Maximum Damage Depth Research Articles

A Study on the Thermodynamic Response of Double-Armed Thin-Walled Piers under an FRP Anti-Collision Floating Pontoon Fire

Abstract: As a potential fire scenario for bridge structures, the safety impact of an FRP anti-collision floating pontoon fire on bridge structures cannot be ignored. Taking the FRP anti-collision floating pontoon fire that occurred in a continuous rigid-frame bridge as the engineering background, the damage condition of the actual bridge fire scene was first investigated. In addition, FDS 5.3 software was used to simulate the FRP anti-collision floating pontoon fire scenario. Furthermore, the thermal–structural coupling method was used to investigate the thermodynamic response of double-armed thin-walled piers under fire. The results show that the FRP anti-collision floating pontoon fire causes localized concrete carbonization and spalling on the surface of the P2 pier, and the FRP anti-collision floating pontoons are largely destroyed. The fire has the greatest impact on the P2-1 pier, with the highest temperature of 667 °C on the windward side and the highest temperature of 326 °C on the leeward side. The temperature impact range is 6 m above the bearing platform, and the maximum damage depth of pier body concrete is 84.58 mm. The deformation and stress of the P2 pier under fire do not show significant changes and do not exceed the allowable limits for structural deformation and material stress. Therefore, the impact of this fire accident on the structural safety of the continuous rigid-frame bridge is minor. This study's results provide reliable guidance for the fire safety assessment and post-fire structural repair of the continuous rigid-frame bridge.

Electrochemical characteristics and damage mechanism in scrubber washing water of UNS N08367 with plasma ion nitriding and electropolishing

In this investigation, electropolishing and plasma ion nitriding are applied to super austenitic stainless steel for the purpose of improving its corrosion and pitting resistance. Electrochemical experiments are conducted with washing water collected directly from the ship’s scrubber. After electropolishing, the surface roughness is improved by about 73.6% compared to mechanical polishing. After plasma ion nitriding, CrN (precipitate), Fe4N (compound), and γN (solid solution) are observed on the surface. The thickness of the layer formed on the surface is measured to be about 10 μm. A hysteresis loop is observed in the cyclic potentiodynamic polarization curves of mechanical polishing and electropolishing, and the areas are calculated as 23.33 mW cm−2 and 0.17 mW cm−2, respectively. The polarization curve of plasma ion nitriding presents perfect passivation characteristics. Accordingly, mechanical polishing and electropolishing reveal local corrosion, whereas plasma ion nitriding presents a tendency towards general corrosion. In the mechanical polishing, electropolishing, and plasma ion nitriding, the corrosion current densities are 0.665 μA cm−2, 0.093 μA cm−2, and 16.47 μA cm−2, respectively, and the maximum damage depth is observed to grow progressively smaller from plasma ion nitriding to electropolishing and then mechanical polishing.

Molecular dynamics simulation of the scratching process of GaAs with different crystal orientations.

In order to further improve the manufacturing technology of resonator facet of GaAs (gallium arsenide)-based laser, the scratching process of GaAs was simulated by molecular dynamics. Models of GaAs crystals with different orientations, including GaAs [100], GaAs [110], and GaAs [111], were generated, followed by scratch simulations on these models. The surface characteristics of scratches, damage width, subsurface damage, stack height, and the distribution and activity characteristics of dislocations were analyzed based on the simulation results. The results show that there are obvious anisotropy in the deformation of different crystal orientation during the scratching process of GaAs. Surface features, damage width, subsurface damage, and dislocation dynamics during scraping in GaAs crystals strongly depend on crystal orientation. It was also observed that GaAs exhibits distinct characteristics of dislocation activity during the scratching process, depending on its crystal orientation. In addition, GaAs [110] crystal direction has the smallest maximum damage width and subsurface damage depth. The maximum of maximum damage width is in GaAs [100] crystal direction, and the maximum subsurface damage depth is in GaAs [111] crystal direction. In addition, the stacking height is maximum when GaAs [100] is scraped and minimum when GaAs [110] is scraped. The engraving quality of GaAs materials was investigated utilizing the LAMMPS software through molecular dynamics simulations, while observations were facilitated using the OVITO software. The MD simulation was conducted employing the NPT ensemble, with the temperature fixed at 300 K. A time step of 2 fs was utilized, and the total duration of the MD simulation spanned 600 ps.

