Basic parameters of the static stability, loads and strength of the vital parts of a bucket wheel excavator's slewing superstructure

Determining a bucket wheel excavator (BWE)'s slewing superstructure weight and its center of gravity (COG) is of extreme importance not only in the design phase, but also after the completion of the erection process and during the operation of the machine. This paper presents a critical comparative analysis of the basic parameters of the static stability of a BWE 1600 superstructure, with the parameters being obtained by both analytical and experimental procedures. The analysis shows that a relatively small difference in superstructure mass, obtained by calculation, leads to a relatively large unfavorable shifting of its COG, necessitating a significant increase in counterweight mass for balancing. A procedure for superstructure 3D model mass correction is presented based on results obtained by weighing after the completion of the erection process. The developed model provides enough accuracy to determine the superstructure's COG in the entire domain of the bucket wheel boom inclination angle, and enables accurate load analysis of the superstructure's vital parts. The importance of this analysis is reinforced by the finding that the procedure prescribed by standard DIN 22261-2 gives results which are not on the side of safety, as shown by an example of strength analysis of a bucket wheel boom stays' end eyes

Basic parameters of the static stability, loads and strength of the vital parts of a bucket wheel excavator's slewing superstructure

Determining a bucket wheel excavator (BWE)'s slewing superstructure weight and its center of gravity (COG) is of extreme importance not only in the design phase, but also after the completion of the erection process and during the operation of the machine. This paper presents a critical comparative analysis of the basic parameters of the static stability of a BWE 1600 superstructure, with the parameters being obtained by both analytical and experimental procedures. The analysis shows that a relatively small difference in superstructure mass, obtained by calculation, leads to a relatively large unfavorable shifting of its COG, necessitating a significant increase in counterweight mass for balancing. A procedure for superstructure 3D model mass correction is presented based on results obtained by weighing after the completion of the erection process. The developed model provides enough accuracy to determine the superstructure's COG in the entire domain of the bucket wheel boom inclination angle, and enables accurate load analysis of the superstructure's vital parts. The importance of this analysis is reinforced by the finding that the procedure prescribed by standard DIN 22261-2 gives results which are not on the side of safety, as shown by an example of strength analysis of a bucket wheel boom stays' end eyes

Impact of cutting elements on forces and roughness of surface during turning hard steel X160 CrMo V12 with CBN tool

Cilj ovih istraživanja se odnosi na istraživanje uticaja elemenata režima rezanja na promenu sila rezanja, kvaliteta obrađene površine i promene fizičko-mehaničkih svojstava u površinskom sloju alata od CBN pri struganju čelika X160 CrMo V12, tvrdoće 60 ± 2 HRC. Rezultati istraživanja habanja površine alata ukazuju na prisustvo procesa oksidacije i promene fizičko-mehaničkih svojstava u površinskom sloju alata. Evaluacija sile jasno pokazuje da je radijalna sila (Fr) dominantna pri obradi ovog čelika. Razvijeni su matematički modeli zavisnosti sila rezanja i kvaliteta obrađene površine. Utvrđeno je da oksidacija površine alata, neposredno uz kontaktnu zonu alat-strugotina, dovodi do povećanja njihove tvrdoće i smanjenja čvrstoće, što u krajnjoj meri dovodi do pojave mikrokrzanja reznog sečiva a time i ubrzanog habanja alata.The goal of these researches is related to the analyses of the impact of elements of cutting mode on the change of cutting forces, quality of a machined surface and change of physical and mechanical properties of a surface layer of a CBN tool for turning of X160 CrMo V12 steel having a hardness of 60 ± 2 HRC. The results of the analyses of tool surface wear indicate the presence of oxidation and changes of physical and mechanical properties in a tool surface layer. The evaluation clearly shows that a radial force (Fr) is dominant during the machining of this steel. The mathematical models of dependence of cutting force and a quality of machined surface were developed. It was ascertained that an oxidation of the tool surface, next to a contact zone tool-cutting chip, leads to the increase of their hardness and reduction of their strength, and it finally leads to the emergence of micro-wear of a cutting knife and rapid tool wear

