Specific Mass Loss Research Articles

The oxidation-resistant Mo30Si60B10 coating for protection of the T2 phase-based molybdenum alloy

This study focuses on fabrication of a Mo30Si60B10 coating with elevated silicon content, which enhances working properties of Mo-alloy based on the Т2 phase (t-Mo5SiB2). The Mo30Si60B10 coating has a columnar structure. The alloy is characterized by hardness of 17 GPa; Young's modulus of 304 GPa, and elastic recovery of 29 %. Deposition of the coating increased hardness by 40 %; the Young's modulus, by 18 %; and elastic recovery, by 25 %. Oxidation tests at 1200 °C demonstrated that the specific mass loss of the alloy with Mo30Si60B10 coating was 1.5-fold lower than that of the uncoated alloy. An 18 μm thick oxide layer based on a-SiВO and containing MoO2 particles was formed on the alloy surface. The coating contributes to a ∼14-fold reduction of oxide layer thick. The increase in oxidation resistance of alloy after coating deposition is related to sealing of substrate defects and formation of an a-SiВO layer with elevated silicon content.

Microstructure, wettability, cavitation and corrosion performance of aluminum (Al6061) coated with RF-sputtered AlN thin film

This study addresses the challenge of enhancing aluminum substrates with AlN coatings for improved durability. Novel RF-sputtered AlN coatings were developed, demonstrating deposition with equiaxed crystals and a predominant presence of aluminum and nitrogen. The coatings exhibited hydrophobic properties as shown by contact angle measurements. Cavitation erosion resistance was systematically analyzed, revealing optimal parameters for minimizing mass loss, including jet velocity, impingement angle, and stand-off distance, thereby showcasing the protective role of the RF-sputtered AlN coating. Response Surface Methodology (RSM) provided insights into the correlation between operational parameters and mass loss, leading to process optimization with specific mass loss values and high desirability percentages. XPS analysis of corroded AlN on Al-6061 revealed aluminum compounds, sodium, NaCl, and oxidation products, aligning with SEM/EDS results and confirming the coating's effectiveness in mitigating corrosion. Carbon and oxygen were the most abundant elements by weight and peak area. Overall, this study offers valuable insights into the multifaceted performance and protective capabilities of RF-sputtered AlN coatings.

Comprehensive Understanding of the Heavy Oil Combustion Process: Reaction Behavior, Kinetic Triplet, and Mechanism Implication.

In this work, thermo-oxidative behavior, kinetic triplet, and free radical mechanism of ultraheavy oil during an in situ combustion (ISC) process were systematically surveyed via multiple thermal analysis techniques (TG/DTG/DSC/PDSC), model-free methods, and related mathematical simulation. First, specific mass loss, exothermic intensity, and corresponding temperature intervals were respectively determined in low-/high-temperature oxidation (LTO/HTO) regions. In addition, the comparison of atmospheric/pressurized differential scanning calorimetry (DSC/PDSC) experiments indicated that the pressurized conditions could obviously strengthen the oxidation progress with more heat emission. Then two model-free methods were contrastively employed for PDSC data to calculate LTO and HTO activation energy variations with the conversion rate. Moreover, the acceleratory rate model for LTO and the Sestak-Berggren model for HTO were accordingly picked as the most probable mechanism functions, which were later used to determine the simulated curves. Then, the simulations of α-T and dα/dT-T curves were respectively attained using Friedman equation in MATLAB software and contrasted with experimental data to validate the accuracy of the yielded kinetic triplet and forecast the combustion behavior. Further, the evolution pathways of the underlying oxidation mechanism was illustrated. This study updates the understanding of the nonisothermal combustion process, contributing to the subsequent numerical simulation and feasible investigation for in situ combustion implementation to enhance heavy oil recovery.

