Journal articles on the topic 'Mechanicalproperties'

It was proposed the design of an artificial neural network (ANN) to estimate the yield strength in the welding zone of HSLA experimental steels. The input parameters of the ANN were the chemical composition and hardness. The information needed to training and testing the ANN was obtained by searching the literature of the yield strength as a function of the input parameters. The design was of the type perceptron multilayer with a rule learning of backpropagation type and sigmoidal transfer function, varying the number of nodes in the hidden layer. It was determined that the design of the ANN with 11 nodes is able to estimate the yield strength of high strength low alloy steels and ultra-high strength steels according to their chemical composition and hardness.

Abstract The article presents an analysis of properties of welded joints of fine-grained steel of P460NH type used more and more often in the modern constructions. A process of examining a technology of welding has been carried out on the thick-walled butt joints of sheet metal by two methods of welding namely MAG – 135 and SAW – 121. The article deals with a topic of optimizing a process of welding thick-walled welded joints of fine-grained steel due to their mechanicalproperties and efficiency.

The successful use of Nickel-Titanium (Nitinol) in biomedical applications requires an accurate control of its unique mechanical properties. The purpose of this study is to analyze the effects of a wide range of heat treatments on the mechanical behaviour of Nitinol. We have taken two different grades of Nitinol with different heat treatment history and surface characteristics. The sample with protective oxide coating showed higher elastic strain with comparatively large hysteresis.

At this article we give a brief review about the additives effects for cast polyamide 6engineering plastics. The natural grade Magnesium catalyzed polyamide 6 has unique mechanicalproperties. Our target is to keep the mechanical and tribological properties with the development ofantistatic and ESD composite version. High conductive very effective to improve the electricalconductivity of magnezium catalized cast PA 6. Only few amount, 0,5% can result good antistaticproperty for the base matrix. Over 3% of additive the surface resistance of the material – performing107 Ω - can reach the ESD (Electrostatic Dissipative) category.

Some features ofstructure, way of production and mechanical properties of titanium andtwo-phase titanium alloys with ultrafine-grained (UFG) microstructure werediscussed. Various methods of UFG structure formation was considered andoptimal conditions for attaining of a homogeneous microstructure with thesmallest grain size were determined. The kinetics of microstructure evolutionin titanium and two-phase titanium alloys during large (severe) plasticdeformation in a wide temperature interval and the mechanisms of ultrafinegrain formation were analyzed. The influence of grain size on static mechanicalproperties was determined. Significantly reduced temperatures of superplasticforming of the UFG conditions were shown. Some examples of practical applicationsof the UFG two-phase titanium alloys were discussed.

Both in the domestic and world steel industry alternative ecologically clean free-cutting steels, having cutting machinability characteristics and mechanicalproperties, comparable with lead-containing steels, but voided of their drawbacks,are actively searched. First ofall the alternative steels should not be not so ecologically harmful. Scientific and technological aspects of lead-free free-machining steels production, alloyed by bismuth, calcium, tin, boron and nitrogen presented. Solubility of bismuth in iron and iron alloys with chromium, manganese, nickel, tungsten, vanadium, cobalt,phosphor, sulphur, aluminum, carbon and other elements at the temperature of 1550–1650 ºСdetermined. Parameters of interaction of the first and second order calculated. Study of bismuth behavior and tin spherical samples in 40X steel melt accomplished. The study done at the high temperature facility with controlled atmosphere and X-ray TV observation system. Simulation of phase compositions multicomponent alloys of steel АВЦ40ХГНМaccomplished by application of a program package FactSage. Within the study,a production technology of lead-free, ecologically clean free-machining, steels elaborated and masteredat OJSC “Zlatoust electro-metallurgical works”. Free-machining corrosion-resistant steels (АВЦ19ХГН, АВЦ40Х, АВЦ40ХГНМ, АВЦ12Х18Н10, АВЦ40Х13, АВЦ14Х17Н2) alloyed by bismuth and calcium, steels (АО40Х, АО30ХМ) alloyed by tin, and steels (А38ХГМАРand А30ХМАР) containing BN were the objects of the study. The steels samples were in the form of forged billet of 10, 20 and 80 mm diameter and ingots of 18 and 500 kg (round 345 mm). Steel quality characteristics determined such as mechanicalproperties in longitudinal and cross directions of ingots, uniformity of distribution of fusible elements, carbon and Sulphur along the axis zone and in billet transverse sections. Pictures of ingots macrostructure by height and section obtained. Estimation of hardenability and steel contamination by non-metallic inclusions, austenitic grain size, steel machinability by cutting, surfacequality of re-worked billet and steel macrostructure accomplished. Comparable ecological studies of atmosphere contamination during the steel alloying also accomplished.

