Uncertainty treatment in forced response calculation of mistuned bladed disk

Mistuning, imperfections in cyclical symmetry of bladed disks is an inevitable and perilous occurrence due to many factors including manufacturing tolerances and in-service wear and tear. It can cause some unpredictable phenomena such as mode splitting, mode localization and dramatic difference in forced vibration response. In this paper first, a method is presented which calculates the forced vibration response of a mistuned system based on an exact relationship between tuned and mistuned systems. Then, the genetic algorithm is used for solving an optimization problem to find the worst-case response of bladed-disk assembly. The second part tries to find methods to reduce the system worst-case response. Intentional mistuning which breaks the nominal symmetry of a tuned bladed disk and rearranging the bladed-disk assembly are introduced and used to reduce the system worst-case response. Finally, a two degree of freedom per blade simplified model with 56 blades is used to demonstrate the capabilities of the techniques in reducing the worst response of the bladed-disk system.     

Brittle fracture assessment of engineering components in the presence of notches: a review

Brittle fracture of notched components has been widely investigated in recent decades both experimentally and theoretically. This is because of designers' concern about catastrophic failure in notched engineering components made of brittle or quasi‐brittle materials. Up to now, extensive studies have been performed on brittle fracture analysis of engineering components weakened by notches of various features under mode I, mode II, mode III and mixed mode loading conditions. In the present paper, the attempt is made to review the research articles published in the open literature on brittle fracture assessment of notched components by means of notch fracture mechanics concepts. The main focus of this paper is on the stress‐based fracture criteria, which are the basis of authors' experience in recent years.     

Human perception of robot safe speed and idle time

Operators and users of robotic systems perform tasks which require close proximity to dangerous moving parts. Two experiments were performed to assess human perception of safe robot arm speed and idling times. Experiment 1 was designed to determine the maximum safe speed of robots. Subjects were asked to adjust the robot speeds. Perceived safe speeds were indicated for two different types of robots. Experiment 2 was designed to determine safe programmed idle time of robots. Subjects were asked to enter the robot work envelope when a programmed idle was perceived to be caused by a malfunction. Safe idle times were reported for two different robot speeds during operational cycles.     

An investigation of the amount of lead in blood of Tehran citizens in 1980–1981

A simple atomic absorption method for lead analysis is described; more than 830 samples of inhabitants on the basis to their age, sex, occupation and residential locations were collected for a period of one year (March 1980‐February 1981) and the results of analysis are given.     

Plastic limit load of cylindrical shells with cutouts subject to pure bending moment

In this paper, the results of limit analyses of thin-walled cylindrical shells with a circular hole under the action of a pure bending moment are presented in dimensionless form for a wide range of geometric parameters. Analytical estimation of lower bound limit load is carried out using the feasible sequential quadratic programming (FSQP) technique. The finite element calculations of limit load consist of elastic–plastic and lower and upper bound predictions by elastic compensation methods. A testing device was made to perform experiments to obtain limit bending moment of cylinders with circular openings. The analytical and finite element calculations are compared with experimental results and their correlation is discussed. The finite element calculation results were found to be in good agreement with lower bound estimations by the nonlinear mathematical programming (FSQP) method and the formula proposed by Shu.     

Microwave-assisted encapsulation of citric acid using hydrocolloids

This study elucidates the capability of a novel technique for producing microcapsules at an enormously short time and low cost. This technique is based on the difference between dielectric constants of core and coat materials. Edible citric acid was mixed with various biomacromolecules at ratios of 1:5, 1:10, and 1:100. Each mixture was treated up to 600 s at various powers (120–1200 W) in a microwave oven. Subsequently, the microcapsules were separated by distinct sieves, and their apparent structure and quality were evaluated using binoculars, and photographs were taken for visual comparisons. Our observations showed that only five hydrocolloids were able to produce high-quality and efficient encapsulation [casein > inulin > carboxymethylcellulose (CMC) > low methoxyl (LM) pectin (9/5%) > sorbitol]. Moreover, the highest coating efficiency was seen at highest intensity (1200 W) at a mixing ratio of 1:10. Furthermore, the optimum treating time periods for those five efficient coating materials were about 400, 75, 400, 100, and 100 s.     

PRELIMINARY PHASE DIAGRAMS FOR BITUMEN/ HEAVY OILS AND RELATED MIXTURES

ABSTRACT

The phase behaviour of heavy oil mixtures was studied using an X-ray imaging system. Batch phase experiments were performed at temperatures and pressures up to 725 K and 7 MPa. Complex phase behaviour such as liquid-liquid-vapour and solid-liquid-liquid-vapour were observed and preliminary experimental phase diagrams were constructed. This observed complex phase behaviour is consistent with thermodynamic theory and such phase behaviour can be modelled using the Peng-Robinson equation of state and the tangent plane criterion. These latter points are illustrated through the phase diagram for a model reservoir fluid (ethane + propane + n-butane + phenanthrene) which exhibits solid-liquid-liquid-vapour phase behaviour. Example predicted and experimental phase diagrams are presented for this model system.     

EIS study of corrosion behavior of metallic materials in ethanol blended gasoline containing water as a contaminant

In the present paper, the effects of ethanol as a gasoline additive and water as a contaminant on the corrosion behavior of metallic components of a fuel delivery system were investigated. Electrochemical impedance spectroscopy (EIS) testing was performed in both water-free and water contaminated gasoline containing 0%, 5%, 10% and 15% ethanol without the addition of any supporting electrolyte. The surface of the specimens examined in 10% ethanol blended gasoline was observed by scanning electron microscope to understand what types of corrosion attack occurred. The results revealed that the addition of ethanol to gasoline fuel decreased the solution resistance and polarization resistance values of the specimens, resulting in an increase in the corrosion rates of these specimens in ethanol blended gasoline. Water contaminant caused a decrease in the polarization resistance of the ferrous specimens, whereas the observed behavior in others was reversed. Among the investigated metallic materials, the brazing alloy fared the best while Al 6061 alloy showed satisfactory corrosion resistance compared to the rest of the materials in both water-free and water-contaminated ethanol blended gasoline. Moreover, no localized attack was observed in corrosion products.