Ladislav Pesek

• Professor
• Technical University of Košice

The work is focused on experimental research of deformation characteristics on three grades of hot-dip galvanized steels for the automotive industry. Deformation maps were obtained using the DIC (Digital Image Correlation) method. The map documents the development of longitudinal and transverse deformations under tensile stress. In addition to unia...

The purpose of the present paper is the diagnostic method of the steady state tearing tests in thin steel sheets. The camera-based contactless system was used in the experimental research. The MATLAB software was used for the processing of real-time images. The data collected in the experiments were used to establish the R-curves in terms of the CT...

Depth-sensing indentation (DSI) is used in this work to determine the change of local mechanical properties by annealing of hot-dip galvanized IF steel sheets. The influence of annealing conditions (temperature and time) on: (i) coating composition; (ii) local mechanical properties and (iii) roughness of the coating surface was quantified. Annealin...

Nanomechanical testing using depth sensing indentation (DSI) provides a straightforward solution for quantitatively characterizing each of phases in microstructure because it is very powerful technique for characterization of materials in small volumes. Measuring the local properties (indentation hardness H IT , indentation modulus E IT , indentati...

The stable crack growth in thin steel sheets is the topic of this paper. The crack opening was observed using a videoextensometry system, allowing the crack extension determination. JR-curve and δR-curve were established from obtained data. The ductile tearing properties of different thin sheets of steel were determined, including the impact of the...

This paper focused on the stable crack growth in laser welds of thin automotive steel sheets. The stable crack growth was monitored using the contactless measurement—the videoextensometry technique on compact tension (CT) specimens with parallel and perpendicular notch orientation to the longitudinal weld axis. Specimens with electro-spark notches...

Nanomechanical testing using depth sensing indentation (DSI) provides a straightforward solution for characterizing of mechanical properties (indentation hardness H,T, Young's modulus E,T, indentation energy: total Wtotai, elastic Weiast, plastic Wpiast) of homogeneous (bulk) materials. However, real materials such as multi-phase steels are heterog...

The Oliver–Pharr method has extensively been adopted for measuring hardness and Young’s modulus by indentation techniques. However, the method assumes that the contact periphery sinks in, which limits the applicability to the materials pile-up [1]. In this work, we characterize the pile-up (shape and height) in steel sheets with different mechanica...

The main idea of this work is using a physical model to prepare a virtual material with required properties. The model is based on the relationship between the microstructure and mechanical properties. The macroscopic (global) mechanical properties of steel are highly dependent upon microstructure, crystallographic orientation of grains, distributi...

The macroscopic mechanical properties of steel are highly dependent upon microstructure, crystallographic orientation of grains and distribution of each phase present, etc. Nanomechanical testing using depth sensing indentation (DSI) provides a straightforward solution for quantitatively characterizing each of phases in microstructure because it is...

The results of diagnostics and analysis of an industrial hall located on the premises of a thermal power plant severely damaged by fire are presented in the paper. The comprehensive failure-related diagnostics, non-destructive and destructive tests of steel and concrete materials, geodetic surveying of selected structural members, numerical modelli...

The Oliver–Pharr method has extensively been adopted for measuring hardness and elastic modulus by indentation techniques. However, the method assumes that the contact periphery sinks in, which limits the applicability to the materials pile-up [1]. This study proposes an improved methodology to calculate the real mechanical characteristics of indiv...

The contribution deals with estimation of tensile properties and fatigue behavior based on hardness measurement. First of all the database of tensile and fatigue properties vs. hardness data was created for a group of steels, from literature survey and performed experiments. Tensile strength, yield strength, ductility and parameters of Ludwig-Hollo...

Using the videoextensometry and UCI – hardness for monitoring of automotive steel sheets Materials Engineering -Materiálové inžinierstvo 18 (2011) 93-96 Resume The paper deals with examination of relation between the hardness and the size of plastic zone during the tensile loading. UCI (Ultrasonic Contact Impedance) micro-hardness method was used f...

This paper deals with description of properties of selected natural materials mainly theirs shelter function. The investigated materials are horsetail and walnut shell. Both natural materials have porous shell/tubular structure. Walnut shell provides natural shield cover for fruit with gradient distribution of porosity and membrane function. In cas...

The macroscopic mechanical properties of steel are highly dependent upon microstructure, morphology, and distribution of each phase present. Nanomechanical testing (Depth sensing indentation) provides a straightforward solution for quantitatively characterizing each of these phases because it is very powerful technique for characterization of mater...

Dual phase (DP), interstitial free (IF) and advanced high strength low alloy steel (HSLA)sheets have been successfully used for different components of car body. DP and HSLA are used ascrash resistant and IF as cover or “skin” of car body. The development of new vehicles nowadays isbeing driven by the need to simultaneously reduce mass and increase...

