Cavitation Resistance Research Articles

Cavitation‐resistant junipers cease transpiration earlier than cavitation‐vulnerable oaks under summer dry conditions

AbstractAshe juniper (Juniperus ashei Buchholz) and escarpment live oak (Quercus fusiformis Small) are two of the most common woody species of the Edwards Plateau, an arid‐to‐semi‐arid region of nearly 100,000 km2 in central Texas. They have very different hydraulic strategies, yet they experienced similar mortality rates during an extreme drought in 2011. We measured J. ashei and Q. fusiformis sap flow velocities during summer dry periods of 2016 and 2017 at six micro‐sites. Although these were years with more‐or‐less average summer conditions, both included significant dry periods. To estimate the relative rate of decrease in sap velocity for each species during the dry periods, we fit a Bayesian exponential decay model to the sap velocity time series for each tree. We found that Q. fusiformis trees were better able to maintain transpiration than J. ashei during dry periods at five micro‐sites and were comparable at the sixth micro‐site. We conclude that it is likely that Q. fusiformis can better maintain transpiration during dry periods than J. ashei, on average, and that in the case of these two species, greater cavitation resistance may not translate to greater drought resistance.

Derived woodiness and annual habit evolved in African umbellifers as alternative solutions for coping with drought

BackgroundOne of the major trends in angiosperm evolution was the shift from woody to herbaceous habit. However, reversals known as derived woodiness have also been reported in numerous, distantly related clades. Among theories evoked to explain the factors promoting the evolution of derived woodiness are moderate climate theory and cavitation theory. The first assumes that woody habit evolves in response to mild climate allowing for prolonged life span, which in turn leads to bigger and woodier bodies. The second sees woodiness as a result of natural selection for higher cavitation resistance in seasonally dry environments. Here, we compare climatic niches of woody and herbaceous, mostly southern African, umbellifers from the Lefebvrea clade to assess whether woody taxa in fact occur in markedly drier habitats. We also calibrate their phylogeny to estimate when derived woodiness evolved. Finally, we describe the wood anatomy of selected woody and herbaceous taxa to see if life forms are linked to any particular wood traits.ResultsThe evolution of derived woodiness in chamaephytes and phanerophytes as well as the shifts to short-lived annual therophytes in the Lefebvrea clade took place at roughly the same time: in the Late Miocene during a trend of global climate aridification. Climatic niches of woody and herbaceous genera from the Cape Floristic Region overlap. There are only two genera with distinctly different climatic preferences: they are herbaceous and occur outside of the Cape Floristic Region. Therefore, studied herbs have an overall climatic niche wider than their woody cousins. Woody and herbaceous species do not differ in qualitative wood anatomy, which is more affected by stem architecture and, probably, reproductive strategy than by habit.ConclusionsPalaeodrought was likely a stimulus for the evolution of derived woodiness in the Lefebvrea clade, supporting the cavitation theory. The concurrent evolution of short-lived annuals withering before summer exemplifies an alternative solution to the same problem of drought-induced cavitation. Changes of the life form were most likely neither spurred nor precluded by any qualitative wood traits, which in turn are more affected by internode length and probably also reproductive strategy.

Cavitation Resistance of WC-10Co4Cr and WC-20CrC-7Ni HVAF Coatings.

Machines operating in aqueous environments may be subjected to cavitation damage during operation. This study aims to evaluate the cavitation resistance of WC-10Co4Cr and WC-20CrC-7Ni coatings under cavitation erosion conditions with additional electrochemical effects. The coatings were deposited on AISI 1040 steel substrates using a high velocity air fuel thermal spray process. The microstructure of the coatings was observed by a scanning electron microscope, while their phase composition was analyzed using an energy-dispersive microanalysis system. In addition, the microhardness of the coatings and substrate was measured, and the surface topography of the eroded surface layers was observed using a 3D optical profilometer. The results revealed that the cavitation resistance of the WC-20CrC-7Ni coatings was better than that of the WC-10Co4Cr coatings. The observation of the structure and surface topography made it possible to identity the reasons for the differences between the cavitation resistance of both coatings: The WC-20CrC-7Ni coatings had a finer grain structure, lower pore density, and lower as-sprayed surface roughness. These differences, along with the presence of a high Cr and Ni content in the feedstock powder, that increased the coating corrosion resistance, contributed to improving the cavitation resistance and reducing the material loss of the WC-20CrC-7Ni coatings.

