scholarly journals Effects of Constant Amplitude Cyclic Loading on the Nonuniform Deformation of Sandstone Specimens

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Xiao-Bin Yang ◽  
Xin-Xing Han ◽  
Xiao-Yao Wang ◽  
Zi-Peng Zhang
Keyword(s):  
Cyclic Loading ◽  
Stress Condition ◽  
Mechanical Response ◽  
Correlation Method ◽  
Image Correlation ◽  
Constant Amplitude ◽  
Nonuniform Deformation ◽  
Evolution Stage ◽  
Number Of Cycles ◽  
Cyclic Loading Tests

In order to explore the mechanical response mechanism of rock materials under cyclic loading, uniaxial constant amplitude cyclic loading tests for sandstone specimens were carried out. The images of specimen deformation during the tests were captured by charge-coupled device (CCD) cameras. Based on the digital image correlation method (DICM), the evolution laws of nonuniform deformation and displacements around localization bands during cyclic loading were investigated. The experimental results show that, during the cyclic loading process, the nonuniform deformation continually escalates with the number of cycles increasing and fluctuates with the cyclic loading stress condition; the nonuniform deformation lags behind the variation of loading stress; and the whole nonuniform deformation experiences a slow evolution stage and a fast evolution stage. At the loading stage or unloading stage, the nonuniform deformation of rock deteriorates with the number of cycles increasing under the same stress condition. In each loading cycle, the nonuniform deformation at the unloading stage is more than that at the loading stage under the same stress condition. The time of dislocation displacements and tension displacements meets hysteresis, compared with the time of stress change. In addition, the dislocation displacements and tension displacements around localization bands in general increase with the number of cycles increasing. The displacement evolution around localization bands has the same hysteresis and accumulation laws as that of nonuniform deformation.

scholarly journals INELASTIC RESPONSES OF SWOLLEN NITRILE RUBBER UNDER CYCLIC LOADING

2018 ◽  
Vol 91 (1) ◽  
pp. 136-150 ◽  
Author(s):  
Mei Sze Loo ◽  
Jean Benoît Le Cam ◽  
Andri Andriyana ◽  
Eric Robin
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Mechanical Responses ◽  
Material Compatibility ◽  
Durability Analysis ◽  
Inelastic Responses ◽  
Nitrile Rubbers ◽  
Loading Tests ◽  
Cyclic Loading Tests ◽  
Conventional Diesel Fuel

ABSTRACT Palm biodiesel is deemed a promising future fuel substitute for conventional diesel fuel. In line with this perspective, necessary changes in the existing diesel engine system are expected in order to address the issue of material compatibility. One typical degradation observed in rubber components exposed to aggressive solvent such as palm biodiesel during the service is swelling. Thus, the investigation of the effect of swelling on the mechanical response under cyclic loading is prerequisite for durability analysis of such components. In this study, filled and unfilled swollen nitrile rubbers are immersed in conventional diesel and palm biodiesel baths until a 5% swelling level is achieved. Both dry and swollen rubbers are subjected to uniaxial cyclic loading tests. The analysis of the mechanical responses has shown that swelling decreases inelastic effects such as hysteresis, stress softening, and permanent set. For both dry and swollen rubbers, fillers are found to have significant effects in the inelastic responses, whereas the effects of solvent and loading rate are comparable.

scholarly journals Subloading Surface Model and Experimental Study of Coal Failure under Cyclic Loading

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Si-fei Liu ◽  
Zhi-jun Wan ◽  
Jing-chao Wang ◽  
Shuai-feng Lu ◽  
Tong-huan Li
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Surface Model ◽  
Deformation Characteristics ◽  
Response Characteristics ◽  
Rock Structure ◽  
Specific Strain ◽  
Damage Process ◽  
The Stability ◽  
Number Of Cycles

The fatigue damage of rock is an important factor affecting the stability of rock structure. In this paper, the mechanical response of coal under cyclic loading was studied. In order to accurately describe the deformation characteristics of coal under cyclic loading, an elastic-plastic model of coal based on the theory of subloading surface was established and verified by experiments. The model can well reflect the Mancin effect and ratcheting effect of coal samples, which is basically consistent with the actual deformation characteristics of coal, and the theoretical value and experimental value are in good agreement. At the same time, the cyclic response characteristics of specimens under strain load disturbance were analyzed. The results show that the specific strain disturbance can only cause a certain damage to coal and the area of hysteresis loop decreases first, then stabilizes, and then increases as the number of cycles increases. In addition, the damage factor Dn in the model was analyzed in this paper. Dn, which can accurately describe the damage process of coal, accurately locate the time point of disturbance load change, and has greater sensitivity to coal failure, is helpful to improve the accuracy of the stability judgment of coal structure and ensure the safety of engineering. The above results are of great significance for strengthening the understanding of coal mass instability process and mode under cyclic loading.

