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The paper is focused on the determination of the course and change of the surface quality parameters obtained by the laser engraving of the material known under commercial name polymethyl methacrylate. The paper aims to find mathematical relations based on regression analysis for amplitudes parameters Ra and Rz. For this purpose, a sample of variable technology parameters will be machined followed by the surface measuring and evaluation using the Talysurf CLI 500 3D Surface Scanner. Thus the data obtained will be subjected to the detailed statistical analysis to check homoscedasticity, the presence of outliers, and multidimensional normality testing. © 2018 Trans Tech Publications, Switzerland.

The paper is focused on the determination of the course and change of the surface quality parameters obtained by the laser engraving of the material known under commercial name polymethyl methacrylate. The paper aims to find mathematical relations based on regression analysis for amplitudes parameters Ra and Rz. For this purpose, a sample of variable technology parameters will be machined followed by the surface measuring and evaluation using the Talysurf CLI 500 3D Surface Scanner. Thus the data obtained will be subjected to the detailed statistical analysis to check homoscedasticity, the presence of outliers, and multidimensional normality testing. © 2018 Trans Tech Publications, Switzerland.

Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.

Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.

Load-carrying systems often suffer from unexpected disruptions which can cause damages or system breakdowns if they were neglected during product development. In this context, unexpected disruptions summarize unpredictable load conditions, external disturbances or failures of system components and can be comprehended as uncertainties caused by nescience. While robust systems can cope with stochastic uncertainties, uncertainties caused by nescience can be controlled only by resilient load-carrying systems. This paper gives an overview of the characteristics of resilience as well as the time-dependent resilient behaviour of subsystems. Based on this, the adaptivity of subsystems is classified and can be distinguished between autonomous and externally induced adaption and the temporal horizon of adaption. The classification of adaptivity is explained using a simple example of a joint brake application.

Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.

Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.

Load-carrying systems often suffer from unexpected disruptions which can cause damages or system breakdowns if they were neglected during product development. In this context, unexpected disruptions summarize unpredictable load conditions, external disturbances or failures of system components and can be comprehended as uncertainties caused by nescience. While robust systems can cope with stochastic uncertainties, uncertainties caused by nescience can be controlled only by resilient load-carrying systems. This paper gives an overview of the characteristics of resilience as well as the time-dependent resilient behaviour of subsystems. Based on this, the adaptivity of subsystems is classified and can be distinguished between autonomous and externally induced adaption and the temporal horizon of adaption. The classification of adaptivity is explained using a simple example of a joint brake application.

Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.

Load-carrying systems often suffer from unexpected disruptions which can cause damages or system breakdowns if they were neglected during product development. In this context, unexpected disruptions summarize unpredictable load conditions, external disturbances or failures of system components and can be comprehended as uncertainties caused by nescience. While robust systems can cope with stochastic uncertainties, uncertainties caused by nescience can be controlled only by resilient load-carrying systems. This paper gives an overview of the characteristics of resilience as well as the time-dependent resilient behaviour of subsystems. Based on this, the adaptivity of subsystems is classified and can be distinguished between autonomous and externally induced adaption and the temporal horizon of adaption. The classification of adaptivity is explained using a simple example of a joint brake application.

Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.

Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.

Load-carrying systems often suffer from unexpected disruptions which can cause damages or system breakdowns if they were neglected during product development. In this context, unexpected disruptions summarize unpredictable load conditions, external disturbances or failures of system components and can be comprehended as uncertainties caused by nescience. While robust systems can cope with stochastic uncertainties, uncertainties caused by nescience can be controlled only by resilient load-carrying systems. This paper gives an overview of the characteristics of resilience as well as the time-dependent resilient behaviour of subsystems. Based on this, the adaptivity of subsystems is classified and can be distinguished between autonomous and externally induced adaption and the temporal horizon of adaption. The classification of adaptivity is explained using a simple example of a joint brake application.

Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.

Load-carrying systems often suffer from unexpected disruptions which can cause damages or system breakdowns if they were neglected during product development. In this context, unexpected disruptions summarize unpredictable load conditions, external disturbances or failures of system components and can be comprehended as uncertainties caused by nescience. While robust systems can cope with stochastic uncertainties, uncertainties caused by nescience can be controlled only by resilient load-carrying systems. This paper gives an overview of the characteristics of resilience as well as the time-dependent resilient behaviour of subsystems. Based on this, the adaptivity of subsystems is classified and can be distinguished between autonomous and externally induced adaption and the temporal horizon of adaption. The classification of adaptivity is explained using a simple example of a joint brake application.

In this paper it was performed curve negotiation analysis of three axle bogie of locomotive type JŽ 461. This locomotive has large distance between first and middle i.e. middle and last axle, which leads to increased lateral forces during curve negotiation. Final result might be widening of track gauge in curves with small radius. This paper points that Infrastructure Manager must take into account vehicle performances and type of track when defines track gauge in curves.

