Dynamic Test Method Research Articles

DETERMINATION OF THE DYNAMIC MODULUS OF LINEAR DEFORMATIONS OF REINFORCED HIGHLY FILLED POLYMER CONCRETE COMPOSITES DURING CURING

The objects of this study are reinforced polymer concrete composites with epoxy matrix and mineral dispersion fillers. Dynamic modulus of linear deformations has been measured according the standardized dynamic testing method ASTM E1876 - 02. The quantitative values of the modulus are obtained by the action of longitudinal and bending. After statistical processing of the obtained results has been established the influence of fiber in the composition on the dynamic characteristic.

The Exothermic Effects of Textile Fibers during Changes in Environmental Humidity: A Comparison between ISO:16533 and Dynamic Hot Plate Test Method

The exothermic effects of high regain fiber types have been described before; yet, there have not been reliable tests to demonstrate these effects on the human body. Most test methods focus on steady-state measurements; therefore, these exothermic effects during changes in environmental humidity are typically not analyzed or quantified. We have conducted a set of fabric tests that shows the connection between the exothermic effect of water vapor uptake and its consequence for heat loss through the fabric in transient conditions. We have performed the ISO:16533 standard test, a dynamic hot plate test developed by Naylor to measure the exothermic property of the fabric, and dynamic regain tests to connect the dots between these tests and the water vapor uptake phenomenon. Although the ISO:16533 test method tends to show the temperature increase in fibers, it cannot differentiate between the hygroscopic fiber (wool, viscose, cotton) types (p > 0.001). In addition, sensor size and sample folding techniques could impact the temperature increase. On the other hand, the Naylor hot plate test showed a greater difference in heat release among the fiber types (wool showed 20% higher heat release than viscose, 50% more than cotton), although the relative humidity changes in the chamber take time, which might not reflect a step-wise change in humidity. So far, these test methods have proven to be the most reliable for determining the exothermic behavior of textile fiber. However, these test methods still have limitations and cannot simulate realistic environmental conditions considering an instantaneous change in the environment. This paper reflects the comparison between the two test methods and recommends directions to accurately address the theory of water vapor uptake under dynamic conditions.

Analysis of heat exchanger corrosion failure in 800,000 light hydrocarbon plant in Liaohe Oilfield

Heat exchangers, as the major equipment for forced heat exchange, are now widely utilized in all areas of life, however in real usage, corrosion failure can frequently occur and cause catastrophic mishaps. In this study, the composition of the corrosion products in the heat exchanger's head section was examined using XRF and XRD, and the corrosion of Q345D steel in the head section was examined using the dynamic potential polarization curve test method in conjunction with SEM under various CO2 and O2 partial pressure and temperature conditions. Fluent simulation software was also used to simulate the impact of erosion corrosion on the heat exchanger's head section. Results indicate that the main corrosion products in the regenerative heat exchanger E-303 are Fe3O4, with minor amounts of Fe2O3 and FeOOH; in terms of temperature, CO2 and O2, these three influencing factors on the heat exchanger head Q345D steel corrosion results, the temperature on the steel corrosion damage is significantly greater than the local corrosion caused by CO2 and O2, but when the temperature is higher than the solution boiling point of its corrosion in and out will occur. The flow rate scouring on the heat exchanger head high temperature inlet that is caused by the damage is much greater than the head low temperature outlet, corrosion damage is primarily concentrated in the lower inlet baffle, which is also consistent with the actual conditions of the site heat exchanger.

