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.

scholarly journals Behavior of Saline Ice under Cyclic Flexural Loading

2020 ◽  
Author(s):  
Andrii Murdza ◽  
Erland M. Schulson ◽  
Carl E. Renshaw
Keyword(s):  
Cyclic Loading ◽  
Flexural Strength ◽  
Stress Amplitude ◽  
Crack Nucleation ◽  
Back Stress ◽  
Lake Ice ◽  
Hit Rate ◽  
Vertical Location ◽  
Dislocation Pileups ◽  
Reversed Cyclic

Abstract. New systematic experiments reveal that the flexural strength of saline S2 columnar-grained ice loaded normal to the columns can be increased upon cyclic loading by about a factor of 1.5. The experiments were conducted using reversed cyclic loading over ranges of frequencies from 0.1 to 0.6 Hz and at a temperature of −10 ºC on saline ice of two salinities: 3.0±0.9 and 5.9±0.6 ‰. Acoustic emission hit rate during cycling increases with an increase of stress amplitude of cycling. Flexural strength of saline ice of 3.0±0.9 ‰ salinity appears to increase linearly with increasing stress amplitude, similar to the behavior of laboratory-grown freshwater ice (Murdza et al., 2020c) and to the behavior of lake ice (Murdza et al., 2020a). The flexural strength of saline ice of 5.9±0.6 ‰ depends on the vertical location of the sample within the thickness of an ice puck; i.e., the strength of the upper layers, which have a lower brine content, was found to be as high as three times that of lower layers. Flexural strength is governed by tensile strength which appears to be controlled by crack nucleation. Cyclic strengthening is attributed to the development of an internal back stress that opposes the applied stress and originates possibly from dislocation pileups. The fatigue life of saline ice is erratic.

scholarly journals Behavior of saline ice under cyclic flexural loading

2021 ◽  
Vol 15 (5) ◽  
pp. 2415-2428
Author(s):  
Andrii Murdza ◽  
Erland M. Schulson ◽  
Carl E. Renshaw
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Flexural Strength ◽  
Stress Amplitude ◽  
Back Stress ◽  
Lake Ice ◽  
Hit Rate ◽  
Vertical Location ◽  
Dislocation Pileups ◽  
Reversed Cyclic

Abstract. New systematic experiments reveal that the flexural strength of saline S2 columnar-grained ice loaded normal to the columns can be increased upon cyclic loading by about a factor of 1.5. The experiments were conducted using reversed cyclic loading over ranges of frequencies from 0.1 to 0.6 Hz and at a temperature of −10 ∘C on saline ice of two salinities: 3.0 ± 0.9 and 5.9 ± 0.6 ‰. Acoustic emission hit rate during cycling increases with an increase in stress amplitude of cycling. Flexural strength of saline ice of 3.0 ± 0.9 ‰ salinity appears to increase linearly with increasing stress amplitude, similar to the behavior of laboratory-grown freshwater ice (Murdza et al., 2020b) and to the behavior of lake ice (Murdza et al., 2021). The flexural strength of saline ice of 5.9 ± 0.6 ‰ depends on the vertical location of the sample within the thickness of an ice puck; i.e., the strength of the upper layers, which have a lower brine content, was found to be as high as 3 times that of lower layers. The fatigue life of saline ice is erratic. Cyclic strengthening is attributed to the development of an internal back stress that opposes the applied stress and possibly originates from dislocation pileups.

scholarly journals Numerical study of contact wire tension affecting dropper stress of a catenary system

2021 ◽  
Vol 13 (3) ◽  
pp. 168781402199504
Author(s):  
Fan He ◽  
Dandan Guo ◽  
Liming Chen
Keyword(s):  
Tensile Stress ◽  
High Speed ◽  
Stress Amplitude ◽  
Numerical Study ◽  
Maximum Tensile Stress ◽  
Wire Tension ◽  
Contact Wire ◽  
Stress Changes ◽  
Response Equation ◽  
Catenary System

