Equivalent Test Conditions Research Articles

Investigation of microstructure evolution and its effect mechanism on high temperature tensile properties of 304L stainless steel processed by laser powder bed fusion

Laser Powder Bed Fusion (LPBF) 304L stainless steel has garnered significant attention due to its unique blend of strength and ductility at room temperature. However, there is limited understanding of its high-temperature tensile properties. In this study, we conducted tensile testing on LPBF 304L at temperatures ranging from 623K to 1023K in its as-built state. Additionally, we performed a comparative tensile test on traditionally hot-rolled (at 1433K) 304L stainless steel under equivalent test conditions. The results revealed that LPBF 304L steel exhibited high ductility at 973K (ultimate tensile stress (UTS) is 257.3 ± 3.6 MPa)-1023K (UTS is 218.7 ± 3.8 MPa), but its strength (yield strength (YS) decreased from 346.0 ± 4.5 MPa to 182.7 ± 3.8 MPa) and plasticity (UTS decreased from 405.7 ± 5.3 MPa to 218.7 ± 6.4 MPa) decreased slowly as the testing temperature increases. We also delved into the microstructure and its impact on high-temperature tensile deformation. The fine grains and ensuing dynamic recovery were found to be responsible for the reduced strength and ductility of LPBFed 304L samples at elevated temperatures. Furthermore, a sawtooth fluctuation emerged in the stress-strain curve at 873K, which could be attributed to dynamic strain aging (DSA) and the interaction between solute elements and dislocations.

Temperature tests of cells - uncertainty considerations

The paper presents the estimation of the uncertainty in the measurement of the maximum surface temperature of voltaic cells exposed to specific tests for the type of intrinsic safety protection. For this purpose, equivalent test conditions using the short-circuit test stand are considered. In the first part, the risk of explosion is presented and it is mentioned that the risk of explosion arises due to the presence of technical equipment in areas where flammable substances may be present. In the second part, the requirements for testing cells are briefly presented. It also introduces the configuration of the stand used for testing. The third part of the paper was devoted to presenting and discussing the results obtained. The analysis of the test results revealed that the measurement uncertainty depends on the test conditions and the application of the temperature sensors. This result would help estimate the surface temperature of cells considering the favorable conditions in terms of minimum uncertainty.

Examining Distributed Fueling Schemes Using Tandem Cavities in a Mach 8 Scramjet

A fundamental investigation of combustion behavior in an ethylene-fueled Mach 8 axisymmetric scramjet combustor was numerically conducted using US3D Reynolds-averaged Navier–Stokes to evaluate the impact of fueling strategies employed with a tandem cavity-equipped combustor. Five fueling configurations with a consistent total fuel-to-air equivalence ratio at 75% of stoichiometric were assessed using a combination of injector ports, located either upstream of, within, between, or downstream of the cavities. Cold-wall and hot-wall conditions were examined, representing shock tunnel equivalent test conditions with minimal wall heating and steady, in-flight wall temperatures, respectively. Two distributed fueling schemes resulted in higher combustion performance when operating in cold conditions and comparable performance when operating in hot conditions. Total pressure losses sustained under each distributed fueling method were equivalent to or lower than those sustained by cases with fuel injected only upstream of the cavities. All distributed schemes examined delayed the onset of flow separation, resulting in improved operational stability and higher resistance to engine unstart.

Benchmarking organic thin film transistor inverter design styles

Organic thin-film transistors (OTFTs) are a promising technology for large-area electronics; choosing an appropriate circuit style is critical to enhancing OTFT circuit functionality and reliability. Here, we design and evaluate different types of static and dynamic logic based on complementary and p-type only technology styles, benchmarking their performance under equivalent processing and testing conditions. We find that differences in off characteristics between n-type and p-type OTFTs to be the primary factor for the choice of logic style. For complementary technology, we conclude that static logic is preferred over dynamic logic considering limited n-type transistor off characteristics, integration density, and delay. In the case of p-type transistors, pre-discharge dynamic logic is preferred over static logic, primarily due to the static power efficiency from good p-type transistor off characteristics. We expect this evaluation to be helpful for assisting design style decisions as these technologies continue to mature and develop.