The intraspecific variation of functional traits modulates drought resilience of European beech and pubescent oak

Abstract A higher frequency and intensity of droughts will impair forest productivity. Therefore, improving our understanding of which factors enhance tree growth resilience against drought has become a crucial issue, but we lack information at the intraspecific level. In this study, we investigate the role played by climatic conditions and tree characteristics in the growth response to severe droughts in two deciduous Fagaceae species near their southern distribution limit: the temperate European beech Fagus sylvatica and the Mediterranean pubescent oak Quercus pubescens. The study area is located in Catalonia, NE Spain, where 149 trees were cored covering the water availability gradient of the species in the region. In addition, tree size (diameter and height) and an ensemble of stem, leaf and hydraulic traits were collected for each tree. Growth responses to extreme droughts during the period 1980–2015 were assessed using resilience indicators based on residual basal area increment series predicted by a model including growing season water balance. Although resistance was unrelated to drought intensity, higher water availability improved recovery and reduced drought legacy effects. Taller trees showed higher resilience against drought, which could be explained by the relationship between the variation in tree height and functional traits, such as leaf nitrogen concentration, leaf turgor loss point and resistance to xylem embolism. For both species, trees with lower cavitation resistance, higher leaf nitrogen concentration and tighter stomatal regulation (suggested by less negative turgor loss point and carbon isotope composition) displayed better performance during and after severe droughts. Both species showed a progressive decrease in resilience and increase in legacy effects. Synthesis. This study highlights the relevance of analysing intraspecific variation of functional traits involved in tree water and carbon balance to improve our understanding of the resilience and variability of growth responses to drought within species.

Parenchyma underlies the interspecific variation of xylem hydraulics and carbon storage across 15 woody species on a subtropical island in Japan.

Parenchyma is an important component of the secondary xylem. It has multiple functions and its fraction is known to vary substantially across angiosperm species. However, the physiological significance of this variation is not yet fully understood. Here, we examined how different types of parenchyma (ray parenchyma [RP], axial parenchyma [AP] and AP in direct contact with vessels [APV]) are coordinated with three essential xylem functions: water conduction, storage of non-structural carbohydrate (NSC) and mechanical support. Using branch sapwood of 15 co-occurring drought-adapted woody species from the subtropical Bonin Islands, Japan, we quantified 10 xylem anatomical traits and examined their linkages to hydraulic properties, storage of soluble sugars and starch and sapwood density. The fractions of APV and AP in the xylem transverse sections were positively correlated with the percentage loss of conductivity in the native condition, whereas that of RP was negatively correlated with the maximum conductivity across species. Axial and ray parenchyma fractions were positively associated with concentrations of starch and NSC. The fraction of parenchyma was independent of sapwood density, regardless of parenchyma type. We also identified a negative relationship between hydraulic conductivity and NSC storage and sapwood density, mirroring the negative relationship between the fractions of parenchyma and vessels. These results suggest that parenchyma fraction underlies species variation in xylem hydraulic and carbon use strategies, wherein xylem with a high fraction of AP may adopt an embolism repair strategy through an increased starch storage with low cavitation resistance.

The role of crystal orientation and grain boundaries in the cavitation resistance of EN 1.4301 austenitic stainless steel: An EBSD study

Characterization of crystal orientation and grain boundaries is of great interest in the understanding of the mechanisms taking place during the degradation process originated by the exposure of materials to erosive media. In the present study, an austenitic stainless steel previously analyzed by electron backscatter diffraction was exposed to ultrasonic cavitation erosion. Several parameters such as crystal orientation, misorientation, coincidence site lattice, Schmid factor and twin orientation were examined in order to determine their influence on the local susceptibility to early damage induced by cavitation. Crystallographic orientation was found to play a significant role in the deformation mechanisms occurring inside grains. Furthermore, high misorientation between adjacent grains was recognized as a determining factor leading to early damage observed at random grain boundaries, while the difference in Schmid factor was identified to have a significant effect on the cavitation resistance of twin boundaries. Moreover, the effect of the deviation from the ideal orientation predicted for coherent twins was analyzed in connection with cavitation resistance.

