Growth Behavior Research Articles

Interrelation between mechanical and electromagnetic radiation emission parameters with variable notch-width ratios under tensile fracture in silicon steel

Abstract The research investigates the effect of variable notch-width ratios on mechanical and electromagnetic radiation (EMR) parameters during the tensile fracture of silicon steel. The primary purpose is to comprehend the plastic deformation and crack propagation at an atomic level. The mechanical and EMR parameters chosen for analysis were correlated. The EMR energy release rate correlated well with the elastic strain energy release rate. The good fit between the EMR parameters and the plastic zone radius is a novel method to determine the crack growth behaviour of metals. A theoretical model of dislocation predicted the nature of EMR signals at fracture. A reasonable agreement between cross-slip energy with maximum stress at crack instability, the elastic strain energy release rate, and the EMR energy release rate will help assess the dislocation dynamics of metals. The EMR amplitude was sensitive to varying strain rates.

Aspergillus nidulans cell wall integrity kinase, MpkA, impacts cellular phenotypes that alter mycelial-material mechanical properties

Mycelial materials are an emerging, natural material made from filamentous fungi that have the potential to replace unsustainable materials used in numerous commercial applications (e.g., packaging, textiles, construction). Efforts to change the mechanical properties of mycelial-materials have typically involved altering growth medium, processing approaches, or fungal species. Although these efforts have shown varying levels of success, all approaches have shown there is a strong correlation between phenotype (of both fungal mycelia and mycelial material’s assembly) and resultant mechanical properties. We hypothesize that genetic means can be used to generate specific fungal phenotypes, leading to mycelial materials with specific mechanical properties. To begin to test this hypothesis, we used a mutant of the model filamentous fungus, Aspergillus nidulans, with a deletion in the gene encoding the last kinase in the cell wall integrity (CWI) signaling pathway, mpkA. We generated one set of mycelial materials from the ΔmpkA deletion mutant (A1404), and another from its isogenic parent (A1405; control). When subjected to tensile testing, and compared to material generated from the control, ΔmpkA material has similar elastic modulus, but significantly increased ultimate tensile strength, and strain at failure. When subjected to a fragmentation assay (i.e., resistance to shear-stress), the ΔmpkA material also had higher relative mechanical strength. To determine possible causes for this behavior, we carried out a comprehensive set of phenotype assessments focused on: three-dimensional structure, hyphal morphology, hyphal growth behaviors, and conidial development. We found, compared to the control, material generated from the ΔmpkA mutant manifests significantly less development, a modified cell wall composition, larger diameter hyphae, more total biomass, higher water capacity and more densely packed material, which all appear to impact the altered mechanical properties.Graphical

Fracture and Fatigue Crack Growth Behaviour of A516 Gr 60 Steel Welded Joints

The facture and fatigue behaviour of welded joints made of A516 Gr 60 was analysed, bearing in mind their susceptibility to cracking, especially in the case of components which had been in service for a long time period. With respect to fracture, the fracture toughness was determined for all three zones of a welded joint, the base metal (BM), heat-affected zone (HAZ) and weld metal (WM), by applying a standard procedure to evaluate KIc via based on JIc values (ASTM E1820). With respect to fatigue, the fatigue crack growth rates were determined according to the Paris law by the standard procedure (ASTM E647) to evaluate the behaviour of different welded joint zones under amplitude loading. The results obtained for A516 Gr. 60 structural steel showed why it is widely used in the case of static loads, since the minimum value of fracture toughness (185 MPa√m) provides relatively large critical crack lengths, whereas its behaviour under amplitude loading indicated a need for further improvement in WM and HAZ, since the crack growth rate reached values as high as 4.58 × 10−4 mm/cycle. In addition, risk-based analysis was applied to assess the structural integrity of a pressure vessel, including comparison with the high-strength low-alloy (HSLA) steel NIOVAL 50, proving once again its superior behaviour under static loading.

Solving the puzzle of copper trafficking in Trypanosoma cruzi: candidate genes that can balance uptake and toxicity.

