High Stress Regime Research Articles

KUFRI DAKSH: A NEW WATER-USE EFFICIENT TABLE POTATO VARIETY WITH CROSS TOLERANCE TO HIGH TEMPERATURE STRESS

Kufri (K) Daksh is a main season, medium maturing, high yielding, water-use-efficient table potato variety that can be grown in regions with limited water availability. It is a clonal selection from the cross between CP1748, having high water use efficiency and LT-1 tolerating high temperature stress. Its plants are tall and vigorous with field resistance to late blight. Its tubers are white-cream (light yellow), ovoid with shallow to medium eyes and cream flesh with good keeping quality. It is fertilizer responsive and can yield 30-35 t/ha under low water (≤ 20%) availability in middle Gangetic plains. K Daksh has better trade-off for high CO2 gain and low water loss through optimization in plant canopy leaf area and plant height components. K Daksh can be an excellent choice to tolerate high temperature and water stress regimes in changing climatic scenarios.

A review of CO2-injection projects in the Brazilian Pre-Salt — Storage capacity and geomechanical constraints

This review describes the main geological and geomechanical aspects of CO2-injection projects in the Brazilian Pre-Salt reservoirs, focusing on the storage potential and geomechanical aspects of CO2 injection. The Pre-Salt reservoirs in the Santos Basin offer favorable conditions for CCS due to their geological characteristics and existing infrastructure. The thick evaporite caprock, primarily composed of halite, acts as an efficient seal against CO2 migration. The CO2-injection in the Pre-Salt has been active since 2010, with significant amounts of CO2 already stored in the reservoirs. The volumetric assessment estimates the static storage capacity of the Pre-Salt reservoirs to be over 3.3 Gt of CO2, considering only the four fields currently undergoing injection. Geomechanical constraints, including the maximum injection pressure and caprock integrity, are crucial considerations for safe CCS operations. The high stress regime and the hydrostatic state of the caprock minimize the risk of fracturing during injection. Furthermore, dynamic storage capacity calculations indicate the feasibility of injecting CO2 into Pre-Salt reservoirs. This review provides insights into the current state and future prospects of CO2-injection projects in the Brazilian Pre-Salt, contributing to the development of sustainable carbon mitigation strategies in the region.

Stochastic nature of incipient plasticity in a body-centered cubic medium-entropy alloy

The stochastic nature of the small-scale incipient plasticity (i.e., “pop-in” behavior manifested as a sudden displacement excursion in the load-displacement curves) in a single grain of the body-centered cubic NbTiZr medium-entropy alloy is explored through a series of nanoindentation tests with three spherical tips having different radii (1.8, 3.4, and 8.2 μm). The maximum shear stress underneath the indenter shows distinct distributions depending on the tip radius, wherein both a narrow high-stress regime and a broad low-stress regime are observed. By recourse to deconvolution of the data and detailed statistical analysis, the two regimes were found to be dominated by homogeneous and heterogeneous yielding mechanisms, respectively. Upon hydrogen charging, the tip radius dependence is sustained, but the fraction of heterogeneous yielding is enhanced, which is due to the hydrogen's effect in assisting defect formation. The suggested scenarios for how the mechanisms are affected by the stressed volume (or tip radius) and hydrogen-induced structural changes were confirmed by direct observations of the deformation behavior underneath the indenter with cross-sectional transmission electron microscopy made on post-pop-in samples.

Nonlinear network connectedness: Assessing financial risk transmission in MENA and influence of external financial conditions

This study investigates the influence of global financial market conditions on financial risk connectedness and transmission among the Middle East and North Africa (MENA) economies. Utilizing weekly realized stock market volatilities as a measure of risk and employing a smooth transition threshold vector autoregressive (STVAR) model to analyze risk transmission under varying levels of financial stress, the authors also examine the impact of external macroeconomic conditions on the risk connectedness of MENA economies. The results indicate that the overall connectedness, based on a standard VAR model, is moderate at 48.34%. However, in the low financial stress regime, overall connectedness increases to 52.79%, and in the high financial stress regime, it rises to 72.94%, indicating stronger risk interdependency among MENA countries during times of high stress. In the high financial stress regime, Kuwait, Oman, Qatar, Saudi Arabia, Turkey, and the United Arab Emirates are identified as net risk transmitters among MENA countries. The study also reveals that risk transmission across MENA is more pronounced in the regime-dependent model compared to the overall mean-based VAR model.

