Dynamic Cyclic Loading Research Articles

Transient model of unsteady creep of sliding zone soil under cyclic dynamic load based on fractional derivative

The shear mechanical behavior of soils in the slip zone under cyclic loading is of great importance for the stability analysis of landslides. In this paper, an experimental device is developed to study the nonlinear deformation mechanism of soil in sliding zone under cyclic load. Based on field tests and model tests, the change of shear strength parameters of the soil in the slip zone with cyclic loading parameters was investigated. Based on the deformation characteristics of slip zone soils under cyclic dynamic loading, the unsteady creep transient model based on fractional derivative is established, and three deformation types of sliding zone soil are described: stable, critical and destructive. The Levenberg-Marquardt (LM) algorithm is used to fit the nonlinear curves, and the applicability of the model is also verified. This research method provides a test apparatus and a method for studying the deformation characteristics of slip zone soils under cumulative loading.

Seismic Damage Analysis of Pile Foundation on Liquefiable Sandy Soil Foundation

Under the action of cyclic dynamic loads caused by earthquakes, the sandy soil foundation will liquefy, which may easily lead to damage to the pile foundation. For example, the soil liquefaction will cause pile foundation subsidence, the failure of the connection between pile cap and cap, and the beam drop caused by pile foundation moving sideways with soil. There are many influencing factors of foundation liquefaction, and the influence of many factors on foundation liquefaction is highly nonlinear. The author analyzes the liquefaction principle of sandy soil foundation and combines the seismic damage data of pile foundation with the experimental data of large-scale shaking table. Then this paper describes the damage and failure characteristics of pile foundation on liquefied sandy soil foundation.

THE EFFECT OF CEMENT AND SCREW ON THE RESISTANCE OF AN IMPLANT CROWN TELESCOPICALLY ENGAGED TO A HEXAGONAL-SHAPED ABUTMENT UNDER COMPRESSIVE DYNAMIC CYCLIC FATIGUE LOADING.

To investigate the resistance of an implant crown telescopically engaged to a geometrically defined hexagonal abutment with and without cement under compressive dynamic cyclic fatigue loading. 40 crowns, 9 mm in height, were cast from prefabricated plastic copings, each telescopically engaged to a 3-mm-high machined hexagonal abutment. 20 crowns were retained with zinc phosphate cement, and 20 crowns were retained with a screw. A vertical load of 15 kg was applied to all samples under oscilla)on. A Periotest was used to measure the mobility of the implant crown in Periotest values (PTV). Test endpoints were defined by the following: fatigue cycles ≥ 20 million; crown PTV > 10; or if samples became visibly loose or component fracture. Cement-retained crowns failed on average at 2.60 x 106 cycles ± 2.27, while screw-retained crown samples failed at 2.17 x 106 cycles ± 1.27 with no significant difference (P > .05). Implant and abutment screw fractures were the most prevalent mode of failure in the cement-retained group, while in the screw-retained group, failures were caused by the loosening of one or both screw joints. The rate of increase in PTV was higher in the screw-retained group than in the cement-retained group. Under the experimental conditions, an implant crown telescopically engaged vertically to a 3-mm-tall hexagonal abutment, under compressive dynamic cyclic fatigue loading with or without cement, demonstrated no differences in resistance or failure outcomes. A cement-retained implant crown with telescopic engagement to the abutment is more rigid, resulting in more implant and abutment screw fractures than loosening.

Influence of retainer design and number of inlay boxes on the biomechanical behavior of zirconia cantilever resin bonded fixed dental prosthesis.