Trypanosoma cruzi, the causative agent of Chagas disease, depends on acquiring nutrients and cofactors, such as copper (Cu), from different hosts. Cu is essential for aerobic organisms, but it can also be toxic, and so its transport and storage must be regulated. In the present study, we characterized the effects of changes in Cu availability on growth behavior, intracellular ion content and oxygen consumption. Our results show that copper is essential for epimastigote proliferation and for the metacyclogenesis process. On the other hand, intracellular amastigotes suffered copper stress during infection. In addition, we identify gene products potentially involved in copper metabolism. Orthologs of the highly conserved P-type Cu ATPases involved in copper export and loading of secreted enzymes were identified and named T. cruzi Cu P-type ATPase (TcCuATPase). TcCuATPase transcription is upregulated during infective stages and following exposure to copper chelators in the epimastigote stage. Homolog sequences for the high affinity import protein CTR1 were not found. Instead, we propose that the T. cruzi iron transporter (TcIT), a ZIP family transporter, could be involved in copper uptake based on transcriptional response to copper availability. Further canonical copper targets (based on homology to yeast and mammals) such as the T. cruzi ferric reductase (TcFR) and the cupro-oxidase TcFet3 are upregulated during infective stages and under conditions of intracellular copper deficiency. In sum, copper metabolism is essential for the life cycle of T. cruzi. Even though cytosolic copper chaperons were not identified, we propose a previously undescribed model for copper transport and intracellular distribution in T. cruzi, including some conserved factors such as TcCuATPase, as well as others such as TcFR and TcIT, playing novel functions.

Vision-Based Prediction of Flashover Using Transformers and Convolutional Long Short-Term Memory Model

The prediction of fire growth is crucial for effective firefighting and rescue operations. Recent advancements in vision-based techniques using RGB vision and infrared (IR) thermal imaging data, coupled with artificial intelligence and deep learning techniques, have shown promising solutions to be applied in the detection of fire and the prediction of its behavior. This study introduces the use of Convolutional Long Short-term Memory (ConvLSTM) network models for predicting room fire growth by analyzing spatiotemporal IR thermal imaging data acquired from full-scale room fire tests. Our findings revealed that SwinLSTM, an enhanced version of ConvLSTM combined with transformers (a deep learning architecture based on a new mechanism called multi-head attention) for computer vision purposes, can be used for the prediction of room fire flashover occurrence. Notably, transformer-based ConvLSTM deep learning models, such as SwinLSTM, demonstrate superior prediction capability, which suggests a new vision-based smart solution for future fire growth prediction tasks. The main focus of this work is to perform a feasibility study on the use of a pure vision-based deep learning model for analysis of future video data to anticipate behavior of fire growth in room fire incidents.

Influence of surface integrity on short crack growth behavior in HFMI-treated welded joints

This study investigates the influence of surface integrity and the localized fatigue phenomena on the initiation and propagation of short fatigue cracks in high-frequency mechanical impact (HFMI)-treated welded joints. The treated surface region, characterized by a compressive residual stress field, smooth notch geometry, and work hardening layer, improves welded joints’ fatigue strength. However, how these surface conditions influence the fatigue damage process zone during short crack initiation and growth is not yet well known. Therefore, this study systematically investigates the influence of different surface characteristics on fatigue life modeling of HFMI-treated welded joints made of high-strength steel. This is achieved using a non-local continuum damage mechanics-based approach of crack growth and elastic–plastic finite element simulation, explicitly modeling treated surface conditions. The simulated fatigue life is first verified with experiments and then applied to various surface conditions. The simulation results show that most of the fatigue life is spent until a crack size of 0.2 mm. The compressive residual stress field greatly extends both short crack initiation and propagation life, with its degree of contribution highly dependent on loading history and residual stress change. The role of the work hardening layer is mainly concentrated on improving fatigue life during short crack initiation and the very beginning of short crack growth.

