Z. Kowalewski - Academia.edu (original) (raw)

Papers by Z. Kowalewski

Archives of Civil and Mechanical Engineering

The aim of this research was to compare the effectiveness of two different optical measurement te... more The aim of this research was to compare the effectiveness of two different optical measurement techniques (digital image correlation—DIC and electronic speckle pattern interferometry—ESPI) during fatigue damage development monitoring in X10CrMoVNb9-1 (P91) power engineering steel for pipes. The specimens machined from the as-received pipe were subjected to fatigue loadings and monitored simultaneously using DIC and ESPI techniques. It was found that DIC technique, although characterised by lower resolution, was more effective than ESPI. DIC allows to monitor the fatigue behaviour of steel specimens and accurately indicate the area of potential failure even within the initial stage of fatigue damage development.

The Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics

Proceedings of the 3rd Polish Congress of Mechanics (PCM) and 21st International Conference on Computer Methods in Mechanics (CMM), Gdansk, Poland, 8-11 September 2015, 2016

Metallic Materials, 2016

The results of analysis of fatigue damage development in the X10CrMoVNb9-1 (P91) steel specimens ... more The results of analysis of fatigue damage development in the X10CrMoVNb9-1 (P91) steel specimens subjected to various cyclic loading combinations are presented. The study concerning a quantitative assessment of damage is based on analysis of the fatigue hysteresis evolution in subsequent loading cycles. According to the elaborated algorithms, damage parameters were determined on the basis of two indicators, i.e., average strain and strain amplitude variations. Each of them was responsible for a single damage development mechanism. The average strain characterized ratcheting effect, which is usually related to local generation of plastic strain surrounding microstructural elements. The second damage mechanism called cyclic plasticity is connected with micro slips preceding slip bands formation. The paper also discusses the results of metallographic and fractographic microscopic (SEM) observations of the tested specimens in order to indicate microstructural aspects of fatigue damage development mechanisms.

EPJ Web of Conferences, 2010

Engineering Plasticity and Its Applications from Nanoscale to Macroscale - Proceedings of the 9th AEPA2008, 2009

ABSTRACT

Strain, 2014

ABSTRACT Determination of cyclic properties of a material used for many engineering structures, e... more ABSTRACT Determination of cyclic properties of a material used for many engineering structures, e.g. airframes, requires preparation of specimens from two-dimensional, shell structures. A specimen must be cut out from the structure component in the way allowing application of a load corresponding to that reflecting service cases. In order to fulfil this requirement, tension–compression testing of the flat specimen is necessary to obtain credible data. Problems associated with such kind of testing are discussed in this paper. In the first part, an extensive review of the anti-buckling fixtures developed up to now is given. Several representative solutions are discussed, with special emphasis on the technique limitations. In the second part of the paper, detailed description of the proposed design is given. Finally, the results of preliminary tests carried out using new fixture to mount the flat specimens cut from steel sheets are presented. Application of the proposed testing technique allowed tension–compression tests to be performed at the displacement amplitude within the range ±5 mm what corresponds to the maximum strain amplitude of ±0.4 for the specimen gauge length to be equal 12.5 mm. Taking into account all data captured by means of new fixture, one can conclude that the technique is promising with respect to providing data for modelling of cyclic deformation behaviour for shell structures.

Strain, 2011

An influence of the chemical composition, porosity and ageing on mechanical behaviour of light, m... more An influence of the chemical composition, porosity and ageing on mechanical behaviour of light, multifunctional aluminium alloys (AlSi8Cu3 and AlSi7MgCu0.5) subjected to creep and low cycle fatigue (LCF) was investigated. The materials were tested to verify their applicability as the cylinder heads in car engines. During creep tests, a strain response of the materials was observed under a range of the step-increased stresses and different temperatures. The LCF tests were carried out under strain control in three blocks of 100 cycles each with a constant strain amplitude. The results of creep and LCF tests were analysed with regard to chemical composition, type of porosity and ageing of the materials tested. An influence of porosity on the creep resistance and lifetime was considered. The results of the LCF tests were compared for the materials in the as-received state and after ageing. An experimental evaluation of cyclic behaviour because of the LCF was carried out to check whether the hardening or softening effects can be observed in the materials. Taking into account the various history of loading, a stress response of the materials was investigated.

Materials Research Innovations, 2011

Materials Research Innovations, 2011

ABSTRACT The paper presents experimental investigations of two light aluminium alloys (AlSi8Cu3 a... more ABSTRACT The paper presents experimental investigations of two light aluminium alloys (AlSi8Cu3 and AlSi7MgCu0.5) under loading conditions leading to the creep or fatigue processes. During the creep process, the strains were measured under selected tensile stresses and temperatures. An influence of a step loading during creep, at elevated temperature, on steady creep rate and a course of creep curve, was investigated. Moreover, an effect of porosity degree on creep of both aluminium alloys was also analysed. An influence of aging process at the elevated temperature was experimentally evaluated. Fatigue behaviour of materials was checked under strain control using cylindrical samples. The results of LCF tests were analysed for the materials subjected to three-stage sequence of loading at elevated temperature. A resistance to creep and fatigue processes of the AlSi8Cu3 was weaker than that obtained in the case of the AlSi7MgCu0.5.