Effect of nanoparticles and siloxane groups on the atomic oxygen erosion resistance of copolyimides

The properties, resistance to atomic oxygen (AO) in particular, of copolyimides based on 4,4′-(9-fluorenylidene)dianiline, 3,3′,4,4′-diphenyloxide tetracarboxylic acid and hexamethylenediamine (PI-1), 4,4′-(9-fluorenylidene)dianiline, 3,3′,4,4′-tetracarboxylic acid diphenyloxide and 1,3-Bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (PI-2) were studied. Tris-(methyldiethoxysiloxy)gallium and tetrakis-(methyldiethoxysiloxy)hafnium were used as precursors for in situ filling of the polymers. The filling of copolyimides leads to an order of magnitude decrease in the specific mass loss of nanocomposites under the AO action. The filled PI-2 shows the better resistance to AO compared to the PI-1 nanocomposite. Based on the analysis of the erosion rates of polymer films, it was shown for the first time that at low fluences the resistance of filled PI-2 to atomic oxygen erosion is determined by the filler, whereas at high fluences the protective function is based on both components of the nanocomposite (filler and matrix). In the case of nanocomposites based on siloxane-free PI-1, their resistance to atomic oxygen erosion is caused by the nanoparticles, regardless of the fluence value.

Cr-Co Oxide Coatings Resistant to Corrosion, Electrodeposited on 304 SS Using an Ethylene Glycol-Water Solvent

The electrochemical co-deposition of Cr-Co oxide coatings at room temperature on 304 stainless steel (SS) was studied using an electrolyte composed of a mixture of ethylene glycol (EG), hydrated metal chloride salts (MCln∙YH2O), and water as a secondary hydrogen donor (HBD). Metallic Cu and Ni undercoats were applied to improve the adhesion of a posterior Cr-Co metallic and oxide layer. The electroactive events that took place during both electrodeposition processes were studied using cyclic voltammetry (CV) and chronoamperometry. The microstructure and composition of the surface layers were studied using scanning electron microscopy (SEM/EDS), X-ray diffraction (XRD) and cross-sectional elemental mapping via transmission electron microscopy (TEM). The surface of steel with the Cr-Co:EG-H2O coating showed greater resistance to pitting corrosion (123.93 mV) compared to untreated stainless steel (62.3 mV). This sample showed a large hystere-sis area, which is associated with high resistance to pitting corrosion by the occurrence of a re-passivation of the sample at a Erep value of 24.31 mV. After the cyclic potentiodynamic polariza-tion (CPP) test, the lowest specific mass loss (0.001 mg/cm2) was achieved for the AISI 304 SS sample coated using EG-water solvents (Cr-Co:EG-H2O), while the untreated AISI 304 SS reached a higher specific mass loss (0.01 mg/cm2). The Electrochemical Impedance Spectroscopy (EIS) tests showed that the uniform corrosion resistance varied significantly from the untreated AISI 304 SS (35 kΩ) to the coated sample (57 kΩ), which is attributed to the protection provided by the chromium and cobalt oxides coating. The best corrosion resistance achieved was correlated with a superhydrophobic character (with a contact angle of 158.41°) of the Cr-Co coatings. This was in turn a consequence of a needle-like morphology characteristic of these oxides.

Effect of calcination on the physical, chemical, morphological, and cementitious properties of red mud

Red mud (RM), a by-product of aluminum production, poses environmental concerns with its disposal. This study explored calcining RM at 600 °C for 0–6 hours to utilize it as a cement substitute. Calcination up to 2 hours decreased particle size and increased surface area due to moisture loss, while further calcination reversed these effects. XRF analysis showed high Fe2O3, Al2O3, SiO2 contents. XRD revealed goethite transformed to hematite and gibbsite to alumina. SEM images displayed a loose then denser structure over time. 10% calcined RM incorporated into cement showed 2-hour calcined RM exhibited optimal properties, including high strength (46.27 MPa) and strength activity index (117.24%). SEM confirmed improved C-S-H gel formation with 2-hour calcined RM. In summary, calcining RM optimally at 600 °C for 2 hours allows its effective use as a sustainable cementitious material, providing environ- mental and technical benefits of RM utilization in cement composites.

