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 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 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 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.

scholarly journals Experimental Study on Acoustic Emission and Resistivity Response of Sandstone under Constant Amplitude Cyclic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Kui Wang ◽  
Xue Li ◽  
Zheng Huang ◽  
Mingjie Zhao
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Cyclic Load ◽  
Stress Amplitude ◽  
Rate Of Change ◽  
Rapid Decline ◽  
Engineering Practice ◽  
Loading Frequency ◽  
Constant Amplitude ◽  
Ae Signal

A lot of engineering practice shows that, during the construction and operation of rock mass projects, in addition to the static load, the rock is more subjected to cyclic load. Constant amplitude cyclic load is one of the simpler cyclic loading methods. The damage of rocks gradually accumulates under the action of periodic cyclic load, and finally, fatigue damage occurs, which affects the stability of the project. Therefore, it is necessary to study the mechanical properties of the rock under the action of constant amplitude cyclic load. Acoustic emission (AE) parameters and resistivity are both sensitive to the damage process of the rock and can well describe the damage evolution law of the rock. Under the action of constant amplitude cyclic loading, different loading conditions, different state specimens, and so on, factors will make a big difference to the AE signal and resistivity, such as the difference in stress amplitude, loading rate, and saturation. Therefore, in this paper, the typical sandstone in the Chongqing area is taken as the research object, the AE characteristics and resistivity characteristics of sandstone under different test conditions such as different stress amplitude, different loading frequency, and different saturation are tested, and the evolution of AE is found. It also has a three-stage rule: in the initial stage, the deformation is faster and the AE signal is strong; in the constant velocity stage, the deformation develops slowly and the AE signal is also stable; in the acceleration stage, the deformation develops sharply and the AE signal also becomes more intense. With the increase of cyclic loading stress amplitude, or the decrease of cyclic loading frequency, or the decrease of rock sample saturation, the acoustic emission signal generated in each cycle will be stronger. The resistivity as a whole shows a rapid decline in the loading phase and a rapid rebound in the unloading phase. The changes in resistivity at different stress amplitudes show differences in the first few cycles; the overall change trend of resistivity at different frequencies is consistent, but the rate of change increases with decreasing frequency, and the variation trend of resistivity is very different under different saturation.

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.

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

Electrical Resistance and Acoustic Emission During Fatigue Testing of Pristine and High Velocity Impact SiC/SiC Composites at Room and Elevated Temperature

2016 ◽  
Author(s):  
Zipeng Han ◽  
Gregory N. Morscher ◽  
Emmanuel Maillet ◽  
Manigandan Kannan ◽  
Sung R. Choi ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Acoustic Emission ◽  
Cyclic Loading ◽  
Electrical Resistance ◽  
Fatigue Testing ◽  
Early Stage ◽  
Loading Conditions ◽  
Initial Attempt ◽  
Matrix Cracks ◽  
Sic Composites

Electrical resistance (ER) is a relatively new approach for real-time monitoring and evaluating damage in SiC/SiC composites for a variety of loading conditions. In this study, ER of woven silicon carbide fiber-reinforced silicon carbide composite systems in their pristine and impacted state were measured under cyclic loading conditions at room and high temperature (1200C). In addition, modal acoustic emission (AE) was also monitored, which can reveal the occasion of matrix cracks and fiber. ER measurement and AE technique are shown in this study to be useful methods to monitor damage and indicate the failure under cyclic loading. Based on the slope of the ER evolution, an initial attempt has been made to develop a method allowing a critical damage phase to be identified. While the physical meaning of the critical point is not yet clear, it has the potential to allow the failure to be indicated at its early stage.

Damage Characterization in Glass/Epoxy Composite Laminates under Normal and Oblique Planes of Cyclic Indentation Loading with AE Monitoring

2021 ◽  
Vol 79 (1) ◽  
pp. 61-77
Author(s):  
A Jayababu ◽  
V Arumugam ◽  
B Rajesh ◽  
C Suresh Kumar
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Cyclic Loading ◽  
Composite Laminates ◽  
Epoxy Composite ◽  
Damage Resistance ◽  
Damage Initiation ◽  
Residual Compressive Strength ◽  
Cyclic Indentation ◽  
Indentation Damage

This work focuses on the experimental investigation of indentation damage resistance in different stacking sequences of glass/epoxy composite laminates under cyclic loading on normal (0°) and oblique (20°) planes. The stacking sequence, such as unidirectional [0]12, angle ply [±45]6S, and cross ply [0/90]6S, were subjected to cyclic indentation loading and monitoring by acoustic emission testing (AE). The laminates were loaded at the center using a hemispherical steel indenter with a 12.7 mm diameter. The cyclic indentation loading was performed at displacements from 0.5 to 3 mm with an increment of 0.5 mm in each cycle. Subsequently, the residual compressive strength of the post-indented laminates was estimated by testing them under in-plane loading, once again with AE monitoring. Mechanical responses such as peak load, absorbed energy, stiffness, residual dent, and damage area were used for the quantification of the indentation-induced damage. The normalized AE cumulative counts, AE energy, and Felicity ratio were used for monitoring the damage initiation and propagation. Moreover, the discrete wavelet analysis of acoustic emission signals and fast Fourier transform enabled the calculation of the peak frequency content of each damage mechanism. The results showed that the cross-ply laminates had superior indentation damage resistance over angle ply and unidirectional (UD) laminates under normal and oblique planes of cyclic loading. However, the conclusion from the results was that UD laminates showed a better reduction in residual compressive strength than the other laminate configurations.

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