Beam Degradation Research Articles

On the Problem of Composite Beam Degradation under Longitudinal Bending and the Solution Method for Large Displacements

On the Problem of Composite Beam Degradation under Longitudinal Bending and the Solution Method for Large Displacements

Degradation of RC short beams under monotonic and repeated loads after cryogenic freeze-thaw cycles

ABSTRACT To investigate the effects of cryogenic freeze-thaw cycles and repeated loading on the bearing capacity and deformation properties of reinforced concrete (RC) short beams, RC short beams with different reinforcement ratios were subjected to Minus 160°C cryogenic freeze-thaw cycles. Subsequently, a four-point bending tests were carried out under monotonic and repeated loading with the aim of exploring the performance characteristics of the test beams, such as failure mode, load‐deflection response, and ductility. Experimental results showed that the failure mode of RC short beams changed from ductile bending to brittle shear failure after cryogenic freeze-thaw cycles. Additionally, the load-carrying capacity, deformation properties and energy dissipation performance exhibited a significant degradation trend. There is decreasing trend for the ductility and ultimate bearing capacity of beams with the increase in freeze-thaw cycles, and the decrease degree was most obvious in the first three cycles. Moreover, compared with monotonic loading, the ductility index of normal temperature beam and freeze-thaw cycle short beam decreased more significantly under repeated loading, and the bearing capacity decreases more obviously under the last stage of multi-level loading and unloading cycles.

Stability investigation of Eu3+ doped CaF2 thin film with ZnO coating under electron beam irradiation

Eu3+ ion doped CaF2 thin film was successfully prepared using the hydrothermal method and coated by a spin coating technique. A thin layer of ZnO was deposited on the Eu3+ doped CaF2 thin film by pulsed laser technique. Incorporation of the dopant into the CaF2 crystal was confirmed by x-ray powder diffraction and x-ray photoelectron spectroscopy (XPS). Excitation of the film at 227 nm produced the characteristic emissions of Eu3+ ions. The stability of the film under electron beam bombard was studied using Auger electron spectroscopy, cathodoluminescence (CL), and XPS. The CL and Auger peak-to-peak heights (APPHs) data were collected concurrently using the same electron beam. The APPH of Ca and O increased, while that of F decreased, which indicated the conversion of CaF2 to CaO. The CL emission decreased initially during degradation and stabilized beyond 48 C/cm2 for the film with the ZnO coating. XPS analysis also indicated the dissociation of the fluoride compounds and subsequent formation of oxide compounds such as CaO and EuO after electron beam degradation.

Observation of fixed lines induced by a nonlinear resonance in the CERN Super Proton Synchrotron

The motion of systems with linear restoring forces and recurring nonlinear perturbations is of central importance in physics. When a system’s natural oscillation frequencies and the frequency of the nonlinear restoring forces satisfy certain algebraic relations, the dynamics become resonant. In accelerator physics, an understanding of resonances and nonlinear dynamics is crucial for avoiding the loss of beam particles. Here we confirm the theoretical prediction of the dynamics for a single two-dimensional coupled resonance by observing so-called fixed lines. Specifically, we use the CERN Super Proton Synchrotron to measure the position of a particle beam at discrete locations around the accelerator. These measurements allow us to construct the Poincaré surface of section, which captures the main features of the dynamics in a periodic system. In our setting, any resonant particle passing through the Poincaré surface of section lies on a curve embedded in a four-dimensional phase space, the fixed line. These findings are relevant for mitigating beam degradation and thus for achieving high-intensity and high-brightness beams, as required for both current and future accelerator projects.

Analysis of single particle and collective beam effects in high intensity beams in a periodic quadrupole channel

In high intensity proton accelerators, there are two main mechanisms that can cause beam degradation: incoherent and coherent effects due to nonlinear space charge forces. The incoherent effects represent the single particle dynamics while the coherent effects represent the collective response of the beam. Of particular interest is the region above a zero current phase advance (σ0) of 90° where the (coherent) second-order envelope instability and the (incoherent) fourth-order particle resonance are seen to lead to emittance growth. Large emittance growth is also seen below the envelope instability region as the full current beam phase advance (σ) decreases. In the present study, we have studied the nonlinear effects in a high intensity beam propagating through a focusing-defocusing (FD) quadrupole channel for σ0 greater than 90°, both analytically, by studying the solutions of Kapchinsky-Vladimirsky (KV) equation and the particle core model, and through detailed particle-in-cell (PIC) simulations using the code. The KV envelope equation gives the collective response of the beam while the particle core model gives the contribution of the single particle effects. With pic simulations, which resemble the behavior of the real beams more closely as compared to envelope calculations or the particle core model, it is possible to study the evolution of the beam in a self-consistent manner. Our studies show, that it is possible to identify the specific process responsible for beam degradation in high intensity beams. It is also possible to identify which process dominates under different conditions. We further show that the width of the emittance increase stop band calculated from PIC simulations is wider than that calculated by the envelope equations and that the width depends on the length of the channel being studied. Published by the American Physical Society 2024