A study on predicting the wear of TBM disc cutters using Cerchar testing

Estimating the disc cutter wear life or change time is a critical part of performance prediction for the application of hard rock TBMs. This paper examines the disc cutter wear rate and the number of required discs during the excavation of the Kanisib (or Zab) tunnel based on the transpositioning concept. The study covers the disc changes due to the normal wear process, leaving out those replaced due to mechanical/bearing failures. This study also analyzes TBM field performance and actual cutter consumption using a method, specific mass loss per volume (SMLV) excavated. SMLV considers the wear mass of a disc cutter relative to the disc cutters replacement for a given volume of excavated rock. Generally speaking, the disc SMLV incorporates critical parameters, and a formula is introduced to calculate it from the rock properties. The new model can be utilized for estimating disc life for any disc cutter size, diameter, and tip width. The predictive model developed in this study allows for estimating cutter life based on the location of disc cutters on the cutterhead. The proposed model uses rock mass parameter, namely the rock quality designation (RQD), and rock material parameters measured in a laboratory, including rock abrasion and strength. Rock abrasion is estimated by Cerchar abrasivity index (CAI) or modified Cerchar abrasivity index (MCAI). Furthermore, a new approach to Cerchar indices has been used, which is based on the pin mass loss instead of pin tip flat size, and as a result, new indices called CAIML and MCAIML are introduced. The correlation between predicted and observed values shows that the proposed model for specific mass loss per volume can predict the normal wear of disc cutters. Furthermore, the Cerchar indices calculated using the pin mass loss offered better correlations with field data than those specified based on the diameter of the pin tip flat. Overall, MCAIML exhibited the best correlation with the field observations compared to the other Cerchar indices.

Tribological Properties of PLA 3D Printed at Different Extrusion Temperature

Fused deposition modelling (FDM) 3D printing is widely used to manufacture prototype. To manufacture functional products with FDM 3D printing, several existing challenges have to be solved. Tribological behaviour of 3D printed parts has to be improved and optimised. In current study, friction and wear behaviours of 3D printed polylactic acid (PLA) printed at different extrusion temperature (190°C, 200°C, 210°C, 220°C, 230°C) sliding against steel disc were investigated. Pin on disc experiments that complies with ASTM G99-95a (2000) were conducted at a normal load of 15 N, and rotational speed of 150 RPM (0.69 m/s). Results showed that increasing the extrusion temperature resulted in a lower pin wear (specific mass loss) and higher friction coefficients. Pins printed at 190°C showed to have the biggest pin mass loss and lowest friction coefficients, whereas pins printed at 230°C showed to have the lowest pin mass loss and highest friction coefficients. This indicates the higher the extrusion temperature, the more capable it is for the deposited material to flow and homogenise with the neighbouring material which creates a flatter surface with less void between layers. Thus, effectively improving the interlayer bond making the FDM 3D printed part less susceptible to shear stress and delamination.

Shear capacity of corroded high-strength bolted connections

The bolted connection is one of the most commonly adopted connection types in steel structures. The high strength bolted connection is always used in important steel structures. Corrosion is inevitable for bolted connections. To clearly reveal the influence of corrosion on the clamping force of high strength bolts, the stochastic numerical model of randomly corroded bolt connections is established. The whole corrosion process can be simulated through the established stochastic numerical model. The influences of uniform corrosion and random corrosion are analyzed. The change rule of clamping force along with mass loss ratio is analyzed. The random distribution of clamping force corresponding to specific mass loss ratio of bolt head is clarified. The probabilistic distribution of clamping force of randomly corroded bolts is revealed. The simplified numerical model of bolt group connection is proposed. The stochastic numerical analysis can be performed based on this simplified model. The results indicated that it is unsafe if the random pitting corrosion is simplified as uniform corrosion. The corrosion location has obvious on the changing rule of residual clamping force.

Effect of diamond like carbon coatings on reducing sliding fit joint interfacial wear damage on Al5083 alloy

Wear is an important concept and is being given importance in different manufacturing industries. In every mobile joint, studies in interaction between sliding surfaces are very important. This is due to the wear that occurs in between the sliding surfaces. A lot of sliding fit joints are fabricated and used in production companies and transportation industries. In this manuscript, an attempt has been made to reduce sliding wear of Al 5083 alloy materials by coating it with diamond like carbon material. Using high velocity oxy fuel thermal spray coating, diamond like carbon materials were coated over Al 5083. Then it was subjected to wear testing by using pin on disc wear testing equipment. Wear tests were conducted by using petroleum lubricant and also in dry conditions. A considerable improvement in wear resistance was observed on using diamond like carbon coatings. Using scanning electron microscopy, the alloy Al 5083 material was evaluated for microstructural variations on conducting wear studies, before and after coating it with diamond like carbon material, with and without lubrication. The variations in coefficient of friction, specific wear rate and wear mass loss were studied under lubrication and without lubrication, with and without diamond like carbon coating. Microstructural evaluation of wear tested surfaces exhibited micro wear, micro voids, coating pull outs, abrasive wear and micro cracks.

