Load Depth Research Articles

Development of a Relation between Return Period Values of Annual Maximum Snow Load and Snow Depth and Its Implication in Structural Reliability for Northeastern China

Development of a Relation between Return Period Values of Annual Maximum Snow Load and Snow Depth and Its Implication in Structural Reliability for Northeastern China

Deformation Stability Analysis of Foundation of Taijiao High-speed Railway above the Mined-out Area Affected by Rainfall

Aiming to the requirements of potential safety risk control along the high-speed railway, taking the foundation of Taijiao high-speed railway above the mined-out area of Dianshang, China as the engineering background, a mechanical model of composite rock strata of the foundation was established based on the theory of thin plate. Combined with the catastrophe theory, the evaluation system of the foundation stability was constructed. Using the self-developed similar model test and rainfall device, the deformation stability of the foundation under the condition of heavy rainfall and dynamic loading of the high-speed railway was analyzed. Results show that the maximum influence depth of the dynamic loading and heavy rainfall on the foundation is about 20 m, and the further compaction of the foundation cracks is the main factor leading to the subsidence of the foundation above the mined-out area. In addition, the increase of the number of longitudinal tensile cracks in the foundation, which gradually plays a dominant role in the new cracks, shows an exponential growth trend. Being affected by the continuous heavy rainfall, the deformation evolution of the foundation displays four stages: the initial stabilization, the slow deformation, the first sudden-jump, and the secondary sudden-jump stages. Among them, the surface's maximum deformation occurs in the secondary sudden jump stage. The conclusions obtained in this study provide a theoretical basis for the stability evaluation and treatment of the foundation of the high-speed railway above the mined-out area.

A low‐cost phased array antenna with axially loaded dielectric laminas

A low-cost phased array antenna, consisting of waveguide radiators, dielectric phase shifters and a cooperated feeding network, is proposed and experimentally validated in this paper. The required progressive phases are obtained by controlling the loading depths of dielectric laminas, which are axially inserted into the rectangular channels. The phase difference among channels is determined by the lamina length, the loading depth and the dielectric constant. Theoretically arbitrary phases can be achieved with these design freedoms. A validation prototype of a 1 × 4 array antenna operating around 10 GHz with an element spacing of 0.735λ0 demonstrates a continuous beam steering range of ±23°, which is consistent with theoretical predictions.

Estimation of Crust and Lithospheric Properties for Mercury from High-resolution Gravity and Topography

We have analyzed the entire set of radiometric tracking data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. This analysis employed a method where standard Doppler tracking data were transformed into line-of-sight accelerations. These accelerations have greater sensitivity to small-scale features than standard Doppler. We estimated a gravity model expressed in spherical harmonics to degree and order 180 and showed that this model is improved, as it has increased correlations with topography in areas where tracking data were collected when the spacecraft altitude was low. The new model was used in an analysis of the localized admittance between gravity and topography to determine properties of Mercury’s lithosphere. Four areas with high correlations between gravity and topography were selected. These areas represent different terrain types: the high-Mg region, the Strindberg crater plus some lobate scarps, heavily cratered terrain, and smooth plains. We employed a Markov Chain Monte Carlo method to estimate crustal density, load density, crustal thickness, elastic thickness, load depth, and a load parameter that describes the ratio between surface and depth loading. We find densities around 2600 kg m−3 for three of the areas, with the density for the fourth area, the northern rise, being higher. The elastic thickness is generally low, between 11 and 30 km.

New development of a solar electrochemical raceway pond reactor for industrial wastewater treatment

In this work, a solar electrochemical-raceway pond reactor (SEC-RPR) is used to treat textile industrial wastewater by solar photoelectron-Fenton (SPEF) at pilot plant scale for the first time. The SEC-RPR is composed of an electrochemical filter press-cell coupled to RPR, where H2O2 is electro-generated. A complete study about experimental variables such as current, catalyst concentration, pollutant load or liquid depth is conducted based on methyl orange removal, mineralization and decolorization. Validation of the SPEF process using SEC-RPR reached more than 80% of mineralization, as well as the complete decolorization of the solution. The good performance of the SPEF treatment in the new SEC-RPR led to quick degradation kinetics, mainly due to the synergetic action of solar radiation and good distribution of H2O2 electrogenerated in the photoreactor. 100% Methyl Orange degradation was achieved after 150, 60, 45, 30 and 20 min of reaction time applying current density equal to 5, 10, 20, 40 and 60 mA cm−2, respectively. However, the increase of current density decreased the mineralization current efficiency. Up to 10 aromatics intermediates and 5 short-chain carboxylic acids were identified by LC-MS and HPLC analysis and a reaction pathway for MO mineralization by SPEF is proposed. This study represents an essential preliminary step towards the development of the first SEC-RPR at demo scale.

