Recorded Test Data Research Articles

On the Resistance of Cruciform Structures during Ship Collision and Grounding

This paper presents an experimental, numerical, and analytical study of a novel specimen subjected to local in-plane load, to investigate its crushing deformation and resistance. The specimen was designed and fabricated to simplify the cruciform structure in double-hulled vessels subjected to external loads during collision and grounding incidents. The study results will provide reliable insights into grounding scenarios as well as side collision scenarios of double-hulled vessels. A quasi-static indentation test and related numerical research showed good agreement regarding deformation mode and force–displacement response. On the basis of the experimental and numerical results, an analytical method is proposed to derive the deformation energy, the instantaneous resistance, and the mean resistance of the deformed structure. The analytical method was verified with recorded test data and a nonlinear finite element analysis. It enables a rapid assessment of the response of the structure under accidental loads, which is a guideline for the design of crashworthy hull structures and the assessment of their crashworthiness.

Response Characteristics of Pre-Stressed Strand Cables Subjected to Low-Velocity Impact: Experiment Test

This paper introduces some experimental data measured from 63 impact tests of pre−stressed strand cables. The test specimens consist of seven steel wires that have a length equivalent to 100 times the outside diameter. To ensure consistency with the engineering service status, the strand cables are fully installed in a specially designed device and are axially pre−stretched to 0% to 40% of the ultimate bearing capacity before being subjected to lateral impact. The mass of the indenter is 50.34 kg, and the maximum impact velocity reaches 13 m/s. Two dimensionless variables, axial force and input kinetic energy, are used to control the experimental parameters. The recorded test data show that input energy and pre−stress level are the key factors governing the impact behavior, which is mainly characterized by plastic deformation controlled by the combination of tension and flexure, and the dynamic fracture concentrated in the impact zone is controlled by the joint effects of compression, tension and shear. As the impact energy increases, the dynamic mode of the test specimen changes from elastic rebound to plastic deformation, and finally evolves into fracture of some or all steel wires, which correspond to slight, partial and total loss of pre−tension, respectively. An increase in the level of pre−stress will significantly reduce the critical displacement of the structural failure but has little effect on the critical failure energy. The present paper provides a basic experimental data and mechanical analysis framework for the analysis, design and evaluation of the mechanical behavior of strands under accidental lateral impact.

Optimization design of functionally graded ultra‐high performance cementitious composite on flexural behavior

AbstractThe research aims to investigate and optimize the flexural behavior of functionally graded ultra‐high performance cementitious composite (FGUHPCC), and to optimize the design of FGUHPCC by using a numerical simulation program named RFPA3D. The equivalent flexural strength and corresponding deflection capacity of double‐ and single‐layered FGUHPCC beams were analyzed by carrying out four‐point bending test. Furthermore, with the numerical model set in RFPA3D, the crack evolution and acoustic emission (AE) event of specimens at limit of proportionality (LOP) point, modulus of rupture (MOR) point, and 30% of MOR are, therefore, discussed. The results indicate that functionally graded design can help to improve the flexural capacity and fracture toughness of all specimens. In addition, the main crack of FGUHPCC looks more irregular and larger damage areas are formed. Higher principal stress and more AE events can be identified in FGUHPCC than that of single‐layer UHPCC. Based on the recorded test data, the influence of bottom layer thickness was also investigated with respect to the peak flexural load and the AE energy. The results indicate that the optimum load capacity and flexural energy can be obtained when layer thickness ratio is about 0.6.

Large wind turbine edge instability field validation

Wind turbines can exhibit flutter-like edgewise instabilities past a critical rotor speed. These edgewise instabilities are dominated by an edge-torsion coupling due to flapwise blade deflection. This paper experimentally validates the predicted stability limit of a 7 MW machine. State of the art simulation software is used to compare against recorded test data and characterize the observed flutter mechanism. The critical rotor speed at which the edgewise instabilities occur at in field measurements can be predicted by time domain simulations and stability analysis with very good agreement.

