Impact Bending Research Articles

A Comparative Study on the Temperature Effect of Solid Birch Wood and Solid Beech Wood under Impact Loading.

In order to use wood for structural and load-bearing purposes in mechanical engineering, basic information on the impact behaviour of the material over a wide temperature range is needed. Diffuse porous hardwoods such as solid birch wood (Betula pendula) and solid beech wood (Fagus sylvatica) are particularly suited for the production of engineered wood products (EWPs) such as laminated veneer lumber (LVL) or plywood due to their processability in a veneer peeling process. In the frame of this study, solid birch wood and solid beech wood samples (300 × 20 × 20 mm3) were characterised by means of an impact pendulum test setup (working capacity of 150 J) at five temperature levels, ranging from −30 °C to +90 °C. The pendulum hammer (mass = 15 kg) was equipped with an acceleration sensor in order to obtain the acceleration pulse and deceleration force besides the impact bending energy. In both solid birch wood and solid beech wood, the deceleration forces were highest at temperatures at and below zero. While the average impact bending energy for solid birch wood remained almost constant over the whole considered temperature range, it was far less stable and prone to higher scattering for solid beech wood.

Beech wood thermally modified in the melt of polyethylene glycol

Various techniques of wood thermal modification in air, liquids, or melts at temperatures above 160 °C improve its resistance to biological damage and water. In this experiment, the European beech (Fagus sylvatica L.) wood was held for 1 to 4 hours in the melt of polyethylene glycol 6000 (PEG 6000) and during a given time either heated at 100 °C or thermally modified at 190 or 210 °C. Its decay resistance improved – maximally at using the more intense modification mode 210 °C/4h – to Poria placenta by 60.3% and to Trametes versicolor by 62.8%. The soaking and volume swelling in water of the PEG-thermally treated beech wood usually was significantly reduced, after 336 h maximally by 60% and 34.6%, respectively. The presence of PEG during the thermal modification processes caused darkening of beech wood – a decoratively interesting and more pronounced effect than what occurs in traditional air-thermal modifications – at which the Eab* was also great from 13.1 to 52.6. However, since the mechanical properties of the PEG-thermally modified beech wood worsened – impact bending strength maximally by 34% and Brinell hardness maximally by 43.3% – its application for structural elements would be limited.

Structure heterogeneity and mechanical properties studied in thickness up to 100 mm of low-alloyed shipbuilding steel sheets with a yield strength not less than 420 MPa

This paper presents a study of changes in the structure and properties in thickness of rolled sheets up to 100 mm of low-alloyed shipbuilding steel with a yield point not less than 420 MPa. The fracture surface of samples after impact bending tests at low temperatures was investigated. It was found that the combination of the parameters of lath morphology bainite (fraction, areas average size and length) and the size of structural elements at given tolerance angles of 5 and 15° (indicating the presence or absence of a developed subgrain structure of deformation origin) determine the level of impact work at low temperatures testing.

Physical and foundry propertiesof Cu-Sn-Al system alloys

Tin-aluminum bronze containing Sn - up to 6.73% and Al - up to 7.53% (by weight) physical and casting properties determination. Methodology. Melting has been carried out in graphitecrucible in induction furnace under charcoal layer. Alloys liquidus and solidus temperatures have been investigated by thermography results of solidifying melt. Free (С) and absolutely difficult (АЗ) linear shrinkage values and alloy transition temperature from plastic to elastic state during cooling in mold have been studied by conventional methods. Bronzes fluidity has been estimated by the spiral sample filled channel length according to GOST 16438. Bronze BrO3A3 tendency to burn and to hot and cold cracks formation has been evaluated by samples surface visual examination results. Cast bronze specific density has been determined by calculation. Studied alloys mechanical properties have been calculated based on corresponding samples tests results at their impact bending at room temperature in accordance with actual standards. Alloys chemical composition control has been carried out on precision analyzer EXPERT 4L on specimens cut from club-shaped samples. Microstructural studies have been performed on metallographic microscopic samples prepared by standard methods on optical microscope Neophot-21. Approximation reliability value and corresponding dependences have been built using EXEL computer program. Results.According to qualitative and quantitative indicators and system Cu-Sn-Al bronzes with Sn content up to 6.73% and Al content up to 7.53% physical and foundry properties assessments, it has been determined that among possible tin and aluminum content in Cu-Sn- Al the most promising is bronze with 3...4% (by weight) of these alloying components each. Originality.For the first time number of physical and foundry properties of Cu-Sn-Al system bronze (with Sn content up to 6.73% and Al up to 7.53%) have been determined. It has been first established that such bronzes linear shrinkage, transition temperature from plastic to elastic state during cooling after solidifying and impact bending value at normal temperature depend on their structure, i.e. phase composition determined by its alloying elements content in bronze. Practical value.According to studies of physical and foundry properties results, bronze BrO3A3 has been recommended to be used as casting material