The development of dental adhesives with enhanced bond strength has assisted minimally invasive dentistry. The aim of this study was to evaluate the fracture load and stress distribution pattern of two retainer designs for posterior cantilever resin bonded fixed dental protheses (RBFDPs). Forty human mandibular molars were divided into two groups according to the retainer design; lingual coverage (LC) and occlusal coverage (OC) retainers. Each main group was then divided according to the number of inlay boxes (n = 10); one inlay and two inlay boxes. High translucency (3Y) zirconia was used to manufacture all restorations, and a dual-polymerizing adhesive resin cement was used for bonding. All specimens underwent 10,000 cycles of thermocycling (5-55°C), 240,000 cycles of dynamic loading (50 N, descending speed v = 30 mm/second, frequency = 1.6 Hz), and failure load test. Both one-way and two-way ANOVA tests were used to analyze the data. The four models included in the in-vitro study are part of the finite element analysis (FEA). When the restorations failed, maximal principal stress values on restorations, enamel, dentin, and luting resin were investigated. A statistically significant (p = 0.018) higher failure load was recorded for OC1 (627.00 ± 153.4 N) than the other groups; (548.0 ± 75.6 N, 521.20 ± 11.3 N, and 509.20 ± 14.9 N for LC1, LC2, and OC2, respectively). With regard to failure mode, one inlay box designs showed more favorable failure pattern than those of two inlay boxes. FEA showed higher stress magnitude transmitted to the tooth structure in models LC2 and OC2. Lingual coverage and occlusal coverage retainers are promising designs capable to withstand the normal occlusal force for cantilever RBFDP in premolar area. The use of two inlay boxes decreased the fracture load of the two retainer designs and increased the stress transmitted to the tooth and resulted in high incidence of catastrophic failure. Monolithic high translucent zirconia RBFDP could be considered as a viable treatment option to substitute missing posterior tooth, with improved esthetics and biocompatibility.

Road Piezoelectric Power Output Model and Experimental Study under Bidirectional Vehicle Load Excitation

Recently, piezoelectric transducers have gained significant attention for energy recovery applications in road engineering. However, in laboratory tests, vehicle loads are often simplified using vertical vibration loads, thus ignoring the role of vehicle tangential loads. In this study, a power output model of a piezoelectric transducer under vertical and tangential loads was proposed through theoretical analysis. A bidirectional cyclic dynamic load test was conducted on the piezoelectric-concrete specimens in combination with a large dynamic and static straight shear instrument, and the power output law of the piezoelectric transducer under vertical and horizontal shear was investigated. The results revealed that the vertical vibration load was the main factor affecting the output performance of the piezoelectric transducer; however, with the addition of the tangential load, the electric energy output of piezoelectric pavement increased with an increase in the horizontal shear rate and displacement. When vibrating vertically (200 kPa and 4 Hz), the electric energy output of piezoelectric pavement was 4.979 μW. However, under the action of vertical vibration and horizontal shear with the working conditions of 200 kPa and 4 Hz, and 0.1 mm and 1 Hz, the electric energy output of piezoelectric pavement was 21.04 μW, which was 3.2 times that of the vertical vibration load alone. Therefore, by considering the influence of vehicle tangential loads, the power output of piezoelectric transducers can be calculated more accurately, which provides a reference for actual installed capacities in real engineering applications.

Addressing the Timing Imbalance between Renewable Energy Generation and Use: Reversible Solid Oxide Cells Based on Rare-Earth Nickelate Oxygen Electrodes

Incorporating more renewable energy into our economy will require us to address the timing imbalance between renewable energy generation and its use. Reversible solid oxide cells which have the ability to be dynamically load cycled between electrolysis mode when renewable energy availability is plentiful, and fuel cell mode when stored energy needs to be used, offer a potential solution. In this work, we have fabricated solid oxide cells featuring a neodymium nickelate based oxygen electrode, nickel – yttria stabilized zirconia (YSZ) fuel electrodes, and YSZ solid electrolyte. The cells have been electrochemically characterized in electrolysis and fuel cells mode, as well as in dynamic load cycling mode for a period of five hundred hours. The cells were characterized by both DC polarization and AC impedance spectroscopy methods. Distribution of relaxation times (DRT) analysis of the impedance data reveal significant details about the mechanisms underlying degradation in electrolysis and dynamic cycling modes, and are strongly linked to microstructural changes in the fuel electrode. Further, the dynamic cycling experiments clearly reveal that operating the cells in the dynamic cycling mode mitigates against degradation that occurs when the cells are operated in electrolysis mode. These results strongly suggest that storage systems featuring stacks of such reversible solid oxide cells may offer a path forward to solving the timing imbalance of renewable energy generation and use.

