Buffer Rod Research Articles

Online ultrasonic monitoring of FDM nozzle temperature based on metamaterial buffer rod

Abstract Fused deposition modeling (FDM) has been widely used for fabricating parts with complex geometries. However, during the printing process the nozzle temperature fluctuates which may cause nozzle blockage, inter-filament delamination, over-melting, etc. Therefore, it is of significance to develop an online and in-situ nozzle monitoring system which could overcome such drawbacks for quality assurance. In this work, a multifunctional system is designed by incorporating a traditional ultrasonic probe and a metamaterial buffer rod to online monitor the nozzle temperature and ensure a correct extrusion force and speed. A parametric simulation model is first constructed implicitly based on thermal-acoustic metamaterial structures for the buffer rod. Secondly, since the high-fidelity calculation is computationally expensive, an efficient surrogate model with kriging approach is constructed based on the dataset drawn from limited trials for rapid prediction. Thirdly, multidisciplinary optimization is performed by the NSGA-III algorithm considering the thermal insulation performance, ultrasonic attenuation and structure integrity. The rod is fabricated according to the best parameters decided. A cross-correlation algorithm is calibrated with thermocouple measurement after waveform recording at different temperatures. The online and in-situ temperature measurement can be realized during 3D printing successfully eventually. This will help to improve the printing quality with potential feedback strategies.

Water content monitoring in water-in-oil emulsions using a delay line cell

The extraction process of crude oil requires addition of water, resulting in complex emulsions, in which the phases must be separated before the petrochemical processing starts. An ultrasonic cell may be used to determine in real time the water content in water-in-crude oil emulsions. The water content of emulsions can be related to parameters, such as propagation velocity, density and relative attenuation. The ultrasonic measurement cell developed here is composed of two piezoelectric transducers, two rexolite buffer rods, and a sample chamber. It is an inexpensive and robust system. The cell measures the parameters at different temperatures and flow conditions. The tests were performed using emulsions with water volume concentrations from 0% to 40%. The experimental results show that this cell is able to obtain more precise parameters, when compared to similar ultrasonic techniques. The data acquired in real time may be used to improve the emulsion separation, decreasing greenhouse gases and energy requirements.

High-temperature elastic moduli: A tool for understanding chemical bonding in thermoelectric materials

In the study of thermoelectric materials, the elastic moduli are valuable for predicting and interpreting trends in lattice thermal conductivity and some aspects of electronic conductivity (e.g., electron-phonon interactions). Because elastic moduli are highly sensitive to the details of chemical bonding, they can also be used to detect subtle changes in crystal symmetry or site-disorder due to phase transitions. Consequently, measurements of elastic moduli are of fundamental value in the development of structure-property relationships in thermoelectric materials. However, experimental reports of the elastic constants of functional materials are relatively sparse, and temperature-dependent data is even less common. Further, unlike most types of functional materials, thermoelectric materials are used over an extremely wide temperature range (up to 1300 K in some cases). In our lab, we measure the elastic constants of polycrystalline and single crystalline thermoelectric materials across a wide temperature range (250–1300 K) using resonant ultrasound spectroscopy with Al2O3 buffer rods to separate the transducers from the hot zone. In this talk, I will discuss the high-temperature elastic properties of several classes of thermoelectric materials, including Mg3Sb2 and GeSe-AgBiSe2 alloys, emphasizing the role that such data can play in interpreting composition- and temperature-dependent trends in lattice thermal conductivity.

Stability analysis of Mars soft landing under uncertain landing conditions and two landing strategies

PurposeThe purpose of this paper is to study the landing performance of the Mars lander considering uncertain landing conditions under two landing modes.Design/methodology/approachA dynamics analysis model for the legged Mars lander is established for landing simulation, where the nonlinear large-deformation flexible buffer rods are equivalently modeled with a rigid-body mechanism with external forces and movement limit. Sensitivities of the landing stability to various landing conditions are analyzed using the Quasi–Monte-Carlo-based Sobol’ method and computer-aided landing simulations. Moreover, based on the results of sensitivity analysis, sensitive parameters are selected for estimating the safe boundaries for stability indices of rotation and clearance.FindingsIt can be concluded from this study that the lander has excellent ability against overturning. The shutdown-before-touchdown strategy helps to maintain than landing pose, and the shutdown-at-touchdown strategy helps to prevent the nozzle from colliding with the surface of Mars.Practical implicationsThis study provides a theoretical reference to choose the better landing strategies for Mars landers considering uncertain landing conditions.Originality/valueA parameterized dynamics Mars lander model and a simplification method are proposed to simulate the landing on Mars. Uncertain landing conditions are parameterized and considered in the dynamics model. Sensitivity analysis and safe boundary methods are used to compare the landing performances with two landing strategies.