Purpose: In this paper the Metal Matrix Composites of AL 7068 and TiC with differentproportions of (2%, 4%, 6%, 8%, and 10%) by using stir casting process, mechanicalproperties and machining responses are investigating.Design/methodology/approach: The samples are fabricated using stir casting, machiningof turning the samples by using Kilster Tool Lathe Dynamometer machining responses wereidentifying.Findings: In this research to find mechanical characterizations like flexural strength, Wearratio, impact strength, hardness, microstructure and also machining responses like surfaceroughness, cutting force, cutting power, tool wear ratio and can be optimized by multipleresponses.Research limitations/implications: This paper research about the mechanicalcharacterization and machining of AL-7068&TiC that focuses on machining responses andmicrostructures.Originality/value: By surveying the research articles the gap will be identified inAA-7068&TiC depended on machining responses and mechanical characterizations.

This research aimed to produce and determine physical and mechanical properties of three-layered particleboard produced with Pinussp. wood particlesand three different times of press, i.e., 3, 5 and 7 minutes. Recommendations of the Brazilian standard ABNT NBR 14810 [1] were adopted to fundament physical and mechanical tests. The properties evaluated were the modulus of rupture (MOR) and modulus of elasticity (MOE) in static bending; internal bond; thickness swelling; water absorption; moisture content and apparent density.The mean values showed, for the physical properties, that all the panels manufactured achievedthe requirements of theBrazilian standard, and for mechanical properties, only the panelsmanufacturedwith 7minutesofpressing timemet therequirements. From the Tukey test results, timesof the pressingcycleinfluencedsignificantlyin allinvestigatedphysical and mechanicalproperties, showed better results the panels madewithseven minutesof the pressingcycle, implyingthat the time ofseven minutesof the pressingcycle is thebest among theinvestigatedperiodsin the manufactureofparticleboard.

This work appears as an experimental attempt to verify the validity of thetheoretical model used to interface ratio proposed by Chicot and Lesage. For this, wepresent a study on the mechanical properties of interface from the instrumentedpenetration tests. One of the important points of the study is related to the characteristicsof materials with micro deformations and influence of defects on the mechanicalproperties. Discussions are developed concerning the intrinsic properties, particularlythe behavior of the modulus of elasticity for different situations in which the materialsare. Were used for development work, samples taken from sucker rods, which are usedin oil production equipment. These rods were coated with two types of materials, thebasis of a NiCr alloy and the other with Al, both obtained by thermal spray process (arcspray). With the use of instrumented penetration testing was carried out indentations inthe coatings, substrate and interface of each sample. With these results, the model wasapplied and theoretical interfacial later tried to verify its validity.

Rainwater infiltration modelling for slope stability analysis in Coc Pai town-Xin Man distict-Ha Giang provinceRainfall plays an important role in formation of landslides by substantially changing the physico-mechanicalproperties of the soil such as soil weight, cohesion, friction angle, pore water pressure etc. For a given soil, thoseparameters are functions of soil moisture. Raiwater infiltration makes the change in soil moisture in space, especialliy in the depth and in time. One specific rainfall event shall give a specific rainwater infiltration and moisture distribution and therfore creates a specific distribution of physico-mechanical properties. Numerical moisture movement under given rainfall event whould give a precise moisture ditribution in soil and therefore can effectively serve the slope stability analysis and prediction. Rainwater infiltration and soil moisture movement modeling for the peak rainfall event in 2008 inCoc Pai town, Xin Man district, Ha Giang province has been carried out, which provides an important input for effectiveslope stability analysis and prediction of the area.