Durability Study of Anode-Supported SOFC with Large-Area Fabricated By 4-Layer Sequential Co-Lamination and GDC Co-Firing Process

Electrolyte-Cathode interfaces are life-threatening regions of solid oxide fuel cells where degradation phenomena occur due to chemical interdiffusion. The Buffer layer is inserted between electrolyte-cathode to limit the cation exchange across the interface. However, state of art buffer layer coated by screen printing does not fully prevent cation migration which results in the formation of insulating phases such as SrZrO3. Herein, a reliable four-layered (NiO-YSZ, NiO-CeScSZ, CeScSZ, and GDC) thin film-based anode supported SOFCs with a large-area (12cm×12cm) were fabricated by sequential co-lamination, in which all cell components perform a distinct role to enhance the interfacial connectivity and packing density of electrolytes. This enhanced connectivity with a highly dense electrolyte (5-6µm) and buffer layer (2-3 µm) accomplished on the porous anode support without any structural defects. The single cell (144cm2) showed a power output of 38W at total current 50A (700°C). The Post-tested cell had exceptional micro-structural characteristics, excellent interfacial adhesion and retained its structural integrity during static and dynamic operation. Also, the formation of insulating phases and decomposition of cathode was effectively prevented, resulting in a remarkable improvement in durability. The cell with four-layered structure exhibits an extreme low-degradation rate of 0.2% kh-1 under 25A current and 21 dynamic load cycling conditions, which satisfies the strict benchmark of durability for commercialization of technology. Key word: Durability, interfacial connectivity, insulating phase, sequential co-lamination Figure 1

Performance Analysis of Multiple Steel Corrugated Pipe Arch Culvert under Construction and Periodic Vehicle Load

The arrangement of multiple culverts has gradually increased in road engineering. However, the arrangement will face a series of risks in both the construction and operation stages. A numerical model was established to analyze the construction and operation safety of multiple steel corrugated pipe arch culverts by using a fully fluid–solid coupling two-dimensional (2D) model of a highway project. The sensitivity of factors affecting the settlement of the composite foundation such as modulus and depth of ground reinforcement was discussed. Based on the results of the 2D model, a fully fluid–solid coupling three-dimensional (3D) model was established to study the influence of dynamic cyclic vehicle load on the mechanical properties of multiple steel corrugated pipe arch culverts. The ground deformation, soil stress and pore pressure, structure stress, and deformation were analyzed. The results show that the maximum settlement of the soil in the arch culvert area is at the junction of the two different arch culverts after construction. The maximum vertical deformation of the structure appears at the vault, and the arch waist is prone to stress concentration. Under cyclic vehicle dynamic load, the ground deformation, structural stress, and arch culvert subgrade deformation showed a rapid growth stage, and then tended to be stable. The weak points in the structure during the construction and operation stages were revealed, which can provide a useful reference for the design and construction of multiple steel corrugated pipe arch culverts.

Fracture Behaviour of Carbon Steel Straight Pipe with Through-Wall Crack under Cyclic Loading

Carbon steel straight pipes form part of the primary heat transport system of nuclear power plants. They may be subjected to dynamic-cyclic loads during earthquake event. This dynamic cyclic loading significantly affects the fracture resistance and the load carrying capacity of cracked components. Further, for the application of leak-before-break concepts, experimental investigations are essential. Therefore, the aim of the present study is to investigate the effect of cyclic loading on fracture resistance of through-wall cracked straight pipes. The paper presents details of the cyclic fracture test on a straight pipe and the results thereof. The behaviour of the pipe was compared with the fracture behaviour under monotonic loading. The study has shown that the load capacity of the pipe is reduced under cyclic loading and the failure is by cyclic tearing followed by sudden collapse.