Data Analysis and Validation of Acquired Temperature Data on Underwater Platform

<p class="western" style="margin-left: -2.25cm; margin-bottom: 0.35cm; line-height: 115%;">Underwater missiles are launched from canister by hot gasses produced by a gas generator. Hot gasses eject the missile out of canister, positioned on an underwater platform in high seas at a depth of 50 m to 70 m. During development phase of submarine launched missile, maximum number of physical parameters related to platform and launching mechanism are acquired on a data acquisition system on-board platform and selected critical parameters are transmitted to control station in real time through an optical data communication link. Missile parameters are recorded on-board and transmitted to the control station by delayed transmission technique once the missile is out of water. Exit velocity of missile is very important parameter for the missile trajectory and range, which depends upon the heat loss in canister and annular gap pressure between missile and canister during the ejection process. Prediction of exit velocity is validated by heat loss calculation by measured temperature at different stations during the test. Temperature measurement is carried out by sensors mounted on the inner wall of canister and also by jumping type of temperature sensor, which measures canister gas temperature. In spite of all efforts, few sensors do not work as expected. It is important to measure various parameters according to instrumentation measurement plan. In case of temperature measurement, sometimes, it is required to predict temperature at location, where sensor was originally not mounted. To validate the recorded test data, another set of data is needed for which one has to wait till next test is conducted that may take years and practically impossible to ensure identical test setup and environmental condition. A mathematical approach to predict temperature at required location and to validate the recorded test data is presented.</p><p class="western" style="margin-left: -2.25cm; margin-bottom: 0.35cm; line-height: 115%;"> </p><p class="western" style="margin-left: -2.25cm; margin-bottom: 0.35cm; line-height: 115%;"> </p>

Experimental and Numerical Study on Modal Dynamic Response of Water-Surrounded Slender Bridge Pier with Pile Foundation

This paper presents an experimental program performed to study the effect of fluid-structure interaction on the modal dynamic response of water-surrounded slender bridge pier with pile foundation. A reduced scale slender bridge pier specimen is built and tested through forced vibration method. The vibration periods of the first four lateral modes, including the first two modes along x-axis and the first two modes along y-axis, are measured based on the specimen submerged by 16 levels of water and designated with 4 levels of tip mass. Three-dimensional (3D) finite-element models are established for the tested water-pier system and analyzed under various combined cases of water level and tip mass. Percentage increases of vibration periods with respect to dry vibration periods (i.e., vibration periods of the specimen without water) are determined as a function of water level and tip mass to evaluate the effect of fluid-structure interaction. The numerical results are successfully validated against the recorded test data. Based on the validated models, the modal hydrodynamic pressures are calculated to characterize the 3D distribution of hydrodynamic loads on the pier systems. The research provides a better illumination into the effect of fluid-structure interaction on the modal dynamic response of deepwater bridges.

The dynamics of cerebrovascular reactivity shown with transfer function analysis

Cerebrovascular reactivity (CVR) is often defined as the increase in cerebral blood flow (CBF) produced by an increase in carbon dioxide (CO2) and may be used clinically to assess the health of the cerebrovasculature. When CBF is estimated using blood oxygen level dependent (BOLD) magnetic resonance imaging, CVR values for each voxel can be displayed using a color scale mapped onto the corresponding anatomical scan. While these CVR maps therefore show the distribution of cerebrovascular reactivity, they only provide an estimate of the magnitude of the cerebrovascular response, and do not indicate the time course of the response; whether rapid or slow. Here we describe transfer function analysis (TFA) of the BOLD response to CO2 that provides not only the magnitude of the response (gain) but also the phase and coherence. The phase can be interpreted as indicating the speed of response and so can distinguish areas where the response is slowed. The coherence measures the fidelity with which the response follows the stimulus. The examples of gain, phase and coherence maps obtained from TFA of previously recorded test data from patients and healthy individuals demonstrate that these maps may enhance assessment of cerebrovascular pathophysiology by providing insight into the dynamics of cerebral blood flow control and distribution.

Cyclic Loading of Polyetheretherketone at High Tensile Stress Levels

In a recent study of the corresponding author, it was found that PEEK bearing elements revealed high (irreversible) surface strains if they were loaded between steel sheets. Since this reflects the conditions in the practical application and because the rolling properties are dominated by the surface material, a more detailed analysis of highly strained PEEK was required. Hence, fatigue tests in the high stress tensile regime were conducted. The experiments were carried out on servo-hydraulic testing machines and during the tests the mechanical response of the specimens was recorded. Two material modifications of PEEK were investigated in the research: untreated PEEK (without heat treatment) and annealed PEEK which was modified using defined thermal conditions. The analysis of the recorded test data aimed on the distinction between cumulative material response (creep deformation, material hardening / softening) and spontaneous material response (material hardening / softening). At the highest stress levels, the cumulative response pretended material softening with increasing number of cycles. However, by examining the spontaneous material response which became stiffer with increasing number of cycles, it was shown that the cumulative softening was caused by time-dependent deformation processes.

Coherence analysis on thermal effect for power cables under different environmental conditions

There are 2 important aspects of this research; these are the experimental study and the data analysis, which are based on coherence analysis. In this study, a low-voltage power cable is tested under 2 different environments, air and water, and the variations in temperature are measured for the conductor, the sheath parts of the cable, and the environment. The recorded test data are analyzed using such as coherence analysis. This in turn provides the means to determine the relationship among the sheath, conductor, and the environment. In conclusion, high correlated peaks in the frequency domain are used to determine the temperature effect.

