Numerical aspects for efficient welding computational mechanics

The effect of the residual stresses and strains is one of the most important parameter in the structure integrity assessment. A finite element model is constructed in order to simulate the multi passes mismatched submerged arc welding SAW which used in the welded tensile test specimen. Sequentially coupled thermal mechanical analysis is done by using ABAQUS software for calculating the residual stresses and distortion due to welding. In this work, three main issues were studied in order to reduce the time consuming during welding simulation which is the major problem in the computational welding mechanics (CWM). The first issue is dimensionality of the problem. Both two- and three-dimensional models are constructed for the same analysis type, shell element for two dimension simulation shows good performance comparing with brick element. The conventional method to calculate residual stress is by using implicit scheme that because of the welding and cooling time is relatively high. In this work, the author shows that it could use the explicit scheme with the mass scaling technique, and time consuming during the analysis will be reduced very efficiently. By using this new technique, it will be possible to simulate relatively large three dimensional structures

Failure criteria of fibre reinforced composites in homogeneous temperature field

The present paper examines the failure criteria of layered composites with orthotropic properties in the homogeneous temperature field. The composite has modeled by two mechanically equivalent families of fibres. The paper formulates constitutive equations in terms of intrinsic preferred directions, which are defined by the orientation of fibers at any point of the composite. A uniformly heated, thermoelastic solid undergoes distortion as well as volume change because it experiences differential expansions in different directions. This effect is more complicated if, in addition of being anisotropic, the material is inhomogeneous, as in the case with laminated materials. In order to illustrate the influence of temperature on the failure of this group of materials constitutive equations are derived and adoptedforuse in failure criteria, without the influence of temperatures, and with the influence of increased temperature

Novel Quorum Quenching YtnP Lactonase From Bacillus paralicheniformis Reduces Pseudomonas aeruginosa Virulence and Increases Antibiotic Efficacy in vivo

Bacterial infections have become increasingly difficult to treat due to the occurrence of antibiotic-resistant strains. A promising strategy to increase the efficacy of therapy is to combine antibacterials with agents that decrease pathogen virulence via the modulation of the quorum sensing (QS). Lactonases inhibit acylated homoserine lactone (AHL)-mediated QS in Gram-negative bacteria, including the leading nosocomial pathogen Pseudomonas aeruginosa. Here we describe the characteristics of heterologously expressed YtnP lactonase from Bacillus paralicheniformis ZP1 (YtnP-ZP1) isolated from agricultural soil using the culture enrichment method. Purified YtnP-ZP1 hydrolyzed different AHLs with preference to substrates with long acyl residues as evaluated in assays with biosensors and HPLC. The enzyme showed good thermostability and activity in a wide temperature range. YtnP-ZP1 in 50 μg mL–1 concentration reduced the amount of P. aeruginosa-produced long-chain AHLs by 85%, while it hydrolyzed 50% of short-chain AHLs. Incubation of P. aeruginosa PAO1 with YtnP-ZP1 reduced its swarming motility and elastolytic activity without bactericidal effect. YtnP-ZP1 caused the inhibition of biofilm formation and disintegration of mature biofilms in P. aeruginosa PAO1 and multiresistant clinical strain BR5H that was visualized by crystal violet staining. The treatment with YtnP-ZP1 in concentrations higher than 25 μg mL–1 improved the survival of P. aeruginosa PAO1-infected zebrafish (Danio rerio), rescuing 80% of embryos, while in combination with tobramycin or gentamicin survival rate increased to 100%. The treatment of P. aeruginosa PAO1 biofilms on infected zebrafish tail wounds with 50 μg mL–1 YtnP-ZP1 and 2 × MIC tobramycin led to infection clearing in 2 days. The extensive toxicity studies proved YtnP-ZP1 was non-toxic to human cells and zebrafish. In conclusion, novel YtnP-ZP1 lactonase with its effective anti-virulence activity could be used to increase the efficacy of clinically approved antibiotics in clearing both systemic and biofilm-associated P. aeruginosa infections

Web-based laboratory for collaborative and concurrent CAD designing, assembling, and practical exercising on distance