Comparison of RSW technologies on DP steels with modified instrumented Charpy impact test

In recent decades the toughness of welded structures becomes more and more important. This trend is particularly valid for the advanced high-strength steels (AHSS), which have reduced toughness comparing to the low-strength structural steels. Dynamic characteristics of the welded joints of the newly developed high-strength steel sheets required by the automotive industry have been neglected, with welding procedures being optimized on the static joint properties, mainly on the tensile-shear force. Up to the present time, testing of dynamic properties of the spot-welded joints has been performed by increased testing speed during tensile testing. The authors have developed a new dynamic testing method and designed new testing equipment for impact bending, which can give a numeric result to characterize the resistance of spot-welded joints against dynamic load. In this paper, this method will be used to evaluate resistance spot-welded joints made on DP600 and DP800 steels with three different technological parameters, comparing long-time welding, short-time welding, and two-pulse welding. The different parameters cause different weld nugget sizes, failure modes, impact energies, and force–time diagrams. All test results show that bigger weld nugget diameters cause better impact energies and impact forces, but the differences are not perfectly correlated.

Improved Operator-Splitting Method for Dynamic Real-Time Substructure Testing of Multiple-Degree-of-Freedom Structure

The operator-splitting (OS) method for real-time substructure testing (RTST) provides explicit and unconditionally stable solutions for structures with softening type stiffness and damping has been widely used for precisely disclosing the seismic performance of structures with velocity-dependent specimens. However, the OS method for RTST provides only explicit target displacement and velocity but not an explicit target acceleration, so that it is essentially an implicit method for Dynamic real-time substructure testing (DRTST) with dynamic system specimens. For precisely disclosing the seismic performance of multiple-degree-of-freedom structures with dynamic system specimens, one improved OS method is proposed for DRTST in this paper. The methodology and stability of the proposed OS method are investigated, and the effectiveness of the proposed OS method is validated by numerical simulations and experimental tests. By using the predictor displacement, velocity, and acceleration approximations, the OS method is an explicit algorithm for DRTST. The stability analysis shows that the proposed OS method is conditionally stable for DRTST, and its stability limit decreases with the increase of the mass ratio and the stiffness ratio, while it increases first and then decreases with the increase of the damping ratio. The numerical and experimental results confirm the stability and accuracy of the OS method. The OS method for DRTST provides a practical and precise investigation strategy for structures with dynamic system specimens and may have broad application prospects in civil engineering.

Effect of Various Dynamic Shear Rheometer Testing Methods on the Measured Rheological Properties of Bitumen

A 23 factorial design experiment was conducted to study the influence of pre-heating temperature (HT) for manufacturing sample, bonding temperature (BT) onto rheometer, and trimming state (Trim) of the sample on complex shear modulus (G*) and phase angle (δ) using a dynamic shear rheometer on unmodified bitumen of types 50/70, 70/100, and two 160/220 from various sources. In addition, the black diagram and 2S2P1D model were used to evaluate the viscoelastic properties of bitumens. Findings show that the G* is more sensitive to the changes than the δ. Additionally, it was found that the 8 mm parallel plate diameter had a higher sensitivity to the trimming state than the 25 mm. The tested factor HT generally did not have a statistically significant impact on the results of the tested materials, except for 160/220_I. At practically all the temperatures tested for 50/70 and 160/220_II, the G* dropped by increasing the factor BT from a lower to a higher value. The Trim:BT interaction has the greatest impact on all materials and temperatures on G*, except for 160/220 at lower temperatures. However, in the case of δ, the Trim:BT interaction has the most significant effects for 70/100 and 160/220_II. The black diagrams show no discernible differences, which may be a result of the limited range of changes made to the variables.

Seismic response evaluation of spring-based piston braced frames by employing closed-loop dynamic (CLD) testing

This paper employs the Closed-Loop Dynamic (CLD) testing method for evaluating the seismic response of Spring-Based Piston Braced Frames (SBPBF) by utilizing a combination of experimental and numerical approaches. The CLD testing procedure is an iterative process, which is initiated by conducting cyclic tests on a reduced-scale bracing element and followed by computational simulations of a full-scale braced frame. To this end, a hysteresis model is developed, based on testing the Spring-Based Piston Bracing (SBPB) element, which is incorporated into a simulated multi-story SBPBF. The time-dependent deformations of SBPBs under earthquake loadings are scaled down using similitude law, serving as a loading protocol for further testing and refining the hysteresis model. The developed model is then calibrated, scaled up, and integrated into the computational model to generate more precise deformation histories of the SBPB. The refined model is validated through aniterative process that combines experimental and numerical results. An illustrative example is presented to demonstrate the feasibility of the CLD testing method for SBPB archetypes. The efficiency of this approach is demonstrated by the remarkable match between the experimental and computational results. Additionally, a comparative numerical assessment is conducted on braced frames equipped with non-compressed and pre-compressed SBPBs, revealing their superior performance compared to the Buckling-Restrained Braced Frames (BRBFs).