Research on Critical Load of Lithium Niobate Crystal Lapping

The elastic modulus and hardness of lithium niobate crystals were obtained by nanoindentation technology, and critical load and critical indentation depth range were determined by AFM by indentation morphology under different loads. According to the normal distribution characteristics of abrasive grains, the critical load model of lapping was deduced, and the critical load of lithium niobate during lapping process under different grain sizes was obtained. It was verified using a single-factor experiment in which experimental results were consistent with theoretical research.

Characterization of fracture toughness for surface-modified layer of 18CrNiMo7-6 alloy steel after carburizing heat treatment by indentation method

Advanced processing of a workpiece, such as by carburization, will modify its surface. Accurate measurement of fracture toughness of such a surface-modified layer is important for fatigue resistance manufacturing, but is still a challenge. A method to characterize fracture toughness of the surface-modified layer using a layering treatment and continuous indentation test is proposed. The load–depth curve obtained from continuous indentation testing with a Vickers indenter was used to characterize the fracture toughness of the surface-modified layer produced by carburizing heat treatment of 18CrNiMo7-6 alloy steel. Variation of fracture toughness with depth of the surface-modified layer was determined.

Customized design of horizontal flow constructed wetlands employing secondary datasets

Values of areal removal rate constant (k, m/day) were derived by employing a dataset of 74 horizontal flow constructed wetlands (HFCWs) using P-k-C* approach, which showed large variation (0.006–0.40 m/day) as these systems were largely under-loaded. This dataset was classified based on substrate loading rates, temperature, and depth to reduce the SDs of k values among the subsets. Further, the k values for organics removal were optimized by eliminating data of 10%, 20% and 30% of the most underloaded HFCWs, which led to a sharp reduction in observed SDs from 84.74% to 4.85%; 116.48% to 3.42%; and 114.70% to 6.89% respectively for the aforementioned scenarios for organics removal. These stable k values can be adopted for area calculations for optimizing the design of HFCWs and the computations made here will help identify the limiting nutrient that would govern the design under specific requirements.

Artificial Neural Networks for Predicting Plastic Anisotropy of Sheet Metals Based on Indentation Test.

This paper mainly proposes two kinds of artificial neural network (ANN) models for predicting the plastic anisotropy properties of sheet metal using spherical indentation test, which minimizes measurement time, costs, and simplifies the process of obtaining the anisotropy properties than the conventional tensile test. The proposed ANN models for predicting anisotropic properties can replace the traditional complex dimensionless analysis. Moreover, this paper is not limited to the prediction of yield strength anisotropy but also further accurately predicts the Lankford coefficient in different orientations. We newly construct an FE spherical indentation model, which is suitable for sheet metal in consideration of actual compliance. To obtain a large dataset for training the ANN, the constructed FE model is utilized to simulate pure and alloyed engineering metals with one thousand elastoplastic parameter conditions. We suggest the specific variables of the residual indentation mark as input parameters, also with the indentation load–depth curve. The profile of the residual indentation, including the height and length in different orientations, are used to analyze the anisotropic properties of the material. Experimental validations have been conducted with three different sheet alloys, TRIP1180 steel, zinc alloy, and aluminum alloy 6063-T6, comparing the proposed ANN model and the uniaxial tensile test. In addition, machine vision was used to efficiently analyze the residual indentation marks and automatically measure the indentation profiles in different orientations. The proposed ANN model exhibits remarkable performance in the prediction of the flow curves and Lankford coefficient of different orientations.

Effect of irradiation temperature on the nanoindentation behavior of P92 steel with thermomechanical treatment

The nanoindentation behavior of P92 steel with thermomechanical treatment under 3.5 MeV Fe13+ ion irradiation at room temperature, 400 and 700 °C was investigated. Pop-in behavior is observed for all the samples with and without irradiation at room temperature, while the temperature dependence of pop-in behavior is only observed in irradiated samples. The average load and penetration depth at the onset of pop-in increase as the irradiation temperature increases, in line with the results of the maximum shear stress. Irradiation induced hardening is exhibited for all irradiated samples, but there is a significant reduction in the hardness of sample irradiated at 700 °C in comparison to the samples irradiated at room temperature and 400 °C. The ratio of hardness to elastic modulus for all samples decreases with increasing penetration depth except for samples at 700 °C. With the increasing of irradiation temperature, the ratio of the irreversible work to the total work gradually decreases. In contrast, it increases for samples without irradiation.

