Soil improvement in Qom City under the influence of montmorillonite nanoclay

To investigate the stress distributions on implant-bone interface and fatigue behaviors of biomimetic titanium implant under static and dynamic loading conditions to provide theoretical basis for a new implant which may effectively transfer the stress to surrounding bones. A 3-D finite element model of a posterior mandible segment with an implant bone was constructed by a CAD (Pro/E Widefire 2.0) software. Two different implant models (a dense implant No.1 and a biomimetic implant No.2) were designed. The stress distributions on bone-implant interface under dynamic and static loading conditions were analyzed by Ansys Workbench 10.0 software, as well as the fatigue behavior of the biomimetic implant. The cervical cortical bones in the 2 implants were all high stress region under the same loading condition. The maximum von Mises stress on the interface and high-stress region in the cancellous bone region, and the maximum stress in the root region of the biomimetic implant were lower than those of the dense implant. The stress on the implant-bone interface decreased from the top to the bottom. The stress in the cervical cortical bone under the dynamic loading was 17.15% higher than that of the static loading. There was no significant difference in maximum stress at the cortical bone region between the dynamic and static loading conditions. The maximum stress of the dense implant in the cancellous bone region was 75.97% higher and that in the root region was 22.46% higher than that of the biomimetic implant. The maximum stress on the implant-bone interface was far less than the yield strength of pure titanium. The stress distribution in the cortical region of the biomimetic implant was 7.85% higher than that of the dense implant, and the maximum stress in the cortical bone was smaller than the yield stress of cortical bone. Within the dynamic loading of 50-300 N, the safety coefficient was all higher than 10, and with the increase of loading pressure, interface stress in the cancellous region increased linearly. Under the loading of 300 N in the axial and 25 N in the lingual 45:, the maximum stress was 11.38 MPa. Biomimetic style implant can effectively transfer the implant-bone interface stress to surrounding bones in the cancellous bone and root region, and the structure with the improved design is safe under normal loading pressure.

Maintaining a stable voltage level at the DC bus is crucial to safeguard equipment, ensure a consistent power supply, and enhance system efficiency. A combination of battery storage and photovoltaic (PV) systems is often employed to maintain an equilibrium between energy supply and demand and keep the DC bus voltage within optimal levels. Nonetheless, frequent and rapid charging and discharging of battery storage in dynamic conditions can negatively impact its lifespan. To address this issue, this study utilizes the application of a frequency‐based current controller in battery storage that facilitates smooth charging and discharging operations in transient conditions. The study evaluates the performance of a grid‐tied PV‐based nanogrid (GT‐PVN) system with three distinct configurations: (a) PV system without storage, (b) PV system with battery storage, and (c) PV system with hybrid energy storage system (HESS) under varying dynamic load and irradiance conditions. The results show that the transient performance on DC bus voltage with battery integration is efficiently improved by 0.3%‐0.5% under dynamic irradiance conditions and 0.5%‐1.17% under dynamic load conditions. Further, with HESS installation, the DC bus voltage transients are improved by 0.85%‐1.25% under dynamic irradiance conditions and 0.5%‐1.5% under dynamic load conditions. Moreover, energy storage technology implementation has the potential to decrease energy procurement from the grid by up to 80%. These findings highlight the potential of energy storage technology in mitigating the intermittency and dynamic operational challenges faced by PV systems.

Concrete-to-concrete bedding planes (CCBP) are observed from time to time due to the multistep hardening process of the concrete materials. In this paper, a series of direct/cyclic shear tests are performed on CCBP under static and dynamic normal load conditions to study the frictional behavior effect by the shear velocities, normal impact frequencies, horizontal shear frequencies, normal impact force amplitudes, horizontal shear displacement amplitudes and normal load levels. According to the experimental results, apparent friction coefficient k (k = FShear/FNormal) shows different patterns under static and dynamic load conditions at the stable shear stage. k is nearly constant in direct shear tests under constant normal load conditions (DCNL), while it is cyclically changing with nearly constant peak value and valley value for the direct shear tests under dynamic normal load conditions (DDNL), where k increases with decreasing normal force and decreases with increasing normal force. Shear velocity has little influence on peak values of k for the DCNL tests, but increasing shear velocity leads to increasing valley values of k for DDNL tests. It is also found that, the valley values of k ascend with decreasing impact normal force amplitude in DDNL tests. The changing pattern of k for the cyclic shear tests under constant and dynamic normal load conditions (CCNL and CDNL tests) are similar, but the peak value of k is smaller in CDNL tests than that in CCNL tests. Normal load levels, shear displacement amplitudes, vertical impact frequencies, horizontal shear frequencies and normal impact force amplitudes have little influence on the changing pattern of k for the cyclic shear tests. The tests of this study provide useful data in understanding the frictional behavior of the CCBP under distinct loadings, and these findings are very important for analyzing the stability of the jointed geotechnical structures under complicated in situ stress conditions.