Intrinsic Smoke Properties and Prediction of Smoke Production in National Bureau of Standards (NBS) Smoke Chamber

Smoke production in a smoke chamber is characterized by the accumulation of smoke and the continuous consumption of oxygen leading to a vitiated atmosphere. However, a method is proposed to predict the smoke evolution in a smoke chamber at 25 kW/m2 by using material properties calculated from a cone calorimeter, as already shown in a previous article. These properties represent the ability of a material to produce smoke at a specific mass loss rate. The influence of a flame retardant on these properties can be used as a quantitative measurement of its action on smoke production. These properties can be calculated at another heat flux than 25 kW/m2. The knowledge of the curve “mass loss rate = f(time)” in a smoke chamber is still required, but this curve is close to that measured in a cone calorimeter at the same heat flux. The results prove that the smoke production in a smoke chamber and cone calorimeter is qualitatively similar, i.e., the decrease of oxygen content in a smoke chamber has no influence on smoke (at least as long as optical density does not exceed 800).

The Contribution of New Breed Purple Wheat (8526-2 and 8529-1) Varieties Wholemeal Flour and Sourdough to Quality Parameters and Acrylamide Formation in Wheat Bread

The aim of this study was to evaluate the influence of purple wheat (varieties 8526-2 and 8529-1) wholemeal flour (PWWF) left untreated or fermented with Lactiplantibacillus plantarum No. 135 on the quality parameters of and acrylamide formation in wheat bread. Different quantities (5, 10, 15, and 20%) of PWWF were tested for bread preparation. Acidity, colour characteristics, hardness, enzyme activities, and antioxidant activity of PWWF, as well as bread quality and acrylamide concentration, were analysed. Differences in LAB count and amylolytic and proteolytic enzyme activities between two varieties of non-treated and fermented PWWF were not found. Fermentation increased DPPH-scavenging activity and reduced hardness of both PWWF varieties. A very strong positive correlation was found between total phenolic compound content and antioxidant activity in PWWF (r = 0.816, p = 0.001). In most cases, PWWF addition lowered bread specific volume and mass loss after baking. After 72 h of storage, bread with 5% PWWF showed the lowest hardness. Addition of 15% PWWF to bread increased overall acceptability. Fermentation and wheat variety significantly affected bread crumb a* colour coordinates. Addition of fermented PWWF significantly decreased acrylamide formation in bread (p ≤ 0.0001), and bread with 5% PWWF variety 8526-1 had the lowest acrylamide content. In conclusion, the addition of new-breed PWWF to wheat bread improved certain quality parameters, while PWWF fermented with L. plantarum possessed DPPH-scavenging activity and can be recommended for acrylamide reduction in wheat bread.

Applied smouldering for co-waste management: Benefits and trade-offs

Smouldering combustion is emerging as a valuable application for many environmentally beneficial purposes, including waste-to-energy. While many applied smouldering systems rely on small fractions of fuel mixed within inert porous media (IPM) like coarse grain silica sand, there is also an opportunity to pursue co-waste management with much higher fuel loadings. This study explores these co-waste systems by blending non-smoulderable wastes (e.g., sewage sludge) with smoulderable wastes (e.g., construction waste woodchips) to form porous solid fuels (PSFs). Key differences between these IPM and PSF systems were identified by contrasting the temperature profiles in space and time, specific mass loss rates, and emissions profiles across experiments in multiple reactors (with 0.054, 0.080, and 0.300 m radii). For example, the PSF systems exhibited higher throughputs, a more straightforward path towards continuous operation, improved scalability, and higher production of potentially useful by-products (e.g., CH4, H2) than the IPM systems. However, the PSF systems were more sensitive to extinction and exhibited lower fuel moisture content limitations than the IPM systems. Altogether, this study illuminates the benefits and trade-offs of co-waste smouldering.