Concept of bulk material and complexity of storing it are explained. The dependence between the physical and mechanicalproperties of the loose material and type of construction in which it is stored. Structural elements considered silos and siloswith conical and flat bottom are described. The common characteristics of metal silos for bulk materials are given. The classification of metal silos by type of housing design is given. The advantages and disadvantages of silos are described.The possibility of storage of bulk materials in cylindrical shells is analyzed depending on the type of construction. The history of occurrence of structures of spiral-fold silos is considered. The set of equipment for the construction of the housing ofthe spiral-fold silos is given, the step-by-step process of formation of the folding lock and features of the installation processare presented. The analysis of the structure is made and the advantages and disadvantages of spiral-fold silos are determined.

The present investigation aims at evaluating and understanding the thermo-mechanical be-haviour of a titanium alloy under hot forming conditions. In this work, several considerations are ad-dressed. First, Scanning Electron Microscopy observations are performed to assess the evolutions of(α − β) phases, grain size, defects regarding the thermo-mechanical loadings from different static anddynamic tests (various temperatures and strain rates). Hence, the relationships between mechanicalproperties and micro-structure evolutions in such conditions allow a first assessment of the deforma-tion mechanisms in link with the macroscopic stress-strain curves. Afterwards, a behaviour modelformulation associated to an identification procedure of the parameters of the constitutive equationsis proposed. Finally, several tests performed under hot forming conditions and conducted on an in-dustrial press are compared to Finite Element calculations. Results are compared and provide someinteresting improvement ways in order to investigate the influence of the process parameters on thefinal shape of the part.

Natural rubber (polymer designation cis-1-4 polyisoprene, is obtained from the sap ("latex") of several rubber-yielding plants (e.g.,HeveaBrasiliensisandPartheniaargentatum) by coagulation with chemicals, drying, electrical coagulation, and other processes. Foamy or sponge structure of natural rubber (NR) is very useful in aerospace and as auxetic materials (exhibiting negative poisons ratio) for use in application of homeland security.The main aim of this research to estimate the influence of carbon black on mechanical properties, curing and viscosity variation behaviors of the natural rubber based composites. Different amounts of carbon black were used along with other fillers. The influence of carbon black on curing behavior and mechanicalproperties of natural rubber foams was investigated at different feedingratios of the carbon black. The physical properties of the foamed NRs were then measured as a function of carbon blacks content. The mechanical properties of the foamed NRs such as tensile strength,strength at break and modulus,were gradually increased with increasingcarbon black content whereas elongation decreasedat break.

Hydrogel matrices were designed as hybrid networks of poly(ethylene oxide) (PEO) with natural polymers,alginate or chitosan by UV irradiation. The networks were formulated in the single-stage procedure inwhich the alginate or chitosan were added to the crosslinking reaction solution of PEO, and two-stage procedure,with additional chemical crosslinking of alginate or chitosan. Double-layer hydrogels composed of PEOhydrogel core with entrapped cells and outer natural hydrogel layer were also synthesized. The hydrogels werecharacterized by gel fraction yield and degree of equilibrium swelling as well as by rheological measurements.The production of ethanol by immobilized Saccharomyces cerevisiae was used to test the suitability of the synthesizedhybrid hydrogels to serve as carriers for cell immobilization. The presence of cells affected the mechanicalproperties and the structure of the polymer networks. The best system for immobilization was found to bethe PEO/alginate/Ca, which exhibited high mechanical strength (G′, 830; GF, 93; ESH2O, 15) without affectingthe metabolic functions of the cells. The maximum ethanol yield was 0.42 g/g corresponding to 82 % of thetheoretical yield.