In the present paper, the Preisach model of hysteresis is extended to structural analysis of trusses damaged under cyclic loading in plastic range. Parameters for the Preisach model of cyclic plasticity are obtained from uniaxial loading experiment. Damage, as a consequence of micro cracks appearance due to alternating loading in plastic domain, is modeled using brittle elements according to Preisach procedure. Results of this research are compared with the already existing in the literature. In the paper examples of trusses under various cyclic loadings are presented.

In this paper it was performed curve negotiation analysis of three axle bogie of locomotive type JŽ 461. This locomotive has large distance between first and middle i.e. middle and last axle, which leads to increased lateral forces during curve negotiation. Final result might be widening of track gauge in curves with small radius. This paper points that Infrastructure Manager must take into account vehicle performances and type of track when defines track gauge in curves.

In the present paper, the Preisach model of hysteresis is extended to structural analysis of trusses damaged under cyclic loading in plastic range. Parameters for the Preisach model of cyclic plasticity are obtained from uniaxial loading experiment. Damage, as a consequence of micro cracks appearance due to alternating loading in plastic domain, is modeled using brittle elements according to Preisach procedure. Results of this research are compared with the already existing in the literature. In the paper examples of trusses under various cyclic loadings are presented.

Rice production in Brazil in 2010 was approximately 12,2 million tons, and to reach that amount several planting techniques were used with different strains of rice in different rice-growing areas. Since Rice Husk Ash (RHA) is the pozzolan of vegetable origin most studied by researchers working in the area of pozzolanic materials, the present paper evaluates the influence that the form of planting, the climate, the soil, the strain of rice and the origin/amount of nitrogen-based fertilizers used in rice cultivation has on the chemical composition and crystallographic properties of RHA. The results obtained in this paper, confirm the importance of carrying out routine chemical analysis and X-Ray diffraction to maintain the quality control of the CCAs produced, because in situations of large-scale production, husks of different origins may be used.

Rice production in Brazil in 2010 was approximately 12,2 million tons, and to reach that amount several planting techniques were used with different strains of rice in different rice-growing areas. Since Rice Husk Ash (RHA) is the pozzolan of vegetable origin most studied by researchers working in the area of pozzolanic materials, the present paper evaluates the influence that the form of planting, the climate, the soil, the strain of rice and the origin/amount of nitrogen-based fertilizers used in rice cultivation has on the chemical composition and crystallographic properties of RHA. The results obtained in this paper, confirm the importance of carrying out routine chemical analysis and X-Ray diffraction to maintain the quality control of the CCAs produced, because in situations of large-scale production, husks of different origins may be used.

This paper reports the experimental work on the characterization of quantum dot-in-well (DWELL) solar cell grown by metal-organic chemical vapor deposition (MOCVD) without employing any post-growing optimization like antireflection coating and metal grid. The structure of the 10-layer DWELL solar cells is studied by cross-sectional transmission electron microscopy (TEM). Room temperature photoluminescence (PL) spectra show strong quantization at 1178.5 nm with a linewidth of 79.9 nm. External quantum efficiency spectra show enhancement in the spectral response of the photocurrent with respect to the reference quantum dot cell (without DWELL structure). In spite of the reduction in conversion efficiency due to poor collection of current in external circuit compared to reference quantum dot cell it show the improvement in open circuit voltage.

The steels fracture toughness was measured at two different temperature T= - 60°C and T = -90°C, at v=0.02 mm/min and v=0.5 mm/min. The following steels: CrMoV, 20MnMoNi55, A533B and A508 were tested with three different sizes of CT specimens 50 and 100 and 200. Those steels are weldable, although the authors investigated the fracture behaviour of base material. In order to satisfy statistical analyses, a large number of specimens were tested. Fracture behaviour has turned out to be typical, S-shaped curve for transitional fracture at low temperatures. Apart from the other variables, specimen’s width significantly affects measured toughness. Smaller specimens, CT50, might be considered of upper bound reliability while the CT200 specimens were shown to be the most conservative. In this way it has been shown that wider specimens are more reliable in a fracture assessment of the examined steels. In this paper, the fracture probabilities of specimens in function of fracture toughness were determined as well, and it could be concluded that the widest specimens are the most likely to be broken for the same values of the fracture toughness.

This paper studies different modelling methodologies for a calculation of the three point bend test. Test samples are composed of a rubber matrix and either steel or textile cords reinforcement. Prior to the bending tests, all of the used materials including the matrix and the reinforcement were measured to find out their mechanical properties. Rubber materials were described using hyperelastic models. FEM software MSC Marc/Mentat is employed as a calculation tool and its various functionalities are utilized for a description of the test composite models. The main observed outcome is a dependence of the vertical force causing the test sample deformation on the amount of the deformation. Calculated results are compared to each other and to measurements. Then, all the modelling techniques are evaluated. © 2018 Trans Tech Publications, Switzerland.

Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behaviour. This paper studies the effect of different doses of ionizing beta radiation on the micro-mechanical properties of commercially available polyamide. The measured results indicate, that electron beam irradiation is very effective tool for improvement of surface properties of PA6. In terms of micro-mechanical properties, the values of micro-hardness of surface layer increased by 24% at radiation dose of 132 kGy, stiffness of surface micro layer by 26% (132 kGy) as a result of different loads (0.5N and 2N). Improvement of micro-mechanical properties of radiated polyamide has a great significance also for industry. The modified polyamide shifts to the group of materials that have considerably better properties. Its micro-mechanical properties make polyamide ideal for a wide application in areas where higher resistance to wear, creep are required. Commonly manufactured PA6 can hardly fulfil these criteria. © 2018 Trans Tech Publications, Switzerland.

The aim of this paper is to investigate the behavior of the recycled polymer containing the filler. The recycled polymer under investigation is polypropylene with a glass fiber filler. During grinding of plastic waste particles are formed which have a different size, shape and surface, from larger pieces to dust particles. Several recycled mixtures were made, all from original material. Samples with different particle size of recycled material were subsequently tested by mechanical testing. Included tests were Charpy impact test and Shore hardness test. Testing was conducted at different temperatures; ambient 23 °C and increased temperatures 60 ° and 100 °C. The results show a very large effect on Charpy properties and a lesser influence on the hardness of these mixtures. Mixture of smallest dust particles indicates larges change of measured properties. © 2018 Trans Tech Publications, Switzerland.

The presented paper deals with the problems associated with laser cutting of metal materials. Specifically, it solves the question of structural changes that occur as a result of the transfer of heat to the material. Experimental machining of selected technical materials was carried out, and on the basis of the hardness measurement near the cutting point, the heat-affected zone was evaluated after passing the laser beam. To confirm the detection of the affected zone width the models of transient temperature field were arranged, to represent the distribution of temperature in the vicinity of the cutting edge. © 2018 Trans Tech Publications, Switzerland.

The aim of this paper is to investigate the behavior of the recycled polymer containing the filler. The recycled polymer under investigation is polypropylene with a glass fiber filler. During grinding of plastic waste particles are formed which have a different size, shape and surface, from larger pieces to dust particles. Several recycled mixtures were made, all from original material. Samples with different particle size of recycled material were subsequently tested by mechanical testing. Included tests were Charpy impact test and Shore hardness test. Testing was conducted at different temperatures; ambient 23 °C and increased temperatures 60 ° and 100 °C. The results show a very large effect on Charpy properties and a lesser influence on the hardness of these mixtures. Mixture of smallest dust particles indicates larges change of measured properties. © 2018 Trans Tech Publications, Switzerland.

The presented paper deals with the problems associated with laser cutting of metal materials. Specifically, it solves the question of structural changes that occur as a result of the transfer of heat to the material. Experimental machining of selected technical materials was carried out, and on the basis of the hardness measurement near the cutting point, the heat-affected zone was evaluated after passing the laser beam. To confirm the detection of the affected zone width the models of transient temperature field were arranged, to represent the distribution of temperature in the vicinity of the cutting edge. © 2018 Trans Tech Publications, Switzerland.

Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behavior. This paper describes the effect of electron beam irradiation on the nano-indentation creep of unfilled and glass fiber filled Polypropylene (25%). Nano-indentation creep were measured by the DSI (Depth Sensing Indentation) method on samples which were non-irradiated and irradiated by different doses of the β – radiation (0, 30, 45 and 60 kGy). The purpose of the article is to consider to what extent the irradiation process influences the resulting nano-indentation creep measured by the DSI method. The unfilled and filled Polypropylene tested showed significant changes of indentation creep. The measured results indicate, that electron beam irradiation is very effective tool for improvement of creep properties of unfilled and filled Polypropylene. The nano-indentation creep after irradiated unfilled Polypropylene was decreased up to 16 % (filled Polypropylene was decreased up to 9%) compared to non-irradiated surface. These changes were examined and confirmed by Gel content. © 2018 Trans Tech Publications, Switzerland.

This paper studies different modelling methodologies for a calculation of the three point bend test. Test samples are composed of a rubber matrix and either steel or textile cords reinforcement. Prior to the bending tests, all of the used materials including the matrix and the reinforcement were measured to find out their mechanical properties. Rubber materials were described using hyperelastic models. FEM software MSC Marc/Mentat is employed as a calculation tool and its various functionalities are utilized for a description of the test composite models. The main observed outcome is a dependence of the vertical force causing the test sample deformation on the amount of the deformation. Calculated results are compared to each other and to measurements. Then, all the modelling techniques are evaluated. © 2018 Trans Tech Publications, Switzerland.

Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behaviour. This paper studies the effect of different doses of ionizing beta radiation on the micro-mechanical properties of commercially available polyamide. The measured results indicate, that electron beam irradiation is very effective tool for improvement of surface properties of PA6. In terms of micro-mechanical properties, the values of micro-hardness of surface layer increased by 24% at radiation dose of 132 kGy, stiffness of surface micro layer by 26% (132 kGy) as a result of different loads (0.5N and 2N). Improvement of micro-mechanical properties of radiated polyamide has a great significance also for industry. The modified polyamide shifts to the group of materials that have considerably better properties. Its micro-mechanical properties make polyamide ideal for a wide application in areas where higher resistance to wear, creep are required. Commonly manufactured PA6 can hardly fulfil these criteria. © 2018 Trans Tech Publications, Switzerland.

This research paper studies the influence of preparation method of recycled polymer material with glass fibers on the tensile properties of the final product. The recycled material was made from polypropylene, which originally contained 30 % of glass fibers. It was divided into fractions using size of the crushed particles. These fractions ranged from large particles, similar to the original material, to small dust particles. Measurements were performed at various temperatures. It was found that the mixture of dust particles showed a large decrease in measured properties. It is mainly due to shortening of the large glass fibers, so that it no longer fulfills its function as reinforcing filler. Conversely, mixture with larger particles did not show a significant decrease in properties compared to the original material. © 2017 Trans Tech Publications, Switzerland.

This research paper studies the influence of preparation method of recycled polymer material with glass fibers on the tensile properties of the final product. The recycled material was made from polypropylene, which originally contained 30 % of glass fibers. It was divided into fractions using size of the crushed particles. These fractions ranged from large particles, similar to the original material, to small dust particles. Measurements were performed at various temperatures. It was found that the mixture of dust particles showed a large decrease in measured properties. It is mainly due to shortening of the large glass fibers, so that it no longer fulfills its function as reinforcing filler. Conversely, mixture with larger particles did not show a significant decrease in properties compared to the original material. © 2017 Trans Tech Publications, Switzerland.

This paper deals with the flexural stiffness of sandwich structures based on fiberglass and polymeric foams. The influence of geometrical and material parameters on the resulting effective flexural stiffness of the sandwich structure is being studied experimentally, analytically and using FEM models. The effective elasticity module of the sandwich-structured element is being studied and it’s theoretical and model dependencies on the stiffness of the foam core are being investigated. These dependencies are then compared with experimentally observed values. This study shows it is necessary to pay special attention to the issue of flexural stiffness of walls when designing sandwich shell products in order to prevent possible failures in the practical applications of these types of structures. © 2016 Trans Tech Publications, Switzerland.

The aim of this research paper is to study the effect of particle size of recycled material on the microharness. Valuation of recycled material effect takes place in several mixtures of materials. These mixtures differ in particle size, which are made during grinding of plastic waste, from large particles similar to the original material to dust particles. The recycled material is always the same as is the original material. Tested material is styrene acrylonitrile SAN. Testing is performed at ambient temperature of 23°C. After the first recycling there is a change of hardness; which decrease mostly in mixture with the smallest particles. © 2016 Trans Tech Publications, Switzerland.

At the Alcoy Campus of the Universitat Politècnica de València, we were challenged to obtain the first double degree for our campus. This double degree was established for a Mechanical Engineering major, and our partner institution was Ostfalia Hochschule für Angewandte Wissenschaften, located in Wolfenbüttel campus. The agreement between the schools was signed in 2012, after three years of work. Students from either university could get an official diploma in Mechanical Engineering at both universities if they spent two consecutive semesters in the partner institution. This has many benefits for students and professors, which will be discussed in this paper, along with the main process followed to arrive to the final agreement.

The economic crisis that began in Spain at the end of 2007 and early 2008, which still lasts today, has greatly harmed industry in the country. Many companies dissolved, and many workers who worked for them remained unemployed. But what effect did the financial crisis have on universities? Apart from financial problems, they generally have had an increase in the number of students enrolled. Many of them are people who, after becoming unemployed, have decided to take time to improve their academic standing, and thus have more chances of finding a job when they finish. This paper will show how these people, with their knowledge and experience acquired in industry as workers, can add value to the manufacturing processes class.

This paper shows the authors experience in the implementation of cooperative learning during the fourth year of the Mechanical Engineering Grade, having involved from the second to the fourth year. Difficulties encountered are discussed.

This paper shows the authors experience in the implementation of cooperative learning during the fourth year of the Mechanical Engineering Grade, having involved from the second to the fourth year. Difficulties encountered are discussed.