New findings on reduced solidification brittle temperature range in epitaxially grown CMSX-4 superalloy welds via varestraint testing

This study examines the solidification brittle temperature range (BTR) of CMSX-4 superalloy welds. Based on the BTR evaluation results, we quantitatively suggest the minimum BTR value for the solidification crack-free welding of the alloy. For the BTR evaluation, a transverse-Varestraint test correlated with real-time visualization of the molten pool temperature was applied. The BTR was evaluated to be 28 K for the 10A-linear condition, 109 K for the 20A-linear, and 336 K for the 30A-linear. With the application of oscillation, the BTR expanded to 434 K (0.6Hz-oscillated). The wide variation in BTR according to the welding conditions was investigated through the characteristics of the crystal growth behavior at the solidification cracking regions. For the 10A-linear condition with the narrowest BTR of 28 K, the entire weld metal, including the solidification cracking region, exhibited perfectly epitaxial growth identical to the base metal's crystal orientation. As the BTR expanded, controversially, the solidification cracking region showed polycrystalline behavior. Consequently, the BTR in the CMSX-4 superalloy welds can be reduced, and weldability can be improved by enhancing the degree of single crystallization during welding fabrication. This improvement is attributed to the reduction of dendrite coalescence undercooling.

FRESH 3D Bioprinting of Collagen Types I, II, and III.

Collagens play a vital role in the mechanical integrity of tissues as well as in physical and chemical signaling throughout the body. As such, collagens are widely used biomaterials in tissue engineering; however, most 3D fabrication methods use only collagen type I and are restricted to simple cast or molded geometries that are not representative of native tissue. Freeform reversible embedding of suspended hydrogel (FRESH) 3D bioprinting has emerged as a method to fabricate complex 3D scaffolds from collagen I but has yet to be leveraged for other collagen isoforms. Here, we developed collagen type II, collagen type III, and combination bioinks for FRESH 3D bioprinting of millimeter-sized scaffolds with micrometer scale features with fidelity comparable to scaffolds fabricated with the established collagen I bioink. At the microscale, single filament extrusions were similar across all collagen bioinks with a nominal diameter of ∼100 μm using a 34-gauge needle. Scaffolds as large as 10 × 10 × 2 mm were also fabricated and showed similar overall resolution and fidelity across collagen bioinks. Finally, cell adhesion and growth on the different collagen bioinks as either cast or FRESH 3D bioprinted scaffolds were compared and found to support similar growth behaviors. In total, our results expand the range of collagen isoform bioinks that can be 3D bioprinted and demonstrate that collagen types I, II, III, and combinations thereof can all be FRESH printed with high fidelity and comparable biological response. This serves to expand the toolkit for the fabrication of tailored collagen scaffolds that can better recapitulate the extracellular matrix properties of specific tissue types.

Constructing valid Li+ fast-transfer channels on novel P(TPC@Lys-Li) separator to enable security, high energy density, and controllable Li dendrites for lithium-metal batteries

Lithium metal batteries (LMBs) attract widespread attention under current high energy density developments. However, wild Li dendrite propagations owing to chaotic Li depositions raise challenges for LMB blossoming. Separators with specific demands thus should be involved when smoothly transferring into LMBs. In this research, a fascinating P(TPC@Lys-Li) separator is prepared by the turbulent interfacial polymerization and electrospinning to ingeniously clarify dependencies of Li+ transfer dynamics on double electric layer thickness (DELT) regulations within porous skeletons. P(TPC@Lys-Li) enables negatively charged porous skeleton surface and compresses DELT, which constructs high-efficiency Li+ fast-transfer channels on porous skeletons and accelerates Li+ transfer speed by 18.3 times. Especially, P(TPC@Lys-Li) supplies extra Li+ for stable formations of solid electrolyte interphase (SEI) layer, homogenizing nucleation and growth behaviors during Li depositions. Remarkable C-rate capacity and cycle stability thus arise for assembled LMBs, holding 87.2 % capacity retention after 700 cycles at 0.5C even under high cathode loading and lean electrolyte conditions. P(TPC@Lys-Li) also maintains constant physical scale and unabated mechanical strength even at elevated temperatures approaching 200 °C, which provides excellent battery security as LMBs encounter uncontrollable thermal runaway. Above attractive features enable P(TPC@Lys-Li) separator to be potentially applied in LMBs demanding sufficient security, high-capacity density, and fast charge technology.

