Nominal Diameter Research Articles

Seismic Performance of Precast Drift-Hardening Concrete Walls Connected by Grout-Sheath Duct.

In order to find a suitable size of sheath duct and a reliable construction method for precast walls, a cast-in-place and five 1/2 scale precast drift-hardening concrete walls reinforced with weakly bonded ultra-high strength SBPDN rebars were fabricated and tested under reserved lateral load and constant compression. The experimental variables were the diameter of sheath ducts (45 mm, 100 mm, and 120 mm), embedded length (20d and 35d; d is the nominal diameter of SBPDN rebars), axial load ratio (0.075 and 0.15), and the construction method. The experimental observations, hysteresis behaviors, envelope curves, residual deformation, crack propagation, and energy dissipation were compared in the study. Moreover, a formula was applied to calculate the bond strength of the sheath duct. The experimental and calculated results revealed that increasing the axial load ratio and embedment length could not enhance the bond strength of the sheath ducts, and increasing the diameter decreased the bond strength significantly. Anchored the SBPDN rebars in smaller sheath ducts separately was a more stable connection method for precast concrete shear walls and provided sufficient drift-hardening capability, even at a large drift level (over 3%).

Comparison of Biomechanical Properties of the iCover and VBX Stent Grafts When Used as Bridge Stents in Fenestrated Endografts: An In Vitro Study.

The objective of this study was to compare in vitro the different biomechanical properties of 2 balloon-expandable covered stents, VBX (Viabahn VBX, W.L. Gore & Associates, Flagstaff, AZ) and iCover (iVascular, Barcelona, Spain), as bridging stents in fenestrated aortic endoprostheses. Three biomechanical tests were performed to evaluate a total of 12 stents (6 VBX 6 × 59 mm and 6 iCover 6 × 57m). First, a 3-point bending test was performed with a calibrated dynamometer to evaluate the bending strength of the 40% and 150% deformation of the system in its crimped state and the force necessary to deform the expanded stent by 40% with respect to its initial diameter. Then the stents were expanded to their nominal diameter inside a 6-mm-diameter handmade fenestration and flared up to 8 and 10 mm. The whole set was fixed in the dynamometer to carry out the pullout-force (perpendicular dislocation) and shear-stress-force (axial dislocation) tests. The resulting forces were recorded via the force transducer. Load, deformation, and displacement data were recorded in newtons. The results of each stent test were examined under the microscope, and both stent types were compared. Higher forces were required to bend the crimped VBX (16.24 N [IQR, 13.87-17.47 N] for the iCover and 19.01 N [IQR, 16.01-19.50 N] for VBX; P < 0.001), but lower forces were necessary for the expanded VBX compared with the iCover (0.36 N [IQR, 0.1-0.49 N] and 1.01 N [IQR, 0.97-1.09 N], respectively; p = 0.004). Pullout forces were 3.56 N (IQR, 3-4.1 N) and 7.07 N (IQR, 6.86-7.28 N) for the 8-mm flare and 7.29 N (IQR, 6.13-8.45 N) and 14 N (IQR, 12.05-15.95 N) for the 10-mm flare for the iCover and VBX, respectively (P = 0.333 for both comparisons). The shear-stress forces needed to dislocate the 6-mm iCover and VBX axially with a 10-mm flare to 50%, 100%, and 200% were 0.88, 1.61, and 3.55 N for the iCover and 0.71, 1.43, and 2.51 N for the VBX (P = 0.343, P = 0.486, and P = 0.486, respectively). After evaluating the stents under in vitro conditions, the VBX and iCover stents showed similar results in terms of biomechanical properties, which demonstrates their competence in in vitro conditions. Further in vitro comparisons with other stent grafts are required. The BECS used in FEVAR / BEVAR must ensure some properties to avoid the most frequent complications derived from the failure of these bridging stents (stenosis, thrombosis, stent integrity, dislodgement or endoleaks) that represent the most common cause for reintervention. This paper adds to the limited data available, information to the clinician after comparing some properties of two BECS used in these techniques that demonstrate their competence in in-vitro conditions.