Dropper is the key component of in a catenary system and it is prone to fatigue fracture. Dropper stress directly affects the operation safety of high-speed railway. In this paper, a span of dropper in a catenary system is modeled to investigate the effects of contact wire tension on dropper stress. The response equation of contact wire and the theoretical equation of dropper stress are deduced. The initial and boundary conditions of each dropper are determined, and then the stress of each dropper is calculated by the finite difference method using a MATLAB program. The results show that the stress amplitude and the maximum tensile stress of the dropper decrease significantly with the increase of contact wire tension. When the tension is low, the stress changes of dropper near the load location experience three stages: instant rebound, attenuated vibration, and bending compression. However, the attenuation vibration stage disappears when the tension is increased to a certain extent. Therefore, the control of the vibration response of the contact wire can effectively reduce the stress amplitude and the maximum tensile stress of the dropper, so as to improve the working reliability of the dropper.

scholarly journals Multi-Body Dynamics Simulation of Hoisting Wire Rope and Its Stress Analysis

2020 ◽  
Vol 38 (3) ◽  
pp. 485-493
Author(s):  
Zhi Qin ◽  
Qing Huang ◽  
Hongrui Jin ◽  
Hongqian Xue
Keyword(s):  
Tensile Stress ◽  
Cross Section ◽  
Contact Stress ◽  
Stress Amplitude ◽  
Steel Wire ◽  
Geometric Model ◽  
Maximum Tensile Stress ◽  
Wire Rope ◽  
Dynamics Simulation ◽  
The Wire

As a key component of the hoisting system of the crane, the steel wire rope will bear a variety of loading actions such as stretching, bending, vibration and impact in the process of traction hoisting. Therefore, it is important to determinate the dynamic characteristics of the steel wire rope under complex loads and understand the stress-strain state to predict the risk of hoisting operation in advance. This article takes the bridge crane as the engineering background, first, a dynamic model of a steel wire rope lifting system based on ADAMS/Cable was established, and the dynamic stress spectrum of the steel wire rope during the lifting process was calculated and obtained. Secondly, by establishing the geometric model and finite element model of the wire rope, the tensile stress and wire displacement distribution of the wire rope and the contact stress between the wire rope and the pulley and the wires inside the wire rope are analyzed during the lifting process of the crane. The final results show that the instantaneous acceleration of the steel wire rope increases the maximum tensile stress of the steel wire rope by 37% compared with the stable lifting stage at the instant of starting the steel wire rope, causes an increase in the stress amplitude of the wire rope cross section, and the lifting process of the steel wire rope is accompanied by unstable vibration loads. The analysis found that the outermost cross-section of the steel wire rope's outer strand was subjected to the greatest stress, and its local maximum tensile stress amplitude was increased by 56% compared to the stable lifting stage. The contact stress generated by the contact between the steel wire rope and the pulley causes contact wear on the external and internal strands of the steel wire rope, and promotes fatigue fracture of the steel wire rope.

scholarly journals Strengthening ice through cyclic loading

2017 ◽  
Vol 63 (240) ◽  
pp. 663-669 ◽  
Author(s):  
DANIEL ILIESCU ◽  
ANDRII MURDZA ◽  
ERLAND M. SCHULSON ◽  
CARL E. RENSHAW
Keyword(s):  
Stress Concentration ◽  
Cyclic Loading ◽  
Flexural Strength ◽  
Grain Boundary ◽  
Fresh Water ◽  
Grain Boundary Sliding ◽  
Reversed Cyclic Loading ◽  
Induced Stress ◽  
Boundary Sliding ◽  
Reversed Cyclic

ABSTRACTNew experiments reveal that the flexural strength of fresh water, columnar-grained ice loaded normal to the columns may be increased by about a factor of two upon reversed cyclic loading at a frequency of ~0.1 Hz at stress amplitudes of 1.3–2.6 MPa. The effect is explained in terms of a reduction in deformation-induced stress concentration through the activation of grain boundary sliding, which is evident through boundary decohesion.

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.

