Instytut Podstawowych Problemów Techniki

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The paper presents the modeling of transmission of the ultrasonic plane wave through an uniform liquid layer. The considered sources of the ultrasonic wave were normal (straight) beam longitudinal wave probes and angle beam sheer waves probes commonly used in non-destructive testing. Coupling losses (CL) introduced by the presence of the coupling layer are discussed and determined applying the numerical procedure. The modeling applies to both monochromatic waves and short ultrasonic pulses with a specified frequency bandwidth. Model implementation and validation was performed using a specialized software. The predictions of the model were confirmed by coupling losses measurements for a normal beam longitudinal wave probe with a delay line made of polymethyl methacrylate (PMMA). The developed model can be useful in designing ultrasonic probes for high-speed rail track inspections, especially for establishing the optimal thickness of the water coupling layer and estimation of coupling losses, due to inevitable changes of the water gap during mobile rail inspection.

Słowa kluczowe:

non-destructive testing, ultrasonic examination, plane wave propagation

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Symulacje komputerowe odgrywają coraz większą rolę w planowaniu, przygotowaniu oraz interpretacji badań ultradźwiękowych. W artykule opisano podstawowe założenia teoretyczne oraz funkcjonalności programu SymUT rozwijanego w pracowni badań nieniszczących IPPT PAN. W celu ilustracji możliwości programu pokazano proste przykłady jego zastosowania do obliczania rozkładów pola ultradźwiękowego głowic ultradźwiękowych oraz obwiedni echa wad modelowych. Opisano zasady wykorzystania programu do projektowania głowic ultradźwiękowych oraz przygotowania procedur badawczych
Computer simulations are playing an increasingly important role in planning, preparation and interpretation of ultrasonic testing. The article describes the basic theoretical assumptions and functionalities of the SymUT software developed in the non-destructive testing laboratory of IPPT PAN. In order to illustrate its capabilities, simple examples of its use for calculation of the ultrasonic field of ultrasonic probes as well as the echo envelopes from model defects are shown. The principles of using the program for designing of ultrasonic probes and preparing testing procedures are described

Słowa kluczowe:

badania ultradźwiękowe, defektoskopia ultradźwiękowa, wiązka ultradźwiękowa, wady materiałowe, symulacje badań ultradźwiękowych, ultrasonic testing, ultrasonic flaw detection, ultrasonic beam, material defects, ultrasonic testing simulations, radar testing, electromagnetic testing

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The paper presents an investigation of the railhead steel R260. Brinell hardness was measured, spherical microindentation tests were performed and the microstructure was analysed using optical microscopy and SEM images. Fatigue damage in various near-surface regions of the railhead was estimated on the basis of local deterioration of elastic modulus and the development of plastic work in cyclic microindentation tests. There is a clear difference in hardness and fatigue damage between the used and the virgin regions of the railhead. The Brinell hardness and ultrasonic measurements show a change in material properties due to rail manufacturing process.

Słowa kluczowe:

Fatigue damage, Microindentation, Brinell hardness, Ultrasonic measurements, Railhead

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This paper aims to present the details of isotactic polypropylene (it-PP) films with a cellular structure (air-cavities) dedicated to pressure sensors. The polymer composites (thin films enriched with 5 and 10 wt% of mineral fillers as Sillikolloid P 87 and glass beads) should exhibit suitable structural elasticity within specific stress ranges. After the deformation force is removed, the sensor material must completely restore its original shape and size.

Słowa kluczowe:

polymer air-cavity films, electret materials, elastic modulus C33, piezoelectricity, contact ultrasonic spectroscopy