Nonlinear transmission of international financial stress

This paper investigates nonlinear international financial stress spillovers on a small open economy. The literature provides evidence that financial stress may amplify the effects of adverse shocks. Using monthly data from the US and Canada over the period 1983–2019, we estimate a two-country threshold vector autoregressive model, where economies can be in either a financially tranquil or stressful regime. In times of high financial stress, we find macro-financial fragility between the real economy and financial stress in the US that generates a risk amplification mechanism deepening economic downturns. Additionally, when both countries are in a high-stress regime, US financial shocks are transmitted more strongly to the Canadian financial system and they are more detrimental for a large number of Canadian macro-financial variables. Finally, simulations suggest that our regime-switching model better captures the economic downturn in Canada during the 2007–2008 financial crisis, compared with a linear model.

Mitigation of tunnel support design risks for hydropower projects within high tectonic stress regimes – an empirical analysis

Abstract The study for the design of tunnels in similar geological settings, providing insights into potential challenges that may arise during excavation and offering strategies for mitigating risks in District Kalam on the Ushu River, Khyber Pakhtunkhwa, Pakistan. The methodology involved geological mapping, rock sampling, discontinuity surveys, and laboratory testing for empirical analysis of tunnel parameters at the Weir House, Powerhouse, and tunnel alignment locations. Empirical analysis of tunnel parameters using three rock classification systems, rock mass rating (RMR), rock quality tunneling index, and rock mass index (RMi). Based on the classification, the rock quality was found to be fair, indicating favorable rock properties. The Q-system rated the rock as poor to fair, suggesting low discontinuity intensity, medium rock strength, or medium deformation modulus. According to the RMi, rock was rated as medium to strong, indicating low discontinuity intensity, high rock strength, or low deformability. The support design for the tunnel is based on empirical analysis, it recommends support design for the tunnel reinforcement elements such as rock bolts, wire mesh, and shotcrete lining. Overall, the tunnel is stable and does not have complex structure and weak zones.

Global supply chain inflationary pressures and monetary policy in Mexico

In this paper, we examine the impact of stress in the global supply chains on inflation and monetary policy in Mexico, a representative emerging market economy. Using non-linear local projections, we estimate the degree of monetary policy tightening required in a high-stress supply chain environment and compare it to that in a low-stress environment. We instrument the monetary policy shocks with shocks to the federal funds rate. Results suggest that in a high-stress regime, the effect of an increase in the monetary policy interest rate on inflation over a one-year period is reduced considerably. We argue that this reduction is due to the slow response of inflation expectations to a monetary policy tightening in a high-stress regime. Furthermore, raising the interest rate has an effect on producer price inflation, a channel that is absent in a low-stress regime. This finding highlights the role of monetary policy in stabilizing inflation when facing supply shocks that are not necessarily permanent.

Effects of bed sediment conditions on debris flow propagation from the two-phase flow modelling perspective

Debris flows are classical two-phase flows that are greatly affected by bed sediment conditions. However, the underlying mechanism remains uncertain from either a theoretical or numerical perspective. Here an existing depth-averaged two-phase continuum flow model is further improved by incorporating the effects of pore-fluid pressure and bed sediment conditions. By numerical simulation of the USGS experiments, we have numerically reproduced the mechanism that “the coarser the bed sediments and the larger the basal pore pressure, consequently the larger the erosion rates”. Moreover, an additional mechanism for this phenomenon has been revealed. Specifically, debris flows on steep slopes are likely to fall into a high shear stress regime, under which conditions the sediment transport capacity always takes a maximum value and is independent of the sediment size. Therefore, the sediment settling velocity that is proportional to the sediment size affects the erosion rate directly. It is also observed that the added potential energy due to a net erosion has positive effects on the kinetic energy of the debris flow. Notably, coarse and fine particles exhibit distinct roles in energetics and the former is characterized by more intensive interactions with the water phase, which should be appropriately considered in the modeling. Finally, particle size coarsening is observed in the head region, which is attributed to the hiding/exposure mechanisms of nonuniform sediments. These findings can enhance the understanding of the mechanism between the bed conditions and debris flow.

