Dilatometry of Steel for the Production of 5.56 mm Calibre Rifle Barrels

During high rates of fire, the bore of the firearm barrel is exposed to high temperatures. This exposure induces structural changes in the barrel material, which is especially significant for the substrate of the galvanic chrome plating. The alloy steel grades used currently for firearm barrels, when exposed to heating above the ferrite stability limits, develop a phase transition with a discrete negative change in the material volume, which results in typical crazing in the bore. This effect is destructive to the galvanic chrome plating, leading to a loss of adhesion, which reduces the ballistic performance of the firearm, especially its muzzle velocity. This can be prevented by manufacturing barrels from steels having a limited range of phase transitions. The primary method for determining the presence of distinct volume changes in steel due to phase transition is dilatometry over a wide temperature range, which includes the interval within which the barrel bore is heated. This paper presents the dilatometry results for four steel grades, which included a steel grade currently used for firearm barrels, and an analysis of the effects of phase transition on the degradation of the barrel bore.

Multiscale modeling of ferroelectrics with stochastic grain size distribution

Macroscopic properties of ferroelectrics are controlled by processes on the microscale, in particular the switching of crystal unit cells and the movement of domain walls, respectively. Besides these microscopic levels, the grains of a polycrystalline material constitute the mesoscopic scale. Interactions of grains with statistically distributed orientations, as a consequence of mechanical and electrostatic mismatch, give rise to for example, residual stress which in turn affects domain switching. A multiscale modeling thus has to incorporate at least three interacting scales. In this context, the condensed method has recently been elaborated as an efficient tool with low computational cost and effort of implementation. It is extended toward statistical distributions of grain sizes in a representative material volume element and amended with regard to the modeling of domain evolution. Each of the few parameters of the constitutive approach has a unique physical meaning and is adapted to available experimental values of macroscopic quantities of barium titanate taken from various sources.

Coupled dynamics and evolution of primordial and recycled heterogeneity in Earth’s lower mantle

The nature of compositional heterogeneity in Earth’s lower mantle remains a long-standing puzzle that can inform about the long-term thermochemical evolution and dynamics of our planet. Here, we use global-scale 2D models of thermo- chemical mantle convection to investigate the coupled evolution and mixing of (intrinsically-dense) recycled and (intrinsically- strong) primordial heterogeneity in the mantle. We explore the effects of ancient compositional layering of the mantle, as motivated by magma-ocean solidification studies, and of the physical parameters of primordial material. Depending on these physical parameters, our models predict various regimes of mantle evolution and heterogeneity preservation over 4.5 Gyrs. Over a wide parameter range, primordial and recycled heterogeneity are predicted to co-exist with each other in the lower mantle of Earth-like planets. Primordial material usually survives as mid-to-large scale blobs (or streaks) in the mid-mantle, around 1000-2000 km depth, and this preservation is largely independent on the initial primordial-material volume. In turn, recycled oceanic crust (ROC) persists as large piles at the base of the mantle and as small streaks everywhere else. In models with an additional dense FeO-rich layer initially present at the base of the mantle, the ancient dense material partially survives at the top of ROC piles, causing the piles to be compositionally stratified. Moreover, the addition of such an ancient FeO-rich basal layer significantly aids the preservation of the viscous domains in the mid-mantle. Finally, we find that primordial blobs are commonly directly underlain by thick ROC piles, and aid their longevity and stability. Based on our results, we propose an integrated style of mantle heterogeneity for the Earth, involving the preservation of primordial domains along with recycled piles. This style has important implications for early Earth evolution, and has the potential of reconciling geophysical and geochemical discrepancies on present-day lower-mantle heterogeneity.