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In recent decades, several novel Ti alloys have been developed in order to produce improved alternatives to the conventional alloys used in the biomedical industry such as commercially pure titanium or dual phase (alpha and beta) Ti alloys. Gum Metal with the non-toxic composition Ti–36Nb–2Ta–3Zr–0.3O (wt. %) is a relatively new alloy which belongs to the group of metastable beta Ti alloys. In this work, Gum Metal has been assessed in terms of its mechanical properties, corrosion resistance and cell culture response. The performance of Gum Metal was contrasted with that of Ti–6Al–4V ELI (extra-low interstitial) which is commonly used as a material for implants. The advantageous mechanical characteristics of Gum Metal, e.g. a relatively low Young's modulus (below 70 GPa), high strength (over 1000 MPa) and a large range of reversible deformation, that are important in the context of potential implant applications, were confirmed. Moreover, the results of short- and long-term electrochemical characterization of Gum Metal showed high corrosion resistance in Ringer's solution with varied pH. The corrosion resistance of Gum Metal was best in a weak acid environment. Potentiodynamic polarization studies revealed that Gum Metal is significantly less susceptible to pitting corrosion compared to Ti–6Al–4V ELI. The oxide layer on the Gum Metal surface was stable up to 8.5 V. Prior to cell culture, the surface conditions of the samples, such as nanohardness, roughness and chemical composition, were analyzed. Evaluation of the in vitro biocompatibility of the alloys was performed by cell attachment and spreading analysis after incubation for 48 h. Increased in vitro MC3T3-E1 osteoblast viability and proliferation on the Gum Metal samples was observed. Gum Metal presented excellent properties making it a suitable candidate for biomedical applications.

Słowa kluczowe:

Gum Metal, mechanical behavior, in vitro corrosion resistance, in vitro biocompatibility, implant applications

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In the paper the calculation of ultrasonic field generated by the transmitting transducer and the energy of the beam returning after the reflection at the defect in the rail volume is presented. The focus of the authors is directed on the specific transducer - defect configurations where the common methods of determination of ultrasonic beam trajectory fails. To solve this problem the refraction effexts are studied and its impact is calculated.

Słowa kluczowe:

non-destructive testing, rolling contact fatigue damage, ultrasound

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The mechanical anisotropy of a multifunctional titanium alloy, Gum Metal, is investigated in this paper. The structural characterisation showed a strong <110> texture for Gum Metal, that is a result of the cold-swaging process applied during its manufacture. Gum Metal was treated as a transversally isotropic solid because of this texture. A significant difference from Young's moduli of the alloy was detected from the ultrasonic measurement of parallel and perpendicular directions to the alloy swaging direction. Samples of Gum Metal cubes were compressed in two different orientations. During the deformation process, two perpendicular walls of each sample were monitored by two visible range cameras for further two-dimensional digital image correlation analysis, this confirmed a strong plastic anisotropy in Gum Metal.

Słowa kluczowe:

gum metal, compression, mechanical anisotropy, digital image correlation, ultrasonic measurement, texture, titanium alloy, full-field deformation measurement

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The article presents the hybrid ultrasonic-neural assessment of the compressive strength of low-strength concrete screeds modified using high volume of mineral dusts sourced from industrial wastes. Quartz and quartz-feldspar dusts were selected to replace up to the 60% of the cement mass. The principal aim of this study is to carry out a systematic investigation of the effect of the addition of selected dusts on the compressive strength of such modified concrete screeds. The ultrasonic pulse velocity (UPV) technique was used for this purpose. After UPV analysis, about 13 different compositions were tested after 28 days for their compressive strengths (ranging from about 4 to 16 MPa). The relationship between the ultrasound velocity and compressive strength of the low-strength concrete screeds was found to be not acceptable. Finally, the artificial neural networks (ANNs) were employed to predict the compressive strength based on the composition of the concrete and UPV velocity. The obtained values of linear correlation coefficient (R) equal to 0.93, 0.91 and 0.94 respectively for learning, testing and validation phase were satisfactory for reliable evaluation of the compressive strength of environmentally friendly low-strength concrete screeds modified using high volume of waste quartz mineral dusts

Słowa kluczowe:

low-strength concrete screeds, industrial wastes, quartz mineral dusts, cement, ultrasonic pulse velocity, artificial neural network

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The paper presents an attempt of application of the acoustic birefringence coefficient for early stage degradation assessment of Inconel 718 nickel superalloy after short-term creep. It is shown that it can serve as a good damage sensitive parameter and, moreover, it can be well correlated with hardness variation.