Investigating mechanical properties of cemented gangue backfill materials subjected to static-dynamic combined loads

This study aims to investigate the mechanical properties and failure mechanisms for the cemented gangue backfill materials (CGBM) of the roadside filling structures along the gob-side entry with no coal pillars under static-dynamic combined loading. Cuboid cemented gangue backfill samples (CGBS) with dimensions of 50 × 50 × 100 mm were first prepared, with the fractal dimension D = 2.6 characterizing the particle size distribution of aggregates, and then conducted static-dynamic combined loading tests in terms of various pre-static loads (5–11 MPa), amplitudes (2–5 MPa), frequencies (1–16 Hz) and dynamic loading cycles (20–320 cycles). The test results indicate significant differences in the mechanical properties, acoustic emission (AE) responses, maximum principal strain fields, and ultimate failure modes of CGBS under different static-dynamic combined loading paths. With an increasing pre-static load, dynamic loading amplitude and number of cycles, the peak stress decreases by 21.28 %, 12.48 % and 11.84 % respectively, while the peak stress first decreases and then increases with the dynamic loading frequency and reaches the minimum value at the “characteristic frequency” of 4 Hz. The irreversible strain generally experiences an “acceleration - constant speed” variation during the dynamic loading as a result of the gradually stable damage effects. The dynamic elastic modulus increases by 45.84% in the pre-static load range of 5–11 MPa, while decreases with the dynamic loading amplitude. The dissipated energy increases by a factor of 6.5 with the dynamic loading amplitude, and by 27.52% with the pre-static loads. The significantly stimulated cracking activities at the beginning of dynamic loading result in extremely violent AE responses, and then the AE signals weaken due to the dominate role of opening and closure of existing cracks. The RA and AF calculation results illustrate that shear cracks become active at the initial dynamic loading and macroscopic failure stages. As the degradation effects of dynamic loading intensify, three various failure modes of inclined shear failure, “Y” shaped shear failure and conjugate shear failure for the CGBS are respectively classified, especially the conjugate shear failure characterized by two cone-shaped blocks. The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the roadside filling body during the dynamic mining.

Study on multibody contact load distribution characteristics of scraper conveying system of continuous miner

Understanding the interaction of the scraper chain–sprocket–tail drum–chain path is of great significance to improving the transportation efficiency and service life of the intermediate scraper conveying system of fully mechanized excavation equipment. The dynamic characteristics of the internal tension, running resistance, and multicontact interface load of the scraper chain are the theoretical basis of the research. Firstly, a method for obtaining periodic cyclic dynamic load history is proposed, and then the model of a single-chain scraper conveyor for a continuous shearer is constructed by using RecurDyn and simulation structures. Finally, the influence of parameters such as conveying inclination angle and running speed of the sleeve scraper chain on the reliable operation of the conveying system is determined. The results show that when the conveying angle is 12°, the scraper conveying system runs stably and the impact between multirigid bodies is small. As the chain speed increases from 0.85 to 2.4 m/s, the wear of the conveying system gradually increases, and the contact load distribution of upper chain plate 2, upper chain plate 3, and lower chain plate 3 is seriously worn.

Cumulative deformation prediction and microstructure change of coarse-grained soil under cyclic loading

This research aims to reveal the macroscopic cumulative deformation development pattern and internal structural change characteristics of coarse-grained soils under moving vehicle loads. Dynamic triaxial tests are used to investigate the development of cumulative deformation of coarse-grained soils under various deviatoric stresses, moisture contents, and loading frequencies. Based on the results of indoor tests, a comprehensive prediction model for the cumulative deformation of coarse-grained soils was established. The cumulative deformation increases with the increasing deviatoric stress, moisture content, and loading frequency. As the deviatoric stress grows, the cumulative deformation rate increases correspondingly. The cumulative deformation prediction model for coarse-grained soils proposed in this study has high accuracy. Cyclic loading reduces the number of large pores, increases the number of smaller pores, and increases the proportion of micropores with increasing deviatoric stress and moisture content. The effect of loading frequency on the deformation of coarse-grained soils is relatively small but still not negligible. Cyclic dynamic loading can transform the long pores in coarse-grained soil subgrade filler into elliptical and circular pores. The increase in moisture content can increase the proportion of long pores in coarse-grained soil filler. This research can deliver a valuable reference for analyzing the cumulative deformation of coarse-grained soils subjected to cyclic loading.

