Rod Modes Research Articles

Investigating the robustness of interface topological modes in rods

Topological phononic crystals and metamaterials are structures that can present waveguiding and energy concentration phenomena, which can be of interest in structural dynamics for energy harvesting and passive vibration and noise control. The periodicity of the typical phononic crystals and metamaterials is broken for these structures, which need to present at least two crystal lattices with different topological characteristics. Thus, the topological invariant, such as the Zak phase, which defines the topological characteristic, must be computed. A rod metastructure exhibiting two low-frequency band gaps, each with a topological interface mode, was designed. It has bolt sets whose weights generate variability, which was modeled and inferred. In order to increase variability along the rod metastructure, washers were included or removed. Experiments were performed to validate the simulations. It was observed that the variability of the topological mode in the first band gap is more robust considering its mode shape, natural frequency, and energy concentration at the interface than the second interface mode, at higher frequency. As variability increases, the robustness of the energy concentration at the interface and of the mode shape of both topological modes decreases. The same behavior was observed for the natural frequencies of the topological modes.

Investigation on the influence of electrospark deposited 718 alloy coating on the penetration performance of 93 W rod

A ballistic experiment on a semi-infinite RHA target impacted by two thicknesses clade 93 W rods (200 μm 718 alloy and 400 μm 718 alloy) with an impact velocity of 1500 ± 50 m/s is conducted to investigate the influence of 93 W surface deposited coating on penetration performance. Moreover, the findings are compared with those of an unclad 93 W rod. This study aims to provide a comprehensive microstructural overview of the penetration process, including the solid-state penetrator flow and the exchange interaction mode of rod and target (R.T.) materials, using optical metallography and electron microscopy. Results indicate that the coating area is composed of approximately equiaxed or short columnar cellular crystals. Furthermore, a metallurgical fusion layer is formed between the substrate and the coating, ensuring excellent bonding strength of the coating. No significant difference in the rheological mode is found between the interfaces of the 200 μm 718 alloy and 93 W R.T. materials, while the 400 μm 718 alloy forms a barrier mix zone at the interface between the R.T. This phenomenon alters the exchange mode of the target material and affects the interface flow mechanism. The barrier mix zone also acts as a solid-state lubricant at the interface, reducing the resistance to the rod's penetration. The average penetration depth of the 400 μm clad rod is 6.89 % higher than that of the 93 W rod. This finding reveals the clad material enhances the rod's performance and provides self-lubricating characteristics.

Elastic wave spin and unidirectional routing in thin rod systems

The unusual topology of elastic waves in continuum systems has been recently uncovered. Prominently, the spin of Rayleigh-Lamb waves has been experimentally observed and used to achieve the unidirectional wave propagation. In this work, the elastic wave spin in thin rod systems is theoretically predicted and experimentally observed, for all the three basic wave modes, i.e., the zero-order flexural, longitudinal and torsional modes. By elaborately building up the subwavelength chiral sources, the spin-momentum locking has been achieved for these three modes within broad frequency range. Interestingly and surprisingly, the spin-momentum locking occurs for flexural and longitudinal modes in both circular and non-circular thin rods; the spin-momentum locking for torsional modes only exits in non-circular thin rods, due to the warping effect in non-circular cross-section rods. Our results open up the door for elastic wave spin in thin rod systems, and provide general tips for the research on basic modes in diverse thin rods, based on either the continuum media or the artificial metamaterials in future.

