Grzegorz Socha, PhD, DSc


Doctoral thesis
1995Zmiany anizotropii plastycznej metali w czasie 
supervisor -- Prof. Lech Dietrich, PhD, DSc, IPPT PAN
518 
Recent publications
1.Krysztofik J., Kukla D., Manaj W., Socha G., Evaluation of damage degree of inconel 718 alloy with the use of non-destructive methods, Russian Journal of Nondestructive Testing, ISSN: 1061-8309, DOI: 10.1134/S1061830919040107, Vol.55, No.4, pp.299-307, 2019
Abstract:

The article presents results of the investigation of the quantitative evaluation of the degree of damage, described by the measure of accumulated plastic strain obtained in a static tensile test, using selected non-destructive techniques. Inconel 718 alloy was tested. The tests were conducted using a new type of specimens of variable cross-sectional area of measuring part. This provided a continuous distribution of plastic strain in the gage part of the specimen. The permanent deformation that varies along the sample axis enables an analysis of damage induced by a plastic deformation. The proposed method enables replacing the series of specimens by one sample. Degradation of the alloy corresponds with the changes of the electromagnetic properties of the material—the phase angle of the complex impedance of the eddy current, as well as with acoustics properties of material—acoustic birefringence of ultrasonic waves. It allows to determine the degree of damage of the material using noninvasive, non-destructive methods. Using the damage parameter proposed by Johnson it is possible to obtain the 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.

Keywords:

nondestructive testing, damage parameter, phase angle of eddy current, acoustic birefringence

Affiliations:
Krysztofik J.-other affiliation
Kukla D.-IPPT PAN
Manaj W.-Institute of Aviation (PL)
Socha G.-other affiliation
2.Kowalewski Z.L., Dietrich L., Socha G., Experimental investigation of thin brass sheets under tension-compression cyclic loading, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.53.3.757, Vol.53, No.3, pp.757-762, 2015
Abstract:

Strength and durability of thin-walled structures are usually calculated with the use of computer simulations. To perform such simulations using Finite Element Method, characteristics of a material subjected to monotonic tension or compression and tension-compression cyclic loading are necessary. Experimental determination of such kind of characteristics is usually performed on specimens cut out from a metal or composite thin sheet. Problems associated with testing on flat specimens under large deformation are discussed in this paper. A new design of fixture proposed by the authors for this kind of testing is shortly described. The results of investigations carried out on brass using the new fixture for flat specimens testing are also presented.

Keywords:

fixture, large deformations, tension-compression tests, thin metal sheet

Affiliations:
Kowalewski Z.L.-IPPT PAN
Dietrich L.-IPPT PAN
Socha G.-other affiliation
3.Krysztofik J., Kukla D., Socha G., Ocena stopnia uszkodzenia stopu Inconel 718 z zastosowaniem prądów wirowych, PRZEGLĄD SPAWALNICTWA, ISSN: 0033-2364, Vol.87, No.12, pp.36-38, 2015
Abstract:

Zaprezentowane wyniki wskazują na możliwość ilościowej oceny stopnia uszkodzenia, opisanego miarą skumulowanego odkształcenia plastycznego, uzyskanego w statycznej próbie rozciągania, z wykorzystaniem prądów wirowych. Badaniom poddano próbkę o zmiennym polu przekroju w całym zakresie części pomiarowej. Użycie próbki o takiej geometrii umożliwia uzyskanie pola deformacji, której wartość zmienia się wzdłuż osi próbki. Znajomość wartości odkształcenia trwałego w danym przekroju próbki w połączeniu z analizą struktury w tym miejscu pozwala na prześledzenie ewolucji uszkodzenia struktury materiału wywołanej jego deformacją trwałą. Na takiej próbce, poddanej próbie rozciągania, wykonano profil zmian kąta fazowego sygnału prądowirowego w kolejnych obszarach o zmiennym stopniu uszkodzenia. Dokonując korelacji pomiędzy stopniem uszkodzenia wyrażonym miarą parametru uszkodzenia oraz wartością mierzonego kąta fazowego, determinowaną lokalnymi zmianami przewodności elektrycznej i przenikalności magnetycznej uzyskano zależność wskazującą na możliwość nieniszczącej oceny stopnia degradacji materiału poddanego obciążeniom przekraczającym wartość granicy plastyczności.

