Impact Bending Tests Research Articles

Investigation of Dynamic-Cyclic, Dynamic-Impact, and Timber-Construction-Relevant Characteristics of Wood–Textile Composites

Wood–Textile Composites (WTCs) are a new type of composite material based on willow wood strips and polypropylene that combines the properties of classic natural-fiber-reinforced polymers with an innovative textile wood design. While the basic quasi-static properties have already been investigated and described, there is a lack of knowledge about the behavior of the material under dynamic-cyclic and dynamic-impact loading as well as in relation to basic wood construction parameters. The present study is intended to contribute to the later use of the developed material, e.g., in architecture. For this purpose, fatigue tests, dart drop tests (impact and penetration), impact bending tests, and embedment tests were carried out. It was shown that embedding wood fabrics in a thermoplastic matrix leads to a significant increase in resistance to impact loads compared to the neat basic materials. It was also shown that the ratio of the failure stress in the fatigue test to the tensile strength of the WTC corresponds to that of other fiber-reinforced thermoplastics at around 70%. The embedment tests showed that WTC has good values compared to neat wood.

Impact of hybrid nanoparticle reinforcements on Mechanical properties of Epoxy-Polylactic Acid (PLA) Composites

This study examines the influence of graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of SiO2-loaded epoxy-polylactic acid (PLA) composites. Epoxy and PLA were mixed to form the matrix with fillers, including SiO2, GNPs, and MWCNTs. The nanocomposites were prepared with a hybrid filler combination (SiO2/GNPs and SiO2/MWCNTs) with filler concentrations ranging from 0.1 – 0.4 wt. %. The composites were prepared using a combination of bath sonication and hand-casting techniques. They are characterized using tensile, bending impact, and fracture tests. The observed characteristics of GNP/SiO2 and MWCNTs/SiO2-loaded nanocomposites exhibited significant differences. Compared to the unmodified epoxy-PLA composite, incorporating 0.1 wt% of GNP/SiO2 filler improved tensile flexural and impact strength. Conversely, adding 0.4 wt% of MWCNTs/SiO2 filler enhances tensile, flexural, and impact strength. The dispersion mechanism of nanofillers was investigated using Scanning Electron Microscopy (SEM) on fracture surfaces obtained from tensile tests. An ANSYS workbench was used to simulate the impact of filler concentration on nanocomposites' tensile and bending strength, and a numerical analysis was performed.

Analysis of Results of Impact Bending Tests of Base Metal Samples and Welded Joints of Pipes From Low-Carbon Pipe Steels

Analysis of Results of Impact Bending Tests of Base Metal Samples and Welded Joints of Pipes From Low-Carbon Pipe Steels

Determining technological parameters for obtaining ta15 titanium alloy blanks with improved mechanical characteristics using the electron-beam 3D printing method

The object of this study is the process of electron beam 3D printing of articles made of TA15 titanium alloy powder. Peculiarities of the structure and properties formation of alloy blanks, obtained by this method have been described. Influence of process parameters (electron beam power and geometric scanning parameters) on the characteristics of the material were considered. Step of displacement of the beam trajectory changed from 0.1 to 0.25 mm with an interval of 0.05 mm. Specific energy of the electron beam varied from 20 to 70 J/mm3 for every trajectory displacement step. The macrostructure was examined visually while the microstructure was studied by optical microscopy. Mechanical properties were determined by uniaxial tension and impact bending tests. It was established that depending on the 3D printing parameters the macrostructure of most samples is dense but with unfavorable parameters non-fusions or shrinkage porosity defects may form. The microstructure of the dendritic type has an α´+β lamellar-acicular morphology, its dispersity and shape of α´–phase areas vary depending on the process parameters. A scanning step of 0.2 mm and a beam energy of 40 J/mm3 allows obtaining a dispersed microstructure in which there are no non-fusions and shrinkage micropores. The value of the Rm is 27 %, and the R0.2 is 24 % higher than that of the alloy obtained by the conventional technology of electron beam melting. The A5 is 3.2 times higher. However, impact toughness of the sample with dendrite unfavorable orientation to the direction of load applying may be lower compared to conventional technology. The results could be used for devising commercial technology of high strength titanium alloys parts produced by 3D printing

Исследование превращений переохлажденного аустенита при ступенчатой закалке стали 20Cr2Mn2SiNiMo