The work experimentally analyses the effect of various factors on hardness measured values on thin steel sheets using Ultrasonic Contact Impedance (UCI) technique. The conditions experimentally used are compared with that according the ASTM A 1038-08 standard. UCI is an experimental technique for indirect hardness measurement. The equipment uses a...

Currently only few methods exist for thin steel sheet testing, especially based on fracture mechanics concept. Charpy impact test is one of the most used methods for testing notch toughness and fracture behaviors because of the simplicity and the other advantages [1]. This article deals with toughness testing of automotive ultra high strength steel...

The paper deals with an experimental determination of the stretch zone dimensions in the notch tip in thin steel sheets. The stretch zone dimensions depend on steel grade, on the rolling direction as well as on the loading rate. Stretch zones were observed and measured on three steel grades. Fracture area and stretch zones were analysed by SEM. Sta...

Mechanical properties by depth sensing indentation are derived from the indentation load-displacement data used a micromechanical model developed by Oliver & Pharr (O&P). However, O&P analysis on the indentation unloading curve is developed from a purely elastic contact mechanics (sink-in). The applicability of O&P analysis is limited by the materi...

The contribution deals with prediction of tensile properties based on measurement of microhardness. First of all, the database of stress - strain, σ-ε vs. hardness data was created. Tensile strength, yield strength, ductility and parameters of Ludwik-Hollomon equation σ = σ0+kεn ; k, n were correlated with hardness. Various hardness values found in...

The paper presents the results of strain measurement using two methods: videoextensometry (ME46) and digital image correlation (DIC)-ARAMIS. ME46 - allows measuring and monitoring the major and minor strain on a planar surface of a loaded object [1]. Experimental equipment uses a CCD camera for monitoring the process. The software calculates the di...

The article is focused on local stress simulation as well as local deformation analysis in a cylinder of piston combustion engine. Design of the exhaust pipe system has to fulfill special requirements with regard to the combined loading due to high pressures and temperatures. There is a special role of the exhaust pipe barrier, which is situated in...

L. Knapcikov(a), J. Husar(a), M. Herzog(b), and L. Pesek(c) ((a)Department of Manufacturing Management, Faculty of Manufacturing Technologies of TU of Kosice, (TU)-T-b of Applied Sciences, Wildau, Germany, (c)Department of Materials Science, Faculty of Metallurgy, TU of Kosice, Slovak Republic): Testing of New Composite Materials Based on Fabric fr...

P. Gavendova(a), R. Ctvrtlik(b), F. Kovac(a), L. Pesek(c), and I. Petryshynets(a) ((a) Institute of Materials Research, Slovak Academy of Sciences, Kosice, Slovakia, (b) Palacky University, Faculty of Science, Regional Centre of Advanced Technologies and Materials, Joint laboratory of Optics of Palacky University and Institute of Physics of Academy...

The study analyses the critical positions in the combustion engine pistons produced by gravity casting of near eutectic aluminium-silicon alloys. The local strength in various positions was calculated from secondary dendrite arm spacing in the microstructure, the real local load was calculated via finite element analysis. The global strength approa...

Strain hardening characteristics of two rolled deep drawing quality (DDQ) steels, namely, interstitial free (IF) and aluminium killed (AK), have been studied with and without the presence of geometric constraints at room temperature. Strain hardening exponent and rate are investigated for plain, centre holed and double notched sheet specimens for b...

In this study, the local mechanical properties: indentation modulus E<sub align="right"> IT </sub> and indentation hardness H<sub align="right"> IT </sub> were experimentally investigated on two matrix-particle systems using depth-sensing indentation technique with a sharp Vickers and Berkovich indenter. The continuous stiffness measurement (CSM) t...

This paper deals with determination of the crack growth resistance of automotive steel sheets. Stable crack growth was monitored with videoextensometry techniques on CT (Compact Tension) specimens with various orientation of notch (parallel to rolling direction, perpendicular to rolling direction). Specimens of three steel grades with a fatigue pre...

Videoextensometry is a new experimental technique for non contact strain measurement, which enables measuring of longitudinal and transversal strain components on a planar surface of a loaded object. Experimental equipment uses a CCD camera (640 × 480 pixels) for monitoring the process on a surface area of 20 × 10 mm2. The special software calculat...

The paper deals with indentation measurements of hardness of the intermetallic phases in the galvanneal coatings. Galvannealed IF-HS steel sheets are presently the subject of interest in automotive as well as steel industry for higher corrosion resistance, and considerably higher strength with excellent formability. These coatings may contain one o...

Videoextensometry is a new experimental technique for non contact strain measurement, which enables measuring of longitudinal and transversal strain components on a planar surface of a loaded object. Experimental equipment uses a CCD camera (640 x 480 pixels) for monitoring the process on a surface area of 20 x 10 mm(2). The special software calcul...