Digital Image Correlation Method in Measuring the Out of Plane Displacement: A Case Study on an Artificial Intervertebral Disc

2020 ◽  
Author(s):  
Hassan M. Raheem ◽  
Willie “Skip” E. Rochefort ◽  
Brian K. Bay
Keyword(s):  
Digital Image Correlation ◽  
Intervertebral Disc ◽  
Digital Image ◽  
Annulus Fibrosus ◽  
Mechanical Response ◽  
Spinal Column ◽  
Correlation Method ◽  
Image Correlation ◽  
Therapeutic Interventions ◽  
Compression Tests

Abstract We have developed a simple, low-cost, and innovative design — known as a “disc emulator” to mimic the mechanical response of a motion segment (vertebra - intervertebral disc-vertebra) of the human spinal column under axial compression loads. The disc emulator consists of upper and lower components that mimic the human vertebrae and a middle component that represents the annulus fibrosus (AF). This study aims to investigate the effects of changing the stiffness of artificial annulus fibrosus of the disc emulator on the bulging measurements while performing compression tests on the disc emulator. A non-contact measurement — digital image correlation (DIC) — was used for the bulging measurements. The results show that the bulging at the posterior region for the discs without nucleus pulposus (NP) bulged inwards, but the bulging at the posterolateral region was outwards, which accords with the reported behavior of the human disc, for the disc without and with NP regardless of the stiffness of the discs. Changing the stiffness of the artificial annulus fibrosus (AAF) alters the bulging magnitudes in the disc, which shows similar responses with respect to the available data on the human disc. The emulator provides a convenient experimental platform for evaluating normal and pathological disc states and assessing the biomechanics of potential therapeutic interventions.

scholarly journals Full Field Strain Analysis of Blasting Under High Stress Condition Based on Digital Image Correlation Method

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Liyun Yang ◽  
Chenxi Ding ◽  
Renshu Yang ◽  
Zhen Lei ◽  
Jing Wang
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Stress Condition ◽  
High Stress ◽  
Correlation Method ◽  
Image Correlation ◽  
High Speed Photography ◽  
Digital Image Correlation Method ◽  
Propagation Law ◽  
High Stress Condition

The depth of mineral resources like coal continuously increases due to the exhaustion of shallow resources, and the characteristic of high ground stress in deep ground inevitably affects fracture of rock blasting. Combining with high-speed photography technology, the digital image correlation method (DIC) is introduced into experimental study on explosive mechanics. And strain evolution process of blasting under high stress condition is obtained by using the model experiment method. The preliminary results show that high stress condition has no obvious effects on the propagation law of blasting stress wave or its stress peak in the medium. In addition, it is found that medium in the “elastic vibration area” by conventional blast zoning is not always “elastic,” and on this basis, the concepts of “plastic area” and “quasielastic area” are put forward. The high stress condition does not influence partition range of above “plastic area” or “quasielastic area,” but in the “plastic area,” the high stress condition decreases both plastic strain value and its decay rate of relevant gauging points.

scholarly journals Payne Effect in Filled Nitrile Rubber Submitted to Cyclic Loadings

2012 ◽  
Author(s):  
Pierre P. Garnier ◽  
Jean-Benoît J. B. Le Cam ◽  
Michel M. Grédiac
Keyword(s):  
Cyclic Loading ◽  
Strain Amplitude ◽  
Viscoelastic Properties ◽  
Nitrile Rubber ◽  
Loading Conditions ◽  
Payne Effect ◽  
Two Temperatures ◽  
Loading Tests ◽  
Number Of Cycles ◽  
Cyclic Loading Tests

This study deals with the viscoelastic properties of filled nitrile rubber submitted to cyclic loading conditions. Classic strain amplitude sweeps were first carried out on both a filled and an unfilled nitrile rubber. Tests were performed at two temperatures ambient and 80 °C. Some specimens were then subjected to a high number of cycles to study the variations in the viscoelastic properties and the sensitivity of the Payne effect to cyclic loading tests at several given strain amplitudes.

scholarly journals Cyclic virtual test on wood furniture by Monte Carlo simulation: from compression behavior to connection modeling

2019 ◽  
Vol 20 (6) ◽  
pp. 606
Author(s):  
L. Chevalier ◽  
F. Pled ◽  
F. Zambou ◽  
E. Launay
Keyword(s):  
Numerical Simulation ◽  
Monte Carlo ◽  
Cyclic Loading ◽  
Mechanical Response ◽  
Experimental Testing ◽  
Confidence Regions ◽  
Permanent Strain ◽  
Cyclic Compression ◽  
Bunk Bed ◽  
Number Of Cycles