In-situ ultrasonic calibrations of pressure and temperature in a hinge-type double-stage cubic large volume press

Here, simultaneous in-situ calibration of pressures and temperatures was performed in a hinge-type second-stage cubic large volume press (LVP) up to 15 GPa and 1400 K by an acoustic travel-time approach. Based on the recently reported P–t S and P–T–t P–t S equations for Al2O3 buffer rod, the cell pressures and temperatures in the chamber of LVP were in-situ determined, in comparison with those by conventional off-line (or fixed-points) pressure calibration method and direct thermocouple measurement, respectively. It is found that the cell pressures of the LVP chamber are significantly reduced after annealing at simultaneous high pressures and high temperatures, owing to the stress relaxation as accumulate in the LVP chamber. This acoustic travel-time method is verified to be a good way for precise determination of thermal (cell) pressures at high temperature conditions, and is of great importance and necessity to conduct in-situ physical property measurements under extreme high P–T conditions, especially when the precious synchrotron x-ray/neutron diffraction beams are not available.

A method for simultaneous measurements of compressional wave and shear wave velocities in rocks and minerals at high pressure and high temperature: A modification to the combined transmission-reflection method

We present a modification to the combined transmission-reflection method, which is frequently used to measure the elastic wave velocities in rocks and minerals at high pressure and high temperature in multi-anvil apparatus. The modification mainly focuses on the adoption of dual-mode ultrasonic transducer and new backing reflector (a molybdenum foil), the former was used to simultaneously measure the travel times of compressional wave and shear wave in the sample, and the latter was used to intensify the reflection signals of the buffer rod. The correction time of the molybdenum foils was determined using the equation of state and highpressure velocities of molybdenum. In addition, the length change of sample under high pressure was also taken into account. Using this method, we simultaneously measured the compressional wave and shear wave velocities in Z-cut a-quartz single crystal to 2 GPa at room temperature, and natural mafic granulite sample to 1.4 GPa and 500�C in a multianvil apparatus. The results of this work agree well with those of previous measurements and demonstrate the feasibility of this new method. We believe that by using this method, more accurate elastic properties of rocks and minerals under high pressure and high temperature can be obtained, especially Poisson�s ratio.

3Pb2-3 Designing Tapered Buffer Rod with Small End for Ultrasonic Pulse Echo Measurements

3Pb2-3 Designing Tapered Buffer Rod with Small End for Ultrasonic Pulse Echo Measurements

On-Line Monitoring of Pipe Wall Thinning by a High Temperature Ultrasonic Waveguide System at the Flow Accelerated Corrosion Proof Facility.

Pipe wall thinning and leakage due to flow accelerated corrosion (FAC) are important safety concerns for nuclear power plants. A shear horizontal ultrasonic pitch/catch technique was developed for the accurate monitoring of the pipe wall-thickness. A solid couplant should be used to ensure high quality ultrasonic signals for a long operation time at an elevated temperature. We developed a high temperature ultrasonic thickness monitoring method using a pair of shear horizontal transducers and waveguide strips. A computer program for on-line monitoring of the pipe thickness at high temperature was also developed. Both a conventional buffer rod pulse-echo type and a developed shear horizontal ultrasonic waveguide type for a high temperature thickness monitoring system were successfully installed to test a section of the FAC proof test facility. The overall measurement error was estimated as ±15 μm during a cycle ranging from room temperature to 150 °C. The developed waveguide system was stable for about 3300 h and sensitive to changes in the internal flow velocity. This system can be used for high temperature thickness monitoring in all industries as well as nuclear power plants.

Sound velocities of the 23 Å phase at high pressure and implications for seismic velocities in subducted slabs

Dense hydrous magnesium silicates (DHMS) are believed to play an important role in transporting water back into the deep interior of the Earth. Recently, a new Al-bearing hydrous Mg-silicate, named the 23 Å phase [ideal composition Mg12Al2Si4O16(OH)14], was reported (Cai et al., 2015), which could be another important hydrous phase in subducting slabs. In this paper, we report new measurements of the compressional (P) and shear (S) wave velocities of the 23 Å phase under pressures up to 14 GPa at room temperature, using a bulk sample with a grain size of less than 20 μm and density of 2.947 g/cm3. The acoustic measurements were conducted in a 1000-ton uniaxial split-cylinder multi-anvil apparatus using ultrasonic interferometric techniques (Li et al., 1996). The pressures were determined in situ by using an alumina buffer rod as the pressure marker (Wang et al., 2015). A dual-mode piezoelectric transducer enabled us to measure P and S wave travel times simultaneously, which in turn allowed a precise determination of the sound velocities and elastic bulk (KS) and shear (G) moduli at high pressures. The velocities of this 23 Å phase (ambient VP = 7.53 km/s, VS = 3.72 km/s) are lower than those of phase A, olivine, pyrope, etc. (especially for S waves), yet the VP/VS ratio (from 2.02 to 1.94, decreasing with increasing pressure) is much higher compared to those mantle minerals (1.7–1.8). A fit to the acoustic data using finite strain analysis combined with the Hashin-Shtrikman (HS) averaging scheme yields: KS0 = 111.4(6) GPa, G0 = 41.0(2) GPa, and KS′ = 3.6, G′ = 1.8 for the bulk and shear moduli and their pressure derivatives. Using these data, the density and velocity profiles of the hydrous harzburgite and lherzolite were calculated along a warm slab P-T condition. The results suggest that a hydrous pyrolitic assemblage containing 23 Å phase should be distinguishable from a dry assemblage at the high pressure and temperature conditions relevant to Al-bearing subducted slabs.