Effect of time step interval and time integration schemes in Pseudo-Dynamic analysis

Pseudo Dynamic Analysis technique is an alternative method for exploring structural performance by combining analytical and experimental investigation. Compared to shake table tests, it is a more economical method, and its reliability has been proven over many years of the studies. The damage occurrence and process can be monitored on the test sample due to experiments performed at low speeds. In this study, the behaviour of a single degree of freedom, cantilever column system, under the effect of the pulse load and earthquake record was investigated both numerically and experimentally using Pseudo Dynamic Analysis method. The effects of two different time integration schemes and various time step interval values on analyses were examined in the investigations and the results were compared. Numerical analyses were performed by α-operator splitting method and central differences method, and experimental studies were performed by α-operator splitting method. In experimental investigations, approximate results were obtained with numerical studies for certain values of the time step. At small time interval values, experimental results deteriorated. It is purposed to determine the optimum time step interval value that can be utilised in the Pseudo Dynamic Test method.

Experimental Study on Silt Soil Improved by Microbial Solidification with the Use of Lignin.

At present, in the field of geotechnical engineering and agricultural production, with increasingly serious pollution an environmentally friendly and efficient means is urgently needed to improve the soil mass. This paper mainly studied the microbial induced calcium carbonate precipitation (MICP) technology and the combined effect of MICP technology and lignin on the improvement of silt in the Beijing area. Through unconfined compressive strength and dynamic triaxial test methods, samples improved by microorganisms were studied to obtain the optimal values of cement concentration and lignin under these two test schemes. The results show that after the incubation time of Sporosarcina pasteurii reached 24 h, the OD600 value was 1.7-2.0 and the activity value (U) was 930-1000 mM ms/min. In the unconfined static pressure strength test, after MICP treatment the optimal concentration of cementitious solution for constant temperature and humidity samples and constant-temperature immersion samples was 1.25 mol/L. The compressive strength of the constant temperature and humidity sample was 1.73 MPa, and the compressive strength of the constant-temperature immersion sample was 3.62 Mpa. At the concentration of 1.25 mol/L of cement solution, MICP technology combined with lignin could improve the constant temperature and humidity silt sample. The optimal addition ratio of lignin was 4%, and its compressive strength was 1.9 MPa. The optimal lignin addition ratio of the sample soaked at a constant temperature was 3%, and the compressive strength was 4.84 MPa. In the dynamic triaxial multi-stage cyclic load test, the optimal concentration of cementation solution for the constant temperature and humidity sample after MICP treatment was 1.0 mol/L, and the failure was mainly inclined cracks. However, in the condition of joint improvement of MICP and lignin, the sample mainly had a drum-shaped deformation, the optimal lignin addition ratio was 4%, and the maximum axial load that the sample could bear was 306.08 N. When the axial dynamic load reached 300 N, the strain accumulation of the 4% group was only 2.3 mm. In this paper, lignin, an ecofriendly material, was introduced on the basis of MICP technology. According to the failure shape and relevant results of the sample, the addition of lignin was beneficial for the improvement of the compressive strength of the sample.