Pipelines are constructed in hostile environments where the occurrence of imposed plasticdeformations can necessitate a strain based design approach. Under such conditions not only the strengthand toughness properties have to be considered; also the strain capacity of pipe and weld metal becomecrucial. Considering the use of spirally welded linepipe sections, the helical seam weld and anisotropicmaterial properties pose real challenges to pipeline designers. In our work, the tensile strain capacity anddefect tolerance of high strength, high toughness spiral pipes will be investigated. This paper brieflydiscusses the different steps in the spiral pipe manufacturing process and their influence on the mechanicalproperties of the pipe. The forming angle is a key parameter as it determines (a) the anisotropy in strengthand toughness of the pipe steel, and (b) the orientation of possible seam weld defects. Each mechanicaloperation (forming, expansion) and each thermal operation (welding, coating) will affect local or globalstrength, toughness and ductility properties of the pipe metal. A thorough material characterization at eachprocess step is needed for a qualitative and quantitative understanding of these effects.

The effect of DC pulsed GTAW method factors on mechanical properties of Aluminumalloys 6061–T6 is proves. Throbbed GTAW on the sheet having dimension of (200* 100*5mm) is implemented at variable pulse current (150, 160, 170, 190) and constant frequencyto get numerous connected joints by electrode type" ER4043 (Al Si5) as a padding metallicand argon as protective gas and compared with base current GTAW welding at D C currentat 90 amps. The welded pieces are examined by X-ray radiography. The welded joints weretreated by heat, the joints heated for half an hour in the furnace to 150 C° then cooled in theair to release the residual stresses. Mechanical quality of the weld joints. Microstructuralcategorizations, Micro hardness, enduring stress are examined. Consequences exposed thata common decline of mechanical properties of TIG welded joints conveyed 34% analogieswith parent metal while the PGTAW joined offers better mechanical qualities analogy withof TIG joined in reductions conveyed 8.4% analogies with original metal this is because ofthe microstructure variations through the joining method and compressive residual stressgeneration in the weld zones. It has been found that by PGTAW improved the mechanicalproperties of welded joints which rely on current parameters.

In this study, nano-composite of polymeric materials, prepared from unsaturated polyesterresin (UP). Two groups of nanocomposites were prepared by Hand Lay-up method. The firstgroup consists from (UP) reinforced by hybrid nanoparticles consisting of a mixture ofzirconium oxide and yttrium oxide (30 mol%Y2O3- ZrO2) with particles size (83.98nm). Thesecond group consists of (UP) reinforced by zirconia nanoparticles (ZrO2) with particle size(47.23nm). The effect of volume fraction (0.5%, 1%, 1.5%, 2%, 2.5%, 3%) of thenanoparticles additives on some mechanical properties of composites materials was studiedalso. The results shown that the values of the flexural modulus, impact strength and fracturetoughness increased, as the volume fraction ratio of the nanoparticle increased for bothgroups of nanocomposites, while flexural strength values decreased with the increased thevolume fraction ratio of the nanoparticles for both groups of nanocomposites also. As wellas, the unsaturated polyester resins reinforced by hybrid nanoparticles has higher mechanicalproperties as compared with their counterparts of composites reinforced by zirconiananoparticles only. The morphological formation of the fracture surface showed a closeinterconnection between all components of the prepared polymeric compositions. Thisreinforce a good compatibility between unsaturated polyester resins and reinforcementnanoparticles, which enhancement the mechanical properties.

The engineering parts joining by the spot welding require acceptable properties to survive the loading conditions XE "temperature". Several studies show that the welding variables have an effect on the properties of spot nugget XE "nugget" and on the future cracking. This review summarizes the resistance spot welding process (RSW). It introduces the basic spot welding principles, experiments XE"experiments" , limitation and defects XE "defects". The new concepts and awareness were presented. The results from the series of scientific works and literature are discussed. The metal’s weldability, XE "spotweldability" strength, XE"strength" and fracture are the main topics in several structural analysis. The welding variables effect on the mechanical properties and performance XE "mechanicalproperties" of the structures is the key analysis. In general, the increasing of the heat input by adjusting the current, time, and pressure producing higher weld area in turn enhance the toughness. However, by increasing the weld area, the defects and cracking tend to appear. Hence, a desired weld size with the mechanical properties is required. The nugget fracture mode is changing from plug or button tearing to shear failure mode depending on the weld properties. The crack grows either from the internal defects or around the nugget.