Contrasting Water Use, Stomatal Regulation, Embolism Resistance, and Drought Responses of Two Co-Occurring Mangroves

The physiological mechanisms underlying drought responses are poorly documented in mangroves, which experience nearly constant exposure to saline water. We measured gas exchange, foliar abscisic acid (ABA) concentration, and vulnerability to embolism in a soil water-withholding experiment of two co-occurring mangroves, Avicennia marina (Forsskål) Vierhapper (Verbenaceae) and Bruguiera gymnorrhiza (L.) Savigny (Rhizophoraceae). A. marina showed higher photosynthesis and transpiration than B. gymnorrhiza under well-watered conditions. Cavitation resistance differed significantly between species, with 50% cavitation occurring at a water potential (P50) of −8.30 MPa for A. marina and −2.83 MPa for B. gymnorrhiza. This large difference in cavitation resistance was associated with differences in stomatal closure and leaf wilting. The rapid stomatal closure of B. gymnorrhiza was correlated with ABA accumulation as water potential declined. Meanwhile, stomatal closure and declining water potentials in A. marina were not associated with ABA accumulation. The safety margins, calculated as the difference between stomatal closure and embolism spread, differed between these two species (1.59 MPa for A. marina vs. 0.52 MPa for B. gymnorrhiza). Therefore, A. marina adopts a drought tolerance strategy with high cavitation resistance, while B. gymnorrhiza uses a drought avoidance-like strategy with ABA-related sensitive stomatal control to protect its vulnerable xylem.

Influence of the polymer matrix type on cavitation resistance of composites

Cavitation resistance of polymer matrix / basalt powder composites was determined in this work. Two types of composites were tested: epoxy resin / basalt powder composite and polyester resin / basalt powder composite. In both cases, a basalt powder was used as reinforcement in the resin (grain size 20μm, in the amount of 15 wt%). An ultrasonic vibration method with a stationary sample was used to test the cavitation resistance of composites in laboratory conditions. The change in sample mass with test time was monitored to define cavitation rate. Scanning electron microscopy was used to monitor the morphology of composites surface damage.

Microstructural and Cavitation Erosion Behavior of the CuAlNi Shape Memory Alloy

Microstructural and cavitation erosion testing was carried out on Cu-12.8Al-4.1Ni (wt. %) shape memory alloy (SMA) samples produced by continuous casting followed by heat treatment consisting of solution annealing at 885 °C for 60 min and, later, water quenching. Cavitation resistance testing was applied using a standard ultrasonic vibratory cavitation set up with stationary specimen. Surface changes during the cavitation were monitored by metallographic analysis using an optical microscope (OM), atomic force microscope (AFM), and scanning electron microscope (SEM) as well as by weight measurements. The results revealed a martensite microstructure after both casting and quenching. Microhardness value was higher after water quenching than in the as-cast state. After 420 min of cavitation exposure, a negligible mass loss was noticed for both samples. Based on the obtained results, both samples showed excellent cavitation resistance. Mass loss and morphological analysis of the formed pits indicated better cavitation resistance for the as-cast state (L).