Real-time dynamic hybrid testing method for the dynamic characteristics of soil-structure interaction system

The radiation damping of the elastic half-space significantly affects the modal damping ratio of the superstructure. However, conventionally, it is hard for the traditional shaking table test to exhibit the radiation damping effect of the site due to the boundary effects of the model box. In this paper, a new impulsive-force-based real-time dynamic hybrid testing (RTDHT) method is developed to investigate the soil-structure interaction (SSI) effect on the structural dynamic characteristics. In the new method, the superstructure is considered to be a physical substructure and the semi-infinite soil deposits is as assumed to be a numerical substructure. The free vibration of the superstructure in the SSI system is excited by applying impulsive force at the interface of the soil and superstructure. Then, a time-domain method combining empirical wavelet transform and Hilbert transform is developed to identify structural modal parameters, which significantly improves the efficiency and accuracy of the experimental modal analysis for the shaking table test of the SSI system. A series of the RTDHT of a two-story steel frame structure on elastic half-space site is carried out, which validated the effectiveness and accuracy of the test method by comparisons between the experimental and numerical results.

REVIEW OF THE MECHANICAL PROPERTIES OF FIBER CONCRETE UNDER DANIAMIC TENSION AND COMPRESSION

This article is a review of the mechanical properties of fiber-reinforced concrete at high strain rates under tensile and compressive stresses. Fibre-reinforced concrete is widely used in the construction of protective structures, in tunnels, engineering structures in seismic areas, airport runways, river and marine engineering structures and is an important substitute for classic concrete. The review covers the following aspects: advantages and disadvantages of various test methods used to determine the dynamic properties of fiber-reinforced concrete; studies of the dynamic characteristics of fiber-reinforced concrete in compression and tension, including their strength, deformation capacity and ability to absorb energy. The purpose of this review is to expand fundamental knowledge about the dynamic properties of fiber-reinforced concrete and to promote further research on its physical and mechanical characteristics and applications for increasing the strength of brittle materials. At the beginning of the review, the most commonly used test setups and methods for dynamic testing are considered. The Kolsky method is most widely used to determine properties in dynamic compression, tension, and tensile splitting at high strain rates. Further, the main part of the review considers the mechanical properties of fiber-reinforced concrete under dynamic compression and tension, including strength, impact strength, and the ability to absorb energy. Studies have shown that with an increase in the rate of deformation, the dynamic strength of fiber-reinforced concrete increases. The use of an appropriate amount of fiber leads to a significant improvement in dynamic properties. However, there is a threshold fiber content. In conclusion, by summarizing and comparing previous studies, the advantages and disadvantages of existing studies are emphasized, and suggestions for further research are made.

About the choice of the test method to clarify the actual working scheme of the beam

This article discusses the problem of determining the actual scheme of a precast reinforced concrete frame of a building when performing engineering surveys. The method of connecting precast reinforced concrete structures in industrial buildings with heavy equipment plays an important role in assessing the stress state of building structures. It is not always possible to perform the opening of nodes in the conditions of existing production, since this requires stopping technological processes or dismantling equipment. The article discusses the possibilities of static and dynamic tests for the study of support units in precast reinforced concrete structures during engineering surveys. The possibilities of static and dynamic test methods are considered, as well as the advantages and disadvantages of these methods when evaluating support units in precast reinforced concrete structures of buildings and structures during surveys. As an example for the study, the case of determining the current structural scheme of a precast reinforced concrete floor using dynamic tests is considered. The article analyzes previous studies on the use of the dynamic method in determining the actual scheme of existing reinforced concrete structures of an industrial building. The results of theoretical studies and their comparison with experimental results are presented. The general conclusions based on the results of the study are formulated, and recommendations are given on the choice of a method of testing structures for cases of establishing a structural scheme of precast reinforced concrete crossbars in operated industrial buildings during survey work.