Improvement of Efficiency in 976 nm Fiber Amplifier by Spectral Filtering in Yb-Doped Fiber with Absorbing Rods Embedded in the Cladding

A novel Yb-doped fiber design for improved lasing near 976 nm based on spectral filtering of the amplified spontaneous emission near 1030 nm was realized and investigated. A very sharp short-pass filter was implemented by adding appropriately chosen high-index absorbing rods into the silica cladding. In this case, the resonant interaction of the core mode with the high-index rod mode could be controlled by fiber bending, which allows for the precise adjustment of the stop-band position. It was shown that the utilization of Sm-doped absorbing rods allows one to achieve very high absorption of emission at unwanted wavelengths, but it also adds background losses for the pump near 915 nm and for the signal at 976 nm. Despite this fact, the improvement of efficiency in the 976 nm fiber amplifier, after shifting the stop-band to 1000 nm, was clearly demonstrated. Based on theoretical calculations, it was shown that, after optimizing the fiber parameters, a further twofold improvement in efficiency was possible despite the excess losses at the pump and signal wavelengths.

Combined effects of axial and lateral loading for Glued-In steel rods in laminated veneer lumber

Glued-in rod timber connections are used to achieve structural continuity in timber structural members and as moment connections due to their high efficiency, stiffness and axial load transition. Existing studies have focused on axial withdrawal load capacity but there is limited research on laterally loaded glued-in rods and combined effects of lateral and axial loading which is common loading condition for all connections. This study investigates the relationship between axial and lateral loading in the ductile failure modes of glued-in steel rods in hardwood LVL. In all specimens an unbonded length was provided based on the latest design recommendations to mitigate splitting failure. The experimental findings suggest that the introduction of lateral load had no effect on the axial load capacities of the rods when the governing failure mode was rod yielding. This is not currently addressed in Eurocode 5. The lateral force capacity exceeded the design code prediction by 82%, and design recommendations are discussed for more accurate estimation of the lateral capacity. The use of the component method can be adopted to estimate accurately the rotational stiffness of moment connections with glued-in rods in LVL.

Field experimental study on the pull-out characteristics of a new type of expanding shell bolt

Rock bolt foundation is becoming increasingly popular for transmission line engineering in mountainous areas due to the ability to maximize rock foundation bearing performance, reduce foundation size and burial depth, and save investment. However, failure modes such as pull-out of bolt can lead to insufficient utilization of bearing capacity of rock bolt. To overcome this problem, a new form of expanding shell bolt is proposed and the effect of several variables including grouting materials, bolt diameter, site weathering degree, and anchoring depth are investigated in this study. The results indicate that the new expanding shell bolt may significantly increase the pull-out bearing capacity compared to common rock bolts, due to the built-in effect between the bottom part of bolt and the rock on the hole wall. The effect of grouting material and anchoring length on the shell anchor's uplift bearing capacity is minimal. Considering that the ultimate tensile strength when the anchor bar breaks depends on the diameter of the steel bar, increasing the diameter of the anchor bar will effectively improve the pull-out characteristics of the bolt. The failure mode of anchor rods is also influenced by the rock layers. Rock layers with lower weathering levels have stronger embedding force, and the expansion head can effectively play a role. Due to the group anchor effect, the ultimate uplift bearing capacity of group anchor foundation in rocks is not simply the sum of the bearing capacity of each one, but must be multiplied by the group anchor coefficient. This coefficient is close to 0.9 in moderately weathered and strong-medium weathering sites. Finally, the calculation method for ultimate pullout force of expanding shell bolt is established. The feasibility of this method is verified by comparing on-site test values and calculated values.Author keywords: Rock bolt; Expanding shell bolt; Pull-out bearing capacity; Failure mode; Group anchor effect.

Preparation and penetration behavior of the reactive fine-grained tungsten heavy alloy