Kolaborativno modeliranje dislociranih učesnika postaje neophodan segment pravovremenog CAD projektiranja. Kompleksni sustavi namijenjeni kolaborativnom projektiranju su velika investicija i iz tog razloga njihova uporaba nije česta. Iako većina CAD programa ima module za suradnju, takva rješenja mogu predstavljati veliki trošak, posebice obrazovnim institucijama koje obučavaju veliki broj studenata. Između ostalog, spomenuti moduli uglavnom rade u određenom CAD programu i pružaju podršku za uvoz i izvoz ograničenog broja CAD formata. U ovom je radu prikazano rješenje otvorenog koda koje nadilazi prethodno navedene probleme. Predloženo rješenje omogućava praktičan rad na daljinu, kombinirajući najčešće rabljene CAD alate u industrijskom dizajnu. U radu je opisana uporaba virtualnog laboratorija za brzo projektiranje izvođenjem praktičnih vježbi, arhitektura predloženog rješenja, modeliranje laboratorija i metode za kreiranje njegovih funkcija. Praktičan primjer prikazuje kolaborativno sklapanje zrakoplova između udaljenih sudionika, s dijelovima modeliranim u različitim CAD paketima. Upotrebljivost laboratorija prikazana je izradom prototipa sklopljenog modela na 3D tiskaču i njegovog završnog testa u zračnom tunelu. Dana je kvalitativna i kvantitativna evaluacija predloženog rješenja. U zaključnom dijelu, dana su predviđanja po pitanju uporabe tehnologija za izgradnju virtualnih laboratorija i virtualnih sklopova.Collaborative CAD of distant modelling is a today’s necessity for realization in a timely manner. This need arises even within educational institutions, where investments in the development of technologies to support collaborative distance learning are still trivial. Most CAD programs used in engineering have modules for collaboration. However, these solutions are expensive, especially for educational institutions that have a large number of students. The mentioned modules generally work within a specific CAD platform and support import and export of a limited number of CAD formats. In this paper, we present an open-source solution that overcomes these problems. It implements practical work at a distance by combining most commonly used CAD platforms in engineering. In this paper, we describe how to use virtual laboratory for rapid designing through execution of practical exercises. The architecture of the proposed solution, the modelling of the laboratory and methods for creating its functions are described. Also, given is a tangible example of collaborative aircraft assembly between distant students, with parts modelled in different CAD packages, and the usability of labs presented through prototype builds on 3D printer and the final test in the wind tunnel. Qualitative and quantitative evaluations were conducted. Conclusions set the direction of the future development using various technologies for building virtual assembly laboratory

Failure criteria of fibre reinforced composites in homogenous temperature field

The present paper examines the failure criteria of layered composites with orthotropic properties in the homogeneous temperature field. The composite has modeled by two mechanically equivalent families of fibres. The paper formulates constitutive equations in terms of intrinsic preferred directions, which are defined by the orientation of fibers at any point of the composite. A uniformly heated, thermoelastic solid undergoes distortion as well as volume change because it experiences differential expansions in different directions. This effect is more complicated if, in addition of being anisotropic, the material is inhomogeneous, as in the case with laminated materials. In order to illustrate the influence of temperature on the failure of this group of materials constitutive equations are derived and adoptedforuse in failure criteria, without the influence of temperatures, and with the influence of increased temperature

NONINVASIVE DETERMINATION OF KNEE CARTILAGE DEFORMATION DURING JUMPING

The purpose of this investigation was to use a combination of image processing, force measurements and finite element modeling to calculate deformation of the knee cartilage during jumping. Professional athletes performed jumps analyzed using a force plate and high-speed video camera system. Image processing was performed on each frame of video using a color recognition algorithm. A simplified mass-spring-damper model was utilized for determination of global force and moment on the knee. Custom software for fitting the coupling characteristics was created. Simulated results were used as input data for the finite element calculation of cartilage deformation in the athlete's knee. Computer simulation data was compared with the average experimental ground reaction forces. The results show the three-dimensional mechanical deformation distribution inside the cartilage volume. A combination of the image recognition technology, force plate measurements and the finite element cartilage deformation in the knee may be used in the future as an effective noninvasive tool for prediction of injury during jumpin

Comparative thermal buckling analysis of functionally graded plate

A thermal buckling analysis of functionally graded thick rectangular plates according to von Karman nonlinear theory is presented. The material properties of the functionally graded plate, except for the Poisson's ratio, were assumed to be graded in the thickness direction, according to a power-law distribution, in terms of the volume fractions of the metal and ceramic constituents. Formulations of equilibrium and stability equations are derived using the high order shear deformation theory based on different types of shape functions. Analytical method for determination of the critical buckling temperature for uniform increase of temperature, linear and nonlinear change of temperature across thickness of a plate is developed. Numerical results were obtained in Matlab software using combinations of symbolic and numeric values. The paper presents comparative results of critical buckling temperature for different types of shape functions. The accuracy of the formulation presented is verified by comparing to results available from the literature

New shape function for the bending analysis of functionally graded plate

© 2018 by the authors. The bending analysis of thick and moderately thick functionally graded square and rectangular plates as well as plates onWinkler-Pasternak elastic foundation subjected to sinusoidal transverse load is presented in this paper. The plates are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity of the plate is assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents. This paper presents the methodology of the application of the high order shear deformation theory based on the shape functions. A new shape function has been developed and the obtained results are compared to the results obtained with 13 different shape functions presented in the literature. Also, the validity and accuracy of the developed theory was verified by comparing those results with the results obtained using the third order shear deformation theory and 3D theories. In order to determine the procedure for the analysis and the prediction of behavior of functionally graded plates, the new program code in the software package MATLAB has been developed based on the theories studied in this paper. The effects of transversal shear deformation, side-to-thickness ratio, and volume fraction distributions are studied and appropriate conclusions are given