Słowa kluczowe:

creep, nickel superalloy, microstructure, pre-deformation, hardness, acoustic birefringence

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W artykule opisano podstawy działania detektorów promieniowania stosowanych w cyfrowej radiografii bezpośredniej - DR. Scharakteryzowano rożne rodzaje paneli płaskich pod kątem ich przydatności w obszarze badań nieniszczących. W sposób bardziej szczegółowy omówiono panele płaskie z przemianą pośrednią oparte na matrycy a-Si z tranzystorami TFT, które wykazują obecnie największą przydatność do zastosowań w badaniach nieniszczących. Przeanalizowano najważniejsze parametry paneli płaskich w aspekcie ich zastosowań do badań złączy spawanych oraz innych wyrobów i elementów badanych dotychczas tradycyjną metodą radiograficzną

Słowa kluczowe:

radiografia cyfrowa, panele płaskie, radiografia bezpośrednia DR

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W artykule przedstawiona została możliwość lokalizacji delaminacji w płycie włóknisto-cementowej za pomocą specjalnie do tego celu skonstruowanego urządzenia wykorzystującego metodę ultradźwiękową i fale podłużne. Przeprowadzono badania na trzech rodzajach płyt. Stwierdzono, że proponowana metoda diagnostyczna umożliwia wykrywanie lokalnych nieciągłości, np. obszarów o obniżonej zwartości, czy delaminacji w płytach włóknisto-cementowych na obszarze średnicy wiązki metodą estymacji prędkości fali ultradźwiękowej. Zaletami metody są niewielkie wymiary urządzenia i krótki czas badania

Słowa kluczowe:

płyty włóknisto-cementowe, badania nieniszczące, ultradźwięki

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W artykule opisano podstawowe parametry głowic ultradźwiękowych zdefiniowane w PN-EN 12668-2 oraz ASTM E 1065-08. Opisano typowe uszkodzenia głowic ultradźwiękowych, występujące podczas eksploatacji oraz przeanalizowano ich wpływ na podstawowe parametry głowic ultradźwiękowych. W dalszej kolejności pokazano w jaki sposób parametry głowic mogą wpływać na istotne aspekty badań ultradźwiękowych, w szczególności na wykrywalność, interpretację oraz ocenę wskazań. Omawiane zagadnienia zilustrowano praktycznymi przykładami pokazującymi wpływ parametrów głowic na wyniki badań. Podkreślono znaczenie właściwego nadzoru nad stanem technicznym głowic ultradźwiękowych w całościowym systemie zapewnienia jakości badań ultradźwiękowych. Wskazano na konieczność prowadzenia okresowych kontroli głowic ultradźwiękowych podobnie jak ma to miejsce w odniesieniu do defektoskopów.

Słowa kluczowe:

głowice ultradźwiękowe, parametry głowic ultradźwiękowych, uszkodzenia głowic ultradźwiękowych, nadzór nad wyposażeniem badawczym, badania ultradźwiękowe

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Evolution of the density and the microstructure during hot pressing of NiAl/Al2O3 composite has been investigated in the present paper. In particular, the effect of the process parameters, viz. compacting pressure, sintering temperature and sintering time, on the evolution of the density of the intermetallic–ceramic composite has been studied. Evolution of the density has been related to microstructure changing. Porosity, pore structures and grains rearrangement have been analysed in microscopic observations.

Słowa kluczowe:

hot pressing, sintering, intermetallic–ceramic composite, density evolution, microstructure

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W pracy opisano podstawowe zasady ultradźwiękowych badań złączy spawanych techniką phased array zgodnie z wymaganiami PN-EN ISO 13588. Przedstawiono zakres i obszar zastosowania normy. Opisano typy skanów ultradźwiękowych zalecanych przez normę do badań spoin przy różnych poziomach techniki badania. Omówiono najważniejsze kalibracje systemów PA oraz inne aspekty ich przygotowania do badań spoin. Opisano metodykę wykonywania badań oraz oceny ich wyników wskazując na aspekty specyficzne dla zautomatyzowanej techniki phased array. Najważniejsze zagadnienia zilustrowano przykładami zaczerpniętymi z własnych badań oraz nadzorowanych wdrożeń. Wskazano na kluczowe znaczenie wprowadzonej normy dla upowszechnienia badań złączy spawanych techniką phased array.

Słowa kluczowe:

badania NDT, UT, technika phased array, badanie spoin

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The influence of hot pressing conditions on mechanical properties of nickel aluminide/alumina composite has been investigated in the present paper. In particular, effect of the process parameters, viz. compacting pressure, sintering temperature and sintering time on the evolution of density, elastic constants and tensile strength properties of the intermetallic-ceramic composite has been studied. Elastic constants, the Young's modulus and Poisson's ratio, have been evaluated using an ultrasonic testing method, and the tensile strength has been determined by a Brazilian-type splitting test. Microscopic observations of microstructure evolution complemented the experimental procedure. Experimental results have been confronted with theoretical models showing a good agreement between the data compared.