A new reactive fine-grained tungsten heavy alloy (RF-WHA) with self-sharpening ability was developed, which is a high-density and -strength material for armor-piercing projectiles with excellent penetration performance and reactive energy-releasing properties. This paper introduces the preparation method, microstructure and mechanical properties of the RF-WHA. Comparative experiments were conducted between RF-WHA and the conventional tungsten heavy alloy (WHA) long rod penetrating semi-infinite medium‑carbon steel target at impact velocities ranging from 1000 m/s to 1700 m/s using a 25 mm ballistic gun. The depth of penetration (DOP), crater channels and residual rods of the RF-WHA and WHA at different velocities were obtained. The experiment results show that the RF-WHA rod has reactive energy-releasing properties, and the DOP of the RF-WHA rod is 10%–15% higher than that of the WHA rod. The RF-WHA rod has an excellent self-sharpening behavior during penetrating. The failure mode of the RF-WHA rod was described by systematically analyzing the macroscopic morphological and microscopic metallurgical of crater channels and residual rods. It is noted that the self-sharpening behavior is related to the adiabatic shear sensitivity and brittle behavior of the RF-WHA under high and medium strain rate loading.

Numerical modeling investigation of cross-laminated timber connections consisting of multiple glued-in rods

Glued-in rods are stiff and high-capacity connections that are used in timber structures. Regardless of the many advantages of glued-in rods, research on the glued-in rods in CLT is limited, especially on numerical modeling. This paper provides the numerical modeling principles, validation details, and parametric studies of glued-in rods embedded on the edge of CLT. The numerical modeling was performed on a 3D finite element basis, and the cohesive surface method was used to define the bond lines along the rods. To validate the numerical models, 24 replica experiments were performed and investigated the effect of the rod diameter and of the embedment length on the pull-out strength of rods embedded perpendicular, parallel, and on the boundary of two cross-wised layers. The numerical models were validated according to the maximum load, stiffness, as well as the failure mode of the glued-in rods. The numerical models showed high reliability in simulating the experiments and predicted the strength of the glued-in rods with a maximum of 4% difference. After validation of the numerical models, the parametric study covered the pull-out strength investigation of rods with 20, 24, and 30 mm diameter and anchorage lengths of 250, 350, and 450 mm embedded in the perpendicular, parallel, and on the boundary of cross-wised layers on the edge of 5 and 7 layer CLT panels. The findings showed that increasing the embedment length and rod diameter enhanced the pull-out strength of the glued-in rods, regardless of where the rod was positioned on the CLT's edge. Rods embedded perpendicular to the grain showed the highest pull-out strength, and two rods with 30 mm diameter and 450 mm embedment lengths reached 961 kN pull-out strength. Numerical models showed that for the same diameter and embedment length of two rods embedded on the parallel and on the boundary of two cross-wised layers reached 836 and 738 kN pull-out strength, respectively. Finally, A design equation is provided to determine the pull-out strength of the glued-in rods embedded in CLT based on the shear strength of the bondline.

Calculation model of concrete-filled steel tube arch bridges based on the “arch effect”

In view of the limitations of the current code based on the equivalent beam-column method with the “rod mode” instead of the “arch mode” for the calculation of concrete-filled steel tube arch bridges, this paper takes the real bearing mechanism of the arch as the starting point and analyzes the different bearing mechanisms of the arch and eccentric pressurized column. The concrete-filled steel tube arch model test was carried out to analyze the deformation state and damage mode, and the geometric non-linear bending moment of the measured arch was compared with the bending moment value calculated by the eccentricity increase coefficient of the “rod mode.” The results showed that the transfer of internal force is from the axial force to the arch axis, causing the vertical reaction force and horizontal thrust. However, the eccentric compression column only produced the vertical force at the bottom and combines with the lateral deformation indirectly generated by the eccentric distance. In addition, the deformation stage of the arch is basically the same as that of the eccentric compression column. The final failure mode of the arch is 4-hinge damage, and the final failure mode of the eccentric compression column is single-hinge damage. The preliminary geometric non-linear bending moment value obtained by the two modes accords well. Therefore, the main factors for the difference in the bearing mechanism between the two modes are different force structures, force transmission routes, and sources of deformation. Due to the difference in the bearing mechanism, the final failure mode is different, and the deformation ability of the arch is weakened by using the “rod mode” instead of the “arch mode.” The geometric non-linear bending moment of the control section calculated by the eccentricity increase coefficient is conservative, but the influence of the geometric non-linearity of other sections is not considered enough.