Electron beam irradiation-induced co-grafting and degradation of cotton cellulose with ionic liquid

We developed a cellulose upgrading method based on electron beam processing technology by using a carbon-carbon double bond-containing ionic liquid as an auxiliary reagent. The irradiation of cellulose was implemented by a 10 MeV high-energy electron accelerator or a 200 keV low-energy electron accelerator. The established method enabled grafting of the ionic liquid onto cellulose while triggering an irradiation degradation of cotton cellulose. By employing irradiation co-grafting degradation with a high-energy electron accelerator in the dose range of 30–40 kGy, highly uniform cotton cellulose with a high degree of polymerization (DP) of 500 and low degree of polymerization deviation (DPD) was obtained. By using a low-energy accelerator in the dose range of 4–6 kGy, cotton cellulose with a high DP of 1000 and low DPD was prepared. This method to upgrade cellulose has advantages of simple operation, short reaction time, and minimal amount of chemical reagents. It opened an avenue to access high quality of cellulose that cannot be attained with other method.

A new empirical model for flexural stiffness of corroded post-tensioned concrete beams

Under service loading and environmental actions, the corrosion of steel strands would reduce the cracking load and ultimate load of post-tensioned concrete (PTC) beams. It also leads to the degradation of flexural stiffness, and hence increases the deflection of beams under the same load. In order to more effectively evaluate the stiffness degradation of corroded post-tensioned concrete (CPTC) beams, an empirical model is proposed in this work for assessing the stiffness considering the effect of the corrosion of steel strands. In the proposed model, cracking stiffness and stiffness after cracking are assessed separately, and the equations of cracking moment and ultimate moment are derived. The proposed model is verified by experimental data. Results show that the proposed model can efficiently predict the stiffness changes during the whole loading process, and the deflections predicted by the proposed model are in good agreement with experimental values. The proposed model is proved to be able to efficiently predict the stiffness degradation of CPTC beams caused by corrosion of steel strands, and can reveal the dependence of flexural stiffness on the corrosion loss of steel strands and the external loads.

Extension of Vortex Bessel Beams Generated by Finite-Width Durnin Ring With Helical Phase Modulation

Bessel beams are widely used for different applications due to their attractive non-diffractive behavior. However, the real-world Bessel beams have finite propagation distance, where such behavior can be assumed. In this work we consider the degradation of vortex Bessel beams generated by a finite-width Durnin ring with helical phase modulation. For this purpose, we derive the expression that describes the propagation of rotationally symmetric vortex beams. By using this expression, we show that the axial degradation of the main lobe of Bessel beams is almost independent on their topological charge and decreases by increasing the radius of the Durnin ring and its width. The increase of ring width also yields to the radial degradation (deformation of the secondary lobes) of the Bessel beams. These findings are particularly important for the construction of more sophisticated structured beams described as a linear superposition of vortex Bessel beams.

Second-Order Statistics of Self-Splitting Structured Beams in Oceanic Turbulence

Free-space optical communication is restricted by random media-stimulated beam degradation. However, partially coherent structured beams modulated by the coherence structure can potentially mitigate this negative effect. By employing the extended Huygens–Fresnel integral, we provide an examination of the second-order statistical features of a common type of partly coherent structured beams, self-splitting structured beams, in a turbulent ocean. The implications of turbulence parameters relating to the ocean and beginning beam parameters corresponding to the progression of such beam propagation attributes are fully investigated. Our numerical outcomes show that, for turbulence with a low-dissipation kinetic energy rate per unit mass of fluid, small Kolmogorov inner scale, large relative strength of temperature to salinity undulations, and large dissipation rate of mean-square temperature has a greater negative effect on the structured beams. In addition, we suggest an effective approach, enhancing the order of the beam and reducing the coherence length of the beams, to lower the oceanic turbulence-induced negative effects, and thus have future extensive possibilities in free-space optical communication.