An ultrafast broadband digital signal processing approach to pulse echo measurements

Pulse-Echo (PE) measurements are commonly used to determine the sound velocity in a sample of known length. In PE measurements, the interface between the transducer and buffer rod, and that between the buffer rod and sample, introduces a total phase shift, Φ, to the acoustic wave that must be accounted for if high accuracy in the velocity is desired. The appropriate time correction, τ=Φ/ω, is traditionally determined by measuring the time-of-flight of multiple acoustic waves with different angular frequencies, ω. A single PE measurement can take several minutes, depending on experimental details such as the number of frequencies measured and the amount of signal averaging performed. Several minutes of data acquisition is tolerable for static experiments, but it is too long for many dynamic processes of interest in biology, pulsed magnetic fields, or any other rapidly changing system. This work describes an approach to PE in which a single broadband signal is collected and later processed offline using standard digital signal processing techniques. We demonstrate that a single captured waveform can be processed to yield the same information as 80 separate waveforms collected over an 80 MHz span, enabling accurate PE measurements on sub-second time scales.

Design and implementation of an ultrasonic sensor for rapid monitoring of industrial malolactic fermentation of wines

ABSTRACTUltrasound is an emerging technology that can be applied to monitor food processes. However, ultrasonic techniques are usually limited to research activities within a laboratory environment and they are not extensively used in industrial processes. The aim of this paper is to describe a novel ultrasonic sensor designed to monitor physical–chemical changes that occur in wines stored in industrial tanks. Essentially, the sensor consists of an ultrasonic transducer in contact with a buffer rod, mounted inside a stainless steel tube section. This structure allows the ultrasonic sensor to be directly installed in stainless steel tanks of an industrial plant. The operating principle of this design is based on the measurement of ultrasonic velocity of propagation. To test its proper operation, the sensor has been used to measure changes of concentration in aqueous samples and to monitor the progress of a malolactic fermentation of red wines in various commercial wineries. Results show the feasibility of using this sensor for monitoring malolactic fermentations in red wines placed in industrial tanks.

High Performance Ultrasonic Buffer Rods With Novel Structure for Polymer Process Monitoring

Abstract To reduce trailing noises mixed in ultrasonic echoes during ultrasonic wave propagation in a buffer rod, the influence of the rod’s boundary shape and dimension on the signal-to-noise ratio (SNR) was analyzed using a simulation method. Novel buffer rods with complex structures and shapes based on a cylinder or cone reference surface were proposed. The novel rods were found to be more effective in obtaining signals with high SNR than the cylinder or cone rods currently in use. Simulation results showed that the rod proposed in this paper exhibited better performance in a given installation space compared with the cylinder or cone rods.

High-temperature ultrasonic thickness monitoring for pipe thinning in a flow-accelerated corrosion proof test facility

Abstract In order to monitor the pipe thinning caused by flow-accelerated corrosion (FAC) that occurs in coolant piping systems, a shear horizontal ultrasonic pitch-catch waveguide technique was developed for accurate pipe wall thickness monitoring. A clamping device for dry coupling contact between the end of the waveguide and pipe surface was designed and fabricated. A computer program for multi-channel on-line monitoring of the pipe thickness at high temperature was also developed. Both a four-channel buffer rod pulse-echo type and a shear horizontal ultrasonic waveguide type for high-temperature thickness monitoring system were successfully installed to the test section of the FAC proof test facility. The overall measurement error can be estimated as ± 10 μm during a cycle from room temperature to 200°C.