Stude of water-oil emulsion using wave treatment dispersant

THE PURPOSE. To develop an apparatus for wave treatment of water-fuel oil and preparation of water-fuel emulsion for combustion. To present a scheme of an innovative vortex burner device for water-oil emulsion combustion. To review existing equipment for preparation of high quality emulsion. Refute the necessity of forced dehydration of fuel oil for high-quality combustion in burners. To present data on the choice of material for manufacturing the dispersant body, taking into account the requirements for corrosion resistance, as well as resistance to cavitation and wear resistance. To develop an experimental setup for the preparation of water-oil emulsion for combustion in a vortex burner. To conduct an analysis to identify the relationship of transformation of physical and chemical properties of water-oil emulsion (sedimentation and aggregative stability, structural viscosity) from temperature and volume of water in them. METHODS. Theoretical methods of viscosity and density determination were used in solving the problem and results were obtained experimentally, by using a capillary viscometer, in different temperature ranges of emulsified fuel preparation. A method was used to assess the clarification of the WFE to evaluate the sedimentation stability, with compulsory conditioning in glass cylinders in a statistical state. RESULTS. The preparation of WOE is conditioned by the water content rationing. The factor of partial loss of moisture at the plant during emulsion preparation can be considered as a positive side effect of dewatering. Data on the density of water-oil emulsion depending on the concentration of water at 70 0C has been obtained. The analysis of dependence of stability of emulsion based on fuel oil M-100 from time of settling at 20 0C is made. CONCLUSION. The presented wave dispersant experimentally demonstrates a high quality of VME preparation. Experimental results prove the presence of a significant numerical increase of the 10 μm particle size, as well as a minimum conversion of 1.25 μm particles towards the 2.5 μm particle size. The use of wave treatment dispersant results in stable water-oil emulsions suitable for use as fuels in the power industry.

Time–temperature superposition for cavitation resistance of metals with nonequilibrium vacancy concentrations

Here, we provide a systematic molecular dynamics (MD) study of the pulse duration and temperature dependence of spall strength in Al and Mg with a nonequilibrium concentration of vacancies. A superconcentration of single vacancies are randomly introduced into an otherwise perfect lattice, and the systems are allowed to evolve for up to 500 nanoseconds as a proxy for the pulse duration of a shock compression wave. Since these systems are nonequilibrium in nature, a time-dependent and temperature-dependent evolution of the microstructure ensues, which leads to a time- and temperature-dependent softening of the spall strength. Here, we report a large parametric study consisting of 196 MD calculations to quantify this softening in Al and Mg. We invoke the notion of time–temperature superposition from the field of viscoelasticity, and show that the results of our 196 MD calculations remarkably collapse onto a single master curve when normalized by an appropriate relaxation timescale. Lastly, a favorable agreement between the MD calculations and experimental measurements of thermal softening of spall strength is reported.

Subalpine dwarf shrubs differ in vulnerability to xylem cavitation: An innovative staining approach enables new insights.

Dwarf shrubs are a key functional group of the high-elevation vegetation belt. Despite their ecological relevance and high sensitivity to environmental changes, the hydraulic adaptations and species-specific variations in drought tolerance within this growth form are mostly unknown. Here, we assess the xylem vulnerability to cavitation of important character species of the Alpine dwarf shrub heaths in Central Europe. Due to the high percentage of nonfunctional xylem areas in these species, vulnerability curves were gained by an innovative staining approach with safranin, validated by hydraulic and xylem anatomical measurements. The loss of 50% conducting xylem area appeared in the range of -1.78 to -2.91 MPa. Midday plant water potential during an intense summer drought remained above these critical thresholds but was correlated with cavitation resistance. No trade-off between hydraulic safety and efficiency was detected across analyzed species. We conclude that the characteristic clustered occurrence of species in the heterogeneous mountain terrain (mainly interpreted as a consequence of varying snow cover dynamics) is also reflected in species-specific adjustments in xylem hydraulics. The interspecific variety in vulnerability thresholds and plant water potentials during summer drought indicates different hydraulic strategies and adjustments in water relations between these co-occurring shrubs.

Primary tissues may affect estimates of cavitation resistance in ferns.

Different methods of measuring cavitation resistance in fern petioles lead to variable results, particularly with respect to the P50 metric. We hypothesised that the fern dictyostele structure affects air entry into the xylem, and therefore impacts the shape of the vulnerability curve. Our study examined this variation by comparing vulnerability curves constructed on petioles collected from evergreen and deciduous ferns in the field, with curves generated using the standard centrifuge, air-injection and bench-top dehydration methods. Additional experiments complemented the vulnerability curves to better understand how anatomy shapes estimates of cavitation resistance. Centrifugation and radial air injection generated acceptable vulnerability curves for the deciduous species, but overestimated drought resistance in the two evergreen ferns. In these hardy plants, axial air injection and bench-top dehydration produced results that most closely aligned with observations in nature. Additional experiments revealed that the dictyostele anatomy impedes air entry into the xylem during spinning and radial air injection. Each method produced acceptable vulnerability curves, depending on the species being tested. Therefore, we stress the importance of validating the curves with in situ measures of water potential and, if possible, hydraulic data to generate realistic results with any of the methods currently available.