Experimental dynamic load cycling and current density measurements of different inlet/outlet configurations of a parallel-serpentine PEMFC

Proton-exchange membrane fuel cells (PEMFCs) in the transport sector require specific design and durability, and stable and reliable performance under varying cycling loads. In this study, experimental dynamic load cycling (DLC) tests and current density mapping (CDM) measurements of local current densities and temperatures were performed for different inlet/outlet configurations of reactants in a parallel-serpentine PEMFC. Results were analyzed in terms of the polarization and power curves and the DLC tests, indicating that the Inverse Hydrogen Flow configuration performed best. However, the differences with respect to the other inlet/outlet configurations (Normal Flow, Inverse Air Flow and Inverse Flow) were not significant with maximum relative voltage and power densities differences below 5% in the polarization and power curves. Also results of the experimented inlet/outlet configurations during the DLCs were similar, with maximum differences in terms of energy during the cycle below 10% comparing the best configuration (Inverse Hydrogen Flow) with the worst. CDM measurements showed an inverse bell-shaped distribution with higher current density values in the external part of the bipolar plate and lower values in the central part and a highly homogeneous temperature distributions in all configurations.

Research on dynamic p-y curves in liquefied sand under cyclic loading conditions

Under dynamic cyclic loads, the pore water pressure in saturated sand rises continuously, which leads to the reduction of horizontal bearing capacity or the damage of the pile foundation. Under dynamic cyclic loads, the existing calculations methods of horizontal bearing capacity of pile foundations were obtained by proposing a reduction factor for the static p-y curve model mostly. Compared with the test results, the soil resistance around the pile obtained by this method is often overvalued and the pile-soil relative displacement has a relative underestimation. As a result, this method is not suitable for pile foundation design. Therefore, the variations of soil resistance around the pile and the pile-soil relative displacement are obtained by analyzing the effect of pore pressure ratio on soil strength around the pile in saturated sand in this paper. The theoretical formulas related to the cyclic vibration times and pore pressure ratio are proposed. The proposed formulas are introduced into the dynamic p-y curve model to obtain the dynamic p-y backbone curve in the process of sand liquefaction. The research results show that the variations of the soil resistance around the pile and the pile-soil relative displacement are related to the pore pressure ratio and the cyclic vibration times during the sand liquefaction. As the cyclic vibration times increases, the pore pressure increases, the soil resistance around the pile decreases and the pile-soil relative displacement increases.

Evaluation of prosthetic screw loosening in all-on-four implant-supported restorations with two different connection systems