원전 2차계통수 모사 환경에서 용접배관 감육 특성에 미치는 재료 및 유속의 영향

The pipelines and equipments are degraded by flow-accelerated corrosion (FAC), and a large-scale test facility was constructed for simulate the FAC phenomena in secondary coolant environment of PWR type nuclear power plants. Using this facility, FAC test was performed on weld pipe (carbon steel and low alloy steel) at the conditions of high velocity flow (> 10 m/s). Wall thickness was measured by high temperature ultrasonic monitoring systems (four-channel buffer rod type and waveguide type) during test period and room temperature manual ultrasonic method before and after test period. This work deals with the complex effects of flow velocity on the wall thinning in weld pipe and the test results showed that the higher flow velocity induced different increasement of wall thinning rate for the carbon steel and low alloy steel pipe.

Effect of Boundary Shape on Performance of the Ultrasonic Buffer Rod Without Clad

Boundary shape is one of the important factors that affects the performance of ultrasonic buffer rods. To provide unclad buffer rods for some certain cases, the paper investigates the effect of the rod outline shape on the signal-to-noise ratio (SNR) of ultrasonic signals based on the models built with Wave 2500, and found that the rods with an outline of a steep gradient play a very important role in eliminating the trailing noise. By only improving the rod's outline, the SNR of ultrasonic signals could be enhanced greatly.

超音波バッファロッドを用いた溶融プラスチックの評価に関する基礎的検討

超音波バッファロッドを用いた溶融プラスチックの評価に関する基礎的検討

Application of ultrasonic Doppler velocimetry to molten glass by using broadband phase difference method

An ultrasonic velocity profile (UVP) measurement in high temperature molten glass was presented using buffer rod technique. A ceramic buffer rod was used to transmit ultrasound into molten glass. The rod had a taper shape and porous cladding to suppress trailing echo, which is the spurious echo in the buffer rod measurement. The broadband signal processing method was presented to improve noise tolerance in velocity estimation. This method is based on the phase difference method, which is originally proposed as a narrowband method. Measurable distance of the UVP measurement was investigated combining the buffer rod and the broadband signal processing method. Experiment was conducted at the temperature from 1000°C to 1200°C. As a preliminary test, motion tracking in molten glass was successfully demonstrated.

Influence of temperature on ultrasound absorption in waveguides made out of refractory materials

We studied the influence of temperature increase to 1500°C on ultrasound absorption at frequencies from 0.1 to 1.0MHz in tungsten, molybdenum, vanadium, graphite, and fused silica. The ultrasound absorption coefficient in these materials was calculated. It was shown that the fused silica has the smallest ultrasound absorption coefficient for temperatures up to 1000°C. Vanadium and graphite also have small values of this coefficient for the considered temperature. The ultrasound absorption was investigated experimentally in graphite and fused silica waveguides. We demonstrated that the ultrasound absorption did not change in graphite with the temperature increase, but it increased in fused silica by a factor 2 for the temperature above 1000°C. We show that different acoustical and mechanical properties of vanadium, graphite, and fused silica allow using them for waveguide applications and buffer rods in crystal growth at temperatures below 1500°C and ultrasound frequency below 1.0MHz.

Development of the ultrasonic buffer rod for the molten glass measurement

Design and demonstration of an ultrasonic buffer rod for high temperature fluid especially for the molten glass were studied. Material selection guide for glass melts was established focusing on high temperature strength, attenuation and acoustic impedance. Durability and wettability of ultrasonic buffer rod have been tested for several materials. Frequency of the ultrasound was chosen considering the transmission characteristic of the buffer rod which was investigated employing three dimensional FEM code. The buffer rod tested has tapered shape and cladding on the side wall as a further suppression of trailing echo. Sound velocity and attenuation coefficient measurements in a temperature range of 1000–1200 °C were then demonstrated utilizing the designed buffer rod. Signal processing technique to eliminate remained trailing echoes was also performed. Applicability of the ultrasonic measurement using the buffer rod is discussed.

Development of Polygonal Buffer Rods for Ultrasonic Pulse-Echo Measurements

In ultrasonic pulse-echo measurement with a long buffer rod (waveguide), it is required to prevent the generation of spurious echoes (often called trailing echoes) accompanying with a main echo in the buffer rod. In this work, new method to prevent such trailing echoes in the rod is proposed and the effectiveness of the method has been demonstrated experimentally and numerically. In the method the cross-sectional shape of the rod perpendicular to the axial direction is a polygon having sides any one of which is not parallel to any of the other sides, so that trailing echoes are hardly generated during the propagation of pulsed ultrasonic wave in the rod. Three-dimensional numerical simulations based on a finite different method are performed to examine the behaviours of ultrasonic pulse-echoes including trailing echoes for several types of buffer rods having different cross-sectional shapes such as a circle, triangle, square, pentagon, hexagon and heptagon. Based on the results, experiments with several buffer rods are carried out at frequency 5 MHz. It has been found that heptagon may be the suitable shape for effectively eliminating trailing echoes and improving the signal-to-noise ratio of the measured pulse-echo.