Physics-informed and data-driven hybrid method for transmission accuracy design optimization of planetary roller screw mechanism

The planetary roller screw mechanism (PRSM) faces an ever-increasing precision transmission demand in current advanced equipment. The relationship between machining errors and transmission accuracy remains elusive due to the over-simplified physical models and small-sample experimental datasets. This work proposes a physics-informed and data-driven hybrid strategy for PRSM transmission accuracy evaluation and tolerance optimization. In the physical model, a PRSM transmission accuracy model is developed to calculate transmission error that considers 16 machining errors in eccentric, nominal diameter, pitch, flank angle, and roller consistency. In the dataset establishment, thread profile measurements and dynamic leadscrew inspections are conducted for the machining error and transmission accuracy data acquisition. A data augmentation approach combining the physical model with the generative adversarial network is utilized to predict travel deviation, variations, and axial backlash and estimate machining error contribution with the small-sample experimental dataset. It is firstly found that the roller consistency of nominal diameter significantly affects PRSM travel variation V2π with a 17.3 % importance value. With the developed framework, the key tolerances for screw, roller, nut, and roller consistency are optimized toward a typical precision transmission requirement using the non-dominated sorting genetic algorithm. It also provides a tolerance grade recommendation table with PRSM transmission accuracy level in engineering practice.

Bridged Ethylene Polyethylene Oxide Surfaces to Improve Packing Materials for Widepore Size Exclusion Chromatography.

Here, we describe the preparation of bridged ethylene polyethylene oxide (BE-PEO) surface-modified silica packing materials for size exclusion chromatography. BE-PEO surface-modified silica was hydrolyzed and subsequent 1H nuclear magnetic resonance analysis of hydrolysis products confirmed the successful formation of BE-PEO bonded surface. Silica particles exhibiting 3µm diameters and 1000 Å nominal pore diameters were selected as a base material for this work out of the critical need to improve analytical capabilities for the testing of cell and gene therapy drug products. Accelerated high pH aging study revealed significant enhancement in column stability. Multi-angle light scattering noise measurements showed inordinately lower baseline noise. Moreover, we evaluated the chromatographic performance of BE-PEO silica-packed columns through separations of a protein test mixture, DNA ladder, monoclonal antibody-based therapeutics, and adeno-associated viruses. BE-PEO silica columns demonstrated high resolution, high recovery separations that were confirmed to be reproducible and capable of extended column lifetimes and exhibited low ionic and hydrophobic secondary interactions. In summary, BE-PEO silica particles have yielded a new level of performance, improved base stability, and inherently lower baseline noise. These novel widepore particles will facilitate more sensitive size-based detection and characterization of large biologics in the form of advanced gene therapy products.

The effect of unintended porosity on the first compressive stress maximum of alumina hollow sphere-filled bimodal composite metal foams

Bimodal composite metal foams made from Al99.5 aluminium and quasi-eutectic Sr-modified AlSi12 matrix were investigated, where the bimodality was introduced by two alumina hollow sphere sets with nominal diameters of Ø7.0 and Ø2.4 mm in various volume concentrations. The research aimed to determine the effect of the cell structure (especially the unintended porosity) on the first compressive stress maximum, depending on the applied matrix material. The various features of the cell structure were quantitatively measured in composite metal foams by filtering raw computed tomography analysis data. The casting porosity, the wetting porosity, the porosity from the various-sized hollow spheres, and the partially matrix-filled hollow spheres have been successfully distinguished based on volumetric and geometrical conditions, such as sphericity and compactness. The unintended porosity (as the sum of the casting porosity and the wetting porosity) influences the first compressive stress maximum of the Al99.5 matrix composite metal foams. In contrast, for the AlSi12Sr bimodal foams, the results correlated with the total porosity values. The first compressive stress maximum could be estimated well from the compressive yield strength of the matrix and the total porosity of the foam.