Determination of Fracture Energy Characteristics and Their Anisotropy for 15Kh2NMFA Steel in Impact Bending Tests

Determination of Fracture Energy Characteristics and Their Anisotropy for 15Kh2NMFA Steel in Impact Bending Tests

Modeling of radial variations of wood properties in naturally regenerated trees of Betula platyphylla grown in Selenge, Mongolia

Wood properties, such as annual ring width, wood fiber length, vessel element length, basic density, air-dry density, dynamic Young’s modulus, modulus of elasticity (MOE), modulus of rupture (MOR), absorbed energy in impact bending, compressive strength parallel to grain, and shearing strength, were investigated for wood from 10 naturally regenerated trees of Betula platyphylla Sukaczev in Mandal, Selenge, Mongolia. Mixed-effects models were used to evaluate the radial variations in the wood properties. The mean values of wood properties obtained in the present study were in almost the same range, with a few exceptions, as those reported by other researchers for other Betula species. The radial variations of wood properties in B. platyphylla were well-fitted to a nonlinear mixed-effects model (logarithmic formula); all examined wood properties increased from the pith and then became constant toward the bark side. The wood properties significantly differed between the core and outer wood. Basic density, air-dry density, and dynamic Young’s modulus were significantly correlated with MOE, MOR, and compressive strength. It is concluded that when the wood of B. platyphylla is utilized as raw materials for solid wood products, the differences between the core wood and outer wood should be considered. In addition, the selection of wood with higher strength properties can be achieved using the wood density and dynamic Young’s modulus as indicators.

Low-speed bending impact behaviour of adhesively bonded dissimilar single-lap joints

This study investigates the low-speed bending impact behaviour of adhesively bonded dissimilar single-lap joints and the effects of both strength and plastic deformation capability of adherend material on adhesive failure. Dissimilar adhesive single-lap joint specimens, such as Al 2024-T3 (top adherend)-Al 5754-0 (bottom) and Al 5754-0 (top)-Al 2024-T3 (bottom), were tested at two impact energy levels (3 and 11 J) for two overlap lengths (25 and 40 mm). The progressive failure analysis of the adhesive layer was also conducted by the non-linear explicit finite element method. The adhesive layer was modelled with a 3D cohesive layer along with the upper and lower adhesive interfaces and a non-linear continuum adhesive region between two cohesive layers. The continuum adhesive region had elasto-plastic adhesive properties whilst the cohesive layers obeyed 3D cohesive rules. The experimental and predicted contact force-time, contact force-displacement diagrams, axial separation lengths of the failed adhesive region, permanent deflection of the bonded region, fracture surfaces were in good agreement. The strength and plastic deformation capability of adherend materials and impact energy levels affected the progressive adhesive failure behaviour. The proposed finite element model was successful reasonably in predicting the initiation and propagation of the adhesive failure.

