On Some Finite Range Life Distributions

Various reliability properties, including some characterization results, have been investigated for two finite range life distributions. One of these, namely, the exponentiated rectangular distribution, exhibits a bath-tub failure rate when the shape parameter has a value less than unity and, as expected, does not conform to certain results relating to ageing properties, which hold in the case of distributions with monotone failure rates. Moments as well as best percentile estimates of the shape parameter for this distribution have been worked out. Stress–strength reliability when stress and strength follow the same distribution of this type over the same range, but with different shape parameter values, has been derived and shown to be related to the Bhattacharyya distance between the two probability distributions. Distributions of parallel and standby system lives for two independent components, with this distribution having varying shape parameters, have been derived.

Application Of Bias Randomization In Evaluation Of Measuring Instrument Capability

The paper deals with the problem of bias randomization in evaluation of the measuring instrument capability. The bias plays a significant role in assessment of the measuring instrument quality. Because the measurement uncertainty is a comfortable parameter for evaluation in metrology, the bias may be treated as a component of the uncertainty associated with the measuring instrument. The basic method for calculation of the uncertainty in modern metrology is propagation of distributions. Any component of the uncertainty budget should be expressed as a distribution. Usually, in the case of a systematic effect being a bias, the rectangular distribution is assumed. In the paper an alternative randomization method using the Flatten-Gaussian distribution is proposed.

The Prediction of Fixture Comprehensive Influence on the Machining Error of Features Pattern

The position and orientation deviation of workpiece caused by the fixing errors of the fixture influences the machining accuracy of workpiece. This paper presents a method of predicting the fixture induced error and its influence on the machining accuracy of features pattern. Firstly, the mathematical model for predicting fixing error caused by locators and locating surface geometrical errors and caused by clamping force and machining force is formulated. Then, based on the 3-2-1 positioning fixture, the influence of fixing errors on the machining accuracy of features pattern is analyzed after introducing the definition, inspection and evaluation method for the composite position error of features pattern. Finally, taking 4-holes pattern in rectangular distribution as an example, the process of predicting the composite positional error of features pattern is detailed and a simulation experiment is conducted. The results show the rightness and validity of this method.

An Experimental Investigation of Temperatures in Grinding of Ceramics with a Brazed Diamond Tool

An investigation is reported of the relationships of the temperatures and grinding parameter for grinding of ceramics with a brazed diamond grinding tool. During the experiments, the temperature distributions along the workpiece surface were measured using a foil thermocouples and the energy partition to the workpiece estimated using a temperature matching method. The results show that the grinding temperature increased with the increasing of worktable feed rate or tool velocity and depth of grinding. The measured temperature responses were found to be in good relation with the analytical results of a moving heat source with a rectangular distribution at the grinding zone.The energy partition ε is about 23%.

Crashworthiness optimization of new thin-walled cellular configurations

Purpose – The purpose of this paper is to optimize a new thin-walled cellular configurations with crashworthiness criteria, so as to improve the crashworthiness of components of a vehicle body. Design/methodology/approach – ANSYS Parametric Design Language is used to create the parameterized models so that the design variables can be changed conveniently. Moreover, the surrogate technique, namely response surface method, is adopted for fitting objective and constraint functions. The factorial design and D-optimal criterion are employed to screen active parameters for constructing the response functions of the specific energy absorption and the peak crushing force. Finally, sequential quadratic programming-NLPQL is utilized to solve the design optimization problem of the new cellular configurations filled with multi-cell circular tubes under the axial crushing loading. Findings – Two kinds of distribution modes of the cellular configurations are first investigated, which are in an orthogonal way and in a diamond fashion. After comparing the optimized configurations of the rectangular distribution with the annular distribution of the multi-cell fillers, it is found that the orthogonal way seems better in the aspects of crashworthiness than the diamond fashion. Originality/value – The two new thin-walled cellular configuration are studied and optimized with the crashworthiness criteria. Study on the new cellular configurations is very valuable for improving the crashworthiness of components of a vehicle body. Meanwhile, the factorial design and the factor screening are adopted in the process of the crashworthiness optimization of the new thin-walled cellular configurations.