On the cyclic change in the dynamics of the IBR-2M pulsed reactor

It is shown that in the IBR-2M reactor by the end of the reactor cycle, changes in dynamics are observed associated with a strong weakening of the fast power feedback (PF), as a result of which the reactor becomes oscillatorily unstable. After each week of zero-power operation the negative changes in reactor dynamics disappear and the stability of the reactor is restored. Thus, the reactor undergoes cyclic changes in the oscillatory instability. The correlation between of a fast PF and a slow PF is experimentally observed, which makes it possible to almost completely eliminate the cyclic component of instability by changing the control mode of rods of the control system.

Influence of photovoltaic support on lightning transient under direct lightning strike

• A new transient circuit model for calculating the transient response of PV support is developed. • The transient overvoltage caused by the mode of air-termination rod and lightning strike point are investigated. • The influences of additional leg, tile angle and equipotential bonding have been studied. • Four types of PV supports are chosen and their lightning transient responses under direct lightning strike are comprehensively investigated. Due to the large-scale installation of photovoltaic (PV) plants in open areas, PV plants is exposed to lightning strike at a high risk. The influence of PV support on lightning transient under direct lightning strike is investigated in this paper. Firstly, the PV support composed of multiple branches is classified into vertical conductor, horizontal conductor and oblique conductor. Their wave impedances are individually derived. Considering the air-termination rod and earthing system, four types of PV supports are chosen and their lightning transient responses under direct lightning strike are comprehensively studied. It suggests that the transient response is heavily dependent on the number of grounding legs. The greater the grounding legs, the lower the overvoltage. The equipotential bonding provides additional routes for the discharge of lightning current. Its presence would minimize the voltage but increase the risk for the entire PV system. The additional auxiliary leg also plays a role. The non-isolated air-termination rod is suggested install at the symmetrical center of the PV support from the perspective of discharging the lightning current.

Spectrally Selective Optical Loss in Fibers With High-Index Rods Embedded Into Silica Cladding

In this work, we perform a detailed study of a novel type of optical fiber for spectral filtering, which is based on a step-index core with high-index rods embedded into silica cladding. Recently, it was theoretically predicted that such a structure could demonstrate a very sharp stopband due to the resonant core mode interaction with the eigen high-index rod mode. In the current paper, we realize the proposed structure and experimentally confirm its applicability for spectral filtering. In our experiments, we show the possibility of creating a very sharp shortpass fiber spectral filter. In particular, we demonstrate a change in the optical loss of the core mode by two orders of magnitude (from less than 0.1 dB/m to more than 10 dB/m) for a 12 nm wavelength shift (from 1008 nm to 1020 nm) and by more than 3 orders of magnitude (from 0.02 dB/m to 60 dB/m) for a 70 nm wavelength shift (from 980 to 1050 nm). Possible applications of the realized fiber design are discussed. Mechanisms of optical loss in the fabricated structure are studied, and the presence of an additional mechanism, which is not related to absorption in the high-index rods, is revealed.

Interface Static Friction Enabled Ultra‐Durable and High Output Sliding Mode Triboelectric Nanogenerator

AbstractUtilizing the static friction of the rolling rod/ball is an effective strategy to address the mechanical durability in sliding mode triboelectric nanogenerators (TENGs), but its line/point contact seriously reduces the output performance. Herein, a high output and ultra‐durable TENG is achieved by a rolling belt method. Compared with the previous rolling rod mode TENG (R‐TENG), the electric output performance of the rolling belt mode TENG (RB‐TENG) increases nearly 3.8 times. The maximum output power density of RB‐TENG reaches ≈280 W m‐2 with self‐charge excitation and power management, and its charge density is the highest among all sliding mode TENGs without sliding friction including rolling rod/ball mode and noncontact freestanding mode. Furthermore, the RB‐TENG remains nearly 98.5% of its output performance after more than 4 100 000 cycles, which is the highest stability measured in such a long time by now, with material abrasion quality 6.42 µg·g‐1 (<1% of traditional sliding TENG) every 10 000 cycles. This work provides an effective strategy for solving the bottleneck issues of mechanical abrasion in sliding mode TENGs.