Influence on Aggregation Structure Changes of Retired Cross-linked Polyethylene (XLPE) Cable Insulation under Pre-qualification Test

In order to investigate the cross-linked polyethylene (XLPE) insulation characteristics of a retired high-voltage cable that has been in operation for 16 years and to evaluate the reliability of reusing it for practical operation, a 180-day pre-qualification test method was applied to a section of this cable to inspect the changes of aggregation structure. In this paper, the electric field and the thermal field of the inner, medium and outer positions of the insulation under the accelerated aging test were analyzed and converted to the corresponding equivalent condition at the surface of the conductor core. It can be found that equivalent testing conditions of the medium and outer positions are close to the cable practical operation condition. The diagnostic measurements of fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and X-ray diffraction (X-ray) were conducted to analyse the aggregation structure of the samples. The results showed that the molecular chain of the inner position of the cable insulation was damaged and the crystalline structure was slightly degraded under high-strength test condition. On the contrary, the crystalline structure of medium and outer positions were both improved after the accelerated aging test because of the reduction of the impurities and the annealing effect. So it can be expected that the rest of this retired cables still have the potential to reuse in long-term actual operation condition.

Study on plasma ablation behavior of C/C composite materials under particle erosion

In order to explore the ablation law and characteristics of carbon/carbon composite materials on the surface thermal protection of hypersonic vehicles under the condition of particle erosion, the ablation test of a 4D C/C composite was carried out based on a small plasma simulated ablation test system. Four sets of experiments were designed according to different temperature and particle concentration. After the test, two kinds of ablation rate were measured, and the microscopic ablation morphology was observed by scanning electron microscope (SEM) and the ablation behavior was analyzed. The results show that, under the equivalent test conditions, the rate of jet temperature increases, and the material ablation rate increases. With the increase of particle concentration, the two kinds of ablation rate of materials increased, the maximum mass ablation rate was 0.0363 g·s−1, and the line ablation rate was 0.053 mm·s−1. The temperature affects the thermal erosion rate of the material, while the particle mainly causes mechanical erosion. The particle has a coupling effect of heat transfer and mechanical destruction on the material, and the material ablation is intensified. Moreover, due to the strong corrosion resistance of carbon fiber, the overall corrosion resistance of materials has obvious anisotropy.

Effect of Buffer System on the Sulfide Stress Cracking Susceptibility of Low-Alloy Steel

The effects of a buffer system in test solution and CO2 partial pressure on sulfide stress cracking (SSC) susceptibility of low-alloy steel were investigated under pH 4.0 at 0.03 MPa H2S partial pressure. A double cantilever beam test was used to quantitatively evaluate SSC susceptibility. The corrosion rates and absorbed diffusible hydrogen concentration were also evaluated. Acetic acid/sodium acetate (acetate buffered solution) and carbonic acid/bicarbonate (bicarbonate buffered solution) buffered solutions were used as buffer systems in this study. From the results, in atmospheric pressure tests, KISSC values in bicarbonate buffered solutions were equivalent to or lower than those in acetate buffered solutions. In high CO2 partial pressure conditions, KISSC values in bicarbonate buffered solutions were much higher than those in acetate buffered solutions. At a high CO2 partial pressure and H2S partial pressure (pCO2/pH2S) ratio condition, hydrogen entry is considered to be greatly prevented by corrosion products probably containing amorphous iron carbonate. Presence of the corrosion product with high protectiveness produced in the high pCO2/pH2S ratio condition suggests the possibility that conventional test conditions using acetate buffered solutions are conservative or are equivalent test conditions for actual field conditions.

