Browse Articles

This paper deals with an innovative technique regarding the embedding of biliary stones in plastic materials as an alternative and viable solution for increasing their mechanical resistance during processing for preparing the samples for instrumental analysis. The human gallstones provided from a single patient were embedded in two different polymeric plastics. The samples were investigated for their mechanical resistance under surface grinding using a rotating abrasive wheel on a bench grinder, as well lathing on a lathe machine. A discussion for the best method of embedding and the sample preparation is presented.

In this paper we have studied the influence of discontinuities on elastic and mechanical properties of composite materials reinforced with woven Carbon, Carbon-Kevlar and Kevlar. In addition, we have studied the way variations of the volume proportion of reinforcement influences elasticity modulus and tensile strength for the studied composite materials. In order to appreciate the property difference between different areas of the composite material and also the dimensions of the defective areas, a relative uniformity influence coefficient was introduced offering us a tool for assessing the mechanical behaviour of the studied composite compared with a reference composite. We have also performed experimental validations of the obtained theoretical results.

The paper analyses the effect of oxides powder deposition by plasma spraying and remelting with laser beam on the cavitation resistance of Ti-6Al-4V biphasic alloy. The deposited and remelted coatings were tested for cavitation erosion on the magnetostrictive vibratory apparatus with nickel tube. Using optical and scanning electron microscopy, were obtained qualitative informations about the degradation mechanism and the cavitation erosion evaluation was done by comparing the specific erosion curves of Ti-6Al-4V substrate with those of coated layers.

This paper presents the effect of reinforcement for styrene-butadiene and styrene-isoprene block copolymers with bentonite in correlation with morphology biphasic thermoplastic elastomers.

This paper presents the results of the research carried out in order to establish the optimum technology of polypropylene pipes, analysed from the point of view of temperature, time and labour press. Analysing the values obtained in the practical samples, the graphics of variation of components after assembly were traced, decreasing the diameter of the pipe after the assembly, the parameters that define significantly the quality of the assembly. The need to address such themes derived from the fact that in the literature, in the present time there are not sufficient and relevant information with regard to the assembly of pipes and connectors of PPR, most of the information being provided by the manufacturers and they are confined to the indication of the parameters of the assembly process.

In this study, the static and dynamic properties of LLDPE/RH composites, with different filler contents of 5 wt% RH, 10 wt% RH, 15 wt% RH, 20 wt% RH and, 30 wt% RH were studied at different levels of strain rates (0.001/s, 0.01/s, 0.1/s, 650/s, 900/s and 1100/s) using a conventional Universal Testing Machine and Split Hopkinson Pressure Bar apparatus, respectively. Results show that the strength, stiffness and yield behavior of LLDPE/RH composites were strongly affected by both filler content and strain rate loadings. Apart from that, the rate of sensitivity of LLDPE/RH shows sgreat dependency towards applied strain rate, where it was increased with increasing strain rate. Unfortunately, the thermal activation values show contrary trend. Besides, at dynamic loading, the fracture surface analysis of the composites showed that all specimens experienced massive plastic deformation.

The impact of pressure-assisted thermal processing (PATP) on selected polymeric food packaging materials was studied. Two commercially available packaging materials called APP (combination of biaxially oriented and PVdC coated polyester with a sealing layer against polypropylene) and BPE (combination of biaxially oriented polyester with coextruded barrier film of the structure polyethylene/EVOH/m-polyethylene) were pressurized at 600 MPa for 10 min, at 70°C. The impact of combined pressure-heat treatment on the change of packaging materials was assessed by SEM (Scanning Electron Microscopy). In addition, visual examination was performed for the treated APP and BPE materials. The results showed that the combined extreme pressure-heat treatments can compromise the integrity of both packaging materials. Opaque areas, delaminations and dark spots were a general consequence of the pressure-assisted thermal processing of tested packaging materials.

Replacing weak soil layer by a gravel cushion is a usual consolidation method, wich has been improved lately by inserting in the gravel cushion reinfocements, analogical to concrete reinforcement, aiming to increase the bearing capacity of the foundation soil. This paper presents some aspects regarding geosinthetical materials behaviour used to reinforced the gravel cushion as much as the effect on stresses distribution and displacements in gravel and surrouding soil. This study has been conducted trough experimental tests and numerical analysis. The conducted analysis is statical and nonliniar. The calculus of the study consists of: displacements of the soil, the values of the stresses in inner part of the gravel layer and in the geosinthetic materials. Noticing that the disposal of the reinforcements leads to decrease stresses and displacements values at the foundation level but also at the gravel layer base.

The purpose of this study is associated to the investigation of the acrylic teeth denture base resin interface with invasive tests such as tensile testing. 30 large size artificial acrylic first upper molars (Spofadent Plus_Spofa Dental) were milled to 30 acrylic cylinders. The cylinders were randomly assigned in three experimental groups, so that 10(ten) cylinders were distributed to each one of the three (3) experimental sample groups. The bonding flat surfaces of the cylinders were submitted to a different treatment: Group 1: (control group_without treatment), Group 2: Benzene, Group 3: Toluene. For the chemical treatment procedures, organic solvents with 98.9% chemical purity were used. The bonding test samples were realized according to ADA specification No. 15, using a self-cured denture base repair resin (Duracryl–Spofa Dental, Kerr Company). Each sample was stored for 30 days in distilled water and in tensile tested at 1 mm/min speed. The mean values of the tensile bond strength test registered were statistically significant among groups, ranging from 26.5 MPa (group 1) to 23.13 MPa (group 3). The results of this study suggest the fact that the chemical treatment with the mentioned organic solvents improves not in a significant manner the adhesion of the acrylic teeth to the denture base resin.

The effects of stearic acid treated dolomite (Sa-Dol) on the mechanical, morphological and thermal properties of polypropylene (PP) composite were studied. Prior treatment, raw dolomite was ground in planetary mill using different grinding time to obtain the submicron size (under 10mm). Particle size and specific surface area of dolomite was analyzed and validated using particle size analyzer (Malvern Mastersizer) and Brunauer-Emmett-Teller (BET) method respectively. Dolomite with five filler loadings (5, 10, 15, 20 & 25%) were mixed with PP thermoplastic and were compounded using hot melt blending method. Fourier Transform Infrared (FTIR) spectroscopy confirms the successful of filler treatment using stearic acid according to the new peak at 2917 cm--1 attributed to the alkyl group that represented the addition of C-H bond. Tensile properties indicated that tensile strength of PP/Dol decreased with the increasing of filler loading for both systems. The elongation at break decreased with filler loading and showed better and improved result after treatment with stearic acid. The incorporation of stearic acid coated filler into PP matrix enhanced the break elongation of the composites that makes the composites more ductile. Morphological analysis using Scanning Electron Microscopy (SEM) proved better interfacial adhesion and less agglomeration of dolomite filler after treatment with stearic acid at low filler loading (5 wt.%).