Thickness Of Zone Research Articles

Intelligent Analysis and Optimization of Lubrication Status Factor Based on Dynamically Loaded Roll Gap in Cold Strip Rolling

Lubrication is a critical process in cold strip rolling, and the accurate characterization of lubrication characteristics is an essential factor affecting the strip quality. The roll bending and tilting roll in the flatness actuators change the loaded roll gap profile and affect the lubrication characteristics by flatness dynamic correction, thus the mismatch between the actual and setting values of the lubrication status factor. Firstly, the flatness deviation correction model of roll bending and tilting roll based on the key information of the rolling process is established according to the high-order flatness target. Secondly, the characterization of the instantaneous oil film thickness in the work zone based on the loaded roll gap profile is derived from Reynolds’ equation. Finally, the explicit characterization method of the lubrication status factor in the rolling force model of the final stand is established with the work roll bending, tilting roll, and instantaneous oil film thickness of the work zone as variables, relying on the UCM five-stand, six-roll tandem cold rolling mill. The statistical evaluation and application results show that the mentioned optimization method can improve the setting accuracy of the rolling force by about 60% and the after-rolling gauge accuracy by about 50%.

Experimental Study on Efficient Short Electric Arc Turning of Titanium Alloy

This study investigates a novel short electric arc vertical turning method for machining titanium alloy shafts. The method was successfully applied to titanium alloy rods, and its effects on material removal rate (MRR), surface roughness, roundness, and cross-sectional morphology were analyzed at varying processing voltages. The results indicate that the MRR and surface quality improve with increased voltage, reaching a maximum of 231 mm3/min and 26 μm surface roughness at 32 V. However, surface roughness deteriorates with higher duty cycles and voltages due to unstable discharges. Roundness deviations are minimized with higher rotational speeds, which enhance uniform material removal and arc stability. Metallographic analysis revealed an increased heat-affected zone and recast layer thickness at higher voltages. This method demonstrates high machining efficiency and improved surface quality, making it suitable for titanium alloy shaft manufacturing in advanced engineering applications.

Adult Neurogenesis in the Subventricular Zone of Patients with Huntington's and Parkinson's Diseases and following Long-Term Treatment with Deep Brain Stimulation.

Parkinson's and Huntington's diseases are characterized by progressive neuronal loss. Previous studies using human postmortem tissues have shown the impact of neurodegenerative disorders on adult neurogenesis. The extent to which adult neural stem cells are activated in the subventricular zone and whether therapeutic treatments such as deep brain stimulation promote adult neurogenesis remains unclear. The goal of the present study is to assess adult neural stem cells activation and neurogenesis in the subventricular zone of patients with Huntington's and Parkinson's diseases who were treated or not by deep brain stimulation. Postmortem brain samples from Huntington's and Parkinson's disease patients who had received or not long-term deep brain stimulation of the subthalamic nucleus were used. Our results indicate a significant increase in the thickness of the subventricular zone and in the density of proliferating cells and activated stem cells in the brain of Huntington's disease subjects and Parkinson's disease patients treated with deep brain stimulation. We also observed an increase in the density of immature neurons in the brain of these patients. Overall, our data indicate that long-term deep brain stimulation of the subthalamic nucleus promotes cell proliferation and neurogenesis in the subventricular zone that are reduced in Parkinson's disease. Taken together, our results also provide a detailed characterization of the cellular composition of the adult human subventricular zone and caudate nucleus in normal condition and in Parkinson's and Huntington's diseases and demonstrate the plasticity of these regions in response to neurodegeneration. ANN NEUROL 2025.

Fluid flow in crustal fault zones with varying lengthwise thickness: application to the Margeride fault zone (French Massif Central)