The economic crisis that began in Spain at the end of 2007 and early 2008, which still lasts today, has greatly harmed industry in the country. Many companies dissolved, and many workers who worked for them remained unemployed. But what effect did the financial crisis have on universities? Apart from financial problems, they generally have had an increase in the number of students enrolled. Many of them are people who, after becoming unemployed, have decided to take time to improve their academic standing, and thus have more chances of finding a job when they finish. This paper will show how these people, with their knowledge and experience acquired in industry as workers, can add value to the manufacturing processes class.

This paper deals with the flexural stiffness of sandwich structures based on fiberglass and polymeric foams. The influence of geometrical and material parameters on the resulting effective flexural stiffness of the sandwich structure is being studied experimentally, analytically and using FEM models. The effective elasticity module of the sandwich-structured element is being studied and it’s theoretical and model dependencies on the stiffness of the foam core are being investigated. These dependencies are then compared with experimentally observed values. This study shows it is necessary to pay special attention to the issue of flexural stiffness of walls when designing sandwich shell products in order to prevent possible failures in the practical applications of these types of structures. © 2016 Trans Tech Publications, Switzerland.

Radiation crosslinking of polyamide 6 (PA 6) is a well-recognized modification of improving basic material characteristics. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behaviour. This research paper deals with the possible utilization of irradiated PA6. The material already contained a special cross-linking agent TAIC (5 volume %), which should enable subsequent cross-linking by ionizing β - radiation (15, 30 and 45 kGy). The effect of the irradiation on mechanical behavior of the tested PA 6 was investigated. Material properties created by β - radiation are measured by nano-indentation test using the DSI method (Depth Sensing Indentation). The change of nano-mechanical properties is greatly manifested mainly in the surface layer of the modified polyamide where a significant growth of nano-hardness values can be observed. The highest values of nano-mechanical properties were reached for the radiation dose of 45 kGy, when the nano-mechanical values increased by about 95%. These results indicate the advantage of the cross-linking in improving the mechanical properties of polyamide. © 2016 Trans Tech Publications, Switzerland.

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micro-mechanical changes in the surface layer of glass-fiber filled PA 66 modified by beta radiation were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. The specimens were prepared by injection technology and subjected to radiation doses of 0, 33, 66 and 99 kGy. The change of micro-mechanical properties is greatly manifested mainly in the surface layer of the modified polypropylene where a significant growth of micro-hardness values can be observed. Indentation modulus increased from 1.8 to 3.0 GPa (increasing about 66%) and indentation hardness increased from 87 to 157 MPa (increasing about 80%). This research paper studies the influence of the dose of irradiation on the micro-mechanical properties of semi-crystalline polyamide 66 filled by 30% glass fiber at room temperature. The study is carried out due to the ever-growing employment of this type of polymer. © 2016 Trans Tech Publications, Switzerland.

The aim of this research paper is to study the effect of particle size of recycled material on the microharness. Valuation of recycled material effect takes place in several mixtures of materials. These mixtures differ in particle size, which are made during grinding of plastic waste, from large particles similar to the original material to dust particles. The recycled material is always the same as is the original material. Tested material is styrene acrylonitrile SAN. Testing is performed at ambient temperature of 23°C. After the first recycling there is a change of hardness; which decrease mostly in mixture with the smallest particles. © 2016 Trans Tech Publications, Switzerland.

This paper deals with the mechanical properties of test specimens of commercially available PIM feedstocks based on a stainless steel powder. After injection molding, a part of the polymer binder has been removed in water. This process was followed by thermal removal of residual binder and sintering at 1360 °C in hydrogen atmosphere. For production of the mechanical test bars fresh and recycled feedstocks were employed. The aim is to determine the changes in mechanical performance resulting from injection molding processing stage, especially possible separation of feedstock components – the stainless steel powder and the polymer binder

This paper deals with utilization of recycled irradiated high-density polyethylene (rHDPEx) as a filler which was blended with non-modified high-density polyethylene (HDPE). Two blends were tested regarding the original state of the mixing components - HDPE granules/rHDPEx grit and HDPE granules/rHDPEx powder. Results show that the increasing amount of the rHDPEx, regardless its form, results in worsening both observed parameters - hardness and micro-indentation hardness. © (2015) Trans Tech Publications, Switzerland.

Bonding has experienced an enormous expansion in the various applications during the last few years in the field of material joining, due to which it is classified as a new joining technology, although it is, in fact, very old. Compared with the conventional joining methods (riveting, screwing and welding), bonding provides a new material combination possibilities and it allows us to obtain special shapes and properties, which can not be formed by conventional methods. To create a high-quality bonded joint, it is important to wet the bonded surface very well wetted by a wetting liquid. The wettability of the material is characterized by a contact angle of wetting, by which the surface energy is subsequently determined. For a high quality of the joint, the bonded material must have higher surface energy than the wetting liquid (adhesive) [1-3]. This paper describes the effect of plasma surface treatment on the surface properties (surface energy, microhardness) of low-density polyethylene (LDPE) and high-density polyethylene (HDPE), and also on the final strength of bonded joints. The measured results indicate, that plasma surface treatment is very effective tool for improvement of surface properties and strength of bonded joints of HDPE and LDPE. The strength of bonded joints after plasma surface treatment was increased up to 350 % compared to untreated material. A similar trend was observed even for surface energy and microhardness of materials. © (2015) Trans Tech Publications, Switzerland.

