Influence of Purging Gas on 316L Stainless Steel Fusion Zone in Autogenous Stationary TIG Welding

This research reveals the influence of different purging conditions on the fusion zone dimensions and shape for stationary autogenous TIG welding of 316L stainless steel. Welding experiments were performed for unpurged and purged weld root side for 7, 14 and 21 second arcing time. Purging was executed with ten seconds of pre-flow and 23 seconds of post-flow with 10 l/min Ar and 4 l/min of He. Characteristic fusion zone dimensions were extracted and calculated from photo-macrographs of weld cross-sections. Purging the weld root side by argon increased penetration depth and cross-section area compared to helium. Those benefits of argon purging can be attributed to its low thermal conductivity. Measurement of thermal cycles on the weld root side revealed that peak temperatures were higher by argon purging compared to the presence of helium or air. The fusion zone width exhibited no significant differences regardless of weld root side gas type

Optimization of thin-walled constructions in CAE system ANSYS

Znanstveni pristup rješavanju problema optimiranja sa stanovišta naprezanja i deformacije u konstrukciji provedeno je u ovom radu na primjeru teleskopske ruke. To je uglavnom zbog činjenice da, unatoč širokom spektru uporabe teleskopskih ruku, ne postoje općenito valjana, znanstveno dokazana i prezentirana teorijska načela za njihovo projektiranje. Sa stajališta mehanike, krak teleskopske ruke, kao predmet istraživanja može se svrstati u tankostjene konstrukcije. U stvari, riječ je o zatvorenom tankostjenom presjeku opterećenom kombinacijom savojnih i torzijskih momenata. Primjenjujući metodu konačnih elemenata (MKE) povezanu s CAE sustavom ANSYS moguće je projektirati optimalan oblik poprečnog presjeka poluge teleskopske ruke. Uspoređujući izračunate vrijednosti naprezanja i deformacije s vrijednostima dobivenim eksperimentalnim mjerenjima, moguće je procijeniti učinkovitost procesa optimiranja.Solving optimization problems from the standpoint of structural stresses and strains can be carried out scientifically on the example of telescopic jib. It is mainly due to the fact that despite a broad spectrum of the telescopic jib utilization there are no generally valid, scientifically proven and presented theoretical principles for their designing. From the viewpoint of the classification of mechanics, the arm of telescopic jib as a subject of study can be ranked among thin-walled constructions. In fact, it is a case of enclosed thin-walled bars stressed in operation by a combination of bending and torsion moments. Applying the Finite Element Method (FEM) in connection with the CAE system ANSYS, it is possible to design an optimum shape of the cross-section of the telescopic jib arm. Comparing the calculated values of stresses and deformations with the values obtained by experimental measuring, it is possible to evaluate the effectiveness of the optimization process

The Influence of Material Storage on Mechanical Properties and Deterioration of Composite Materials

This article focused on the experimental and statistical analysis of the mechanical properties of dog-bone samples manufactured by fused deposition modelling (FDM). Two identical materials were examined, i.e., Onyx with carbon fiber but from different series and differently stored. One was kept in the manufacturer package and the other one was kept in machine storage box. The paper explains how the samples with various numbers of fiber layers and printing infill were created, 3D printed, measured to evaluate their accuracy in dimensions, exposed to tensile test, and reviewed. At this stage of investigation, the paper is limited to static tests of materials. The data presented here will be of great assistance for additional studies intended for the filament deposition development and modification of the basic material through the combinations with different composites, such as carbon fiber. It was discovered with this research that the mechanical properties of test samples created by FDM can differ based on the manufacturer series. This issue has not been studied thoroughly, so far. Research, by analysing the key variable, which is the batch of 3D print material, offers important new data to engineers and designers. It also prepares the ground for advanced studies and research in respect of the weakness and strength analysis of the 3D printed models.That is very relevant for the optimizing structures in this modern age and the industrial era 4.0 as well as the development in the LEAN process of manufacturing

Unbalance Response Analysis of a Rotor Kit with Two Identical Discs Located Between Bearings

In this paper, the dynamic behavior of a rotor kit with two identical disks located between the plain bearings was analyzed. Modal and harmonic analysis of this rotor kit configuration were performed in the Ansys software package. To calibrate the bearing parameters (stiffness and damping) in the numerical model, experimental measurements of the rotor kit with a disc mounted at the midspan of the shaft were performed. As a result of modal analysis, natural frequencies and models were obtained. Using the Campbell’s diagram, the critical speeds and the influence of the gyroscopic effects on the natural frequencies were determined. The responses of the rotor kit to different unbalance distributions were considered by harmonic analysis

Finite element modelling of creep process - steady state stresses and strains

Finite element modelling of steady state creep process has been described. Using an analogy of visco-plastic problem with a described procedure, the finite element method has been used to calculate steady state stresses and strains in 2D problems. An example of application of such a procedure have been presented, using real life problem - cylindrical pipe with longitudinal crack at high temperature, under internal pressure, and estimating its residual life, based on the C* integral evaluation

