Reliability analysis of structural ceramic components using a three-parameter Weibull distribution

Described here are nonlinear regression estimators for the three-Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data

Reliability analysis of laminated CMC components through shell subelement techniques

An updated version of the integrated design program Composite Ceramics Analysis and Reliability Evaluation of Structures (C/CARES) was developed for the reliability evaluation of ceramic matrix composites (CMC) laminated shell components. The algorithm is now split into two modules: a finite-element data interface program and a reliability evaluation algorithm. More flexibility is achieved, allowing for easy implementation with various finite-element programs. The interface program creates a neutral data base which is then read by the reliability module. This neutral data base concept allows easy data transfer between different computer systems. The new interface program from the finite-element code Matrix Automated Reduction and Coupling (MARC) also includes the option of using hybrid laminates (a combination of plies of different materials or different layups) and allows for variations in temperature fields throughout the component. In the current version of C/CARES, a subelement technique was implemented, enabling stress gradients within an element to be taken into account. The noninteractive reliability function is now evaluated at each Gaussian integration point instead of using averaging techniques. As a result of the increased number of stress evaluation points, considerable improvements in the accuracy of reliability analyses were realized

Parental Unemployment, Social Insurance and Child Well-Being across Countries

Based on a unique repeated cross-sectional data set of school-aged children in Europe, the Middle East and North America, we analyze how children’s subjective well-being is related to parents’ employment status, depending on the institutional context. We find that parental unemployment is strongly negatively related to children’s life satisfaction across countries and years. The effect is thereby moderated by the generosity of unemployment benefits. Exploiting across- and within-country variation, our results suggest that a higher benefit replacement rate alleviates the negative effects of fathers’, but not mothers’, unemployment. We further test the robustness of our results considering unemployment benefits jointly with social work norms. While the buffering effect of unemployment insurance remains, the spillover effects of paternal unemployment seem to be more pronounced in environments with stricter social work norms

Dynamic Response Of Plates Due To Moving Loads

An analysis based on linear theory is presented for determining the dynamic response and the conditions of resonance for a simply supported rectangular plate acted upon by two types of moving loads corresponding to: (1) a point force of variable magnitude oscillating about a fixed position on the plate, and (2) a point force of constant magnitude traveling in a circular orbit about a fixed position on the plate. In addition to the ordinary resonance as produced by a variable magnitude load concentrated at a fixed position on the plate, resonance of the plate may occur due to the changing position of the load on the plate. It is shown that an infinitely countable number of load movement frequencies may excite a given principal frequency of the plate for the m, nth mode of vibration. Numerical examples of typical deflection profiles and time rate of deflection buildup are presented for two sets of initial conditions corresponding to: (1) a load initially at rest on the deflected beam, and (2) an accelerating load dropped from zero height on an initially undeformed beam. © 1967, Acoustical Society of America. All rights reserved

Reliability Analysis of Structural Ceramic Components Using a Three-parameter Weibull Distribution

This paper describes nonlinear regression estimators for the three-parameter Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data

Parameter estimation techniques based on optimizing goodness-of-fit statistics for structural reliability

New methods are presented that utilize the optimization of goodness-of-fit statistics in order to estimate Weibull parameters from failure data. It is assumed that the underlying population is characterized by a three-parameter Weibull distribution. Goodness-of-fit tests are based on the empirical distribution function (EDF). The EDF is a step function, calculated using failure data, and represents an approximation of the cumulative distribution function for the underlying population. Statistics (such as the Kolmogorov-Smirnov statistic and the Anderson-Darling statistic) measure the discrepancy between the EDF and the cumulative distribution function (CDF). These statistics are minimized with respect to the three Weibull parameters. Due to nonlinearities encountered in the minimization process, Powell's numerical optimization procedure is applied to obtain the optimum value of the EDF. Numerical examples show the applicability of these new estimation methods. The results are compared to the estimates obtained with Cooper's nonlinear regression algorithm

Electric-field induced capillary interaction of charged particles at a polar interface

We study the electric-field induced capillary interaction of charged particles at a polar interface. The algebraic tails of the electrostatic pressure of each charge results in a deformation of the interface $u\sim \rho ^{-4}$. The resulting capillary interaction is repulsive and varies as $\rho ^{-6}$ with the particle distance. As a consequence, electric-field induced capillary forces cannot be at the origin of the secondary minimum observed recently for charged PMMA particles at on oil-water interface.Comment: June 200

On-Line Process Fiber Optic Refractometer for Measuring Edible Oil Hydrogenation

The process of edible oil partial hydrogenation has improved steadily over the past decades, but few on-line process instruments exist capable of measuring the extent of hydrogenation. This work describes the design of a prototype, on-line fiber optic refractometer for controlling and monitoring of oils. It uses an established correlation between the degree of hydrogenation of an edible oil and its refractive index (Rl). The refractometer cell uses a bare optical fiber in direct contact with processing oil. Equations are given describing the power transmission characteristics of an optical fiber as a function of its cladding Rl. Comparisons between calculated and experimental data are shown using test liquids flowing through the refractometer

Rate of development of predatory insects is dependent on that of their prey

In this study we analyzed data in the literature on the rates of development of parasitoids that parasitize aphids and coccids. The objective was to determine whether their rates of development, as is well documented for ladybirds, are also dependent on that of their prey. The analysis revealed that, like ladybirds, parasitoids that parasitize aphids develop faster than those that parasitize coccids. Parasitoids and ladybird predators show the same pattern in their rates of development: those attacking aphids develop faster than those attacking coccids. This is strong evidence that we are dealing with a general response rather than one specific to ladybirds. It also lends support to the concept that the development rates of these natural enemies are evolutionarily conserved rather than phylogenetically constrained