Crustal fault zones, holding promise as potential geothermal reservoirs, remain largely untapped and unexplored. Located in the southern Massif Central, France, the Margeride fault zone (MFZ) varies in thickness (lateral extension perpendicular to the fault plane) from 100 m to over 2500 m. Reactivated several times under different stress regimes since the Variscan orogeny, this zone is characterized by an intense alteration and fracturing. As a result, the multiple reactivation of the fault zone has maintained permeability, leading to favourable conditions for fluid circulation. Structural measurements and geological cross sections were used to precisely constrain thickness and geometry of the fault zone. North of the MFZ, the Coren thermal spring indicates reservoir temperatures of about 200–250 °C, hinting at the possible existence of a temperature anomaly. To investigate this geothermal potential, 3D numerical models simulating fluid circulation within a fault zone were conducted. Various configurations were explored, altering fault zone thickness and permeability for two key geometries. The first geometry, which manipulated the width of the fault zone along its length, demonstrated a direct correlation between fault zone thickness and amplitude of thermal anomaly. Thinner faults (< 500 m) exhibited multiple weak positive thermal anomalies, while thicker faults (> 500 m) tended to develop a single, substantial positive thermal anomaly. In the second examined geometry, where fault zone thickness increased longitudinally, a consistent positive temperature anomaly emerged at the thickest section of the fault zone. Depending on the permeability value, an additional anomaly may develop but will migrate laterally towards the thinnest part of the fault zone. This multi-disciplinary approach, combining numerical modelling and field measurements, presents a predictive methodology applicable to geothermal exploration in analogous basement domains. In our case, it has shown that the northern end of the Margeride fault zone could represent an area that needs to be explored further to assert its high geothermal potential. Our numerical models will increase understanding of how fault width and geometry impact the geothermal potential of the Margeride fault zone and similar areas in crystalline basement.

Insights into the effects of subretinal voretigene neparvovec-rzyl in RPE65-associated Leber congenital amaurosis: an 18-Month report.

Assess safety and effectiveness of subretinal gene replacement therapy at 18 months post treatment. Retrospective, longitudinal study conducted at the Hospital for Sick Children in Toronto, Canada. Patients with bi-allelic RPE65 variants, early onset retinal degeneration, and residual viable retina who underwent voretigene neparvovec r-zyl gene replacement therapy. Data collected included demographic information, molecular genetic results, and comprehensive ocular assessment results from preoperataive and postoperative visits up to 18 months. To assess the treatment's efficacy, postoperative best corrected visual acuity, full-field stimulus test (FST), visual field (VF) area, optical coherence tomography, and global satisfaction were compared to preoperative findings. The procedures were safe with no complications. There was no significant improvement in visual acuity. Three eyes showed a slight reduction in VF area. All showed a reduction in ellipsoid zone thickness and area, but the outer nuclear layer thickness and area were stable. All had a significant improvement in retinal sensitivity, as per FST, allowing better navigation in a dim environment. All 3 patients reported being "very satisfied". Following a safe gene replacement therapy, the 3 first Canadian cases had an improvement in retinal sensitivity as per FST, and our patients described their experience as positively life changing.

Interactions between megathrust behavior and forearc deformation in the Andreanof segment of the Aleutian Subduction Zone, offshore Alaska, USA

To explore controls on megathrust behavior and its connection with forearc deformation, we studied the Andreanof segment of the Aleutian Subduction Zone (offshore Alaska, USA), which has a simple geological history as a relatively young intra-oceanic subduction zone. Here, the forearc shows greater uplift and compression in the strongly coupled Adak region compared to the weakly coupled Atka region. Using multichannel seismic reflection data, we found that the incoming plate in both regions exhibits similar characteristics along the segment, suggesting that its properties do not account for the varying megathrust behavior and forearc deformation. Instead, differences between the Atka and Adak regions in the thickness of the methane hydrate stability zone, as marked by a bottom-simulating reflector, suggest more heat advection, and thus dewatering, in the Adak region, where the more developed fault network may enable fluid drainage, thereby lowering pore pressure at the megathrust and promoting coupling. Higher coupling allows for seismic and stress cycling that would sustain forearc permeability by faulting. Our results suggest a feedback between deformation and coupling that may be active or latent in other more complex subduction zones but in concert with or masked by other factors.