The main goal of this paper is to compare measurements of creep behavior of Crosslinking polymer materials. Creep properties have been measured by two methods, first is micro-indentation with Depth Sensing Indention (DSI) and the second method is long-term creep test in room temperature. These rather different methods enable better analyis of the influence of radiation crosslinking, and therefore better define the appropriate dose of radiation with respect to the use of polymer materials in practice. The evaluation criteria for DSI test is index CIT [%]. The evaluation criteria for the standard creep test is the value of average elongation at the end of the test. When comparing these two values is then possible to see a slight effect on the radiation dose for the standard creep test, which showed mikrocreepu only slightly.[1,2] © (2015) Trans Tech Publications, Switzerland.

Every manufacture of any plastic parts produces some waste, such as defective injects or cold runner system from injection molding technology. This waste can be directly used several times. But when size of this material is reduced, particles of different sizes are made. From large particles similar to the original granulate material, to dust particles. This size variation can cause problems during subsequent processing. These particles of different size have distinct melting rate. That can cause an inhomogeneity of a melt and diverse structure of solidified polymer. This research paper studies the influence of the particle size of recycled polymeric material on the micro harness properties of semi-crystalline polyamide 6 at room temperature. © (2015) Trans Tech Publications, Switzerland.

This paper deals with the mechanical properties of test specimens of commercially available PIM feedstocks based on a stainless steel powder. After injection molding, a part of the polymer binder has been removed in water. This process was followed by thermal removal of residual binder and sintering at 1360 °C in hydrogen atmosphere. For production of the mechanical test bars fresh and recycled feedstocks were employed. The aim is to determine the changes in mechanical performance resulting from injection molding processing stage, especially possible separation of feedstock components – the stainless steel powder and the polymer binder

This paper deals with utilization of recycled irradiated high-density polyethylene (rHDPEx) as a filler which was blended with non-modified high-density polyethylene (HDPE). Two blends were tested regarding the original state of the mixing components - HDPE granules/rHDPEx grit and HDPE granules/rHDPEx powder. Results show that the increasing amount of the rHDPEx, regardless its form, results in worsening both observed parameters - hardness and micro-indentation hardness. © (2015) Trans Tech Publications, Switzerland.

Every manufacture of any plastic parts produces some waste, such as defective injects or cold runner system from injection molding technology. This waste can be directly used several times. But when size of this material is reduced, particles of different sizes are made. From large particles similar to the original granulate material, to dust particles. This size variation can cause problems during subsequent processing. These particles of different size have distinct melting rate. That can cause an inhomogeneity of a melt and diverse structure of solidified polymer. This research paper studies the influence of the particle size of recycled polymeric material on the micro harness properties of semi-crystalline polyamide 6 at room temperature. © (2015) Trans Tech Publications, Switzerland.

Bonding has experienced an enormous expansion in the various applications during the last few years in the field of material joining, due to which it is classified as a new joining technology, although it is, in fact, very old. Compared with the conventional joining methods (riveting, screwing and welding), bonding provides a new material combination possibilities and it allows us to obtain special shapes and properties, which can not be formed by conventional methods. To create a high-quality bonded joint, it is important to wet the bonded surface very well wetted by a wetting liquid. The wettability of the material is characterized by a contact angle of wetting, by which the surface energy is subsequently determined. For a high quality of the joint, the bonded material must have higher surface energy than the wetting liquid (adhesive) [1-3]. This paper describes the effect of plasma surface treatment on the surface properties (surface energy, microhardness) of low-density polyethylene (LDPE) and high-density polyethylene (HDPE), and also on the final strength of bonded joints. The measured results indicate, that plasma surface treatment is very effective tool for improvement of surface properties and strength of bonded joints of HDPE and LDPE. The strength of bonded joints after plasma surface treatment was increased up to 350 % compared to untreated material. A similar trend was observed even for surface energy and microhardness of materials. © (2015) Trans Tech Publications, Switzerland.