Purpose: The purpose of the work was to evaluate the compressive strength of metalceramicconnections in the fixed dental restorations.Design/methodology/approach: Restorations were made on a model of the naturalpatient's dentition which was developed specifically for this study. The study included 10metal - porcelain crowns, for each group of teeth. Their production used Remanium 2000+alloy and porcelain Vita VMK Master. A static compression test was carried out on the finalcrowns and Vicker's hardness test was performed. Visual observations were carried out ona scanning electron microscope.Findings: On the basis of the research and the discussion it was possible to concludethat metal-porcelain crowns have a greater compressive strength than natural human teeth.Thus, they are more resistant to occlusal forces and the crowns for the first molars are thestrongest restorations.Practical implications: The metal-porcelain crowns are a very good option for teethrestoration and they can be used even in the areas of the mouth where the occlusal forcesreach the maximum values.Originality/value: The article focuses on testing of compressive strength of metal-ceramiccrowns. The comparison with natural human occlusal forces shows the sufficient mechanicalproperties of metal-ceramic crowns for application in humans. The artificial tooth geometryallows applying prosthetic crowns in the patient's mouth without the risk of ceramic breakdown.

The objectives of this study were to estimate the effect of the blue light cure unit on the compression force and hardness for composite resin nanoCeram at different thickness. The basic material used in this study was Ivoclar Vivadent Tetric N-Ceram Light Cured Hybrid restorative composite resin. The samples were cured by applying a (LED.F) unit Blue phase in a wavelength emission spectrum (494 NM) was used.60 disc-shaped specimens [9 mm diameter at (0.5, 1) mm thickness and 10 mm diameter at (1.5) mm thickness] were prepared using a stainless steel mold for hardness and compressive strength measurements. A composite resin was polymerized with an aid of a ( DC 5V/1A) lamp for (10, 20 and 30) sec .Three specimens were used for each group.The results were analyzed using (linear logarithmic, quadratic, linear and power) test.The different groups showed significant variability in relation, with a significant interaction between the groups.The result showed that the greater thickness more efficient for polymerization than small thickness and the long irradiation time more efficient for polymerization than short irradiation time, long irradiation time diffusion in deep portions of the sample convert to polymer and this provide good polymerization and then good mechanicalproperties.

Membrane technology is growing rapidlybecause of its superiority and has beenwidely applied in various industries. Thewaste of teak sawdust is increasing as thefurniture industry develops, but its utilizationis not optimal. The purpose of this study wasto determine the effect of the addition of TiO2on the mechanical properties andperformance of photocalytic membranesfrom cellulose diacetate teak sawdust forprocessing PDAM water raw materials.Cellulose isolation from teak sawdust wascarried out by adding NaOH 17.5% (b / v)and continued with cellulose bleachingprocess. Cellulose teak sawdust wassynthesized into cellulose diacetate byacetylation method. Membrane production isdone by phase inversion method withvariations in the composition of TiO2 0.25%,0.5%, 0.75% and 1% and also variations inevaporation time 20 seconds, 25 seconds,30 seconds and 35 seconds. The photocyticmembrane of cellulose diacetate from teaksawdust and TiO2 produced wascharacterized by thickness test, mechanicalproperties and performance. Photocalyticmembranes with optimum conditions arecharacterized by SEM (Scanning ElectronMicroscopy), FT-IR (Fourier TransformInfraRed) and antibacterial effectiveness.The optimum composition of thephotocatalytic membrane is 16% cellulosediacetate, 4% formamide, acetone 79% and1% TiO2 with 30 seconds evaporation time.The mechanical properties obtained werestress 1562,50000 kN / m2, strains 0.01 m /m and Young Modulus 141593,4835 kN /m2. The membrane has an averagethickness of 0.04 mm, a flux value of 683.10L.m2.hari-1, a rejection value of 97.74% andan antibacterial effectiveness of 99.57%.

