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High Tensile Steels such as AISI-4340 is extensively used steel in various engineering sectors such as aerospace, defense, automotive, heavy engineering and power sectors for components such as pinion housing, gears, shafts, connecting rods, propeller shafts, & landing gears of aerospace vehicles etc. Such component faces extensive wear at the contact areas during operation resulting in loss of performance leading to replacement. Directed energy deposition or laser cladding for refurbishment of such components can reduce the cost of replacement and can also be advantageous in countering environmental concerns. In this study, feasibility of using AerMet-100 alloy powder for refurbishment of AISI4340 steel was explored using laser cladding process. A 6 kW diode laser with 6 + 2 axes robot was used for the experimentation where laser clads were generated by melting and depositing the powder that was fed through a powder-feeding nozzle. AerMet-100 clads were found to have good compatibility with the substrate and defect free clads were generated. In order to homogenize the microstructure at Heat Affected Zone, a post-clad heat treatment (PCHT) at 470 °C for 1hr was carried out. The as-cladded microstructure shows lath martensite with retain austenite, whereas post clad heat-treated sample shows slightly reduced retained austenite. Micro-hardness evaluation revealed increased in clad hardness after PCHT due to formation of fine carbides. Micro-tensile test of Post heat-treated clad showed max Tensile stress of 1752 MPa compared to substrate 1240 MPa. It can be concluded that AerMet-100 material can be a potential candidate for repair and refurbishment of AISI4340 steel.

The shock and spall behavior of tempered AF9628, an ultra-high strength (UHSS) martensitic low-alloy carbon steel, is investigated using gun-driven, symmetric, planar impacts. The study utilized laser velocimetry to obtain transmitted wave velocity histories that were analyzed to obtain the Hugoniot Elastic Limit (HEL), the shock Hugoniot, and the spall strength. The work was limited to the stress range below 13 GPa (below the e phase transition), and an HEL of 2.35 GPa and a spall strength of 6.8 GPa are reported. The HEL and spall strength of AF9628 are both above the typical values for inexpensive low-alloy steels, and only slightly below those for a much more expensive Aermet steel. The dynamic compressive yield strength (as calculated from the HEL) is only slightly higher than the quasi-static compressive yield strength when compared using a similar yield assignment convention, indicating a small, but positive, value of strain-rate sensitivity. The Hugoniot for AF9628, US = 0.67uP + 5.01 km/s, is in good agreement with other low-alloy martensitic steels for which data is available, and distinctly different than the Hugoniot for ferritic steels. The Hugoniot extrapolates to a bulk sound speed significantly higher than what is measured at ambient conditions, an incongruity that is unusual among metals and that the authors attribute to the unsteady nature of the shock waves generated in this work. Finally, it is suggested that there may be a relationship between dynamic compressive yield strength (calculated from the HEL) and dynamic tensile failure strength (the spall strength).

In the operation of thermoelectric power plants, fossil fuels are burned, generating air pollutants such as carbon monoxide (CO), nitrogen oxide (NOX), particulate matter (PM), sulfur dioxide (SO2), and volatile organic compounds (VOCs). Accordingly, the objective of this study was to simulate the dispersion of atmospheric pollutants from the Borborema S.A thermal power plant, using the Aermod View program as a tool to evaluate the concentrations resulting from the simulation and to make comparisons with allowable levels according to current law. Thus, the emission sources of chimney air pollutants of a thermal power plant in 2016 were evaluated using the Aermod View, Aermet View, and WRPLOT View software. Regarding the pollutants generated, NOx values at 1 h showed NO2 concentration over the primary and secondary standards allowed by law, with a maximum concentration of 1680 μg/m3, about five times higher than the primary standard and eight times the secondary. The simulation indices for the concentrations of PM, SOx, NOx, and CO, even though they are appeared very low, except NO2 at 1 h, it was observed that these pollutants can affect the health of the local population, fauna and flora, in view of the process of bioaccumulation, which is inherent to organisms, which directly or indirectly absorb substances or chemical compounds.

Bu çalışma, özellikle kış mevsimlerinde yoğun havakirliliğinin yaşandığı Balıkesir ili için yapılmış ilk hava kalitesi modellemeçalışmasıdır. Balıkesiril merkezinde bulunan bir sanayi işletmesinden atmosferik karbonmonoksit (CO)salınımlarının kent merkezine olan olası etkileri mevcut meteorolojik ve yüzeytopoğrafya özellikleri dikkate alınarak incelenmiş ve CO salınımlarına ait yeryüzü konsantrasyonlarının dağılımlarınıgösteren haritalar AERMOD ile oluşturulmuştur.Eldeedilen sonuçlara göre, Balıkesir iliiçin uzun yıllık hakim rüzgar yönü Kuzey (N) ve Kuzey-Doğu (NE) yönlü olarak belirlenmiştir ve kaynaktanyayılan maksimum günlük 8 saatlik ortalama CO konsantrasyonu modelleme sonucunagöre 34,01 μg.m-3 olarak tahmin edilmektedir. Bu nedenle, tahminedilen CO seviyelerinin yasal sınırları aşmadığı ve şehir merkezine olumsuz biretkisinin olmadığı belirlenmiştir. Ayrıca incelenen kaynağa yakın kabuledilebilecek yerde tam teşekküllü bir hastanenin olması, yapılan çalışmayı dahaönemli bir hale getirmektedir. Modelleme sonucuna göre, kaynaktan salınanmaksimum günlük 8 saatlik ortalama CO konsantrasyonu yaklaşık 10 μg.m-3olarak tahmin edilmiş olup, bu değerin yine aynı yönetmelikte izin verilenyasal sınırları aşmadığı tespit edilmiştir. Çalışma sonuçlarının, halkın bilinçlendirilmesine katkısağlanması ve yerel otoriteye karar alma sürecinde öneriler sunulması da ayrıcaçalışma kapsamında önem arz etmektedir., This study is thefirst air quality modeling study for downtown Balikesir where intense airpollution levels are experienced during the winter seasons. The possibleeffects of atmospheric carbonmonoxide (CO) emissions from an industrialoperation in downtown Balikesir were examined by taking into consideration theexisting meteorological and surface topography characteristics and the mapsshowing the distributions of the ground level concentrations for CO releaseswere created by using the AERMOD.According to the results, the prevailing winddirection was determined as North (N) and North-East (NE) for Balikesirprovince, and the maximum daily 8-hour means of CO concentration emitted fromthe source was estimated as 34,01 μg.m-3 for the modeling study. Forthis reason, it has been determined that the modeled CO concentrations do notexceed the legal limits and there is no adverse effect on the downtown area. In addition, the fact that, there was a full-scaledhospital that was located nearby the source. The location of hospital complexmade the air quality modeling study more significant. According to the modelingresult, the maximum daily 8-hour means of CO concentration released from thesource was estimated to be about 10 μg.m-3 for the hospital area. Ithas also been determined that the modeled value for hospital does not exceedthe legal limits as states in the regulation. Within the scope of the study,the obtained results are also important due to contribution to raising publicawareness and also provide suggestions to local authority in decision-makingprocess.

