Rolled Material Research Articles

FEATURES OF THE CALCULATION OF ROLLS ON THE FATIGUE STRENGTH

On modern rolling mills, manufacturers have the possibility to use a wide range of materials with technologically determined properties, which allows for effective use of rolls and improvement of technical and economic indicators of production processes. Reasonable choice of materials and properties of rolls is impossible without reliable methods of calculating the strength and predicting the service life of the rolls. In particular, increasing of the reliability of methods for calculating the fatigue strength of rolls is an urgent task, both for scientists and for technologists and specialists of rolling mills.
 The purpose of the work is to study the features of fatigue calculation of rolls based on the predicted number of load cycles. The work solves the problem of assessing the possibility of applying a known method of determining the predicted number of load cycles and studying the features of such a method for rollsofrolling mills.
 The method of calculation based on the approximation of Woehler curves for the roll material by Beskin's power dependence within the zone of high cycle fatigue, which was determined by the number of cycles from 1·103 to 5·106, was considered. It has been proven that such a technique can be used for rolls into account the identified features. The main features of the calculation of rolls for fatigue strength include: a symmetrical cycle of changes in bending stresses and a pulsating cycle of changes in torsional stresses; mandatory consideration of working conditions due to the modified endurance limit of the material; compliance with the condition that the working stresses exceed the modified endurance limit, but are less than the admissible stresses for the roll material; taking into account the stress concentration depending on the shape of the grooves that form the passes. Consider influence the effect of stress concentration in the grooves of the rolls requires clarification based on empirical data of a certain rolling mill.
 The application of the fatigue calculation method for rolls, with considerthe identified features, will allow to increase the accuracy of determining the predicted terms of operation of the rolls and determining their consumption.

2次均質化法を用いた多結晶材料の圧縮変形における寸法依存性と加工条件の関係評価

In a hot steel rolling process, the rolling force and the strain distribution in a rolled material is strongly affected by the friction coefficient between the work roll and the rolled material and the rolling shape factor which is the ratio of the contact length between the work roll and the material to the material thickness. In this respect, many numerical attempts have been made to reveal their relationship. These simulations often suppose the homogeneity of the material because of simplicity. However, the recent researchers have suggested that the heterogeneity in microstructure can cause size effect on deformation behavior of polycrystalline material. In order to clarify the size effect in the rolling process, this study investigates the size effect on the deformation force and the strain distribution in the plane strain compression which is simple and similar to the flat rolling in effects of the friction coefficient and the shape factor, using the second-order homogenization-based finite element (2nd HMFE) simulations. Simulations are performed by two-dimensional 2nd HMFE with different friction coefficients, shape factors, work hardening parameters and size ratios between micro and macrostructures, which are related to strain heterogeneity in a deformed material. As a result, in case of the small friction coefficient, relatively uniform deformation tends to occur in the material, which results in small effects of the size ratio on deformation behavior. In contrast, in case of the large friction coefficient, size effects on the compression force and the strain distribution appears to be large when the shape factor of a deformed material approaches 1. It is considered to be because high strain gradient tends to reduce the plastic work in the microstructure and a deformation band in which the strain gradient is higher is formed in the material in such a case.

Persepsi Siswa Kelas XI IPA 3 Dan XI IPS 2 terhadap Pembelajaran Senam Lantai Materi Roll Depan di SMANegeri 9 Samarinda Tahun Pembelajaran 2017/2018