Sawdust is a waste from furnitureindustry which is mostly left in the garbage or burn for landfill in hugequantities every year. Efforts to find utilization of this material haveresulted mostly in low value. However, sawdust waste can be considered as analternative to fabricate fiber reinforced polymer composites for furniturefunction. This study was undertaken to determine the physical and mechanicalproperties of wood plastic composites, which were made under laboratoryconditions by hot pressing of high-density polyethylene (HDPE) with teakwoodsawdust as filler. Seven levels of mixed flour, 10, 20, 30, 40, 50, 60 and 70%,based on the composition by weight was added to the HDPE powder with palm oilas coupling agent. A flat pressing technology, the simplest method for capableof large dimension wood plastic panel production, was used to manufacturetesting specimens in dimensions 5.8 x 7.3 cm2. Investigation of themechanical property of the composites material, according to the Americansociety for testing and materials (ASTM) method, was done by impact strengthtester. The measurement results were found that impact strength was decreased uponthe increasing of the sawdust up to 30 % mixing then gradually increased. However,by increasing mixed flour content, water resistance of the panels wasnegatively influenced. The best appearance of composites material in comparisonwith the natural woods was ~30% sawdust powder mixing. The woodplastic panels were utilized for construction of a Thai spirithouse as an outdoor decoration.

In this study, the flame-retardant treatment for cotton fabric has been done by using the commercial organophosphoruscompounds labelled Pyrovatex CP New (PR). Knittex FFRC (K), a formaldehyde-free crosslinking agent, has been usedto enhance the link between Pyrovatex CP New and Cellulose molecules. The flame-retardant treatment process forcotton fabric has been done by the pad-dry-cure technique. The purpose of the study is to predict the optimal PyrovatexCP New and Knittex FFRC concentrations with the highest fire resistance efficiency, minimum loss for mechanicalproperties and minimum formaldehyde release for the treated fabric. To achieve this goal, the response surfacemethodology (RSM) was used to find the relationship between the controlled experimental factors and the observedresults. The central composite design type face centred (CCF) was applied as experimental design. According to thisexperimental design, 10 experiments were carried out. The chemical uptake rate, vertical flammability characteristics,LOI value, tensile strength and formaldehyde-free content of the untreated and treated samples were determined. Fourresponse models between the reagent concentrations and the add-on amount, LOI value, warp and weft tensile strengthof the treated fabric were obtained by the assistance of software Design-Expert V 10.0.8. The R-squared values of thesemodels were above 80% confirming their significances. The optimal conditions when combining three parameters (LOI,warp tensile strength and weft tensile strength) were selected as 450 g/l Pyrovatex CP New and 107,575 g/l KnittexFFRC with the assistance of Design-Expert software

Background. The disinfection of orthodontic acrylic resins might change the physical and mechanicalproperties of these materials. We aimed to investigate the impact of four different commercially availabledisinfectants on the surface roughness of acrylic resins used for orthodontic appliances. Methods. Four disinfectant solutions (BirexSE, Opti-Cide3, COEfect MinuteSpray, and CaviCideSpray) were used to disinfect orthodontic acrylic resins using the spraying method. The resins weresubjected to repeated disinfection protocols. Distilled water, also applied via spraying method, was usedas a control. Surface roughness was scrutinized to examine the extent of surface topography changes bystylus profilometry. Data normality was evaluated via the Shapiro–Wilk test, followed by the WilcoxonSigned-Rank test for non-parametric data or paired Student’s t-test for parametric data to compareintra-group differences in roughness before and after the use of the disinfectant solutions. Results. Some of the disinfectants (BirexSE and CaviCide) resulted in significant changes in surfaceroughness values before and after the disinfection compared to the controls (P<0.05). The groups thatwere in contact with distilled water, Opti-Cide, and Coeffect did not exhibit significant differences insurface roughness before and after the intervention (P>0.05). However, from a clinical perspective, theresulting variations in surface roughness (<%0.15) induced by these solutions might not reflect clinicallysignificant differences. Conclusion. The use of disinfectant solutions is unlikely to harm the surface of orthodontic acrylic resins.Oral care providers need to be attentive to the interpretation and implementation of clinically significantchanges in their evidence-based approach regarding potential material damages by disinfection sprays.