Cross-linking is a process in which polymer branches are associated through chemical bonds. The cross-linking level can be adjusted by the irradiation dosage and often by means of a cross-linking booster. The polymer additional cross-linking influences the surface nano and micro layers in the way comparable to metals during the thermal and chemical-thermal treatments. The aim of this paper is to study the effect of ionizing radiation with different doses (33, 66 and 99 kGy), on micro-mechanical properties of polyethylene (HDPE) and compare these results with those of non-irradiated samples. Micro-mechanical properties increased with increasing value of the dose of irradiation material. The highest values of micro-mechanical properties were reached at radiation dose of 99 kGy, when the micro-hardness values increased by about 12%. The changes were examined and confirmed by X-ray diffraction. The changes were examined and confirmed by X-ray diffraction. © (2015) Trans Tech Publications, Switzerland.

The main goal of this paper is to compare measurements of creep behavior of Crosslinking polymer materials. Creep properties have been measured by two methods, first is micro-indentation with Depth Sensing Indention (DSI) and the second method is long-term creep test in room temperature. These rather different methods enable better analyis of the influence of radiation crosslinking, and therefore better define the appropriate dose of radiation with respect to the use of polymer materials in practice. The evaluation criteria for DSI test is index CIT [%]. The evaluation criteria for the standard creep test is the value of average elongation at the end of the test. When comparing these two values is then possible to see a slight effect on the radiation dose for the standard creep test, which showed mikrocreepu only slightly.[1,2] © (2015) Trans Tech Publications, Switzerland.

The aim of this research paper is to study the effect of particle size of recycled polymeric material to mechanical tensile properties. During grinding particles are formed which have a different size, shape and surface, from larger pieces to dust particles. During processing these particles melt at different rates depending on their size. For example they can cause material degradation or lack of melt homogeneity. Several recycled mixtures were prepared that had differed particle size after crushing. The recycled material is always the same as is the original material. The studied material was a Polycarbonate. Testing was performed using a tensile test. When comparing a virgin polycarbonate with recycled mixtures, the particle size of the recycled material affects some of the material parameters quite substantially, but it had no effect on some other properties. © (2014) Trans Tech Publications, Switzerland.

This research paper deals with utilization of recycled irradiated high-density polyethylene (HDPEx). Grit prepared of irradiated HDPEx was used as a filler into virgin low-density polyethylene (LDPE). Concentrations from 10 to 60 % were made and their influence on mechanical properties was investigated. Tensile test at ambient and elevated temperature was used to describe mechanical properties of resulting blends. Results show that there is an upward trend of elastic modulus and ultimate tensile strength and downward trend of nominal strain at ambient temperature. Similar findings were observed at elevated temperature, which might suggest possible utilization of such modified thermoplastic materials. However other material properties have to be tested to make final conclusion. © (2014) Trans Tech Publications, Switzerland.

Radiation processing of polymers is a well-established and economical commercial method of precisely modifying the properties of polymers. The principle of radiation processing is the ability of high energy radiation to produce reactive cations, anions and free radicals in materials. The industrial applications of the radiation processing of plastics and composites include polymerization, cross-linking, degradation and grafting. Radiation processing mainly involves the use of either electron beams from electron accelerators or gamma radiation from Cobalt-60 sources. The PBT Polybutylene terephthalate tested showed significant changes of temperature stability and mechanical properties after irradiation. From this point view, new applications could also be seen in areas with service temperatures higher than their former melting point. The comparison of the temperature stability and mechanical properties of irradiated and non-irradiated PBT is presented in this paper.

This research paper deals with an investigation of the influence of honeycomb core compression on the mechanical properties of sandwich structures. These structures consist of prepreg facing layers and two different material types of honeycomb and are produced by modified compression molding called Crush-Core technology. Produced structures are mechanically tested in three-point bending test and subjected to low-velocity impact and Charpy impact test.

Delivery of polymer melts into the mold cavity is the most important stage of the injection molding process. This paper shows the influence of cavity surface roughness and technological parameters on the flow length of rubber into mold cavity. The fluidity of polymers is affected by many parameters (mold design, melt temperature, injection rate and pressures) and by the flow properties of polymers. Results of the experiments carried out with selected types of rubber compounds proved a minimal influence of surface roughness of the runners on the polymer melt flow. This considers excluding (if the conditions allow it) the very complex and expensive finishing operations from the technological process as the influence of the surface roughness on the flow characteristics does not seem to play as important role as was previously thought. Application of the measurement results may have significant influence on the production of shaping parts of the injection molds especially in changing the so far used processes and substituting them by less costly production processes which might increase the competitiveness of the tool producers and shorten the time between product plan and its implementation.

Little research was done to investigate possible utilization of irradiated materials after the end of their lifetime. This research paper deals with the possible utilization of irradiated high-density polyethylene (HDPEx) after its service life. Irradiated HDPE was used as filler into the virgin low-density polyethylene (LDPE). Three material combinations were investigated (powder/powder, granules/powder and granules/grit) and influence of the filler on optical behavior was measured. Terahertz spectroscopy at wide range of frequencies was used for refractive index determination. According to measured data there is significant influence by the amount of the filler. Moreover influence of particle size was also observed. All three combinations have similar curve courses; however the most consistent results were achieved at the powder/powder combination. Behavior of virgin LDPE and virgin HDPE is in correlation with previous findings.