Fatigue behavior and calculation methods of high strength steel fiber reinforced concrete beam

Adding steel fibers into concrete was considered as one of the most effective ways to restrain the crack development and improve the stiffness for reinforced concrete (RC) structures. To explore the reinforcement mechanism of steel fibers on the fatigue behavior of high-strength RC beam, eight high-strength steel fiber reinforced concrete (HSSFRC) beams subjected to fatigue loading were tested in this study. The main design parameters considered in this work were stress level and steel fiber content. The failure mode, crack patterns, fatigue life, crack width, and stiffness degradation of HSSFRC beams under fatigue loading were discussed. The results showed that steel fibers could significantly increase the fatigue life, restrain crack development, and improve crack patterns of HSSFRC beams under fatigue loading compared to ordinary RC beams. Both the crack width and stiffness degradation rate of beams decrease with increasing steel fiber content. Besides, the empirical formulas for calculating the maximum crack width and midspan deflection of HSSFRC beam under fatigue loading were proposed and validated using experimental results.

A novel design criterion for I-shape beams of steel MRF buildings in subduction-zone earthquake-prone areas

This paper highlights the difference in the seismic response of 5-storey, 10-storey, and 15-storey steel moment resisting frame (MRF) buildings of various span lengths (6 m, 7.5 m, 9 m), located on Site class C in Vancouver, B.C., Canada, resulted under the mega-thrust subduction zone ground motions against crustal ground motions (GMs). To emphasize on the impact of GM duration on the seismic response of buildings, seven spectrally equivalent short and long duration record pair sets were selected from ground motion databases and employed in analyses. Numerical models that account for P-Δ effects and strength and stiffness degradation of steel MRF beams were used. Detailed nonlinear dynamic analyses were conducted to assess the collapse safety according to FEMA P695 (2009) methodology. The results indicated high probability of buildings’ collapse under the long duration subduction GM suite, with a 38% average reduction in the median collapse capacity. Moreover, tall MRF buildings designed according to the current building code and steel design standard did not satisfy the collapse safety criteria when subjected to subduction GMs characterized by significant duration t5-95 > 60 s, while the middle-rise buildings showed borderline pass. To overcome this drawback, a novel design criterion for I-shape MRF beams is proposed; hence, selecting MRF beam sections of Class 1 that are able to achieve aggregated fatigue coefficient greater than the proposed limit value, the occurrence of low cycle fatigue of plastic hinge region of MRF beams is delayed and the collapse safety criterium is achieved.

Random error propagation on electron beam dynamics for a 50 MeV S-band linac

The stability and the quality of particle beams are of utmost importance for many emerging linac installations. The impact on beam properties damage of beam electromagnetic element misalignments and jitter/fluctuations in various accelerator sub-systems should be properly known, as usually such shot-to-shot fluctuations cannot be avoided. On top of that, knowing which parameters the machine is most sensitive to is of utmost to take precautionary measures to reduce the beam degradation and thus improve beam stability and quality. This simulation work focuses on a 50 MeV S-band linear accelerator based on RF photoinjector electron source. The sensitivity of the beam parameters towards several errors has been studied collectively as well as individually for each accelerator element. While the emittance at the end of the linac is dominated by the laminar behavior in the accelerating section, the main emittance degradation comes mainly from orbit errors located at the linac entrance.

Electron beam degradation of the cardiovascular drug salbutamol: Mechanisms and degradation pathways

With the increasing incidence and mortality of cardiovascular diseases, high consumption of the cardiovascular drug salbutamol (SAL) has made this compound an emerging pollutant in natural water and a challenge for traditional wastewater treatment. In this paper, an efficient advanced oxidation process was used to degrade SAL by electron beam (EB) irradiation. The results revealed that 100 mg L−1 of SAL could be nearly completely removed (95.1%) at 10 kGy and the degradation kinetic well followed pseudo first-order kinetic model. Different factors, including pH, inorganic ions and water matrix, had varying effects on the degradation of SAL owing to their important influence on the formation of reactive species in the aqueous solution. And it was found that eaq− played a major role in the degradation of SAL parent. Moreover, the addition of K2S2O8 (20 mM) increased the SAL mineralization rate from 2.9% to 64.2%, suggesting that oxidation free radicals could greatly improve the mineralization rate of SAL. Combining with the theoretical calculations and determined degradation by-products, four possible degradation pathways of SAL by EB irradiation were proposed, including H•, •OH and eaq− all participated in the degradation of SAL. Finally, toxicity evaluation suggested that the toxicity of SAL aqueous solution reduced after EB irradiation, indicating that it is an effective method to degrade SAL.