Ultrahigh-sensitivity temperature sensor based on resonance coupling in liquid-infiltrated side-hole microstructured optical fibers

A compact fiber-optic temperature sensor based on refractive index liquid (RIL) functionalized side-hole microstructured optical fibers (SHMOFs) is proposed and experimentally demonstrated. Transmission spectral characteristics of the proposed temperature sensor have been investigated from experimental as well as theoretical perspectives. Due to the resonance coupling between the fundamental core mode and RIL rod modes, multiple resonance dips are present in the transmission spectrum, which could be tuned by adjusting environmental temperature. Experimental results indicate that the highest temperature sensitivity reaches − 13.1 nm/°C for a temperature range of 80–100 °C. Hence, the SHMOF-based temperature sensor has several desirable merits such as ultrahigh sensitivity, wide measurement range and ease of fabrication, which make it a promising candidate for various applications in environmental monitoring, industrial and agricultural production.

Effect of fiber hybrid mode on the tension–tension fatigue performance for the pultruded carbon/glass fiber reinforced polymer composite rod

In order to promote the application of fiber reinforced polymer (FRP) rod in bridge engineering, the carbon/glass fiber uniformly dispersed hybrid (UDH) rod with a diameter of 22 mm was developed as the bridge cable through the pultrusion technology. In the present paper, the tension–tension fatigue performances of hybrid rod were investigated with three stress levels of 0.33, 0.44, 0.60 and the fixed stress ratio of 0.4. The fatigue life, stiffness degradation and stress redistribution during the fatigue loading were obtained by linear variable differential transformer (LVDT) and digital image correlation (DIC) method. Furthermore, the fatigue failure mechanism was revealed by microstructure damage analysis. Through the fiber uniformly hybrid technology, the fatigue failure mode of hybrid rod transferred from shell-core debonding to uniformly carbon and glass fiber/resin interface splitting. The positive hybrid effect of fatigue performance was realized to obtain higher fatigue life, stiffness retention and residual mechanical properties. The reliable fatigue life prediction model was developed, and the recommended fatigue limit of present hybrid rod applied for bridge cable was 0.45 at the stress ratio of 0.4 to obtain more than two million fatigue cycles.

BEHAVIORS OF OXIDATION AND DECARBURIZATION ON SURFACE OF HIGH-CARBON STEEL WIRE RODS

The quality of high-carbon wire rods is subject to high requirements in terms of the size of the decarbonized layer, the amount and composition of the scale formed by the interaction of the oxidizing furnace atmosphere with the surface of steel. In this connection, studies of the kinetics of high-temperature oxidation of high-carbon steel are of great practical importance, both in the development of new and adjustment of existing modes of heat treatment of steel. The results of experimental studies of hightemperature oxidation and decarburization of the surface of high-carbon steel grade 80P on the synchronous thermal analysis device STA 449 F3 Jupiter presented. Temperature intervals of intensification of scale formation and decarburization of the surface in various media (weakly oxidizing and oxidizing) have been established. Phase transformations in high-carbon steel grade 80P have been studied by differential scanning calorimetry and the temperatures of the beginning and end of the formation of homogeneous austenite during heating have been established. It was noted that in the range of heating temperatures of steel 720‒950°C, along with phase transformations, the intensification of the processes of scale formation and depletion of the surface layers with carbon begins. The exponential dependence of steel loss on the heating temperature of the sample was obtained by thermogravimetric analysis. It was shown that the oxidation rate of the surface increases by 3 times with an increase in the temperature of the workpiece from 900 to 1000°C, and up to 1200°C ‒ by 8 times. It was noted that the temperature at which the oxidation rate of steel is minimal in the temperature range from 900 to 1000 °C is about 929 °C, in the range of 1100‒1250°C ‒ 1157°C. The obtained results can be used to select the main technological parameters of the heat treatment mode of wire rods made of 80P steel, which ensure the formation of a minimum amount of easily removed scale on the metal surface.