Capacitive self tension sensing properties of steel beam: electrode configuration and stress regime

A structural material is called self-sensing when it is able to reveal its own state without the need for any external sensors. Self-sensing for steel is valuable for the control and safety of steel structures such as buildings and bridges. The changes in the capacitance of steel in response to cyclic tensile stresses applied in low, medium and high stress regimes are measured by using a Inductnce-Capacitance-Resistance (LCR) meter. Coplanar and parallel plate electrode configuration is used for capacitance measurements. Aluminum foil is used as electrode. A steel beam of 100 mm in length, 30 mm in width and 2.5 mm in thickness is tensioned by holding it at both ends to produce direct tensile stresses in the material. The maximum stresses applied for low, medium and high stress regimes are 6.7 MPa, 33.3 MPa and 66.7 MPa. The capacitance value of the sample with coplanar and parallel plate electrode configurations measured without applying load are 203.42 pF and 196.00 pf, respectively. The fractional changes in capacitance are 0.059%, 0.192% and 0.275% when 6.7 MPa, 33.3 MPa and 66.7 MPa direct tensile stress is created in the steel beam. These values are 0.12%, 0.20% and 0.29% for parallel plate electrode configuration. Test results demonstrates that there is a relation between stress and fractional change in capacitance. In other words, measuring fractional change in capacitance gives information about the stress variations in the material. From the experimental results, parallel plate electrode configuration is found to be more effective in tensile stress self-sensing. In addition, the relationship between stress and fractional change in capacitance is more linear for both electrode configurations in the low stress regime. This paper aims to reveal the tensile stresses occurring in steel by means of capacitance-based sensing. Sensing capability in larger scale structures and factors effecting sensing sensitivity are to be addressed in future work.

Enhancing the creep resistance of a cast AZ91 alloy via minor Sc addition

The influence of 0.2 wt% Sc addition on the microstructure and creep characteristics of a cast AZ91 magnesium alloy was studied by impression creep tests under the constant punch stresses ranging from 175 to 700 MPa in the temperature range 425–525 K. The findings indicated that creep rates decreased at all stress levels and temperatures after Sc addition. This was ascribed to the formation of the thermally stable Al3Sc and Mg5Al4Sc particles, reduction in the quantity of the unstable β-Mg17Al12 phase, and solid solution strengthening of Al in the Mg matrix. The creep stress exponent and activation energy values obtained from the studied alloys ranged from 5–6 and 95–117 kJ/mol, respectively. The detected drop in creep activation energy with increasing stress implies that two concurrent mechanisms of dislocation climb controlled by lattice and pipe-diffusion are competing with each other. The former one was the governing mechanism at low stress levels, while the latter one was the prevailing mechanism in the high stress regimes.

Vulnerability in the Java northen region in association with earthquake sources of tectonic origin

While threats from the subduction zone off the Java south coast remain persistent, potential sources of a tectonic earthquake centered in the Java northern areas come into play. Despite their enigmatic presence and a clear shift of the sources from the mainland to the north from hypocentre relocation studies, this poses a danger to the community in the Java northern coastlines, increasing vulnerability to earthquake and tsunami hazards. The main aim of this study is thus to evaluate seismic hazards and corresponding analysis, hence assessing vulnerability with respect to the presence of active faults in the northern regions. The methods used here included a-value and b-value calculations inferred from seismogenic zonation made available for the study area and source mechanism determination derived from seismic inversion for two recent events recorded at the Java Sea. The results revealed that the a-value reached 8.55 in Zone 1, reflecting a high seismicity rate over the northern areas of West Java and Banten provinces, and the b-value was about 0.8 in Central Java and East Java, implying a relatively high-stress tectonic regime. The moment tensor solutions yielded sizes M w 6.7 at a depth of 539 km and M w 7.0 at a depth of 594 km with a major double-couple component for the normal faulting types of mechanism, consistent with reference. The results suggest the significance of awareness of seismic threats possible to occur in the Java northern regions; hence more investigations into detailed seismicity in the regions of interest for future research direction.

Creep property and microstructural evolution of laser powder bed fused binary Al–10Ce alloy

Aluminum–Cerium (Al–Ce) based alloys have shown promise as cost-efficient high temperature creep-resistant aluminum alloy. These alloys are also highly printable with laser powder bed fusion (LPBF) additive manufacturing. This study investigates the creep property of a near eutectic binary Al–10Ce (wt. %) alloy manufactured by LPBF and its microstructural evolution during creep. The as-built alloy exhibited columnar grain structure with a weak cube texture and its microstructure consisted of fine eutectic Al + Al11Ce3. Compressive creep tests with incremental stresses were performed perpendicular to the build direction at temperatures ranging from 275 to 400 °C. The stress exponent was approximately 1 in the low stress regime and 5–7 in the high stress regime, corresponding to diffusion and dislocation creep, respectively. The average activation energy was approximately 229 kJ/mol·K in the temperature between 275 and 375 °C. After creep deformation, the melt pool boundary faded and the eutectic Al11Ce3 intermetallics slightly coarsened. The grain structure remained relatively stable and the grain boundary became more pronounced. By comparing the minimum creep strain rate to other alloys, it was found that LPBF Al–10Ce is more creep resistant than similar cast binary Al–Ce counterpart, some ternary Al–Ce alloys and LPBF AlSi10Mg alloy. This benchmark results on the creep property of LPBF binary eutectic Al–Ce alloy provide insights to future development of creep-resistant Al–Ce alloys.