SMOOTH AND REDUCED OIL AND GAS PIPES WITH INCREASED CORROSION RESISTANCE

Formulation of the problem. Corrosion of pipes used in the oil and gas industry leads to significant economic losses, therefore, increasing their corrosion resistance and durability is an urgent task. Purpose: generalization of results of developments of technologies of manufacturing and research of qualitative characteristics of oil and gas pipelines (smooth) and pump-compressor (threaded) pipes of the increased and high corrosion resistance and giving recommendations on their application in oil and gas industry in environments of various corrosion aggressiveness. Methodology. The microstructure of tubular steels and protective coatings was studied by light metallography and electron microscopy. Complex corrosion studies included laboratory tests of samples in model chloride and hydrogen sulfide-containing media, the resistance to sulfide corrosion cracking under stress (SCCS) and hydrogen cracking (НС) according to the methods of NACE TM 0177 and NACE TM 0284 as well as operational tests at the oil fields of Ukraine. Mechanical properties for stretching and impact bending of samples by standard methods. Results. The results of the development of production technologies and the study of the qualitative characteristics of oil and gas pipelines and tubing with increased and high corrosion resistance in aggressive oil and gas production environments are summarized. The influence of the chemical composition of steels and protective coatings, as well as pipe manufacturing technologies on their microstructure, corrosion resistance in various media, and mechanical properties is shown. Scientific novelty. For the first time, the presence of special low-energy boundaries in the ferrite of low-alloy ferrite-pearlite and high-alloy ferritic-austenitic steels was established, their number and energy level were estimated. The high operational reliability of threaded pipes with a protective coating is substantiated. Practical value. The results of the work and recommendations for the rational use of oil and gas pipes with increased corrosion resistance can be used to increase the economic efficiency of production in the oil and gas industry.

Features of diffusion processes in the preparation of prepregs by the method of layered application of components

The modern production of products made of composite materials based on thermosetting binders is mainly based on the use of pre – impregnated reinforcing technical threads-prepregs. The binder used for such semi-finished products must meet two important technological requirements: have a low reactivity (high viability) when stored in the temperature range from -5 to +25 ° C and the ability to adjust the curing time at the molding temperatures of the product. To eliminate the disadvantages of the traditional method of obtaining polymer composite materials, to improve their strength characteristics and reduce the cost of the resulting reinforced composites, it is proposed to use the method of layered application of components. The essence of the method consists in layer-by-layer impregnation of the fibrous filler with a binder solution, and then a developed curing system consisting of an amine hardener that prevents the interaction of the hardener with the resin under storage conditions and protective polymer emulsions. The binder-filler system is activated only at an elevated temperature under curing conditions. It is established that the optimal parameters for processing by direct pressing of the pre-pegs components obtained by the method of layer deposition are a pressure of 15 MPa and a temperature of160-170 ?С with a pressure exposure of 15 minutes. If you get products by winding, then for such products, heat treatment for 6 hours at a temperature of 120 ?С is optimal. In the conditions of forming products, that is, at an elevated temperature and at an increased pressure, the mutual diffusion of components occurs due to the movement of oncoming flows. Oligomeric molecules from the resin volume diffuse from the inner layer to the outer one, and the components of the curing system meet them from the outer layer to the inner one. The method of layered application of components makes it possible to create a macroheterogenic system of interpenetrating polymer meshes in the contact area of sequentially applied layers. The result of the research is an increase in the shelf life, the viability of prepregs (up to 10 days) and an improvement in the complex of physical and mechanical properties of composites: the destructive stress during static bending increases to 60 %, during dynamic bending (impact) - up to 50 %. The use of carboxymethylcellulose as a protective polymer provides higher indicators of the studied properties than when using butadiene styrene latex as a protective polymer..

Performance improvement of radiata pine wood by combining impregnation of furfuryl alcohol resin and densification for making fretboard materials

The fast-growing plantation radiata pine wood has undesirable intrinsic properties, which cannot meet the physical and mechanical performance requirements of string instrument fretboard materials. In this study, the synergistic modification technology of FA impregnation treatment and densification treatment was proposed to improve the density, dimensional stability, and mechanical properties. In addition, its surface color of radiata pine wood was deepened to imitate precious tropical hardwood (e.g., ebony, Indian rosewood, and African blackwood) that are commonly used in the fretboards of string instruments. This technology combined the characteristics of the wood densification and FA impregnation treatment, that is, the densification treatment can improve the mechanical strength of low-quality wood and FA can fix the deformation of the densified wood, preventing treated wood from spring back. The performance differences between the fretboard wood and FA-densified-wood with compression rates (CRs) of 17 %, 33 %, and 50 % were analyzed, and the optimal CR was determined. The fretboard wood has high density (> 800 kg/m3), dimensionally stable, and red brown or jet-black surface color. The modulus of rupture (MOR), modulus of elasticity (MOE), compression strength (CS), Brinell hardness (BH), and impact bending strength (IBS) of the fretboard wood are higher than 140.0 MPa, 13.0 GPa, 120 MPa, 7.9 N/m2, and 17 kJ/m2, respectively. The fretboard wood also has good abrasion resistance. The FA-modified wood with a CR of 50 % had a high density (> 1000 kg/m3), superior dimensional stability, excellent mechanical properties, and its surface color was jet black, which was the same as those of the fretboard wood. The FA-modified wood with a CR of 50 % met the performance requirements of wood for fretboards, and has the potential to replace the fretboard wood for string instrument fretboard manufacturing. It breaks through the restriction that fast-growing plantation wood cannot be used for musical instruments, alleviating the shortage of the resources of commonly used tropical hardwood for fretboards and providing new insights for the high-value utilization of plantation radiata pine wood.