Currently, step quenching of steels in the temperature range of martensitic transformation, including quenching – partitioning, has found wide application in the automotive industry. Step quenching technology is successfully used to increase a set of properties, which most often include temporary tensile strength and relative elongation. The authors carried out a dilatometric study of the supercooled austenite transformations occurring in the 20Cr2Mn2SiNiMo steel, when implementing various options of step quenching with holding in the martensitic region. It was found that after single-stage quenching, single-stage quenching followed by tempering, and two-stage quenching, primary martensite, isothermal bainite, and secondary martensite are formed in various quantitative ratios. Using X-ray diffraction phase analysis, the amount of residual austenite was determined during step quenching. It has been shown that two-stage quenching makes it possible to stabilise up to 14 % of residual austenite, in the structure of the studied steel, at room temperature. Research has revealed that 20Cr2Mn2SiNiMo steel is characterised by a decrease in the crystal lattice parameter of the residual austenite, with an increase in its content in the steel structure. Uniaxial tensile and impact bending tests were carried out, and the values of the mechanical properties were determined. It has been found that during two-stage quenching, higher strength and elongation values, with lower values of relative contraction and impact strength are achieved compared to oil quenching and low-temperature tempering. The study showed that, with regard to the structural reliability of machine-building parts, step quenching is not the optimal heat treatment mode for the steel under study. The best combination of strength, ductility and impact hardness is achieved after quenching and low-temperature tempering.

Investigation of joints from corrosion-resistant steels obtained by energy-saving rotary friction welding technology

In this article the possibility of application of rotary friction welding for joining parts from stainless steels is evaluated on the example of 10Cr17Ni13Mo2Ti steel. Application of rotary friction welding allows to refuse post-weld heat treatment, which is labor-intensive, energy-consuming and environmentally harmful operation. For this purpose, cylindrical samples of 20 mm in diameter were made from the above steel using friction welding without subsequent heat treatment. The microstructure, microhardness measurement, tensile and impact bending tests were carried out. The microstructure study showed that the weld width across the entire cross-section does not exceed 12 μm. It has an irregular wavy shape with a fine-grained structure. Tensile tests showed that the average value of yield strength of samples with welded joint is 1.6% higher than the same value of samples from the base metal, but the average value of time resistance is lower by 5.6%. Impact bending test results showed that the average impact toughness of welded samples is almost the same as that of base metal samples. According to the results of studies concluded that the weldability of steel 10Cr17Ni13Mo2Ti using friction welding is good, welded joints are obtained high quality.

Changes in structure, hardness and crack resistance of plasma-strengthened steel 65G

The present paper describes the research of structure, hardness and crack resistance indicators before and after plasma treatment of 65G steel of a ploughshare part. As a result of plasma treatment, we obtained the modified layer with increased hardness in the range of 980 – 3558 HV with increase in 3.6 times. Metallographic studies showed that pearlitic-ferritic structure of the original metal transforms into needle martensite with high hardness and strength due to plasma hardening. It is recommended to determine the impact toughness by the Drozdowski method, in which a fatigue crack is pre-created on a special vibrator. Also, before the fatigue crack was grown, lateral V-shaped notches of different depths were made on the sample lateral surface. The relative crack length, λ, varied from 0.27 to 0.65. According to the results of compression tests, it was found that there was a small movement of cracks in the hardened samples in the range from 1.3 to 5.6 mm. The initial unstrengthened samples are in a more brittle state than the quenched ones, and accordingly, significant fracture is observed in the conditions of artificial cracking. The evaluation of 65G steel samples for crack resistance by impact bending tests with subsequent oscillographing showed that plasma hardening inhibits crack growth by increasing impact toughness. Thus, the use of plasma hardening is effective in surface hardening of 65G steel, in particular ploughshares which are constantly exposed to mechanical stresses, friction and wear.