The predicted flow behaviors of Aermet 100 steel were analyzed within a wide range of temperatures of 1,073 K–1,473 K and strain rates of 0.01 s–1–50 s–1 based on isothermal compression tests. Using the original Johnson Cook (JC) model and a modified Johnson Cook (MJC) model, the constitutive equations were constructed in the case of elevated temperatures. For both the JC and MJC, and the previously studied (Arrhenius-type model and double-multivariate nonlinear regression (DMNR)) models, their respective predictability levels were evaluated by contrasting both the correlation coefficient R and the average absolute relative error (AARE). The results showed that the prediction from the three models meet the accuracy requirement based on the experimental data, the only exception being the JC model. By comparing the predictability and numbers of material constants involved, the modified Johnson Cook model is regarded as an excellent choice for predicting the flow behaviors of Aermet 100 steel within the range being studied.

Carbon-bearing high Co-Ni steels, which have superior strength, reasonable ductility, and toughness, are crucial materials for load-bearing parts in the aerospace and defense industries. In this study, laser powder bed fusion (LPBF) was used to fabricate high-density ultrahigh-strength high Co-Ni steel (AerMet 340). The relationship between the microstructure and mechanical properties of LPBF steel samples built by varying the laser scan rates (200 mm/s, 400 mm/s, 800 mm/s) with laser power of 90W was investigated. Nearly defect-free carbon-bearing high Co-Ni steel with a relative density of 99.9% could be fabricated at the scan rate of 400 mm/s. The high Co-Ni steels have a fine columnar microstructure, evidence of rapid cooling during LPBF processing, with effective grain sizes of 1.13∼1.68 μm (martensite) and 8∼12% retained austenite. The fractions and average sizes of Mo-rich carbides increase at higher laser scan rate. The compressive yield strengths of the LPBF-built steels are 1621 MPa (200 mm/s), 1698 MPa (400 mm/s), and 1711 MPa (800 mm/s), respectively. The tensile properties of LPBF bulk sample were measured as 1208 MPa of yield strength (YS), 1791 MPa of ultimate tensile strength (UTS), and 4.5% of elongation. The UTS and strength-elongation combination obtained in this study is the highest level reported for LPBF as-built steels to date. The results of the yield strength prediction and calculation show that solid-solution and martensite with high dislocation density are major hardening mechanisms for the superior mechanical properties of LBPF carbon-bearing high Co-Ni steel.

The performance of the regulatory dispersion model AERMOD in simulating vehicle-emitted pollutant concentrations near-roadway using area or volume source representation of emissions and with different low wind options was assessed using the SF 6 tracer data from the General Motors (GM) Sulfur Dispersion Experiment. At downwind receptor locations, AERMOD, using either area or volume source emissions, can reasonably predict the tracer concentrations near the surface (0.5 m) but the model performance decreases at higher elevations (3.5m and 9.5m above the surface). For upwind receptors, using an area source representation leads to significant under-predictions due to AERMOD’s lack of treatment of lateral plume meander, but using volume source representation leads to over-predictions of upwind concentrations regardless of the low wind options for plume meander. Among the three low wind options currently available in AERMOD, best model performance is obtained with low wind option 3, which treats plume meander with a higher minimal standard deviation of the horizontal crosswind component (σ v,min = 0.3 m s −1 ), eliminates upwind component of dispersion and uses an effective lateral dispersion parameter (σ y ) to replicate centerline concentration. The optional adjustment of the surface friction velocity in the meteorological preprocessor AERMET does not lead to obvious improvements in predicted near-road concentrations for this application.

The mechanical properties and microstructure of the 3D-printed high Co–Ni secondary hardening steel fabricated by the laser melting deposition technique was investigated using a material testing machine and electron microscopy. A microstructure investigation revealed that the samples consist of martensite laths, fine dispersed precipitates, and reverted austenite films at the martensite lath boundaries. The precipitates are enriched with Co and Mo. Because the sample tempered at 486°C has smaller precipitates and a higher number of precipitates per unit area, it exhibits better mechanical properties than the sample tempered at 498°C. Although the 3D-printed samples have the same phase constituents as AerMet 100 steel, the mechanical properties are slightly worse than those of the commercial wrought AerMet 100 steel because of the presence of voids.

Ultra-high strength steels employed in safety-critical applications, such as AerMet®100 used in aircraft landing gear structures, are managed on very conservative rejection criteria for small defects and repair options are limited. A novel repair technique using laser cladding has recently been developed. In the present paper we report a study of the fatigue endurance of AerMet®100 steel components repaired by the laser cladding process, and a fracture mechanics based model to predict the fatigue endurance of repaired components. Three different types of samples were tested; baseline AerMet®100 sample with a small electro-discharge machining notch to initiate a crack, as-clad repaired, and as-clad repaired followed by heat treatment to relieve residual stresses. The specimens were subjected to cyclic loading under a special sequence consisting of constant amplitude segments at two different stress-ratios (ratio of minimum to maximum cyclic stress). The test results showed that the crack propagation lives from a common initial depth of 0.25 mm for the as-clad samples were significantly longer than the baseline samples by a factor of three to four. The longer life is attributed to the beneficial compressive residual stresses resulting from the repair process. The model predictions are found to correlate well with the results of quantitative fractography measurements from samples tested under variable amplitude cyclic loads.

This paper describes the design, simulation, development, and analysis of a Cross Floating Valve (CFV), an important instrument used in a cross float or pressure calibration system of pressure balances (PBs) to make the calibration process easy and time efficient. The design aspects of the CFV include the selection of proper materials and modeling of various necessary components of the CFV. For the piston design, 5 different materials, SS304, SS316, Aermet 340, SS440C, and AISI17-4PH were used. After the design, simulation studies were carried out using the ANSYS (Workbench R15.0) software to understand the behavior of stress, strain, and deformation. Out of the 5 materials thus used, the values of the factor of safety of 2 materials (SS304 and SS316) were found to be below expectations and hence were not used in the fabrication process. Among the rest of the 3 other materials (AISI17-4PH, SS440C, and Aermet 340) having a factor of safety within the expected limits, Aermet 340 was also ignored because of its high cost. Finally, AISI17-4PH and SS440C were used to fabricate the piston, the most important and critical component of the CFV. The final CFV thus developed was tested for its performance in the cross floating experiments with 2 different sets of PBs. The results thus obtained show that the use of CFV reduces the calibration time considerably which is approximately 30% (average time of increasing and decreasing orders of pressure) from the time taken in performing calibration without using CFV, which is a significant achievement.