Development of high intensity multibeam laser metal deposition system with blue diode lasers for additively manufacturing of copper rod

A 100 W blue diode laser with an optical fiber having a core diameter of 100 μm was developed and installed into a blue diode laser metal deposition system (B-LMD), achieving a laser intensity of 7.58 × 104 W/cm2, four times higher than that of the previous B-LMD system. The increase in laser intensity is expected to enable faster and more efficient 3D processing of pure copper. The authors conducted the rod formation experiment by varying the processing speed. The rod formation process is observed with a high-speed video camera to clarify the mechanism of copper rod formation. As a result of rod formation as a 3D modeling of pure copper, a 30 mm rod was formed in 1.5 s under the following conditions: a laser intensity of 1.27×106W/cm2, a powder feed rate of 220 mg/s, and a processing speed of 20 mm/s. It was found that the mode of rod forming changed depending on the processing speed. When the processing speed is high, the mode becomes molten layer type and the energy efficiency becomes high. In addition, the processing point became closer to the focal point at high speed, and the cross-sectional shape of the formed rod was closer to the circular ones.

Tunable Plasmon-Induced-Transparency Effect in a Simple Planar Composite Structure

A planar metamaterial structure has been designed to obtain surface plasmon-induced-transparency (PIT) effect, which is composed of a nanodisk sandwiched between double rods. From theoretical perspective, the three-level plasmonic system has been utilized to analyze the near-field coupling mechanism. Besides, the simulation results show that PIT resonance can be tailored by structure parameters. Particularly, when the length of the rods is more than twice of the diameter of the disk, two PIT windows are generated simultaneously, based on the coupling between the bright mode of the nanodisk and two multipole dark modes of rods. Furthermore, a metamaterial structure, composed by a disk and two pairs of nanorods, is suggested to achieve the polarization-independent plasmon-induced-transparency effect. As a result, this work shows great application prospect in the area of compact optical devices, such as multiband tunable filters, plasmonic switches, and slow light devices.

Experimental investigation and modeling of temperature-dependent flexural strength of hybrid composite rods

The flexural behavior of hybrid composite rods used in high capacity low sag overhead conductors at elevated temperatures is experimentally investigated. Dynamic mechanical analysis (DMA) is carried out on pultruded carbon/glass/epoxy specimens, followed by three-point bending experiments at different elevated temperatures. The failure mechanisms are examined by using macro/micro images taken from the failed specimens. The results show that flexural properties such as strength and modulus decrease as temperature increases. The failure mode of hybrid composite rods is also found highly temperature-dependent. A new simple model is developed based on DMA data to predict the flexural strength of high-performance polymeric composites at different temperatures. The predictions are in good agreement with the experimental data.

Investigation of the Structure and Properties of Deformed Semi-Finished Products from Alloys of the Al-REM System Made by the Method of Ingotless Rolling-Extruding

The article presents the investigation results of the structure and properties of rods of aluminum alloys containing zirconium, cerium and lanthanum after ingotless rolling-extruding (IRE) and heat treatment. The patterns of changes in the microstructure, mechanical properties, electrical resistivity depending on the chemical composition of the alloys, processed by the IRE method and various modes of rods annealing are shown. A metallographic analysis of the grain structure of the samples in a deformed state and after annealing performed. The temperatures at which the alloy structure remains stable and maintains the level of operational properties revealed. The effect of chemical composition on the heat resistance of deformed semi-finished products represented. The study made it possible to evaluate the level of properties of experimental alloys after processing by the method of ingotless rolling-extruding and various modes of rods annealing.