Density, thermal expansion, dynamic viscosity of halogenated arenes

Purpose. Experimental study of the density, thermal expansion and dynamic viscosity of halogenated arenes at temperatures from 293.15 to 343.15 K and atmospheric pressure 97.992 kPa.Methods. Density was determined by the pycnometric method, viscosity by the capillary method. A quartz pycnometer type PZh2 with a nominal capacity of 10 ml and a glass capillary viscometer type VPZh-2 with a nominal capillary diameter of 0.34 mm were used. The mass of liquids was measured using an electronic scale VSL-200/0.1A with a division value of 0.0001 g. Numerical methods were used to process the experimental results.Results. Experimental data were obtained on the density, coefficient of volumetric thermal expansion and dynamic viscosity of liquid o-xylene, ethylbenzene, fluorobenzene, chlorobenzene, bromobenzene, toluene, o-fluorotoluene, mfluorotoluene, p-fluorotoluene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, 2,4-dichlorotoluene, 2,6-dichlorotoluene. Density and dynamic viscosity data are approximated by a third-degree polynomial. Data on the coefficient of volumetric thermal expansion are obtained from approximated measured density data. The maximum estimate of the measurement error for density was 0.13 %, for dynamic viscosity – 3.5 %. The maximum calculation error for the coefficient of thermal expansion is estimated at 3 %.Conclusion. Mathematical processing of the obtained experimental data on density and dynamic viscosity made it possible to obtain analytical relations in the form of power polynomials that allow calculating the values of these quantities at any temperature from the studied temperature range and atmospheric pressure with an error not exceeding the error of experimental determination. The calculated values are in good agreement with the data provided in the reference and scientific literature. The experimental data obtained complement the information on the properties of some of the liquids under consideration, for which the dependences of density and viscosity on temperature are poorly understood. The substances under study are used in various sectors of the economy and are therefore technically important liquids. The measurement results can be used in condensed matter physics, for the analysis of liquid hydrocarbons, and can be useful in the chemical industry.

Cyclic bond behavior and bond stress – slip model of steel strands in steel fiber reinforced concrete

To study the bond performance of steel strands in steel fiber reinforced concrete (SFRC), bonding tests under monotonic and cyclic loads were performed on the specimens with different steel fiber volume fractions (SFVFs), bond lengths, nominal diameters of steel strands and SFRC strengths. The results showed that the relative rotation between the steel strand and SFRC occurred when the steel strands were vertically pulled out from SFRC due to the smooth and continuous helical shape of the steel strands. For the specimens with the same parameters, the maximum bond stress under cyclic load decreased by 1.67–22.88 % than that under monotonic load. The maximum bond stress under cyclic load increased with the increasing SFVFs or SFRC strength. Notably, the maximum bond stress under cyclic load also increased with the increasing bond length or diameter of steel strands, significantly different from that of ordinary ribbed steel bars and FRP bars. The cumulative energy dissipation (CED) of bond specimens increased with the diameter of steel strands and SFRC strength. Besides, the SFVFs had a positive effect on the CED, but simultaneously increasing diameter of steel strands would weaken the positive effect of SFVFs, and simultaneously increasing bond length had no obvious on the CED. Finally, a bond stress – slip model of steel strands in SFRC was established, suitable for calculating bond stress – slip curves under random and complicated loading schemes. By comparing the calculation and test results of bond stress – slip curves, it was proved that the proposed model had an acceptable accuracy and could describe the influence laws of SFVF, bond length, nominal diameter of steel strand and SFRC strength well.