In environmental impact assessment of coal plant, it is essential to determine the radius impact. This information can be used to determine the impacted area, which will significantly receive the pollution emitted from the stack for years. In this study, we use the American Meteorological Society - Environmental Protection Agency Regulatory Model (AERMOD) model, which is a regulated model in the USA and other countries. Five years hourly meteorological data for feeding AERMET model was obtained from MM5 re-analysis data. Terrain data was extracted from the SRTM30 satellite image and converted into DEM. The parameter to be considered in this study is Sulfur Dioxide (SO2), Nitrogen Dioxide (NO2), and Total Suspended Particle (TSP). The calculation shows that the pollutions tend to disperse in the south direction by the wind direction. NO2 is more disperse than SO2 and TSP. Calculation of impact radius indicates that concentration of all pollutants in annual average is below the national standard. For the case of the highest one hour average gives the radius impact of 18 km for NO2 and 9 km for SO2. For the case of the highest 24 hours, only NO2 gives value beyond the standard with an impact radius of 4.5 km. Calculation of TSP indicates that concentration is below the standard in all cases. The maximum concentration of all pollutants is detected 3 km south of the stack.

Climate is defined as the statistics of weather over a long period of time. Climate has a dynamic structure, and climate change is caused either by natural or anthropogenic effects. Meteorological parameters are routinely recorded by national weather stations. In this study, climate variability was analyzed in a mid-populated city in the middle of the Anatolian Peninsula. Humidity, temperature, precipitation, open surface evaporation, and solar radiation records over 57-year period from 1960 to 2016 were considered. The increase in temperature and solar radiation was obvious. The increase rates were 0.05 °C and 0.62 W/m2 for temperature and solar radiation, respectively. Relative humidity showed a declining trend from 64 to 53%. This study also aimed to evaluate the climate change of planetary boundary layer development, which influences air quality level. AERMET, which is the AERMOD meteorological preprocessor was exploited in order to simulate the planetary boundary layer height, and twice daily upper air soundings, wind speed, wind direction, ambient temperature, and cloud cover have been used as minimum required parameters. The complete meteorological data available were between 2006 and 2016; for that reason, the boundary layer was calculated for 11 years. The determined average boundary layer height was 1018 m in 2006 and was reduced to 889 m in 2016. © 2019, Springer Nature B.V., The authors greatly acknowledge Turkish State Meteorological Service for providing the extensive data set of Aksaray weather records.

The microstructure and mechanical properties of ultrahigh strength Aermet 100 steel tempered at five different temperatures in the 472–492 °C range have been studied. The results show that the mechanical properties of Aermet 100 steel are sensitive to the tempering temperature; especially at the temperature of 482 °C, in which significant changes can be observed. At 482 °C, the strength of Aermet 100 steel sharply decreases by 70–100 MPa when the tempering temperature increases by only 5 °C. This is mainly due to the growth of M2C carbide at relatively high tempering temperature that can greatly decrease its interface strengthening effect. In addition to strength, the plasticity and fracture toughness of Aermet 100 steel obviously increase at 482 °C when compared with lower tempering temperatures. The rising amplitudes of elongation and fracture toughness can reach 1.7% and 30 MPa m1/2 respectively. This is attributed to the reverted austenite film precipitated at 482 °C. For one respect, the existence of austenite film between lath martensite can reduce the local stress concentration and the chance of microcrack formation in Aermet 100 steel during deformation, which is responsible for the obvious increase of plasticity. For another respect, the excellent softness, toughness and stability of reverted austenite prompt the advancing crack to divert, branch and blunt or appear “zigzag” route, which results in an increase in the fracture toughness. Aermet 100 steel can achieve the optimum combination of strength, plasticity and toughness at the tempering temperature of 482 °C, which has the yield strength of 1845 MPa, the elongation of 12.9% and the fracture toughness of 113 MPa m1/2.

The effect of laser cladding on the fatigue and fracture behavior under variable amplitude loading is a major consideration for the development of laser cladding process to repair high value complex fatigue critical aerospace military components, that otherwise would be replaced. The selected material, AerMet®100, is a widely used ultra-high strength steel in current and next generation aerospace components, such as landing gears. Laser cladding was performed using AerMet® 100 powder on AerMet® 100 fatigue substrate specimens. No micro-cracking and very little porosity were observed in the clad layer. The fatigue tests were performed under variable amplitude loading with a maximum stress of 1000 MPa. Residual stress, microstructure, and hardness, was also evaluated. Both the as-clad and post-heat treated (PHT) samples were compared to a baseline sample with an artificial notch to simulate damaged condition. Results show that laser cladding significantly improves fatigue life, as compared to the baseline sample with a notch. However, the fatigue life of the as-clad sample is lower as compared to a baseline sample without a notch. A compressive residual stress of 300–500 MPa was observed in the clad region and HAZ. The fracture modes in the as-clad specimen consisted mainly of tearing topology surface and some regions of decohesive rupture through the columnar austenite grains. The PHT condition however was not effective in improving the fatigue life. The fracture modes showed mainly decohesive rupture, and as a consequence, reduced the fatigue life.

Isothermal compression tests were conducted on A100 steel using a Gleeble 1500 thermal simulator at a temperature range of 900–1,200°C and strain rate range of 0.001–3 s−1. Results show that the A100 steel has higher strength than the Aermet 100 steel at high temperatures. Constant values, such as A, α, and n, and activate energy Q were obtained through the regression processing of the stress–strain data curves under different strains. A set of constitutive equations for A100 steel was proposed by using an Arrhenius-type equation. The optimum processing craft ranges for A100 steel based on the analysis of the hot working diagram and deformation mechanism are as follows: temperature range of 1,000–1,100°C and strain rate range of 0.01–0.1 s−1. The average grain size within this working range is 7–22.5 μm.

Bu çalışma, özellikle kış mevsimlerinde yoğun hava kirliliğinin yaşandığı Balıkesir ili için yapılmış ilk hava kalitesi modelleme çalışmasıdır. Balıkesir il merkezinde bulunan bir sanayi işletmesinden atmosferik karbonmonoksit (CO) salınımlarının kent merkezine olan olası etkileri mevcut meteorolojik ve yüzey topoğrafya özellikleri dikkate alınarak incelenmiş ve CO salınımlarına ait yeryüzü konsantrasyonlarının dağılımlarını gösteren haritalar AERMOD ile oluşturulmuştur. Elde edilen sonuçlara göre, Balıkesir ili için uzun yıllık hakim rüzgar yönü Kuzey (N) ve Kuzey-Doğu (NE) yönlü olarak belirlenmiştir ve kaynaktan yayılan maksimum günlük 8 saatlik ortalama CO konsantrasyonu modelleme sonucuna göre 34,01 μg.m-3 olarak tahmin edilmektedir. Bu nedenle, tahmin edilen CO seviyelerinin yasal sınırları aşmadığı ve şehir merkezine olumsuz bir etkisinin olmadığı belirlenmiştir. Ayrıca incelenen kaynağa yakın kabul edilebilecek yerde tam teşekküllü bir hastanenin olması, yapılan çalışmayı daha önemli bir hale getirmektedir. Modelleme sonucuna göre, kaynaktan salınan maksimum günlük 8 saatlik ortalama CO konsantrasyonu yaklaşık 10 μg.m-3 olarak tahmin edilmiş olup, bu değerin yine aynı yönetmelikte izin verilen yasal sınırları aşmadığı tespit edilmiştir. Çalışma sonuçlarının, halkın bilinçlendirilmesine katkı sağlanması ve yerel otoriteye karar alma sürecinde öneriler sunulması da ayrıca çalışma kapsamında önem arz etmektedir. This study is the first air quality modeling study for downtown Balikesir where intense air pollution levels are experienced during the winter seasons. The possible effects of atmospheric carbonmonoxide (CO) emissions from an industrial operation in downtown Balikesir were examined by taking into consideration the existing meteorological and surface topography characteristics and the maps showing the distributions of the ground level concentrations for CO releases were created by using the AERMOD.According to the results, the prevailing wind direction was determined as North (N) and North-East (NE) for Balikesir province, and the maximum daily 8-hour means of CO concentration emitted from the source was estimated as 34,01 μg.m-3 for the modeling study. For this reason, it has been determined that the modeled CO concentrations do not exceed the legal limits and there is no adverse effect on the downtown area. In addition, the fact that, there was a full-scaled hospital that was located nearby the source. The location of hospital complex made the air quality modeling study more significant. According to the modeling result, the maximum daily 8-hour means of CO concentration released from the source was estimated to be about 10 μg.m-3 for the hospital area. It has also been determined that the modeled value for hospital does not exceed the legal limits as states in the regulation. Within the scope of the study, the obtained results are also important due to contribution to raising public awareness and also provide suggestions to local authority in decision-making process.

