Experimental and numerical study of the load distribution in a ball-screw system

In this work, load distribution on ball-screw systems (BSS) is determined by experimental techniques. Two optical techniques are used: photoelasticity for stress-field measurement and the mark-tracking method for displacement-field determination. In parallel to the experimental study, finite element method (FEM) and analytical solutions are used to calculate the loads applied on each ball of the BSS. Experimental results are used to validate the choice of boundary conditions and contact conditions between ball-screw and ball-nut in the FEM solution. The validation criterion is the correspondence between numerical and experimental fringes representing the differences of principal stresses. In addition to the study of load distribution, this paper presents the influence of the angle of contact direction on the stress distribution in BSS.     

Fuzzy energy management of hybrid renewable power system with the aim to extend component lifetime

In this paper, a fuzzy energy management algorithm for a hybrid renewable power system based on lifetime extending is presented. When the system contains two storage elements or more, the selection of the suitable element to be charged or discharged becomes of paramount importance. When the storage elements are of different types, the decision will be difficult. Conventional algorithms that make series of tests to select the storage element choose always the first available element. This way of testing affects badly the most used element and may affect the other storage elements too as they rarely operate under hard load scenarios. In this study, and in order to solve this problem, two fuzzy controllers have been used to manage the energy flow for a hybrid renewable power system. It is composed of: a photovoltaic generator as a main source, a fuel cell and batteries as a storage elements. The controllers operate as master and slave. The master controller gives orders to all the system power converters and to the slave controller as well. The latter is activated only when the storage elements are at the same state of charge. It is charged, instead of the master's, to select the suitable element to be charged or discharged. Its orders are given based on lifetime functions for each element. To examine the proposed algorithm, simulations have been performed under Matlab /Simulink (The MathWorks, Inc., Massachusetts, USA). Comparison and statistics have been carried out to give the percentage of the worked hours for each element in each operating mode. The obtained results show the high performance of the proposed algorithm. Copyright © 2017 John Wiley & Sons, Ltd.     

Constitutive model of micromechanical damage to predict reduction in stiffness of a fatigued SMC composite

Elastic behavior of sheet molding compound (SMC) composites with a given orientational distribution of fibers under cyclic loading is investigated herein. Fatigue tests were carried out over various strain ranges. During each test, evolution of Young’s modulus was measured and the composite was analyzed using scanning electron microscopy. Observations revealed the principal form of degradation to be matrix fiber debonding. A constitutive model that takes into account the reduction of overall elastic properties, i.e., Young’s modulus, was developed. This model uses a Mori-Tanaka mean field approach coupled with a micromechanical damage law. The energetic failure criterion and the failure probability are functions of local shear and normal stresses calculated at each point of the interface of each fiber family. A procedure for identifying the most appropriate material parameters is described in detail. The proposed model agrees well with the experimental results.     

Injection molded composites of short Alfa fibers and biodegradable blends

Fully biodegradable composites made from two polymer blend matrices (SEVA‐C: starch and a copolymer of ethylene vinyl alcohol; and SCA: starch and cellulose acetate) and short Alfa fibers were developed and processed by conventional injection molding into standard tensile specimens. For each kind of matrix, the influence of the reinforcement load was evaluated, using fiber amounts from 0 to 30% (wt/wt). An optimization study was carried out for the composite SEVA‐C with 10% Alfa fiber. The obtained results establish that the produced biodegradable composites present a significant improvement in stiffness for both matrices. Improvements in the tensile strength were observed only for the Alfa fiber reinforced SEVA‐C. However, for both matrices, the reinforcement causes a significant loss in the material ductility. Results from design of experiments (Hadamard plans) were used to explain the influence of the injection molding conditions on the mechanical behavior of the obtained composites, mainly on the stiffness values. POLYM. COMPOS., 27:341–348, 2006. © 2006 Society of Plastics Engineers     

Phenolic compounds and the colour of oranges subjected to a combination treatment of waxing and irradiation

The effects of waxing, irradiation doses and storage on phenolic compounds and colour of irradiated oranges were investigated. Mature oranges (Citrus sinensis (L) Osbeck var Maroc late) waxed or unwaxed were treated with 0, 1 or 2 kGy radiation and stored up to 9 weeks at 20 °C and 40–50% RH. Colour of the oranges, total phenols and flavones in the peel were measured. Phenolic compounds increased with irradiation dose and storage time. Hue angle, L* value and chroma of the orange colour were more affected by waxing and storage time than the irradiation treatment. Changes in the phenolic compounds were linked with changes in the redness and saturation of the orange colour. Irradiation stimulated synthesis of flavones; waxing controlled changes induced by irradiation. These results may aid in maintaining the quality and safety of oranges during storage. Copyright © 2004 Society of Chemical Industry