Comparative Analysis of Cavitation Resistance of Deposited/Sprayed Layers of Carbides, Stainless Steels and Metastable Austenite

The cavitation erosion resistance of deposited/sprayed layers prepared by thermal spraying and welding processes was evaluated using a new principle of ultrasonic vibratory testing [1]. A high velocity air fuel thermal spraying process (HVAF), gas tungsten arc welding (GTAW or TIG), and shielded metal arc welding (SMAW) were used to prepare the deposit deposited/sprayed layers. The WC-10Co4Cr powder was deposited on 20X13 stainless steel, while E308L-17 welding filler electrode, 06X19H9T welding solid wire, and Fe-Cr-Al-Ti cored wire (known as PPM-6) were deposited on AISI 316L stainless steel. For all materials, the curves of volume loss as a function of testing time were plotted. The obtained results showed that the deposited layers of PPM-6 metastable austenite steel prepared by TIG welding process was exhibited a higher resistance to cavitation erosion than the others. The maximum volume loss of PPM-6 steel was about 0.31 mm1, whereas the volume loss for the other materials was of 5-20 times high.

Ultrasonic Cavitation Behavior and its Degradation Mechanism of Epoxy Coatings in 3.5 % NaCl at 15 ℃

Pipes operating in the seawater environment faces cavitation degradation and corrosion of the metallic component, as well as a negative synergistic effect. Cavitation degradation shows the mechanism by which materials deteriorate by causing rapid change of pressure or high-frequency vibration in the solution, and introducing the formation and explosion of bubbles. In order to rate the cavitation resistance of materials, constant conditions have been used. However, while a dynamic cavitation condition can be generated in a real system, there has been little reported on the effect of ultrasonic amplitude on the cavitation resistance and mechanism of composites. In this work, 3 kinds of epoxy coatings were used, and the cavitation resistance of the epoxy coatings was evaluated in 3.5% NaCl at 15 oC using an indirect ultrasonic cavitation method. Eleven kinds of mechanical properties were obtained, namely compressive strength, flexural strength and modulus, tensile strength and elongation, Shore D hardness, water absorptivity, impact test, wear test for coating only and pull-off strength for epoxy coating/carbon steel or epoxy coating/rubber/carbon steel. The cavitation erosion mechanism of epoxy coatings was discussed on the basis of the mechanical properties and the effect of ultrasonic amplitude on the degradation of coatings.

Vulnerability to xylem cavitation of Hakea species (Proteaceae) from a range of biomes and life histories predicted by climatic niche.

Extreme drought conditions across the globe are impacting biodiversity, with serious implications for the persistence of native species. However, quantitative data on physiological tolerance are not available for diverse flora to inform conservation management. We quantified physiological resistance to cavitation in the diverse Hakea genus (Proteaceae) to test predictions based on climatic origin, life history and functional traits. We sampled terminal branches of replicate plants of 16 species in a common garden. Xylem cavitation was induced in branches under varying water potentials (tension) in a centrifuge, and the tension generating 50 % loss of conductivity (stem P50) was characterized as a metric for cavitation resistance. The same branches were used to estimate plant functional traits, including wood density, specific leaf area and Huber value (sap flow area to leaf area ratio). There was significant variation in stem P50 among species, which was negatively associated with the species climate origin (rainfall and aridity). Cavitation resistance did not differ among life histories; however, a drought avoidance strategy with terete leaf form and greater Huber value may be important for species to colonize and persist in the arid biome. This study highlights climate (rainfall and aridity), rather than life history and functional traits, as the key predictor of variation in cavitation resistance (stem P50). Rainfall for species origin was the best predictor of cavitation resistance, explaining variation in stem P50, which appears to be a major determinant of species distribution. This study also indicates that stem P50 is an adaptive trait, genetically determined, and hence reliable and robust for predicting species vulnerability to climate change. Our findings will contribute to future prediction of species vulnerability to drought and adaptive management under climate change.