Keywords:

ocena uszkodzenia, lokalne pomiary odkształcenia, prądy wirowe

Affiliations:
Krysztofik J.-other affiliation
Kukla D.-IPPT PAN
Socha G.-other affiliation
4.Socha G., Dietrich L., A fatigue damage indicator parameter for P91 chromium-molybdenum alloy steel and fatigue pre-damaged P54T carbon steel, FATIGUE AND FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, ISSN: 8756-758X, DOI: 10.1111/ffe.12104, Vol.37, pp.195-205, 2014
Abstract:

Two grades of structural steel were subjected to fully reversible, constant stress amplitude cyclic loading. The local strain response of the material was measured and recorded during the test, with the applied testing technique enabling the monitoring of hysteresis loop variation for the narrowest cross-section of the hourglass specimen. Changes in hysteresis loop width, representing the local inelastic response of the material, were recorded in order to monitor the density of structural imperfections. Material ratcheting behaviour was observed as changes in the mean strain for selected load cycles. Ratcheting was attributed to local deformation of the material in the vicinity of imperfections such as voids or inclusions, as well as deformation induced by the propagation of microcracks. Definitions of a damage indicator parameter and damage parameter were proposed. The fatigue behaviour of the two investigated grades of steel was finally illustrated in the form of damage curves for different stress amplitudes and for undamaged and fatigue pre-damaged material.

Affiliations:
Socha G.-other affiliation
Dietrich L.-IPPT PAN
5.Dietrich L., Socha G., Kowalewski Z.L., Anti-buckling Fixture for Large Deformation Tension–Compression Cyclic Loading of Thin Metal Sheets, STRAIN, ISSN: 0039-2103, DOI: 10.1111/str.12078, Vol.50, pp.174-183, 2014
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.

Keywords:

buckling, cyclic loading, fixture, thin sheets

Affiliations:
Dietrich L.-IPPT PAN
Socha G.-other affiliation
Kowalewski Z.L.-IPPT PAN
6.Dietrich L., Socha G., Accumulation of Damage in A336 GR5 Structural Steel Subject to Complex Stress Loading, STRAIN, ISSN: 0039-2103, Vol.48, pp.279-285, 2012
Abstract:

Changes in the mechanical characteristics of the structural steel because of fatigue damage accumulation are investigated in this article. Cyclic loading was performed in a complex stress state. Tubular specimens were loaded by axial force and torque, with loading performed along proportional and non-proportional paths in the strain space. Material characteristics in the form of the stress–strain curve and yield surface were determined in the ‘as received’ state and after cyclic loading. It was found that accumulation of the fatigue damage because of cyclic loading in a complex stress state along proportional and non-proportional paths in the strain space is manifested by the increase in inelastic response. The rate of damage was found to be higher for non-proportional (circular) loading paths than that for proportional loading with the same strain amplitude.

Keywords:

complex stress state, damage accumulation, fatigue, strain space, yield surface

Affiliations:
Dietrich L.-IPPT PAN
Socha G.-other affiliation
7.Socha G., Zmiany anizotropii plastycznej metali w czasie (Praca doktorska), Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.21, pp.1-111, 1995
8.Kowalewski Z.L., Śliwowski M., Socha G., Wpływ różnokierunkowej deformacji cyklicznej na ewolucję powierzchni plastyczności stali 18G2A, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.25, pp.1-50, 1994
9.Dietrich L., Kiryk R., Socha G., Śliwowski M., Identyfikacja plastycznej anizotropii stopu aluminium, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.26, pp.1-49, 1994
10.Dietrich L., Kowalewski Z.L., Śliwowski M., Socha G., Charakterystyka cyklicznych właściwości stopu aluminium na podstawie badań w złożonym stanie naprężenia, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.29, pp.1-60, 1994
11.Kowalewski Z.L., Śliwowski M., Socha G., Określanie cyklicznych właściwości stali 18G2A na podstawie krzywych szkieletowych dla płaskiego stanu naprężenia, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.32, pp.1-53, 1994

Conference papers
1.Libura T., Kowalewski Z.L., Dietrich L., Socha G., Anti-buckling system for flat specimens investigations under cyclic tension-compression, Materials Today: Proceedings, ISSN: 2214-7853, DOI: 10.1016/j.matpr.2016.03.045, No.3, pp.1045-1050, 2016
Abstract:

Modern automobile and airplane structures made of sheet metals or composites require usage of thinner and stronger materials. On the other hand, manufacturers are trying to reduce production costs by shortening the fabrication processes and by application of computed simulation for forming operation. Therefore, it is necessary to better understand and more accurately investigate deformation behaviour of sheet alloys. Testing of flat specimens under compression and cyclic tension-compression within large deformation procures a lot of problems. One of them is the buckling phenomenon. A new version of the device mounted in a standard testing machine was developed and geometry of the specimen for validation of the device was proposed. Specimens of DP690 steel with nominal thickness equal to 1.6 mm were investigated at ambient temperature. Tension-compression cyclic tests within a strain range ± 0.04 were executed starting in tension direction. It is shown that the results are repeatable.

