Grid-like Vibration Measurements on Power Transformer Tank during Open-Circuit and Short-Circuit Tests

In this work, the vibrations on the surfaces of the tank wall, stiffeners, and the cover of a 5 MVA transformer experimental model were measured during open-circuit and short-circuit transformer tests. Vibration measurements of a transformer tank side were conducted at discrete points using two different voltage sources in no-load test. Using interpolation functions, the RMS values of acceleration and vibration velocity are visualized and compared for each considered measurement configuration (no-load and load tests and two different excitation sources). Significant differences in mode shapes and amplitudes of vibrations at different frequencies are observed. The maximum RMS values of acceleration, velocity and displacement in the open-circuit test are 0.36 m/s2, 0.31 mm/s, and 0.42 µm, respectively. The maximum values in short-circuit test are 0.74 m/s2, 1.14 mm/s, and 1.8 µm, respectively. In the short-circuit test, the frequency component of 100 Hz is dominant. In the open-circuit test, the first few 100 Hz harmonics are significant (100 Hz, 200 Hz, and 300 Hz). In addition to the visualization of RMS values during the open-circuit and short-circuit tests, animations of the vibrations are created. Fourier analysis and phase comparison between frequency components are also used to show vibration animations at dominant frequencies in the spectrum (100 Hz harmonics). The visualization of the vibrations at the tank wall surfaces is transferred into 3D space in such a way that all 15 surfaces are mapped to the spatial coordinates of the surfaces so that a 3D model of the acceleration, vibration velocity, and displacement of the transformer tank is shown.

Numerical and Experimental Investigations On Cross-sensitivity Characteristics of Instrumented Wheelset Associated with Longitudinal Force and Lateral Contact Position

It is crucial to grasp wheel-rail contact forces in the evaluation of running safety and curving performance of railway vehicles. To measure the wheel-rail contact forces, instrumented wheelset, which has the strain gauges on the wheel surface, is widely used. The purpose of this research is to increase the measurement accuracy of the wheel-rail contact forces by understanding the detailed characteristics of the instrumented wheelset. Although the various research works on the instrumented wheelset have been carried out to increase the measurement accuracy of wheel-rail contact forces, there are few works considering the longitudinal force and the lateral shift of the wheel-rail contact point. However, sometimes the longitudinal force has a non-negligible influence on the measurement accuracy on the instrumented wheelset. In this paper, the authors clarify the cross-sensitivity characteristics of the instrumented wheelset when the longitudinal force is applied to the various lateral position on the wheel tread through the FEM analysis and the static load test. The authors also propose a method to approximate the cross-sensitivity as an analytical function of the lateral and circumferential contact positions.

Experimental Investigation on the Vertical Bearing Characteristics of Jacked Piles in Saturated Silt Foundations under Excavation

A model test system for vertical bearing characteristics of the jacked piles in saturated soil foundations under excavation has been introduced. The system device comprises a soil pressure loading system, a model pile loading system, a soil vacuum saturation system, a model box, a model pile, and a control and data acquisition system. The soil vacuum saturation system designed for the model box of this test device can ensure that the saturated soil in the model box can reach a higher degree of saturation. Loading and unloading were conducted on the soil sample in the model box through the soil pressure loading system to simulate the soil excavation so that the soil sample and that in the field have the same stress state and history. The soil consolidation pressure, pile jacking pressure, pile tip force, soil consolidation settlement, and pile displacement at the top were collected and monitored in real time through the control and data acquisition system. This device is used to conduct an experimental study on the bearing characteristics of the jacked piles in saturated silt foundations under excavation. The results indicate that the static load test increases the residual pressure on the tip of the jacked pile while also increasing soil stiffness at pile tip and ultimate tip resistance, thereby increasing the pile top stiffness and ultimate load-carrying capacity. However, when the jacked pile is left undisturbed for the same time, the static load test on the jacked pile does not affect the pile skin friction resistance. There is a better linear relationship between the pile skin friction resistance and the undrained shear strength of the soil under the corresponding stress path during the static load test of the normally consolidated soil and the jacked pile after overburden pressure unloading. There is a good linear relationship between the ultimate resistance and the undrained shear strength of the soil under the corresponding stress path in pile sinking, normally consolidated soil, and during the static load test on jacked pile after unloading.