Słowa kluczowe:

Hot pressing, sintering, intermetallic-ceramic composite, elastic properties, Brazilian test, tensile strength, ultrasonic method

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It is commonly known that the properties of sintered materials are strongly related to technological conditions of the densification process. This paper shows the sintering behavior of a NiAl-Al2O3 composite, and its individual components sintered separately. Each kind of material was processed via the powder metallurgy route (hot pressing). The progress of sintering at different stages of the process was tested. Changes in the microstructure were examined using scanning and transmission electron microscopy. Metal-ceramics interface was clean and no additional phases were detected. Correlation between the microstructure, density, and mechanical properties of the sintered materials was analyzed. The values of elastic constants of NiAl/Al2O3 were close to intermetallic ones due to the volume content of the NiAl phase particularly at low densities, where small alumina particles had no impact on the composite’s stiffness. The influence of the external pressure of 30 MPa seemed crucial for obtaining satisfactory stiffness for three kinds of the studied materials which were characterized by a high dense microstructure with a low number of isolated spherical pores.

Słowa kluczowe:

ceramics, composites, electron, intermetallic, metallic matrix, microscopy, powder metallurgy, sintering, structural

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Thick-walled, main stream pipelines are key elements in many power and chemical plants. Operating for a long time in high temperature and subjected to internal pressure such pipes are subjected to creep resulting in material degradation and strain. The most common method of pipe state evaluation is pipe diameter monitoring. Usually such measurements are performed with micrometer gauge in locations where special “pips” were earlier installed. Other methods are also tested to monitor creep progress like various temperature-resistance strain gauges or eddy current sensors. The paper examines a new ultrasonic technique to evaluate thick-walled pipe diameter changes. Pipe diameter evaluation is based on time of flight of bulk ultrasonic waves propagating in circumferential direction along the polygon, reflecting on the pipe external surface only. Presented are results of experiments performed on 100 mm diameter pipe subjected to internal pressure to generate small diameter changes and on 273 mm diameter and 40 mm wall thickness pipe section. Measurements were performed with longitudinal, shear SV and shear SH waves. Described are advantages and disadvantages of various ultrasonic wave types for pipe diameter evaluation in practice. Discussed is the influence of residual stresses and temperature on accuracy of pipe diameter evaluation with proposed technique. Shear SV wave was chosen as the most easily applicable ultrasonic wave on thick-walled tubes.

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W pracy opisano podstawowe zasady ultradźwiękowych pomiarów modułów sprężystości w materiałach technicznych. Omówiono definicje stałych sprężystości dla materiałów o różnej symetrii, w szczególności dla materiałów ortotropowych, poprzecznie izotropowych oraz izotropowych. Opisano metodykę wyznaczania stałych sprężystości na podstawie pomiarów prędkości fal ultradźwiękowych dla materiałów o różnej symetrii. Wskazano na podstawowe wymagania dotyczące dokładnych pomiarów prędkości fal ultradźwiękowych w próbkach materiałów. Na zakończenie zaprezentowano przykład zastosowania omówionej metodyki pomiarowej do wyznaczenia zależności modułów sprężystości od zawartości fazy ceramicznej w kompozycie NiAl-Al2O3.

Słowa kluczowe:

badania ultradźwiękowe, pomiary prędkości fal, wyznaczanie modułów sprężystości, kompozyty metalowo-ceramiczne

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It is commonly known that the available non-destructive and mechanical methods of the Young modulus measurement yield different results. This paper presents comparison of the results of experimental determination and numerical modeling of the Young modulus of Cr–Al2O3–Re composites (MMC) processed by a powder metallurgical method (SPS). In the computational model a finite element analysis is combined with images of the real material microstructure obtained from micro-computed tomography (micro-CT). Experimental measurements were carried out by four testing methods: three-point bending, resonance frequency damping analysis (RFDA), ultrasonic pulse-echo technique, and scanning acoustic microscopy. The paper also addresses the issue which of the four experimental methods at hand gives results closest to the theoretical predictions of the micro-CT based FEM model.