Numerical study on the suction force of jack-up mat foundation on marine clay seabed

A deep layer of soft clay is widely present on the seabed in the offshore area of China. The traditional jack-up spudcan faces the problem of difficult insertion and extraction in clay seabed. Jack-up mat foundation is more suitable in soft clay than spudcan for its lower requirements on bearing capacity. Due to the poor permeability of clay, the uplifting process of the mat foundation needs to overcome a large soil suction force. In this study, three-dimensional numerical model is established to investigate the suction force of jack-up mat foundation on marine clay seabed. The elastoplastic constitutive model, which can describe the structural and over-consolidation of soft marine clay seabed, was embedded in commercial software ABAQUS through UMAT subroutine. The cohesive contact model was adopted to stimulate the interaction between mat foundation and the seabed soil. Field test was conducted to verify the accuracy of the numerical model. Then, the effects of degree of over-consolidation, degree of structural, depth of clay, interface stiffness and eccentric uplift loading on suction force are studied in detail. Numerical results show that the effects of degree of over-consolidation and structural of soil have significant influence on the suction force. The suction force first increases rapidly and then decrease gradually as the thickness of the upper dimensionless clay layer increases. With the increase of the uplift eccentricity, the suction force reduces continuously.

Inverse Identification of Single-Crystal Plasticity Parameters of HCP Zinc from Nanoindentation Curves and Residual Topographies.

This paper investigates the orientation-dependent characteristics of pure zinc under localized loading using nanoindentation experiments and crystal plasticity finite element (CPFEM) simulations. Nanoindentation experiments on different grain orientations exhibited distinct load–depth responses. Atomic force microscopy revealed two-fold unsymmetrical material pile-up patterns. Obtaining crystal plasticity model parameters usually requires time-consuming micromechanical tests. Inverse analysis using experimental and simulated loading–unloading nanoindentation curves of individual grains is commonly used, however the solution to the inverse identification problem is not necessarily unique. In this study, an approach is presented allowing the identification of CPFEM constitutive parameters from nanoindentation curves and residual topographies. The proposed approach combines the response surface methodology together with a genetic algorithm to determine an optimal set of parameters. The CPFEM simulations corroborate with measured nanoindentation curves and residual profiles and reveal the evolution of deformation activity underneath the indenter.

Review on the kerogen deformation mechanism

Shale gas is unconventional natural gas energy stored in shale, and is one of the important substitutes for conventional oil and gas resources. Since amorphous kerogen is the main component of shale organic matter and has a high degree of deformation ability, it is a key factor to improve shale gas recovery. As an emerging mining technology CS-EGR, the CO2 injection method replaces the hydraulic pressure method, thereby alleviating the greenhouse effect and energy crisis. The basic understanding of the microscopic mechanism of the multicomponent competitive adsorption and diffusion of the adsorbate in kerogen will provide a theoretical basis and guidance for further understanding of kerogen deformation and further CS-EGR. Starting from the summary of experimental research, this paper systematically summarizes the kerogen model used for kerogen deformation research and discusses the effects of adsorbate, load, moisture, temperature, pressure, and geological depth on different kerogen structures of different maturity. The effect of kerogen deformation.

Study on Deformation Characteristics of Extended Highway in Operation Period

Highway widening has become an effective way to improve the carrying capacity of existing expressways. However, assume that the differential settlement between the new and the old subgrades is not controlled. In that case, it will lead to longitudinal cracks on the pavement, which will seriously affect the safety of vehicles. In this study, the variations of elastic modulus and dynamic elastic modulus of new and old subgrades under traffic load were studied by tests. A hyperbolic model of dynamic elastic modulus increasing with strain is proposed. The numerical calculation model of new and old subgrades under traffic load is established. The deformation characteristics of new and old subgrades without treatment measures and setting up geogrid and geocell are studied. The main conclusions are as follows: (1) with the increase of traffic load and subgrade depth, the elastic modulus changes significantly in the early stage and small in the later stage. (2) Under the condition of no treatment measures, the vertical and horizontal deformation of the subgrade surface show a trend of increasing and then decreasing with the distance from the center line of the subgrade. (3) Setting geogrid and geocell can effectively reduce the differential settlement of the old and new subgrades. (4) The effect of setting geogrid to reduce the differential settlement of old and new subgrades is better than that of setting geogrid.

