Papers by Keyword: Weibull Analysis

Abstract: It has been studied how SiO₂ nanoparticles affect the mechanical and electrical properties of low-density polyethylene (LDPE). The tensile strength, microstructural features, and AC breakdown characteristics of LDPE containing silicon dioxide (SiO₂) nanoparticles were investigated in this work. The concentrations of filler were adjusted to 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 3.0 wt%, and 4.0 wt%. The samples were prepared by using Haake machine and shaped by compression moulding, and a sphere to sphere electrode arrangement was used for AC breakdown testing. The breakdown reliability was assessed using the Weibull distribution. Molecular interaction and nanoparticle dispersion were analysed using Raman spectroscopy and scanning electron microscopy (SEM), respectively. The findings demonstrated that mechanical strength and breakdown voltage increases with filler concentration, reaching a maximum at 2.0 wt% SiO₂. When compared to pure LDPE, the AC breakdown voltage increased by 27.54% at this concentration. SEM pictures showed a homogeneous dispersion of nanoparticles, while Raman spectra verified improved interfacial bonding. AC breakdown voltage above 2.0 wt% shows decrease value due to agglomeration of nanoparticles. According to this study, LDPE insulation performance is best enhanced by 2.0 wt% SiO₂.

Abstract: In this work, the processing of α-Al₂O₃ ceramics is studied in order to attain the microstructure and mechanical and thermal properties suitable for its application as a special refractory material in sintering furnaces. Samples of a commercial powder with addition of 3% polyvinyl alcohol, a binder additive, was compacted by uniaxial cold pressing and sintered in air at 1500 oC. The effects of powder preparation conditions and the consolidation process on density, thermal expansion and conductivity, hardness, flexural strength and microstructure were analyzed. Ceramics with densities of approximately 90% were obtained, with an average hardness of 14.9 ± 0.6 GPa, characteristic strength of 238 MPa and Weibull modulus of 8. The microstructure had grain sizes between 1 and 2 μm. Processing and powder consolidation and sintering parameters resulted in alumina ceramic with suitable properties for its intended purpose.

Abstract: Societal, economical, technical and environmental advantages are today justifying the replacement of synthetic fibers by natural fibers. However, natural fibers obtained from plants do not present the same dimensional uniformity. In fact, they show large dispersion of values, as compared to synthetic fibers. In the case of the lignocellulosic fiber extracted from the pineapple leaf, limited information exists regarding the correlation between its properties and dimensional characteristics. In particular, so far, no investigation has been carried out on the influence of the diameter and the density of pineapple fibers. Therefore, the objective of this work was to measure the density of pineapple fibers and to define, by means of the Weibull statistic method, its dependence on the corresponding fiber diameter.

Abstract: Environmental considerations in addition to technical, economical and societal benefits are contributing to promote the substitution of natural fibers for glass fiber in polymer matrix composites. However, natural fibers are heterogeneous in their dimensions, specially the cross section diameter, which plays an important role in their physical properties. The fibers extracted from the leaf of the fique plant (Furcraea andina) are a promising stiff natural fiber for composite reinforcement. In this work, a statistical analysis of the density of fique fibers using the Weibull methodology was performed. An attempt to correlate the fiber density with the diameter, precisely measured by means of a profile projector, was carried out. The results revealed an inverse dependence, adjusted to a hyperbolic equation, between the fique fiber diameter and corresponding density.

Abstract: Environmental, economical, societal and technical advantages are today favoring natural lignocellulosic fibers over glass fiber. However, natural fibers are not as uniform in their dimension and properties as compared to synthetic ones. In recent works, it was found that the variation in strength could be correlated to the diameter for several lignocellulosic fibers, including that obtained from the eucalyptus wood. The present work investigated a possible correlation of the diameter with changes in the elastic modulus of eucalyptus wood fibers. Precise measurements of the equivalent diameter, conducted in a profile projector, were correlated with the elastic modulus by means of the Weibull statistic analysis. The results showed that an inverse correlation with the diameter applies for the elastic modulus with a reasonable degree of precision. SEM observation of the eucalyptus fiber, both it its structure and fracture aspects, strongly indicates that defects and microfibrils participation could be responsible for the inverse correlation.

Abstract: To achieve sustainability in the composite industry, natural fibers must be able to replace synthetic fibers .In this work the tensile properties of sisal fibers were determined. The relationships between tensile strength, young modulus, failure to strain and gage length was studied. Also variation in tensile strength was quantified using statistical analysis. The relationship between Weibull statistics and gage length were also investigated. The strength of the sisal fiber obtained in this work was between 255-377 MPA and decreased with an increase in gage length. The Weibull modulus obtained was similar for all gage lengths and was around 2.5.

Abstract: The modern concepts of civil construction for building with a maximum of 5 stores rely on structural blocks to support part of the load. These are normally hollow parallelepiped pieces made of concrete or fired ceramic. In Brazil, the abundance and easy to mine natural clay deposits favor the use of structural blocks fabricated of fired clay ceramics. Moreover, the available wood from reforestation, as fuel for the ceramic furnaces has the advantages of a less expensive and environmentally correct source of energy. Since the main property of a structural block is its compressive strength, special care should be taken in its evaluation. The ceramic industries in Campos dos Goytacazes, traditionally involved in the fabrication of simple non-structural clay bricks, are currently interested in producing structural blocks to attend large scale governmental housing programs. In order to evaluate the mechanical performance of these structural blocks, the preset work carried out a statistical study of their compressive strength by means of the Weibull analysis together with a characterization of the precursor clay body. The results indicated that the structural blocks comply with the norm and confirmed a valid number of tested specimens.

Abstract: Zirconium dioxide is a material more and more used by technicians and dental surgeons due to its chemical composition and excellent mechanical strength. It features high biocompatibility and may be used even in 6-unit fixed dental bridges. Adhesive bonding is one of the methods used in dental applications. New generation bonding agents featuring high mechanical strength are widely available on the market. This article presents the equipment designed and manufactured to European Standards for bonded joint testing as well as specimen geometry and bonding method. Monotonic and fatigue tests of bonded joints were performed, the results were presented and Weibull analysis was performed.

Abstract: In this paper, we introduce a prediction method for air material failure prediction. Firstly, we studied the feature of air material and previous studies on its failure prediction; we then established an air materiel failure prediction model based on Weibull analysis; then we proposed methods to improve the performance of the model through data processing and model adjustment; then, we used our model to estimate the product life cycle and predict the failure of air material based on a data sample.we not only demonstrate the validity of the model and presents a weibull analysis operation steps through the case analysis. Finally, we made some conclusions of this paper and proposed some suggestions for future research.

Abstract: Gating system in a casting mold consists of a series of channels and reservoirs designed to feed molten metal to all parts of the mold cavity. The design of the system is the principle means by which the mold designer can control the rate of the metal flow and promote the desirable temperature distribution of cooling that will take place within the filled cavity. This research was conducted to determine the effects of vortex well thickness on the microstructure and mechanical properties of Aluminium LM6 in sand casting process. The experimental results show that increasing the vortex well thickness leads to a significance improvement on the flexural strength of the cast material. In addition, casting defects such as shrinkage porosity and gas porosity would be minimized as the thickness of the vortex well increases.