Morphological study of cortical bone damage caused by high-pressure water jet erosion based on SPH-FEM coupling algorithm

Currently, traditional processing methods such as drilling, sawing, and milling are primarily utilized in orthopedic surgery, generating a significant amount of heat during the cutting process, leading to irreversible damage to bone and surrounding tissues. High-pressure water jet technology has demonstrated the capability to effectively reduce cutting temperatures and prevent thermal damage during the cutting process. It holds promising potential as an alternative approach to traditional surgical techniques in orthopedic surgery. This study selected the SPH-FEM (Smoothed particle hydrodynamics-Finite element method) coupling algorithm and LS-DYNA software to simulate the effects of high-pressure water jet erosion on cortical bone. The study analyzed the impact of jet pressure on damage morphology and the degree of cortical bone breakage. The simulation results indicate that the concave section of cortical bone damaged by high-pressure water jet is “U” shape. The maximum damage depth of cortical bone increases with the increase in jet pressure. Specifically, as jet pressure increases from 80 MPa to 245 MPa, the increase rate of the average cortical bone damage depth increased from about 0.01 mm/s to more than 0.45 mm/s. The beginning of the concave section of cortical bone damage presents a “funnel” shape, and the width of cortical bone damage reaches its maximum. When the jet pressure is below 180 MPa, there is a significant fluctuation in the width of cortical bone damage. However, with increasing jet pressure, the fluctuation lessens. Physical experiments were carried out under identical technological parameters to verify the numerical results. The experimental results are basically consistent with the numerical results, which can provide a theoretical basis for improving the surface quality of jet erosion of cortical bone.

WITHDRAWN: Investigation on effectiveness calculation and interaction of friction factor of CrN-coated stainless steel: Design of experiment and surface analysis

Hydrogen valves for electric vehicles operate in a high-pressure friction environment and suffer significant wear damage; thus, application of surface treatment technology is necessary. Systematic research is needed to evaluate the effectiveness of friction factors to reduce wear damage in harsh environments of surface-treated specimens. In this investigation, CrN coating using the arc ion plating (AIP) method was applied to stainless steel, and the effectiveness of the factors (load, distance, and rotation speed) of wear damage was tested using the design of experiments method. A validity test was calculated using analysis of variance, and the calculated results were comprehensively compared with the microscopic analysis results. The analysis of variance indicated that the highest factor and lowest factor were the F-value of the load (127.49) and the rotation speed (0.66), respectively. The maximum damage depth and width increased as all friction factor conditions increased. As a result, the calculation of the effective factor of wear damage was similar between the analysis of variance and the microscopic analysis. The CrN coating layer had excellent wear resistance, and the load factor was the most effective.

Microstructural changes in He-irradiated V-Cr-Ti alloys with low Ti addition at 700 °C

V-Cr-Ti alloys with reduced Ti contents are expected to be good candidates as recyclable structural materials for fusion reactors. Herein, He irradiation was applied to V-4Cr-xTi (x = 0 to 4) alloys to investigate the additional effect of Ti and gas interstitial impurities on their microstructural evolution and irradiation hardening. Following He irradiation of the specimens at 700 °C with a maximum damage depth of 0.5 dpa, transmission electron microscopy and nanoindentation hardness tests were conducted. The microstructural evolution of the titanium-oxycarbonitride (Ti(CON)) precipitates formed during He ion irradiation was observed. The behavior of irradiation hardening is explained by the formation process of Ti(CON) precipitates and the magnitude of irradiation hardening depends on the amount of gas interstitial impurities that contribute to precipitate formation.

