Advanced Materials Research Vols. 199-200

Abstract: Influenced by the geometry and boundary condition’s complexity of the model, as to the heat conductor with complicated shape or non-linear boundary condition, the model must be simplified a lot, before it’s heat dissipating capacity can be calculated with the mathematic method, the course is quite complicated, and the error is large. Utilizing finite element software, an universal program has been worked out by the APDL, and it can output the heat dissipating capacity of appointed surfaces in analysis software. The program is so powerful that it can calculate the heat dissipating capacity of heat conductor in which the heat transfer two-dimensionally or three-dimensionally even if the heat conductor is anisotropic, which is difficult to calculate with the mathematic analysis method. The method mentioned in the paper can diminish the inaccuracy caused by the predigestion with the mathematic analysis method. The calculation principle of the program was introduced in detail. Comparing the result of the program with that got by mathematic method, it was indicated that the calculation error of program is smaller than 1%.

Abstract: To improve the reliability effectively, the reliability sensitivity method is researched with considering that a mechanical system or component may fail in many modes, which is simplified to be a series system model. It is supposed that all ultimate state functions in multi-failure modes are normal distribution. A computation module for total reliability is established. A kind of computation method for reliability sensitivity in multi-failure modes is built based on that in single failure mode. A pin connection component that may fail in shear fracture, bruise on pin or hole surfaces, or in any assemble with two different modes is computed, and the reliability and sensitivity of the component are estimated. Consequently, it is found that the most effective method to enhance the reliability was to enhance the crushing strength of the pin.

Abstract: K-type derrick of inclined drilling rig that is top driving is usually loaded by axial compression, lateral force and concentrated torque simultaneously, and is more prone to out-plane instability due to its poor torsional rigidity. Here the upper segment of derrick was simplified as cantilever beam-column with laced-bar lattice structure. Stability model was established by energy method, and Ritz method was employed to obtain deformation curves for lateral deflection and torsion. Effects of dip angle of derrick and position of top drive on deformation were analyzed. At last the out-plane instability process of derrick is presented by increasing longitudinal compressive force gradually. For ultimate loads of well drilling condition, out-plane stability requirement of derrick is met.

Abstract: Theories of transfer function are use to describe how to calculate random response of vehicle skeleton under road spectrum in this paper. First passage fail model combing with the basic theory of structural reliability, the calculation formula of dynamic strength reliability for vehicle skeleton is presented. Strength reliability for a bus body skeleton is solved by 13936 samples of Monte-Carlo Method when the bus is running on the C level road at a velocity of 80 km/h. The results of the numerical example show that the dynamic strength failure probability for the bus body skeleton is 8.90524×10^-4 and corresponding reliability is 99.9991095%.

Abstract: Statistic is used to calculate the reliability and maintainability of the modern aerotransport line maintance. The reliability index and the maintainability index’s chosen process and calculated process in the line maintance is given out in this paper. First the index’s choose process is given out; Second 40 modern aerotransports’ trouble shooting data from November 2007 to December 2008 is given out. According the data, the index’s calculate process is given out; Third the reliability and the maintainability require is given out according the calculate result.

Abstract: This article takes the tower crane jib as the optimized object, in view of the jib unique feature, and has established the jib quality optimization objective function, then uses amplification coefficient to obtain its membership function to the fuzzy constraint condition,thus has transformed constraint condition very well. Direct searching tool-box of MATLAB software is adopted to get the optimization model,not only is simplified the optimization process,but also global optimal solution is found reliably.

Abstract: Based on reliability analysis theory, traditional interval reliability analysis method is improved by take the smaller value of probability reliability and interval reliability as the results of reliability assessment, which makes the reliability assessment results more fit engineering cases. The improved model is applied to reliability assessment of small sample products with degradation characteristics, and results of assessment are compared with existing methods. A numerical example is considered, the results show that the assessment results by the method proposed in the paper is reasonable and believable.

Abstract: Response surface methods are often used to solve reliability analysis problems of complex engineering structure. But the solved reliability index of these methods is mostly geometric reliability. Some errors exist in geometric reliability index compared with the reliability in practical engineering which need to be improved. The importance sampling method in V-space was lead into this paper to transform the basic random variable space to V-space by Rosenblatt transformation and linear orthogonal transformation basing on the designed checking points and its nearby response surface, the complex structure reliability value was solved out by using Monte Carlo importance sampling method. The comparative analysis of several numerical examples’ results have showed that the method put forward in this paper is of high precision and suitable for the reliability solution of complex structures with strong nonlinear performance function.

Abstract: There is a growing need for improving manufacturing equipments availability to achieve high levels of productivity. As a key complement to CBM and RCM, PHM is becoming a key enabler for achieving cost effective ultra-reliability and availability in tomorrow’s manufacturing equipments at an affordable cost. Based on traditional maintenance strategies, key issues pertaining to PHM application to manufacturing equipments, including health monitoring, diagnostics and prognostics, are discussed in this paper. As an example, a method for dynamic MFOP based maintenance strategy optimization using PHM and RUL estimation is presented.

Abstract: It is the common characteristic of most engineering systems that failure statistical correlation of elements exists in the fatigue happened process due to the twin loads．Based on randomized Basquin equation，the constitutive relations between element life and twin loads，initial strength,fatigue strength exponent are established．Product-moment correlation coefficients are derived and used to quantify the dependence of logarithm life of elements．Aim at fatigue life correlation of elements in structural systems, the computation model of the system reliability is preliminarily established by means of using copula function. The new model can express the dependence of elements fatigue life in structural systems, can be used probability prediction of structural systems under common stochastic cyclic load, which gives a new path for reliability-based design and probability assesment in equipment systems with multi-mode damage coupling．