Statement of ProblemThe OT BRIDGE connection system can be an alternative to multiunit abutments (MUA) for patients with all-on-four implant-supported restorations. However, the amount of prosthetic screw loosening of the OT BRIDGE in comparison with the MUA used in all-on-four implant restorations is unclear. PurposeThe purpose of this in vitro study was to compare the loss of removal torque in the absence of load and after dynamic cyclic loading between the 2 different connection systems: OT BRIDGE attachment and MUA used in all-on-four implant-supported restorations. Material and methodsFour dummy implants (Neobiotech Co Ltd) were inserted into an edentulous mandibular model according to the all-on-four concept. Sixteen screw-retained restorations were digitally fabricated and assigned to 2 groups: the OT BRIDGE group received 8 restorations connected with OT BRIDGE (Rhein 83 srl); the MUA group received 8 restorations connected with MUA (Neobiotech Co Ltd). Restorations were tightened to the abutments according to the manufacturers’ recommendations by using a digital torque gauge. The removal torque value (RTV) was measured with the same digital torque gauge. After retightening, dynamic cyclic loading was applied by using a pneumatic custom cyclic loading machine. RTV after loading was measured with the same torque gauge. From the RTVs measured, the ratios of removal torque loss (RTL) before and after loading and the difference between before and after loading were calculated. Data were analyzed by using the independent samples t test, paired samples t test, and mixed model analysis of variance (α=.05). ResultsThe OT BRIDGE showed significantly higher RTL before loading ratio (%) than the MUA in anterior abutments (P=.002) and posterior abutments (P=.003), as well as significantly higher RTL after loading ratio (%) in anterior abutments (P=.02). The MUA showed significantly higher RTL difference between before and after loading ratio (%) than the OT BRIDGE in both anterior (P=.001) and posterior abutments (P<.001). In both systems, posterior abutments showed significantly higher RTL after loading ratio (%) than anterior abutments (P<.001). ConclusionsPosterior abutments showed more prosthetic screw loosening than anterior ones in both systems. The OT BRIDGE showed higher total prosthetic screw loosening than the MUA, although this was not significant in posterior abutments after loading. However, the OT BRIDGE was less affected by cyclic loading than the MUA.

Experimental study on wayside monitoring method of train dynamic load based on strain of ballastless track slab

In the long-term service of ballastless track, which constantly bears the cyclic load from high-speed trains, it is important to obtain the long-term mechanical behavior of train dynamic load on the ballastless track. In this paper, a novel wayside monitoring method of train dynamic load is proposed, which takes CRTS III ballastless track as the research object and embeds Fiber Bragg grating (FBG) strain sensors into the track slab. The traditional wayside method installing strain gauges on the rail is used to compared with the sensors embedded in the track slab, which was tested in the field. Then, the time domain and frequency domain information of rail strain and slab strain are analyzed in detail, and the correlation analysis of signals is carried out. Finally, the calculation method of the running trains information and dynamic load is proposed. The results show that the vertical strain level of track slab is low under the action of high-speed train dynamic load. The time history curve shows that the adjacent wheel has obvious coupling effect on the slab strain signal, rather than rail strain. The frequency domain analysis of the signals indicates that the low-frequency components of the rail strain and slab strain have a strong correlation. However, the high-frequency components of train dynamic load are buffered out due to the effect of the fastener system. The mapping relationship between the track slab strain and the dynamic load can be found through calibration test, which provide a novel monitoring method of dynamic train load. The monitoring method can realize the real-time monitoring of train running information and record the long-term train dynamic load cycle law, and provide important parameters for the ballastless track boundary condition model.

Development of novel self-healing strain-hardening cementitious composites (SH2CC) for dynamic cyclic loading conditions using mineral and polymer admixtures

Dynamic cyclic loading commonly encountered in engineering practice can pose great threat to the integrity and durability of concrete infrastructures. Ductile materials with enhanced self-healing performance could provide a promising solution under such conditions. This study proposes and investigates, for the first time, as self-healing SHCC (SH2CC) for dynamic reversed-cyclic (DRC) applications through incorporating a mineral substitute (MS) comprising of reactive MgO and quicklime and triethanolamine (TEA) additive in a high-volume-fly-ash matrix. Different DRC preloads were considered. Results indicated that applying 5% MS combined with 1.5% TEA additive showed optimal crack width control below 12 μm under up to 5 cycles of DRC preloading and the highest potential for mechanical strengthening of modulus of rupture, first cracking strength and flexural stiffness reaching up to 160%, 137% and 210% respectively after healing. Moreover the highest crack sealing efficiency was observed up to 88% under 14d water immersion. Microstructural analysis revealed that MS produced additional hydrates and promoted more carbonates to form in cracks during healing, while TEA effectively paused hydration under air curing but resumed the process upon water contact for massively enhancing crack healing (especially mechanical strengthening). Combining MS and TEA in SH2CC produced complementary healing products both in cracks and fibre-matrix interfaces indicating better filling and bridging of the cracks and demonstrating great potential for enhancing healing performance under aggressive loading conditions.

