Machines. Technologies. Materials.
Vol. 13 (2019), Issue 10

Table of Contents

  • MACHINES

    • Finite element simulation on tensile creep behaviour of underground support liner

      pg(s) 417-420

      Polymer-based products are widely used as load-carrying components in different structural applications due to the ease of manufacture, installation, and long lifetime properties. In mining and tunnelling industry, fast-setting, thin polymer-based products are in demand as an underground support liner. Researchers have agreed that the time-dependent material properties of underground support liners have significance for short to long term applications. Although some creep tests were performed in literature, there is no available study on the numerical analysis/simulation of the creep behaviour of underground support liners. In this study, viscoelastic mathematical
      models developed for two different underground support liners were analyzed in ABAQUS finite element numerical modelling software with a developed subroutine. After the implementation, tensile creep test specimens were modelled to verify the new subroutine. There are two main purposes of the simulation of experiments; Firstly, to verify that the subroutine works in accordance with the actual behaviour of the material, secondly, to obtain realistic creep behaviour results for cases where experiments were not performed. As a result, a good  agreement was obtained between the mathematical model predictions and numerical results for different stress levels. The proposed subroutines may create a basement for future numerical studies.

    • Failure characterization of rock anchor bolts by thermal change detection under tensile strength testing

      pg(s) 421-424

      Rock bolts are widely used in tunnels, underground openings, and also rock slopes to provide support and attach blocks to the rock mass in various engineering fields. They have a significant role for the stability of underground structures and natural rock slopes both in the mining and civil engineering industry. The understanding of the rock bolt behavior under stress conditions plays a key role in the long term stability and sustainability of rock slopes, nearby structures, and underground openings. The detection of the failure type and the investigation of failure behavior can be supported by thermal imaging of certain regions on the anchor bolt during tensile testing. In this context, anchor bolt behavior under tensile testing with a force controlled testing environment was analyzed with a LWIR (Longwave Infrared) thermal camera. The heat dissipation during experiments was recorded by a thermal camera together with the force reading from the hydraulic press data logger. As a result of the experiments, it was seen that there is a relation between the temperature change and bolt failure behavior. Therefore, it is expected that this study will provide an opportunity to detect the failure characteristics of the anchor bolts under tensile strength test by the help of infrared thermal camera.

    • Procedure for determination of the calibration curve of the measurement device using the method of linear regression

      pg(s) 425-429

      The result of each measurement consists big or small measurement uncertainty. Many sources of uncertainty, especially in industry measurements, are not well studied and require further researchment. Therefore, it is important to have good knowledge about measurement uncertainty in order to minimize as much as possible.
      The results of performed analyse and the study of the opportunities for application of the method of linear regression for determination the calibration curve of the measurement device are presented in this paper. The researchment refers to the assessment of the measurement uncertainty type A and B, as well as the combined and extended uncertainty of the measurement result.
      By the fulfillment of the assumption for realization of an engineering experiment, with possession of mathematical, technical and practical experience of the operator and the computer supported analytical process, the calibration curve of the measurement device is determined, as well as the extended uncertainty of the measurement result. In this way, a stable measurement process will be achieved, a consistent measurement result, with an increased level of confidence.

    • Simulation tests of the braking process of an agricultural tractor

      pg(s) 430-432

      The agricultural industry is growing very quickly. Large areas of fields make tractors work at higher speeds, with which they also move on public roads. Except acceleration, the agricultural tractor must also be stopped. There are emergency situations on the roads that require sudden braking, and therefore a quick stop of the vehicle. Drum brakes are used in most farm tractors. They contain a friction pair (shoes and drum) which as a result of cooperation changes the kinetic energy of the motion into thermal energy. Unfortunately, this crates huge amount of this energy. This can cause overheating of the friction lining, which can lead to permanent damage. This paper presents the results of simulation tests of the heating process during single emergency braking. It has been shown that in some situations the temperature can reach a higher value than that which is safe for friction material components.

  • TECHNOLOGIES

    • Analysis of the corossion condition of the steel pipe system after long period of exploatation

      pg(s) 433-436

      In this this research work, the results of investigation corrosion condition of the steel pipe system for the heated water transportation and distribution after long years of exploitation are presented. The analysis was performed on the pipe segments after their removing i.e. cutting. Thirty segments were taken for inspection. The outer and inner surface of the pipes was inspected. Plan for inspection was prepared basing of the literature revue and personal experience. All specimens were visually inspected. For the investigations of pitting corrosion measuring of depth of pits was done. Performed investigations confirmed that general corrosion, uniform and no uniform is represented on the pipe from the outer side. From the inner side are presented different types of pitting: narrow, shallow, and elliptical and corrosion under layer. Performed investigation confirmed that the most dangerous for the piping systems is corrosion on the outer sides of the pipes which their perforation. Measurement of the pits deepness showed that pitting corrosion is not so danger because pits deepness is in the range between 0.18-1.24 mm which is negligible compared with the pipes wall thickness.