Mechanical Properties of a 3D-Printed Wall Segment Made with an Earthen Mixture

This study provides a contribution to the research field of 3D-printed earthen buildings, focusing, for the first time, on the load-bearing capacity of these structures. The study involves the entire production and testing process of the earthen elements, from the design, to the preparation of the mixture and the 3D printing, up to the uniaxial compression test on a wall segment. The results indicate that 3D-printed earthen elements have a compressive strength of 2.32 MPa, comparable to that of rammed earth structures. The experimental data also made it possible to draw conclusions on the action of the infill, which seems to have the function of stopping the propagation of cracks. This has a positive effect on the overall behavior of 3D-printed earthen elements, since it avoids the onset of dilative behavior in the final stages of the load test and maintains ultimate load values higher than 50% of the maximum load.

The “Fight Bite” Saline Joint Loading Test: Effectiveness in Detecting Simulated Traumatic Metacarpophalangeal Arthrotomies

Background: The saline load test is routinely used to recognize other joints’ traumatic arthrotomies; however, there are currently no studies evaluating the novelty of this test for metacarpophalangeal joints (MCPJs). This study aimed to investigate the effectiveness and sensitivity of saline load testing in identifying the traumatic arthrotomies of the MCPJs using human cadavers. Methods: This was a cadaveric study of 16 hands (79 MCPJs). Traumatic arthrotomies were created using 11-blade stab-incisions, followed by blunt probing into the joint on the radial or ulnar side of the flexed MCPJs. A 3-mL syringe was used to inject intra-articular methylene-blue-dyed saline from the contralateral side. The volume at saline extravasation was recorded. Test sensitivity and factors influencing extravasation volume were assessed. Results: The mean (range) volume injected to identify arthrotomy of all MCPJs was 0.18 mL (0.1-0.4 mL). The mean volume to identify MCPJ arthrotomy of the thumb, index, long, ring, and small fingers was 0.16 mL (0.1-0.3 mL), 0.19 mL (0.1-0.3 mL), 0.21 mL (0.1-0.4 mL), 0.17 mL (0.1-0.3 mL), and 0.16 mL (0.1-0.3 mL), respectively. Cadaver age, laterality, and joint range of motion were not significantly associated with the injected volume at extravasation( P > .05, each). Injection volumes of 0.3 and 0.32 mL were required to detect arthrotomies at 95% and 99% sensitivities across all MCPJs. None of the MCPJs required > 0.4 mL to detect arthrotomy. Conclusions: Saline joint loading volumes to detect traumatic arthrotomy were similar for all MCPJs. Injection volumes of 0.32 mL is suggested for 99% sensitivity. Our findings provide the first report, to our knowledge, on intra-articular injection volumes expected to detect an arthrotomy of MCPJ. This is critical for further validation using in vivo clinical studies.

Data-Driven Modeling of Ultimate Load Capacity of Closed- and Open-Ended Piles using Machine Learning

Field pile load tests are fairly expensive experiments that can be applied to certain pile types required to be installed in full scale. Hence, it is neither practical nor efficient to perform a load test for every installed pile. While there exist many empirical relations for predicting pile capacities, such methods typically suffer from accuracy and generality. Therefore, current geotechnical practice still looks for methods to accommodate full-scale pile load testing to serve as both accurate and practical tools. In this study, load bearing capacities of closed and open-ended piles in cohesive and cohesionless soils are predicted using machine learning. Nine such methods are utilized in the analyses where CPT and pile data are considered as the learning features necessary to teach those methods the database gathered via a comprehensive search. Then, machine learning models are developed, and the databases are separated into five-folds according to the cross-validation-principle, which are used for both training and testing of the machine learning methods. Model predictions are validated with classical empirical equations. Results indicate that the Relevance Vector Regression and the Random Forest methods typically generate considerably better predictions than the other methods and empirical equations. Hence, machine learning methods are found as reliable tools to predict the pile load capacities of both open-ended and closed-ended piles provided that there is a large enough database and an appropriate method to use.

Mechanical Properties of a 3D Printed Wall Segment Made with an Earthen Mixture

This study provides a contribution to the research field of 3D printed earthen buildings, focusing, for the first time, on the load-bearing capacity of these structures. The study involves the entire production and testing process of the earthen elements, from design, to the preparation of the mixture and the 3D printing, up to the uniaxial compression test on a wall segment. The results indicate that 3D printed earthen elements have a compressive strength of 2.32 MPa, comparable to that of rammed earth structures. The experimental data also made it possible to draw conclusions on the action of the infill, which seems to have the function of stopping the propagation of cracks. This has a positive effect on the overall behavior of 3D printed earthen elements, since it avoids the onset of dilative behavior in the final stages of the load test and maintains ultimate load values higher than 50% of the maximum load.