Experimental study of two-phase pressure-drop in horizontal return bends with ammonia

In evaporators and condensers of refrigeration and air conditioning systems, various straight tubes are joined via U-bends. These U-bends result in higher pressure drops due to flow disturbances and centrifugal effects. Accurate prediction of pressure drops in these bends is essential for reliable design and operation. This study investigates the two-phase flow pressure-drop in horizontal U-bends with ammonia under wide range of experimental conditions. Three pipes with nominal outer diameter between 22.2, 15.9, and 9.5 mm were used, each with three bend radii (R/do ratio) between 1.2 and 2.5 in horizontal configuration. Tests were conducted at saturation temperature of +10 and -15 °C, with mass flux varying between 10 and 50 kg m−2 s−1, and vapor quality between 0.1 and 0.9. The pressure-drop increased with mass flux and vapor quality while decreased with saturation temperature, pipe diameter and R/do ratio of the bend.Large tubes exhibited a greater increase in pressure drop with rising mass flux and decreasing bend ratio compared to small tubes, which showed higher absolute values and more consistent performance across the vapor quality range at both saturation temperatures. The tube diameter had a less significant effect at high saturation temperature and high mass flux, while the bend curvature ratio predominantly influenced the pressure drop performance for large diameter tubes. One correlation from the literature predicted the data well only if the vapor quality was below 0.5. For wider range of quality, the existing models in the literature were not well-suited for predicting pressure drops in ammonia U-bends.

Investigation on local mooring stresses of floating offshore wind turbines considering mooring chain geometrical and material nonlinearity

As the renewable energy industry moves towards deep water, mooring chains play an irreplaceable role in position keeping. The geometrical and material nonlinearity of the mooring chains significantly affects moored platform responses and mooring responses. To investigate local mooring stress evolution under wave loads, a simulation method was proposed, combining hydrodynamic loads derived from fully coupled simulations of floating offshore wind turbines (FOWTs). The simulation method, embedding the lumped mass mooring model, was validated by comparing the experimental data from OC4 semi-submersible wind turbines. Their reasonable segment numbers and the mooring structural damping ratio were also discussed. Based on the validated simulation technology, a coupled 3D-mooring analysis was performed, replacing linear mooring stiffness suggested in FAST tutorials with nonlinear mooring stiffness calculated by axial stretching the real-sized 3D chains. The nonlinear mooring stiffness is assumed, taking into account detailed geometry, nonlinear material properties, and contact behavior between chains. The nominal diameter of the real-sized 3D-chains was determined, so that the chains had the same volume per unit length as the validated case, ensuring a similar Morison's force on the mooring line. Then, the local mooring stresses were investigated by loading the derived nonlinear fairlead tension onto both sides of real-sized 3D chains in an explicit finite element software. The evolution of local mooring stresses under design wave loads with different wave headings of 0, 30, 60° was compared and discussed. As wave direction increases, this study indicated that the amplitude of local maximum principal stress decreases and its phase leads. Additionally, its magnitude is mainly influenced by axial tension force and contact behavior.

Translucent Si Solar Cells Patterned with Pulsed Ultraviolet Laser Beam

We report an application of a pulsed ultraviolet (UV) laser (λ = 355 nm) in producing translucent Si solar cells. This process efficiently generates a densely packed microhole array on a fully fabricated Si P‐N junction solar cell in just a few minutes. Herein, prototype cells with a nominal microhole diameter of 23 μm with a spacing between 60 and 300 μm are fabricated. High‐resolution electron‐beam microscopy reveals that the UV laser beam introduces amorphized silicon oxide (SiOx) in proximity to the patterned microholes via localized heating in air. Quantitative photovoltaic (PV) analysis shows a decline in the open‐circuit voltage (Voc) and the fill factor (FF) of the cells with the increase in the microhole density, likely due to the P‐N junction damage during the laser beam irradiation. Despite the reduction in Voc and FF, the solar cells retain a short‐circuit current density (Jsc) above 90% without post‐processing. The inherent microhole geometry associated with the laser beam profile allows multiple light scattering within the confined microhole structure, enhancing the translucency of the cells. While further development is required for optimization, these findings support the potential use of UV laser beams for fast and scalable production of translucent solar cells.