Ground control by L-shaped cemented paste backfilling technology in underground coal seam mining: a case study

Traditional cemented paste backfilling continues to face the shortcomings such as paste leakage, poor adaptability to geological structures and insufficient roof-contact. To solve the limitations, a novel L-shaped cemented paste backfilling (LCPB) technology was proposed in this study. It is to set L-shaped filling zones and partition zones in the goaf to perform interval and multiple filling. A mechanical model was established to calculate backfilling body strength, widths of L-shaped filling zones and partition zones and backfilled ratio and etc. The results of a case study showed that: (1) The LCPB mining has a high backfilled ratio, without prominent ground pressure. The maximum values of roof-to-floor convergence of the working face and roadway were 58 mm and 259 mm, respectively. It could effectively control the deformation of surrounding rock and achieve roadway retention. (2) When the floor strata were intact, the maximum floor damage depth was less than 4 m, and the floor near the fault was 10–12 m. The secondary lift height of the confined water was about 5 m near the fault. The LCPB mining allows for safety mining above a confined aquifer. (3) The maximum surface inclination and curvature were 1.75 mm/m and 0.06 mm/m2, respectively. The draw angle was 11.3°, and the subsidence factor was 0.085. The ground surface deformation was reduced to be less than that allowed in the first level of the building damage (inclination and curvature of 3 mm/m and 0.2 mm/m2, respectively).

He2+ irradiation response of structural evolution at different depths of MgO-Nd2(Zr1-xCex)2O7 composite ceramics used for inert matrix fuel

This paper reported the irradiation response of a 55 wt.% MgO-45 wt.% Nd2(Zr1-xCex)2O7 (abbreviated to M-NZCx, x = 0, 0.3 and 1) composite ceramics used as candidate inert matrix fuel under 500 keV He2+ ions with fluence of 1 × 1016–5 × 1017 ions/cm2. The irradiation-induced lattice expansion, amorphization of MgO and NZCx phases and order-disorder transition of Nd2(Zr1-xCex)2O7 pyrochlore were systemically explored via GIXRD, Raman and TEM techniques. And the detailed irradiation response at different depths of the typical M-NZC0.3 sample was especially investigated via GIXRD and TEM. The results showed that the lattice expansion ratios (Rs) of MgO (M), ordered pyrochlore (P) and disordered defect-fluorite (F) structures of NZCx pyrochlore in the samples under the same dose of He2+ irradiation were regular, which were ranged as the following order: RsM < RsP < RsF. And there was a belt-shaped damage aggregation zone located near interphase boundary at the maximum damage depth of M-NZC0.3 sample, which could be explained by the defect-absorption of boundary. And this defect-absorption of boundary was also found at any depth of M-NZC0.3 sample. This work systematically analyzed α-decay irradiation response of different phases in M-NZCx composite ceramics applying for inert matrix fuel.

The effect of magnetic field on the electric breakdown trajectory of high‐voltage electric pulse rock breaking

AbstractHigh‐voltage electric pulse drilling technology has the advantages of high rock‐breaking efficiency, low energy consumption for rock breaking, and good quality of well wall, which is a new and efficient potential rock‐breaking method. In this paper, we constructed a numerical simulation model of rock electric breakdown and realized the whole process of rock breaking and plasma channel generation by high‐voltage electric pulse. The results of the study showed that the change of magnetic field has a large influence on the formation of plasma channels inside the rock, and under the self‐magnetic field environment, the plasma channels inside the rock show branching, and the maximum penetration depth and maximum damage depth are higher than those under the non‐magnetic field environment. In the external magnetic field environment, the plasma channels gradually tend to develop “downward” (inside the rock), and the temperature distribution of the plasma channels inside the rock is more concentrated. In the presence of a magnetic field, the speed and degree of freedom of charged particles are limited. In an external magnetic field environment, the charged particles cause fewer particles to deviate, and the particles show a “downward” accumulation phenomenon. The research in this paper can provide certain theoretical and technical guidance for the development of electric pulse rock‐breaking technology and provide reference for the development and parameter optimization of electric pulse rock‐breaking tools.

Analytical modeling of subsurface damage and material removal energy in elliptical vibration cutting of micro-structures on brittle materials

Elliptical vibration cutting (EVC) is a promising technique for the fabrication of micro-structures on brittle materials. In this work, the surface quality and material removal energy in ultra-precision machining of micro-structures on brittle materials by EVC were investigated. Theoretical models were first established for predicting subsurface damage and specific cutting energy (SCE) based on the intermittent material removal characteristics of EVC. The models correlated cutting parameters with the tool vibration trajectory parameters, target surface geometry parameters, and material removal modes. Furthermore, the material removal behaviors in the nominal cutting direction and the feeding direction were comprehensively considered. To verify the model, the experiments of EVC and ordinary cutting (OC) were performed on single crystal silicon, and the surface morphology and cutting force were characterized. The results indicated that, compared with OC, the maximum subsurface damage depth is reduced by 61.82% and the SCE stability value is reduced to 45.87% by applying EVC to fabricate micro-structures. EVC could significantly improve the machining quality and reduce energy consumption. In addition, increasing the vibration amplitude in the depth of cut direction could further save energy, but a larger amplitude would increase subsurface damage. This work not only promotes the recognition of the material removal mechanism of EVC, but also presents effective guidance for achieving high-quality and sustainable machining of micro-structured surfaces.