Creep damage mechanism of 20Cr32Ni1Nb steel at high temperatures

In the petrochemical industry, the centrifugally cast austenitic 20Cr32Ni1Nb stainless steel used in steam reformer furnace's hot outlet manifold experiences creep failure and microstructural degradation, impacting its structural integrity. Understanding the causes of these issues is crucial for addressing the associated challenges. This study examines the creep deformation behaviour, damage mechanisms, and microstructural evolution of 20Cr32Ni1Nb steel under stresses of 22–50 MPa at temperatures of 1163 K (890 °C) and 1223 K (950 °C). Analysis of creep and creep strain rate curves revealed the presence of both primary and tertiary creep stages, with the power law relationship governing the stress-dependent minimum creep rate and rupture life. The variance of creep damage tolerance factor was also analysed, with results showing that in high-stress regimes, loss of section and necking along with cavity growth may initiate tertiary creep, while in low-stress regimes, microstructural degradation, specifically G-phase formation, may initiate tertiary creep. As the duration of creep exposure increases, microstructures were observed to degrade, with the growth and coarseness of NbC and M23C6 carbides. The structure of the space group for the Ni–Nb–Si enriched G-phase in 20Cr32Ni1Nb steel was found to be Fm3‾m, with a lattice parameter of about 1.14 nm.

Asymmetric effects of monetary policy and financial accelerator: Evidence from India

This paper analyzes the asymmetric effects of monetary policy shocks during low and high financial stress regimes in India. We explore the asymmetric effects through various monetary policy transmission channels, namely, interest rate, credit, asset prices, exchange rate, and expectations channels, using threshold vector autoregression (TVAR) models. Financial Stress Index (FSI) is used in the TVAR estimations as the threshold variable that endogenizes the regime-switching. We use a compressive FSI based on the dynamic conditional correlation-generalized autoregressive conditional heteroscedasticity (DCC-GARCH) method. The empirical findings indicate that a contractionary monetary policy shock through various channels has a stronger and more persistent effect on macroeconomic goal variables, output, and inflation during high financial stress than in a low financial stress regime. An expansionary monetary policy shock also shows a more significant effect on output during a high financial stress regime. Also, we found a stronger financial accelerator effect during high financial stress. This finding supports the literature that argues for the emergence of a stronger financial accelerator effect during financial stress. Finally, using nonlinear historical decompositions, we find that interest rate shocks contribute significantly to macroeconomic fluctuations in India.

Financial Stress and Effect on Real Economy: Turkish Experience

The core of this paper is an econometric estimation of the relation between financial stress and a number of macroeconomic variables (consumption, real GDP, investment, unemployment). This estimation is done on Turkish quarterly data for the period 2002-2021 using threshold vector autoregression (i.e., TVAR). The paper observes the non-linear trade-off between financial stress and macroeconomic indicators. The effect of financial stress appears to be adverse when the stress level is already at a higher level. During high stress episodes, any further increase in financial stress drags economic growth down and the effect appears to be prolonged in nature. Consumption and investment growth also moderate due to a higher stress level. Furthermore, the forecast error decomposition indicates sustained contribution of financial stress impeding growth prospects over the forecast horizon. The findings corroborate with the financial friction mechanism. As borrowing constraint tightens during a high stress regime, the effect of financial stress moderates economic activities. Lastly, the paper extends a local projection approach for estimating a threshold VAR model as a robustness check.

Coherency loss marking the onset of degradation in high temperature creep of superalloys: Phase-field simulation coupled to strain gradient crystal plasticity

A dislocation density based crystal plasticity — phase-field model is applied to investigate directional coarsening during creep in CMSX-4 Ni-based superalloys in the high temperature and low stress regime. Coherency between the ordered γ′ precipitates and the disordered γ channels prevents the generation of geometrically necessary dislocations, since the precipitate can be considered undeformable in the low stress regime. After coherency loss between the γ matrix phase and the γ′ precipitates the constraint against generation of geometrically necessary dislocations is relaxed, causing rotation of the crystal lattice under uniaxial load, known as “Schmid rotation”. As a consequence, the creep rate in the matrix increases, whereby degradation can be measured by the number density of geometrically necessary dislocations. The state of coherency loss is associated with the minimum creep rate in a creep experiment under constant load. The presented simulations start from a coherent γ′ precipitates distribution with random size and position generated during a precipitation heat treatment process. Simulations of N-type and P-type rafting under tensile and compressive load respectively are presented. The effect of coherency loss, coalescence of precipitates and lattice rotation due to generation of geometrically necessary dislocations is discussed in correlation with experimental findings.

