oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 13 )

2019 ( 199 )

2018 ( 248 )

2017 ( 273 )

Custom range...

Search Results: 1 - 10 of 191470 matches for " G. Wróbel "
All listed articles are free for downloading (OA Articles)
Page 1 /191470
Display every page Item
Ultrasonic methods in diagnostics of polyethylene
G. Wróbel,?. Wierzbicki
Archives of Materials Science and Engineering , 2007,
Abstract: Purpose: The aim of the work was to find relationship between the ultrasonic wave velocity and the strenght and stess in a polyethylene specimens.Design/methodology/approach: The experiments have been performed in three distinct phases. During the first phase, typical polyethylene was ageing to get different mechanical properties. In the second phase, strength and ultrasonic properties of composite was testing. In the last of phases we compare changes of properties.Findings: The experimental results showed relationship between velocity of ultrasonic wave and strength and stress in a polyethylene specimens.Research limitations/implications: In the future test will be necessary to use more precise testing equipment. Perhaps we will use other ultrasonic probes of lower frequency. In this experiment we used 2 MHz probes. It is necessary to run an experiment with more specimens. Further work is needed in the correlations between ultrasound and stress area.Practical implications: The results of the investigation have shown possibility of using ultrasonic method to diagnosis of strength changes in polymers materials. This method allowed to test working parts of machines or buildings, without destruction.Originality/value: The results of the investigations allow to confirm, that ultrasonics can be used to non-destructive testing of the strength and Young’s modulus changes.
Ultrasonic methods in diagnostics of glass-polyester composites
G. Wróbel,?. Wierzbicki
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The aim of the work was to find relationship between the ultrasonic wave velocity and the strenghtand Young’s module in a glass-polyester composite.Design/methodology/approach: The experiments have been performed in three distinct phases. During the firstphase, typical glass-polyester composite was ageing to get different mechanical properties. In the second phase,strength and ultrasonic properties of composite was testing. In the last of phases we compare changes of properties.Findings: The experimental results showed relationship between velocity of ultrasonic wave and strength andYoung’s module.Research limitations/implications: In those applications, in which polymer structural composites were subjectedto a heat and mechanical load, it is essential to test the strength characteristics of the composites in the use of nondestructivemethods. That enables contemporaneous status check of the structure and makes it possible to replacethe bivalent evaluation scale (good – bad) with an incessantly gradable strength degradation scale for a material.Practical implications: The results of the investigation have shown possibility of using ultrasonic methodto diagnosis of strength changes in composites. This method allowed to test working parts of machines orbuildings, without destruction.Originality/value: The results of the investigations allow to confirm, that ultrasonics can be used to nondestructivetesting of the strength and Young’s modulus changes.
A computer model of the process of polymer materials fatigue destruction
G. Wróbel
Journal of Achievements in Materials and Manufacturing Engineering , 2010,
Abstract: Purpose: In the paper an evolutionary model of fatigue destruction was described. The aim is in as much as possible faithful modeling of processes during constructional materials exploitation observed, particularly progressing of strength ability loss or other useful characteristics changes.Design/methodology/approach: The MES was choosed as a discretisation method. The model evolution goes sequentialy – chaotic system modification by actual state analysis is preceded. Evolution stage and material state characteristics evaluation give a bases of destruction extend nondestructive evaluation.Findings: The example gives an evolutionary acoustic properties of polymeric composite change illustration. It points the model diagnostic value.Research limitations/implications: In order to obtain reliable results, there are many factors to be considered such as real three-dimensional composite structure, type and quality of composite components, particularly reinforcement and others. Further work is needed in this area.Practical implications: The results obtained would be of considerable importance in the computer aided diagnostic method of polymer composite materials.Originality/value: A new approach to the problem of investigation of polymeric composite’s fatigue destruction has been demonstrated by means of computer simulation procedure. The method developed should be of interest to the industrial quality control applications and forecasting of important mechanical characteristics of composite materials, exploited in fatigue conditions.
Ultrasonic evaluation of the fibre content in glass/epoxy composites
G. Wróbel,S. Pawlak