Słowa kluczowe:

Finite element analysis (FEA), Micro-CT based FE model, Metal matrix composites, Elastic modulus, Mechanical and nondestructive techniques

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Słowa kluczowe:

badania ultradźwiękowe, pomiary współczynnika odbicia, ocena powierzchni kontaktu, pomiary chropowatości

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Badania ultradźwiękowe są obecnie podstawową metodą badań nieniszczących materiałów i struktur kompozytowych stosowanych w przemyśle lotniczym. W badaniach wykonywanych na etapie produkcji części i zespołów kompozytowych największe znaczenie mają zautomatyzowane techniki ultradźwiękowe oparte na metodzie przepuszczania, nazywane w branży lotniczej technikami C-scan. Pozwalają one w szybki i wydajny sposób badać zarówno laminaty monolityczne jak i struktury przekładkowe o różnej grubości i budowie dając w wyniku zobrazowania typu C badanych części. Podstawowe zasady działania systemów C-scan oraz przykłady ich praktycznego stosowania opisano w pracy.

Słowa kluczowe:

badania ultradźwiękowe, technika phased array, kompozyty węglowe, wady kompozytów

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Podstawową techniką stosowaną w badaniach laminatów węglowych metodą Phased Array jest kontaktowa metoda echa z ręcznym przesuwem głowicy. Pod względem mobilności i uniwersalności jest to technika zbliżona do konwencjonalnych badań defektoskopowych ze zobrazowaniem typu A, zapewniająca jednak pełny zapis wyników badania oraz znacznie większe możliwości ich analizy.

Słowa kluczowe:

badania ultradźwiękowe, technika phased array, wady laminatów węglowych, typy zobrazowań PA

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W pracy przedstawiono ultradźwiękowe badania naprężeń zmiennych w elementach konstrukcji stalowej. Opisano podstawy ultradźwiękowej metody pomiarów naprężeń, podano zależności z jakich na podstawie pomiarów czasu przejścia impulsów fal ultradźwiękowych obliczane są wartości naprężenia. Opisano wykorzystane w badaniach głowice ultradźwiękowe i układ pomiarowy. Pokazano wyniki badania zmian naprężeń w dwóch elementach kratowego mostu kolejowego – w podłużnicach i w wykrzyżowaniach kratowego dźwigara. Zarejestrowano zmiany naprężeń wywołane przejazdami pojazdów szynowych o różnych masach, poruszających się z różnymi prędkościami, w obu kierunkach. Badania prowadzone dwukanałową aparatur ą równocześnie w dwóch podłużnicach pozwoliły na wykrycie asymetrii obciążenia konstrukcji mostu podczas przejazdu pociągu towarowego. Porównano wyniki pomiarów uzyskanych technik ą ultradźwiękową z wynikami uzyskanymi technik ą tensometrii oporowej.

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This paper presents a new method for evaluating the temperature dependency of ultrasonic shear and longitudinal wave velocities. Results of such measurements allow the determination of elastic properties of solids, such as Young’s and shear moduli, for various temperatures. A short description of well-established techniques of ultrasonic measurements at high temperatures, such as laser and waveguide techniques, is given and their disadvantages listed. The main disadvantage, especially in the case of small samples with low heat capacity, is uneven temperature distribution in the sample volume caused by contact with a waveguide or through heat generated by the laser pulses. The proposed techniques enable velocity measurement of both longitudinal and shear waves in small samples while ensuring constant temperature in the whole sample volume. Measurements were performed using piezoelectric transducers pressed between two samples and generating and detecting ultrasonic waves propagating along the samples. Advantages of this measuring technique are: no need for couplant; the ability to measure small, easily machined samples; and the low cost of the experiment. The main disadvantage of the technique is a limited temperature range. The paper presents results of measurements performed on several samples cut from light alloy castings of various chemical compositions.

Słowa kluczowe:

ultrasonic, velocity, temperature, elastic constants

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Development of creep damage at elevated temperatures and structural degradation due to plastic deformation at room temperature were assessed using destructive and non-destructive methods in steels commonly applied in power plants (40HNMA, 13HMF and P91). As destructive methods the standard tension tests were carried out after every kind of prestraining. Subsequently, an evolution of the selected tension parameters was taken into account for damage identification. In order to assess a damage development during the creep and plastic deformation the tests for the steels were interrupted for a range of the selected strain magnitudes. The ultrasonic and magnetic techniques were used as the non-destructive methods for damage evaluation. The experimental programme also contained microscopic observations.