Root-soil interface friction jointly amplified by high root density and shear deflection

Plant roots significantly enhance the stability of shallow slopes. However, the mechanism of the root-soil interaction at root-bundle scale remains unclear. The objective of this study is to reveal the factors that control root-soil interface frictional stress at root-bundle scale. Through theoretical analysis, it is clarified that spatiotemporal inhomogeneity exists in root-soil interface frictional stress, and it could be amplified by root density and root deflection angle. Large-scale shear tests with 160 mm and 10 mm shear zones were then conducted to verify this hypothesis, where variations in shear zone thicknesses corresponded to different shear deflections. The number of roots was measured within the sheared zone. Results reveal that the average root-soil interface frictional stress of rooted soils with 10 mm shear zone is 66% higher than that for rooted soils with 160 mm shear zone. During the shear process, the state of roots transitions from stretching to sliding, accompanied by increasing root-soil interface friction. This study confirms that root-soil interface frictional stress is jointly amplified by root density and root deflection angle, providing robust evidence for constructing physics-based mechanical reinforcement models.

Global Sensitivity Analysis of Slope Stability Considering Effective Rainfall with Analytical Solutions

Abstract: Rainfall-induced landslides are widely distributed in many countries. Rainfall impacts the hydraulic dynamics of groundwater and, therefore, slope stability. We derive an analytical solution of slope stability considering effective rainfall based on the Richards equation. We define effective rainfall as the total volume of rainfall stored within a given range of the unsaturated zone during rainfall events. The slope stability at the depth of interest is provided as a function of effective rainfall. The validity of analytical solutions of system states related to effective rainfall, for infinite slopes of a granite residual soil, is verified by comparing them with the corresponding numerical solutions. Additionally, three approaches to global sensitivity analysis are used to compute the sensitivity of the slope stability to a variety of factors of interest. These factors are the reciprocal of the air-entry value of the soil α, the thickness of the unsaturated zone L, the cohesion of soil c, the internal friction angle ϕ related to the effective normal stress, the slope angle β, the unit weights of soil particles γs, and the saturated hydraulic conductivity Ks. The results show the following: (1) The analytical solutions are accurate in terms of the relative differences between the analytical and the numerical solutions, which are within 5.00% when considering the latter as references. (2) The temporal evolutions of the shear strength of soil can be sequentially characterized as four periods: (i) strength improvement due to the increasing weight of soil caused by rainfall infiltration, (ii) strength reduction controlled by the increasing pore water pressure, (iii) strength reduction due to the effect of hydrostatic pressure in the transient saturation zone, and (iv) stable strength when all the soil is saturated. (3) The large α corresponds to high effective rainfall. (4) The factors ranked in descending order of sensitivity are as follows: α &gt; L &gt; c &gt; β &gt; γs &gt; Ks &gt; ϕ.

Pathogenesis of fibrosis in patella-patellar tendon junction induced by jumping load in a rabbit model.

The mechanism of fibrosis at the patella-patellar tendon junction (PPTJ) was investigated using a rabbit overuse jumping model. Thirty-two female New Zealand White rabbits were randomly divided into control and jumping groups, and each group was further divided into four groups at 2, 4, 6, and 8 wk. The rabbit in the jumping group jumped 150 times/day, 5 days/wk. The PPTJ was removed at the corresponding time point and subjected to hematoxylin and eosin, safranin O, and immunohistochemical staining. Significant differences were observed in histological changes and fibrosis-related factors between the jumping and control groups (P < 0.01). Comparison within the jumping group indicated that the changes in the fibrocartilage zone thickness and proteoglycan area were pronounced at week 6; the expressions of transforming growth factor β (TGF-β1), Smad3, CTGF, α-SMA, COL-I, and COL-III peaked at week 6 (P < 0.05). The jumping load can lead to morphological and fibrotic changes in the patella-patellar tendon junction, with peak changes occurring at week 6. The fibrosis in the patella-patellar tendon junction may be associated with increased secretion of TGF-β1 and Smad3 due to jump loading, which upregulates CTGF expression and thus promotes the synthesis of α-SMA, COL-I, and COL-III.NEW & NOTEWORTHY The temporal pattern of fibrosis in the patella-patellar tendon junction (PPTJ) was determined by observing changes in histology and fibrosis-related factors at different time points in an overused jumping rabbit model. The results revealed that 1) the peak fibrotic changes in the PPTJ occurred at week 6 of jump training; 2) fibrosis in PPTJ may be associated with the changes in TGF-β1/Smad3. This study contributes to the development of targeted early interventions.