This study aimed 1) to determine whether talar cartilage deformation measured via ultrasonography (US) after standing and hopping loading protocols differs between chronic ankle instability (CAI) patients and healthy controls and 2) to determine whether the US measurement of cartilage deformation reflects viscoelasticity between standing and hopping protocols. A total of 30 CAI and 30 controls participated. After a 60-min off-loading period, US images of the talar cartilage were acquired before and after static (2-min single-leg standing) and dynamic (60 single-leg forward hops) loading conditions. We calculated cartilage deformation by assessing the change in average thickness (mm) for overall, medial, and lateral talar cartilage. The independent variables include time (Pre60 and postloading), condition (standing and dynamic loading), and group (CAI and control). A three-way mixed-model repeated-measures ANCOVA and appropriate post hoc tests were used to compare cartilage deformation between the groups after static and dynamic loading. After the static loading condition, those with CAI had greater talar cartilage deformation compared with healthy individuals for overall (-10.87% vs -6.84%, P = 0.032) and medial (-12.98% vs -5.80%, P = 0.006) talar cartilage. Similarly, the CAI group had greater deformation relative to the control group for overall (-8.59% vs -3.46%, P = 0.038) and medial (-8.51% vs -3.31%, P = 0.043) talar cartilage after the dynamic loading condition. In the combined cohort, cartilage deformation was greater after static loading compared with dynamic in overall (-8.85% vs -6.03%, P = 0.003), medial (-9.38% vs -5.91%, P = 0.043), and lateral (-7.90% vs -5.65%, P = 0.009) cartilage. US is capable of detecting differences in cartilage deformation between those with CAI and uninjured controls after standardized physiologic loads. Across both groups, our results demonstrate that static loading results in greater cartilage deformation compared with dynamic loading.

Sliding wear of cast zinc-based alloy bearings under static and dynamic loading conditions

The Ryukyu limestone formation is not assumed to be a suitable load bearing foundation in Ryukyu Archipelago. The characteristics of Ryukyu limestone with various porosity under static and dynamic conditions have been investigated by the authors. Furthermore, the behavior of the interface between piles and Ryukyu limestone are tested using large-scale dynamic shear testing device. Some model piles founded on Ryukyu limestone are subjected to static and dynamic loads to check their deformation response and their load-bearing capacity. The authors will explain fundamental studies on foundations on Ryukyu Limestone Formation under static and dynamic loading conditions and present the outcomes of these studies and discuss their implications on bridge piles.

Brittle failure of high toughness steel structures tends to occur after ductile crack initiation/propagation. Damages to steel structures were reported in the Hanshin Great Earthquake. Several brittle failures were observed in beam-to-column connection zones with geometrical discontinuity. It is widely known that triaxial stresses accelerate the ductile fracture of steels. The study examined the effects of geometrical heterogeneity and strength mismatches (both of which elevate plastic constraints due to heterogeneous plastic straining) and loading rate on critical conditions initiating ductile fracture. This involved applying the two-parameter criterion (involving equivalent plastic strain and stress triaxiality) to estimate ductile cracking for strength mismatched specimens under static and dynamic tensile loading conditions. Ductile crack initiation testing was conducted under static and dynamic loading conditions using circumferentially notched specimens (Charpy type) with/without strength mismatches. The results indicated that the condition for ductile crack initiation using the two parameter criterion was a transferable criterion to evaluate ductile crack initiation independent of the existence of strength mismatches and loading rates.