Numerical Analysis of a Self-Acting Gas Bearing Lubricated with a Low-Boiling-Point Medium Using an Advanced Model Based on the Finite Difference Methods and Universal Computational Fluid Dynamics Software

Methods for determining the characteristics of self-acting (aerodynamic) gas bearings have been developed for many years, but many researchers and engineers still question how sophisticated a model of such bearings should be to obtain reliable results. This is the subject of this article, which presents a numerical analysis of aerodynamic gas bearings using two alternative methods: a specialized program based on the finite difference method, and a universal CFD program using the finite volume method. Gas bearings with a nominal diameter of 49 mm, designed for a 10 kW turbogenerator operating at a rotational speed of 40,000 rpm, are analyzed. The vapor of the low-boiling medium, designated HFE-7100, is used as the bearing lubricant. The calculations focus on determining the position of the bearing journal where the bearing achieved the required load capacity and checking the bearing characteristics beyond the nominal operating point. The most important results obtained by the two independent methods are compared, and recommendations are made for those interested in the numerical analysis of self-acting gas bearings.

Dynamic Characterization of Diameter for Round Surfaces using a Non-contact Optical Measurement System

Ensuring uniformity in the final round product's diameter is essential to production line operations because it permits adherence to geometry specifications and fulfills client demands. Non-contact diameter measurement systems are essential for manufacturing cost savings as well as quality monitoring. However, because of their non-linear movement, lengthy manufactured specimens like rods might be difficult to measure the diameter of precisely. Typically, analysis systems rely on costly and intricate optical components, limiting accessibility to small businesses. This research aims to address this issue by presenting a low-cost and practical optical system for measuring the diameters of round samples in continuous lines. The aim here is to obtain instant feedback through dynamic measurement and to create a continuous control mechanism that will contribute to sustainability. Experimental results show that the proposed method exhibits a high level of precision, with a measurement accuracy of 0.25% of nominal diameter.

Exploring the relationship between embedment behaviour in cross-laminated timber and its layers: An experimental study

Cross-laminated timber (CLT) has become popular as a construction material and the design of CLT connections is typically based on empirical equations with an average embedment strength of the wood-based product. The experimental study presented herein aims at enhancing the understanding of the relationship between the CLT embedment behaviour and the single layers it is composed of. Non-linear embedment stress–displacement relationships were measured in 244 full-hole and half-hole embedment tests on structural timber boards as well as on CLT produced of parts of the same boards. Three different fasteners, namely a steel dowel with a diameter of 12 mm and the threaded part of screws with a nominal diameter of 6.5 mm and 10 mm, were studied. The design of the experiments allowed to validate a simple mechanical model with parallel springs for the CLT, which showed good agreement with experiments. In addition to a validation of the non-linear spring model, this unique experimental data-set is further exploited in a comparison with empirical equations and for the derivation of a non-linear embedment ratio, between parallel and perpendicular to the grain embedment stresses, over the displacement. Knowledge of the relationship between the non-linear embedment behaviour of the single layers and the CLT element can be further exploited in the engineering design and numerical modelling of CLT connections with dowel-type fasteners.

Development and Testing of Small-Scale Flash Dryer for Maize Bran

Sun drying is the most common technique used to dry various food products due to its economic convenience. However, it is not effective owing to its unreliable nature leading to microbial deterioration and aflatoxin contamination of food. In Tanzania, about 1.3 million tonnes of maize bran are at risk of deterioration annually due to improper drying. The aim of this study was to design, fabricate and test an efficient small-scale flash dryer for maize bran. Using principles of material and energy balance, a small-scale flash dryer with a throughput of 500 kg of dry product per hour was designed resulting in a nominal diameter of 387 mm and a drying length of 20 m. Design calculations and drawings were done using MS Excel 2021 and SolidWorks 2018 respectively. Empirical procedures were used to fabricate and test the dryer. The material of construction used in the flash duct was food grade (stainless steel, SS 201). A fuel blend of Waste Engine Oil (WEO) and diesel (85%-15%) was used with a novel heavy oil burner. It was observed that at an inlet air temperature of 150 °C and air velocity of 12 m/s, moist maize bran was dried from 37% to 10% w.b. The fabricated flash dryer's energy efficiency, specific energy consumption, and specific energy utilization are 74%, 3.4 MJ/kg water evaporated, and 1.71 MJ/kg dry maize bran respectively. It was concluded that the fabricated small-scale flash dryer displayed improved energy performance compared to others presented in literature. Better instrumentation was recommended for feedback control on burner operation and process monitoring which further enhances the performance of the fabricated small-scale flash dryer.