Estimation of the Viscoplastic Properties of 38G2F Steel Using the Results of Tensile and Impact Bending Tests

Estimation of the Viscoplastic Properties of 38G2F Steel Using the Results of Tensile and Impact Bending Tests

The Behaviour of Hybrid Aluminium-Steel Resistance Spot Welded Joints in Case of Dynamic Loading

Hybrid joints between aluminium and steel are used sometimes in case of thin sheets for example for a car body. Resistance welding for this joining challenge is not frequently used, but the resistance welded joints basically have good mechanical properties. During resistance spot joining of these hybrid joints, fusion between the two materials cannot occur, but with the right technological parameters an intermetallic compound (IMC) appears in the joint line. The properties of the IMC have significant effect to the joint properties, because the researchers basically investigate this. The original static mechanical tests can show good, comparable results for the joint properties. If we see the dynamic tests basically really difficult to find results in case of spot welding of steels and joining of hybrid aluminium – steel joints. The aim of this paper to show the dynamic properties of these hybrid joints. During our investigation DP600 dual-phase steel was used as the steel part because this grade is frequently used in a car chassis. For the aluminium part, two types of aluminium were applied: non-heat treatable 5754-H22 alloy, and heat-treatable 6082-T6 alloy. The different aluminium alloys have different properties, so different technological parameter combinations were used. To test the resistance of hybrid joints against dynamic loading, instrumented impact tests were performed. This special impact test is considered as an impact-bending test, because the load is perpendicular to the welded point joint. Force – time diagrams of impact tests were shown too in this paper. The intermetallic compound is necessary for joint, but it is very brittle with very big hardness, but in case of dynamic testing this hardness has no significant effect, so these specimens show good result in case of dynamic loading. The two different aluminium – steel joints show different resistance against dynamic loading, and the fracture modes were different too.

The Effects of Electrochemical Hydrogen Charging on Charpy Impact Toughness and Dry Sliding Tribological Behavior of AISI 316H Stainless Steel

In this work, solution-annealed AISI 316H grade austenitic stainless steel was studied in terms of investigating the electrolytic hydrogen charging effects on the resulting Charpy impact toughness and dry sliding tribological behavior. Conventional Charpy impact bending tests were employed to study the mechanical response of the investigated material to dynamic loading conditions, whereas dry linear sliding tribological tests were used to study material friction and wear behavior. The obtained mechanical and tribological properties were correlated with corresponding fracture and tribological mechanisms, which were determined from morphological observations of fracture surfaces and tribological tracks. The applied testing procedures were individually carried out for the non-hydrogenated, hydrogen-charged, and dehydrogenated material conditions. The observed changes in individual properties due to applied hydrogen charging were rather small, which indicated the good resistance of solution-annealed AISI 316H steel against material degradation in currently used electrolytic hydrogenation conditions.

Microstructure and Impact Toughness of Acicular Ferrite in Low Alloy Steel Weld Joints from Results of Multiple Impact Bending Tests

Microstructure and Impact Toughness of Acicular Ferrite in Low Alloy Steel Weld Joints from Results of Multiple Impact Bending Tests

Impact of barium and strontium on calcium recovery level in ladle treatment of steel by complex modifiers with alkaline-earth metals

Increasingly rigid requirements in terms of the steel products quality are forcing the technical experts of metallurgical production to look for new solutions to stabilize the steel quality. Much attention is paid to ladle treatment technologies and selection well-minded composition of modifiers, which makes it possible to reduce steel contamination by non-metallic inclusions. To solve this problem, complex modifiers containing both calcium and other alkaline-earth metals (barium and strontium) are used. The paper presents the results of the pilot scale tests of steel ladle treatment by complex modifiers with alkaline-earth metals (Si, Ca, Ba) in steel production with increased requirements to non-metallic inclusions in conditions of electric furnace steelmaking shop of JSC “Ural Steel”. During experimental work it was possible to reduce the maximum contamination score profile rolled steel from pipe steel grades for brittle silicates (GOST 1778) from 4.0 to 1.5 – 2.5, for non-deforming silicates from 4.0 to 3.0 – 3.5. The substitution of SK40 grade silicocalcium for experimental modifiers led to an improvement in the strength properties of rolled products, both in tensile tests and in impact bending tests at low temperatures. The indicated impact was observed in all variants of consumption the experimental master alloys. It is noted that with an increasing in the consumption of master alloys, the positive effect on the steel mechanical properties enhanced. It was established that the replacement of silicocalcium with experimental variants of master alloys made it possible to increase the calcium recovery by an average of 1.6 times when using Si – Ca – Ba, and by an average of 2.4 times when using Si – Ca – Ba – Sr. The use of complex modifiers made it possible to obtain the target value of residual calcium in the sample at significantly lower calcium consumption.