Effect of Hostile Solutions on the Residual Fatigue Life of Kevlar/Epoxy Composites after Impact Loading.

Due to the enormous benefits inherent to composite materials, they have been widely used in the most diverse fields of engineering. Therefore, it is not surprising that in many of these applications they can be exposed to hostile environments, which can affect the mechanical performance of such materials. Therefore, the main goal of this work was to study the effect of immersion into different hostile solutions on the impact strength and, subsequently, to evaluate the residual fatigue life. For this purpose, the specimens were initially immersed into solutions of hydrochloric acid (HCl), sodium hydroxide (NaOH), sulphuric acid (H2SO4), diesel, distilled water, and seawater. Subsequently, the specimens were subjected to impact loads with an energy of 12 J and, finally, subjected to fatigue loads to assess the residual fatigue life. Seawater and NaOH solution provided the lowest impact strength. This was confirmed by the lower energy restored and impact bending stiffness (IBS), a parameter that allows evaluating the damage resistance of a composite. In terms of restored energy, for example, the seawater promoted a decrease around 30.4% in relation to the value obtained with non-immersed samples, while this value was 27.6% for the alkaline solution (NaOH). In terms of IBS, the lowest values were also obtained with these solutions (437.4 and 444.9 N/mm, respectively). Finally, the lowest residual fatigue life was also observed for these two solutions, and it was noticed that there was a direct relationship between the IBS and the residual fatigue life.

Furfural-based resin for modifying birch wood properties

Furfural (F) cannot be easily polymerized like furfuryl alcohol, but it is an aldehyde that can react with urea (U) to make a polymeric network. The possibility of preparing F/U polymer along with an acidic catalyzer (maleic anhydride; M) was evaluated as a means to improve some selected properties of birch (Betula pendula) wood. The F+U/M resin was introduced into the wood with a double treatment technology. The first step involved dilution of F in water and methanol, and the second step was immersion in a U/M aqueous solution. The color of treated wood was darkened after resin curing from brown to a spectrum of black depending on the amount of loaded resin. The 60 to 80% of materials were converted to a non-leachable polymer based on the different formulations. The water absorption and volumetric swelling of the treated samples decreased with an increase in weight percent gain (WPG). The analysis of mechanical strength showed that treatment with F + U/M reduced to some extent the hardness and the impact bending of wood, while modulus of rupture, modulus of elasticity, and compression parallel to the grain with WPG were increased. The exposure of the samples to the accelerated weathering showed noticeable changes in color and roughness.

Gas Atomization of X6CrNiTi18-10 Stainless Steel Powder for Selective Laser Melting Technology

Powders of X6CrNiTi18-10 stainless steel were fabricated from original workpieces of different grade by gas atomization method. It was found that it is necessary to use argon as a gas for gas atomization of X6CrNiTi18-10 steel, since the use of nitrogen leads to the formation of its compounds, namely, titanium nitride. It is shown that all used workpieces – electric arc, electric slag and vacuum arc refinement – allow one to obtain powders suitable for further utilization in selective laser melting technology of 3D printing. The main physicochemical and technological properties of the obtained powders have been investigated. Changes in the chemical composition and quality of the powders are not significant within the X6CrNiTi18-10 grade. The 0...20 μm fraction of powders does not have fluidity, and thus cannot be used for additive technologies. The fraction 20...63 μm have suitable rheological properties for additive technologies and may be used in selective laser melting (SLM) process. The yield of target fraction 20 ... 63 microns was ≈45%. The fraction 63...120 μm may be used for the direct metal deposition (DMD) additive technology. Considering the economic aspect of the technology, it is preferable to use original workpieces of X6CrNiTi18-10 steel produced by electric arc or electroslag process, since the market price of vacuum arc steel is significantly higher. The fraction of ferrite phase in the powder increases with a decrease of particle size of the resulting powder and is lower comparing to the original workpiece. In the future, for a detailed study of the technological properties, it is planned to grow samples from each type of the obtained powders on installation for selective laser melting and direct laser deposition to determine the physical and mechanical properties of fabricated samples (tensile and impact bending tests) and carry out metallographic studies.