Shear thickening in dense bidisperse suspensions

Discrete-particle simulations of bidisperse shear thickening suspensions are reported. The work considers two packing parameters, the large-to-small particle radius ratio ranging from δ=1.4 (nearly monodisperse) to δ=4, and the large particle fraction of the total solid loading with values ζ=0.15, 0.5, and 0.85. Particle-scale simulations are performed over a broad range of shear stresses using a simulation model for spherical particles accounting for short-range lubrication forces, frictional interaction, and repulsion between particles. The variation of rheological properties and the maximum packing fraction ϕJ with shear stress σ are reported. At a fixed volume fraction ϕ, bidispersity decreases the suspension relative viscosity ηr=ηs/η0, where ηs is the suspension viscosity and η0 is the suspending fluid viscosity, over the entire range of shear stresses studied. However, under low shear stress conditions, the suspension exhibits an unusual rheological behavior: the minimum viscosity does not occur as expected at ζ≈0.5, but instead decreases with further increase of ζ to 0.85. The second normal stress difference N2 acts similarly. This behavior is caused by particles ordering into a layered structure, as is also reflected by the zero slope with respect to time of the mean-square displacement in the velocity gradient direction. The relative viscosity ηr of bidisperse rate-dependent suspensions can be predicted by a power law linking it to ϕJ, ηr=(1−ϕ/ϕJ)−2 in both low and high shear stress regimes. The agreement between the power law and experimental data from literature demonstrates that the model captures well the effect of particle size distribution, showing that viscosity roughly collapses onto a single master curve when plotted against the reduced volume fraction ϕ/ϕJ.

Slope design in brecciated carbonatite complexes under high-stress regimes

Slope design in brecciated carbonatite complexes under high-stress regimes

Microstructure-sensitive modeling of high temperature creep in grade-91 alloy

Predicting the effects of microstructure on high-temperature creep responses of steel components is critical to minimize the risks of failure and maximize economic viability in the energy sector. In this work, a recently developed advanced mechanistic constitutive model is employed to study the effect of microstructure on the creep responses and to rationalize experimentally reported variability in the performances of grade-91 alloy. Hundreds of experimental creep tests from the literature are used to assess the predictability of the model. The model proposed is shown to accurately predict the steady-state creep rates and also the less commonly considered, yet important, primary-to-secondary transients for a wide range of creep conditions. Further, the model is capable of extrapolating the creep response of grade 91 alloy even outside of the calibration regime. Using this model, the roles of initial microstructure described in terms of grain size, dislocation density, and precipitate content, on the creep responses are investigated. The effect of initial microstructure on the steady-state creep rates and creep-strain is found to vary with stress and temperature. Grain size plays a significant role in the low-stress creep, where the diffusional creep is dominant. On the other hand, the effects of dislocation densities and precipitate content are significant in the dislocation-plasticity-dominated high-stress and temperature regimes. Furthermore, by comparing model predictions against a large experimental creep database, it is found that variability in the creep responses can be rationalized on the basis of differences in the initial microstructure. Overall, this work provides a robust pathway for microstructure-aware engineering design, verification, and validation of metallic components for energy applications.

Effect of Mg microalloying on elevated-temperature creep resistance of Al–Cu 224 cast alloys

The influence of microalloying with Mg (0–0.36 wt%) on the elevated-temperature strength and creep resistance of Al–Cu 224 cast alloys was investigated. The Mg-containing alloys yielded finer and denser θ′ precipitates after high-temperature stabilization (300 °C/100 h) than the Mg-free alloy, which improved the yield strength at both room temperature and 300 °C. Compressive creep tests were conducted at 300 °C over a wide range of the applied stresses (45–100 MPa). The results showed that the creep resistance increased with increasing Mg content at any fixed applied stress, and the alloy with 0.36 wt% Mg exhibited the best creep resistance among the four alloys studied. During creep deformation, the θ′ precipitates continued to coarsen. However, Mg microalloying greatly stabilized the θ′ precipitates in the matrix by slowing down the coarsening process. An obvious break was observed in the creep rate curves with different stress exponents (n). Below the break in the low-stress regime (LSR), stress exponent (n) was ∼3, whereas it increased to 9–12 above the break in the high-stress regime (HSR). In the LSR, the creep was controlled by the dislocation climbing, and it transformed into the Orowan looping in the HSR.