Finite Element Analysis of a Shrink Fitted Disc-Shaft Rotating System

In this paper, the shrink fit between the conical disk and the rotor shaft of a steam turbine was analysed with the aim of determining the rotor speed at which this fit is lost. The analysis was carried out numerically using the finite element method (FEM) in the Ansys software package. Three design values of disc-shaft joint interference were considered: minimum, maximum and mean. The rotor speed at which the shrink fit is lost is the lowest for minimum interference and the highest for maximum interference, which was expected. In other words, the rotor speed at which the shrink fit is lost is a linear function of the amount of interference (the allowance). The results of the analysis showed that the considered interferences of the shrink fit ensured the smooth transmission of torque in the range of speeds up to the operating speed and that the operation of the turbine is safe from that point of view

Investigation of the mixed-mode fracture in delamination tests: numerical simulations using cohesive zone and partitioning methods

U radu se istražuju pokusi delaminacije (loma) pomoću numeričkih simulacija u kojima su korištene različite osobine kohezivnih zona. Koristili su se asimetrični i simetrični dvokraki gredni uzorci opterećeni momentom savijanja. Udjeli tipa I i tipa II loma u ukupnoj energiji loma su proračunati pomoću globalnog i lokalnog pristupa. Rezultati mješovitog tipa loma su prezentirani i analizirani. Numeričke vrijednosti podjele energije za različite konfiguracije su uspoređene s dvije analitičke teorije podjele energije, koje su postavili Williams te Hutchison i Suo. Nasuprot teorijama, uočena je ovisnost podjele energije o osobinama kohezivne zone.Delamination (fracture) tests have been numerically investigated using various cohesive zone properties. The test utilises asymmetric and symmetric double cantilever beam specimens loaded with bending moment. Energy release rate contributions from mode I and mode II fracture are calculated using a global and local approach. Mode-mixities results are presented and analysed. The numerical partitioning results for different configurations are compared to two analytical partitioning theories, namely, after Williams and after Hutchinson and Suo. Opposite to these theories, partitioning is observed to be dependent on cohesive zone properties

Numerical-Experimental Determination of Stress and Deformation State in Connecting Lugs with the Effect of Contact Area Size

The present paper describes numerical and experimental methodology for the analysis of stress and deformation state in structural elements with geometrical discontinuities. The research is based on structural elements of the connecting lug type. The stress and deformation state was determined as the contact area size between the axle and the connecting lug was changing. Numerical analysis was conducted by applying the finite element method in a ''KOMIPS'' software package. Experiments were performed at the Laboratory for stress and deformation measurements, Faculty of Mechanical Engineering, University of Belgrade, using ''GOM'' equipment and ''ARAMIS'' software application (DIC). This paper demonstrates how it is possible to anticipate the results by applying FEM. A short review of current research in the field of structural elements with geometrical discontinuities is given within the framework of the paper

Numerical-Experimental Determination of Stress and Deformation State in Connecting Lugs with the Effect of Contact Area Size

The present paper describes numerical and experimental methodology for the analysis of stress and deformation state in structural elements with geometrical discontinuities. The research is based on structural elements of the connecting lug type. The stress and deformation state was determined as the contact area size between the axle and the connecting lug was changing. Numerical analysis was conducted by applying the finite element method in a \u27\u27KOMIPS\u27\u27 software package. Experiments were performed at the Laboratory for stress and deformation measurements, Faculty of Mechanical Engineering, University of Belgrade, using \u27\u27GOM\u27\u27 equipment and \u27\u27ARAMIS\u27\u27 software application (DIC). This paper demonstrates how it is possible to anticipate the results by applying FEM. A short review of current research in the field of structural elements with geometrical discontinuities is given within the framework of the paper

An Estimation of Sufficient Impact Toughness for the Material of a Turbine Shaft

The fracture of a turbine shaft in the case of overloading can exhibit brittle or plastic failure, depending on the material properties, the turbine-shaft geometry and the form of loading. Usually, when the toughness increases, the stiffness of the shaft material is reduced, which can lead to the plastic twist of the shaft. If the fatigue crack appears in the critical region of the shaft then the low impact-toughness value may induce a brittle fracture. During the retrofit of a hydro-power plant a new turbine shaft was produced by quenching-and-tempering technology. Charpy impact-toughness tests showed lower values for the shaft material than those prescribed by the project documentation. Since the turbine shaft for a hydro-power plant is a massive and expensive component, it is necessary to determine a sufficient impact toughness for the material in terms of the geometry and the manner of loading for the turbine shaft. Since only the yield strength and the impact toughness of the material were prescribed, the level 0 of the SINTAP should be applied. The minimum impact toughness values that ensure the ductile fracture of the shaft, cracked circumferentially was also estimated. We also analyzed the variation of the shaft’s carrying capacity resulting from a reduction of the non-cracked ligament in the transversal direction