Carbon Impact and Cost of Mass Timber Beam–Column Gravity Systems

The need to lower the embodied carbon impact of the built environment and sequester carbon over the life of buildings has spurred the growth of mass timber building construction, leading to the introduction of new building types (Types IV-A, B, and C) in the 2021 International Building Code (IBC). The achievement of sustainability goals has been hindered by the perceived first cost assessment of mass timber systems. Optimizing cost is an urgent prerequisite to embodied carbon reduction. Due to a high level of prefabrication and reduction in field labor, the mass timber material volume constitutes a larger portion of total project cost when compared to buildings with traditional materials. In this study, the dollar cost, carbon emitted, and carbon sequestered of mass timber beam–column gravity system solutions with different design configurations was studied. Design parameters studied in this sensitivity analysis included viable building types, column grid dimension, and building height. A scenario study was conducted to estimate the economic viability of tall wood buildings with respect to land costs. It is concluded that, while Type III building designations are the most economical for lower building heights, the newly introduced Type IV subcategories remain competitive for taller structures while providing a potentially significant embodied carbon benefit.

A Numerical Study on 3D Printed Cementitious Composites Mixes Subjected to Axial Compression

Aptly enabled by recent developments in additive manufacturing technology, the concept of functionally grading some cementitious composites to improve structural compression forms is warranted. In this work, existing concrete models available in Abaqus Finite Element (FE) packages are utilized to simulate the performance of some cementitious composites numerically and apply them to functional grading using the multi-layer approach. If yielding good agreement with the experimental results, two-layer and three-layer models case combinations are developed to study the role of layer position and volume. The optimal and sub-optimal performance of the multi-layer concrete configurations based on compressive strength and sustained strains are assessed. The results of the models suggest that layer volume and position influence the performance of multi-layer concrete. It is observed that when there exists a substantial difference in material strengths between the concrete mixes that make up the various layers of a functionally graded structure, the influence of position and of material volume are significant in a two-layer configuration. In contrast, in a three-layer configuration, layer position is of minimal effect, and volume has a significant effect only if two of the three layers are made from the same material. Thus, a multilayered design approach to compression structures can significantly improve strength and strain performance. Finally, application scenarios on some structural compression forms are shown, and their future trajectory is discussed.

Passive Sensing of Electromagnetic Signature of Roadway Material for Lateral Positioning of Vehicle

Autonomous vehicles (AV) and advanced driver-assistance systems (ADAS) offer multiple safety benefits for drivers and road agencies. However, maintaining the lateral position of an AV or a vehicle with ADAS within a lane is a challenge, especially in adverse weather conditions when lane markings are occluded. For significant penetration of AV without compromising safety, vehicle-to-infrastructure sensing capabilities are necessary, especially during severe weather conditions. This research proposes a method to create a continuous electromagnetic (EM) signature on the roadway, using materials compatible with existing paving materials and construction methods. Laboratory testing of the proposed concept was performed on notched concrete-slab specimens and concrete prisms containing EM materials. An induction-based eddy-current sensor and magnetometers were implemented to detect the EM signature. The detected signals were compared to evaluate the effects of sensor height above the concrete surface, type of EM materials, EM-material volume, material shape, and volume of EM concrete prisms. A layer of up to 2 in. (5.1 cm) of water, ice, snow, or sand was placed between the sensor and the concrete slab to represent adverse weather conditions. Results showed that factors such as sensor height, EM-material volume, EM dosage, types of the EM material, and shape of the EM material in the prism were significant attenuators of the EM signal and must be engineered properly. Presence of adverse surface conditions had a negligible effect, as compared to normal conditions, indicating robustness of the presented method. This study proposes a promising method to complement existing sensors’ limitations in AVs and ADAS for effective lane-keeping during normal and adverse weather conditions with the help of vehicle-to-pavement interaction.

