Critical Deformation Research Articles

Developing evolutionary models for deformation band formation in high-porosity suprasalt sandstones: An example from Paradox Basin, Utah

Pervasive deformation adjacent to salt diapirs can drive significant porosity and permeability reduction in potential reservoir units, yet predicting the intensity and spatial distribution of these subseismic-scale features has remained as a persistent challenge. Previously, Jurassic sandstones adjacent to salt-cored anticlines in the Paradox Basin, eastern Utah, have been used to characterize deformation banding formation. However, these host rocks have undergone significant structural and diagenetic modification following band formation, which adds significant complexity to analyses of this type. Here, we integrate detailed structural transect analysis, petrologic analysis of bands and host rocks, depth-compaction relationships, critical state deformation models, and regional burial evolution models to constrain the timing and conditions of band formation. This analysis demonstrates that bands in this region formed prior to pervasive cementation and are generally expressed as two plastic strain gradients; one characterized by distributed deformation bands across the crest of salt-cored anticlines and a second wherein deformation band density increases near mesoscale normal faults. Comparison of these results with numerical structural evolution models of similar structures indicates that band gradients may have formed as a result of outer-arc extensional stress induced by the rising diapir and are linked with normal faults. These results highlight that the integration of material behaviors with kinematic evolution can constrain models for deformation band formation and may provide a useful workflow for understanding the development of these features in geologically young petroleum systems like those of the Atlantic passive margin.

A refined model for the flexural behavior of reinforced UHPC members under sustained loading

The long-term behavior of reinforced Ultra-High Performance Concrete (UHPC) members is significantly influenced by UHPC’s creep properties. To predict the long-term performance of structural members, it is essential to have both a material-level creep model and a constitutive model for structural analysis. This paper presents a refined model for the long-term performance of UHPC, incorporating critical nonlinear deformation mechanisms: instantaneous damage, plastic strain, creep strain, and time-dependent damage. The constitutive model for instantaneous damage and plastic strain mechanisms is based on experimental data from short-term cyclic loading tests on UHPC specimens. Additionally, the creep strain components and time-dependent damage evolution laws are derived from well-established linear and nonlinear creep models, validated for cementitious materials through extensive research. The model parameters were meticulously calibrated using creep damage test results from UHPC. The validation process included linear and nonlinear creep tests on UHPC cylinders under sustained stress levels ranging from 0.2fc to 0.66fc, creep failure tests on UHPC cylinders under sustained stress levels from 0.85fc to 0.95fc, and long-term bending tests of reinforced UHPC beams under sustained load. In the linear and nonlinear creep tests, comparison between the calculated ultimate creep coefficients and the experimental results demonstrates the model’s validity under low and moderate stress levels. In the creep failure test, a comparative analysis of strain evolution and creep lifetime between experimental and model results confirms the model’s validity under high sustained stress levels. Similarly, during the long-term bending test, simulated time-dependent displacement and compressive strain show good agreement with the experimental data, confirming the model’s accuracy in predicting the long-term performance of reinforced UHPC members. Furthermore, to streamline the constitutive model, the instantaneous damage effect was simplified and ultimately neglected. A comparison of simulation results between the original model and the simplified version demonstrates that disregarding the instantaneous damage effect is a safe approach for practical engineering applications.

Hot deformation behaviour of Swaged Zircaloy-4 at varying strain rate and its microstructural evolution

Zirconium alloy demonstrates a favourable combination of strength, ductility, low neutron absorption cross-section, as well as excellent corrosion and oxidation resistance. In the context of its application as a reactor component, the critical hot deformation behaviour of isothermally swaged Zr-4 alloy has been extensively studied. Different combinations of elevated temperatures (873 K to 1023 K) and strain rates (0.01 s−1 to 10/s) have shown enhancement in flow stress. Analysis of stress flow, microstructural changes, and activation energy behaviour was performed using a state-of-the-art thermomechanical simulator with 50% reduction in sample thickness. The modified Arrhenius equation was employed to correlate theoretical and experimental flow stress behaviour. EBSD was utilized to understand texture evolution in hot deformed samples, revealing a transformation from pure basal to basal plus pyramidal poles concerning the compression direction. Texture evolution played a significant role in microstructural development, further characterized through TEM, which showed influential characteristics like subgrain boundaries, dislocations, and precipitate behaviour. Dynamic recrystallization mechanisms in swaged Zr-4 hot deformed samples were analysed using bright and dark field TEM modes, which were subsequently correlated with other microstructural characteristics such as grain morphology and structural defects.