Comparative study of the effective parameters on residual stress relaxation in welded aluminum plates under cyclic loading

2020 ◽  
Vol 21 (5) ◽  
pp. 505
Author(s):  
Yousef Ghaderi Dehkordi ◽  
Ali Pourkamali Anaraki ◽  
Amir Reza Shahani
Keyword(s):  
Residual Stress ◽  
Cyclic Loading ◽  
Stress Relaxation ◽  
Stress Amplitude ◽  
Cyclic Plasticity ◽  
Mean Stress ◽  
Effective Parameters ◽  
Perfect Plasticity ◽  
Residual Stress Relaxation ◽  
Aluminum Plates

The prediction of residual stress relaxation is essential to assess the safety of welded components. This paper aims to study the influence of various effective parameters on residual stress relaxation under cyclic loading. In this regard, a 3D finite element modeling is performed to determine the residual stress in welded aluminum plates. The accuracy of this analysis is verified through experiment. To study the plasticity effect on stress relaxation, two plasticity models are implemented: perfect plasticity and combined isotropic-kinematic hardening. Hence, cyclic plasticity characterization of the material is specified by low cycle fatigue tests. It is found that the perfect plasticity leads to greater stress relaxation. In order to propose an accurate model to compute the residual stress relaxation, the Taguchi L18 array with four 3-level factors and one 6-level is employed. Using statistical analysis, the order of factors based on their effect on stress relaxation is determined as mean stress, stress amplitude, initial residual stress, and number of cycles. In addition, the stress relaxation increases with an increase in mean stress and stress amplitude.

Behavior of HPFRC Connections for Precast Concrete Frames Under Reversed Cyclic Loading

PCI Journal ◽  
1998 ◽  
Vol 43 (6) ◽  
pp. 58-71 ◽  
Author(s):  
Rosa M. Vasconez ◽  
Antoine E. Naaman ◽  
James K. Wight
Keyword(s):  
Cyclic Loading ◽  
Precast Concrete ◽  
Concrete Frames ◽  
Reversed Cyclic Loading ◽  
Reversed Cyclic

scholarly journals Cyclic strengthening of lake ice

2020 ◽  
pp. 1-4
Author(s):  
Andrii Murdza ◽  
Aleksey Marchenko ◽  
Erland M. Schulson ◽  
Carl E. Renshaw
Keyword(s):  
Flexural Strength ◽  
Fresh Water ◽  
Stress Amplitude ◽  
Fiber Stress ◽  
Lake Ice ◽  
Water Ice ◽  
Outer Fiber

Abstract Further to systematic experiments on the flexural strength of laboratory-grown, fresh water ice loaded cyclically, this paper describes results from new experiments of the same kind on lake ice harvested in Svalbard. The experiments were conducted at −12 °C, 0.1 Hz frequency and outer-fiber stress in the range from ~ 0.1 to ~ 0.7 MPa. The results suggest that the flexural strength increases linearly with stress amplitude, similar to the behavior of laboratory-grown ice.

Effect of operating parameters on functional fatigue characteristics of an Ni-Ti shape memory alloy on partial thermomechanical cycling

2022 ◽  
pp. 1045389X2110722
Author(s):  
Swaminathan Ganesan ◽  
Sampath Vedamanickam
Keyword(s):  
Yield Strength ◽  
Applied Stress ◽  
Stress Level ◽  
Crack Nucleation ◽  
Maximum Temperature ◽  
Thermomechanical Cycling ◽  
Permanent Strain ◽  
A Value ◽  
The Stability ◽  
Cycle Temperature

In this study, the influence of upper cycle temperature (maximum temperature in a cycle) and the magnitude of applied stress on the functional properties of an SMA during partial thermomechanical cycling has been studied. A near-equiatomic NiTi SMA was chosen and tested under different upper cycle temperatures (between martensite finish (Mf) and austenite finish (Af) temperatures) and stress level (below and above the yield strength of the martensite). The upper cycle temperature was varied by controlling the magnitude of the current supply. The results show that a raise in the upper cycle temperature causes the permanent strain to increase and also lowers the stability. However, decreasing the stress imposed to a value lower than the yield strength of the martensite improves cyclic stability. The upper cycle temperature was found to influence the crack nucleation, whereas the applied stress level the crack propagation during partial thermomechanical cycling of SMAs. Therefore, decreasing the upper cycle temperature as well as the magnitude of stress applied to lower than the yield stress of martensite have been found to be suitable strategies for increasing the lifespan of SMA-based actuators during partial thermomechanical cycling.

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