Application of the Restoring Force Method for Identification of Lumbar Spine Flexion-Extension Motion Under Flexion-Extension Moment

The restoring force method (RFM), a nonparametric identification technique established in applied mechanics, was used to maximize the information obtained from moment-rotation hysteresis curves under pure moment flexion-extension testing of human lumbar spines. Data from a previous study in which functional spine units were tested intact, following simulated disk injury, and following implantation with an interspinous process spacer device were used. The RFM was used to estimate a surface map to characterize the dependence of the flexion-extension rotation on applied moment and the resulting axial displacement. This described each spine response as a compact, reduced-order model of the complex underlying nonlinear biomechanical characteristics of the tested specimens. The RFM was applied to two datasets, and successfully estimated the flexion-extension rotation, with error ranging from 3 to 23%. First, one specimen, tested in the intact, injured, and implanted conditions, was analyzed to assess the differences between the three specimen conditions. Second, intact specimens (N = 12) were analyzed to determine the specimen variability under equivalent testing conditions. Due to the complexity and nonlinearity of the hysteretic responses, the mathematical fit of each surface was defined in terms of 16 coefficients, or a bicubic fit, to minimize the identified (estimated) surface fit error. The results of the first analysis indicated large differences in the coefficients for each of the three testing conditions. For example, the coefficient corresponding to the linear stiffness (a01) had varied magnitude among the three conditions. In the second analysis of the 12 intact specimens, there was a large variability in the 12 unique sets of coefficients. Four coefficients, including two interaction terms comprised of both axial displacement and moment, were different from zero (p < 0.05), and provided necessary quantitative information to describe the hysteresis in three dimensions. The results suggest that further work in this area has the potential to supplement typical biomechanical parameters, such as range of motion, stiffness, and neutral zone, and provide a useful tool in diagnostic applications for the reliable detection and quantification of abnormal conditions of the spine.

Large loop shifts in hematite nanocrystals embedded in amorphous matrix

In this paper, magnetic hysteresis loop shifts were observed in amorphous-based hematite spin glass. The loop-shift values were found to be much higher than the values for any reported spin-glass system in equivalent test conditions. Also, these values were dependent on the temperatures and external-field ranges, which is indicative of the coexisted exchange bias effect (induced by the exchange coupling between ferromagnetic nanocrystals and spin glass matrix at low temperatures) and minor loops effect (derived from the unsaturated loop measurements).

Comparison of fatigue crack propagation behaviour in two gas turbine disc alloys under creep–fatigue conditions: evaluating microstructure, environment and temperature effects

Gas turbine disc materials should possess excellent fatigue and creep performance due to the severe in service conditions experienced. In this study, a comparison of fatigue crack propagation behaviour in two turbine disc alloys, i.e. N18 and low solvus high refractory (LSHR) superalloy, has been made in terms of the propagation rate and fractography observed under equivalent testing conditions. Temperatures of 650 and 725°C are compared for a trapezoidal dwell fatigue cycle (1–20–1–1) in both air and vacuum at an R ratio of 0·1. It is found that coarse grained LSHR superalloy has better fatigue crack propagation resistance than fine grained N18 in vacuum, which is ascribed to its better creep performance. Oxidation causes significant degradation of fatigue performance of these two alloys, especially in the LSHR superalloy at higher temperature (725°C), resulting in its inferior fatigue performance compared with N18. In the LSHR superalloy, it seems that oxidation is the principal contributor to the deterioration of fatigue resistance. This is supported by observations of transgranular fracture in vacuum and intergranular fracture in air. In contrast, creep is a greater contributor to the deterioration in fatigue performance of N18 (as indicated by the intergranular failure modes observed in vacuum). An apparent activation energy analysis is able to provide further insight into the underlying mechanisms of fatigue crack propagation under creep–oxidation–fatigue conditions in these two alloys.