This research was conducted to detect the effect of static load, dynamic condition, and rainfall on slope stability. The studied parameters are: rainfall intensity, static load, frequency, soil suction variation, and the form of slope failure. A laboratory model was manufactured in the form of a box with dimensions of (2000 × 1000 × 1450) mm that slides on a rail installed on the ground and moved by a dynamically generated system and provided with a controlled rainfall system. To clarify the rainfall effect with dynamic conditions on the slope stability, the effect of rainfall intensities of (20, 30, and 40) mm/h were studied on a series of three model tests. Two stages of a rainfall (duration of each one = 1 h) have been applied to the soil sample. After each stage, the model was left for 24 h to allow the water infiltration process into the soil layers. Dynamic conditions were enjoined as (20) mm of one direction horizontal vibration displacement at frequencies of (0.5, 1.0, and 2.0) Hz. The time duration for each frequency value is (3) minutes. The acceleration during vibrations was measured through the test by an accelerometer that was placed on a shaking table and inside the soil. The main result shows that the rainfall and dynamic load have negatively affected the slope bearing capacity. It decreased from (408) kPa at the static test to (204, 127, and 102) kPa at the three rainfall tests, respectively. On the other hand, results also revealed that the soil suctions were decreased after the application of rainfall on the slope model.KeywordsSlope stabilityDynamic conditionRainfallNumerical analyses

The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition. Based on the in-site geological conditions of Longgu coal mine, this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition. Results showed that under the static loading condition, the maximum vertical stress, deformation and failure range are large, where the stress concentration coefficient is 1.64. The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm, respectively. Then, under the dynamic and static combined loading condition: (1) The influence of dynamic load frequency on the two-sides is more obvious; (2) The dynamic load amplitude has the greatest influence on the stress concentration degree, and the plastic failure tends to develop to the deeper; (3) With the dynamic load source distance increase, the response of surrounding rock is gradually attenuated. On this basis, empirical equations for each dynamic load conditions were obtained by using regression analysis method, and all correlation coefficients are greater than 0.99. This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.

The constitutive modelling of geosynthetic–geosynthetic interfaces is essential to predict the performance of the engineering structures such as landfills, flood control dykes and geotextile encapsulated-sand systems for the protection of shore. This article presents a mathematical model to simulate the shear stress/force–displacement behaviour of the interfaces involving smooth geomembrane and nonwoven geotextile under static and dynamic loading conditions. The model is the extension of an existing technique developed for predicting the soil-structure interface shear behaviour under static loading conditions. The proposed model can predict the non-linear pre-peak and the post-peak strain softening/hardening behaviour of the interfaces observed during the laboratory testing. The shear stress/force–displacement response of the interfaces has been modelled by dividing it into three parts: pre-peak, peak and post-peak behaviour. Subsequently, the modelling parameters are obtained using the results from the laboratory direct shear tests and fixed–block type shake table tests conducted on these interfaces. Finally, the shear stress/force–displacement response of the interfaces is evaluated and compared with the experimental results. The predicted shear stress/force–displacement response of the interfaces is found to be in good agreement with the experimental data for both static and dynamic loading conditions.

Rockbolts are widely used as an underground support element to resist the convergence and maintain the stability of excavations. However, shear failure of rockbolts is increasingly observed in jointed rock mass of underground tunnels, especially after being subjected to seismic events. At present, understanding of the mechanical response of rockbolts subjected to seismic or dynamic loading in shear is still unclear. To investigate the shear performance of rockbolts under dynamic loading condition, a series of tests were conducted using a drop mass of up to185 kg from a maximum height of 3 m based on a double shear test (DST) system. Three variables were examined in the laboratory test including rockbolt diameter (8 mm and 16 mm), installation angle (90° and 45°) and input energy (drop height). The duration of the impact was 10–12 ms from release of the drop mass to first contact. By evaluating the DST system’s displacement/velocity/acceleration–time characteristic and the amount of energy absorption, the shear performance of rockbolt was assessed. When sufficient energy is applied into the DST system, the deformation of the rockbolt is dominated by localized shear force. The transient force can rupture the rockbolt with little bending and without any obvious tensile elongation. It was found that the averaged dynamic shear load is less than the peak static shear load whether horizontally installed or installed at an angle. In conclusion, the effectiveness of rockbolts in resisting shear stress can differ significantly under static loading and dynamic loading condition; the difference is reflected in the level of shear deformation and amount of energy absorption. The shear capacity of a rockbolt under 1 s−1 strain rate can be determined by the energy absorbed and average dynamic load. This approach can be applied to the support system design in rockburst-prone condition.