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: The aim of the work was to find relationships between the selected parameter of an ultrasonic waveand the local fibre content in a glass/epoxy composite.Design/methodology/approach: The experiments have been performed in two distinct phases. During the firstphase, typical glass/epoxy composite materials with different fibre content were examined by means of throughtransmissionand pulse-echo ultrasonics.In the second phase, the standard destructive method was applied to determine the actual glass content ininvestigated composite materialsFindings: The experimental results showed relationships between ultrasonic wave velocity and the local fibrecontent in investigated composite materials. This study has also assessed the ability of pulse-echo technique tocarry out such a testing.Research limitations/implications: Relationships found may be useful to local fibre content examination, but foreach composite material different relationships are required to be determined, as was done in the present study.Practical implications: The described method can be applied to the post-production quality control of a finishedcomposite product, but in the case of composites made of different components it is necessary to determinedistinct relationships for each material.Originality/value: A new approach to the problem of fibre content examination has been demonstrated bymeans of pulse-echo technique. The method developed should be of interest to the industrial quality controlprocedures and has great importance for products with a high failure-free requirements.
Thermographic method of fatigue assessment of polymeric materials
M. Rojek,G. Wróbel
Journal of Achievements in Materials and Manufacturing Engineering , 2010,
Abstract: Purpose: The article presents the adoption of thermal imaging techniques in assessing methodology of the fatigue degradation degree of the polymeric materials.Design/methodology/approach: Epoxy composites reinforced with glass fiber have been subjected to three point method fatigue bending. The degraded materials were then tested using thermovision method.Findings: In experiments the temperature changes velocity of the samples was determined in the conditions of infrared radiation. The dependence between speed up of temperature and the number of fatigue cycles was determined. With an increasing a number of fatigue cycles drop in temperature speeds up was observed.Research limitations/implications: Restriction is a condition of loading state - as homogeneous as possible, and hence the homogeneous degradation state of the material.Practical implications: Designated diagnostic relation gives a basis for non-destructive evaluation of the degree of exhaustion of load-bearing capacity of the material.Originality/value: Original value of the paper are the experimental results proving the effectiveness of non-destructive thermographic methods for polymeric materials diagnosis.
The importance of PET filtration for the possibility of material recycling
G. Wróbel,R. Bagsik
Journal of Achievements in Materials and Manufacturing Engineering , 2010,
Abstract: Purpose: With the development increasing of plastics production the problems associated with their disposal have appeared on. Because of the large volume of plastic wastes and their limited long-term resolution, there is a need for treatment and reuse. For this purpose, with tests of properties, studies on plastics recycling and reprocessing into new products (recyclate) are conducted. The basic technological problem connected with using of secondary material is to clean it. The basic utility problem is the impact of recycling operations on the properties of the secondary material. The work to this issue is mainly devoted.Design/methodology/approach: One of the basic surgery to restore the plastics reusing ability is impurities removing. An available modern way is to use a specialized system of filtration sieves. Optimization problem is to select the proper filter in terms of mechanical properties of the resulting recyclate. In the work, the secondary material with using of grid filter of varying size has been tested. Prepared, with using of purified secondary plastic, three layer film to tensile test was subjected.Findings: The result of the tests described in this work is the preliminary determination of the filtration effect on the mechanical characteristics of the selected secondary materials.Research limitations/implications: The results confirm the impact of the quality of filtration of thermoplastics in the process of secondary processing on the base product properties. The accuracy of the pollution elimination process affects directly on the mechanical characteristics of secondary material. Used in the research procedure filtration system with automatic filter change operation helps to minimize the impact of filtering on the performance of the extrusion process.Practical implications: Practical benefit of the study is the confirmation of the possibility and desirability of material recycling, particularly with using of modern filtration system.Originality/value: The original value of the research are qualitative and quantitative assessment of the effects of filtration on the characteristics of the secondary material.
Numerical simulation of fatigue degradation process of polymer materials using diagnostic acoustic characteristics
G. Wróbel,J. Kaczmarczyk
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The objective of the work was to construct the finite elements model for simulation of acoustic wave propagation process in polymer material in the aspect of diagnostic of fatigue changes.Design/methodology/approach: Flat model was composed from finite elements with elastic properties of represented medium. Procedure of model modification corresponding with material fatigue degradation was presented. Acoustic and strength characteristics achieved as a result of numerical analysis gave the basis of numerical diagnostic of degradation process.Findings: Structural modification possibilities of numerical model needed to obtain conformity of experimentally affirmed correlation of strength and acoustic characteristics of material have been indicated.Research limitations/implications: Developed method allows the identification of material’s residual load capacity state on the basis of given, determined in diagnostic process its acoustic characteristics. The method also enables the simulation of variable fatigue process of material in complex constructional conditions.Practical implications: Practical utilization of the model consists in prediction possibility of material state of complex constructional elements in varied operating conditions – on the basis of failure cumulation hypothesis.Originality/value: The value of developed model is in its practical usability in simulation diagnostic process. Simulation method with idea of diagnostic simulation is the original part of the present work.