Experimental studies on bond behaviour of steel rebar with different rib patterns in concrete

The bond between concrete and steel rebar is one of the most crucial parameters in the construction of reinforced concrete structures. The load-bearing capacity and serviceability of these structures depend heavily on bond strength. The rib pattern of the rebar plays a significant role in enhancing bond behaviour. The impact of different rebar patterns on bond studies in the concrete mix is found to be limited. In the study, six concrete mixes were prepared and tested. Three of these mixes incorporated fly ash in varied amounts to partially replace cement, while the other three mixes had no fly ash. Three different rib patterns of steel bars were embedded into these six grades of concrete. The pull-out tests were used to assess the bond strengths of various combinations in accordance with RILEM recommendations. The findings show that the ribs in rebars significantly increase mechanical interlocking whereas the presence of fly ash improves chemical adhesion in bond behaviour. Particularly, pattern 2 rebar (transverse rib thickness, 0.797 mm; transverse rib width, 2.06 mm; rib spacing (inner to inner), 6.428 mm; longitudinal rib thickness, 1.04 mm; longitudinal rib width, 2.312 mm; rib inclination angle, 66.39o; nominal diameter, 16 mm; length of transverse rib, 25 mm) exhibited notably superior bond strength, reaching a maximum of 17.21 MPa in M30 grade concrete in which 95 kg/m³ of fly ash was used as a replacement for cement.

2D3C Measurement Of Velocity, Pressure And Temperature Fields In A Intake Flow Of An Air Turbine By Filtered Rayleigh Sattering (FRS) And Validation With LDV And PIV

A Filtered Rayleigh Scattering Technique is implemented in two different experimental setups and compared to the established velocity measurement techniques Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV). The Frequency Scanning Filtered Rayleigh Scattering Method employed uses an imagefiber bundle which allows for the simultaneous observation of the flow situation from six independent perspectives, utilizing only one sCMOS camera. A testrig with a nominal diameter of 80 mm was implemented by ILA R&amp;D GmbH. Here measurements with straight pipe flow and a swirl generator were realised, as well as comparisions with LDA. A second experiment utilized Cranfields University’s Complex Intake Facility (CCITF), enabling the simulation of the flow field for an engine intake as observed behind an S-Duct diffuser. The diameter in the measuring plane was 160 mm. Measurements up to a mach number of 0.4 were performed and compared with HighSpeed Stereo-PIV (S-PIV) measurements. Good agreement was achieved in respect to both the absolute magnitude of the velocity measurements as well as to the resolution of complex flow structures. The developed FRS multi-view Setup is able to simultaneously determine the 3D velocity components, the pressure and the temperature on a measurement plane with high resolution and without seeding. After calibration the FRS system yields the pressure and temperature within 3 percent respectively 0.8 percent of the reference values. The measured velocity was within 1-2 m/s of the reference.

Investigation of Machining Different Nominal Thread Diameters with the Same Thread Mill Tool Due to Varying Revolution Radius of Helical Interpolation Motion

Investigation of Machining Different Nominal Thread Diameters with the Same Thread Mill Tool Due to Varying Revolution Radius of Helical Interpolation Motion

Exploring single-shot propagation and speckle based phase recovery techniques for object thickness estimation by using a polychromatic X-ray laboratory source.