Tribological Behavior of Gas-Nitrided 42CrMo4 Steel at Elevated Temperatures

Nitriding is a well-known thermochemical treatment improving the surface hardness and the wear resistance of steel. The phase composition and growth kinetics of the nitrided layer can be controlled using a gas nitriding with changeable nitriding potential. In this work, such a gas nitriding was used to produce, on 42CrMo4 steel, the two nitrided layers differing in the thickness of compound zone and diffusion zone. The microstructure and nanohardness of these layers were studied. For the first time, the tribological behavior of gas nitrided layers at elevated temperatures (from 23 to 400 °C) was investigated. The compound zone consisted of ε + (ε + γ’) iron nitrides and, in the diffusion zone, the nitric sorbite with γ’ precipitates was observed. The highest nanohardness was measured in the ε + γ’ zone. The lowest values of friction coefficients were obtained if the contact surface of the friction pair entered the ε + γ’ zone. After the wear process, at a final temperature of 400 °C, worn surfaces showed only intensive abrasive wear, evidenced by shallow grooves. The increased oxygen content at the edges of wear tracks indicated possible oxidative wear.

Risk and Pollutant Protective Concentration Levels of Drilling Waste Used to Pave Oil and Gas Field Well Sites

Paving oil and gas field well sites of drilling waste allow us to reuse solid waste. However, to keep the risk within acceptable limits, some questions need to be answered: what is the dilution effect that soil and groundwater have on the transport of pollutants? What is the minimum concentration of pollutants leached from drill wastes? In this study, we focus on the paving of well sites using drilling wastes, and we analyze the pollutant migration pattern in the soil vadose zone and groundwater mixing zone after rainwater leaching. The drilling waste pollutant protective concentration level (PCL) and the corresponding dilution attenuation factor (DAF) were then proposed. In addition, the PCL’s accessibility, uncertainty, and environmental significance were further analyzed. It was found that the pollutant dilution factor (DF) of the groundwater mixed zone was strongly influenced by the thickness of the mixed zone, the groundwater Darcy rate, the length of the contaminant source, and the permeability, and each contributed approximately 25%. The soil vadose zone attenuation factor (AF) was primarily influenced by the soil vadose zone (i.e., groundwater depth) thickness that contributed approximately 53%. The contaminant DAF values of the well site drilling waste paving (e.g., the soil vadose zone thickness ranged from 5 to 30 m) ranged from 12 to 84. Additionally, the PCL values of the contaminants ranged from 12 to 84 times of the acceptable concentration (e.g., the Class III permissible limits of the Groundwater Quality Standards GB/T 14848-2017) at the groundwater compliance point. The expression for the exponential relationship between the DAF or PLC and the depth of the soil vadose zone was also provided in this study. The study results provide a reference for the actual process of the use of drilling wastes to pave well sites and for solid waste treatment or soil remediation decision-making and the associated risk assessment procedures.

Effect of Treatment with Progestins and Antiplatelet Agents on IVF in Women with Adenomyosis and Recurrent Implantation Failure.

Background: This prospective study aims to identify the effect of the dienogest 2 mg/day and aspirin 150 mg/day combined treatment for two months before frozen ET on the assisted reproduction outcome in women with adenomyosis and recurrent implantation failure (RIF). Methods: Patients were selected based on specific criteria and divided into two groups (with and without treatment). Preimplantation biochemical parameters and ultrasonographic features (endometrial thickness, uterine peristalsis, and junctional zone thickness) were compared with pregnancy rate in a non-natural cycle frozen embryo transfer technique. A comparison between the two study groups indicated an increased successful implantation rate and clinical pregnancy rate (25% vs. 7.4%). Results: These results were attributed to the reduced uterine peristalsis and the reduction in thickness of the junctional zone following treatment. Available data were limited due to the nature of the study though maximal effort was exerted for the selected patients between groups to be as demographically similar and free from other potential pathology that may affect the results. Conclusions: In conclusion, it appears that the above stated treatment improves outcomes in women with adenomyosis and RIF; the parameters used may provide an insight as to the reasons why this occurs, though an explanation of the molecular mechanisms is still elusive.