Ion energy dependence of dry etch damage depth in Ga2O3 Schottky rectifiers

The β-polytype of Ga2O3 has a high critical electric field strength (∼8 MV.cm−1) and can be grown as large diameter (6 in.) single crystal boules by inexpensive melt-growth techniques. This makes it promising for next generation power electronics and solar-blind UV photodetectors. Since wet etching is not feasible for patterning such devices due to the chemical inertness of Ga2O3, attention is focused on dry etching, with the attendant issue of surface modification due to chemical or ion-induced changes. In this work, we demonstrate that dry etch damage in β-Ga2O3 is manifested by a reduction in near-surface carrier concentration, possibly due to the introduction of Gav acceptor states. The depth to which the carrier density is affected depends on the interplay between ion energy and etch rate, with faster etch rates reducing the depth of the remaining damaged region. The maximum damage depth observed experimentally from capacitance-voltage profiling on Schottky rectifiers was ∼ 110 nm, well beyond the range of the ions in the Inductively Coupled Plasmas and emphasizing that rapid diffusion of point defects occurs into the sample during the etch step. Using Schottky rectifier structures as a platform to understand the effect of dry etch damage on device parameters, we found that on-state resistance was more affected than ideality factor or breakdown voltage, with a large increase (5x) for ion energies ≥ 325 eV. Reverse current density characteristics showed the presence of trap-assisted space-charge-limited conduction in the damaged layers. The implications for high power rectifier fabrication are discussed.

Effects of temperature on the deformation of 6H–SiC during nanoscratching

With the aid of large-scale molecular dynamics simulations, this paper comprehensively investigated the effects of processing temperature on the deformation of single crystal 6H–SiC during nanoscratching. The effect was investigated across a wide range of temperature variations, from 1 K to 900 K. It was found that with increasing the processing temperature, the material removal mechanism of 6H–SiC experience a transition from intermittent cleavage to continuous plastic deformation. The deformation mechanism of 6H–SiC is achieved by the combination of surface amorphization and subsurface dislocations that reside mainly in the cubic diamond structural layer. The processing temperature significantly affects the dislocation distribution, groove morphology, scratching forces and coefficient of friction. The anisotropic effect on chip formation decreases with increasing the processing temperature. By evaluating surface roughness and the maximum subsurface damage depth, the investigation concludes that the scratched surface/subsurface quality of 6H–SiC deteriorates with increasing processing temperature.

Numerical study on spatial distribution of blast-induced damage zone in open-pit slope

The excavation damage zone in rock slopes after drill-and-blast operations is of great significance for assessing the slope stability and design of open pit mines. The traditional method simplifies, the spatial distribution of the damage zone in a slope following blasting is as a single radius distributed, which leads to an inaccurate evaluation of slope stability. Herein, a model coupling the tensile damage and the Drucker-Prager yield criteria is established to investigate the spatial distribution characteristics of blast-induced damage zone in the final wall of an open-pit. Explosive explosion is converted to an equivalent pressure time history acting on the blasthole wall and the extension of the damage observed in the field test is reproduced successfully by numerical simulation. The proposed model is verified on the basis of the site-monitored data from the Wushan Copper mine, a large-scale open-pit mine in Inner Mongolia, China. The results show that the damage decreases with increasing depth, exhibiting a nonlinear distribution behind the slope face. The maximum depth and scopes of horizontal and vertical damage occur at the slope crest. The proposed model is compared with five widely used damage models and proves to be more capable of representing the spatial distribution of the damage zone observed in the site test. Finally, the formation mechanism of the maximum damage depth along the crest is also revealed.