On the specific heat and mass loss of thermochemical transition

Poly(vinyl alcohol) PVA is a synthetic polymer used in a variety of applications and exhibits unusual thermal behavior. In this work, differential scanning calorimetry (DSC), isothermal and non-isothermal thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), optical microscopy, viscometry and kinetic modeling were used to study the thermal behavior of PVA for providing further insights about the thermochemical transition. It is shown that the value of specific heat of thermochemical transition is comparable to theoretical values derived from chemical bond dissociation energy values. Activation energy's contribution to the specific heat of thermochemical transition seems to be low. Contradictions among the conclusions from various analytical techniques, regarding the glass transition of PVA, are discussed and interpreted. Settlement of these contradictions leads to the conclusion that like PVA's melting point, its glass transition is also a thermochemical transition but with no detectable mass loss.

The contribution of edible cricket flour to quality parameters and sensory characteristics of wheat bread.

This study evaluated the influence of edible cricket flour (ECF) on the quality parameters and sensory characteristics of wheat bread (WB), including the formation of volatile compounds (VC) and their relationship with emotions (EM) induced for consumers. ECF reduced dough pH, redness, and yellowness. At 5%, ECF increased the porosity of WB (by 7.87%). The quantity of ECF significantly affected WB's specific volume (p=.030), porosity (p=.0001), shape coefficient (p=.0001), and mass loss (p=.023). All WB with ECF had a more intense color and additive odor. Bread samples with 10% and 15% ECF had more intense overall, additive, acidity, and bitterness flavors. However, all WB had similar overall acceptability (OA) and no correlations were found between OA and VC. The EM "happy" and "sad" were expressed more intensely for WB with 15% ECF, and significant correlations were established between the EM "happy" and separate VC. The main VC in WB were ethanol; 1-butanol and 3-methyl; 1-hexanol; estragole; and hexanoic acid. Finally, 5% ECF could be incorporated into the main WB formula without having a negative impact on bread quality. Also, ECF influences VC formation, and separate VC could be related to emotions induced for consumers.

Design and development of novel LiCl–NaCl–KCl–ZnCl2 eutectic chlorides for thermal storage fluids in concentrating solar power (CSP) applications

Molten chloride mixtures are of great scientific and technical interest for sensible heat storage in solar power generation. In this work, the condensed phases in a LiCl–NaCl–KCl–ZnCl 2 multicomponent system were critically evaluated and predicted via literature review and simulations of LiCl–KCl and KCl–ZnCl 2 systems. Two innovative LiCl–NaCl–KCl–ZnCl 2 quaternary chloride systems with low melting points were proposed and developed on the basis of a thermodynamic design. The thermal–physical properties of these two eutectic compositions, including melting point, mixing enthalpy, specific heat capacity, density, thermal conductivity, and mass loss, were then experimentally determined. The experimental results were consistent with the theoretical predictions. The novel quaternary eutectic chlorides with excellent thermophysical properties developed herein are potential candidates for thermal energy storage and transfer materials in concentrating solar power plants. • Thermodynamic prediction of LiCl–NaCl–KCl–ZnCl 2 system was performed via CALPHAD. • Two novel quaternary eutectic chlorides were successfully designed for thermal energy storage and transfer. • Thermophysical properties of the system were determined by experiment and classical prediction method. • Thermodynamic performance of the novel chlorides was substantially improved compared with other potential materials. • The novel quaternary eutectic chlorides were proposed as potential candidate materials in CSP applications.

Glacier–permafrost relations in a high-mountain environment: 5 decades of kinematic monitoring at the Gruben site, Swiss Alps

Abstract. Digitized aerial images were used to monitor the evolution of perennially frozen debris and polythermal glacier ice at the intensely investigated Gruben site in the Swiss Alps over a period of about 50 years. The photogrammetric analysis allowed for a compilation of detailed spatio-temporal information on flow velocities and thickness changes. In addition, high-resolution GNSS (global navigation satellite system) and ground surface temperature measurements were included in the analysis to provide insight into short-term changes. Over time, extremely contrasting developments and landform responses are documented. Viscous flow within the warming and already near-temperate rock glacier permafrost continued at a constant average but seasonally variable speed of typically decimetres per year, with average surface lowering limited to centimetres to a few decimetres per year. This constant flow causes the continued advance of the characteristic convex, lava-stream-like rock glacier with its oversteepened fronts. Thawing rates of ice-rich perennially frozen ground to strong climate forcing are very low (centimetres per year) and the dynamic response strongly delayed (timescale of decades to centuries). The adjacent cold debris-covered glacier tongue remained an essentially concave landform with diffuse margins, predominantly chaotic surface structure, intermediate thickness losses (decimetres per year), and clear signs of down-wasting and decreasing flow velocity. The former contact zone between the cold glacier margin and the upper part of the rock glacier with disappearing remains of buried glacier ice embedded on top of frozen debris exhibits complex phenomena of thermokarst in massive ice and backflow towards the topographic depression produced by the retreating glacier tongue. As is typical for glaciers in the Alps, the largely debris-free glacier part shows a rapid response (timescale of years) to strong climatic forcing with spectacular retreat (>10 m a−1) and mass loss (up to >1 m w.e. specific mass loss per year). The system of periglacial lakes shows a correspondingly dynamic evolution and had to be controlled by engineering work for hazard protection.

