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1
Content available Thin inclusion in elastic body: identification of damage parameter
Khludnev Alexander
Control and Cybernetics
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2019
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Vol. 48, No. 1
13--29
EN
In the paper, we consider an equilibrium problem for a 2D elastic body with a thin elastic inclusion crossing an external boundary. The elastic body has a defect which is characterized by a positive damage parameter. The presence of a defect means that the problem is formulated in a non-smooth domain. Non-linear boundary conditions at the defect faces are imposed to prevent the mutual penetration between the faces. Both variational and differential problem formulations are proposed, and existence of solutions is established. We study an asymptotics of solutions with respect to the damage parameter as well as with respect to a rigidity parameter of the inclusion. Identification problems for finding the damage parameter are investigated. To this end, existence of solutions of optimal control problems is proven.
2
Content available Tests of damage to Inconel 718 alloy used in aviation
Krysztofik J., Socha G.
Prace Instytutu Lotnictwa
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2017
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Nr 1 (246)
104--116
EN
Inconel 718 alloy was tested. A new type of specimens of variable cross-sectional area measuring part was used for the tests. This provided a continuous distribution of plastic strain in that part of the sample. The proposed method enables to replace a series of specimens by one specimen. The degradation of the material u:as obtained by static tensile test and the creep test. The permanent deformation that varies along the specimen axis allows for an analysis of damage induced by a plastic deformation. The degradation of the alloy corresponds with the changes of acoustics properties of the material - attenuation of ultrasonic waves. It allows to determine the degree of damage to the material using a non-invasive - ultrasonic method. Using the damage parameter proposed by Johnson allows to obtain correlation between the non-destructive results and a damage degree of the material. The presented testing method delivers information about changes in the material structure caused by permanent deformation.
PL
Badaniom materiałowym poddano stop Inconel 718. Do badań użyto nowy rodzaj próbki o zmiennym polu przekroju części pomiarowej. Dzięki temu uzyskano ciągły rozkład odkształceń plastycznych w tej części próbki. Zaproponowana metoda badania uszkodzenia struktury prowadzi do zastąpienia w badaniach serii próbek jedną próbką. Degradację materiału zadano poprzez statyczną próbę rozciągania i próbę pełzania. Deformacja trwała, która zmienia się wzdłuż osi próbek, umożliwia analizę uszkodzenia wywołanego odkształceniem plastycznym. Z degradacją badanego stopu wiążą się zmiany jego właściwości akustycznych -współczynnika tłumienia materiału. Pozwala to na określenie stopnia uszkodzenia materiału za pomocą bezinwazyjnej metody nieniszczącej -metody ultradźwiękowej. Stosując parametr uszkodzenia zaproponowany przez Johnsona uzyskano korelację pomiędzy wynikami pomiarów nieniszczących a stopniem uszkodzenia materiału. Zastosowana w przedstawionym artykule metoda badawcza dostarcza informacji na temat zmian struktury materiału wywołanych deformacją trwałą.
3
Content available The Impact of Damage in Anneling Inconel 718 on Hardness Measured by the Vickers Method
Malicki M., Gadalińska E., Chmiel M.
Fatigue of Aircraft Structures
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2016
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Iss. 8
92--96
EN
In the previous work [1] it was shown that strain hardening had considerable impact on the hardness of Inconel 718. In order to verify the weakening of the material associated with the damage mechanism in the tested material, the hardness tests were performed on the stretched specimen which was subsequently heat treated. The tests revealed that, after heat treatment, the measured hardness was reduced with an increasing degree of the plastic deformation present prior to heat treatment.
4
Content available Evaluation of Damage Degree of Inconel 718 using Nondestructive Indicators of Damage
Krysztofik J.
Fatigue of Aircraft Structures
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2016
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Iss. 8
55--64
EN
This paper presents the results of the quantitative evaluation of the degree of damage caused by plastic strain accumulated in static tensile tests and creep tests. To detect changes in the structure of the material and in order to determine the degradation of the materials, nondestructive methods were used, namely the ultrasonic and eddy current methods. In ultrasonic testing, attenuation and acoustic birefringence were used as damage indicators. In the case of the eddy current method, changes in the phase angle of impedance were observed in the material. The material tested was Inconel 718 alloy. Inconel alloys are often find application in extreme working conditions including in the power engineering industry, aviation and aerospace. A new type of specimen with the variable cross-sectional area of the measuring part was used in the tests. This allowed researchers to obtain a continuous distribution of plastic strain and enabled analysis of the material with respect to different damage degrees. The correlation between the degree of damage, expressed by the measure of deformation, and the value of nondestructive indicators was determined. On the basis of it, the dependence indicating the ability to nondestructive evaluation of the degradation degree of the material, subjected to loads exceeding the yield limit was obtained.
5
Content available The Impact of Damage in Inconel 718 on Hardness Measured by the Vickers Method
Malicki M., Madejski B.