Dynamic Kinematic Responses of Female Volunteers in Rear Impacts and Comparison to Previous Male Volunteer Tests

Objectives: The objective was to quantify dynamic responses of 50th percentile females in rear impacts and compare to those from similar tests with males. The results will serve as a basis for future work with models, criteria, and safety systems. Methods: A rear impact sled test series with 8 female volunteers was performed at velocity changes of 5 and 7 km/h. The following dynamic response corridors were generated for the head, T1 (first thoracic vertebra) and head relative to T1: (1) accelerations in posterior–anterior direction, (2) horizontal and vertical displacements, (3) angular displacements for 6 females close to the 50th percentile in size. Additionally, the head-to-head restraint distance and contact time and neck injury criterion (NIC) were extracted from the data set. These data were compared to results from previously performed male volunteer tests, representing the 50th percentile male, in equivalent test conditions. T-tests were performed with the statistical significance level of .05 to quantify the significance of the parameter value differences for the males and females. Results: At 7 km/h, the females showed 29 percent earlier head-to-head restraint contact time (p = .0072); 27 percent shorter horizontal rearward head displacement (p = .0017); 36 percent narrower head extension angle (p = .0281); and 52 percent lower NIC value (p = .0239) than the males in previous tests. This was mainly due to 35 percent shorter initial head-to-head restraint distance for the females (p = .0125). The peak head acceleration in the posterior–anterior direction was higher and occurred earlier for the females. Conclusions: The overall result indicated differences in the dynamic response for the female and male volunteers. The results could be used in developing and evaluating a mechanical and/or mathematical average-sized female dummy model for rear impact safety assessment. These models can be used as a tool in the design of protective systems and for further development and evaluation of injury criteria.

SU-E-T-108: EBT2 Film Based Dosimetry Incorporating Correction for Spatial-Temporal Dose Response Variation

Purpose: Implementation of radiochromic film, such as GafChromic EBT2 film, as a quantitative 2‐dimensional dosimeter requires an array of equipment calibrations and corrections. We have developed a holistic model‐based calibration/correction mechanism for radiochromic film dosimetry. Methods: One challenge of using radiochromic film is that most of the densitometry scanners in use are designed for qualitative, not quantitative use. We performed careful characterization and quantification of the systematic and random components of all temporal and spatial optical density variations. In the proposed workflow, the spatial‐dependent dose response is estimated in the calibration stage under a novel model‐based optimization framework. A benchmark calibration process has been developed for the full (optical density, space) calibration map. For improved robustness, a simplified model that assumes separability of spatial variation and dose dependence was developed. The corresponding QA tool utilizes a consistent correction principle and maps the observed pixel intensity value based on the estimated spatially varying calibration map. The developed method has been tested on seven plans (both IMRT and VMAT) and compared with commercial software correction results. Dosimetry accuracy was validated against EDR2 film by comparison with treatment planning system calculated dose distribution using 3%‐3mm gamma criterion.Results: Under equivalent test conditions, the proposed method achieves gamma passing rates with EBT2 that are comparable to or better than a correction method of a commercial counterpart. Such corroboration is consistent for both IMRT and VMAT plans under gamma tests Conclusions: We have developed a systematic approach to comprehensively calibrate and use EBT2 film, accounting for temporal and spatial dose response variations. Specifically, a formal generative model and an estimation methodology was developed to achieve good balance between measurement sensitivity and robustness. This process has been implemented with in‐house software. Research supported in part by AACR career development award.

Experimental and Modeling Approach to Decolorization of Azo Dyes by Ultrasound: Degradation of the Hydrazone Tautomer

Sonochemical bleaching of monoazo dyes C.I. Acid Orange 7 and C.I Acid Orange 8, which exist in their hydrazone forms in dye solutions, was investigated by irradiating 40 microM dye solutions using a 300 kHz emitter. It was found that the rate of bleaching was first-order with respect to the maximum absorption of the dye in the visible band and accelerated with increased acidity. Decolorization of Acid Orange 7 was slightly faster than that of Acid Orange 8 at equivalent test conditions. The oxidative degradation of Acid Orange 7 and Acid Orange 8 were modeled by means of density functional theory calculations. The adduct formation by hydroxyl radical attack to the carbon atom bearing the azo linkage was more preferred over the attack on the nitrogen atom. A competing reaction of hydrogen abstraction from the CH3 group in C.I Acid Orange 8 was found responsible for the difference in color removal rates.