Experimental analysis on combustion characteristics of diesel and kerosene under different radiation intensity of heat source

With the help of cone calorimeter, combustion experiments of 0# diesel and kerosene (3# jet fuel) under external heat radiation were completed, and the main combustion performance parameters, such as heat release rate, specific mass loss rate, effective heat of combustion, time to ignition, combustion duration and fire spread risk, were obtained under different heat source radiation intensities. The change rules of the main combustion characteristics of these tow fuels with the increase of heat source radiation intensity were discussed, and the differences of the main combustion characteristics between the diesel and kerosene were compared and analyzed. The results show that the average heat release rate, peak heat release rate and specific weight loss rate of the diesel and kerosene increase linearly with the increase of heat source radiation intensity, and the increasing trend (slope) of kerosene is larger than that of diesel. The time to reach the peak heat release rate, ignition time and combustion duration of the both fuels decreased exponentially with the increase of heat source radiation intensity. Under the same radiation intensity, the heat release rate, specific mass loss rate and effective heat combustion of kerosene are higher than those of diesel, while the time to reach the peak heat release rate, ignition time and combustion duration of kerosene are lower than those of diesel. The total heat release of kerosene is higher than that of diesel under different heat source radiation intensities, and the average total heat release of kerosene is about 6.17% higher than that of diesel. THR/tlast and pkHRR/TTI of the two fuels showed an exponential relationship, and the fire spread risk of diesel was less than that of kerosene.

Study on wear behavior of low nickel austenitic stainless steel by using ball on disc

Austenitic stainless steels have wide applications in various industries due to its good corrosion characteristics and their surface strength. A variety of procedures are used to enhance the surface characteristics. Wear studies are critical in all of the toughest materials. Surface damage was studied in terms of material-removal methods such plastic deformation and brittle fracture. This paper investigated the specific wear rate of Low Nickel ASS. The parameters selected for wear testing like sliding speed, load, time duration and types of ball. Six numbers of experiments were conducted for measuring specific wear rate, mass loss and coefficient of friction were highlighted in this paper. A comparison study was made to know the effect of wear parameters like sliding speed, load, time duration and types of ball on specific wear rate and coefficient of friction. It was seen that with increasing of load and sliding speed of disc the specific wear rate of the material significantly increasing.SEM analysis was also made on worn surface to know the behaviour of wear in the sample.

Specific gravity, Extractive Content, and Natural Durability of Balsa (Ochroma pyramidale) Wood at 3 and 4 years old

The aim was to investigate the specific gravity, extractive content, and natural durability of balsa (Ochroma pyramidale) wood. A total of six trees of balsa at 3 and 4 years old were harvested and cut into the sample of specific gravity, extractive content, and natural durability test. Natural durability was tested according to SNI 01-7207-2006 against dry wood termites (Cryptotermes cynocephalus Light.). Specific gravity, extractive content, mass losses, and termite mortality were measured. Variance analysis was used to find the differences. The results showed that age influenced significantly on specific gravity and mass losses, while axial direction/position influenced significantly on extractive content and mass losses. Variance analysis also showed that radial direction influenced significantly on specific gravity and extractive content. The specific gravity of three years balsa wood is 0.14, which is lower than that of four years old three, which is 0,19. Extractive content in the bottom part (3.95%) is higher than that of in the middle (2.87%) and top (2.74%). Mortality in the bottom part (33.83%) is higher than that of in the middle (10.5%) and top part (5,8%) of the stem. In general, balsa wood is classified into durability class II-III.