Mechanical performance of hybrid high-strength steel composite cellular beam under low cyclic loading

This study aimed to compensate for the impairments in structural load-carrying capacity and stiffness caused by conventional reduced web section beams, and to meet the strength design requirements for engineering. A new hybrid high-strength steel composite cellular beam (HHS-CCB) using high-strength steel in the beam flange and ordinary steel in the web was proposed. A composite cellular beam between the rigid joint and inflection point in the frame structure was selected as the research object, and low cyclic loading tests were conducted on one homogeneous ordinary steel composite cellular beam (HOS-CCB) and four HHS-CCB specimens. The effects of the hybrid use of high-strength steel and ordinary steel on the failure modes, load-carrying capacities, strength and stiffness degradation, ductility, and energy-dissipation capacities of the composite cellular beams were investigated. The test results show that with reasonable values for the diameter of the web opening and for the distance from the first opening at the beam end to the column surface (abbreviated as the hole edge distance), the HHS-CCB specimens exhibit local plastic damage at the first opening at the end of the beam but maintain a good ductility, stiffness degradation, strength degradation, and energy dissipation capacity, while significantly improving the structural load-carrying capacity loss owing to the web opening. Compared with HHS-CCB specimens using HHS in both the upper and lower flanges, the HHS-CCB specimens using HHS only in the lower flange show superior mechanical properties. Considering the poor plastic deformation capacity of HSS, the steel plate strength of the flange should not be much higher than that of the web to ensure the full development of plasticity in the cross-section, and Q460 steel or Q550 steel is generally recommended. A nonlinear finite element (FE) model was developed using ABAQUS software to predict the hysteresis behavior of specimens. Numerical simulation shows that the simplified FE model can be used to simulate the hysteresis performance of HOS-CCB and HHS-CCB.

Mechanism of shear strengthening for RC beam by drilling web openings based on experiment and 3D RBSM analysis

In practice, web openings are usually drilled in reinforced concrete (RC) beams to accommodate pipes and cable installations. But introducing web openings always causes shear degradation of RC beams. This study aims to establish a rational position design of multiple small web openings, which can improve the shear behavior of RC beams, by controlling the path of critical diagonal crack. Three-point bending tests on four RC beams without and with web openings (shear span depth ratio: 2.59 and 3.56) were firstly carried out to evaluate the strengthening effect attributed to the proposed placement of web openings. Besides, the Three Dimensional Rigid-Body-Spring Method (3D RBSM), a discrete numerical methodology, was applied to simulate the test process, and the strengthening effect due to the placement of web openings was parametrically investigated. Finally, the decoupling of shear components (beam and arch actions) was conducted to comprehensively understand the shear strengthening mechanism due to drilling web openings, by using RBSM-based methodology. The test and numerical results confirmed that the proposed position design of web openings could evidently improve the shear strength and deformation ability of RC beams, because the multiple web openings could increase the angle of critical diagonal crack, by predetermining it propagation path. Moreover, it was clarified that the strengthening mechanism of shear behavior owing to web opening setting was dependent on the more dramatic development of arch action with the increasing angle of critical diagonal crack. The present paper provided a rational design to solve the problem of shear degradation caused by small web openings in the field of concrete member design, and proved a possibility to strengthen the shear behavior of existing concrete beams by drilling web openings.

Experimental Study on Flexural Behavior of Seawater Sea-Sand Concrete Beams Reinforced with Superelastic Shape Memory Alloy Bars

In order to research the flexural behavior of shape memory alloy (SMA)-reinforced seawater sea-sand concrete (SWSSC) beams and improve their self-healing ability, three SMA SWSSC beams and one anti-corrosive steel bar SWSSC beam were designed. The influence of the reinforcement ratio, strength grade of SWSSC and type of reinforcement on the flexural performance of the beam were considered. The failure process, maximum crack width, mid-span deflection, displacement ductility and stiffness degradation of beams were studied by cyclic loading tests. The test results showed that the number of cracks in SMA-reinforced beams were significantly smaller than that in anti-corrosive-reinforced beams, and the crack width and mid-span deflection recovery effect were better after unloading. However, the effect of increasing the SMA reinforcement ratio on crack recovery was not obvious. The increase in SMA reinforcement ratio and the strength grade of SWSSC can significantly improve the bearing capacity of the beam and the stiffness, but the stiffness degradation rate decreased. Moreover, the ductility of concrete beams with SMA bars was significantly increased.