The contribution deals with influence of montmoril-lonite (MMT) nanoparticles on strength, hardness and deformation properties of composites with PP and PA matrix. The mechanical properties were determined (HIT, EIT) using the depth sensing indentation technique (DSI) and creep behavior of investigated materials was monitored in the means of DSI. N...

The contribution deals with determination of mechanical properties of TiC(N) particles embedded in steel matrix by depth sensing indentation. The system belongs to a hard particle in soft matrix system. It has been shown that this technique can be applied to measure properties of the particles. The influences affecting the accuracy of measurement w...

Two progressive methods were used for evaluation of indentation and deformation characteristics of laser welds. Depth sensing indentation techniques (DSI) is used for determination of local mechanical properties of laser welds. Mechanical properties such as indentation hardness (HIT), Martens hardness (HM), total indentation energy (W), elastic ind...

Two steel sheets used for deep drawing of the compressor cover were investigated using the videoextensometry technique for strain monitoring during tensile test. The material causing cracks during deep drawing has higher both yield stress and strength and lower ductility comparing with material without problems in technology. The strain hardening e...

The main goal of this paper is the determination of the size and shape of the plastic zone in thin steel sheets. The aim of experiments was to analyze the influence of the material and type of the initial crack on the dimensions of the plastic zone. The plastic zone size and shape is also predicted by measuring hardness (HV 1) along and across the...

The paper deals with examination of relation between the hardness and deformation εy. UCI hardness method was used for hardness measurements. Deformation was evaluated by non-contact extensometry - videoextensometry. The results present existence of the power relation between hardness and plastic deformation: HV = HVp+ kεa.

The contribution deals with influence of montmoril-lonite (MMT) nanoparticles on strength, hardness and deformation properties of composites with PP and PA matrix. The mechanical properties were determined (HIT, EIT) using the depth sensing indentation technique (DSI) and creep behavior of investigated materials was monitored in the means of DSI. N...

The aim of this paper is the determination of the true stress - true strain, σ - ε, curves by depth sensing indentation (DSI) on both aluminium (AA6063) and steel (St 52) using a spherical indentation. Hardness, H, indentation modulus, E', and a part of the indentation stress - strain, σ - ε, curve were determined using a spherical indenter with 60...

The contribution deals with the evaluation of the microhardness of powder particles and specification of the factors affecting measured results. This problem arouses up by Vickers microhardness HV0.01 measurements on two different powders, results of which showed large scattering from the average and give no possibility to identify the influence of...

This paper deals with the accuracy of the non-contact system for strain measurement. This measuring system allows the measurement of strains in two orthogonal directions simultaneously and in realtime. The aim of experiments was to analyze the factors affecting the accuracy of ME 46 videoextensometric system.

Purpose: The goal of this work was to investigate the influence of chemical composition and isothermal heating in order to determine the change of the mechanical properties of the metallic ribbons by depth sensing indentation technique. Design/methodology/approach: The amorphous metallic ribbons were manufactured by planar-flow-casting method. Inst...

Using a Depth Sensing Indentation technique (DSI), the Martens hardness HM, indentation modulus EIT and deformation work W for Al matrix and Al<sub align="right"> 4 </sub>C<sub align="right"> 3 </sub> particles have been measured. It has been shown that the hardness of Al<sub align="right"> 4 </sub>C<sub align="right"> 3 </sub> particles is 5–7 tim...

The paper presents mechanical properties of two kinds of Co-based and one Fe-based metallic ribbons by the depth sensing indentation (DSI) technique. Investigations were carried out on two kinds ternary alloy Co77Si11,5B11,5 and Fe78Si13B9 and multicomponent Co68Fe4Mo1Si13,5B13,5, which are so-called "zero-magnetostriction" materials. Metallic ribb...

Micro- and macro-hardness of the individual layers of an Al2O3 / Al2O3 + ZrO2 layered composite have been investigated. The indentation load size effect has been studied in a range of indentation load of 25 mN – 100 N using depth sensing indentation technique and conventional Vickers hardness testers. Fracture toughness values of the layers have be...

Using a depth sensing indentation (DSI) technique, the Martens hardness HM, indentation modulus EIT and deformation work W for Al matrix and Al4C3 particles have been measured on mechanically alloyed system Al–Al4C3. It has been shown that the hardness of Al4C3 particles (10–14 GPa) is 5–7 times higher than the hardness of matrix. Hard particles ab...

The failure strain and the mechanics of thinning of sheets of interstitial-free steel in two orientations are addressed. The investigation is confined to two situations, namely in plane samples and in samples containing geometrical constraints. Finite element analysis as well as experimental investigations is conducted under quasi-static loading co...