Some upper air atmospheric parameters measured during period of 2011-2016 by means of radiosonde located at Hasanuddin International Airport were examined for characterization of boundary layer over Makassar, Indonesia. These data, combined with surface atmospheric parameters were used to calculate some boundary layer parameters using AERMET model which based on Monin-Obukhov similarity theory. The obtained Monin-Obukhov length which reflecting atmospheric stability then converted into traditional Pasquill-Gifford stability classification. Examination of wind characteristics of wind showing clearly their dependence of the day, season and height. Winds dominantly flows from the southeast during the daytime with the relatively larger velocity and from the northwest with smaller velocity during the nighttime. Interpretation of monin-obukhov length using Pasquill-Gifford stability classification showing that the atmosphere was dominantly unstable during the daytime and dominantly stable during the nighttime. These atmospheric stabilities were also varied during seasons. The height of convective boundary layer (CBL) was start to rise in the morning and reaching its maximum in the afternoon (18:00) at the mean value of 2 km. Meanwhile, the height of mechanical boundary layer (MBL) during the day time forming parabolic curve with its maximum value of 1.2 km at noon. These indicated that any released pollution from the stack will be less dispersed during the nighttime due to the fact of lower mixing height, lower wind speed, atmosphere become more stable, and it dispersed in different direction compare to the daytime.

The present work is part of the research project that aims to create an automated system for the evaluation of air pollution and odour for CMPC CELULOSE RIOGRANDENSE. Initially, three different ways of initializing the CALPUFF model (one of the models under evaluation to compose the system) were evaluated. The results when compared with observational data on air quality suggest the need for a validation of the boundary conditions and turbulent scale parameters in the hourly time representation when CALPUFF is the model being used. The choice was not random, but based on three quantities that impose physical affinity to micrometeorological data. The surface roughness, the albedo and the Bowen ratio. Changes in these quantities were imposed during pre-processing of AERMET, which established the quantities of interest in a simulation of dispersion of pollutants. After this alternative the results become more representative for the atmospheric dispersion process. The monthly and annual representation of the CALPUFF model is satisfactory without validation procedure.

This study compares MM5 and WRF modeled upper air and surface wind speed and direction with observations from two standard meteorological stations locat;ed in areas characterized by either flat or complex terrain. Additionally, we evaluate the boundary layer height calculated by AERMET VIEW Upper Estimator. The upper air wind speed predictions of MM5 (but not of WRF) met all the acceptance criteria. In contrast, WRF surface wind predictions were mostly in better agreement with the observations than those of MM5, with a clear advantage for the 12 km grid resolution over the 3 km grid resolution. Modeled wind fields over complex terrain were less accurate than over flat terrain. Based on these results we conclude that in the absence of measured on-site meteorological data, WRF surface wind field predictions are expected to provide more reliable pollutant dispersion estimations and to propagate the estimation uncertainties to a lesser extent than MM5 surface wind field predictions, in particular for flat terrain scenarios.

AerMet 100 exhibits excellent mechanical properties with both high yield strength and excellent ductility. Understanding the dynamic mechanical behavior of the material should clear the road for wider application of AerMet 100 as critical mechanical parts serving in extreme mechanical conditions. In this paper, the strain rate dependency of AerMet 100 is investigated by using Split-Hopkinson pressure bar (SHPB) and also compared with its quasi-static counterpart. Based on the experiment results, a simplified Johnson–Cook model is established to describe the strain rate dependent behaviors and is proved to perform better than Cowper–Symonds model. The validation of the suggested constitutive model is embedded in the finite element analysis and can well repeat the strain wave observed from experiment results. Furthermore, the impact fracture toughness of AerMet 100 is also studied both numerically and experimentally. Finally, a thin-walled tube made of AerMet 100 is numerically simulated and the excellent crashworthiness is proven. Results may enlighten the understanding of dynamic mechanical behavior of AerMet 100 and provide fundamental experiment data for its future engineering applications. Keywords: AerMet 100, Strain rate effect, Constitutive behavior, SHPB method, Numerical simulation

In this paper, we present a numerical model to study pollutant dispersion in the atmospheric boundary layer (ABL). The model accounts for the mechanisms of advection by the mean wind in the horizontal direction, turbulent diffusion in the vertical direction to ground surface, dry deposition, and radioactive decay. More importantly, the model is capable of accounting for the evolution of the ABL structure over a diurnal cycle by considering parameterizations for the wind-speed and eddy-diffusivity profiles that depend on the atmospheric stability condition, which in turn undergoes dramatic changes throughout the day. To solve the resulting advection–diffusion equation, we propose a numerical method based on a stabilized finite element formulation. After validating the numerical model by simulating classical experiments and comparing its predictions with those available in literature, we study the dispersion of a pollutant during a full diurnal ABL cycle with the meteorological parameters generated by AERMET for a 24-h period on a 1-h basis.

Air quality in most parts of Kay County is good and unlikely to cause major health problems. However, Kaw Nation wants to know if the concentration of Particulate matters (PM2.5) and Sulfur dioxide (SO2) released from power plants, refinery and carbon black plant in Oklahoma reaches the Tribal land at Kanza Travel Plaza, Braman, Kay Co. Oklahoma. Kanza Travel Plaza is located in the north central Oklahoma 22 miles Northwest of Ponca City at a latitude of 36.9395 degrees North and longitude of -97.3453 degrees West. In order to estimate the concentration of PM2.5 and SO2 that reaches the Tribal land, Kaw Nation run the U.S. Environmental Protection Agency regulatory air quality model called AERMOD (Version 15181). AERMOD is a steady state plume model that measures dispersion of gases and particulate matters from the source to the point of impact within source radius. The study sites are flat and rural conditions with less complex terrain. Meteorological data representative of the study area was preprocessed using AERMET program. AERMET prepares hourly surface data and upper air data. The hourly surface data was obtained from Station #3965 (Stillwater Regional), while the upper air data was obtained from Station #3948 (Norman). The Building parameters such as height and length were processed using the building profile called BPIB. To calculate the concentration of PM2.5 and SO2 air pollutants released from the coal power plant the Gaussian air molding (AERMOD) used Control, Source, Receptor, Metrological and Output pathways. The AERMOD result indicates at least 19-26% of PM2.5 and SO2 released from the stacks of the power plants, refinery and carbon black plant into the atmosphere reaches the Tribal land. Based on the Gaussian air modeling (AERMOD and BAM 1020 Continuous Air monitor) less than 12 µg/m3 of pollutant has been captured that falls within the attainment zone as per the National Ambient Air Quality Standards (NAAQS).