The Journal of Strain Analysis for Engineering Design, 2004

ABSTRACT

The Journal of Strain Analysis for Engineering Design, 1994

A number of mechanisms-based constitutive equations were assessed in an effort to describe the cr... more A number of mechanisms-based constitutive equations were assessed in an effort to describe the creep behaviour of an aluminium alloy at 150°C. It was found that a sinh function of stress, rather than the usually used power law, is best able to describe the strain rate and rupture behaviour over the narrow stress range analysed. A single state variable theory which represents a dominant damage mechanism is not capable of predicting the shape of the tertiary curve; however, a two state variable theory which represents two mechanisms provides a good description. The two relevant mechanisms identified are creep-constrained cavitation and ageing of the particulate microstructure. The non-linear equations which describe both these physical mechanisms are complex and strongly coupled. This makes it difficult to determine the constants in the constitutive equations from experimental data. The paper reports the development of automated numerical optimization techniques which overcome these d...

Journal of Materials Processing Technology, 2001

This paper presents an experimental evaluation of the effects induced in the selected engineering... more This paper presents an experimental evaluation of the effects induced in the selected engineering alloys (brass and aluminium alloy) by annealing and ageing. Both materials were tested in the as-received state and after annealing. In the case of brass, an influence of the ageing process on the subsequent mechanical properties under complex monotonic loading was also investigated. An analysis of

International Journal of Plasticity, 1991

The aim of this paper is to present results of creep experiments carried out on thinwalled tubula... more The aim of this paper is to present results of creep experiments carried out on thinwalled tubular specimens of pure copper under combined tension and torsion at 573 K. The experimental program consists of creep tests for the material in the virgin state, and for the same material prestrained plastically at the room temperature by uniaxial tension or by pure torsion. The modified Norton's law, based on experimental observations, was proposed to describe the rate of secondary creep. This modification is based on the assumption that the material parameters may be expressed as the functions depending on the direction of the loading stress vector. Results are discussed in terms of a creep surface concept. The changes in size and shape of the creep surfaces caused by plastic prestrains express the evolution of the initial creep surface for virgin material.

Archives of Civil and Mechanical Engineering

The aim of this research was to compare the effectiveness of two different optical measurement te... more The aim of this research was to compare the effectiveness of two different optical measurement techniques (digital image correlation—DIC and electronic speckle pattern interferometry—ESPI) during fatigue damage development monitoring in X10CrMoVNb9-1 (P91) power engineering steel for pipes. The specimens machined from the as-received pipe were subjected to fatigue loadings and monitored simultaneously using DIC and ESPI techniques. It was found that DIC technique, although characterised by lower resolution, was more effective than ESPI. DIC allows to monitor the fatigue behaviour of steel specimens and accurately indicate the area of potential failure even within the initial stage of fatigue damage development.

The Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics

Proceedings of the 3rd Polish Congress of Mechanics (PCM) and 21st International Conference on Computer Methods in Mechanics (CMM), Gdansk, Poland, 8-11 September 2015, 2016

Metallic Materials, 2016

The results of analysis of fatigue damage development in the X10CrMoVNb9-1 (P91) steel specimens ... more The results of analysis of fatigue damage development in the X10CrMoVNb9-1 (P91) steel specimens subjected to various cyclic loading combinations are presented. The study concerning a quantitative assessment of damage is based on analysis of the fatigue hysteresis evolution in subsequent loading cycles. According to the elaborated algorithms, damage parameters were determined on the basis of two indicators, i.e., average strain and strain amplitude variations. Each of them was responsible for a single damage development mechanism. The average strain characterized ratcheting effect, which is usually related to local generation of plastic strain surrounding microstructural elements. The second damage mechanism called cyclic plasticity is connected with micro slips preceding slip bands formation. The paper also discusses the results of metallographic and fractographic microscopic (SEM) observations of the tested specimens in order to indicate microstructural aspects of fatigue damage development mechanisms.