    • An approach of FRA and its use for UFV supported manufacturing

      pg(s) 437-438

      While many modern industries are tending to use UFV (unmanned flying vehicles) in a near future, there are also many problems of yet unknown procedures to make possible the usage of such UFV. In a current age of aviation development there is an approach of FRA (free routing area) utilization to support growing congestion of many flying vehicles in air space. From our prospective, those manufacturing implementing “Industry 4.0” ideas are expected to use UFV to support supply chains. Hence, both problems and solution approaches to support many aircraft in airspace and to control airspace congestion within safe boundaries can be used also in a local scale of UFV supported manufacturing. This research paper is focused on problems and ability to build routes within FRA and analysis of possible use of known approaches to solve similar problems of modern automated manufacturing.

    • Planning the inflow of products for production levelling

      pg(s) 439-442

      Production levelling, also referred to as production smoothing (jap. Heijunka), is an effective method for reducing unevenness in the production process and maintaining better control over stock levels. It helps keep production at a steady pace and ensure the desired level of flexibility. The authors present a study aimed at developing a method for planning the inflow of products from the production process, intended to be used in the scheduling of levelled production. Focus has been put on finding the right combination of lot size and production interval which, assuming certain input parameters (order size and placement rate, initial stock levels), yields the best outcome in terms of timely/untimely order fulfilment and minimum and maximum stock levels.

    • Selection of production time forecasting method for customized products

      pg(s) 443-446

      The article concerns the problem of selection the most suitable method of calculating manufacturing time of products created in Design To Order approach. Product customization is becoming an increasingly important aspect of many companies. The basic problem of this type of production is the determination of time needed for delivery to the customer. Also estimating the duration of individual production operations can be a significant problem for production planning. Without these values, it is not possible to conduct the production planning process without mistakes and faulties. The use of common worktime calculation methods is often impossible or inadequate from the point of view of the workload involved during production preparation. The article presents the results of practical research in an enterprise, determining the most effective method of calculating production time in Design To Order approach.

    • Numerical simulation prediction and validation two dimensional model weld pipe

      pg(s) 447-450

      This paper deals with Numerical Simulation to analyse the behaviour of residual stresses in welding pipe. This work aims to develop a validation model for the simulation of phase changing after welding in multi-pass welds using a hardness test and compare the results with numerical simulation. The simulation considers the local microstructure properties changes due to the thermal welding cycles. Finally, the challenge of this work is the welding of dissimilar materials, where a calibrated model will be applied and validated to predict the effect of welding residual stresses in welding pipe. A further aim is to develop a new procedure to simulate a typical welded pipe process.

    • Hybrid methods for hardening of superhard vacuum coatings

      pg(s) 451-453

      Physicomechanical and adhesion characteristics, specific surface energy of vacuum coatings formed on high-speed steels of the P6M5 type subjected to processing at cryogenic temperatures are investigated. The structural transformations occurring in vacuum coatings formed on steel substrates with subsequent processing at low temperatures were studied. A change in the tribological characteristics of titanium nitride coatings during subsequent processing in a cryogenic liquid is shown.

  • MATERIALS

    • Analysis of plasticity of quenched tool steel during stress relaxation at elevated temperature

      pg(s) 454-456

      Phase transformations in metals have a major influence on the material behaviour in several common engineering applications. Steels exhibiting enhanced response to transformation-induced plasticity (e. g. high strength TRIP-steels for automotive production) are examples of the important role martensite formation can play. An externally stressed specimen in the process of a phase transformation may show a significant nonlinear behaviour, which is known as transformation plasticity. Even under an externally applied load stress with the corresponding equivalent stress being small in relation to the “normal” yield stress of the material, plastic deformation occurs.
      An aim of a research was to determine relaxation and transformation plasticity properties of alloyed tool steel while is tempered at elevated temperatures and for different tempering duration.

