continuous Casting ◽  
Three Dimensional ◽  
Reduction Process ◽  
Element Model ◽  
Maximum Tensile Stress ◽  
Stress Concentrations ◽  
Soft Reduction ◽  
The Right

The stress concentrations over the brittle temperature range (BTR) in the bloom continuous casting are the main reason of internal cracks. In order to analyze the stress distribution in the BTR of the blooms during soft reduction stage, a three-dimensional thermo-mechanical finite-element model with different corner structures (i.e. chamfer angle and chamfer length) was established. The relationship between corner structures, maximum tensile stress, as well as shear stress is analyzed, and the influence of corner structure of bloom on the internal cracks is studied. The results show that the tensile stress and the shear stress decreased gradually by properly adjusting the chamfer angle and the chamfer length of the bloom. Compared with the use of the right-angle bloom casting, the application of chamfer bloom casting is able to reduce the stress concentration over the BTR, therefore reduces the internal cracks. In addition, as a side benefit, the chamfer bloom casting can save energy required in deforming the bloom during the soft reduction process.

Preparation and characterization of incompletely condensed POSS and its application in RTV composites

2016 ◽  
Vol 49 (2) ◽  
pp. 157-172 ◽  
Author(s):  
Zhanglin Yuan ◽  
Jincheng Wang
Keyword(s):  
Tensile Strength ◽  
Mass Loss ◽  
Mass Loss Rate ◽  
Three Dimensional ◽  
Xrd Analysis ◽  
Tensile Tests ◽  
Amorphous Structure ◽  
Proton Nuclear Magnetic Resonance ◽  
Elongation At Break ◽  
H Nmr

Research on the structure and properties of room-temperature vulcanizated silicone rubber (RTV) composites with a type of incompletely condensed polyhedral oligomeric silsesquioxane (POSS) was conducted. Trisilanolphenyl POSS (TPOSS) was synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), proton nuclear magnetic resonance (1H NMR), and scanning electron microscopy (SEM). FTIR spectra suggested successful bonding of TPOSS. XRD analysis illustrated that POSS exhibited a crystal behavior while TPOSS had an amorphous structure. The chemical shift of 1H NMR at 7.1–7.8 ppm and 3.71–3.73 ppm further confirmed the structure of TPOSS. TPOSS particle was aggregated with large size observed from SEM Then, TPOSS was applied in RTV composites. Properties of RTV/TPOSS composites such as swelling behavior, tensile strength, elongation at break, thermal stability, and flame retardance were researched and compared. Results showed that the TPOSS were beneficial for increasing the cross-linking points and forming the effective three-dimensional networks in RTV composites. Tensile tests revealed that the tensile strength of RTV/TPOSS-3 was 20% higher than that of pure RTV, and the elongation at break of RTV/TPOSS-1 also showed an improvement. Thermogravimetric analysis studies demonstrated that RTV/TPOSS-5 presented the highest values of temperature at 5% mass loss and temperature at maximum mass loss rate of 437.5°C and 573.7°C, respectively. In addition, the residue of RTV/TPOSS-9 increased to 61.0%. Horizontal burning test found that the burning rate with 9% content of TPOSS was strikingly decreased by 66.4% compared with pure RTV.

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