Mechanical Characterization Potentials of Aluminide Diffusion Coatings on Molybdenum Substrates

A mechanical test strategy is designed to determine the resistance of protective intermetallic aluminum layers on molybdenum substrates. Performing mechanical experiments, such as compression, four‐point bending and indentation tests, the specific failure behavior and a potential impact of observed phase transformations within the interface zone on the structural integrity and adhesion strength are examined. Herein, the applied test structure aims at the description of damage characteristics and critical deformation states regarding the type of loading. In this respect, it focuses on delamination behavior under compressive load and crack channeling due to bending stress. The analysis of the mechanical experiments is supported by various measurement techniques, including 3D camera equipment (GOM) and an acoustic emission (AE) analysis system. In particular, the application of the AE technique in this work provides a helpful contribution to the detection of delamination failure and the development of multiple crack channeling. Considering the successfully applied experimental approaches, it is assumed that more complex coating‐base material combinations can be characterized this way with respect to preceding annealing effects and the thereby influenced load capacity of thin films under different loading types.

An integrated determination method of optimal supporting time against TBM jamming

TBM (Tunnel Boring Machine) jamming and support failure occur frequently with inappropriate supporting time, particularly when TBM crosses adverse geology. Given this, an integrated determination method of optimal supporting time against TBM jamming was proposed. In this paper, the causes and failure mechanism of large deformation in the tunnel were revealed through X-ray diffraction (XRD) measurement of the rocks. The frictional resistance of TBM shield and the stress of support under different supporting time and measures were investigated by numerical simulation. It was shown that early installation of the support will lead to excessive load on the support, resulting in support failure. Contrarily, delayed installation of the support will lead to excessive tunnel deformation, inducing TBM shield jamming. The optimal supporting time was determined by comprehensively analyzing the critical deformation of TBM jamming and ultimate stress of support. The deformation of surrounding rock in the range of 31.6 mm ∼ 39.9 mm was the optimal support time in this study. Installation support with an optimal supporting time can ensure the safety of TBM and support simultaneously. The range of optimal supporting time decreases continuously with the weakening of support parameters. Specifically, the support measures (bolt + steel arch, shotcrete + bolt) cannot simultaneously ensure the safety of the TBM and support. The research results can effectively guide the prevention of jamming and support design in TBM tunnels.

Characteristics of Damage to Brown Rice Kernels under Single and Continuous Mechanical Compression Conditions.