An investigation on the possibility to improve the corrosion and cavitation resistance of SS304 steel by NiTi coatings

Equiatomic and near equiatomic NiTi alloys, showing good mechanical and thermal shape memory properties, are widely exploited in different industrial applications. In addition, NiTi alloys have promising anti-cavitation and corrosion-resistance properties. These advantages have provided opportunities to exploit NiTi alloys as the coatings for protecting materials used in the industrial applications. This study is a preliminary investigation aiming to evaluate the feasibility to form NiTi alloy coatings on SS304 steel by tungsten inert argon arc welding (TIG) technology. The microstructure analysis shows that the crystalline phases in NiTi coatings on SS 304 steel are TiNi-B2, TiNi-B19’ and Ni3Ti. The potential of the NiTi coatings to enhance the corrosion resistance and cavitation resistance behaviors of steel exposed to seawater is studied. NiTi coatings, with two different thicknesses of about 1.2 and 2 mm, having homogenous microstructures were successfully deposited on SS304 steel using TIG technology. Results of tests, done in aqueous solutions simulating seawater, showed that the formation of the oxide films on the surface of NiTi coatings increased the corrosion resistance and wear resistance and decreased the damage caused by the cavitation. Moreover, it was understood that the NiTi coatings with 2 mm in thickness show the superior performances than those with 1.2 mm in thickness. The tribological mechanisms responsible for the unique properties of NiTi alloy coatings were investigated. The wear-resistance behaviors of NiTi alloy coatings are greatly influenced by the friction conditions. Increasing load decreased CoF and the wear rate of the coatings were almost constant, which was attributed to the pseudoelasticity of NiTi alloy. The attractive properties of NiTi alloys that makes it most influential materials for industrial applications have also been discussed.

Experimental and numerical investigations of cavitation evolution in a high-speed centrifugal pump with inducer

Along with the anti-cavitation performance, the high speed and the high power density, are the main trends in the development of centrifugal pumps. At present, the most effective method is to install an inducer in front of the impeller. However, the tip leakage of the inducer results in the vortex cavitation at the blade leading edge of the inducer, and the cavitating flow inside the inducer seriously interferes with the hydraulic behavior of the inducer as well as the impeller with the development of the cavitation, thus to badly affect the operational reliability of the high-speed centrifugal pump. In the present paper, the cavitating flow in a high-speed centrifugal pump with an inducer is investigated by numerical simulations and visual experiments for different cavitation numbers. A typical evolution process of the cavitation is shown, including the inception, the development and the deterioration. A general description of the pump head-drop phenomenon is made through the study of the local and global flow fields, and the relationship between the vapor distribution and the static pressure distribution along the inducer is determined to describe the evolution of the cavitation. This paper intends to provide the foundation for studying the overall cavitation state of a high-speed centrifugal pump, and designing the inducer with a better cavitation resistance.

Comparison of FeMnCrSi Cavitation Resistance Coatings Deposited by Twin-Wire Electric Arc and High-Velocity Oxy-Fuel Processes

The hydraulic runners and many other components are exposed to cavitation phenomena and the erosion occurs, and normally are repaired by arc welding processes. However, the heat input from the welding causes microstructural changes in the components materials. Considering the martensitic stainless steel CA6NM, the welding thermal cycle reduces its fracture toughness and consequently the structural integrity of the equipment. Thermally sprayed coatings are an alternative to repair low eroded areas of these components, since the thermal sraying processes do not change the substrate microstructure and/or mechanical properties as the welding process. Different FeMnCrSi alloys deposited by Twin-Wire Electric Arc (TWEA) or High-Velocity Oxy-Fuel (HVOF) are on development and their cavitation resistance, comparable to the substrate CA6NM, are the object of the study in this research. This work presents the comparison of the deposition characteristics and properties of different FeMnCrSi alloys chemical compositions coatings obtained by TWEA and HVOF processes, evaluating the particles in-flight, morphology, hardness, adherence, and cavitation resistance of the coatings.

Optimization Design and Simulation of Cavitation Resistance of Aviation Fuel Centrifugal Pump

Optimization Design and Simulation of Cavitation Resistance of Aviation Fuel Centrifugal Pump