Deformation of the Al–Al4C3 system was analyzed by “in situ tensile test in SEM” and a model of fracture mechanism was suggested.It has been shown that during tensile deformation, the first cracks appeared due to decohesion of the matrix–particle interphase as a result of different physical properties of the matrix and the particles. The stress inc...

The effect of lead on productivity and health condition of Dominant hybrid layers in the 9th month of laying was observed for 45 d. Layers of the control group were fed complete mixed feed for layers. The 1 st experimental group received feed supplemented with lead at a level of 1000 mg.kg -1 mixed feed. The 2nd experimental group, in addition to t...

Using a depth sensing indentation (DSI) technique, the Martens hardness HM, indentation modulus EIT and deformation work W for Al matrix and Al4C3 particles have been measured on mechanical alloyed system Al-Al4C3. It has been shown that the hardness of Al4C3 particles (10-14 GPa) is 5-7 times higher than the hardness of the Al matrix. Hard particl...

The interaction between cyclic loading and the surrounding environment has to be taken into account especially at high temperature exposure. In atmospheric conditions fatigue and oxidation take place parallel. This results in a shorter crack initiatial period and enhanced crack propagation both in thermal cycling and isothermal conditions. In the p...

The interaction between cyclic loading and the surrounding environment has to be taken into account especially at high temperature exposure. In atmospheric conditions fatigue and oxidation take place paralelly. This results in a shorter crack initiation period and enhanced crack, propagation both in thermal cycling and isothermal conditions. In the...

In the present work the deformation of the Al-12Al4C3 system was analysed by "in-situ tensile test in SEM" and the model of fracture mechanism was suggested. It has been shown that during tensile strain the first cracks appeared due to decohesion of matrix-particle interphase. The further stress increase causes the cracks development into the speci...

The Young's modulus values of silicon nitride samples prepared with various composition and amount of additives were measured by microindentation and ultrasonic contact impedance methods and compared with the Young's moduli evaluated from four point bending load/displacement curves. Both methods were found to be reliable enough to determine the You...

SiAlONs are mostly taken for a low cost alternative for silicon nitride ceramics due to their simple processing. In spite of this, their properties in some aspects can be superior to the pure silicon nitride. SiAlON can be taken for silicon nitride with an extended lattice in which a part of the silicon is replaced by aluminium and a part of nitrog...

Based on creep tests of a two-phase titanium alloy a change of the value of the activation energy was revealed in temperature range of 450-475°C. This change was related to the change of the mechanism ruling of the creep deformation. Microscopical observations of the fractured samples showed that grain boundary sliding occurs on the original β grai...

The purpose of this work is to compare three fatigue precracking techniques for SENB specimens containing residual stresses. These are local compression, the use of a high R ‐ratio in the fatigue cycle and reverse bending. The possible effects of these techniques on the values of fracture toughness are assessed. The main conclusion is that local co...

The resistance of high yield stress microalloyed steel (Re = 814 MPa) against the stable crack growth by the R-curves method is assessed. The R-curves and the values J0.2/BL assessed by single specimen compliance method and the other by multiple specimen method were compared. The influence of side grooves on R-curves was investigated and the values...

The experiments were carried out on three alloys. VT3-1 was examined in the globular state and lamellar state. The semifinished products of VT6, VT20 and VT3-1 alloys were forged and heat treated. Mechanical properties at 20 and 500°C are given and creep characteristics (yield limit and creep strength) are presented. The lamellar states fail by the...

The effect of precipitation and particle strengthening on yield strength and fracture toughness was tested in two higher-strength microalloyed steels. A mathematical relationship is given to illustrate the dependence of fracture toughness on the mean distance of the incoherent precipitations.

The article deals with the relationship of a structure characterized by the ferrite grain size and the distance of lambda-precipitate particles on the one hand and the fracture toughness and the yield point on the other hand in microalloyed hot rolled steel strip. The effect of the precipitation and grain hardening on mechanical properties is discu...

The application of the nondestructive potentiometric method utilizing stabilized dc current for the determination of the subcritical crack growth makes it possible to define more accurately the material characteristics defining the fracture toughness of a material. The method is very sensitive and can be used for measuring the fracture initiation o...

The acceptable load range for fatigue crack formation in specimens subjected to fracture toughness testing is discussed. The used stress intensity level ranged from 20 to 40 MPa m** one-half . Microalloyed steel strips 8. 8 and 9. 8 mm thick were tested at two temperatures corresponding to linear-elastic and one corresponding to elastic-plastic beh...

The results obtained using different appproaches of fracture toughness evaluation for two V-Nb microalloyed steels and one microalloyed Mo-Nb steel are compared and discussed. It has been found that the two Nb-V steels have a higher brittle fracture resistance than the Mo-Nb steel in the entire temperature range examined. The microalloyed Nb-V stee...

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