Application of 3D Roughness Parameters for Wear Intensity Calculations

In this paper, calculations of 3D parameter Vm (material volume) of surfaces with irregular roughness and comparison with experimental data were performed, with further application of this parameter in calculations of wear intensity. First, using Mountains Map software for profilometric measurements, 3D roughness processing and determination of material volume Vm at specific relative levels γ were performed. The next step was an additional analysis of the distribution of surface ordinates using a theoretical and experimental Laplace function. The given check confirmed that for mostly surfaces with irregular roughness the ordinate distribution corresponds to the normal Gaussian distribution law, but in cases when the asymmetry of the ordinate distribution function goes outside the permissible limits (|∆Ssk|> 10%), errors> 10 % occur. On this basis, the mathematical formula of the material volume Vm was derived, and the obtained calculations were compared with the measured values. The results showed that the calculated values of the parameter Vm were very close to the experimental data (|∆Vm|<10 %), while at the relative level γ=+3, errors occurred that was related to the deviation from the normal distribution law. It was concluded that the given parameter could be used in the calculations of linear wear intensity, knowing the relative level γ.

Coupled dynamics and evolution of primordial and recycled heterogeneity in Earth's lower mantle

The nature of compositional heterogeneity in Earth's lower mantle remains a long-standing puzzle that can inform about the long-term thermochemical evolution and dynamics of our planet. Here, we use global-scale 2D models of thermochemical mantle convection to investigate the coupled evolution and mixing of (intrinsically dense) recycled and (intrinsically strong) primordial heterogeneity in the mantle. We explore the effects of ancient compositional layering of the mantle, as motivated by magma ocean solidification studies, and of the physical parameters of primordial material. Depending on these physical parameters, our models predict various regimes of mantle evolution and heterogeneity preservation over 4.5 Gyr. Over a wide parameter range, primordial and recycled heterogeneity are predicted to co-exist with each other in the lower mantle of Earth-like planets. Primordial material usually survives as medium- to large-scale blobs (or streaks) in the mid-mantle, around 1000–2000 km depth, and this preservation is largely independent of the initial primordial-material volume. In turn, recycled oceanic crust (ROC) persists as large piles at the base of the mantle and as small streaks everywhere else. In models with an additional dense FeO-rich layer initially present at the base of the mantle, the ancient dense material partially survives at the top of ROC piles, causing the piles to be compositionally stratified. Moreover, the addition of such an ancient FeO-rich basal layer significantly aids the preservation of the viscous domains in the mid-mantle. Finally, we find that primordial blobs are commonly directly underlain by thick ROC piles and aid their longevity and stability. Based on our results, we propose an integrated style of mantle heterogeneity for the Earth involving the preservation of primordial domains along with recycled piles. This style has important implications for early Earth evolution and has the potential to reconcile geophysical and geochemical discrepancies on present-day lower-mantle heterogeneity.

Evaluation efficacy of amniotic membrane in the treatment of neonatal Extravasation: a pilot study

Introduction: Intravenous treatment exposes the neonates to Extravasation due to Fragile and small veins and the long period required for treatment. Extravasation is leakage of fluids, nutrition, or drugs from a peripheral intravenous which could cause tissue damage. Based on extravasated material, volume, and patient-related factors, the injured complications range from local irritation to skin necrosis and severe scar formation after the healing. Several methods have been used to control the complications of Extravasation. We used an Amniotic membrane, a biological dressing, for healing the wounds. Our object in this study is to examine whether can the amniotic membrane induce healing wounds following extravasations. Methods: This prospective 13-week single-arm clinical trial study was performed on five neonates from February 2020 till May 2021 in the children's medical center of Tehran University. Neonates with any gestational age and with the diagnosis of the wound due to Extravasation entered our study. Neonates with skin disorders and wound stages of 1 and 2 were excluded from the study. Established Wounds without necrosis and infection are treated with an amniotic membrane. The amniotic membrane covers the wound, and After 48 hours, the wound is rechecked. Five days after the first bandage, the amniotic membrane is replaced with a new one, and the sequence of removing the bandages is five to seven days until healing occurs. Results: An amniotic membrane was applied to the wounds and the average time for healing was 2.5 weeks. The average gestational age was 33.6 weeks. We did not report any adverse reaction, and healing was without scar formation. Discussion/Conclusion: Implementing an amniotic membrane for treating wounds due to Extravasation can be a new approach. This treatment route decreases graft requirement and can be implemented by expert nurses, so in remote NICUs, its usage is easy.