Evaluation of Static Pile Load Test Results of Ultimate Bearing Capacity by Interpreting Methods

in geotechnical engineering, foundation piles are ideal for deep foundations that cannot bear higher loads. This architectural expansion places a great deal of responsibility on the engineer to anticipate the appropriate load for the constructor. Unfortunately, calculations of the pile’s bearing capacity are not accessible. It has always been a source of concern for geotechnical engineers, as the structure’s safety depends on the pile’s bearing capacity and gives it a safe value. These research tests are previously known pile load test data from several locations in Nasiriyah to determine the ultimate load-carrying capacity using various interpreting methodologies. A database that was used to test the pile load for three different areas in Nasiriyah, southern Iraq: The Main Drain River Bridge Project, the Al-Eskan Interchange Project, and the Al-Hawra Hospital, as determined by analytical methods, as well as evaluating the final loading values resulting from the methods used, by ASTM D-1143, American and British Standard Code of Practice BS 800. The final capacity for the pile bearing is estimated using these approaches, which are depicted in the form of a graph-based on field data. Chin-Kondner and Brinch Hansen algorithms anticipate the highest failure load for all piles based on the comparison. On average, Chin–Kondner’s ultimate load is 22% higher than Hansen’s maximum load for the 22 pile load tests. Decourt and DeBeer, and Mazurkiewicz’s techniques yielded the closest average failure load. Buttler-Hoy approach yielded the smallest failure load.

Integral State Feedback Control Using Linear Quadratic Gaussian in DC-drive System

The electric motor is one of the technological developments which can support the production process. DC motor has some advantages compared to AC motor especially on the easier way to control its speed or position as well as its widely adjustable range. The main issue in the DC motor is controlling the angular speed with uncertainty and disturbance. The alternative solution of a control method with simple, easy to design, and implementable in a multi-input multi-output system is integral state feedback such as linear quadratic Gaussian (LQG). It is a combination between linear quadratic regulator and Kalman filter. One of the advantages of this method is the usage of fewer sensors compared with the original linear quadratic regulator method which uses sensors as many as the state in the system model. The design, simulation, and experimental study of the application of LQG as state feedback control in a DC-drive system have been done. Both performance and energy were analyzed and compared with conventional proportional integral derivative (PID). The gain of LQG was determined by trial whereas the PID gain is determined from MATLAB autotuning without fine-tuning. The load test and tracking test were carried out in the experiment. Both simulation and hardware tests showed the same result which LQG is superior in integral absolute error (IAE) by up to 74.37 % in loading test compared to PID. On the other side, LQG needs more energy, it consumes higher energy by 6.34 % in the load test.

Experimental Study of Dynamic Mechanics Characteristics of Saturated Marble under Low Temperature

The effect of low temperature on dynamic mechanical properties of low-temperature frozen marble at a high strain rate was studied by a dynamic impact test. The influence of temperature changes (25°C–40°C), especially negative temperature changes, on dynamic strength, peak strain, and failure mode of the marble was analyzed. Combined with the fracture morphology, the reasons for the deterioration of dynamic mechanical strength of water-saturated marble at lower negative temperatures were investigated. The experimental results show that the dynamic mechanical properties of marble are significantly affected by the change of freezing temperature. The dynamic strength firstly decreases and then increases with the decrease of temperature in the range of 25°C to −20°C, but the dynamic strength decreases sharply after −20°C. The peak strain increases first, then decreases, and then increases, and the inflection point temperature of the change is −5°C and −20°C, respectively, which is completely different from the static load test results of frozen rock at low temperature. According to fracture morphology analysis, water-ice phase transformation at −5°C leads to the nucleation and expansion of a large number of microcracks and micropores in marble, and the interaction between slip separation cracks and microstructures caused by shear deformation under impact separates the massive crystals inside the rock into microscopic crystals, thus reducing the bearing capacity and strength of marble. From −5°C to −20°C, the ice medium and marble matrix contract when cooled, and the microcracks and micropores caused by the phase transition gradually close during the contraction process, the integrity of the rock is restored, and the dynamic strength of the rock is increased. At −20°C, there is a great difference in the shrinkage rate of the marble matrix and the ice medium, and the internal microstructure increases. Meanwhile, the impact amplifies the brittleness of the rock at low temperatures, leading to a sharp decrease in the dynamic strength of the marble.