The high-temperature effect on the breakdown voltage of an air-gap at atmospheric pressure with reference to paschen curve

The breakdown voltage of an air-gap was determined as a function of gap pressure-spacing product as given by Paschen curve at 20 °C. This was followed by experimental research on the effect of temperature on the breakdown voltage. In this paper, a family of Paschen curves is calculated as a function of the temperature and gap-spacing. A comparison between the corresponding calculated Paschen curves and the recorded test data is then made. The results validate the theory presented and confirm its limitations at higher temperatures.

Fuzzy-Logic Modeling of a Rolling Unmanned Vehicle in Antarctica Wind Shear

of wind shear are investigated using the recorded test data during a flight from the Pegasus white ice runway in Antarctica. The main purpose of this paper is to determine the reasons and characteristics of roll oscillations for improvement of autopilot design and ground operator training. The Meridian flight test is conducted with the necessaryrangeconstraint, which precludes steadylevel flight.The measured orestimated data,such as theangle of attack and sideslip angle, are filtered through a nonlinear compatibility analysis. The estimated aerodynamic coefficients are modeled as implicit functions of filtered flight variables in a concept of aerodynamic model identification, instead of parameter identification. A model identification method called fuzzy-logic modeling is used to set up the aerodynamic models without assuming the functional relations. The aircraft’s oscillatory stability and control derivatives are found to be significantly impacted by the environmental disturbances. The exhibited highly oscillatory motion in the manual-control mode is analyzed and identified as the pilot-induced oscillation with a new energy method. It is shown that the pilot-induced oscillation is identified as the motion when the motion energy is increasedbythecontrolinput.Intheautopilot flight,themotionisdeterminedtobewingrock,whichisexcitedbythe pilot-induced oscillation in the manual mode and sustained by the interaction between the wing wake and the V tail.

Rotordynamic Performance of Shimmed Gas Foil Bearings for Oil-Free Turbochargers

Oil-free turbochargers (TCs) will increase the power and efficiency of internal combustion engines, both sparking ignition and compression ignition, without engine oil lubricant feeding or scheduled maintenance. Using gas foil bearings (GFBs) in passenger vehicle TCs enables compact, lightweight, oil-free systems, along with accurate shaft motion. This paper presents extensive test measurements on GFBs for oil-free TCs, including static load-deflection measurements of test GFBs, rotordynamic performance measurements of a compressed air driven oil-free TC unit supported on test GFBs, and bench test measurements of the oil-free TC driven by a passenger vehicle diesel engine. Two configurations of GFBs, one original and the other modified with three shims, are subjected to a series of experimental tests. For the shimmed GFB, three metal shims are inserted under the bump-strip layers, in contact with the bearing housing. The installation of shims creates mechanical preloads that enhance a hydrodynamic wedge in the assembly radial clearance to generate more film pressure. Simple static load-deflection tests estimate the assembly radial clearance of the shimmed GFB, which is smaller than that of the original GFB. Model predictions agree well with test data. The discrepancy between the model predictions and test data is attributed to fabrication inaccuracy in the top foil and bump strip layers. Test GFBs are installed into a TC test rig driven by compressed air for rotordynamic performance measurements. The test TC rotor, 335 g in weight and 117 mm long, is coated with a commercially available, wear-resistant solid lubricant, Amorphous M, to prevent severe wear during start-up and shutdown in the absence of an air film. A pair of optical proximity probes positioned orthogonally at the compressor end record lateral rotor motions. Rotordynamic test results show that the shimmed GFB significantly diminishes the large amplitude of subsynchronous rotor motions arising in the unmodified GFB. Predicted synchronous rotor amplitudes and rigid body mode natural frequencies agree reasonably well with recorded test data. Finally, the oil-free TC is installed into a passenger vehicle diesel engine test bench. The TC rotor speed is controlled by the vehicle engine. Speed-up tests show dominant synchronous motion (1X) of the rotor. Whirl frequencies of the relatively small subsynchronous motions are associated with the rigid body natural mode of the TC rotor-GFB system as well as (forced) excitation from the four-cylinder diesel engine. The bench test measurements demonstrate a significant reduction in the amplitude of subsynchronous motions for the shimmed GFB, thus verifying the preliminary test results in the TC test rig driven by compressed air.