The purpose of this study was to find out how big the perception of class XI IPA 3 and XI IPS 2 SMA Negeri 9 Samarinda students towards the front roll material floor gymnastics learning. The subjects in this study were students of class XI IPA 3 and XI IPS 2 with 70 students of which 40 were male and 30 female. The method used in this research is descriptive quantitative using a questionnaire instrument. Data analysis was carried out using the percentage formula. The data obtained is data in the form of numbers calculated, then processed by adding up, compared with the number of respondents and the percentage obtained. The results showed that the description of the perceptions of students in class XI IPA 3 and XI IPS 2 towards learning floor exercise on the front roll material, the perception of factors / experiences in the very good category, as many as 67 respondents (95.71%) and as many as 3 respondents (4.29%) in the category good. Perceptions of student needs in the very good category as many as 57 respondents (81.43%) of which 11 respondents (15.71%) were in the good category, 1 respondent (1.43%) was in the fairly good category and 1 respondent ( 1.43%) is in the less category. Perceptions of fun/hobby factors in very good category 27 respondents (38.57%) 23 respondents (32.86%) were in good category, 16 respondents (22.85%) were in, 3 respondents (4.29%) ) is in the poor category and 1 respondent (1.43%) is in the very poor category. Perceptions of habits / patterns of daily living are in very good category as many as 38 respondents (54.28%) 23 respondents (32.86%) are in good category and 9 respondents (12.86%) are in quite good category .

Why rolled Mg-Al-Ca-Mn alloys are less responsive to aging as compared to the extruded

Dilute Mg-Al-Ca-Mn alloys exhibit excellent strength-ductility combinations in the peak-aged condition due to ordered, single atomic layer Guinier-Preston (GP) zones. The present work explains why rolled sheet material is softer and less responsive to aging, as compared to extruded. Using crystal-plasticity modeling, it is shown that the initial texture of the rolled material permits the soft modes, basal slip and twinning, to accommodate more of the strain during in-plane tension, and they are less responsive to hardening by the finely dispersed GP zones. Even with the same number density of GP zones, the extruded material is stronger in tension along the extrusion axis due to an initial texture which forces higher relative activity of prismatic slip, a mode previously shown to be strongly affected by the GP zones. The present work reemphasizes the significant role of the initial texture in determining the strength and anisotropy of non-cubic metals and alloys.

Analysis of roller compaction pressure distribution in automated dry fibre placement

Automated Dry Fibre Placement (ADFP) is a version of Automated Fibre Placement (AFP) where prepreg tapes are substituted with dry fibre tapes. In this process, a uniform compaction pressure applied by a compaction roller is required to manufacture preforms with consistent quality. In this paper, a finite element model is developed to analyse the roller-applied pressure on the fibrous reinforcement bed. The model has been validated by using a pressure sensitive film. The influence of roller material, tool curvature and substrate thickness on the pressure distribution are investigated. Increasing tool curvature leads to a decrease in compaction pressure uniformity using the same compaction force. Force input target bounds for different rollers on tools with different curvatures are determined using the model. It is found that softer rollers show large force control window and suitability for tools with higher curvature. Thick substrates exhibit large deformation which could increase complexity for force control strategies.

Enhancing Mechanical Properties of Poly(p-phenylene sulfide) by Biaxial Deformation Using Cross-Rolling and Subsequent Annealing

The effect of thermal treatment on the mechanical performance of biaxially oriented poly(p-phenylene sulfide) by cold roll milling was studied. It was found that the ductility of the cross-rolled material could be further enhanced by annealing at temperatures above Tg and the yield strength could be enhanced by annealing at temperatures below Tg with a partial loss in ductility. Two-dimensional wide-angle X-ray diffraction patterns suggested a reduced crystallinity in the rolled material and showed that the crystal structure of the unrolled material could be partially recovered by annealing above Tg; however, scattering patterns adjacent to the crystalline reflections persisted with heat treatment. Modulated differential scanning calorimetry (MDSC) and broadband dielectric spectroscopy indicated that cross-rolling altered the kinetics of the cold-crystallization process. MDSC and dynamic mechanical analysis measured a reduction in Tg suggesting enhanced molecular mobility as an outcome of cross-rolling. After annealing at temperatures well beyond Tg, a large reduction in elongation to failure was observed, and the material could not cold draw. These results suggest that a two-stage process involving plastic deformation by roll milling followed by annealing treatment may be used to commercially produce high toughness and yield strength sheet products from commercially available resins.