A comparison study of the pulse-echo and through-transmission ultrasonics in glass/epoxy composites
G. Wróbel,S. Pawlak
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The aim of the present study was to assess the limits and compare abilities of the pulse-echo and through-transmission ultrasonics to evaluate a chosen property of composite materials.Design/methodology/approach: Two different ultrasonic non-destructive techniques were employed to measure the mechanical wave velocity in glass/epoxy composites. The study was performed on various specimens with different glass content at the range from 30 to 65%. The exact glass content in examined materials was determined using the standard destructive analysis.Findings: A comparison showed that the results obtained for the wave velocity from pulse-echo and through-transmission are in good agreement, indicating that both techniques can be considered as a quantitative non-destructives tools of local fiber content evaluation. The results are presented in the form of linear relationships of wave velocity versus fiber content in the composite materials.Research limitations/implications: In order to obtain lower dispersion of data, there are many factors to be considered such as void content in composite materials and/or transducer frequency of ultrasonic device, which were out of the scope of the present study.Practical implications: The considered ultrasonic techniques can be applied to the industrial quality control of composite products, but for any different composite structures, distinct relationships should be determined.Originality/value: The results presented would be of interest to the industrial quality procedures, especially in the case of products with high failure-free requirements.
Influence of temperature on the viscoelastic properties of drawn PE pipes
M. Szymiczek,G. Wróbel
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: Purpose of this paper is to describe the free drawing process of PE pipes in the aspect of timecharacteristics of the viscoelastic return.Design/methodology/approach: To determine the properties, drawing tests were conducted on chosen PE pipes, usinga testing machine station. Pipe samples were preheated to a set temperature and drawn by a fixed drawing die. Changesin the pipe diameter and length of the test section were recorded for the further analysis of the pipe sample.Findings: Obtained dependencies were assumed to be the basis for formulation of conclusions as to the choiceof essential process conditions for the technological sequence of PE lining deposition in the outer coating ofinstallation pipes or reconstruction of a transmission channel.Research limitations/implications: Conducted research and their conclusions have a methodological value.They factually correspond to chosen spatial parameters of pipes and dies. Together with parallel tribologicalresearch on the conditions in the drawing die zone, they give a basis for building a model of the reverse drawingprocess with its all complexity.Practical implications: From a practical point of view, the obtained results allow to optimize the expansivedeposition process of PE pipes in production of new and renovation of damaged elements of transmissionnetworks – in the latter case, mainly in digless conditions.Originality/value: Original input of these works is determination of simultaneous influence of geometricalproperties – the degree of inner diameter reduction of the pipe and the approach angle of the drawing die – andthe temperature of the examined material on the time characteristics and participation of plastic strain in theprocess of viscoelastic after-deformation return.
Influence of temperature on friction coefficient of low density polyethylene
G. Wróbel,M. Szymiczek
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: The article describes influence of temperature on friction coefficient of low density polyethylene in the aspect of loads occurring in a drawing die during free drawing of pipes.Design/methodology/approach: Research was conducted on the basis of the PN-EN ISO standard.Findings: The paper presents results of friction coefficient research. The research was conducted on a testing machine with a special design table for measurement of friction in different, set temperatures. The paper resulted in characteristics of correlation between examined friction coefficient and temperature.Research limitations/implications: Research on dependence allows to evaluate thickness of the plasticized layer in free drawn PE pipes. Thickness of the plasticized layer depends on the value of friction coefficient. This is important in case of after-deformation returns which allows tight fitting of polyethylene lining during digless pipe reconstruction.Practical implications: Results of conducted research allow to verify the mathematical model describing a process of free pipe drawing.Originality/value: Research was conducted on exclusively prepared samples, which allows to reproduce conditions inside a drawing die.
Page 1 /191470
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.