Comparing Recovery Volumes of Steady and Unsteady Injections into an Aquifer Storage and Recovery Well

Aquifer Storage and Recovery (ASR) can involve injecting available surface water into an unconfined aquifer and then extracting it to provide secondary water for irrigation. This study demonstrates a method for evaluating the appropriateness of steady injection versus unsteady injection for an assumed situation. In design, it can be important to affect the transient: the proportion of the injected water that would be subsequently extracted (versus that remaining in the aquifer) and the proportion within the extracted water that would be an injectate (versus ambient groundwater). These proportions can be predicted from the predicted value of an ASR well’s Recovery Effectiveness (REN)—the time-varying proportion of injectate that is extracted subsequently from the same fully penetrating well. Applying the demonstrated procedure with appropriately detailed data and simulation models can predict the REN values resulting from steady versus unsteady injection, followed by steady extraction. For convenience in displaying and computing REN, the injectate was assumed to have a 100 ppm conservative solute concentration. For this demonstration, a homogenous isotropic unconfined one-layer aquifer was assumed. The scenarios involved steady or unsteady injection for 61 days via a fully penetrating ASR well. Then, 91 days of steady pumping led to the extraction of a total volume equal to that injected. For the assumed hydrogeologic data—31 years of Salt Lake City, Utah, rainfall data and estimated captured runoff—the results show that steady injection is more likely to cause a predictable REN but might not cause a higher REN than daily varying injection of the same total volume. Assuming different runoff or hydrogeologic flows would lead to different REN values. Steady injection causes a predictable groundwater mound and can assure a sufficient vadose zone thickness for overlying plants. Augmentation and storage of captured rainwater can help to provide a steady injection rate. For a situation that requires REN management, appropriate simulations can help water managers design ASR systems that will achieve REN goals and increase sustainable groundwater availability.

Significant changes of area, length and terminus of Sikkim Himalayan glaciers within the Kanchenjunga national park from 1990 - 2022

In this study, we have investigated four glaciers, namely Zemu, Talung, Alukthang and Rathong within Kanchenjunga national park. This study evaluates physical and morphometric parameters (area, length, perimeter, area of accumulation zone, ablation zone length, snout position, thickness and specific mass balance) of multiple glaciers and to ascertain the poorly understood glaciers of western Sikkim region under Kanchenjunga national park. The principal objective of this research is to find out the changes of glacial mass and other physical parameters of the selected glaciers using multi sources digital elevation model data.Various techniques of statistics, including Mann-Kendall and Sen’s slope tests have been applied at different confidence interval. We have identified that climate change is responsible for the alterations of the physical characteristics of the glaciers. Result shows that during the study period, Zemu glacier has faced highest amount of deglaciation in terms of area (20.79 sq.km) along with maximum 30 meter elevation reduction, 24m increase of snout elevation and 200m retreat of terminus. Furthermore, it is observed that terminus of the each selected glaciers retreated during the study period. Rathong experienced maximum retreat rate, approximately 550m, and it is accompanied by a notable 163% increase in the ablation zone. Alukthang and Talung reduced their areas 0.56 and 4.06 sq.km respectively, along with 2.75m and 9.10m thickness respectively. Maximum 36.39m/y-1 flow rate has been observed over Zemu glacier. The flow rate of Talung, Rathong and Alukthang glacier is 26.4m/y-1, 34.1m/y-1, and 23.7m/y-1 respectively.

Diminished retinal microcirculation in mild preeclampsia without obvious retinopathy in high-altitude native Tibetans by OCTA

BackgroundTo investigate the retinal microcirculation in mild preeclampsia (PE) without obvious retinopathy in high-altitude native Tibetans by optical coherence tomography angiography (OCTA). MethodsThis study enrolled 64 mild preeclamptic pregnant women without retinopathy (group PPW), 63 healthy pregnant women (group HPW), and 61 healthy non-pregnant women (group HNPW). All participants were high-altitude native Tibetans who underwent OCTA, retinal thickness (RT), vascular density (VD), perfusion density (PD) and foveal avascular zone (FAZ) parameters were measured in the macula. Differences in these parameters among the groups were compared, and the correlations of these parameters with blood pressure were evaluated. ResultsIn the entire macula, VD and PD were significantly lower in group PPW than in group HPW and HNPW (p < 0.05). In the subregions, VD was significantly different in fovea, parafovea and perifovea, PD was significantly different in parafovea and perifovea among the three groups (p < 0.05), the further pairwise comparisons showed VD and PD in parafovea and perifovea were lower in group PPW than in group HPW, and VD and PD in perifovea were lower in group PPW than in group HNPW (p < 0.05). RT and FAZ parameters did not differ among the groups (P > 0.05). VD and PD exhibited negative correlations with SBP and DBP (p < 0.05). ConclusionOCTA can objectively evaluate diminished microcirculation in mild PE without obvious retinopathy among high-altitude native Tibetans, and provide a crucial time window for early screening of PE-induced retinopathy.