Evaluation of Micropiles With Different Configuration Settings for Landslide Stabilization Based on Large-Scale Experimental Testing

In this study, a large-scale model test was performed to investigate the effect of the single-row and double-row micropiles on the landside stabilization. For two different testing configuration settings, the bending moment along the micropiles, failure mode, and force condition were captured and compared. It is found that the landslide thrust on piles was distributed in a triangular shape. The piles in the front row carried greater pressure than the piles in the rear row. The resistance of the sliding body behind the pile was distributed in a parabolic shape, and mainly concentrated on the middle of the pile. The piles were destroyed due to the combined shearing and bending impact applied near the slipping surface. The boundary of the failure zone was from the position of two times the pile diameter under the slipping surface to the position of two and a half times the pile diameter above the slipping surface. Under the action of the landslide, each row of piles deformed at the same time. The capability of landslide stabilization for double-row piles was better than that of a single-row pile. The sections of the pile above slide surface were mainly subjected to negative bending moments and were distributed mainly within the pile length range of one-third of the anti-sliding section above the sliding surface. The pile body of the embedded section located in the range of ten times the pile diameter below the sliding surface was subjected to a positive bending moment.

Cold Resistance and Mechanical Properties of 07Cr25Ni13 (ER309LSI) Stainless Steel Obtained by 3D Printing by Electric Arc Surfacing on a CNC Machine

The article discusses the mechanical properties and cold resistance of austenitic stainless steel (analogue 07Cr25Ni13) obtained by 3D printing by electric arc surfacing from ER309LSI welding wire on a CNC machine. These properties were investigated in the process of physical tests of samples cut along and across the layers of 3D printing for tensile and impact bending. Using optical microscopy, the microstructures of steel sections were obtained for various temperature conditions of interlayer exposure, as well as the values ​​of the recommended microhardness. In the process of 3D printing, an intelligent system for monitoring the dynamic stability of the electric arc was applied, which made it possible to guarantee the stability of the structure and properties of the obtained samples throughout the entire process of surfacing. Additional heat treatment of experimental samples (austenitization) was considered as a way to improve mechanical properties and cold resistance. It has been established that the dynamic stability of an electric arc, modes of interlayer temperature holding and subsequent heat treatment largely determine the mechanical properties and cold resistance of ER309LSI steel obtained by 3D printing by electric arc surfacing.

Influence of silicone oil thermal modification on mechanical properties of Masson pine wood

In this study, the effect of silicone oil thermal modification at different treatment temperatures (150 oC, 180 oC and 210 oC for 2 h and 4 h.) on the mechanical properties of masson pine (Pinus massoniana L.) wood was investigated. The density, modulus of elasticity (MOE), modulus of rupture (MOR), impact bending, compressive strength, and hardness of silicone oil thermal treated samples were evaluated and compared with those of untreated samples. Results showed the mechanical properties of masson pine wood reduces after silicone oil thermal modification. The higher the modification temperature, the lower the mechanical properties of Mason pine wood. At 210 oC for 4 h, mechanical properties of the modified samples were two times lower than the mechanical properties of the untreated. Higher modification temperature and longer treatment time contributed to lower mechanical properties

Correlation between grain boundary strength determined by impact test of miniature specimen and stress corrosion cracking resistance of irradiated austenitic steels used for the internals of WWER-type and PWR-type nuclear reactors

Austenitic chromium-nickel 321, 316 and 304 stainless steels used for internals of PWR (pressurized water reactor) and WWER (water-water energetic reactor) reactors were irradiated to 4–125 dpa in different neutron energy spectra and investigated by impact bending tests of miniature specimens. Relying on these tests, the effects of neutron dose and neutron energy spectrum on the intergranular fracture energy determining grain boundary strength have been analyzed.Two neutron spectra were considered. One spectrum is typical of the core of light water moderated reactors PWR and WWER, another spectrum is typical of the core of fast neutron reactors (FR).A correlation between resistance to stress corrosion cracking (SCC) and grain boundary strength in irradiated chromium-nickel 321, 316 and 304 stainless steels has been found.