Comparing New Theory with Prior Beliefs: Market Civilization and the Democratic Peace

Stuart Bremer counseled against the falsificationist convention of testing new models against the null hypothesis of no model. Instead, new models should be compared against prior beliefs, and theories should compete, whenever possible, on a field of equivalent test conditions. This article applies Stuart Bremer's notion of comparative theory testing by comparing a new model of contract norms with the prior institutionalist model of democratic peace. On a field of equivalent test conditions it is found that the hypothesis for contract norms (that the democratic peace is contingent upon economic development) is thousands of times more likely to be true than the hypothesis for institutionalist theory (that democracy pacifies all dyads regardless of economic conditions). Democracy appears to be a significant force for peace only in dyads that are above the median income: the richest 45%. The results indicate that scholars of war should update the widespread prior belief that democracy, alone, causes peace.

A Quantitative Index for Mar and Scratch Resistance of Materials for Automotive Glazing Applications and Quantitative Evaluation of Damages by Different Scratching Modes

To comprehensively evaluate mar/scratch resistance of a material in a specific application, introduction of a quantitative index is very useful. The index depends on the properties of the material as well as on the application environment. Study of the samples, which have been used in the application environment, investigating the application conditions and figuring out their equivalent laboratory test conditions, is a necessary first step. This is then followed by quantitative evaluation of damages made by different scratching modes. Then, such an index can be formed. This paper introduces the concept of the index and describes the procedure of obtaining the index, including a quantitative evaluation of damages made by different scratching modes.

Aided speech recognition in single-talker competition by elderly hearing-impaired listeners

This study examined the speech-identification performance in one-talker interference conditions that increased in complexity while audibility was ensured over a wide bandwidth (200–4000 Hz). Factorial combinations of three independent variables were used to vary the amount of informational masking. These variables were: (1) competition playback direction (forward or reverse); (2) gender match between target and competition talkers (same or different); and (3) target talker uncertainty (one of three possible talkers from trial to trial). Four groups of listeners, two elderly hearing-impaired groups differing in age (65–74 and 75–84 years) and two young normal-hearing groups, were tested. One of the groups of young normal-hearing listeners was tested under acoustically equivalent test conditions and one was tested under perceptually equivalent test conditions. The effect of each independent variable on speech-identification performance and informational masking was generally consistent with expectations. Group differences in the observed informational masking were most pronounced for the oldest group of hearing-impaired listeners. The eight measures of speech-identification performance were found to be strongly correlated with one another, and individual differences in speech understanding performance among the elderly were found to be associated with age and level of education. [Work supported, in part, by NIA.]

Monolithic miniaturized quartz microbalance array and its application to chemical sensor systems for liquids

We report on the design, fabrication, and application of novel monolithic miniaturized quartz microbalance (QMB) arrays. Up until now, almost all reported resonator arrays (often designated as electronic noses or electronic tongues, respectively, dependent on their application) are assembled from single QMBs. We fabricate arrays with up to 36 QMBs on a single AT-cut quartz blank. Mass sensitive devices based on AT-cut quartz resonators are suitable as (bio)chemical sensors. A frequency shift caused by mass accumulation on the sensor surface increases theoretically with f/sup 2/, hence the detection limits for the application as chemical sensors should be decreased with increasing frequency. Since the quality factor Q of a quartz crystal decreases with f, the frequency stability is reduced, thus limiting mass sensitivity. The mass sensitivity of resonators with different resonant frequencies was examined by means of electrochemical copper deposition on their surface. Subsequently, the manufactured resonators were coated with different layers (polystyrene, amyl-calix[8]arene, /spl beta/-cyclodextrine). In order to examine the applicability of such coatings as sensitive layers, their sensitivities to toluene in water were investigated. Moreover, arrays with up to four different resonant frequencies on one chip were fabricated for comparing the resonator behavior of the same coating at different frequencies. In another test setup, different layers were sprayed onto an array of microbalances having all the same resonant frequency. This allowed for comparing the different coating behavior under equivalent test conditions. Arrays were tested for viscosity measurement to find an optimum resonant frequency.