Keywords:

Buckling, cyclic loading, fixture, thin sheets

Affiliations:
Libura T.-IPPT PAN
Kowalewski Z.L.-IPPT PAN
Dietrich L.-IPPT PAN
Socha G.-other affiliation
2.Kowalewski Z.L., Dietrich L., Socha G., Experimental investigation of thin metal sheets under tension-compression cyclic loading, ACAM 8, 8th Australasian Congress on Applied. Mechanics, 2014-11-23/11-26, Melbourne (AU), pp.1-10, 2014
Abstract:

Strength and durability of thin-walled structures are usually calculated with the use of computer simulations. To perform such simulations using Finite Element Method the characteristics of a material subjected to monotonic tension/or compression and tension-compression cyclic loading are necessary for example. Experimental determination of such kind of characteristics is usually performed on specimens cut out from metal or composite thin sheet. Problems associated with material testing on flat specimens under large deformation are discussed in detail by this paper. In the first part, a short review of the antibuckling fixtures developed up to now is given. Several representative solutions including the applied design are discussed, with special emphasis on the technique limitations. In the second part, the results of investigations carried out on steel and brass using the new fixture for the flat specimens testing are presented.

Keywords:

fixture, large deformations, tension-compression tests, thin metal sheet

Affiliations:
Kowalewski Z.L.-IPPT PAN
Dietrich L.-IPPT PAN
Socha G.-other affiliation

Conference abstracts
1.Kowalewski Z.L., Dietrich L., Socha G., On the experimental techniques for thin sheets testing at large deformations, 9th German-Greek-Polish Symposium Recent Advances in Mechanics, 2016-09-04/09-09, Kolympari, Chania (GR), pp.41-42, 2016
Abstract:

Problems associated with material testing on flat specimens under large deformation due to compression or cyclic tension-compression are discussed. A short review of the anti-buckling fixtures developed up to now is given with special emphasis on the new fixture elaborated at the Institute of Fundamental Technological Research in Poland.

Affiliations:
Kowalewski Z.L.-IPPT PAN
Dietrich L.-IPPT PAN
Socha G.-other affiliation
2.Kowalewski Z.L., Socha G., Dietrich L., Libura T., Thin sheet of brass testing under cyclic tension - compression using novel anti-buckling fixture, DAS 2015, 32nd Danubia-Adria-Symposium on Advances in Experimental Mechanics, 2015-09-22/09-25, Smokovec (SK), Vol.1, pp.128-129, 2015
3.Kowalewski Z.L., Dietrich L., Socha G., Anti-buckling system for flat specimens investigation under cyclic tension-compression, Plasticity 2015, 21st International Symposium on Plasticity and its Current Applications, 2015-01-04/01-09, Montego Bay (JM), pp.127-129, 2015
Abstract:

Problems associated with material testing on flat specimens under large deformation are discussed in this paper. An extensive review of the anti - buckling fixtures developed up to now is given first, and then detailed description of the proposed design is presented. Finally, the results of cyclic tests carried out using new fixture are studied

Affiliations:
Kowalewski Z.L.-IPPT PAN
Dietrich L.-IPPT PAN
Socha G.-other affiliation
4.Socha G., Dietrich L., Evolution of damage for p91 steel under cyclic load, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.169-170, 2014

Patents
Filing No./Date
Filing Publication
Autor(s)
Title
Protection Area, Applicant Name
Patent Number
Date of Grant
pdf
398245
2012-02-27
BUP 18/2013
2013-09-02
Dietrich L., Kowalewski Z.L., Socha G.
Układ do badań wytrzymałościowych cienkich elementów konstrukcyjnych, zwłaszcza blach
PL, Instytut Podstawowych Problemów Techniki PAN
231688
WUP 03/2019
2019-03-29



359944
2003-04-30
BUP 22/2004
2004-11-04
Socha G., Dietrich L.
Samocentrujący uchwyt do mocowania przedmiotów zaopatrzonych we współosiowe gwintowane końcówki
PL, Instytut Podstawowych Problemów Techniki PAN
199326
WUP 09/2008
2008-09-30
359943
2003-04-30
BUP 22/2004
2004-11-02
Socha G., Dietrich L.
Sposób określania stopnia uszkodzenia materiału konstrukcyjnego wywołanego obciążeniami eksploatacyjnymi
PL, Instytut Podstawowych Problemów Techniki PAN
204561
WUP 01/2010
2010-01-29