During the rice milling process, single and continuous compression occurs between brown rice and the processing parts. When the external load exceeds the yield limit of brown rice, brown rice kernels are damaged; with an increase in compression deformation or the extent of compression, the amount of damage to the kernels expands and accumulates, ultimately leading to the fracture and breakage of kernels. In order to investigate the mechanical compression damage characteristics of brown rice kernels under real-world working conditions, this study constructs an elastic-plastic compression model and a continuous damage model of brown rice kernels based on Hertz theory and continuous damage theory; the accuracy of this model is verified through experiments, and the relevant processing critical parameters are calculated. In this study, three varieties of brown rice kernels are taken as the research object, and mechanical compression tests are carried out using a texture apparatus; finally, the test data are analysed and calculated by combining them with the theoretical model to obtain the relevant critical parameters of damage. The results of the single compression crushing test of brown rice kernels showed that the maximum destructive forces Fc in the single compression of Hunan Early indica 45, Hunan Glutinous 28, and Southern Japonica 518 kernels were 134.77 ± 11.20 N, 115.64 ± 4.35 N, and 115.84 ± 5.89 N, respectively; the maximum crushing deformations αc in the single compression crushing test were 0.51 ± 0.04 mm, 0.43 ± 0.01 mm, and 0.48 ± 0.17 mm, respectively; and the critical average deformations αs of elasticity-plasticity deformation were 0.224 mm, 0.267 mm, and 0.280 mm, respectively. The results of the continuous compression crushing test of brown rice kernels showed that the critical deformations αd of successive compression damage formation were 0.224 mm, 0.267 mm, and 0.280 mm, and the deformation ratios δ of compression damage were 12.24%, 14.35%, and 12.84%. From the test results, it can be seen that the continuous application of compression load does not result in the crushing of kernels if the compression deformation is less than αd during mechanical compression. The continuous application of compressive loads can lead to fragmentation of the kernels if the compressive deformation exceeds αd; the larger the compression variant, the less compression is required for crushing. If the compression deformation exceeds αc, then a single compressive load can directly fragment the kernels. Therefore, the load employed during rice milling should be based on the variety of brown rice used in order to prevent brown rice deformation, which should be less than αd, and the maximum load should not exceed Fc. The results of this study provide a theoretical reference for the structure and parameter optimisation of a rice milling machine.

Finite Element Analysis of Patient-Specific Cranial Implants under Different Design Parameters for Material Selection

This work presents the study of the thickness vs. stiffness relationship for different materials (PMMA and PEEK) in patient-specific cranial implants, as a criterion for the selection of biomaterials from a mechanical perspective. The geometry of the implant is constructed from the reconstruction of the cranial lesion using image segmentation obtained from computed axial tomography. Different design parameters such as thickness and perforations are considered to obtain displacement distributions under critical loading conditions using finite element analysis. The models consider quasi-static loads with linear elastic materials. The null hypothesis underlying this research asserts that both biomaterials exhibit the minimum mechanical characteristics necessary to withstand direct impact trauma at the implant center, effectively averting critical deformations higher than 2 mm. In this way, the use of PMMA cranioplasties is justified in most cases where a PEEK implant cannot be accessed.

Seismic performance assessment and design procedure of base-isolated bridges with lead-rubber-bearing and negative stiffness springs (LRB-NS)

This study proposed a straightforward and simplified design procedure for the base-isolated highway bridges with LRB and negative stiffness springs (LRB-NS) device. Compared with the traditional LRB-isolated system, the proposed LRB-NS device contains dual-functionality: (a) alleviate the nonlinearity and damage in piers during slight-to-moderate earthquakes; (b) control the excessive bearing deformation and prevent failure during catastrophic excitations. Therefore, this device effectively improves the post-earthquake function and seismic resilience of bridge systems, and facilitate the rescue operations, since bridge can allow the passage of urgent vehicles with minimal repair. With incremental dynamic analysis (IDA) accounting for the record-to-record variability, the LRB-NS device is shown with dual-functionality as designed and better seismic performance than LRB, subjected to all of far-field (FF), near-fault no-pulse (NFNP), and near-fault pulse-type (NFPT) motions. Additionally, the influence of three kernel parameters, i.e., target period ratio sy_LRB-NS, initial spring length l, and critical deformation ucr, is also investigated in detail, concerning both the structural properties and seismic responses. The results show that increasing sy_LRB-NS and l both benefits the dual-functionality of LRB-NS, but the efficiency reduces with the increase of these design values. While greater ucr significantly reduces column nonlinearity, the bearing deformation is increased as a result, and thus careful tradeoff should be made during practical design.