Understanding the deformation and cracking behavior of Cr-based coatings deposited by hybrid direct current and high power pulse magnetron sputtering: From nitrides to oxynitrides

Vibration is one of the most common causes of avionic device failure. The aircraft's avionic equipment must be able to resist high vibrations. Because it is not possible to place vibration equipment directly on the shaker table of a vibration machine, a mechanical structure known as a fixture is used to place the equipment and the machine. The proposed work's main goal is to develop the overall performance of the vibrating fixture to study the vibration characteristics of that particular structure at static and dynamic loading conditions, as well as performing random vibration analysis on various types of fixtures made up of Aluminum 2024 andAZ31B magnesium alloy. In this scenario, the natural frequencies, strength, strainand deformation of the structure are calculated at static load and dynamic loading conditions. By determining all of these findings, the proper selection of material for vibrating fixture can be done for mechanical design analysis.

A typical ground support system designed to safely excavate mine openings in rock consist of rockbolts, rockbolt plates, steel mesh, structural support lines, and shotcrete. The rockbolt plate, which connects the embedded rockbolt to the surface support, is a crucial part of a ground supporting system and is often the weakest link. Matching the correct embedded rockbolt to the rockbolt plate is crucial for proper ground support system interaction. If the selected plate is too weak, it will deform and will prevent full rockbolt yielding. If the plate is too strong, the system will take a lower cumulative load due to the lost energy dissipation potential of the plate and there will be no indication of rockbolt load due to the hindering of plate deflection. The rockbolt plate should deform during the yielding phase of the rockbolt, and fail after the reinforcing element. The ground support system must accommodate static and dynamic loading conditions and mechanical properties must be characterized to optimize rockbolt density and safety factor. CanmetMINING has developed a static and dynamic rockbolt plate testing regime using industry standards and innovative testing methods. The static testing methods are modified versions of standardized deflection tests. The dynamic testing methods were developed by CanmetMINING and include novel testing methodology. This paper describes the instrumentation and data acquisition methods, testing methodology, data processing method, and analysis of the static and dynamic test results from the tests. INTRODUCTION As the demand for critical minerals increases, there is additional pressure on mining operations to exploit new ore reserves, often in areas with more difficult ground conditions (Plouffe et al., 2008). In some cases, these orebodies are now found at depth, which poses additional ground control challenges due to higher in-situ stress conditions. To mitigate ground control instability, mining and ground control engineers carefully select appropriate reinforcement systems that may include rockbolts, mesh, and/or shotcrete (Potvin et al., 2010). At CanmetMINING's Ground Support Testing Laboratory in Ottawa, Ontario, Canada, linear reinforcement elements (i.e., rockbolt systems) can be evaluated under static and dynamic conditions. This detailed characterization of ground reinforcement elements is important for design engineers to understand the behavior of the ground reinforcement and therefore specify the appropriate reinforcement to counteract anticipated failure mechanism(s). This current research program focusses on the development of a method for evaluating rockbolt plate response under static and dynamic loading conditions for the purpose of improving plate characterization and contributing to improved rockbolt performance.

Therapeutic lubricant injections of hyaluronic acid are a relatively recent treatment for osteoarthritis. Their efficacy, however, in vivo has been subject to much debate. Frictional properties of cartilage-cartilage contacts under both static and dynamic loading conditions have been investigated, using healthy cartilage and cartilage with a physically disrupted surface, with and without the addition of a therapeutic lubricant, hyaluronic acid. Most of the cartilage friction models produced typical time-dependent loading curves, with a rise in static friction with loading time. For the dynamic loading conditions the rise in friction with loading time was dependent on the spatial (and time) variation in the load on the cartilage plate. For sliding distances of 4 mm or greater, when the cartilage plate was unloaded during sliding, the dynamic friction remained low whereas, with shorter sliding distances, the dynamic friction increased with increasing loading time. Static friction was higher than dynamic friction (under the same tribological conditions). The 'damaged' cartilage models produced higher friction than healthy cartilage under equivalent tribological conditions. It was shown that hyaluronic acid was an effective boundary lubricant for articular cartilage under static conditions with both healthy and damaged cartilage surfaces. Hyaluronic acid was less effective under dynamic conditions. However, these dynamic conditions had low friction values with the control lubricant because of the effectiveness of the intrinsic biphasic lubrication of the cartilage. It was only under the tribological conditions in which the cartilage friction was higher and rising with increasing loading time because of depletion of the intrinsic biphasic lubrication, that the role of hyaluronic acid as an effective therapeutic lubricant was demonstrated.