Distributed power generation, located close to consumers, plays an important role in the current and future power systems. However, its near-source impacts in complex urban environments are not well understood. In this paper, we focused on diesel backup generators that participate in demand response (DR) programs. We first improved the micro-environmental air quality simulations by employing a meteorology processor, AERMET, to generate site-specific boundary layer parameters for the Large Eddy Simulation (LES) modeling. The modeling structure was then incorporated into the CTAG model to evaluate the environmental impacts of diesel backup generators in near-source microenvironments. We found that the presence of either tall upwind or downwind building can deteriorate the air quality in the near-stack street canyons, largely due to the recirculation zones generated by the tall buildings, reducing the near-stack dispersion. Decreasing exhaust momentum ratio (stack exit velocity/ambient wind velocity) draws more exhaust into the recirculation zone, and reduces the effective stack height, which results in elevated near-ground concentrations inside downwind street canyons. The near-ground PM2.5 concentration for the worst scenarios could well exceed 100 μg m−3, posing potential health risk to people living and working nearby. In general, older diesel backup generators (i.e., Tier 1, 2 or older) without the up-to-date emission control may significantly increase the pollutant concentration in the near-source street canyons if participating in DR programs. Even generators that comply with Tier-4 standards could lead to PM hotspots if their stacks are next to tall buildings. Our study implies that the siting of diesel backup generators stacks should consider not only the interactions of fresh air intake and exhaust outlet for the building housing the backup generators, but also the dispersion of exhaust plumes in the surrounding environment.

Cutting tool temperature plays a key role in machining processes due to its effect on tool life and material removal rate, especially during high-speed machining of hard-to-cut materials. Several methods have been introduced to measure temperature of static objects in machining, such as workpiece in milling operation or cutting tool in turning operation. However, a few methods have been proposed to measure cutting tool temperature in milling process. In this article, we investigate cutting tool temperature in slot milling process. A wireless temperature measurement system with embedded thermocouple is developed to monitor and record cutting tool temperature. A series of experiments for slot milling of AerMet 100 steels are designed to measure cutting tool temperature with the wireless temperature measurement system. The cutting experiments are carried out under cutting speeds from 500 to 1750 m/min. The measurement results reveal that milling tool temperatures increase first and then decrease as cutting speed increases, and the peak temperature of milling tool appears at a critical cutting speed of about 1250 m/min. The effects of cutting speed on cutting tool temperature and tool wear are discussed.

In this research we aim to present a fast and semi-quantitative electrochemical method – based on cyclic voltammetry (CV) – to easily screen the H uptake of materials. We used Aermet 100, an ultrahigh-strength steel, in its as-quenched (martensitic) state and an aged state to investigate the H-desorption properties of different microstructures. The CV-based method clearly shows the influence of the alloying elements, the microstructure and the effect of hydrogen recombination poisons on the H uptake. The experiments indicate that a significant part of the uptake of hydrogen is due to (i) the presence of Ni as an alloying element and (ii) the presence of austenite that forms during the heat treatment.

This paper investigates grinding force and grinding temperature of ultra-high strength steel Aermet 100 in conventional surface grinding using a single alumina wheel, a white alumina wheel and a cubic boron nitride wheel. First, mathematical models of grinding force and grinding temperature for three wheels were established. Then, the role of chip formation force and friction force in grinding force was investigated and thermal distribution in contact zone between workpiece and wheel was analyzed based on the mathematical model. The experimental result indicated that the minimum grinding force and the maximum grinding force ratio under the same grinding parameters can be achieved when using a CBN wheel and a single alumina wheel, respectively. When the phenomenon of large grinding force and high grinding temperature appeared, the workpiece material would adhere locally to the single alumina wheel. Grinding temperature was in a high state under the effect of two main aspects: poor thermal properties of grinding wheel and low coolant efficiency. The predicted value of grinding force and grinding temperature were compared with those experimentally obtained and the results show a reasonable agreement.

The fatigue behaviour of an ultra-high strength steel (>1800 MPa) was evaluated to assess the potential of using laser cladding as a repair tool for such steels in aeronautical structural applications. AISI 4340 and AerMet 100 steel powder were used to clad over a grind-out region in an AISI 4340 steel substrate using a 2.5 kW ND:YAG laser. Post-clad heat treatment (PCHT) was also investigated. Results showed very poor tensile properties and significantly reduced fatigue life of the AISI 4340 as-clad with a very high hardness and brittle fracture in the clad and HAZ zone. Residual stress results showed a compressive residual stress in the clad region and tensile residual stress in the HAZ. Changing the alloy of the clad layer to AerMet 100 steel, as well as applying a PCHT process, showed promising results as the fatigue life was improved from that of the grind-out substrate.

In this paper, the results of a study aimed at understanding the specific role of microstructure on cyclic stress response, cyclic strain resistance, and cyclic stress versus strain response, deformation and fracture behavior of high strength alloy steel AerMet® 100 is presented and discussed. The cyclic strain amplitude-controlled fatigue properties of this ultra-high strength alloy steel revealed a linear trend for the variation of log elastic strain amplitude with log reversals-to-failure, and log plastic strain amplitude with log reversals-to-failure. Cyclic stress response revealed a combination of initial hardening for the first few cycles followed by stability for large portion of fatigue life before culminating in rapid softening to failure at the lower cyclic strain amplitudes and intermediate cyclic strain amplitudes and resultant enhanced cyclic fatigue life. Fracture characteristics of test specimens of this high strength alloy steel were different at both the macroscopic and fine microscopic levels over the entire range of cyclic strain amplitudes examined. Both macroscopic and fine microscopic observations revealed fracture to be essentially ductile with features reminiscent of locally occurring ductile mechanisms. The intrinsic microscopic mechanisms governing stress response, deformation characteristics, fatigue life and final fracture behavior are presented and discussed in light of the competing and mutually interactive influences of intrinsic microstructural effects, deformation characteristics of the microstructural constituents, cyclic strain amplitude and concomitant response stress.