Electrochemical Properties of Super Austenite Stainless Steel with Temperature in a Green Death Solution

In this investigation, potentiodynamic polarization experiments were conducted on UNS S31603 and UNS N08367 in a modified green death solution, which simulates the environment of a desulfurization device (scrubber), using temperature as a variable. A Tafel analysis showed that the corrosion current density of UNS S31603 at the highest temperature (90 °C) was approximately 4.5 times higher than that of UNS N83067. A surface analysis using a scanning electron microscope revealed that pitting and intergranular corrosion occurred simultaneously in UNS S31603, whereas UNS N83067 exhibited a stronger tendency toward intergranular corrosion. After electrochemical experiments, the corrosion rates according to maximum damage depth were compared with the corrosion rates according to corrosion current density; the relationships between the two values were expressed as α values. The α values of UNS N08367 were higher than those of UNS S31603, indicating that the local damage rate of UNS N08367 was higher.

Electrochemical Characteristics with NaCl Concentrations on Stainless Steels of Metallic Bipolar Plates for PEMFCs

Stainless steel, which is used in metallic bipolar plates, is generally known to have excellent corrosion resistance, which is achieved by forming oxide films. However, localized corrosion occurs when the oxide films are destroyed by pH and chloride ions. Particularly, since the operating condition of polymer electrolyte membrane fuel cells (PEMFCs) is strongly acidic, the reduced stability of the oxide films leads to the corrosion of the stainless steel. In this research, the electrochemical characteristics of 304L and 316L stainless steels were investigated in an accelerating solution that simulated the cathode condition of PEMFCs with chloride concentrations. Results under all experimental conditions showed that the corrosion current density of 304L stainless steel was at least four times higher than that of 316L stainless steel. Maximum damage depth was measured at 6.136 μm and 9.192 μm for 304L stainless steel and 3.403 μm and 5.631 μm for 316L stainless steel for chloride concentrations of 0 and 1000 ppm, respectively. Furthermore, 304L and 316L stainless steels were found to have uniform and localized corrosion, respectively. The differences in the electrochemical characteristics of 304L and 316L stainless steel are considered to be due to the molybdenum contained in the chemical composition of 316L stainless steel.

Study on Excavation Damage Characteristics of Surrounding Rock in Deeply Buried Tunnels by Particle Flow Code Simulation

This study is aimed at investigating the excavation damage characteristics of surrounding rock in Jinping deeply buried marble tunnels, China. According to the acoustic detection results of tunnel cross-sections under the condition of tunnel boring machine (TBM) obtained on site, the PFC microscopic parameters of Types II/III tunnel marble were simulated and calibrated through the PFC2D program. In doing so, the excavation damage characteristics of surrounding rock of deeply-buried sections in Jinping diversion tunnels were simulated. The results reveal that the excavation damage zones (EDZ) of surrounding rock of Types II/III marble sections in Jinping tunnels are unevenly distributed around the tunnels; the largest zone is located from the top arch to the north arch shoulder. The EDZ depth and damage degree of surrounding rock rise with the increase in buried depth, and they also increase with the decrease in rock quality. Generally, the maximum damage depth of Type III surrounding rock is about 1.0 m larger than that of Type II surrounding rock under the same buried depth, which is basically consistent with the detection results of the relaxation depth of surrounding rock. The simulation well discloses the excavation damage characteristics of surrounding rock in Jinping deeply buried tunnels.

Effect of the notched foreign object damage depth on the HCF strength of titanium alloy TC11

In this study, the effects of different incident foreign object damage (FOD) depths on the high-cycle fatigue (HCF) performance of TC11 titanium alloy specimens with compressor leading edge blades were studied. FOD values were obtained through high-speed ballistic impact tests at different aiming positions under the same impact conditions. HCF tests of smooth and FODed specimens were conducted via the step-loading test method, and the HCF strength was determined via experiments and numerical analysis. The results indicated that with increasing damage depth, the stress concentration factor significantly increased. There occurred greater material losses on the exit side of the resultant notch damage than those on the incident side. The maximum damage depth ranged from 0.23 to 1.51 mm, and the fatigue strength of the FODed specimens reached approximately 21.77–84.99 % of that of the smooth specimens. With increasing depth, the material loss increased, and the fatigue strength decreased. According to the Kf = 3 empirical criterion for FOD tolerance design, the determined serviceable limit of notch-type damage was 0.84 mm, which is expected to be useful for quick assessment of the notch-type FOD degree of TC11 titanium alloy leading edge blades.

