Wyniki wyszukiwania - BazTech

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Mechanical response at peri-implant mandibular bone for variation of pore characteristics of implants: A Finite Element Study

Sarkar Sulagna, Sahu Tikeshwar Prasad, Datta Arijit, Chandra Nimesh, Chakraborty Arindam, Datta Pallab, Majumder Santanu, Chowdhury Amit Roy

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 2

83--93

EN

In this paper, the mechanical response of generic dental implants having calculated porosities with varying pore-sizes has been evaluated. The purpose of this study was to compare the developed stress-strain of designed porous implants (i.e., stress at the implant and strain at the peri-implant bone) with that of the non-porous implant. Methods: 3D model of a mandible was prepared from CT scan data and nine generic dental implant models have been designed having 10%, 20%, and 30% porosity with 500, 700, and 900 micron pore size along with a non-porous model for carrying out FE analyses. First, failure analyses of implants, under a biting force of 250 N have been performed. Next, the remaining implants have been further evaluated under average compressive chewing load of 100 N, for mechanical responses at bone-implant interface. Results: Von Mises strain at the peri-implant mandibular bone increases with the increase in percentage porosity of the implant material and maximum implant stress remained much below the yield stress level. Conclusion: Implant stiffness and compressive strength vary as a function of porosity and pore size. Strain obtained on the peri-implant bone is sufficient enough to facilitate better bone growth with the 700 micron pore size and 30% porosity, thus reducing the effect of stress shielding.

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Numerical analysis of friction welded titanium joints

Shenbaga Velu P., Rajesh Jesudoss Hynes N.

Journal of Achievements in Materials and Manufacturing Engineering

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2016

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Vol. 76, nr 1

26--29

EN

Purpose: Friction welding is found to be a suitable candidate for joining the dissimilar materials. Numerical model would be helpful for proper selection of processing conditions. In the present work, a thermo-mechanical model has been developed using finite element method based software. Design/methodology/approach: Friction welding process is characterized of thermomechanical phenomenon, which is highly complex in nature. Thermo-mechanical model is considered as highly nonlinear due to the interaction between the temperature fields and time dependent on the material properties. The numerical model is subject to certain assumptions and boundary conditions. Findings: The numerical investigation was carried out to predict the temperature distribution, heat flux, the axial shortening and stress on the friction welded titanium joints. Research limitations/implications: Leading aerospace manufacturers are exploring the joining of titanium to titanium for aerospace applications. The approach is time saving and it is supposed to have a promising future in automotive and nuclear fields.

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Application of Gurson-Tvergaard-Needelman function to modelling of plastic deformation in ductile iron with a ferritic matrix

Piekło J., Maj M.

Inżynieria Materiałowa

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2013

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Vol. 34, nr 4

349--353

EN

Based on the criterion of ductile fracture and progressive degradation of material stiffness, the ﬁnite element method (FEM) was used to determine changes in components of the stress state in a numerical model of the spheroidal graphite precipitate and ferritic matrix under the influence of increasing tensile forces leading ultimately to the matrix fracture. For different densities of the graphite precipitates, an increase in the volume of void surrounding the graphite precipitate at an instant of the fracture fonnation was calculated, assuming it to be equal to a critical value fCR of the void volume fraction in the Gurson-Tvergaard-Needelman (GTN) model. Using the GTN yield condition, in which the previously determined values offCR were allowed for, stretching of a cylindrical specimen until rupture was simulated by FEM, comparing the resulting stress-strain curve with the curve determined experimentally for the EN-GJS-400-18 cast iron.

PL

Na podstawie kryterium pękania ciągliwego oraz progresywnej degradacji sztywności materiału, metodą elementów skończonych (MES), wyznaczono zmiany wartości składowych stanu naprężenia w modelu numerycznym wydzielenia graﬁtu kulkowego i osnowy ferrytycznej pod wpływem rosnącej wartości sił rozciągających, aż do chwili pęknięcia osnowy. Dla różnych gęstości wydzieleń graﬁtu określono przyrost objętości pustki otaczającej wydzielenie graﬁtu w momencie powstania pęknięcia, przyjmując założenie, że jest ona równa krytycznej wartości udziału objętościowego pustek fcrz W modelu Gursona-Tvergaarda-Needelmana (GTN). Stosując warunek plastyczności GTN, w którym uwzględniono wcześniej wyznaczone wartości fCR, metodą MES przeprowadzono symulację rozciągania próbki walcowej, aż do chwili zerwania, porównując uzyskane zależności naprężenie-odkształcenie z doświadczalnie wyznaczoną krzywą rozciągania żeliwa EN-GJS-400-18.

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Rozkłady naprężeń i odkształceń w próbkach gładkich i z karbem przy kominacji zginania ze skręceniem

Łagoda T., Macha E., Molski K., Ferenc R.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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2001

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Z. 73

55-62

PL

W pracy przedstawione są wyniki obliczeń za pomocą metody elementów skończonych rozkładów naprężeń i odkształceń w przekrojach prętów gładkich i z karbem w przypadku zginania, skręcania i kombinacji proporcjonalnego zginania ze skręcaniem. W obliczeniach przyjęto model ciała sprężystego i sprężysto - plastycznego.

EN

The paper presents the calculation results obtained with use of the finite element method for stress and strain distribution in the sections of smooth and notched bars under bending, torsion and combined proportional bending with torsion. For calculations it was assumed that the body is elastic and elastic - plastic with exponential hardening rule.