Operation of an Energy Recovery Linac with an Internal Target

Because an Energy Recovery Linac (ERL) decelerates and dumps the beam after at most a few passes, beam degradation in the interaction region that is orders of magnitude larger than in a storage ring is tolerable in such a device. As a consequence, some new types of Nuclear Physics experiments can be carried out. In 2016, an experiment (the DarkLight experiment) was installed in the Jefferson Lab FEL Driver ERL to test out this idea. The ERL had previously been used for FEL applications where high peak current and a large growth in energy spread was present. For the internal target, the machine setup required very small energy spread, and had to deal with large transverse emittance growth in the target. Additionally, the addition of a strong solenoid in the transport complicated the details of energy recovery. This presentation will describe how these new machine physics challenges were addressed.

Comparative study of the mechanical properties after proton irradiation of Al2O3 and Si-SiC ceramics for fusion breeding blanket applications

In this work, a study on the compression and indentation behavior of ceramic samples previously proton irradiated was studied. Prismatic bars were processed from commercial Al2O3 99.7%, and Si-SiC tubes manufactured by slip casting and extrusion, respectively. At least ten probes from each batch were submitted to high energy H+ ion beams (approximately 4.5 MeV) up to a fluence of 1.0 × 1016 ions/cm2 at both sample sides. A beam degrader was located inside the irradiation chamber to distribute the ions homogeneously in the target volume. The mechanical responses of these materials were examined for application as breeding blankets in nuclear fusion reactors, and their behavior after implantation was compared with similar bars in the as-received condition. Compressive and micro-indentation tests were carried out, obtaining the samples compressive strength, elastic modulus, hardness, and fracture toughness values. In addition, their relationship with the microstructure was studied by scanning electron microscopy. After ion irradiation, both ceramics show a reduction in compressive behavior. However, if the ceramics are compared with each other, the compressive properties after ion-irradiation are superior in the Al2O3 ceramic. From micro-indentation tests, no change in the material properties (hardness and fracture toughness) due to ion implantation at different depths was evidenced.

Beam physics design of a 30-MW beam transport to the target for an accelerator-driven subcritical system

The Japan Atomic Energy Agency's accelerator-driven subcritical system (JAEA-ADS) proposes the reduction of nuclear waste through the transmutation of minor actinides. The JAEA-ADS drives a 30-MW proton beam to a spallation target to produce neutrons for a subcritical 800-MWth reactor. The beam must be transported from the end of the linear accelerator (linac) to the target located inside the reactor core with high beam power stability and low peak density to ensure beam window integrity, which is a primary concern for the ADS project. Additionally, the design of the beam transport to the target (BTT) must be compatible with the established reactor design, and the elements that comprise the BTT must facilitate the maintenance and replacement of the fuel and the beam window. To this end, a robust-compact BTT design was developed through massive multiparticle simulations. First, the beam optics was optimized to guarantee beam window feasibility requirements by providing a low peak density of less than 0.3 μA/mm2. Then, beam stability was evaluated and improved by a simultaneous application of input beam and element errors. The input beam errors were based on the beam degradation obtained by implementing fast fault compensation in the linac, which is a key strategy to attain high-reliability operation. The results show that the BTT design fulfills reactor and beam window requirements for JAEA-ADS.

Experimental and numerical investigations on flexural performance of ultra-high-performance concrete (UHPC) beams with wet joints

Ultra-high-performance concrete (UHPC) wet joint beams with inverted trapezoidal keyed (ITK) joints were tested. A nonlinear finite-element model (FEM) for simulating the mechanical behavior of UHPC wet joint beams was also established. Parametric studies of the UHPC wet joint beams were conducted using the verified FEM analyses. The results indicated that the first visual crack and maximum crack width of the UHPC wet joint beams appeared at the wet joints. Improvements in the reinforcement ratio could significantly limit crack propagation and increase the flexural capacity of UHPC wet joint beams. The initial flexural stiffness of the UHPC beam was insignificantly affected by the wet joints, whereas the flexural stiffness degradation of the UHPC wet joint beams due to cracks was faster than that of the monolithic beam. The joint shape had a significant influence on the flexural performance of the UHPC wet joint beams. Among the keyed joints, the ITK joint exhibited the best flexural performance. The flexural performance of the UHPC wet joint beams with small-sized ITK joints was superior to that of large-sized joints. The difference in the flexural capacity between the UHPC wet joint beams and monolithic beams decreased as the reinforcement ratio increased.