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This paper describes the application of acoustic birefringence measurement for evaluation of material degradation due to creep. The problem with ultrasonic investigation of the influence of creep-induced voids on ultrasonic wave velocities is the lack of samples containing well-defined voids. The only way to‘‘produce’’ damaged material with numerous voids is accelerated creep laboratory test or long-term service of material in high temperature and stress. To describe voids it is necessary to perform laborious metallographic examination of damaged material. Paper presents glass samples with artificial semi-flat voids created with laser engraving technique. Results of ultrasonic wave velocities and acoustic birefringence measurements in glass samples proved that laser engraving can be helpful for the experimental investigation of voids influence on solid acoustic properties.

Słowa kluczowe:

Ultrasound, Birefringence, Creep, Artificial voids

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Damage development due to creep under uniaxial tension at elevated temperatures is assessed using destructive and non-destructive methods in steels, commonly used in power plants or chemical industry, and in aluminium alloy used in aircrafts for responsible elements. The results obtained using two different destructive methods for assessments of damage development are critically discussed. In the first method the specimens of steel after different amounts of creep prestraining were stretched up to failure and variations of the selected tension parameters were taken into account for damage identification. In the second one, a damage degree was evaluated by studying variations of an initial yield locus position in the stress space and by determination of the yield loci dimensions. The ultrasonic investigations were selected as the non-destructive method for damage development evaluation.

Słowa kluczowe:

Creep, Damage, Mechanical Parameters, Ultrasound (US), Yield Surface

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Słowa kluczowe:

badania ultradźwiękowe, TOFD, badania spoin, poziomy akceptacji, PN-EN ISO 15626

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Słowa kluczowe:

badania ultradźwiękowe, technika phased array, badania spoin, PN-EN ISO 13588

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Słowa kluczowe:

badania radiograficzne, radiografia cyfrowa, technika CR, fotostymulowana luminescencja

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Słowa kluczowe:

badania radiograficzne, izotop Yb-169, badania spoin, PN-EN ISO 17636-1

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Słowa kluczowe:

badania ultradźwiękowe, badania degradacji stali, pełzanie, pomiary prędkości fal, pomiary tłumienia fal, dwójłomność akustyczna

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The paper is devoted to an analysis of creep damage at elevated temperatures and structural degradation due to plastic deformation at room temperature of selected steels commonly applied in power plants (40HNMA, 13HMF). The materials were tested in the as-received state, however, in the case of the 13HMF steel also after different periods of exploitation (76000h and 144000h at elevated temperature (813K) under internal pressure (14 bars)). Destructive and non-destructive testing methods were applied to assess material degradation. As destructive methods the standard tension tests were carried out after every kind of prestraining. Subsequently, an evolution of the selected tension parameters were taken into account for damage identification. In order to assess a damage development during the creep and plastic deformation the tests for both steels were interrupted for a range of the selected strain magnitudes. The ultrasonic and magnetic techniques were used as the non-destructive methods for damage evaluation. The last step of the experimental programme contained microscopic observations. A good correlation of mechanical and selected non-destructive parameters identifying damage was achieved for the tested steels. It gives very promising tool for degradation assessments appearing in pipelines at power stations.

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Słowa kluczowe:

Mechanical Anisotropy, Ti alloy, Gum Metal, Ultrasound Measurement, Digital Image Correlation

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Słowa kluczowe:

Gum Metal, EBSD, ultrasonic measurement

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Experimental investigation of mechanical anisotropy in a multifunctional beta titanium alloy Gum Metal under compression is reported. Non-destructive and destructive techniques were used to analyze unique mechanical behavior of the alloy. Structural characterization showed a strong <110> texture of Gum Metal, which is a result of cold-swaging applied during its fabrication [1]. Due to this kind of texture Gum Metal can be treated as transversally isotropic solid. Ultrasonic measurements determined elastic constants with high accuracy. A significant difference between Young's moduli of the alloy calculated for parallel and perpendicular directions to the alloy swaging direction was demonstrated. Compression of Gum Metal cube samples with two orientations was conducted on a testing machine. Two perpendicular walls of each sample were monitored by two visible range cameras during the deformation process for further 2-dimensional digital image correlation (DIC) analysis. Strong mechanical anisotropy of Gum Metal was confirmed by a detailed analysis of the stress vs. strain curves and strain distributions.

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Development of damage due to creep at elevated temperatures and fatigue at room temperature was assessed for power engineering steels using destructive and nondestructive methods. The experimental programme contained also microscopic observations to find feedback between macro and microscopic parameters

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