Low-Temperature Deformation and Fracture of Cr-Mn-N Stainless Steel: Tensile and Impact Bending Tests

The paper presents the results of tensile and impact bending tests of 17%Cr-19%Mn-0.53%N high-nitrogen austenitic stainless steel in temperatures ranging from −196 to 20 °C. The steel microstructure and fracture surfaces were investigated using transmission and scanning electron microscopes, as well as X-ray diffraction analysis. The steel experiences a ductile-to-brittle transition (DBT); however, it possessed high tensile and impact strength characteristics, as well as the ductile fracture behavior at temperatures down to −114 °C. The correspondence between γ–ε microstructure and fracture surface morphologies was revealed after the tensile test at the temperature of −196 °C. In this case, the transgranular brittle and layered fracture surface was induced by ε-martensite formation. Under the impact bending test at −196 °C, the brittle intergranular fracture occurred at the elastic deflection stage without significant plastic strains, which preceded a failure due to the high internal stresses localized at the boundaries of the austenite grains. The stresses were induced by: (i) segregation of nitrogen atoms at the grain boundaries and in the near-boundary regions, (ii) quenching stresses, and (iii) reducing fcc lattice volume with the test temperature decrease and incorporation of nitrogen atoms into fcc austenite lattice. Anisotropy of residual stresses was revealed. This was manifested in the localization of elastic deformations of the fcc lattice and, consequently, the stress localization in <100>-oriented grains; this is suggested to be the reason of brittle cleavage fracture.

Оценка вязкопластических свойств стали 38Г2Ф по результатам испытаний на растяжение и ударный изгиб

Оценка вязкопластических свойств стали 38Г2Ф по результатам испытаний на растяжение и ударный изгиб

Fatigue behaviour of NiCr-type of austenitic nodular cast iron

High resistance to high and low temperatures, resistance to corrosion when exposed to salt water and alkaline media, resistance to wear, high elongation, and paramagnetism are all characteristics of austenitic nodular cast iron. However, less research has been done on the fatigue resistance of austenitic nodular cast iron. Therefore, the objective of this study is to determine the fatigue characteristics of austenitic nodular cast iron and compare them to those of different types of nodular cast iron. The nodular cast iron used in the research (EN-GJSA-XNiCr20-2) was alloyed with 20% nickel and 2% chromium to create an austenitic matrix. Light metallographic microscopy was used to examine the microstructure. A tensile test, an impact bending test, and a Brinell hardness test were used to examine the mechanical properties of the material. Fatigue tests were done under sinusoidal cyclic push-pull loads at room temperature to obtain the Wöhler curve and determine the fatigue limit. The results of these tests were compared with the fatigue characteristics of nodular cast irons with different matrixes, namely ferrite-pearlitic and pearlite-ferritic nodular cast irons.

LABORATORY AND OPERATING TESTING OF HIGH-ALLOY STEEL PIPES MADE BY THE LATEST TECHNOLOGIES

The purpose of the research: evaluation of the quality and durability for pipes made of high-alloyed austenitic and ferritic-austenitic steels, which are manufactured at PJSC "CENTRAVIS PRODUCTION UKRAINE" using the latest technologies, by conducting complex laboratory studies and long-term operational tests at chemical industry enterprises. Materials and methods: the research materials were experimental pipes made of high-alloyed austenitic and ferritic-austenitic chromium-nickel-molybdenum steels of the new generation, manufactured using the latest technologies. The microstructure of the pipes was investigated by metallography and electron microscopy using developed and improved methods. Corrosive researches in laboratory terms included a test on firmness against the local types of corrosion inherent in high-alloy steels: intergranular corrosion (IGC), pitting corrosion (PC), corrosion cracking (CC) and sulfide stress corrosion cracking (SSCC). The mechanical properties of the pipes were determined by tensile and impact bending tests. Long-term operational tests of pipes were carried out in conditions of industrial production at chemical industry enterprises in apparatus for the urea and caustic soda production. Research results: A high content of special low-energy grain boundaries in the theory of coincident nodes’ lattices (SG CSL) was established in the structure of pipes manufactured according to the latest technologies (≥ 75 %); high resistance of pipes against various types of the most dangerous local corrosion compared to existing analogues, a high level of mechanical properties, as well as high corrosion resistance during long-term operational tests in environments at chemical industry enterprises. The implementation of the obtained results will contribute to increasing the efficiency of production and operation for highly alloyed steel pipes in demand on the world market and increasing the competitiveness of domestically produced pipes on the European and world markets.