    • ТіН2-based multi-layered titanium matrix composites fabricated using blended elemental powder metallurgy

      pg(s) 457-460

      The high specific strength of Ti-based alloys and composites makes them highly requested materials in various structural applications. However, reinforcement of the alloys with hard particles generally lowers the values of toughness and plasticity of material. A satisfactory combination of plastic and strength can be achieved by formation of layered structures comprising of two and more layers of different materials with different chemical compositions within individual layers. The multi-layer materials allow controlling the mechanical properties of the individual layers by changing microstructure and chemical composition within each layer specifically. In the present study, a cost-efficient process of fabrication of Ti-based multi-layer composites using blended elemental powder metallurgy (BEPM) and TiH2 powder is proposed. Two and three-layered composites based on titanium or Ti-6Al-4V alloy and their metal-matrix composites (MMC) with TiC and TiB were fabricated. Multi-layered samples reinforced by TiC were successfully sintered due to very close shrinkage of adjacent layers. Shrinkage values of layers reinforced by TiB were lower than those for the Ti-alloy, which led to delamination of layered structures, distortion of shape, and cracking. We can control shrinkage in individual layers by means of optimizing the powder size, that allows to obtain multi-layer titanium matrix composites reinforced by TiB with well-balanced mechanical properties.

    • Titanium hydride, metal-matrix composites, titanium carbide, titanium boride, multilayered, microstructure, powders

      pg(s) 461-463

      Titanium diboride reinforced iron matrix composites were produced via powder metallurgy techniques. Iron powder (<10 microns) and titanium diboride powder (<10 microns) were mixed in a ball mill and the powder mixture was cold compacted in a steel die at 550 MPa pressure. Amount of titanium diboride that was added into iron was in 3-10 wt %. Sintering was performed at 1120 oC for 30 minutes in argon atmosphere. Sintered samples were subjected to three-point bending tests, hardness measurements and microstructural examinations.
      It was found that the hardness of the composites increases significantly with the increase in the amount of titanium diboride addition. Hardness of unreinforced iron was 50 Brinell 10 and that of 10 % titanium diboride reinforced composite increased to 100 Brinell 10. On the other hand, there was a decrease in the bending strength and strain of the composites, with increasing titanium diboride addition. Bending strength of unreinforced iron was 850 MPa and that of 10 % titanium diboride reinforced composite decreased to 350 MPa.

    • Preparation and study of corrosion stability of composite coatings on the base of ZrO2 and TiO2

      pg(s) 464-466

      Zirconium dioxide-titanium dioxide coatings were obtained by sol-gel method on stainless steel plates. The samples were treated at three Zirconium dioxide-titanium dioxide coatings were obtained by sol-gel method on stainless steel plates. The samples were treated at three temperatures 300, 400 and 500oC. The morphology and chemical surface composition were examined by Scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), while the phase composition was examined by X-ray diffraction analyses (XRD). The corrosion resistance was evaluated by weight loss measurements in NaCl medium. The coatings are possess relatively smooth surface with some microcracks. After corrosion test the coatings treated at 500oC, keep their surface structure without visible signs of corrosion and thecorrosion tests revealed zero mass loss. The good protective properties of these coatings could be attributed to (i) amorphous structure, leading to deterioration of the ion and electron conduction of the films and (ii) probably increased density after the thermal treatment

    • Crystal structure, magnetic and optical properties of thin films, synthesized on base of SmCo5 and Nd2Fe14B powders

      pg(s) 467-470

      Thin Sm-Co and Nd-Fe-B layers with a thickness of ~ 30 – 850 nm were synthesized by thermal evaporation method using permanent magnets SmCo5 and Nd2Fe14B powders as precursors on glass substrates. The crystal structure was studied by X-ray diffraction in CuKa – radiation at room temperatures. It was shown that thin films are characterized by a highly amorphized crystalline state. It was found that annealing of the films leads to the destruction of the compositions on the glass substrate. In the temperature range of 80 – 1100 K using the ponderomotive method the specific magnetization in the “heating – cooling” mode was measured. Magnetic hysteresis loops were studied in the temperature range of 5 – 300 K. In the wavelength range of 250 – 3000 nm, optical transmission spectra of transparent Sm-Co and Nd-Fe-B films with a thickness of ~ 30 nm were studied.

    • Composite polymeric materials modified by nanodispersion functionalized particles

      pg(s) 471-473

      The paper considers the impact of functionalized nanosized carbon particles on the physicomechanical characteristics of composite materials based on polyamides. The concentration of the modifier varied both in the field of “doping” concentrations and in the field of concentrations used in the industrial production of nanocomposite materials based on polymer matrices. It was found that the use of cryogenic treatment of the initial polyamide leads to an increase in physical and mechanical characteristics. The introduction of nanodispersed particles in the field of “doping” concentrations increases the strength and hardness of the developed compositions based on a polyamide matrix.