Constant strain rate, constant velocity and Hopkinson Pressure Bar compression tests were carried out on AerMet 100 martensitic steel between 1130 °C and 1250 °C spanning strain rates from 0.01 s−1 to 4000 s−1. The results were used to generate a predictive flow stress model over the entire range of test conditions. The effect of initial austenite grain size on flow stress was found to follow the Hall–Petch relationship. This dependency was then removed through innovative heat treatments. The morphology of the flow stress curves were also dependent on mechanisms of microstructural evolution which were controlled by the test method, strain rate and temperature. Friction and adiabatic heating also had a major contribution. A novel method was proposed in order to define the flow stress, which was then used to determine the work hardening exponent of the Zener–Hollomon equation. It was found that a deviation from the linear trend was observed in Hopkinson Pressure Bar tests and reasons were given. An artificial neural network approach was used to determine a more accurate predictive flow stress model which included the effects of test method, temperature, stain rate and initial austenite grain size. The method showed that it was possible to predict the flow stress between 50 and 2000 s−1 where mechanical testing’s results were absent.

The stress corrosion crack (SCC) susceptibility of ultra-high strength steel AerMet 100 was investigated by slow strain rate technique (SSRT), tensile with polarization and surface analysis technique. The curves of tfCl/tfW-strain rate are divided into three regions: stress-dominated region, SCC-dominated region, and corrosion-dominated region, so as the curves of ɛfCl/ɛfW-strain rate and tm/tf-strain rate. The results of tensile tests with polarization show that the main SCC mechanism of AerMet 100 is anodic dissolution, which controls the corrosion process. The three regions have been discussed according to the relationship between the rate of slip-step formation and the rate of dissolution. Fracture appearances in different environments were analyzed by scanning electron microscopy (SEM). SCC fracture appears as a mixture of intergranular and dimples, while it is totally dimples in the inert environment. The ɛf becomes the parameter to predict tf because the relationship between ɛfCl/ɛfW and tfCl/tfW is a straight line for AerMet 100.

A detailed characterization of two dissimilar high-strength steels, SCMV and Aermet 100, joined by inertia friction welding (IFW)—a solid-state welding technique—was undertaken using high energy synchrotron X-ray diffraction and advanced electron microscopy in order to understand the dramatic hardness variation across such a weld. It was found that the severe high-temperature deformation in the thermomechanically affected zones (TMAZs) of the weld, stabilized ordered, and nanosized FeCo zones in Aermet 100 and about 12 to 14 vol pct austenite in SCMV (Ni equivalent 9 wt pct). The ordered FeCo zones in Aermet 100 resulted in exceptionally high hardness values of 700 to 725 HV. Very close to the weld line, the TMAZ of Aermet 100 also displayed a region with about 15 vol pct austenite, while in the parent material, 8 to 9 vol pct was typically observed. No indication of martensite was found in the weld region of Aermet 100. Ferrite texture analysis at different locations within the TMAZs on either side of the weld showed that SCMV develops a very strong α-fiber texture near the weld line and, in addition, a γ-fiber texture toward the heat-affected zone (HAZ), suggesting the presence of ferrite during welding near the weld line and recrystallization further away. The ferrite texture development in the TMAZ of Aermet 100 was relatively weak, suggesting that austenite is a dominant phase in the TMAZ during IFW.

Monitoring campaigns from different locations have recently shown how air concentrations of persistent semivolatile contaminants such as polychlorinated biphenyls (PCBs) often exhibit short-term (less than 24 h) variations. The observed patterns have been ascribed to different factors, such as temperature-mediated air-surface exchange and variability of planetary boundary layer (PBL) height and dynamics. Here, we present a new modeling approach developed in order to investigate the short-term variability in air concentrations of organic pollutants at a local scale. A new dynamic multimedia box model is supplied by a meteorological preprocessor (AERMET) with hourly values of air compartment height and wind speed. The resulting model is tested against an existing dataset of PCB air concentrations measured in Zurich, Switzerland. Results show the importance of such modeling approach in elucidating the short- and long-term behavior of semivolatile contaminants in the air/soil system.

The material micro-hardness is used to reflect the plastic deformation within the localized shear band and the segment of saw-tooth chip. A high strength alloy steel Aermet 100 is taken as the workpiece material. The saw-tooth chip roots are obtained by cutting operation. The material micro-harnesses along the shortly initiated localized shear band, across the shortly initiated localized shear band and fully developed localized shear band, and within the segment are examined and analyzed. The localized shear band initiation and propagation are revealed by a new proposed model. The results show the localized shear band initiates firstly at the tool tip end of the primary shear band, and consequently another localized shear nucleates at the free surface end of the primary shear band. These two localized shears propagate face to face until the whole localized shear band is formed.

This paper describes the methodology used to incorporate two numerical plume rise algorithms, one by Janicke and Janicke and another by Webster and Thomson, into the Lagrangian particle model LAPMOD. LAPMOD is fully interfaced with the diagnostic meteorological model CALMET, which is part of the widely used CALPUFF modeling system. LAPMOD can also use the meteorological input files produced with the AERMET meteorological processor of the US-EPA recommended model AERMOD. This paper outlines the theory behind the two plume rise algorithms and the details of their implementation in LAPMOD. The paper also provides the results of the evaluation of LAPMOD and its included plume rise algorithms against the well-known Indianapolis and Kincaid SF6 and SO2 field studies and tracer experiments. The performance of LAPMOD is successfully evaluated with the Model Evaluation Kit and compared with that of other air quality models.

Fluid catalytic cracking unit is of great importance in petroleum refining industries as it treats heavy fractions from various process units to produce light ends (valuable products). FCC unit feedstock consists of heavy hydrocarbon with high sulfur contents, and the catalyst in use is zeolite impregnated with rare earth metals, i.e., lanthanum and cerium. Catalytic cracking reaction takes place at elevated temperature in fluidized bed reactor generating sulfur-contaminated coke on the catalyst with large quantity of attrited catalyst fines. In the regenerator, coke is completely burnt producing SO2, PM emissions. The impact of the FCC unit is assessed in the immediate neighborhood of the refinery. Year-long emission inventories for both SO2 and PM have been prepared for one of the major petroleum refining industry in Kuwait. The corresponding comprehensive meteorological data are obtained and preprocessed using Aermet (Aermod preprocessor). US EPA approved dispersion model, Aermod, is used to predict ground level concentrations of both pollutants in the selected study area. Model output is validated with measured values at discrete receptors, and an extensive parametric study has been conducted using three scenarios, stack diameter, stack height, and emission rate. It is noticed that stack diameter has no effect on ground level concentration, as stack exit velocity is a function of stack diameter. With the increase in stack height, the predicted concentrations decrease showing an inverse relation. The influence of the emission rate is linearly related to the computed ground level concentrations.

The effects of chromium on the corrosion and the electrochemical behaviors of ultra high strength steels were studied by the salt spray test and electrochemical methods. The results show that ultra high strength steels remain martensite structures and have anodic dissolution characteristic with an increase of chromium content. There is no typical passive region on the polarization curves of an ultra high strength stainless steel, AerMet 100 steel, and 300M steel. However, chromium improves the corrosion resistance of the stainless steel remarkably. It has the slowest corrosion rate in the salt spray test, one order of magnitude less than that of AerMet 100 and 300M steels. With the increase of chromium content, the polarization resistance becomes larger, the corrosion potential shifts towards the positive direction with a value of 545 mV, and the corrosion current density decreases in electrochemical measures in 3.5wt% NaCl solutions. Because of the higher content of chromium, the ultra high strength stainless steel has a better corrosion resistance than AerMet 100 and 300M steels.