Fatigue of Aircraft Structures
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2015
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Iss. 7
69--79
EN
To prevent failure of machine components it is necessary to measure material damage generated in a component throughout its entire lifetime. Damage can be quantified by means of damage parameters. This paper considers the usefulness of hardness measurements to evaluate damage parameter in Inconel 718. Vickers hardness tests were performed on a specimen with a variable cross section area after tensile testing. The specimen’s geometry enabled the evaluation of damage parameter in respect of hardness measurements made on one individual specimen.
6
Content available The Application of Acoustic Anisotropy to Evaluation of Material Properties
Krysztofik J., Manaj W., Socha G.
Fatigue of Aircraft Structures
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2015
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Iss. 7
5--11
EN
Structural properties of materials change under stress, temperature and work environment. These changes are generally unfavorable. They cause a reduction in strength of materials. This has an impact on the safety and service life of machines and constructions. In the chemical and petrochemical industry the destruction of a structure can be activated by chemical substances. In the energy industry, a key element in assisting the destruction is temperature. In aviation, the typical cause of damage is the process of fatigue. Regardless of the differences regarding/concerning the mechanisms of degradation, typical of the sectors of industry, the end result is the emergence of microvoids and microcracks in the material. In the final phase of the process, dominant cracks are formed. The term of measure of material damage, introduced by Kachanov and Rabotnow, can be effectively used also when considering the impact of microdamages on measurable macroscopic acoustic quantities. A damage parameter proposed by Johnson allows to correlate changes in acoustic birefringence of the material with the parameter describing the degree of damage. In this article the authors presented the nondestructive tests results concerning Inconel 718 alloy subjected to damage caused by plastic deformation. This paper focuses on the evaluation of acoustic properties in relation to the degradation of the materials tested.
7
Content available Finite element model updating of reinforced concrete beams with honeycomb damage
Ismail Z.
Archives of Civil Engineering
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2012
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Vol. 58, nr 2
135-151
EN
A method of detecting honeycombing damage in a reinforced concrete beam using the finite element model updating technique was proposed. A control beam and two finite element models representing different severity of damage were constructed using available software and the defect parameters were updated. Analyses were performed on the finite element models to approximate the modal parameters. A datum and a control finite element model to match the datum test beams with honeycombs were prepared. Results from the finite element model were corrected by updating the Young’s modulus and the damage parameters. There was a loss of stiffness of 3% for one case, and a loss of 7% for another. The more severe the damage, the higher the loss of stiffness. There was no significant loss of stiffness by doubling the volume of the honeycombs.
8
Content available remote Methods of Material Parameters Identification for Isotropic Damage in Viscoplastic Flow Conditions
Kłosowski P., Pyrzowski Ł., Woźnica K.
Machine Dynamics Problems
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2008
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Vol. 32, No. 3
44-50
EN
The paper presents three methods of damage parameters identification in viscous flow conditions. Constitutive relations including damage are used according to the Chaboche and Lemaitre concept. The authors propose also their own modifications of identification algorithm. All algorithms are compared in the identification process for aluminum alloys.
9
Content available Statistical damage mechanics - constitutive relations
Rinaldi A., Krajcinovic D., Mastilovic S.
Journal of Theoretical and Applied Mechanics
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2006
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Vol. 44 nr 3
585-602
EN
The statistical damage model presented by the authors in the previous paper of this series is used to formulate analytical constitutive relations for the hardening and softening phases of two-dimensional lattices. A proper definition of the damage parameter for the softening is introduced. The results confirm that the analytical model can be used for the study of the softening phase and failure. This research offers a seminal basis for Damage Tolerance Principles technology standards of the commercial airplane industry.
PL
Statystyczny model uszkodzenia, przedstawiony przez autorów w innej pracy, zastosowano tu do sformułowania analitycznych związków konstytutywnych w zakresie wzmocnienia i osłabienia dla dwuwymiarowych modeli sieciowych. Wprowadzono odpowiednią definicję parametru uszkodzenia w zakresie osłabienia. Uzyskane wyniki potwierdzają, że wprowadzony model analityczny można stosować do badania osłabienia i zniszczenia materiałów. Praca stanowić może podstawę do ustalenia norm technicznych uszkodzenia stosowanych w przemyśle lotniczym.
10
Content available remote Mesoscopic theory of microcracks
Papenfuss C., Van P., Muschik W.
Archives of Mechanics
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2003
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Vol. 55, nr 5-6
481-499
EN
The mesoscopic concept is a way to deal with complex materials with an internal structure within continuum mechanics. It consists of extending the domain of the balance equations by mesoscopic variables and of introducing a local distribution function of these variables as a statistical element. In our case microcracks are modelled as penny-shaped and are completely characterized by their diameter and the unit normal to the crack surface. Two examples of crack dynamics are given as well as a possible definition of a damage parameter. Orientational order parameters (fabric-alignment tensors) are defined and balance-like dynamic equations for them are derived.
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