Magmatic activity in incipient continental break-up as revealed by coupling melt and fluid inclusions

Abstract Deciphering deep magmatic processes driving the onset of continental break-up is fundamental to constrain our understanding of plate tectonics. The East African Rift System (EARS) is the only currently active system on Earth to study distinct stages of rift evolution. We present a coupled analysis of melt and fluid inclusions in the Virunga Volcanic Province (VVP) offering an unprecedented insight into the dynamics of incipient rifting and its evolution. Our study highlights that melting of distinct metasomes in the deep lithosphere is a common feature of immature rifts. In the VVP, it leads to the emission of nephelinitic and basanitic melts at Nyiragongo and Nyamulagira volcanoes, respectively. Additionally, the chemical composition of melt and fluid inclusions supports the identification of another magmatic series in the area. Related alkali basaltic melts would be produced by contemporary melting of a less enriched domain in the upper lithosphere, more classically documented in mature rifts. Various extents of mixing and crystallisation of these three distinct magmatic series occur in the lower crust beneath the VVP where the barometric estimates are consistent with the presence of a thick seismic low velocity zone (LVZ). The involvement of alkali basaltic melts in the regional magma production could be also detected in the spread of gas emissions in the rift valley and in the fumaroles of the main active volcanoes. Melting of the corresponding mantle domain is an added source of gas release that may largely contribute to CO2 emissions along the EARS.

Advanced Scanning Technology for Volume Change Measurement of Residual Soil

Weathering processes of rocks lead to the formation of residual soil layers, which are typically characterized by a deep groundwater table and a thick unsaturated zone. Hence, the calculation of a slope’s safety factor under the influences of climatic circumstances is a function of unsaturated characteristics, such as the soil–water characteristic curve (SWCC). To determine the SWCC, the volume of the soil specimen must be determined in order to compute the void ratio and degree of saturation. The drying processes of the soil specimen led to uneven soil volume change during laboratory SWCC testing, demanding the development of a soil shrinkage curve. Several methods for measuring soil volume change have been developed over the years. However, there are significant limitations, and it is rarely used due to the difficulty linked to accurately measuring the soil volume during drying processes. In this study, a revised scanning approach is developed to evaluate residual soil volume change utilizing 3D scanning technology. The proposed method is applied in a case study on residual soil from the Old Alluvium in Singapore. The laboratory data and analysis results suggested that 3D scanning technology should be required to provide a correct estimation of the air-entry value of soil.

Anatomy of a deep Piedmont critical zone: Evaluating hypotheses on regolith depth controls through comparison of ridge and valley boreholes

AbstractControls on the physical and chemical architecture of the subsurface critical zone are somewhat controversial, with multiple hypotheses proposed to account for variations in the depth of weathering between sites, and with landscape position at a site. In the Piedmont region of the Mid‐Atlantic US weathering of crystalline bedrock has been observed to extend tens of meters below the surface and groundwater in a'bow‐tie’ shape – i.e. weathering extends to lower elevations below ridges than below channels. The chemical and physical structure of a hillslope transect in the Maryland Piedmont was explored with a 45 m borehole in the ridge, as well as shallow bedrock boreholes at the toe of the slope and valley. Chemical weathering fronts were characterized using elemental abundances and mineralogical analysis. The ridge borehole did not extend deeper than the chemically and physically weathered rock. Surface and borehole geophysics and density measurements were used to characterize the weathered rock and saprolite. Na and Ca results suggest that plagioclase feldspar weathering is similar between samples collected from 45 m under the ridge and 2.2 m under the valley bottom. A narrow Fe oxidation garnet weathering front co‐insides with the transition from weathered bedrock to saprolite, suggesting that this reaction may generate initial saprolite porosity. Muscovite weathering co‐occurs with complete depletion of plagioclase a few meters above the Fe oxidation front. These nested weathering fronts in the saprolite appear to follow a subdued version of the surface topography. The location and shape of the nested saprolite weathering fronts may be controlled by the feedback between the transport of reactants and solutes and reaction‐generated porosity, consistent with the conceptual “valve” hypothesis. Differing dominant control mechanisms on deep bedrock weathering and saprolite initiating reactions may explain the thickness and structure of the critical zone at our site.