Influence of microstructure on degradation of cast graphitic high-speed steel

Work rolls used in hot rolling of steel suffer severe wear caused by combinations of adhesion, abrasion, rolling contact fatigue, thermal fatigue, and tribo-chemical corrosive attack. Depending on the specific wear mechanisms, damage of these rolls may include loss of material, surface, and subsurface cracking, as well as impairment of the surface finish. In this work, wear tests were performed using a custom-designed roll test rig which simulates the contact conditions between the work roll, the back-up roll and the hot-rolled steel. To simulate typical conditions occurring in a hot rolling mill, different contact pressures and rolling temperatures were considered. Wear and damage mechanisms were analyzed by optical microscopy and scanning electron microscopy (SEM). A systematic approach was used for correlating wear and microstructure of the roll materials. Therefore, graphitic high-speed steels (G-HSS) with different fractions and types of carbides were investigated. MC and M2C/M6C were identified to influence mainly the wear behavior of G-HSS. Increasing the fraction of these carbides reduced the wear rate but increased the surface roughness. The optimum balance between carbide types, graphite content and metal matrix has been identified as mandatory for achieving high wear performance of work roll materials.

Tensile test of a specimen from different-thickness sheet material

A technique for tensile testing of a sample cut from a sheet blank of different thicknesses is proposed. Gage interference sheet blanks are obtained by rolling or welding sheet materials of different thicknesses and are used in the manufacture of various shells by metal forming in the automotive, electrical, and aerospace industries. Currently existing test methods provide for the tension of samples having the same thickness and width. Therefore, an urgent task is to develop a technique for tensile testing of a sample of different thicknesses. The proposed technique uses a sample cut from a sheet material of different thicknesses joined by welding, having different widths, in which the cross-sectional area along the estimated length is constant, which creates the same conditions for its deformation throughout the volume. In contrast to existing tensile test methods, in which the averaged values of mechanical and plastic properties are determined, the proposed method obtains mechanical and plastic properties in several cross sections of the sample located along the estimated length. The sample is subjected to tension with a uniform rate of deformation until the onset of the neck formation with the recording of the load-displacement diagram. By changing the dimensions of the cross sections when using the load-displacement diagram, at the considered moment of tension, the intensity of stresses and strains, parameters of hardening curves, anisotropy coefficients, and the non-uniformity of plastic deformation in each cross section of the sample are determined. For example, tests of a different thickness sample made of NHX260YD steel with a weld in the transverse direction are given.

Solid-state processing of surplus aluminium alloy powders through a combination of field-assisted sintering technology and hot rolling

ABSTRACT Metal additive manufacturing techniques typically operate using powders with limited particle size ranges, but atomisation processes produce significant amounts of particles outside these ranges, resulting in an accumulation of out-of-size specification metal powders without a clear use case. Field-assisted sintering technology (FAST) can provide an alternative, solid-state processing route to consolidate these powders into billets for subsequent processing, or directly into near-net shape components. In this study, surplus powders of A20X, an aerospace approved aluminium alloy developed by Aluminium Materials Technologies (ECKART GmbH), were processed using FAST and subsequently hot rolled to produce sheet material. Tensile properties were similar to hot rolled conventional cast material and comparable to additively manufactured product. This indicates that FAST is an effective option for converting surplus metal powders into useful products, while improving sustainability in the additive supply chain.

Characterization of Plastic Deformation in CuZr Metallic Glasses Subjected to the Rolling Process

Using the rolling process, it is possible to induce multiple shear bands in the microstructure of metallic glasses (MGs) and improve the overall plasticity in the subsequent mechanical loadings. Hence, it is crucial to understand the mechanism of shear banding and plastic deformation under the rolling process. In this work, molecular dynamics (MD) simulation was applied to evaluate the formation and generation of shear bands in a CuZr MG under cold- and hot-rolling processes. Based on the results, it is found that the shear bands are formed with secondary branches in the cold rolling, while the shear events are scattered in the bulk of material in the hot rolling. Considering Voronoi analysis, it is revealed that the hot rolling is accompanied by the recovery of crystalline-like clusters provided that rolling process continues for subsequent passes. On the other hand, the cold-rolled sample shows a stable behavior in the evolution of crystalline-like clusters; however, the population of main icosahedral polyhedrons decreases in the system.