TESTING OF BRIDGES DAMAGED AS A RESULT OF COMBAT ACTIONS

The work examines the application of methods of static and dynamic testing of bridges damaged as a result of hostilities. Penetration by projectiles and damage by explosions of structural elements, in addition to obvious damage, also form a series of hidden defects, the determination of which according to norms and regulatory documents is regulated to be carried out by means of tests with calculated loads. For testing bridges in accordance with the requirements of construction standards and regulatory documents, the equipment developed by the author of the article was used for digital registration and processing of signals of acoustic emission and mechanical vibrations. The results of static tests of three span overpasses made of precast concrete with a length of 63.20 m along the street are presented. Kvitneva in the city of Chernihiv and a four-span pedestrian bridge with a length of 263.1 m across the Desna River in the park zone of the city of Chernihiv. The peculiarities of the application of the acoustic emission method for determining the state of the span structures of the bridge during static tests with step loading are considered. During the analysis of the results of the dynamic tests of the pedestrian bridge, the results of the application of wavelet analysis were translated to reveal the characteristics of the oscillations of a non-separable steel three-span structure that received dynamic load impulses and determine the natural frequency of oscillations of the span structures. The results of the work are recommended for use during the examination and testing of bridges, the girder structures of which have hidden defects and damage, as well as for constant monitoring of the structures.

Method and apparatus for dynamic testing of structural joints

The dynamic testing technique is used during the design phase of structures and series production. This test evaluates the structural capacity, especially of the assemblies, to withstand different forces and rates of impact encountered under realistic operational conditions. This study proposes a magnetic pulse exciter for high-speed impact loading in dynamic tests because of its capability to provide single and repeatable pulse loading over a wide range of force up to 20 kN and pulse durations from 10 up to 1000 ms. The method transforms accumulated electrical energy in a capacitor bank into mechanical energy. For experimental investigations, flat and cylindrical coil devices were used for a capacitor-type pulse current generator. The proposed method has been experimentally validated on timber beams in a specified volume of force loading. The technique demonstrated a potential for controlling force and energy parameters. The effects of operating voltage on coil and ‘metal plate - coil’ distance on the amplitude of dynamic loading have been investigated. Aluminium and steel plates fastened to the object at the point of impact were used to improve excitation efficiency. The developed technique can be used in experimental studies on model joints and real objects.

Equivalence analysis of brake testing methods at the stands

Equivalence analysis of brake testing methods at the stands For use during technical inspection, site stands are being promoted in Russia that implement the static method of checking brake systems with the vehicle wheels stationary. However, the equivalence of such a method to dynamic testing on roller benches or in road conditions has not been previously studied. The presented analysis gives an idea of the nonequivalence of the methods of static and dynamic testing of brakes in parametric and technological terms. Keywords ATS, brakes, stand, braking force, performance

The estimation of Poisson’s ratio by time-averaging and Cornu’s method for isotropic beams

Prior research suggests that direct static (e.g., uniaxial testing) and dynamic (e.g., ultrasonic wave propagation analysis) measurements differ in the estimation of Poisson’s ratio because anisotropies and heterogeneities in the sample material affect the two types of tests differently. Even assuming isotropic and homogeneous material properties, prior research further suggests that discrepancies between static/dynamic test results will exist because the error of the diagnostic techniques for the measurand are inherently different. Finally, thermodynamic effects are not present in static tests but can significantly affect dynamic test results. Given the potential for all these variables to produce discrepancies, it would be helpful to have the measurement of Poisson’s ratio obtainable from the same theory and experimental measurements by either static or dynamic testing methods. Our finite element calculations show that by combining time-averaged scanning digital holography with Cornu’s method, it is theoretically possible to estimate the effective Poisson’s ratio from the anticlastic contours at the antinode of the first out-of-plane bending mode shape. This is true regardless of frequency and therefore applicable for both static and dynamic measurements. Our results show that the estimate of Poisson’s ratio by Cornu’s method using data from simulations of mode shapes approaches the true value of Poisson’s ratio. In addition, our research suggests that beam geometry and boundary conditions are fundamental factors limiting the convergence of the estimate of Poisson’s ratio to the true value of Poisson’s ratio regardless of performing a static or dynamic test.

