Simon Sedmak

Welding and testing of welded joints made of HARDOX 400

Rad primljen / Paper received: Januar 2018. Adresa autora / Authors address: 1 i 3 Inovacioni centar Mašinskog fakulteta u Beogradu, Beograd, Srbija. Innovation Center of Faculty of Mechanical Engineering, Belgrade, Serbia MFGO, Fabrika građevinske opreme, Mladenovac, Srbija MFGO, Construction equipment manufacturer, Mladenovac, Serbia KonMat, Beograd, Srbija. KonMat, Belgrade, Serbia Tehnološko metalurški fakultet Univerziteta u Beogradu, Beograd, Srbija. Faculty of Technology and Metallurgy, University of Belgrade, Serbia Stetter GmbH, Memmingen, Nemačka. Stetter GmbH, Memmingen, Germany

The effect of cracks on stress state in crane wheel hard-surface under contact loading

Original scientific paper Shown in this paper are the results of microstructure testing of crane wheels, along with the repair welding procedure performed by hard-surfacing. Repair welding involved the application of a welded layer to the crane wheel, due to the damage that was caused by wear. Detailed analyses, based on the mechanical and chemical properties of the materials used for crane wheels, as well as for repair welding, were performed for the contact between the rail and wheel in real exploitation conditions, as well as by using numerical simulations. Numerical simulations were performed by using the finite element method. For the purpose of the analysis, contact stresses between the wheel and rail were calculated according to Hertz theory. Each of the numerical models was used to perform stress analysis with or without a crack in order to determine crack influence on the crane wheel integrity, and to compare the results with the values obtained theoretically. In addition, the symmetry of the contact area between the wheel and rail was taken into account, i.e. both symmetric and asymmetric contact models were made.

Scientific Biography and Bibliography of Professor Stojan Sedmak

Professor Stojan Sedmak was born in 1929 in Kratovo, then Kingdom of Yugoslavia. He finished high school—gymnasium in Belgrade in 1948, and graduated in 1954 from the Faculty of Mechanical Engineering, University of Belgrade.

Measuring of Strain and Displacements in Welded Joints Subjected to Tensile Load Using Stereometric Methods

During the experimental testing of a welded joint, made of steel P460NL1, complete strain and displacement fields, which provide full insight into the behaviour of a welded joint under tensile load, were obtained using an optical stereometric measuring method. Optical stereometric method involved the application of digital image correlation. Presented in this paper are the strain and displacement for various load levels are shown, along with the behaviour of the welded joint as a whole. As a result of this approach, concrete and accurate values of the observed strain field as a whole can be compared directly, rather than as chosen representative parts that would be tested using a strain gauge in a single position, and provide a more detailed insight into the behaviour of the tested joint. With the aid of images obtained using cameras, the development of strain over time can be monitored, while pointing out the critical parts of a welded joint, allowing the determining of potential locations with increased stress intensity factor.

Experimental examination of fatigue life of welded joint with stress concentration

This paper presents results of experimental examinations of stress concentration influence to fatigue life of butt welded joints with K-groove, produced from the most frequently used structural steel S355J2+N. One group of experiments comprised examinations carried out on the K-groove specimens with stress concentrators of edged notch type. Specimens with short cracks (limited length of initial crack), defined on the basis of the experience from fracture mechanics by the three points bending examinations, have been examined according to standard for the determination of S-N curve, and aimed to determine fatigue strengths for different lengths of initial crack and Relationship between fatigue strength and crack length. Other group of experiments comprised examinations of specimens with edge notch, prepared in accordance with ASTM E 399 for three points bending, in order to establish regularity between crack growth and range of exerted stress intensity factor aimed to determine resistance of welded joint to initial crack growth, namely fatigue threshold

Calculation of Maximum Tensile and Shear Forces in Restorative Materials Using Finite Element Method

The purpose of this paper was to determine tensile loading that leads to dental restoration failure, i.e. the critical values of stress. In order to analyze stress distribution within the restoration and tooth, mechanical properties of materials and tissues, such as Young modulus and Poissons ratio were taken into account. An additional purpose of the paper was to determine whether tensile or shear stresses that occur in the restorative composite and the surrounding enamel cause this failure. Tensile stress is caused by forces acting in the direction perpendicular to the cross-section of a given element, whereas shear stresses are caused by forces parallel to said cross section. A 3D numerical model of a tooth including three different materials (dentine, enamel and composite) was made and used for these calculations. These results will be used as a base for the physical experiment.

Stress Analysis of Hyperbaric Chambers of Different Geometries

Hyperbaric Oxygen Therapy (HBOT) is a method used to administer pure oxygen at a pressure which is greater than atmospheric pressure in order to increase the concentration of O2 in the tissues, blood and cells, and correct or improve certain conditions. The hyperbaric chamber is a medical instrument that provides many benefits to the economy and health protection. They are in fact pressure vessels, subjected to the higher stress levels. In this paper, the stress and deformation state of different multiplace hyperbaric chambers are determined. Stress and deformation states are calculated for different geometry models using ABAQUS. Therefore, the aim of this paper is to define the weakest points in the chambers of different geometry with the use of the Finite Element Method.

J integral as a measure of crack driving force in full-scale pressure vessel test

ABSTRACT Direct measurement of J integral enables the evaluation of crack driving force in full-scale pressure vessel test. The axial notch was positioned with the tip in heat-affected-zone of weldment, obtained by submerged-arc welding. The test has been instrumented by strain gauges along J integral path and by crack mouth opening displacement gauge. Residual stresses, caused by cold forming and welding, were measured according to ASTM E837 method before pressurising. The experimentally obtained results for pressure dependence of J integral has been compared with crack driving force model, developed by Ratwani, Erdogan and Irwin.