COMPARATIVE ANALYSIS OF WELD MICROSTRUCTURE IN TI-6AL-4V SAMPLES PRODUCED BY ROLLING AND WIRE-FEED ELECTRON BEAM ADDITIVE MANUFACTURING

The microstructure and phase composition of electron beam welded Ti-6Al-4V titanium alloy were studied by optical and scanning electron microscopy, backscattered electron diffraction, and X-ray diffraction analysis. Deep-penetration electron beam welds were made in single pass on rectangular Ti-6Al-4V samples obtained by rolling and wire-feed electron beam additive manufacturing. It was found that the weld width in 3D printed Ti-6Al-4V samples is greater than in the rolled material. The influence of the gas vapor channel on the size, shape and structure of primary β-grains formed in the fusion zone was shown. The variation of the penetration coefficient, volume fraction of the residual β phase, and residual stresses along the weld length was studied for Ti-6Al-4V samples obtained by both rolling and 3D printing.

ПРОБЛЕМИ ТА ПЕРСПЕКТИВИ РОЗВИТКУ ПІДПРИЄМСТВ ЗАЛІЗНИЧНОГО ТРАНСПОРТУ

The article proves that today, in conditions of drastic changes in macro- and micro-environments, Ukrainian railway transport enterprises are not always able to adequately and flexibly respond to these changes, as a result of which the industry's potential opportunities for obtaining economic benefits can turn into a source of problems. Studies have shown that currently the characteristic features of the modern state of railway transport enterprises are a high level of wear and tear of the rolling stock and material and technical base, a critical level of the financial state of the industry, as well as open questions regarding restructuring, the development of public-private partnerships, attracting investments, and technical innovations. and technological modernization in the industry. This situation arose as a result of: almost complete lack of state support, state funding, which does not allow covering the needs for maintenance and development of transport infrastructure; lack of own means of railways; lack of external funding sources; administrative restrictions on the increase of railway transport tariffs, which does not allow to accumulate funds for capital investments; imperfections of the legislative and regulatory framework. To date, the railways of Ukraine have a sufficiently high level of efficiency, as evidenced by the main qualitative indicators that characterize the operation of railway transport: average daily locomotive productivity, average daily wagon productivity and freight wagon turnover. It has been proven that without the implementation of decisive measures in the direction of improving management activities, the railway transport of Ukraine in the coming years may turn into the main restraining factor of the rise and structural restructuring of the economy, ensuring the country's security and defense capability, improving conditions and raising the standard of living of the population. Ensuring the effective development of railway transport should be based on a fundamentally new management approach, which would include the formation of innovative potential as a priority, as well as the constant and continuous improvement of the competence of railway enterprises.

Meningkatkan Kreativitas Anak Melalui Bahan Loose Part pada Kelompok B TK IT Almawaddah

This study aims to describe the increase in children's creativity through loose part materials in group B TK IT Almawaddah. The form of this research is classroom action research using descriptive methods. The research subjects were children aged 5-6 years, totaling 5 people. Data collection is done through observation and interviews. The results showed that children's creativity increased after being given action through activities using loose part materials which gave children the freedom to explore, choose suitable materials and colors, free to cut, tear, cut and roll materials according to their wishes and use the tools provided in accordance with child's needs.

Development of front and back rolling mobile learning media for class x students of SMAN 1 Pamekasan

Many students do not understand the gymnastic movements being taught and become bored with the movement, as well as the learning method. This study aims to produce a learning media device in physical education, sports and health in the form of mobile learning floor exercise with front roll and back roll material for student’s class X of SMAN 1 Pamekasan so that it can be a teaching material. In this study, the Research and Development (R&D) from Lee and Owens was. So that only 5 steps are in accordance with the conditions in the field. (1) needs analysis, (2) product design, (3) development related to the material to be developed (4) application/implementation, (5) product evaluation by experts and product trials. Results of product development data obtained the first result (91.3%) with 32 students and the second group (87.4%) with 115 students. From the results of these data, it can be concluded that the criteria for learning media products for floor exercise materials based on mobile learning have very valid criteria and are suitable for use in learning activities in schools.