Sequential irradiation does not improve fatigue crack propagation resistance of human cortical bone at 15 kGy

Sequential irradiation has been advocated for mitigating the reduction in fatigue properties of tendon compared to a single dose. However, to our knowledge, its capability of mitigating fatigue losses in bone is unknown. Recently, we reported that sequential irradiation did not mitigate losses in high-cycle S-N fatigue life of cortical bone at 15 kGy; however, it is unclear if sequential irradiation provides a benefit to fatigue crack propagation resistance. Our previous study also showed that radiation-induced collagen chain fragmentation and crosslinking increased from 0 to 15 kGy, suggesting that both likely contribute to the reduction in high-cycle S-N fatigue life within this dose range. Our objectives were: 1) to evaluate the fatigue crack propagation resistance of cortical bone and the effect of radiation on fracture plane damage zone thickness (DZT) at the crack tip in the dose range of 0–15 kGy, and 2) to evaluate whether sequential irradiation at 15 kGy mitigates the loss of fatigue crack propagation resistance of cortical bone compared to a single irradiation dose. Compact tension specimens from four male donor femoral pairs (ages 21–61 years old) were divided into 5 treatment groups (0 kGy, 5 kGy, 10 kGy, 15 kGy, and a 15 kGy sequential irradiation dose of 5 kGy sequentially irradiated with 10 kGy) and subjected to fatigue crack propagation testing (n = 3–4 specimens per group) where fatigue crack growth rate da/dN and cyclic stress intensity factor ΔK were determined. Following testing, specimens were bulk stained in basic fuchsin, embedded in poly(methylmethacrylate), sectioned, and mounted on acrylic slides to evaluate fracture plane DZT at known crack lengths. Sections were then imaged with a fluorescence microscope, and fracture plane DZT was measured using ImageJ (n = 3–4 specimens per group) and analyzed as a function of ΔK. We observed a decrease in fatigue crack propagation resistance at 15 kGy compared to doses of 10 kGy or lower (p ≤ 0.013). Fracture plane DZT decreased overall with increasing radiation dose from 0 to 15 kGy. Sequential irradiation offered no improvement in fatigue crack propagation resistance (p = 0.98). Radiation-induced collagen chain fragmentation and crosslinking in this dose range likely contribute to a decrease in energy dissipation capability with increasing radiation dose. Other alternative radiation sterilization methods besides sequential irradiation may be warranted to mitigate radiation-induced tissue damage and extend the functional lifetime of structural cortical bone allografts.

Unnotched fatigue behavior of the laser powder bed fused and hot isostatic pressed Inconel 718 at 600 °C

The microstructure and mechanical properties of hot isostatically pressed (HIP) Inconel 718 additively manufactured using the laser beam powder bed fusion (LPBF) process were investigated at 600 °C, with emphasis on the high cycle fatigue behavior evaluated using the rotating bend fatigue tests, and elucidation of the role of γ” precipitate size on the fatigue resistance. Experimental results show that the unnotched fatigue strength (σf) of the peak aged alloy improves only by 7 % after HIP, as compared to that of the non-HIP peak aged alloy, despite a significant improvement in the ductility due to HIP. Over-aging the HIP alloy, however, led to a further enhancement (by ∼14 %) in σf. Fractographic analyses suggest that the fatigue crack initiation occurs from the intrusions and extrusions on the fracture surface of both versions of the aged alloy. Microstructural investigations reveal the presence of persistent slip bands (PSBs) with different morphologies in peak- and over-aged microstructures. A change in the deformation mechanism due to the size of precipitates was identified to be the reason for the formation of nano-grains (through dynamic recrystallization) within the PSBs of the alloy with a coarse γ” microstructure. In several {110} grains, ∼5 μm thick nanocrystalline grain zones formed on the specimen surface; they completely suppressed the formation of PSBs and enhanced the fatigue resistance of the HIP LPBF IN718 alloy in the over-aged condition.