A novel fracture criterion for elastic‐brittle cracked body under compression and shear conditions

AbstractWhen the elastic‐brittle cracked body is subjected to compressive‐shear loading, not only does the phenomenon of wing crack initiation and propagation occur, but there is also a notable incidence of secondary crack initiation and propagation due to shear stress. Moreover, the shear fracture toughness (KIIc) predicted by the fracture criterion in the framework of classical fracture mechanics is usually smaller than the tensile fracture toughness (KIc), which is inconsistent with the actual observations. Therefore, this research firstly establishes a mechanical model of an elastic‐brittle cracked body under biaxial compression considering three kinds of crack parameters and materials' mechanical properties. Then, the stress field characteristics at the crack tip are analyzed. Next, a compression‐shear mixed fracture criterion is proposed. Finally, the effects of the lateral pressure coefficient (λ), critical plastic zone size (rc), friction coefficient (f), and deformation parameters of the crack surface on the failure modes at the crack tip are investigated.

Bending strain–induced changes in perpendicular magnetic properties of Pt/Co/Pt films on flexible substrates

We studied the irreversible changes in the perpendicular magnetic properties of Pt(2.2 nm)/Co(0.8 nm)/Pt(2.2 nm) films deposited on a flexible polyethylene terephthalate substrate with bending deformation. The changes in the magnetic properties of the Pt/Co/Pt film with deformation were analyzed using magneto-optical Kerr-effect microscopy. The film was bent in one direction using cylindrical rods or semicylindrical grooves of different radii and then restored to the initial flat state. No significant changes in the magnetic properties due to bending strain were observed below a critical bending curvature. However, for bending curvatures above +0.25 mm−1 or below −0.14 mm−1, the magnetic domain shape changed from circular to elongated ellipses, perpendicular to the bending direction, and the coercivity of the film increased by 10%–30%. Furthermore, the domain wall motion exhibited a distinct anisotropic behavior, with ∼12-fold difference in the velocity of domain wall motion in different directions. Conclusively, the magnetic properties of the Pt/Co/Pt film fabricated on a flexible substrate exhibited irreversible changes beyond a critical deformation of +2.44% or −1.37%.

Investigating Fertilizer Spreader Blades for Improved Flow Behaviours and Material Resilience in Palm Plantation Settings

Fertilizer spreaders play a crucial role in evenly distributing granule fertilizer across palm plantations. However, in specific areas where growth conditions are unsuitable, fertilizer application becomes unnecessary. Therefore, this study aims to improve granule fertilizer distribution efficiency through enhanced fertilizer blade design. Using Finite Element (FE) simulation, the stress deformation and deflection of the existing spreader blade were evaluated. Meanwhile, Computational Fluid Dynamics (CFD) simulation was used to investigate the influence of spreader design on fertilizer projection speed and direction in the case of open and closed side discharge. The study revealed that the applied forces increased both the critical stress deformation and deflection. To ensure the fertilizer spreads properly over the desired area, the initial velocity had to be increased proportionally with an increase in the angle of direction. These findings contributed to a deeper understanding of the relationship between fertilizer projection velocity, spreader blade strength, and flow behaviour, enabling the reduction of waste in granule fertilizer, while enhancing the operational efficiency and reliability of fertilizer spreader.

Hot Deformation Behavior of Inconel 718 Alloy Using Regression-based Dynamic Material Model and Applications in Ring Rolling Manufacturing

Inconel 718 nickel-based alloy is extensively used in the aerospace industry (e.g., gas turbine engine components) because of its excellent corrosion resistance and high mechanical properties at elevated temperatures. However, there is a certain limit to manufacturing the alloy through plastic deformation due to its high deformation resistance and complicated deformation behaviors. In this study, the hot deformation behavior of Inconel 718 alloy was investigated to establish how processing conditions of flow stress-strain, at strain rates from 0.001 to 10 s<sup>-1</sup>, and temperatures from 850 to 1200<sup>o</sup>C, affected dynamic recrystallization. The regression-based material model was utilized to calculate the strain-rate sensitivity, and subsequently depict the efficiency of the power dissipation and instability criterion of hot deformation. The processing map and instability criterion predicted by the developed 3<sup>rd</sup>-order polynomial regression model corresponded with the experimental results and in particular, showed a better prediction for instability regime compared to the existing discrete derivative approach. Predicting the strain-rate sensitivity values on a continuous scale with regression analysis covered the additional instability region of the high strain rate near 10 s<sup>-1</sup>. The dynamic recrystallization deformation was also characterized by microstructural analysis along with the processing map. Consequently, ring-rolled aviation parts were manufactured with the optimum processing parameters, which conform to the AMS 5663 standard (Aerospace material specifications for Inconel 718).