Inhibition of calcium carbonate scale under severe conditions

Despite extensive works have been devoted to study the scale inhibition behavior, the performance of inhibitors is still not fully understood. In this paper, we present a laboratory study to elucidate the impact of water composition on the performance of some commonly used phosphonate and polymeric calcium carbonate scale inhibitors, in highly supersaturated brines at high temperature. Calcium tolerance inhibitor chemicals with various molecular structures are studied using dynamic scale loop test method at 150 °C. Brine composition is varied by changing the non-stoichiometry of scaling lattice ions, e.g., ( Ca 2 + ) / ( CO 3 2 − ) ratio, over a wide range. Test results indicate that the effectiveness of inhibitors can be significantly changed by the scaling ion ratio. In general, the efficacy of inhibitors decreases significantly with calcium concentration in the test brine even at constant supersaturation state and temperature, and also the performance ranking of the different inhibitor chemistries can be changed with brine composition. This could be caused by the alternations of interactions between inhibitor molecules and the surface of calcium carbonate scale crystals. Findings from this study suggest that the effect of scaling ion ratio must be considered in scaling risk assessment and for the optimization of inhibitor treatment programs.

Research progress on dynamic testing methods of wood shear modulus: A review

Wood is a non-homogeneous and orthotropic natural polymer material. It is important to test the wood shear modulus and elastic constants accurately and reliably using dynamic methods. Based on the introduction of the advantages of six common methods for dynamic testing of wood shear modulus, such as free plate torsional mode method, free bar torsional vibration method, and Timoshenko beam iterative method, issues associated with the applicability and accuracy of these methods are also pointed out. Recent methods, such as the free square plate torsional mode method and the square plate static torsional strain method, that were developed to dynamically test the shear modulus of wood and wood composite materials, are presented as effective ways to tackle these issues. These new approaches are expected to provide beneficial technical support for using small specimens, overcoming the size effect of specimens, simplifying the testing procedures, improving the test accuracy, and expanding the application range in the dynamic testing of wood shear modulus. These approaches have practical significance in promoting the industrialization and development of structural engineering, furniture and interior decoration, transportation, military, and musical instrument industries.

Signal Identification of Wire Breaking in Bridge Cables Based on Machine Learning

With the booming development of bridge construction, bridge operation and maintenance have always been major issues to ensure the safety of the community. Affected by the long-term service of bridges and natural factors, the safety and durability of cables can be threatened. Cables are critical stress-bearing elements of large bridges such as cable-stayed bridges. Realizing the health monitoring of bridge cables is the key to ensuring the normal operation of bridges. Acoustic emission (AE) is a dynamic nondestructive testing method that is increasingly used in the local monitoring of bridge cables. In this paper, a testbed is described for generating the acoustic emission signals for signal identification testing with machine learning (ML) models. Owing to the limited number of measured signals being available, an algorithm is proposed to simulate acoustic emission signals for model training. A multi-angle feature extraction method is proposed to extract the acoustic emission signals and construct a comprehensive feature vector to characterize the acoustic emission signals. Seven ML models are trained with the simulated acoustic emission signals. Long short-term memory (LSTM) has been specially applied for deep learning demonstration which requires a large amount of training data. As all machine learning models (including LSTM) provide desired performance, it shows that the proposed approach of simulating acoustic emission signals can be effective.

Pseudo-dynamic test and numerical analyses of staggered truss framing systems

To facilitate the popularization and application of high-rise staggered truss framing systems in high intensity area, the seismic performance of the staggered truss framing system was studied. A series of pseudo-dynamic tests were carried out on a 14-story staggered truss framing system model with a scale of 1/8. The time-history curves of displacement, acceleration and base shear under Taft earthquake record with different peak ground accelerations were obtained. Based on the test results, the stiffness degradation, equivalent viscous damping coefficient of the test model were analyzed. The proportion of plastic energy consumption of each component to the whole plastic energy consumption of the structure was obtained. Three different finite element models were established to study the effect of the Vierendeel panel length on the seismic performance. The test results show that the staggered truss framing system has a large lateral stiffness in the direction of the truss, but its seismic energy dissipation capacity is insufficient. Through the pseudo dynamic test method, it is found that the column base is the weak part of the staggered truss framing system. The research results can be used to guide the design of staggered truss framing systems.