Comprehensive Monitoring Research on the Effect of Roof Cutting and Pressure Release: A Case Study of the Jiulishan Coal Mine in China

The longwall panel of the Jiulishan coal mine is affected by floor-confined water, while the roof rock weighting makes the production management of some longwall panels difficult. This has caused engineering methods of roof cutting and pressure release to be considered. To explore the dynamic effects of roof cutting and pressure release method, the 14141 longwall panel was taken as the test point, and a variety of monitoring methods were used to comprehensively analyze the characteristics of roof rock weighting, front abutment pressure, and floor mining failure. The main results are as follows: first, the weighting interval, the weighting intensity distribution, and the gateway deformation are asymmetrical. Second, the peak point of the front abutment pressure is approximately 6 m away from the coal wall, the peak stress is 7.02 MPa, the concentration coefficient is 1.54, the range of the pressure increasing area is approximately 16.4 m, and the farthest end of the front abutment pressure effect area is 22.4 m away from the coal wall. Furthermore, the maximum depth of the floor failure is at the No.17 measuring point (A117) position under the condition of one electrode distance. The maximum damage depth is 9.8 m, and the horizontal distance between the location of the maximum failure depth and the working face is 4.1~10.3 m. Finally, compared with the formula calculation value without considering the effect of roof cutting and pressure release or the adjacent 14121 longwall panel, the weighting interval and the weighting intensity, the gateway deformation, the degree of coal wall spalling, the influence range of the front abutment pressure, and the degree of floor mining failure are significantly reduced. The research results provide scientific and technological support for roof cutting and pressure release as a technical method to prevent floor water inrush and reduce the roof rock weighting intensity on the longwall panel.

Dual conductive network of nickel‐coated carbon fiber woven fabric for indirect and direct lightning strike protection of carbon fiber reinforced polymer composites

AbstractIn this study, a dual conductive network of nickel‐coated carbon fiber woven fabrics (Ni‐CFWF) was presented for indirect and direct lightning strike protection (LSP) of carbon fiber reinforced polymer (CFRP) composites. The Ni‐CFWF prepared by electroless plating was bonded to the top surface of a CFRP composite. Excellent electromagnetic interference shielding effectiveness of Ni‐CFWF/CFRP composite was achieved with a value of 92.87 dB in the frequency range 8.2–12.4 GHz, 189.22% greater than that of the pristine CFRP composite. Moreover, the prepared Ni‐CFWF also exhibited a good direct lightning strike (LS) protection performance. The maximum LS damage depth and area of the Ni‐CFWF/CFRP composites were reduced by 21.59% and 6.11% under a simulated lightning current with the peak of 100 kA, respectively. Correspondingly, the residual strength of the Ni‐CFWF/CFRP composites was maintained at 92.65% after LS, demonstrated the LSP effectiveness. Our work provides an effective strategy for the design of a protective system that considers both indirect and direct LSP.

The Coal Pillar Width Effect of Principal Stress Deflection and Plastic Zone Form of Surrounding Rock Roadway in Deep Excavation

In order to explore the influence of coal pillar width on the principal stress deflection and plastic zone form of surrounding rock in deep roadway excavation, taking 11030 working face transportation roadway of Zhaogu No. 2 Coal Mine as engineering background, theoretical analysis, numerical simulation, and field detection were used to study the effect of coal pillar width on principal stress deflection and plastic zone form and field detection and verification of plastic zone form of surrounding rock in 11030 transportation roadway. The results show that the maximum principal stress is deflected in the vertical direction, which in roadway surrounding rock excavation. The coal pillar width effect of principal stress deflection on both sides of roadway roof and floor and inside coal pillar are more obvious than that of middle roof and floor, coal pillar edge and coal wall position. The deflection of the principal stress affects the morphological distribution of the plastic zone of the surrounding rock, which led to the width effect of coal pillar in roof, and two sides plastic zone are more obvious than that in floor. The principal stress deflection of roadway surrounding rock is highly consistent with the maximum damage depth of plastic zone, and at the same time, the drilling peep results of surrounding rock are basically consistent with the form characteristics of plastic zone in numerical simulation. On this basis, the surrounding rock reinforcement support scheme of 11030 working face transportation roadway was proposed.