Mathematical modeling of rocks fracture within local structures

Soil massif fracturing has a significant impact on change in engineering and geological conditions and, as a result, on stability of structures. Development of tectonic fracturing of local structures, taking into account the history of the process, its mechanism, resulting stresses in the massif and subsequent deformations of the rocks, led to a change in their structure, composition and strength characteristics, activation of hypergenesis and exogenous processes. The above circumstances require careful attention to identification of areas of increased fracturing, as the most dangerous in terms of risks during the construction of engineering structures. Field methods for assessing the fracturing of rock masses are laborious. It is not always possible to conduct instrumental surveys that allow solving the final problem – establishing patterns and sizes of damaged areas within local structures. The existing mathematical models for assessing fracturing, as a rule, are used to solve local problems: assessing the stability of developed pits, water content of rock masses, degree of fragmentation of individual blocks, etc. This information is not sufficient when assessing the areal distribution of weakened zones and clarifying their boundaries, since it does not take into account the history of the development of the structure, its parameters (dimensions, amplitude of the foundation block uplift, deformation properties of rocks). Aim. To develop a mathematical model of formation of the red-colored strata tectonic fracturing zones based on deformation criterion of destruction and mechanism of development of local structures. Results. The authors have developed a new mathematical model for predicting damage (fracturing) of terrigenous rocks of the red-colored strata that make up local structures, based on the mechanism of formation of local tectonic structures of the 3rd order and the deformation criterion of destruction. The paper introduces the mathematical dependencies that make it possible to predict the size (area) of taxa based on the data on the uplift amplitude of local structures. The results of the research can be used in assessing the fracturing of massifs composed of terrigenous rocks, and make it possible to judge the regularities in distribution of weakened zones within the entire massif being assessed.

Fuzzy seismic fragility analysis of underground structures considering multiple failure criteria

To avoid the deficiency of a single failure criterion and deterministic thresholds of limit states in seismic fragility analysis of underground structures, a method of fuzzy seismic fragility analysis of underground structures considering multiple failure criteria is proposed by combining fuzzy-random theory and copula theory. In this method, probabilistic seismic demand and capacity analyses based on different failure criteria are first performed. Then, the fuzziness of the limit states of different failure criteria is characterized by using membership functions, and the fuzzy seismic fragility of underground structures considering a single failure criterion with different membership functions is further calculated. On this basis, the copula function and the combination of membership functions are optimized to characterize the correlation between multiple failure criteria and establish fuzzy seismic fragility curves considering multiple failure criteria. Taking the Daikai subway station as the background, the effects of different failure criteria and the fuzziness of limit states on the seismic fragility are discussed, and the optimal combination of membership functions that characterizes the fuzziness of limit states under the failure criteria of deformation and strength is also presented. The results show that the failure criteria and fuzziness of limit states have significant effects on the seismic fragility of underground structures, and the combination of trigonometric membership functions is the optimal combination that characterizes the fuzziness of multiple failure criteria. Moreover, the fuzzy seismic fragility of underground structures considering multiple failure criteria is more sensitive to the fuzziness of limit states under frequent earthquakes and basic earthquakes, while the multiple failure criteria and the correlation between different failure criteria have more significant effects on the fuzzy seismic fragility considering multiple failure criteria under rare earthquakes and extremely rare earthquakes.

Novel electrocardiographic criteria may render possible the more accurate recognition of cardiac amyloidosis.