ANALYSIS OF THE MECHANICAL PROPERTIES OF LONG PRODUCT ROLLING MILL ROLLS

Rolls of longproduct rolling mills, as an expendable working tool of the rolling technological operation, make up a significant share of redistribution costs and significantly affect the economic efficiency of the manufacturing process. The importance of rolls is manifested in the organization of their production at specialized enterprises, the presence of rolling menage in the workshops of metallurgical enterprises, the development and introduction of new rolling rolls materials. Therefore, the tasks of analyzing the available roll materials and their properties, choosing the optimal set of properties for the conditions of a certain state become quite actual.
 The purpose of the work is to review rolled materials and analyze the properties of rolls used in modern long-product mills. Such an analysis was performed for steel and cast-iron rolls, the use of which is most common on mills for the production of simple profiles in the form of bars and rods.
 Based on the analysis of the latest research and publications, the stages of the development of rolled materials in retrospect, the main indicators of the mechanical, technological and operational properties of the rolls have been determined. The main types of cast iron and steel rolling materials offered by leading manufacturers of rolling rolls are also established. For these groups of roll materials, an analysis of their mechanical properties, such as hardness, tensile strength, and bending strength, was performed.
 Based on the results of the analysis, a significant improvement in the mechanical and operational properties of modern rolled materials was noted. This is achieved due to alloying, improvement of their manufacturing technologies, specialized types of heat treatment aimed at forming a certain structure and properties. Conditional blurring of boundaries between cast iron and steel rolls is also established. For example, iron rolls with a ferrite structure and spheroidal graphite and graphitized steel rolls are used, which provide approximately the same mechanical strength, gripping ability and wear resistance.
 Modern rolled materials are characterized by the expansion of controlled property indicators. This applies both to the components of the chemical composition and to indicators of mechanical properties. In particular, the leading manufacturers of rolled rolls include the bending strength limit, which is 1.5 to 2 times higher than the strength limit from tensile tests, among the mandatory indicators.
 In the calculations of the rolls, the fulfillment of their strength conditions should be checked by the allowable stresses determined beyond the bending strength limit, as an indicator of the properties, which to a greater extent corresponds to the load conditions of the rolls.
 An objective assessment of the performance of the rolls according to the strength conditions can be obtained only when determining the allowable stresses based on the actual values of the properties provided by the manufacturer of the rolls, and not according to the range of values recommended in the literature.
 The results of the conducted analysis can be used for the justified selection of rolling materials, improving the control of their properties, obtaining objective assessments of their performance, increasing the efficiency of the rolling farm and technical and economic indicators of production processes.

Thermal behavior in rolling bearing applications: Comparison of steel and ceramic materials applied to tapered rollers

Due to their properties, ceramic materials can improve both reliability and efficiency of rolling bearings. Most of the studies have investigated the power losses and temperatures of ball bearings with balls made of silicon nitride (Si3N4) versus steel ones. This study thus focuses on tapered rollers. Thanks to experimental and numerical means, the thermal behavior of tapered roller bearings is investigated for both steel and silicon nitride rollers. Various operating conditions (rotational speed, oil flow rate and oil temperature) are tested to allow the comparison of the behavior of both bearing set-ups (full-steel and hybrid). A thermal model is developed according to the thermal network method and is validated thanks to experimental results. It is then used to analyze behaviors observed during experiments, related to thermal exchanges and power losses. The effect of changing the mechanical and thermal properties of the roller material is investigated.

Influencing factors and conditions of increasing N in molten steel

N content has the important influence on the performance of rolled material and needs to be keep a watchful eye. However, the current N content control course is relatively simple and needs to be further studied. Starting from the full steel smelting course, through the analysis of the influence factors of increasing N in liquid steel and conditions, found that the main node control enhance of N in liquid steel and operating points, summed up the appropriate bottom blowing N gas pressure and flow rate, improve the control level of bottom blowing N and N content, the ability of N steel smelting in batches, ensure the quality of liquid steel meets the demand of high standard special steel, at the same time achieving production cost reduction.