Transcription Impairment of TMEM208 by ZBTB14 Suppresses Breast cancer Radiotherapy Resistance

Zinc finger and BTB domain-containing protein (ZBTB) proteins have been implicated in different cellular processes, including DNA damage responses and cell cycle progression. However, the mechanism by which ZBTB14 modulates radiotherapy (RT) radioresistance (RT-R) remains to be elucidated. We aimed to elucidate the regulation mechanism of ZBTB14 in breast cancer (BC) RT-R. Using integrated bioinformatics prediction, ZBTB14 was identified as a hub transcription factor related to RT-R in BC. ZBTB14 was significantly under-expressed in non-responders and RT-R/BC cells, whereas its target transmembrane protein 208 (TMEM208) was significantly overexpressed in non-responders and RT-R/BC cells. Chromatin immunoprecipitation-qPCR and luciferase reporter assays revealed that ZBTB14 downregulated TMEM208 expression through transcriptional repression. Overexpression of ZBTB14 significantly inhibited the malignant biological behavior of BC cells and tumor growth in vivo, and further upregulation of TMEM208 reversed the biological activity and radiotherapy resistance of RT-R/BC cells inhibited by overexpression of ZBTB14.

Structure, performance and deposition control of the graphitic carbon protective layer in blast furnace hearth

Hundreds of operational blast furnaces annually are forced to be maintained using traditional methods due to hearth safety, significantly increasing carbonaceous fuel consumption and maintenance costs. Our team has pioneered a novel hearth maintenance approach, whose core lies in promoting the formation of a graphitic carbon protective layer. The key to forming this protective layer and optimizing its structure and performance lies in regulating the precipitation and growth behavior of graphite in blast furnace molten iron. This work first clarified the phase composition, morphology, crystal structure, growth direction, and high-temperature performance of the graphitic carbon protective layer by multiple characterization methods. The contents of C, Si, S, and Ti in the protective layer were much higher than those in molten iron, and the C content was up to 81.24 wt.%. Graphite exhibited macroscopically large-size flake morphology and microscopically lamellar stacking structure, and its preferred growth direction was [21-30]. The thermal conductivity of the protective layer decreased with increasing temperature. The CSLM in-situ experiments were conducted to reveal the effect of the molten iron elements on the precipitation and growth behavior of graphite. The elements that promote the graphite precipitation were Si, Ti, and C in order, while S inhibited it. The S, C, and Si promoted the lateral growth of graphite along the a-axis, and S was the strongest promoter. The effect of Ti on graphite growth was negligible. The control approach for promoting the deposition of flake graphite was proposed in terms of both temperature and molten iron elements.

Effect of printing parameters on the microstructure, mechanical properties and fatigue crack growth behavior of Al-Zn-Mg-Cu-Si-Zr-Er alloy prepared by laser powder bed fusion

Effect of printing parameters on the microstructure, mechanical properties and fatigue crack growth behavior of Al-Zn-Mg-Cu-Si-Zr-Er alloy prepared by laser powder bed fusion

The role of cyclic oxidation on low cycle fatigue crack initiation and growth behaviour of a Ni-based superalloy

The role of cyclic oxidation on low cycle fatigue crack initiation and growth behaviour of a Ni-based superalloy

In-situ experimental investigation of the small fatigue crack behavior in CP-Ti: The influence of loading parameters and directions

This study quantitatively investigates the influence of loading parameters and directions on the behavior of small fatigue cracks (SFC) in commercially pure titanium (CP-Ti). It is observed that reductions in peak stress and increases in stress ratio correlate with a decrease in SFC growth rate and an intensification of growth rate fluctuations. Notably, crack growth along the transverse direction (TD) generally exhibits lower rates compared to that along the rolling direction (RD), with more pronounced fluctuations. Through metallographic analysis of crack paths, roughness-induced crack closure (RICC) is identified as a significant factor contributing to the observed variations in SFC growth behavior under different loading conditions. Furthermore, electron backscatter diffraction (EBSD) characterization reveals that crack propagation along the RD is primarily governed by prismatic slip, while TD samples exhibit more engagement of non-prismatic slip systems with higher activation stress. This results in a more tortuous crack path and pronounced crack arrest phenomena. Finally, a modified multi-scale rate prediction model based on the reference stress ratio method is proposed. Comparative analysis demonstrates that the modified model outperforms existing models by offering enhanced predictive capability across diverse loading conditions, thereby reinforcing its robustness in predicting SFC behavior of CP-Ti.