Computation of Unsteady Separated Flow Fields Using Anisotropic Vorticity Elements

A novel computational methodology to compute two-dimensional unsteady separated flow fields using a vorticity based formulation is presented. Unlike traditional vortex methods, the elements used in this method are designed to take advantage of the natural anisotropy of most external flows. These vortex elements are disjoint and of compact support. The vorticity is uniform over rectangular elements whose initial thickness is set by a diffusion length scale. The elements are a mathematical construction which enables the vorticity of the flow to be created and followed numerically, and the Biot-Savart integral to be performed. This integral specifies the associated velocity field. Since the vorticity of a single element is of finite extent, the velocity associated with an element is given by a nonsingular expression. Viscous diffusion effects are modeled using random walk and the advection term is computed by transporting the vorticity elements with the local velocity field. Consequently, this Lagrangian mesh continually evolves through time. Since pressure does not explicitly appear in the formulation, surface pressures are computed using a stagnation enthalpy formulation. These elements are used to compute vorticity production, accumulation, transport and viscous diffusion mechanisms for unsteady separated flow fields past a pitching airfoil. Dynamic stall vortex initiation and development were examined and compared with existing experimental data. Surface pressure data and integrated force coefficient data were found to be in excellent agreement with experimental data. Effects of geometry were provided with baseline calculations of the unsteady flow past an impulsively started cylinder. Both qualitative and quantitative comparisons with experimental data for equivalent test conditions establish the applicability of this approach to depict unsteady separated flow fields.

Alterations in the physiology of CO2 exchange in tomato plants grown in CO2-enriched atmospheres

Young, greenhouse-grown tomato plants were transferred to growth cabinets where they were maintained in normal air (0.03% CO2) or in air enriched to 0.1 or 0.5% CO2. CO2 enrichment increased net assimilation rate but decreased leaf area ratio. As a result, relative growth rate was greatest at 0.1% CO2 and was less in 0.5% CO2 than in 0.03% CO2. Gas exchange measurements were made on the third true leaf of plants from different CO2 regimes. They indicated that growth under conditions of CO2 enrichment affected photosynthesis at an early stage of leaf development (leaf plastochron index (PI) = 5) but not at a later stage (PI = 10.5). The effects were linked to changes in mesophyll resistance, not stomatal resistance. At PI = 5 and under equivalent test conditions of irradiance and CO2 concentration, net photosynthesis tended to be increased following growth in 0.1% CO2 but was decreased or unchanged by 0.5% CO2. Young leaves developed in 0.1% CO2 were less subject to photosynthetic inhibition by atmospheric oxygen and had low CO2 compensation points. CO2 enrichment also affected the activities of the enzymes ribulose-1,5-bisphosphate carboxylase and glycolic acid oxidase and the enzyme responses corresponded well with the gas exchange responses. The results indicate that photosynthetic adaptations may occur in response to the concentration of CO2 present during growth, and that enrichment to concentrations much above 0.1% CO2 may be detrimental to net photosynthesis and growth rate.

A Model for the Subjective Effects of Listener Echo on Telephone Connections

Any appreciable listener echo on telephone lines is perceived as undesirable, and considerable effort is expended to hold echo to acceptable levels. To provide a basis for appropriately controlling listener echo, a series of four subjective tests was conducted at Bell Laboratories to obtain subjective evaluations of the effects of listener echo on telephone transmission quality. The subjective tests included conditions in which the listener echo-path loss was flat or frequency-shaped by selective filtering. The test results showed that subjective opinions for conditions with the same singing margin (minimum value of echo-path loss) were highly dependent on the frequency shaping. A weighted echo-path loss (WEPL) is defined to provide a weighting on the frequency-shaped test conditions so that subjectively equivalent test conditions have approximately the same levels of WEPL. The results of these subjective tests are used to formulate a model of subjective opinion for use in network planning studies. The resulting listener echo opinion model is incorporated into an existing transmission rating model which encompasses loss, noise, and talker echo. Objectives are proposed for listener echo based on WEPL.