The electrochemical behaviors of ultra high strength steels, 300M and AerMet 100, with corrosion products which were formed during salt spray test were studied using potentiodynamic polarization curve, EIS, SEM, scan Kelvin probe (SKP) and Raman spectroscopy. The results show that the corrosion products on the steel 300M are γ-FeOOH and Fe(OH)3, and those on the steel AerMet 100 are β-FeOOH, Fe3O4 and γ-Fe2O3 after salt spray test. Because of the compact characterization, Fe3O4 and γ-Fe2O3 have a better protection property for substrate by hindering the permeation of O2 and Cl � . The corrosion potentials shift negatively and corrosion current densities become larger with increasing salt spray time, meaning a faster rate of anodic dissolution for these two steels. After salt spray test, the values of Kelvin potential for the two steels are 0.5—0.6 V positive than those before tests, and more uneven. For 300M, the corrosion resistance of rust layer becomes larger/smaller with the corrosion productions gathering/drapping on/from the samples. The electrochemical reaction for AerMet 100 is diffusion-controlled process and the value of Warburg impedence which expresses the diffusion-hindering effect becomes larger. The corrosion resistance and protection ability of corrosion products for steel AerMet 100 are better than those of steel 300M.

Some common high strength steels possess enough magnetostriction to serve as the active material in sensors, e.g. torque sensors, while simultaneously performing their usual structural role. The magnetization and magnetostriction of six common high strength steels have been measured as a function of stress. Measurements were made in a hydraulic load frame at compressive stresses of -1, -50, -100, and -150 MPa with fields up to 135 kA/m (1700 Oe). With two exceptions, all of the samples displayed ldquonormalrdquo strain-field curves. The exceptions were Maraging 300 steel whose magnetostriction was continuing to increase with stress even at -150 MPa and an SAE 4130 steel that showed an ldquoinverted V rdquo shape. B-H curves of all of the samples showed some small dependencies on stress but were otherwise unremarkable. The saturation magnetostrictions (muS = 1 times 10-6) and saturation magnetization (tesla) were: AerMet 100 [30 muS, 1.68 T]; HP 9-4-20 [23 muS, 1.68 T]; SAE 4130 [10 muS, 1.81 T]; Maraging 300 [32 muS (at -150 MPa), 1.67 T]; SAE 4340 [5 muS, 1.58 T]; SAE 9310 (heat treatment I) [10 muS, 1.77 T]; and SAE 9310 (heat treatment II) [12 muS, 1.82 T]. Details of the heat treatments are given.

We examine the efficacy of two methods commonly used to estimate the vertical turbulent fluxes of momentum and sensible heat from routinely observed mean quantities in the surface layer under stable stratification. The single-level method uses mean wind speed and temperature measurements at a single height, whereas the two-level method uses mean wind speed measurements at a single height and mean temperature measurements at two heights. These methods are used in popular meteorological processors such as the U.S. Environmental Protection Agency approved AERMET and CALMET to generate inputs for dispersion simulations. We use data from a flux station of the U.K. Met Office at Cardington for comparison. It is found that the single-level method does not describe the flux variation in the weakly stable regime at all, because of its assumption that the temperature scale, i.e. the ratio of the kinematic sensible heat flux to the friction velocity, is constant, which is plausible only under strongly stable conditions. On the other hand, the two-level method provides a physically realistic variation of the fluxes with stability, but the required temperature measurements at two levels are usually not available on a routine basis. If measurements of the standard deviation of temperature are also available, in addition to the mean temperature at a single level, then they can be usefully employed in a third (single-level) method, with the consequence that the computed fluxes are very similar to those obtained from the two-level method. An improvement to the original single-level method is considered, and flux calculations under low wind conditions are also discussed.

The welding of dissimilar alloys is seen increasingly as a way forward to improve efficiencies in modern aeroengines, because it allows one to tailor varying material property demands across a component. Dissimilar inertia friction welding (IFW) of two high-strength steels, Aermet 100 and S/CMV, has been identified as a possible joint for rotating gas turbine components and the resulting welds are investigated in this article. In order to understand the impact of the welding process and predict the life expectancy of such structures, a detailed understanding of the residual stress fields present in the welded component is needed. By combining energy-dispersive synchrotron X-ray diffraction (EDSXRD) and neutron diffraction, it has been possible to map the variations in lattice spacing of the ferritic phase on both sides of two tubular Aermet 100-S/CMV inertia friction welds (as-welded and postweld heat-treated condition) with a wall thickness of 37 mm. Laboratory-based XRD measurements were required to take into account the variation in the strain-free d-spacing across the weld region. It was found that, in the heat-affected zone (HAZ) slightly away from the weld line, residual stress fields showed tensile stresses increasing most dramatically in the hoop direction toward the weld line. Closer to the weld line, in the plastically affected zone, a sharp drop in the residual stresses was observed on both sides, although more dramatically in the S/CMV. In addition to residual stress mapping, synchrotron XRD measurements were carried out to map microstructural changes in thin slices cut from the welds. By studying the diffraction peak asymmetry of the 200-α diffraction peak, it was possible to demonstrate that a martensitic phase transformation in the S/CMV is responsible for the significant stress reduction close to the weld line. The postweld heat treatment (PWHT) chosen to avoid any overaging of the Aermet 100 and to temper the S/CMV martensite resulted in little stress relief on the S/CMV side of the weld.

The present study examines the strain-rate sensitivity of four high-strength, high-toughness steels at strain-rates ranging from 0.0002 s −1 to 200 s −1 : AerMet 100, modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A newly developed dynamic servohydraulic method was employed to perform tensile tests over this entire range from quasi-static to near split-Hopkinson or Kolsky bar strain-rates. Each of these alloys exhibits only modest strain-rate sensitivity. Specifically, the semi-logarithmic strain-rate sensitivity factor β was found to be in the range of 14–20 MPa depending on the alloy. This corresponds to a ∼10% increase in the yield strength over the 6-orders of magnitude change in strain-rate. Interestingly, while three of the alloys showed a concomitant ∼3–10% drop in their ductility with increasing strain-rate, the ES-1c alloy actually exhibited a 25% increase in ductility with increasing strain-rate. Fractography suggests the possibility that at higher strain-rates ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.

Cylinders and rings fabricated from AerMet ® 100 alloy and AISI 1018 steel have been explosively driven to fragmentation in order to determine the fracture strains for these materials under plane-strain and uniaxial-stress conditions. The phenomena associated with the dynamic expansion and subsequent break up of the cylinders are monitored with high-speed diagnostics. In addition, complementary experiments are performed in which fragments from the explosively driven cylinders are recovered and analyzed to determine the statistical distribution associated with the fragmentation process as well as to determine failure mechanisms. The data are used to determine relevant coefficients for the Hancock–McKenzie (Johnson–Cook) fracture model. Metallurgical analysis of the fragments provides information on damage and failure mechanisms.