Evaluation of elastic-plastic deformation in HSS work roll under coupling of residual stress thermal stress and contact stress during hot rolling

Fatigue damage such as crack and spalling on the work roll surface in hot rolling is caused by comprehensive action of residual stress, thermal stress and contact stress. In this work, a HSS work roll was studied based on the actual hot rolling condition, and high temperature performances of the work roll materials are considered. Finite element method was used to obtain the residual stress distribution of the work roll after quenching and tempering. Then, the coupling mechanism of residual stress, thermal stress and contact stress of the work roll in the bite region are analyzed by a transient thermomechanical model. The results showed that, the maximum equivalent strain and equivalent plastic strain appear at the exit of the bite region. And residual stress and thermal stress account for about 90% of the coupling stress. The accumulation of plastic deformation only occurs in the initial rolling, and the initial temperature influences the plastic deformation accumulation. Furthermore, abnormal rolling often leads to large plastic deformation on the roll surface.

Modifikasi Matras Lantai Dalam Pembelajaran Senam Lantai Materi Roll Depan Dan Roll Belakang Bagi Siswa Sma Negeri 3 Semarang Tahun 2022

Facts on the ground show that at SMA Negeri 3 Semarang, the learning activities of floor gymnastics for the front roll and back roll materials are not much in demand by students. The cause of the low interest of students is because they feel ashamed and afraid, think it is too difficult to do it, and cannot balance the body. It is dominated by female students and students who have fat bodies. From the facts in the field, the researchers created a tilted mattress tool to help students perform front roll and back roll motion skills.
 This research is a development research, which uses the Research and Development method. The product development procedures are: (1) information gathering, (2) initial planning, (3) developing the initial product, (4) expert validation, (5) initial revision, (6) small-scale test (50 students), (7 ) product revision, (8) large scale test (80 students), (9) final product revision, (10) final results. This research produces a product, namely a tilting mattress tool.
 Data was collected using questionnaires obtained from expert evaluations and student questionnaires. Based on the results of the development, small-scale trials obtained a percentage of 79.34% (Good), the results of large-scale trials were 78.22% (Good), and for expert validation tests obtained a percentage of 86.66% (Good).
 The conclusion of this study is based on the assessment criteria that have been determined, the product of this tilting mattress aid is included in the good criteria for use. Suggestions for schools, teachers, and students can participate and contribute in the use of modified floor mats in learning floor exercise with front roll and back roll materials.

Effect of substructural inhomogeneity on the anisotropy of physical and mechanical properties of textured materials

Today, anisotropy of the physical and mechanical properties of textured materials is mainly calculated based on average properties of a single crystal and information about the volume percent of grains that have different orientations, which can be determined with the help of distribution function. It is a fact that, in addition to the crystallographic texture, substructural inhomogeneity develops in rolled materials, which manifests itself as a difference in the distortion of the crystalline lattice (hardening) and elastic microstrains in grains belonging to different texture components. Substructural characterization is based on the X-ray method of Generalized Direct Pole Figures, which implies that a full profile of X-ray reflections is registered for different positions of the specimen, i.e. as a direct pole figure is being built. As a result, one can obtain the FWHMs of X-ray lines and elastic microstrains distributed on the stereographic projection. It means that a textured polycrystalline material that has undergone thermo-mechanical treatme nt is characterized with a certain spectrum of structural states and the presence of residual elastic microstrains. Therefore, the degree of macroscopic anisotropy of the product properties is defined both by the predominant grain orientation in the polycrystal and by the parameters of substructural inhomogeneity of grains belonging to different texture components. In spite of the fact that the elastic properties of an individual crystallite do not change and the tensile and compressive elastic microdeformations are balanced in the studied volume of the material, the elasticity of the whole system, i.e. of a polycrystal, changes due to interacting grains and the elastic energy stored in them. The authors propose a method for calculating elastic moduli and thermal expansion coefficients while accounting for the substructural inhomogeneity of the material by minimizing the elastic energy of the textured material. The efficiency of this method is demonstrated on specimens of a semi-finished channel pipe made of Zr – 2.5% Nb alloy.This research was funded by the Ministry of Science and Higher Education of the Russian Federation; Agreement No. 075-15-2021-1352.