The early diagnosis of cardiac amyloidosis (CA) is paramount, since there are effective therapies that improve patient survival. The diagnostic accuracy of classical electrocardiographic (ECG) signs, such as low voltage, pseudoinfarct pattern, and conduction disturbances in the diagnosis of CA, is inferior to that of the echocardiographic myocardial deformation criteria; therefore, our aim was to find more accurate novel ECG criteria for this purpose. We tested the diagnostic value of five novel ECG criteria, two of them devised by us, in 34 patients with confirmed CA (20 transthyretin amyloidosis and 14 AL amyloidosis) and 45 control patients with left ventricular hypertrophy on echocardiography due to hypertension, valvular aortic stenosis and hypertrophic cardiomyopathy. The following novel ECG criteria, that suggested CA, were tested: QRS amplitude in lead I<0.55mV (I<0.55); QRS amplitude in lead aVR<0.5mV (aVR<0.5); average QRS amplitude of leads I+aVR<0.575mV [(I+aVR)<0.575]; average QRS amplitude of leads I+aVR/average QRS amplitude of leads V1-4<0.375 [(I+aVR)/(V1-4)<0.375]; average QRS amplitude of leads I+aVR/longest intrinsicoid deflection in leads I,aVL,V1-6<0.0115 [(I+aVR)/I,aVL,V1-6ID<0.0115]. The I<0.55, aVR<0.5, (I+aVR)<0.575, (I+aVR)/(V1-4)<0.375, (I+aVR)/I,aVL,V1-6ID<0.0115 test accuracy (TA) were 81%, 84.8%, 82.3%, 84.8%, and 83.3%, respectively; the sensitivity (SE): 76.5%, 82.4%, 85.3%, 82.4%, and 76.9%; specificity (SP): 84.4%, 86.7%, 80%, 86.7%, and 87.5%; positive predictive values (PPV): 78.8%, 82.4%, 76.3%, 82.4%, and 80%; negative predictive values (NPV): 82.6%, 86.7%, 87.8%, 86.7%, and 85.4%; area under curve (AUC) values: 0.8922, 0.8794, 09016, 0.8824, and 0.8462 were respectively. These parameters of the novel ECG criteria were at least as good as those reported by other authors in the literature of the qualitative (TA: 67%, SE: 80%, SP: 34%, PPV: 75%, NPV: 42%, AUC: 0.57) and quantitative apical sparing (TA: 64-80%, SE: 66-81.3%, SP: 55-78.3%, PPV: 33-83.9%, NPV: 41-75%, AUC: 0.62-0.68) and left ventricular ejection fraction/global longitudinal strain >4.1 (TA: 77%, SE: 93%, SP: 38%, PPV: 79%, NPV: 69%, AUC: 0.65) echocardiographic criteria. Among the classical criteria, the low voltage in limb leads criterion was present most frequently (in 73.5%) in patients with CA, with slightly worse diagnostic value than the novel ECG criteria (TA: 78.5%, SE: 73.5%, SP: 82.2%, PPV: 75.8%, NPV: 80.4%). The novel ECG criteria [mostly the aVR<0.5, (I+aVR)/(V1-4)<0.375] seem at least as reliable in the diagnosis of CA as the best echocardiographic myocardial deformation criteria and might be used either together with the echocardiographic criteria or as stand-alone criteria to diagnose CA in the future.

Stability and Deformation Criteria in Free Boundary CMC Immersions

Let ∑n and M n+1 be smooth manifolds with smooth boundary. Given a free boundary constant mean curvature (CMC) immersion φ: ∑ → M, we found results related to the existence and uniqueness of a deformation family of φ, {φt}t ∈I , composed by free boundary CMC immersions. In addition, we give to some criteria of stability and unstability for this type of deformations. These results are obtained from properties of the eigenvalues and eigenfunctions of the Jacobi operator Jφ associated to φ and establishing conditions for this operator such as Dim(Ker(Jφ)) = 0, or if Dim(Ker(Jφ)) = 1 and, for f ∈ Ker(Jφ); f ≠ 0, ∫∑ volφ*(g) ≠ 0. The deformation family is unique up to diffeomorphisms.