The research is aimed to search of optimal solution in integration of various methods for predicting the sizes of karst-suffosion deformations on the ground surface or at the base of shallow foundations. Necessity of integration is dictated by engineering-geological conditionsof the karst areas and the complexity of their reliable study with using modern approaches (drilling, geophysics etc.). From this point of view increasing of authenticity of the final forecast is in direct dependency from completeness of investigation of sizes of observed surface karstforms and features of behavior soils massif above the karst cavity. The mechanism of the karst process in the soils thickness is defined, first of all, by geological structure (thickness and interleaving of different soil layers), hydrogeological conditions and the physical-mechanicalproperties of soils. At the present day are known three basic mechanisms of soil deformation over karst cavity: karst-collapse, karst-suffosion and karst-suffosion-collapse mechanism. Even in the conditions of one site these mechanisms can be interleave during the year, which makesthe karst formation process hard-to-predict in part of diameters of sinkholes and subsidence zones. Today are known and applicable next four methods to estimations of possible sizes of karst-suffosion deformations: 1) method of analogy, 2) probabilistic method, 3) deterministic(calculated) method, 4) laboratory physical modeling method. Each of four methods for predicting the sizes of karst-suffosion deformations has its own advantages and disadvantages, which limit the possibility of using any one of them in different natural environments of karstdevelopment. To improve objectivity and reach necessity accuracy of estimation of diameters and depths of surface karst deformations in engineering-geological purposes a block-scheme of integrations of different forecasting methods is recommended. This scheme is based on the data about surface karst area, the depth of occurrence of karst rocks and level of responsibility of the projecting object.

The effects of clay and limestone dusts in the aggregates on the physico -mechanical characteristics of concretewere investigated. The fine aggregates (dune sand) and coarse aggregates (crushed gravels) used in this study were washed, dried and sieved.Twodifferent mineralogical compositions of dusts (clay and stone) were incorporated in different rates(0%, 5%, 10%, 15%, 20%, 25% and 30%) by replacementin weight of fine(dune sand) and coarse (crushed gravel) aggregates. The presence of clay and limestone dust particles in the fine and coarse aggregates inexcessive quantities influencedthe physico –mechanicalpropertiesof fresh and hardened concrete. The results obtained showed that the effect of clay dust content is more important compared to limestone dust content on the properties of concrete.

This article provides the review of the medical use of pH- and temperature-sensitive polymer hydrogels. Such polymers are characterised by their thermal and pH sensitivity in aqueous solutions at the functioning temperature of living organisms and can react to the slightest changes in environmental conditions. Due to these properties, they are called stimuli-sensitive polymers. This response to an external stimulus occurs due to the amphiphilicity (diphilicity) of these (co)polymers. The term hydrogels includes several concepts of macrogels and microgels. Microgels, unlike macrogels, are polymer particles dispersed in a liquid and are nano- or micro-objects. The review presents studies reflecting the main methods of obtainingsuch polymeric materials, including precipitation polymerisation, as the main, simplest, and most accessible method for mini-emulsion polymerisation, microfluidics, and layer-by-layer adsorption of polyelectrolytes. 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The role of the materials used for packaging is to protect innercontent from external, mostly negative, factors. Besides beingsafe, and with good mechanical properties, these materials needto align with other consumers’ needs and demands, being bothattractive and authentic, while at the same time meetingecological requirements. Gelatin-based thin films are goodcandidates for production of semi-soft cup-shaped products thatcould be used for cruciferous vegetables packaging. These filmswere prepared by a simple solvent evaporation method. Preparedfilms were characterized by swelling study and their mechanicalproperties were investigated. The optical characteristics of thefilms were determined by optical microscopy revealing that thesesystems possess attractive clear and transparent gold-yellowishappearance with a smooth surface.