The aim of the paper is to study the effect of the surface shape and perforation of plastics on sound absorption. Samples with different asperity heights, depths and numbers of holes were prepared by means of CNC milling machine. Experimental measurements of frequency dependencies of the sound absorption coefficient were realized by the transfer function method using Kundt́s impedance tube at normal incidence of acoustic wave on the investigated materials. The study was performed on two types of polyurethanes. Different factors, that have influence on sound absorption, are evaluated in the conclusion of this work. Both investigated materials are also compared in terms of their ability to absorb sound. © (2014) Trans Tech Publications, Switzerland.

Nowadays, manufacturers and users of parts made of polymeric materials make increasing demands on surface quality of these parts. In order to fulfill these claims, it is necessary to use not only the quality measurement systems for surface quality inspection, but also suitable products that allow to set up the inspected polymeric component properly set up to the measuring system scanner. However, it is not sufficient. Due to the requirements of the customers or the production it is often necessary to repeat the surface quality measurement, which is more and more often done in 3D; that might be quite difficult. Except for special cases there should not be any marks done by the inspection workplace which might lower the inspected surface quality. Therefore it is not suitable to make mechanical marks such as scratch, ridge, etc. On the other hand, other types of marks done by non-invasive method, such as sticking paper marks, measuring cross, etc. is also not admissible as there might result in surface damage due to adhesive forces as well by mechanical or chemical processes. Thus it is necessary to take into account the fact that parts made of polymeric material can be so small that none of the above mentioned methods that are widely used nowadays cannot be applied just because of the dimensional reason. © (2014) Trans Tech Publications, Switzerland.

This work deals with a development of a tool for ear ventilation tube production. Ear tubes are medical devices, which allow ventilation and provide pressure equalization in the middle ear cavity for prolonged period of time; in case of repetitive inflammation. These implants are normally made from metals or classical polymeric materials. Whereas, today, the effort is to develop bioresorbable tubes based on polylactic acid, which could replace currently used material. The benefit provides no requirement of secondary surgery for their removal. The size of ear implants is only in millimetres and the tool for their manufacturing requires a special technology. In this paper, two tubes and a transfer mold for their production was designed using 3D CAD software Catia V5R18. Subsequently, the special manufacturing process for the mold cavity plates using the rapid prototyping and electroforming technology was proposed. The designed tool is intended for biodegradable tubes, which will be further tested in the laboratory. © (2014) Trans Tech Publications, Switzerland.

This research paper deals with behavior of recycled material at higher temperature. Assessment of recycled material influence takes place on four kinds of thermoplastic materials, which are always high-heat polycarbonate (PC-HT) with different amount of recycled material (pure polycarbonate, polycarbonate with twenty percent of recycled material, polycarbonate with thirty percent of recycled material and hundred percent of recycled polycarbonate). Specimens were prepared by the mostly used technology for production products, which is injection molding. Each kind of material is one by one loaded by high temperature 110°C and consequently tested. This temperature was chosen because we encounter products made with recycled material additive, which can be used at elevated temperatures. To determine behavior of recycled material at this high temperature, one basic mechanic material tests is used. This test is normalized compression test. © (2014) Trans Tech Publications, Switzerland.

This research paper focuses on grinding of materials used for tools (100Cr6 (CSN 4 14109), X210Cr12 ( CSN 4 19436) and epoxy resin) using grinding wheels from cubic boron nitride and diamond. The disadvantage of grinding of difficult-to-machine materials is higher wear of grinding wheels. The modern grinding wheels are able to achieve high accuracy of dimensions and high surface quality with a smaller wear of grinding wheels then grinding wheels from conventional materials. Correctly selected technological conditions are one of the most important matters to achieve the required surface quality. The main aim of this research is to determine the influence of technological conditions to quality of surface after planar grinding. The research determines the influence of the grain type of grinding wheels, feed rate and cutting depth on the quality of functional surfaces.

The aim of this research paper is to study the effect of particle size of recycled polymeric material to mechanical tensile properties. During grinding particles are formed which have a different size, shape and surface, from larger pieces to dust particles. During processing these particles melt at different rates depending on their size. For example they can cause material degradation or lack of melt homogeneity. Several recycled mixtures were prepared that had differed particle size after crushing. The recycled material is always the same as is the original material. The studied material was a Polycarbonate. Testing was performed using a tensile test. When comparing a virgin polycarbonate with recycled mixtures, the particle size of the recycled material affects some of the material parameters quite substantially, but it had no effect on some other properties. © (2014) Trans Tech Publications, Switzerland.