Seismic Damage Detection of a Full-Scale Shaking Table Test Structure

A series of full-scale tests was conducted on the E-Defense shaking table facilities in Japan to simulate various levels of realistic seismic damage in a high-rise structural steel building. During the shaking table tests, the specimen experienced damage of the concrete slabs, beam-to-column connections, and nonstructural walls. The densely recorded test data of global and local structural deformation and the extensive acceleration records provide a unique benchmark case for evaluating the effectiveness of vibration-based damage diagnosis methods. Dynamic properties of the specimen were extracted from floor accelerations under the white noise excitations by the frequency response function curve-fitting method and autoregressive with exogenous term method. The natural frequencies of the structure decreased on average 4.1, 5.4, and 11.9% after three levels of seismic excitation, respectively, because of increasing extent of structural and nonstructural damage. The analysis of the vibration data shows that the mode shapes changed very little because the damage was distributed over the entire specimen rather than being concentrated on one floor or story for the high-rise moment frame building.

2-4 マルチメディア機器における試験データ同期記録再生手法の検討(第2部門 コンシューマエレクトロニクス&マルチメディアストレージ)

2-4 マルチメディア機器における試験データ同期記録再生手法の検討(第2部門 コンシューマエレクトロニクス&マルチメディアストレージ)

Experiences in modelling the performance of generating plant for frequency response studies on the British transmission grid

Significant changes to the generation mix on the British transmission system have occurred in the past 10 years, and this trend is expected to continue in the future with an increase in renewable generation. This change, in conjunction with market changes, has driven the need to establish suitable generator models for thermal plant used in dynamic response studies. These studies are presently used to quantify the dynamic requirement that secures the transmission system against large instantaneous losses of power. This paper provides an account of the experiences gained in modelling the performance of generators based in Great Britain. Established governor models to represent the behaviour of traditional coal and oil fired plant already exist and comments are made on their performance against system incidents. Models of combined cycle units using traditional open cycle gas turbine models have shown poor correspondence with monitored grid data in simulations. A gas and steam turbine governor model to represent combined cycle plant was developed, and is presented, with results from validation trials against recorded test data. Improvements in simulating grid frequency have been demonstrated using the developed models in a full network simulation of a recent generator loss event.

Measurement and Analysis of Impact Test Data for X100 Pipeline Steel

Charpy upper shelf energy is widely used as a fracture controlling parameter to estimate the crack arrest/propagation performance of gas transportation pipeline steels. The measurement of this fracture criterion particularly for modern steels and its apportion into different components, i.e. fracture and non-related fracture energy, are of great importance for pipeline engineers. This paper presents the results of instrumented Charpy impact experiments on high-grade pipeline steel of grade X100. First, the instrumentation technique including the design and implementation of a strain gauge load-cell and the details of the data-recording scheme are reviewed. Next, the experimental data obtained from the Charpy impact machine so instrumented are presented and discussed. These include the test data from full and sub-sized Charpy V-notched specimens. The instrumented Charpy machine was able to capture the load history in full during the fracture process of the test specimens resulting in a smooth load-time response. This eliminated the need for filtering used in similar test techniques. From the recorded test data the hammer displacement, impact velocity and fracture energy were numerically calculated. The results showed that there was a significant drop in hammer velocity during the impact event. This resulted in a change in the fracture mode from dynamic to quasi-static which was more appreciable for full-size Charpy test samples. As a result, sub-sized specimens might be preferable for impact testing of this steel in order to guarantee the conditions of dynamic crack propagation in the specimen ligament. Accurate analysis of the instrumented impact test data showed that the ratio of crack initiation energy to propagation energy was around 30% for the X100 steel. It can be concluded that in impact testing of high-grade pipeline steel a significant portion of overall fracture energy is consumed in non-related fracture processes. This high fracture initiation energy should be accounted for if the current failure models are going to be used for toughness assessment of highstrength low-alloy gas pipeline steels.

Examination of high frequency contact chatter in trailing arm armatures

Experiments with relatively high action armatures in a medium caliber launcher (35-mm rail height) have shown a repeatable vibration in the armature which is observable in the early parts of both the recorded muzzle voltage and on the contact surface of the rail. Although the vibration or "chatter" in the contact does not appear to grow in amplitude or shift in frequency during this early part of the launch, it is probable that it plays a role in conditioning the armature surface for later transition in the launcher. This paper examines the recorded test data and compares it with structural analyses of the launch package to show that the chatter is correlated with natural vibration modes in the armature. Probable causes of chatter are discussed and tests incorporating some potential solutions are presented. Reduction or elimination of this behavior is important both for long-term bore life of the launcher and maximum launch package performance with payloads that are sensitive to lateral launch loads.

Plotting Blower-Test Curves

Abstract To the several methods of plotting blower-test curves another method is here added, whose utility is demonstrated by the solution of problems from graphically recorded test data. Diagrams are given for impellers with blades tilted forward, with blades radial, and with blades tilted backward, the coordinates used being revolutions per minute and static pressure in inches of water. Two series of curves are given, one showing various rates of discharge in cubic feet per second, and the other the volumes discharged per second per horsepower.