Garments respond differently to four types of arc exposures. Moisture in arc-exposed garments can alter their appearance in ways not typically observed in standardized arc flash testing, such as ASTM ...F1959, IEC 61482-1-1, IEC 61482-1-2, or ASTM F2621. Color changes, which are commonly seen in garments exposed to standard tests, do not occur as expected when garments are moist. This information may be useful in accident investigation and hazard assessment. The four types of arc exposures described herein are presented as follows: radiated arc, ejected arc, arc-in-a-box, and "tracking" arc. Two of these arc exposures can be described as plasma rich, and the other two are only circumstantially plasma rich, depending on equipment configuration, duration, voltage, and fault current level. New methods to reduce arc hazards, such as blankets meeting ASTM F2676 and shields meeting ASTM F2522, and how they relate to potential arc exposures will also be discussed.
Plastic is ubiquitous in modern life, but most conventional plastic is non-biodegradable and accumulates as waste after use. Biodegradable plastic is a promising alternative to conventional plastic. ...However, biodegradable plastics must be thoroughly evaluated to ensure that they undergo complete degradation and have no adverse impact on the environment. We evaluated the degradation of biodegradable plastics during 18-week full-scale composting, and determined whether additives from the plastics are released upon degradation. Two biodegradable plastic films—one containing polybutylene co-adipate co-terephthalate (PBAT) and the other containing polylactic acid/poly-hydroxy−alkanoate (PLA/PHA)—were placed into meshbags and buried in the compost. Degradation was assessed by image analysis, scanning electron microscopy, Fourier-transformed infrared spectroscopy, electrophoretic mobility, δ13C isotope analyses, and single particle mass spectrometry of mulch fragments. The results showed >99% macroscopic degradation of PLA/PHA and 97% for PBAT film. Polymers in the biodegradable films degraded; however, micro- and nanoparticles, most likely carbon black, were observed on the meshbags. Overall, biodegradable plastics hold promise, but the release of micro- and nanoparticles from biodegradable plastic upon degradation warrants additional investigation and calls for longer field testing to ensure that either complete biodegradation occurs or that no long-term harm to the environment is caused.
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•Plastic pollution is a ubiquitous environmental problem.•Biodegradable plastic can help reduce plastic pollution.•Not all components in biodegradable plastics may degrade.•Non-biodegradable additives, such as carbon black, may be released upon degradation of plastic.
This study aims at investigating the influence of high stress triaxiality on the yield strength and ultimate tensile strength of commonly used structural steels (ASTM A36, ASTM A572 and ASTM A992). ...To this end, axisymmetrically notched steel specimens are designed to generate a range of stress triaxialities. Yield strength and ultimate tensile strength of notched steel specimens are then determined using engineering stress-strain curves obtained from uniaxial tensile testing of notched specimens. Yield strength and ultimate tensile strength of all three types of structural steels are found to increase linearly with increase in stress triaxiality of test specimens. Based on experimental and complimentary finite element results, predictive equations are proposed to estimate increased yield strength and ultimate tensile strength as a function of stress triaxiality in structural steels.
Thoracolumbosacral pedicle screw systems (TPSSs) are spinal implants commonly utilized to stabilize the spine as an adjunct to fusion for a variety of spinal pathologies. These systems consist of ...components including pedicle screws, rods, hooks, and various connectors that allow the surgeon to create constructs that can be affixed to a wide range of spinal anatomy. During the development and regulatory clearance process, TPSSs are subjected to mechanical testing such as static and dynamic compression bending per ASTM F1717, axial and torsional grip testing per ASTM F1798, and foam block pullout testing per ASTM F543. In this study, design and mechanical testing data were collected from 200 premarket notification (510(k)) submissions for TPSSs submitted to FDA between 2007 and 2018. Data were aggregated for the most commonly performed mechanical tests, and analyses were conducted to assess differences in performance based on factors such as component type, dimensions, and materials of construction. Rod material had a significant impact on construct stiffness in static compression bending testing with cobalt chromium rods being significantly stiffer than titanium rods of the same diameter. Pedicle screw type had an impact on compression bending yield strength with monoaxial screws having significantly higher yield strength as compared to polyaxial or uniplanar screws. Axial and torsional gripping capacities between components and the rods were significantly lower for cross-connectors than the other component types. The aggregated data presented here can be utilized for comparative purposes to aid in the development of future TPSSs.