The dynamic characteristics of saturated remolded loess under cyclic load

Due to the joint development characteristic and macropore structure of loess, it is easy to cause structure collapse under earthquake or artificial vibration. The study on the loess disaster effect and its mechanism under earthquake action is insufficient due to its complexity. Hence, to study the deformation and mechanical properties more accurately, the dynamic characteristics of saturated remolded loess under cyclic dynamic load were tested using a GDS dynamic triaxial instrument in this paper. The test results show that strain and pore water pressure increase gradually at different rates with the development of vibration, and there is an obvious inflection point in the time-history curve of both. When the number of vibrations (N) exceeds this point, the strain increases rapidly, and pore water pressure tends to be stable. Under the action of large amplitude and low-frequency dynamic load, the strain and pore water pressure increase rapidly with fewer vibrations and the deviator stress (q) decreases rapidly, while the sample achieves damage faster with the increase of amplitude. During the application of a dynamic load, the effective stress (p) gradually decreases and its rate of change slows down. Finally, when the saturated remolded loess is subjected to a constant-amplitude dynamic load, the combination of large amplitude and low frequency leads to the failure of the sample in the shortest time.

Dynamic characteristics and energy evolution of granite subjected to coupled static–cyclic impact loading

In many underground rock projects, rock masses are subjected to coupled static–cyclic dynamic loading. In this paper, dynamic tests were carried out on granite specimens using a modified split Hopkinson pressure bar to study the dynamic characteristics and energy evolution of the rock under coupled static–cyclic impact loading. The results show that both the dynamic characteristics and the energy evolution of granite are sensitive to the number of repeated impacts and the confining pressure. Under the same confining pressure, the dynamic increase factor (DIF), dynamic elastic modulus, and transmitted energy ratio decreases, while the cumulative dissipated energy, cumulative specific energy dissipation and dissipated energy density tend to increase as more impact cycles are applied. The effect of confining pressure on enhancing the mechanical property of the rock is pronounced: the peak stress of rocks under confining pressure during cyclic impact is higher than their quasi-static compressive strength, and the DIF increase as the confining pressure increases. However, its effect on the dynamic elastic modulus is fairly insignificant. The confining pressure could change the crack propagation path of the specimens, and the failure mode is mainly a tensile failure, with no obvious axial splitting. By increasing the confining pressure, the energy dissipation capacity of the rock is significantly improved, and its increased rate of internal damage could be slowed down.Graphical abstract

Durability Study of Anode-Supported SOFC with Large-Area Fabricated By 4-Layer Sequential Co-Lamination and GDC Co-Firing Process

Electrolyte-Cathode interfaces are life-threatening regions of solid oxide fuel cells where degradation phenomena occur due to chemical interdiffusion. The Buffer layer is inserted between the electrolyte-cathode to limit the cation exchange across the interface. However, state of the art buffer layer coated by screen printing does not fully prevent cation migration which results in the formation of insulating phases such as La2ZrO7 and SrZrO3. Herein, a reliable four-layered (NiO-YSZ, NiO-CeScSZ, CeScSZ, and GDC) thin film-based anode-supported SOFCs with a large-area (12 cm × 12 cm) were fabricated by sequential co-lamination, in which all cell components perform a distinct role to enhance the interfacial connectivity and packing density of electrolytes. This enhanced connectivity with a highly dense electrolyte (5-6 µm) and buffer layer (2-3 µm) was accomplished on the porous anode support without any structural defects. The single cell (144 cm2) showed a power output of 38 W at a total current of 50 A (700 °C). The Post-tested cell had exceptional micro-structural characteristics and excellent interfacial adhesion and retained its structural integrity during steady and unsteady state operation. Also, the formation of insulating phases and decomposition of the cathode were completely prevented, resulting in a remarkable improvement in durability. The cell with a four-layered structure exhibits an extreme low degradation rate of 0.2% kh-1 under 25 A current and 21 dynamic load cycling conditions, which satisfies the strict benchmark of durability for technology commercialization.