Breakup prediction of oscillating droplets under turbulent flow

Droplet and bubble breakup phenomena under turbulent flow have been widely studied for over 70 years through theoretical, experimental and numerical approaches. Despite significant progress, the dynamics of breakup remains an active research topic. The present study considers a database of breakup events under turbulent conditions. The database contains neutrally buoyant droplets obtained for a single moderate turbulent Reynolds number and a Weber number near the critical Weber number of the droplets, allowing for long time evolution prior to droplet breakage. Each droplet in the database follows a consistent behavior: the droplet undergoes (1) an initial shape deformation, then (2) an extended oscillatory regime, until (3) a critical large deformation starts, leading to (4) a capillary-driven breakup. While the first two stages have been investigated in our previous work using spherical harmonics decomposition, this study focuses on the last two stages, describing them qualitatively and quantitatively by means of seven different shape parameters. These shape parameters are based on different information of the specific droplet such as its surface, its volume or its averaged mean curvature, and provide a multidimensional analysis of the droplet breakup. They are used to measure the time spent in the final two stages prior to breakup, as well as the transition between these stages. Additionally, we establish breakup thresholds for each shape parameter to predict neutrally buoyant droplet breakup under turbulent flow conditions.

Contact mechanics modeling of fractal surface with complex multi-stage actual loading deformation

The contact mechanical behavior of rough surfaces is related to the friction and wear of mechanical components, and also has an important impact on the dynamic performance and force transfer characteristics of assembly surfaces. This paper aims to solve the complex multi-stage mechanical deformation mode of the loading surface, and establishes all multi-stage contact mechanical models involved in the actual loading deformation process from the perspective of the actual deformation and critical deformation of the asperity. Firstly, based on the three-dimensional fractal contact theory, the force deformation relationship of a single asperity during the full deformation stage of loading is constructed. Then, six critical contact areas and four critical deformation quantities of a multi scale asperity are derived. Finally, the complex multi-stage deformation contact mechanical models of three-dimensional fractal surfaces under actual loading are established. The area power spectral density (APSD) function spectrum of rough surface under different fractal parameters, as well as the variation of contact load, contact stiffness, and contact area are analyzed numerically. Compared with several classical models, the rationality of the proposed model is verified. This study can be used as the basis for constructing the overall dynamic model of an assembly system

The origins of critical deformations in cylindrical silicon based Li-ion batteries

Correlative neutron and X-ray imaging unravels the causes of localized defects in Li-ion batteries containing a silicon-graphite based anode.

Método DIC aplicado na calibração de um modelo MEF de interface coesiva rocha-argamassa

Abstract In civil engineering, the stability of many structures depends on the physical properties of the contact between the concrete seated on the rocky foundation surface. Usually, they are critical structures of great importance to society, such as: bridges, tunnels and dams. Thus, the shear behavior of rock-concrete joints is a key factor of the structural stability. The method of cohesive zones (CZM) allows to simulate the beginning of the formation of a crack and its propagation, without knowing the crack location or when it will start. Thus, in this work, a numerical model was developed capable of simulating the failure due to interfacial delamination of the contact between a structure formed by mortar seated on a rocky granite leaning surface. The calibration of the numerical model was performed using the experimental test results of simple compression on a block of rock in contact with the mortar by an inclined interface. The test was monitored using a high-resolution digital camera. The data were processed using the digital image correlation method (DIC) to obtain displacement data of the laboratory test. The DIC results were used to calibrate the nonlinear numerical model of the test using the bilinear method of cohesive zone in the rock-mortar interfacial contact elements. By a parametric analysis varying the maximum shear stress parameter of the contact cohesive elements, the bilinear law was adjusted (Maximum tensile stress and critical displacement and damage rate). Indirectly, the rate of release of energy of critical deformation from the rupture of the contact was also estimated.