INVESTIGATION OF IMPURITIES IN BRONZE BrO3A3 INFLUENCE ON ITS MECHANICAL PROPERTIES

. Problem statement. To investigate the influence of main alloying components Sn, Al on 3… 4% each without taking into account impurities influence, as well as silicon, iron, zinc and lead in Cu-Sn-Al system bronze on its mechanical properties. Purpose. To establish permissible concentrations of silicon, iron, zinc and lead impurities in Cu-Sn-Al system bronze at tin and aluminum content each of 3… 4%. M aterial and methods. Alloys for investigation have been prepared by melting of technical purity primary charge materials in crucib le induction furnace using graphite crucible and charcoal as coating material. Studied alloys mechanical properties have been calculated based on experimental samples tests results during their static expansion and impact bending at room temperature in accordance with actual standards. Microstructural studies have been performed on metallographic specimens prepared by standard methods on optical microscope Neophot-21. Alloys chemical composition control has been carried out using precision analyzer EXPERT 4L on samples cut from club-shaped samples. Estimation of each impurity influence level on mechanical properties has been estimated according to regression coefficients due to system of corresponding linear equations solving by G. Cramer method. Results and discussion. According to research results, in this work permissible concentrations impurities of silicon, iron, zinc and lead in Cu-Sn-Al system bronze have been detected at optimal content of tin and aluminum 3… 4% each. Conclusions. For the first time, alloying components (Sn, Al on 3… 4% each) optimal amount influence without impurities effect, as well as impurities of silicon, iron, zinc and lead in bronze BrO3A3 on its mechanical properties has been established. Practical impl ementation of received regularities for bronze BrO3A3 preparation is the key to obtaining castings with given level of properties.

Fixed and Variable Temperature Super-Solidus Liquid Phase Sintering of High Chromium Cast Iron With 25 Wt.%CR and Its Microstructure

A variable temperature super-solidus liquid phase sintering (SLPS) technique is employed in fabrication of high chromium cast iron (HCCI) with 25wt.%Cr to extend its sintering temperature window. Its microstructure evolution, mechanical properties, and abrasive wear behavior are investigated systemically. The results indicate that the variable temperature SLPS can obtain samples with full density plus fine and uniformly distributed carbide particles, and its carbide volume fraction is increased by 4~5% in comparison with the fixed temperature SLPSed one. Meanwhile, its bending strength and impact toughness can be raised by 8.0% and 16.7%, respectively. Finally, the sintering temperature window for variable temperature SLPS of HCCI is extended by 12 °C, reaching 27 °C.

Dynamic strength properties and structural integrity of wood modified with cyclic N-methylol and N-methyl compounds

Abstract Cyclic N-methylol compounds have been used for cell wall impregnation modifications of wood. Besides an improved decay resistance and dimensional stability, the modifications resulted in a decrease of wood’s dynamic strength properties. However, the mechanisms behind a significant loss in dynamic strength are not fully understood yet. In this study, wood blocks were treated with the N-methylol compounds 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and methylated DMDHEU (mDMDHEU) and the N-methyl compound 1,3-dimethyl-4,5-dihydroxy-ethyleneurea (DMeDHEU). In order to study the factors that control the changes of wood performance under dynamic loads, single (impact bending strength, IBS) and multiple dynamic impact (resistance to impact milling, RIM) tests were applied. It became evident, that reductions in IBS and RIM increased with increasing solid content, formaldehyde content and catalyst concentration of the impregnation solutions, but were not affected by a cold-water leaching. Differences in structural integrity of wood modified with N-methylol and N-methyl compounds were more pronounced than those of IBS. Therefore, RIM appeared more sensitive to changes on cellular level, as a higher degree of co-condensation of the N-methylol compounds with cell wall polymers was expected in comparison with the N-methyl compound.