EPJ Web of Conferences, 2010

Engineering Plasticity and Its Applications from Nanoscale to Macroscale - Proceedings of the 9th AEPA2008, 2009

ABSTRACT

Strain, 2014

ABSTRACT Determination of cyclic properties of a material used for many engineering structures, e... more ABSTRACT Determination of cyclic properties of a material used for many engineering structures, e.g. airframes, requires preparation of specimens from two-dimensional, shell structures. A specimen must be cut out from the structure component in the way allowing application of a load corresponding to that reflecting service cases. In order to fulfil this requirement, tension–compression testing of the flat specimen is necessary to obtain credible data. Problems associated with such kind of testing are discussed in this paper. In the first part, an extensive review of the anti-buckling fixtures developed up to now is given. Several representative solutions are discussed, with special emphasis on the technique limitations. In the second part of the paper, detailed description of the proposed design is given. Finally, the results of preliminary tests carried out using new fixture to mount the flat specimens cut from steel sheets are presented. Application of the proposed testing technique allowed tension–compression tests to be performed at the displacement amplitude within the range ±5 mm what corresponds to the maximum strain amplitude of ±0.4 for the specimen gauge length to be equal 12.5 mm. Taking into account all data captured by means of new fixture, one can conclude that the technique is promising with respect to providing data for modelling of cyclic deformation behaviour for shell structures.

Strain, 2011

An influence of the chemical composition, porosity and ageing on mechanical behaviour of light, m... more An influence of the chemical composition, porosity and ageing on mechanical behaviour of light, multifunctional aluminium alloys (AlSi8Cu3 and AlSi7MgCu0.5) subjected to creep and low cycle fatigue (LCF) was investigated. The materials were tested to verify their applicability as the cylinder heads in car engines. During creep tests, a strain response of the materials was observed under a range of the step-increased stresses and different temperatures. The LCF tests were carried out under strain control in three blocks of 100 cycles each with a constant strain amplitude. The results of creep and LCF tests were analysed with regard to chemical composition, type of porosity and ageing of the materials tested. An influence of porosity on the creep resistance and lifetime was considered. The results of the LCF tests were compared for the materials in the as-received state and after ageing. An experimental evaluation of cyclic behaviour because of the LCF was carried out to check whether the hardening or softening effects can be observed in the materials. Taking into account the various history of loading, a stress response of the materials was investigated.

Materials Research Innovations, 2011

Materials Research Innovations, 2011

ABSTRACT The paper presents experimental investigations of two light aluminium alloys (AlSi8Cu3 a... more ABSTRACT The paper presents experimental investigations of two light aluminium alloys (AlSi8Cu3 and AlSi7MgCu0.5) under loading conditions leading to the creep or fatigue processes. During the creep process, the strains were measured under selected tensile stresses and temperatures. An influence of a step loading during creep, at elevated temperature, on steady creep rate and a course of creep curve, was investigated. Moreover, an effect of porosity degree on creep of both aluminium alloys was also analysed. An influence of aging process at the elevated temperature was experimentally evaluated. Fatigue behaviour of materials was checked under strain control using cylindrical samples. The results of LCF tests were analysed for the materials subjected to three-stage sequence of loading at elevated temperature. A resistance to creep and fatigue processes of the AlSi8Cu3 was weaker than that obtained in the case of the AlSi7MgCu0.5.

The Journal of Strain Analysis for Engineering Design, 2004

ABSTRACT

The Journal of Strain Analysis for Engineering Design, 1994

A number of mechanisms-based constitutive equations were assessed in an effort to describe the cr... more A number of mechanisms-based constitutive equations were assessed in an effort to describe the creep behaviour of an aluminium alloy at 150°C. It was found that a sinh function of stress, rather than the usually used power law, is best able to describe the strain rate and rupture behaviour over the narrow stress range analysed. A single state variable theory which represents a dominant damage mechanism is not capable of predicting the shape of the tertiary curve; however, a two state variable theory which represents two mechanisms provides a good description. The two relevant mechanisms identified are creep-constrained cavitation and ageing of the particulate microstructure. The non-linear equations which describe both these physical mechanisms are complex and strongly coupled. This makes it difficult to determine the constants in the constitutive equations from experimental data. The paper reports the development of automated numerical optimization techniques which overcome these d...

Journal of Materials Processing Technology, 2001

This paper presents an experimental evaluation of the effects induced in the selected engineering... more This paper presents an experimental evaluation of the effects induced in the selected engineering alloys (brass and aluminium alloy) by annealing and ageing. Both materials were tested in the as-received state and after annealing. In the case of brass, an influence of the ageing process on the subsequent mechanical properties under complex monotonic loading was also investigated. An analysis of

International Journal of Plasticity, 1991

The aim of this paper is to present results of creep experiments carried out on thinwalled tubula... more The aim of this paper is to present results of creep experiments carried out on thinwalled tubular specimens of pure copper under combined tension and torsion at 573 K. The experimental program consists of creep tests for the material in the virgin state, and for the same material prestrained plastically at the room temperature by uniaxial tension or by pure torsion. The modified Norton's law, based on experimental observations, was proposed to describe the rate of secondary creep. This modification is based on the assumption that the material parameters may be expressed as the functions depending on the direction of the loading stress vector. Results are discussed in terms of a creep surface concept. The changes in size and shape of the creep surfaces caused by plastic prestrains express the evolution of the initial creep surface for virgin material.