SUMMARYObjective: The purpose of this in vitro studywas to compare the tensile strength betweentwo materials for the manufacture ofacrylic denture bases (Veracril® from NewStetic and SR Triplex Hot® from IvoclarVivadent), and to know the mechanicalproperties of materials to study that haveclinical implications.Methods: Laboratory tests were conductedunder the technical standard of ASTMInternational # D 638-03 to evaluate thetwo acrylic resin materials for denturebases, processed by pressed moulding. Theobservations were made using the universaltesting machine Tinius Olsen® brandH50KS to analyze the tensile propertiessuch as modulus of elasticity, elongation,yield strength, maximum strength, energy,effort and tensile stress between the twomaterials evaluated.Results: For the effort, maximum strengthand modulus of elasticity, high-impactacrylic resin SR Triplex Hot® showedhigher values. With regard to the characteristicsof maximum displacementbefore the fracture, elongation and energy,conventional acrylic resin showed highervalues. The only characteristic that showeda significant difference between the twogroups of thermo-cured acrylic resin wasthe modulus of elasticity where the highimpactacrylic resin obtained a much highervalue than conventional acrylic resin.Conclusions: The acrylic resin SR TriplexHot® presents higher values in some tensileproperties, while the Veracril® showsbetter in others. The only characteristic thatshowed a significant difference betweenthe two acrylic resins was the modulus ofelasticity.Keywords: Acrylic resin denture bases,tensile strength, high impact acrylic resin.

International audience This work concerns the field of recycling of waste intobuilding materials. It reports on the possibility ofrecovering plastic waste and related products fromthe wood industry, in construction. The objective ofthe study is to give added value to wood-plasticcomposites produced using the cold compressionmolding process, by improving their mechanicalproperties. Through the bending test, the influence oftwo manufacturing parameters - compactionpressure and drying temperature after molding - onthe mechanical properties, was evaluated for the caseof a composite based on tropical wood sawdustcoming from Benin and recycled polystyrene (CBPo).It appears that the compaction pressure and thedrying temperature are essential factors to considerwhen evaluating the mechanical performance of thecomposite. Increasing the compaction pressure to alimit value significantly improves the properties of thematerial. The optimal properties of CBPo wereobtained at a pressure of 7 MPa. Post-forming dryingat 100 ° C also significantly improved the performanceof the composite. In addition, thanks to its enhancednew mechanical properties, the CBPo is repositionedrelatively to other existing materials, thus making itpossible to think about new applications inconstruction. Ce travail concerne le domaine du recyclage dedéchets en matériaux. Il rend compte d’unepossibilité de valorisation de déchets plastiques et deproduits connexes de l’industrie du bois dans laconstruction. L’étude vise à donner une valeurajoutée à un composite bois-plastique élaborésuivant un procédé de moulage par compression àfroid, par l’amélioration de ses propriétésmécaniques. A travers un essai de flexion, l’influencede deux paramètres de fabrication - pression decompactage et température de séchage postmoulage- sur les propriétés mécaniques, a étéévaluée dans le cas d’un composite à base de sciuresde bois tropicaux venant du Bénin et de polystyrène(CBPo) recyclés. Il en ressort que la pression decompactage et la température de séchage, sont deuxfacteurs essentiels à considérer lors de l’évaluationdes performances mécaniques du composite.L’augmentation de la pression de compactage jusqu’àune valeur limite améliore significativement lespropriétés du matériau. Les propriétés optimales duCBPo ont été obtenues à la pression de 7 MPa. Leséchage post-moulage à 100°C, a également amélioréde façon significative les performances du composite.Aussi, par ses nouvelles performances mécaniques, leCBPo se repositionne par rapport à d’autresmatériaux existants permettant ainsi d’en envisagerde nouvelles applications dans la construction.