Yusuf Arman

Elastic-plastic finite elements analysis of transient and residual stresses in ceramo-metal restorations

Transient and residual stresses occurring in partially fixed dental prostheses after the firing process can be calculated with elastic or elastic-plastic finite element analyses (FEA). In this study, firstly, the mechanical and thermal properties at various temperatures of the materials used in a porcelain fused metal (PFM) system were obtained by experimental and literature studies. The effects of viscoelastic and viscoplastic behaviours of the dental porcelain at the elevated temperatures were reflected onto its elastic properties. The equivalent heat transfer coefficients were determined experimentally by measuring temperatures and the results were supplied as input to the 3D finite elements analysis. It has been observed that the maximum stresses occur within a short time period after cooling begins and that stresses decrease during the cooling process and remain at a constant value at the end of cooling; these are the thermal residual stresses.

Thermal Stresses in a Thermoplastic Composite Disc under a Steady State Temperature Distribution

In the present study, an elastic-plastic stress analysis is carried out in a thermoplastic composite disc reinforced by steel fibers curvilinearly under a steady state temperature distribution. Elastic, elastic-plastic, and residual stresses are calculated in the solution. The largest tangential stress and the highest residual stress components are found around the inner portion of the disc. The solution is also performed by the finite element solution. Both solutions are observed to be in good agreement.

An experimental and numerical investigation on low velocity impact behavior of composite plates

This paper presents an experimental and numerical investigation on low velocity impact response of S2 glass/epoxy and aramid/epoxy composite plates. Two different impact energy levels, 20 J and 30 J, were considered for impact tests. The commercial software called LS-DYNA was used in order to perform numerical simulations. The experimental and numerical results were found to be in good agreement.

Effect of interface crack on lateral buckling behavior and free vibration response of a sandwich composite beam

The aim of this study is investigation of the effect of interface crack on lateral buckling load and free vibration response of a sandwich composite beam using experimental methods and finite element solutions. The lateral buckling load and natural frequencies in a thin sandwich composite cantilever beam with crack were considered. The crack was opened between the face sheets and foam core. The length of the crack was selected, such as 100, 150, 200, and 250 mm. Lateral buckling and vibration tests were applied on these samples and then the critical lateral buckling load and natural frequencies were found using experimental and finite element method. In the experimental studies, in-house test mechanisms were used. For the numerical analysis, ANSYS finite element software was used. Close results were obtained between both two methods.

Effects of temperature and impactor nose diameter on the impact behavior of PA6 and PP thermoplastic composites

In this study, the effects of temperature and impactor nose diameter on the impact behavior of woven glass-reinforced polyamide 6 (PA6) and polypropylene (PP) thermoplastic composites were investigated experimentally. Impact energies are chosen as 10, 30, 50, 70, 90, 110, 130, and 170 J. The thickness of composite materials is 4 mm. Impact tests were performed using a drop weight impact testing machine, CEAST-Fractovis Plus, and the load capacity of test machine is 22 kN. Hemispherical impactor nose diameter of 12, 7, and 20 mm were used as an impactor. The tests are conducted at room temperature (20°C and 75°C). As a result, the PP composites of the same thickness absorbed more energy than PA6 composites. The amount of absorbed energy of PP and PA6 composites decreased with temperature.