A deformation-diffusion interactive model to study crack-tip behaviour and predict crack growth rate under fatigue and hydrogen-embrittlement conditions

Hydrogen is accepted as a cleaner and more sustainable energy source, since it carries abundant energy and does not produce any effluent gas from burning when compared to fossil fuels. However, long-term degradation in mechanical properties, attributed to hydrogen embrittlement, is reported for metallic materials exposed to gaseous hydrogen, leading to accelerated crack growth behaviour under fatigue. In this paper, a visco-plastic deformation-diffusion interactive model is developed to study fatigue crack growth behaviour in a nickel-based superalloy under hydrogen-embrittlement condition. In the model, cyclic deformation is described by visco-plasticity constitutive model, while hydrogen diffusion is simulated by a modified form of Fick’s first law of diffusion which can address hydrogen diffusion driven by the hydrostatic stress gradient. In particular, trapped hydrogen, expressed as dependent on both diffusible hydrogen concentration and inelastic strain, is considered in the modelling of hydrogen diffusion. The model also describes the effects of hydrogen concentration on mechanical deformation by considering its influence on the evolution of isotropic hardening as well as on the strain state. Interaction between cyclic deformation and hydrogen diffusion is therefore studied for a crack tip in a compact tension specimen subjected to fatigue and hydrogen attack, showing a strong dependency on both loading frequency and stress intensity factor range. Subsequently, a two-parameter criterion is proposed for fatigue crack growth prediction, which accounts for the contributions of both cyclic deformation and hydrogen diffusion. The predictions show a good agreement with experimental data in terms of crack growth rate under fatigue and hydrogen-embrittlement conditions.

Assessment of the fatigue crack growth behavior of HG785D steel welded joints

Fatigue performance of high-strength steel welded joints is widely concerned in engineering fields. In this research, the fatigue crack growth (FCG) behavior of HG785D steel with and without a "soft + hard + soft" composite welded metal is investigated by conducting FCG tests, hardness tests and fracture observation. Further, FCG curves (da/dN-ΔK) quantified by Seven-point incremental polynomial method (SP) and Smith method (SM) from tested crack length and number of cycles are compared. Results show the fatigue performance of composite welded metal is improved due to the hard layer ensures strength and soft layers provide toughness. Additionally, the fatigue life assessment is safer using da/dN-ΔK curves by SP, whereas more accurate using that by SM. The da/dN-ΔK curves by SP can capture the local fluctuations in FCG rate, while that by SM provides a smooth and global description for FCG behavior with steadily increased da/dN. Considering heterogeneous properties of composite welded metal, a piecewise function combining SP method is recommend to describe the unconventional da/dN-ΔK curves. Moreover, the correlation between Paris parameters for steels is analyzed, offering a reference for fatigue reliability assessments.

Fluorescent nanoparticles from roast duck induce cell damage and physiological dysfunction in Caenorhabditis elegans.

The safety of fluorescent nanoparticles (FNPs) that enter the human body through food consumption is uncertain. In this study, the biocompatibility of FNPs derived from roast duck was investigated using pheochromocytoma (PC12) cells and Caenorhabditis elegans. Fluorescent nanoparticles, at concentrations of 1 and 4 mg mL-1, caused an increase in early apoptosis, altered the cell cycle, elevated reactive oxygen species levels, and decreased mitochondrial membrane potential in PC12 cells. Both acute and prolonged exposure to the FNPs enabled them to permeate C. elegans via its food source, accumulating predominantly in the intestine. At concentrations ranging between 0 and 15 mg mL-1, FNPs did not induce mortality in C. elegans but they did affect its growth, reproductive ability, and motor behavior. This study advances the understanding of FNP safety significantly, facilitates risk assessment for foods containing FNPs, and provides valuable guidance to ensure food safety. © 2024 Society of Chemical Industry.