A comparison study of mechanical change and chemical disorder in 4H-SiC irradiated with Si5+ and He2+ at room temperature

The effects of ion mass on lattice disorder of 4H-SiC irradiated with Si and He ions at room temperature to doses of 0.04 displace per atoms (dpa) to 4.0 dpa were investigated by nano-hardness and Raman spectroscopy. The changes in mechanical property and chemical disorder after Si and He irradiation were compared. “Pop-in” phenomena were observed in the profile of load vs. penetration depth before and after ion irradiation. The profile of hardness value in the damaged layer exhibited “M” shape for He irradiation, while it decreased monotonously with increasing Si dose. The hardness value for Si irradiation to a dose of 0.08 dpa was almost equal to the value of He irradiation as high as 0.4 dpa. The Raman intensity of typical scattering peaks showed that it was smaller after Si irradiation than after He irradiation at the same dose. The possible reasons of more survival lattice defects in the Si-irradiated 4H-SiC are discussed.

Do adjunctive antimicrobials improve the outcome of non-surgical peri-implantitis treatment?

Design This study was a single-centre, single-blind, controlled parallel group randomised control trial.Case selection Participants included those referred to The Hague Clinic for Periodontology in the Netherlands. The selection criteria included patients diagnosed with peri-implantitis, defined as marginal bone loss of >2 mm in addition to bleeding or suppuration on probing and a probing depth of >5 mm. The study was carried out over seven years and involved a control group (full mouth non-surgical peri-implantitis treatment) and a test group (non-surgical peri-implantitis treatment combined with systemic antimicrobials). Data analysis Sixty patients were recruited (30 allocated to each group) and 57 completed follow-up and were analysed according to the intention to treat principle. The patients were reviewed monthly and clinical data according to the parameters being measured were recorded. Microbiological analysis was also carried out. The power calculation was based upon the primary outcome measure of interest: bleeding on probing (BoP).Results The primary outcome parameter being measured was change in full mouth BoP and this study concluded that there were no significant differences in bleeding scores between the control and intervention at three months post-treatment. Secondary outcome parameters being measured included full mouth peri-implant and periodontal plaque scores (PS, %), clinical attachment levels, suppuration scores (SS, %), mean probing depths, mean peri-implant bone levels, change in detection frequency of periodontal pathogen species over the study duration, adverse event occurrence and need for additional surgical treatment. No significant differences were noted between the two groups for any clinical parameter.Conclusions Antimicrobial therapy does not lead to improved patient outcomes in terms of reducing microbial load and reducing pocket depth. Based on this study, there is inadequate evidence to support the use of adjunctive antimicrobials for the non-surgical treatment of peri-implantitis.

Shock-induced large-depth gradient microstructure in commercial pure titanium subjected to explosive hardening

Explosive hardening of commercial pure titanium plate was conducted by a thin-layer high-detonation-velocity explosive. The nanoindentation and Vickers hardness tests of the treated titanium plates along the depth of shock loading were performed. The microstructures along the depth were characterized by using different methods, including X-Ray Diffraction, Optical Microscopy, Electron Back-Scattered Diffraction and Transmission Electron Microscopy. Experimental results showed that large-depth gradient hardness distribution with depth of 2.5 mm was produced in CP titanium by explosive hardening. There are two gradient hardenedlayers, ultra-hardened layer with a depth of 0–40 μm and a hardness increase of ∼400%, sub-hardened layer with a depth of 40 μm-2500 μm and a hardness increase of 54.3%. Gradient microstructures with different characteristics were observed, including gradient α-ω phase transition, gradient grain size, gradient twining and gradient dislocation. The area of gradient microstructure is consistence with that of gradient hardness distribution. Grain refinement/α-ω phase transition mainly contributed to hardness sharply increasing in ultra-hardened layer. High-density dislocation/twining mainly contributed to hardness increasing in the sub-hardened layer. Finally, the formation mechanism of gradient microstructures and grain refinement mechanism was detailly discussed.