•We propose a new simplified method to measure the albedo of limited extent targets.•The method measures the albedo of typical land covers with high accuracy.•The method can reliably measure the ...albedo of a target with different background albedo.•The proposed method can be used in place of the ASTM E1918-06.
Albedo is important in the research fields of atmospheric sciences, forestry, urban climatology, building energy sciences, and several others. Here we establish a new simplified method for measuring the albedo of limited extent targets in field. Back-to-back pyranometers are centered and leveled over the target to measure the incident radiation and the reflected radiation. A circular baffle with an aperture at the bottom is assembled around the lower pyranometer’s detector to make the detector receiving the reflected radiation from the target only. Measurement is calibrated by covering the target with a spectrally non-selective diffuse mask. We use the proposed method to measure the albedo of typical land covers; the measured results were then compared against the measured albedo attained using the ASTM E1918-06 standard. The comparison shows close agreements, indicating that the proposed method is reliable to measure the albedo of a limited extent target and can serve as a simplified alternative to ASTM E1918-06.
AbstractThe objectives of this study are (1) to investigate the microstructural changes in structural steels that are exposed to fire accidents; and (2) to understand their influence on post-fire ...mechanical properties. Specifically, three structural steels—ASTM A36, ASTM A572, and ASTM A992—are employed, and three post-fire mechanical properties—yield strength, ultimate tensile strength, and ductility—are determined. Structural steel specimens are subjected to high temperatures ranging from 500°C to 1,000°C for 1 h and are subsequently air-cooled. Post-fire mechanical properties of air-cooled specimens are determined using uniaxial tension tests. Metallographic specimens are prepared, and microstructural analysis is carried out. Changes in metallurgical phases are tracked, and the grain sizes of the corresponding metallurgical phases are evaluated as a function of exposed temperature. By observing the post-fire mechanical properties of steels along with the microstructural analysis, an increase in ferrite volume fraction and ferrite grain size clearly leads to a reduction in both the post-fire yield strength and ultimate tensile strength of ASTM A36 steels. The increase in ferrite grain size alone resulted in an increase in the ductility of ASTM A36 steels. Based on the results obtained in this study, multivariate linear regression equations are proposed to evaluate the post-fire yield strength of all three structural steels as a function of ferrite grain size and pearlite colony size. The results of this study will be useful to forensic engineers when evaluating the residual strength of fire-affected steel structures based on microstructures, especially when elevated temperature values are not available.
•A method for estimating CO2 generation rate by age is proposed.•Identified the trends and age segment points in CO2 generation rates from ages 5 to 70.•Described the individual differences in CO2 ...generation rates using body surface area.•Metabolic rate is the primary factor causing errors in CO2 generation rate estimation.•ASTM D6245-18′s method requires higher metabolic rate input as compensation.
In most applications of indoor CO2, such as building ventilation rate estimation and demand-controlled ventilation, the CO2 generation rate of building occupants is a crucial parameter. Currently, ASTM D6245-18 provides an estimation formula for the CO2 generation rate, but there are indications that its results tend to be underestimated. This paper utilized more than 7,200 sets of CO2 generation rate data from over 1100 participants aged 5 to 70 to propose a segmented regression model for estimating CO2 generation rates based on gender, age, and activity metabolism as independent variables. Based on the patterns of CO2 generation rate with age and metabolic rate, two critical age breakpoints were identified: 10/11 years for girls/boys entering puberty and 13/15 years for girls/boys entering the stable growth phase. The reliability of the established model was validated through literature-based data across various scenarios. The results revealed that using the activity intensity determined by the recommended metabolic rates in the ASHRAE Handbook, our estimations were closer to the experimental values compared to ASTM D6245-18, which required higher metabolic rates for compensation. The method in this paper requires only age, gender, and activity metabolic rate to estimate the mean CO2 generation rate for different occupants, offering a simple calculation approach for key parameters in CO2 applications within buildings.