Fatigue Crack Initiation and Growth Behaviors of Additively Manufactured Ti-6AI-4V Alloy After Hot Isostatic Pressing Post-Process

In this study, the fatigue crack initiation and growth behaviors of an additively manufactured (AM) Ti-6AI-4V alloy were investigated, and its prospect for fatigue applications was evaluated. The AM specimens were first fabricated by selective laser melting (SLM) and then underwent a cycle of annealing at 800 °C for 2 h and hot isostatic pressing (HIP) treatment at 920 °C/150 MPa/3 h followed by surface machining. Prefabricated spherical defects with different diameters (1.0 mm and 2.0 mm) were introduced to examine the efficacy of HIP treatment for eliminating the built defects. Both fracture morphology and microstructure were characterized to reveal the failure mechanism of these tested specimens. The results suggest that both the fatigue lives and fatigue crack growth resistances of most SLM+HIP-processed specimens are much higher than those of traditional wrought material, thus highlighting that the AM Ti-6AI-4V alloy can be a better candidate for future fatigue applications. However, due to the large variability in fatigue performance, the current SLM+HIP-processed Ti-6Al-4V alloy still cannot meet the demand for high safety and reliability.

Ex-situ observation of ferrite grain growth behavior in a welded 9Cr-1Mo-V-Nb steel during aging at 740 °C

It has recently been reported that ferrite grains coarsened to several hundred micrometers were occasionally observed in long-term serviced 9Cr-1Mo-V-Nb steel welds. To clarify the factors that cause ferrite grain growth in martensite during high-temperature exposure, alternating aging heat treatment and observation of the same field of view was performed using a welded 9Cr-1Mo-V-Nb steel. Such ex-situ observations revealed that the rapid grain growth of ferrite by consuming martensite occurred in the weld metal during aging at 740 °C. In the test material used in this study, some δ-ferrite grains were observed in the weld metal near the fusion line. In the region where δ-ferrite grains were observed, the concentrations of austenite-forming elements such as Mn and Ni were locally decreased in the matrix due to dilution by the base metal, promoting δ-ferrite retention after welding. Ex-situ observation indicated that no significant grain growth of δ-ferrite occurred during aging. Therefore, it was suggested that a new ferrite grain formation followed by rapid grain growth consuming martensite occurred during aging. The elastic strain energy density of the dislocations PMdis and the interfacial energy density PMsurf in martensite can affect the driving force for ferrite grain growth by consuming martensite. Based on the evaluation results for PMdis and PMsurf after 500 h of aging, PMsurf was considered to be the main driving force for ferrite grain growth. Although the ferrite-formation process could not be directly observed, it is possible that ferrite was formed by the recrystallization of martensite through the bulging mechanism.

Effects of the grain size and orientation of Cu on the formation and growth behavior of intermetallic compounds in Sn-Ag-Cu solder joints

The rapid development of semiconductor packaging technology has accelerated the applications of flip-chip bonding technology using fine-pitch micro bumps and Cu pillar bumps. These micro-bump systems are composed of metallic Cu and Sn. The properties of the Cu- and Sn-based bonding materials applied in these technologies have a significant effect on the mechanical properties and long-term reliability of micro-joints. This study focuses on the effects of the grain size and orientation of the Cu substrate on the formation and growth of intermetallic compounds (IMCs) at the Sn/Cu interface. The Cu substrate was annealed from 200 to 1000 °C to alter its grain size, which was measured via electron backscatter diffraction analysis. Sn-3.0Ag-0.5Cu (SAC) solder paste was printed onto the Cu substrate, and the Sn/Cu interfacial microstructure was observed by scanning electron microscopy and energy-dispersive X-ray spectroscopy after the reflow soldering process. A thin IMC formed on substrates with small grain sizes, whereas larger grain sizes resulted in the formation of thick and elongated IMCs. In addition, the IMC growth exhibited a specific directional preference in the (21̅1̅0) direction on substrates annealed at 1000 ℃. The effects of the Cu grain size and orientation on the interfacial reactions and growth of IMCs were compared and analyzed by observing IMCs formed at the SAC/Cu interface. Microstructural analysis revealed that controlling the Cu grain size and orientation significantly impacts the reliability of the solder joints. This study shows that the effect of grain size and orientation can be utilized to micro-solder joints, which can significantly enhance their mechanical strength and reliability.