Prediction of durability of wood product is a major challenge and an important goal for furniture industry. Numerical simulation based on approximation methods such as the finite element method (FEM) is an efficient and powerful tool to address this challenge while avoiding expensive experimental testing campaigns. Nevertheless, the strong heterogeneity of wood-based materials, the specific geometrical characteristics of wood-based structures (such as furniture that can often be represented as an assembly of beams, plates and/or shells) and the complex nonlinear 3D local behavior near the connections between structural parts may induce some difficulties in the numerical modeling and virtual testing of furniture for robust design purposes. Especially, when cyclic loading occurs, the behavior of junctions in furniture involves a local permanent strain that increases with the number of cycles and that can lead to an important gap potentially affecting the structural integrity of furniture. In this paper, we present an experimental campaign of cyclic compression tests carried out on spruce specimens. Theses specimens are cut out from a bunk bed and loaded under cyclic compression. The cyclic compression loading applied to the specimens leads to an evolution of the permanent strain during cycles that is modeled using a simple law describing the displacement gap as a function of the number of cycles. Considering the strong dispersion in the mechanical properties of wood-based materials and the variabilities induced by the experimental configuration, a stochastic modeling of the gap is proposed by having recourse to the maximum entropy (MaxEnt) principle in order to take into account the random uncertainties on the experimental setup and between the test specimens. The random mechanical response of a complex corner junction in a bunk bed under cyclic loading is then numerically simulated by using a Monte Carlo numerical simulation method as stochastic solver. This provides independent realizations of the random gap evolution (with respect to the number of cycles) in the bunk bed corner, allowing probabilistic quantities of interest related to the random gap, such as first- and second-order statistical moments (mean value, standard deviation) as well as confidence regions (with a given probability level), to be estimated.

scholarly journals Evaluation of the effects of cross-linking and swelling on the mechanical behaviors of hydrogels using the digital image correlation method

Soft Matter ◽  
2019 ◽  
Vol 15 (16) ◽  
pp. 3389-3396 ◽  
Author(s):  
Makoto Uchida ◽  
Tatsuya Sengoku ◽  
Yoshihisa Kaneko ◽  
Dai Okumura ◽  
Hiro Tanaka ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Statistical Model ◽  
Mechanical Response ◽  
Correlation Method ◽  
True Stress ◽  
Image Correlation ◽  
Cross Linking ◽  
Strain Response ◽  
Mechanical Behaviors ◽  
Non Gaussian

The effects of cross-linking and swelling on the true stress–strain response of hydrogel were evaluated using DIC, and the mechanical response was fitted based on a non-Gaussian statistical model.

scholarly journals Cyclic Soft/Hardening and Microscopic Mechanism of GS-20Mn5

2021 ◽  
Author(s):  
Zongyuan Zou ◽  
Doudou Liu ◽  
Shuting Han ◽  
Chunyan Song ◽  
Hongzhong Wang
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Cast Steel ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Offshore Platforms ◽  
Microscopic Mechanism ◽  
Tem Analysis ◽  
Loading Tests ◽  
Cyclic Loading Tests

Abstract The cyclic plastic characteristics of metal materials are different from the deformation characteristics under monotonic loading, which has an important effect on the safety of structures in service under cyclic loading. However, GS-20Mn5, which is commonly used in large hydraulic machine beams, offshore platforms and large Bridges, is still lacking the studies of mechanical response characteristics under cyclic loading. In this study, the cyclic softening/hardening characteristics of GS-20Mn5 are studied by a series of cyclic loading tests under uniaxial strain control. Combined with transmission electron microscope (TEM) analysis of cyclic loading tests under typical strain levels, the microscopic mechanism of cyclic softening/hardening is discussed. The results show that the cyclic softening/hardening properties of GS-20Mn5 cast steel are sensitive to amplitudes and cycles. At smaller strain amplitudes (0.16%,0.2% and 0.3%), the cyclic hardening properties of GS-20Mn5 cast steel are rapid at the beginning of the cycle, followed by cyclic softening and then slow secondary cyclic hardening at the end. However, under larger strain amplitudes (0.4% and 0.5%), the cyclic hardening continues during the cyclic loading, and the hardening rate is bigger at the beginning of the cyclic loading and smaller at the later cyclic stage. The cyclic softening/hardening characteristics of GS-20Mn5 cast steel are related to the dislocation structure of ferrite and pearlite. Taking the strain amplitude of 0.2% as an example, the initial cyclic hardening is mainly caused by the proliferation and interaction of dislocations in ferrite. Dislocation spots and cell walls in ferrite grains are mainly caused cyclic softening at the initial stage, the secondary cyclic hardening is directly related to dislocation proliferation and entanglement in pearlite.

scholarly journals Mechanical response of a Laser Cladding repaired structure: localization of plastic strain due to microstructure gradient

2019 ◽  
Vol 300 ◽  
pp. 03003
Author(s):  
Camille Guévenoux ◽  
Simon Hallais ◽  
Alexandre Charles ◽  
Eric Charkaluk ◽  
Andrei Constantinescu
Keyword(s):  
Laser Cladding ◽  
Mechanical Response ◽  
Base Material ◽  
Correlation Method ◽  
Tensile Tests ◽  
Image Correlation ◽  
Thin Walls ◽  
Gauge Section ◽  
Initial Geometry

Laser Cladding is an additive manufacturing technology enabling to repair complex metallic components by removing the worn region and reconstructing locally the initial geometry. The aim of this work is to study the mechanical response of Inconel 718 repaired thin walls. More precisely, we perform an EBSD imaging and in-situ SEM tensile tests on specimen whose gauge section contains the interface between base material and repaired area. We observe the multiaxial strain patterns until failure at the grain level using a Digital Image Correlation method and superpose this pattern with the microstructure gradient induced by repair. The observations highlight a strain localization phenomenon in repaired structures mainly due to grain size effect.

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