Propagation and speckle-based techniques allow reconstruction of the phase of an X-ray beam with a simple experimental setup. Furthermore, their implementation is feasible using low-coherence laboratory X-ray sources. We investigate different approaches to include X-ray polychromaticity for sample thickness recovery using such techniques. Single-shot Paganin (PT) and Arhatari (AT) propagation-based and speckle-based (ST) techniques are considered. The radiation beam polychromaticity is addressed using three different averaging approaches. The emission-detection process is considered for modulating the X-ray beam spectrum. Reconstructed thickness of three nylon-6 fibers with diameters in the millimeter-range, placed at various object-detector distances are analyzed. In addition, the thickness of an in-house made breast phantom is recovered by using multi-material Paganin's technique (MPT) and compared with micro-CT data. The best quantitative result is obtained for the PT and ST combined with sample thickness averaging (TA) approach that involves individual thickness recovery for each X-ray spectral component and the smallest considered object-detector distance. The error in the recovered fiber diameters for both techniques is , despite the higher noise level in ST images. All cases provide estimates of fiber diameter ratios with an error of 3% with respect to the nominal diameter ratios. The breast phantom thickness difference between MPT-TA and micro-CT is about 10%. We demonstrate the single-shot PT-TA and ST-TA techniques feasibility for thickness recovery of millimeter-sized samples using polychromatic microfocus X-ray sources. The application of MPT-TA for thicker and multi-material samples is promising.

Effect of Corrosion Inhibitors on Bond Strength of Reinforced Concrete Structures

Corrosion of steel reinforcement is a major factor affecting the durability and strength of reinforced concrete structures. This study investigated the influence of plant-derived corrosion inhibitors, applied as coatings, on the bond strength between reinforcing steel and concrete. Thirty-six 150 mm concrete cubes with 12 mm diameter embedded steel bars were prepared and divided into uncoated, corrosion inhibitor coated, and control groups. The samples were immersed in 5% sodium chloride solution over 360 days to accelerate corrosion. Pull-out testing measured the bond strength and failure load. The corroded samples showed 31-26% lower bond strength and 82-87% higher maximum slip than controls, indicating corrosion damage at the steel-concrete interface. However, inhibitor-coated samples displayed 24-36% higher bond strength and 42-43% lower maximum slip versus corroded samples. Although the coatings did not fully restore original bond strength, this demonstrates their effectiveness at protecting bond properties. Microscopic analysis revealed non-uniform, localized corrosion preferentially initiated at steel defects. Statistical correlations confirmed the direct relationship between steel weight loss and reductions in post-corrosion rebar weight due to material loss. While nominal rebar diameters showed minimal differences between sample types, localized diameter reductions and cross-sectional area increases in corroded samples highlighted discrete corrosion effects. These were mitigated in coated samples. Together with direct weight loss measurements, this proves corrosion occurred in unprotected samples. Overall, the significant recovery of bond strength, slip resistance, diameter, area, and weight in coated samples validates the success of the natural corrosion inhibitors in reducing steel deterioration and interface degradation. The results provide new insights on optimizing inhibitor coatings to maximize corrosion protection for reinforced concrete structures.

A Cutting Force and Hole Geometry Study for Precision Deep-Hole Microdrilling of Magnesium.

Size effects, high thrust forces, limited heat dissipation, and tool deterioration are just some of the challenges that deep microdrilling poses, underscoring the importance of effective process control to ensure quality. In this paper, an investigation performed on a microdrilling process on pure magnesium using a 0.138 mm diameter microdrill to achieve an aspect ratio equal to 36 is proposed. The effect of the variation of the cutting parameters feed per tooth fz and cutting speed vc was studied on thrust force, supporting hole quality evaluation in terms of burr height, entrance, and inner diameters. The results showed that fz significantly influences the hole quality. In fact, as fz increases, the burr height decreases and the inner diameter approaches the nominal diameter. However, optimizing the hole geometry with high feed per tooth values increases the thrust forces, compromising tool life. In fact, a significant dependence of the thrust force on both cutting parameters was found. In this scenario, increasing vc can mitigate the high thrust forces by inducing material softening. The study results improve precision manufacturing by refining parameters, ensuring the quality and reliability of magnesium-based microcomponents.