Dynamic failure behavior of Jinping marble under various preloading conditions corresponding to different depths

To better understand the dynamic mechanical properties of rock at different depths, a method to simplify the stress characteristics of the rock mass surrounding a circular cavern was developed, and a series of impact tests involving high-speed photographic monitoring were performed on deep marble drilled in situ in the China Jinping Underground Laboratory at nine preloaded uniaxial stress levels (corresponding to simulated depths of 0, 100, 300, 600, 700, 900, 1200, 1500 and 1800 m). The results indicated that the strain rate sensitivity of the dynamic strength of Jinping marble decreased with the simulated depth, and obvious ductile deformation and failure characteristics occurred under high-energy dynamic loading and great depths. According to the fragmentation records, cracks clearly initiated and propagated mainly along the axial direction , and the observed failure patterns were classified into three typical modes: striped fragmentation (depth<600 m and strain rate<75/s), cylindrical surface spalling (depth≥600 m and strain rate<75/s) and comminution failure (strain rate≥75/s). Additionally, energy characteristics analysis revealed that the dissipative energy density e f and energy absorption efficiency A C exhibited significant depth differences and strain rate correlations, which corresponded well to the failure characteristics of the studied marble. Finally, an improved microcrack model considering the strain rate and simulated depth was established to characterize the dynamic mechanical behavior of the investigated marble, and the theoretically predicted strength values agreed well with the experimental values. • The dynamic failure behavior of rock under coupled static-dynamic loading conditions corresponding to different depths is revealed. • Striped fragmentation failure and a high strain rate sensitivity of the dynamic rock strength occur in shallow marble, while cylindrical surface spalling failure and a low strain rate sensitivity of the dynamic rock strength are observed at greater depths. • An improved microcrack model for dynamic rock strength prediction is established, which overcomes the limitation of previous models that lack comprehensive consideration of static preloading and strain rate conditions.

Mechanic properties modification of SiO2 thin films by femtosecond laser

SiO2 films were deposited on fused silica substrates by ALD technology. The properties of ALD SiO2 films irradiated by femtosecond laser were investigated. Raman spectra confirms the molecular structure of SiO2 films is identical to that of fused silica. The relative content of the three- and four-membered ring of films irradiated is increased. Photoluminescence (PL) spectra shows that the defects of the films irradiated by laser of 10% power ratio are reduced. Indentation tests show that both hardness and elastic modulus are decreased by 1.8%, their standard deviations are decreased by 73.8% and 46.8% respectively. Scratch experiments exhibit that femtosecond irradiation improves the bonding performance of the films, and the critical load is increased by 10.8%. Meanwhile, the standard deviations of the lateral load and penetration depth are decreased on average from 0.0636 to 0.0336, from 8.3478 to 1.6747, individually. The plastic deformation ratio of the films are increased from 19.80% to 28.89%. The morphology and cross section of the scratches observed by optical microscopy and confocal laser microscopy suggest that the damage form of the films irradiated by laser is changed from the brittle fracture removal form to the mixed removal form of brittle fracture and plastic.

Diagnosis of Mechanical Properties with Instrumented Indentation Technique Using Multiple Pyramid Indenters

Abstract This paper presents a semi-nondestructive method for diagnosing mechanical properties through an instrumented indentation technique using multiple pyramid indenters with different dihedral angles. In the developed method, an approximated true stress–true strain curve can be obtained from the plots of the representative stress–representative strain relation estimated for each of the four different pyramid indenters. A functional relation between the representative stress and the indentation load–depth curve was derived from dimension analysis using the π theorem. Then, specific values of constants in the functional equation were determined for each of the pyramid indenters using experimentally validated finite element analysis of the instrumented indentation test. Meanwhile, the representative strain levels were quantified according to the dihedral angle of the pyramid indenters. The developed method was applied to estimate the true stress–true strain curve of non- and prestrained steels. As a result, a small difference could be seen only in non-strained steel with Lüders strain, but the estimated results are nearly in agreement with those obtained by tensile tests. The approximated curves were also used to estimate yield stress and prestrain. The results showed that estimation accuracy of yield stress was better than that based on an empirical correlation with Vickers hardness, and the estimated values of prestrain were in good agreement with those actually introduced by tensile tests. It is expected that the developed multi-indenter method will become useful for semi-nondestructively diagnosing mechanical properties for steel.