The current state-of-the-art metal additive manufacturing (AM) process still cannot meet the high industry requirements in terms of surface roughness. In addition, there are limited ISO/ASTM ...standards on the post-processing of metal AM components. Considerable efforts have been made to close these current gaps and challenges for standardization. In this review, First, all the existing ISO/ASTM standards under the jurisdiction of ASTM Committee F42 on additive manufacturing technologies are briefly discussed. Second, two of the most promising additive manufacturing processes: powder bed fusion (PBF) and directed energy deposition (DED), as well as their common defects of AM components, are thoroughly reviewed. The build quality, surface finish characteristics, and dimensional integrity of the as-built AM components are still not satisfactory (i.e., Ra > 5 µm and Rz > 100 µm). Third, the review is focused on identifying potential solutions to surface-finish complex additive manufactured geometries and reduce the surface roughness to meet the industry requirements (i.e., Ra < 1 µm and Rz < 20 µm). Current state-of-the-art surface finishing techniques, their material removal mechanisms, process parameters, advantages, and limitations to post-process PBF components are discussed. The technical gaps and future perspectives in enhancing the surface quality of AM components are outlined.
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•Mg2Zr5O12 have been used for the first time as heterogeneous catalyst for transesterification reaction.•97.98% of FAME conversion was accomplished from kusum (Schleichera triguga) ...oil.•Catalyst can be reused up to seven cycles with conversion of >75%.•Optimization of transesterification reaction was carried by response surface methodology (RSM).
A heterogeneous catalyst, magnesium zirconate (Mg2Zr5O12) was synthesized by co-precipitation and was used for biodiesel production via transesterification. Kusum oil was used as a feedstock. Catalyst characterization was accomplished by TGA, XRD, ATR FTIR, SEM, and EDX. The parameters viz. particle size, zeta potential, BET surface area and basicity of the catalyst were also determined. Characterization of catalyst supports the formation of single phase Mg2Zr5O12 and the catalyst was able to catalyse the transesterification reaction for economically viable biodiesel production. Various reaction parameters such as molar ratio (methanol: oil), catalyst concentration and reaction time were optimized in presence of Mg2Zr5O12 by using Response Surface Methodology (RSM) based on Box-Behnken design. The catalyst was reusable up to seven runs with ∼75% conversion in the seventh run.
Maximum conversion of 97.98% FAME was obtained at 18:1 M ratio (methanol: oil), 2.5 wt% of catalyst at 65 °C temperature for 150 min. Physicochemical properties of FAME were also studied as per ASTM standard method.
In marine or coastal zones, the most harmful exposure for reinforced concrete structures to chloride ions. The ASTM C1556 chloride diffusion test (or its European equivalent NT BUILD 443) has been ...widely used as the most reliable testing method to assess the performance of concrete against chloride penetration. However, this test is time demanding and labour intensive. As a result, accelerated test ASTM C1202 (RCPT) is often preferred, providing fast and acceptable assessment of chloride penetrability of Ordinary Portland Cement Concrete. This study aimed to investigate the suitability of RCPT to assess the performance of Geopolymer Concrete (GPC) in chloride environment. The correlation between several GPC properties i.e. compressive strength, volume of permeable voids (VPV) and sorptivity and the chloride diffusion coefficient are examined. Results indicate that the compressive strength, the VPV and the sorptivity coefficient are not suitable indicators of the GPC performance. The ASTM C1202 standard RCPT failed to measure the charges passed through most of the GPCs tested. A modified version of RCPT using 10 V (as opposed to 60 V specified by standard ASTM C1202) is proposed in this paper, allowing to successfully measure the charges passed through all GPC samples using a wide range of binders. A good correlation was observed between modified ASTM C1202 and Standard ASTM C1556 test results. Performance-based recommendations are proposed in this paper. Both experimental results from this study and appropriate reference concretes from the literature were used to calibrate the modified ASTM C1202 and ASTM C1556 performance-based requirements for GPCs.