APPLICATION OF MODELS OF THE STRUCTURE OF SEPARATION SURFACES IN STEELS WHEN OBTAINING PRODUCTS WITH A GIVEN LIFE CYCLE

Background. The development of digital mechanical engineering requires the development and use of interdisciplinary concepts and models of the behavior of heterogeneous polycrystalline materials under the influence of technological and operational loads. In this regard, the development and use of approaches to modeling and analysis of the mechanical behavior of the boundary zones of separation of products, taking into account their energy, becomes important. The development of such approaches makes it possible to solve an actual scientific and technical problem – optimization of the modes of technological processing of products with a given life cycle. Objective. The use of system models of the structure of steels for the development of computational schemes and methods of managing the structural-energy state of the separation surfaces of structural components when obtaining products with increased reliability parameters, taking into account the conditions of their operation. Methods. The analysis of the structure was carried out using the concept of invariant modeling, the results of metallographic and factographic studies, electron microscopy. The assessment of the structural and energetic state of grain separation surfaces after ionplasma etching of the samples was carried out, wear and impact bending tests were carried out, and system computer simulation of the properties of polycrystalline systems was carried out using the FEniCS open finite element analysis package in Python. Results. When applying the energy description of continuous non-local environments, it was established that depending on the angles between the boundaries at the joints of the grains, the structural and energetic state of this region and its ability to form microdefects change. At angles between 140‒180°, zones are formed with a high capacity for the formation of intergranular damage and destruction under load. It is shown that the intensity of wear and intergranular fracture upon impact increases depending on the number of triple joints, in which the boundaries differ significantly in terms of energy level. Steel 40X (5135 Steel) is more sensitive to the formation of triple junctions with a high energy gradient during heat treatment than steels containing nickel, molybdenum and silicon. Conclusions. On the basis of hierarchical modeling of the structure of polycrystals, new approaches are proposed and an algorithm is created to determine the relationships between the structure of the separation surfaces of steels and their operational reliability. Diffuse damage is formed on the separation surfaces between the triple junctions of grains with a high energy gradient. Reducing the share of triple joints, which differ significantly in terms of energy when designing the technological regimes of the quenching and tempering processes, made it possible to increase the wear resistance of improved steels by 48‒53 %.

Instrumentation of a Pendulum Impact Testing Machine for Impact Bending Tests

Instrumentation of a Pendulum Impact Testing Machine for Impact Bending Tests

Specifics of diagnostics and investigation of material properties in pipes with planar defects

The paper presents findings of a study on planar defects formed on the inner surface of gas pipeline metal in the operation process. The diagnostic indicators of a defective section were determined and analyzed using the intelligent pigging data. A broad range of research was carried out, including visual and measuring control of the object, step-by-step ultrasonic thickness measurement, chemical analysis, optical and electron microscopy, microhardness measurement of defective and defect-free areas, static tensile and impact bending tests. The structure and morphology of defective and defect-free areas were considered. It was determined that the cause of the defects is contamination of the source material with gas pores and fluorspar residues. The defects of planar nature are formed during rolling and can be characterized as metal delamination. The maximum detected thickness of the inclusions was 1.0 mm, however, the main part was rolled to 10.0 μm. The key feature of defects is their location on various levels throughout the wall cross-sections, ranging from one to four detected layers or groups of rolled discontinuities. It is shown that such defects lead to a change in the strength properties of defective area, uneven distribution of loads and reduction in safety margin of the object.

Evaluation of failure mechanisms of metals obtained by additive electric arc growth using neural network classification

Structural alloys obtained by additive electric arc growth are tested. Impact bending tests followed by fractographic studies showed that the fracture mechanism of 09Г2С steel completely changes from ductile to brittle at temperatures below –60 °C, for 07Х25Н13 steel and АМг5 alloy, the fracture mechanism does not change up to temperatures of –150 °C. To assess the nature of the destruction of the materials, it is proposed to use fractal analysis and an artificial neural network. Keywords: 3D printing, electric arc welding, cold resistance, impact toughness, fracture mechanisms, fractal analysis, artificial neural network.uru.40@mail.ru