Microstructural variation across inertia friction welded Aermet 100 (ultra-high strength secondary hardening steel) and SCMV (high strength low alloy Cr–Mo steel) has been studied. Retained austenite was mapped in two dimensions across the inertia friction welds using synchrotron-X ray diffraction. Microhardness testing and SEM were used to characterize the general microstructure variation across the weld line in the as-welded and post-weld-heat-treated (PWHT) conditions. Four distinct microstructural zones were observed for the as-welded condition in the heat-affected zone. Subsequent PWHT resulted in a reduction of the peak hardness on adjacent sides of the weld with all other areas increasing in hardness. These changes in hardness are explained based on tempering of the martensitic structure and precipitation reactions during PWHT.

The commercial materials forming package DEFORM-2D is used to model the inertia friction welding (IFW) process with particular reference to aero-engine mainline drive shafts. Both representative and predictive modelling techniques are presented, and models are described for the welding of identical and dissimilar material/geometry combinations. The range of material properties required for the models are discussed and details of the tests carried out to produce suitable material data are included. Case studies involving Inconel 718 and AerMet 100 are presented. The phase transformations in a high-strength aerospace steel are included in the model and their effects on residual stresses are presented. Temperature profiles are compared with experimental thermocouple measurements and the models are also compared with upset and rotational velocity data collected during welding. The DEFORM-2D software in conjunction with a friction law coded into a subroutine are shown to be suitable for modelling the IFW process between similar and dissimilar shaft materials. Results highlight the importance of the inclusion of the volume change associated with the martensite transformation on the residual stresses generated during the post-weld cooling of IFW joints.

The AERMET model is used to estimate hourly mixing heights during the Joint URBAN (2003) experiment in Oklahoma City, Oklahoma. AERMET is a simple 2-D model that requires only routine meteorological observations and an early morning atmospheric sounding to estimate convective boundary layer (CBL) growth. Estimated mixing heights are compared with observed mixing heights measured during Joint URBAN 2003. Observed CBL heights are derived from profiler data using a peak signal-to-noise ratio method. The method of deriving mixing heights from profiler data is validated using daily atmospheric sounding data. Estimated mixing heights using AERMET show good agreement with observations on days of varying temperature and cloud cover. AERMET was able to estimate the rapid boundary layer growth observed in the late morning and early afternoon hours during highly convective conditions. CBL heights of over 3000 m are observed in sounding data during the late afternoon. Estimated CBL heights of over 3000 m during the late afternoon agreed well with observations from the sounding and profiler data.

Fully hardened martensitic steel AerMet alloy 100 was nitrided using a newly developed technique known as high intensity plasma ion nitriding (HIPIN). A systematic study, using the experimental techniques of optical and scanning electron microscopy, microhardness measurement, and Rockwell C-scale (150 kg load) indentation was executed to determine the resulting case depth and hardness profile as affected by the processing parameters of ion energy, current density, process temperature and duration. It was observed that nitrogen diffused rapidly at the temperature range from 427 to 480 °C and a case depth up to 200 µm was obtained. The surface hardness after nitriding increased to HK200g = 800–900 from 600–700. However, the bulk hardness reduced slightly from Rc56 for the unnitrided to Rc55 upon nitriding even for a short duration of about 1 h. When the nitriding temperature was not too high (≤454 °C) and the duration was not too long (≤15 h), the bulk hardness remained within the range of Rc53–55. Further increase in temperature and duration resulted in significant reduction in the bulk hardness. Using simulated gear samples in the form of V-notch bars, the nitrided case depth was determined to be quite uniform around the entirety of the notch geometry. Considering the bulk hardness, surface sputtering, and nitride case depth, it appeared that nitriding at 454 °C for up to 15 h that produced a case depth of about 120 µm may be the optimal condition. From the experimental data, the diffusion coefficient and activation energy for nitrogen in AerMet 100 were determined to be D0 = 4.33 × 10−6 cm2 · s−1 and Ea = 0.488 eV, respectively. Based on the results of this study, the viability of the HIPIN technique has been demonstrated for the thermochemical processing of prototype components composed of AerMet 100 alloy steel.

Modern precipitation-hardened ultra-high-strength AERMET 100 steel (Fe-Co-Ni-Cr-Mo-C) is susceptible to severe transgranular hydrogen environment–assisted cracking (HEAC) in neutral 3.5 pct NaCl solution. The threshold stress intensity for HEAC, K TH , is reduced to as low as 10 pct of K IC , and the stage II subcritical crack growth rate, da/dt II, is up to 0.5 μm/s. Low K TH and high da/dt II are produced at potentials substantially cathodic, as well as mildly anodic, to free corrosion. However, a range exists at slightly cathodic potentials (–0.625 to –0.700 VSCE), where the crack growth rate is greatly reduced, consistent with reduced crack-tip acidification and low cathodic overpotential for limited H uptake. Short crack size (250 to 1000 μm) does not promote unexpectedly severe HEAC. High-purity AERMET 100 is susceptible to HEAC because martensite boundary trapping and high crack-tip stresses strongly enhance H segregation to sites that form a transgranular crack path. The stage II da/dt is H diffusion rate limited for all potentials examined. A semiquantitative model predicts the applied potential dependence of da/dt II using reasonable input parameters, particularly crack-tip H uptake reverse calculated from measured K TH and a realistic critical distance. Modeling challenges remain.

We present a thermal explosion (cookoff) model for an HMX-based plastic bonded explosive (LX-10). The thermal–chemical–mechanical response of LX-10 is modeled based on the measurements from the scaled thermal explosion experiment (STEX) at the Lawrence Livermore National Laboratory. Confined LX-10 is heated at a rate of 1 °C/h until an explosion is observed. The modeled cookoff problem is simulated by the Arbitrarily Lagrangian–Eulerian hydrocode (ALE3D) that can handle a wide spectrum of time scales that vary from a structural to a high speed shock physics time scale. In addition to a comprehensive model for energetic material, the confinement material namely an AerMet 100 steel is modeled as a Steinberg–Guinan material with a Johnson–Cook failure model with a statistical failure distribution. By using the size distribution data from the fragmentation experiment, the metal fracture and fragmentation due to an explosion are modeled. The explosion temperature is predicted to within 1°. Calculated wall strain provides violence associated with the thermal explosion process and agrees favorably with the measured STEX data.

Comparisons were made between field monitored and prognostic model generated meteorological parameters for source dispersion modeling in Chandrapur, India. The first set of meteorological fields was generated using field monitored data based on measured parameters of SODAR and Mini-sonde. The second set of meteorological fields was generated using a prognostic model MM5 version 3.6.1. AERMET meteorological preprocessor was used to determine derived parameters from monitored and modeled parameters. Wind speed, wind direction, temperature, surface heat flux and mixing height were estimated separately for the two fields. Wind speed observed from SODAR was higher than the model predicted value. Temperature data from the Mini-sound was compared to MM5 modeled data and it was observed that MM5 under predicted temperature by 7 °C. Statistical measures indicated poor performance of the model. Results indicated that the use of prognostic models for predicting meteorology to study air quality in a region must be calibrated to local boundary conditions. There is a need to enhance data nudging and validation of prognostic models for different climatic conditions.