Experimental research on machine elements of helicoidal shell shape

U radu su predstavljeni modeli za eksperimentalno i numeričko istraživanje zavojne ljuske. Tri oblika su odabrana za eksperiment: model A predstavlja zavojnu ljusku na cilindričnoj ljuski, model B kružnu ljusku na cilindričnoj ljuski, i model C pravokutnu ljusku na cilindričnoj ljusci. Ostvarenje kontinualnog opterećenja po površini ljuske je izvršeno pomoću normalnog tlaka koga osigurava konstrukcija sa dvostrukom zavojnom ljuskom sa posebnim elementima za brtvljenje. Mjerenje naprezanja je izvršeno korištenjem mjernih traka. Usporedni rezultati su dobiveni uporabom softverskog paketa za analizu pomoću metode konačnih elemenata ANSYS Workbench. Eksperimentalna istraživanja su potvrdila da numeričko modeliranje daje mjerodavne rezultate naprezanja, deformacija i ugiba kontinualno opterećene zavojne ljuske.In this paper we present a model for the experimental and numerical study of helical shells. Three different forms were chosen for the experiment: Model A forms a helicoidal shell on a cylindrical shell, Model B is an annular shell on a cylindrical shell and Model C a rectangular plate on a cylindrical shell.. Placing a continuous load on the surface of the shell was achieved by normal pressure, thanks to special sealing elements within the construction of the double helical shell.The strain was measured using strain gauges. Comparable results were obtained using the ANSYS Workbench software package for analysis using the finite element method. The experimental investigation confirmed that the numerical modelling provides relevant results for the stress, deformation and deflections of continuously loaded helical shells

Micro-Cutting Mechanisms in Silicon Nitride Ceramics Silinit R Grinding

The paper contains an experimental study of micro-cutting intended to help the optimization of the grinding process of the silicon nitride ceramic Silinit R (Si3N4 - Al2O3 - AIN - TiN). The investigations were carried out to determine the normal and tangential cutting forces, the critical penetration depth and the specific grinding energy as a function of the grain penetration speed and depth. The micro-cutting process was performed with a single diamond cone-shaped grain (tip angle 120 [degrees] and tip radius 0.2 [min]) at varying depths of cut. The critical grain penetration depth separating ductile flow from brittle fracturing falls within the 6-8 [mu m] range. The specific grinding energy ranges from 135 - 180 [J/mm(3)] in ductile flow and from 60 80 [J/mm(3)] in brittle fracturing

Micro-Cutting Mechanisms in Silicon Nitride Ceramics Silinit R Grinding

The paper contains an experimental study of micro-cutting intended to help the optimization of the grinding process of the silicon nitride ceramic Silinit R (Si3N4 - Al2O3 - AIN - TiN). The investigations were carried out to determine the normal and tangential cutting forces, the critical penetration depth and the specific grinding energy as a function of the grain penetration speed and depth. The micro-cutting process was performed with a single diamond cone-shaped grain (tip angle 120 [degrees] and tip radius 0.2 [min]) at varying depths of cut. The critical grain penetration depth separating ductile flow from brittle fracturing falls within the 6-8 [mu m] range. The specific grinding energy ranges from 135 - 180 [J/mm(3)] in ductile flow and from 60 80 [J/mm(3)] in brittle fracturing

ANALYSIS OF THE OF HELICOIDAL SHELL BENDING ON CYLINDRICAL SHELL

ABSTRAC

A study on friction stir welding of AlSi1MgMn aluminium alloy plates

U radu su prezentirana eksperimentalna istraživanja i numeričke simulacije procesa zavarivanja trenjem (FSW). Cilj rada je određivanje termo-mehaničkih i kinematičkih parametara procesa spajanja lima od aluminijske legure AlSi1MgMn debljine 7,8 mm. Eksperimentalna istraživanja su projektirana na temelju usvojenog višefaktornog plana (DoE), s variranjem faktora na dvije razine i ponavljanjem u središnjoj točki plana. Parametri varirani u eksperimentu su: brzina zavarivanja, kutna brzina okretanja alata, kut nagiba trna, promjer trna i promjer čela alata. Na temelju usvojenih geometrijskih parametara projektirana je i izrađena familija alata. Eksperiment je proveden u laboratorijskim uvjetima, koji su slični proizvodnom okruženju. Za numeričku simulaciju procesa FSW, korišten je programski paket DEFORM-3D. U radu je prikazana detaljna analiza i usporedba istraživanih parametara dobivenih eksperimentalnim putem i numeričkom simulacijom.Presented in this paper are an experimental investigation and numerical simulations of the Friction Stir Welding (FSW) process. The aim was to determine thermo-mechanical and kinematic parameters of the process of joining two AlSi1MgMn aluminium alloy plates with the thickness of 7,8 mm. Experimental study was designed based on the 2-level multifactorial design of experiment (DoE), with centre points. Parameters varied in the experiment were: welding speed, rotation speed, angle of pin slope, pin diameter and shoulder diameter. Based on the adopted geometric parameters, the family of tools was designed and manufactured for the experiment. The experiment was performed in laboratory conditions, which were similar to production environment. Numerical simulation of the FSW process was carried out using DEFORM-3D software. Detailed analysis of the process as well as comparison between experimental and numerical results is presented