Xiaolan Wang

Probabilistic modeling of unified S-N curves for mechanical parts:

This article aims at modeling unified S-N curves based on multifailure modes and stress ratios. Heterogeneous mixture distributions are used to describe life distribution of multifailure modes. Bayes clustering is applied to cluster failure data to avoid convergence to global optima. Derived from regression analysis, failure data are compensated by nonrandom error. The relationship between distribution parameters and stress is established, and the ultimately unified probabilistic S-N curve is modeled. Two assumptions are presented to modify an original S-N curve model with varied stress ratios. The first one is to take into account the effects of low-amplitude load “exercising,” which we call results in the “pseudo-fatigue damage.” The other one is to set up probability density function of fatigue limit considering uncertainty. Combined with material parameters modification, thus a new modified and unified S-N curves model is available for not only researchers, but engineers as well.

Research on assembly tolerance allocation and quality control based on fuzzy reliability

The enhancement between cost and reliability is the developmental direction of modern manufacturing enterprises. On the basis of fuzzy theory, the relationship among the cost of product quality loss, the reliability of the assembly dimension chain and assembly tolerance is studied together in this article. Processing cost can be considerably reduced and the target of quality engineering is realized by optimization design. As an example, a tolerance design model is determined for gear and shaft assembly. Moreover, the mathematical model of the relationship between the cost of fuzzy quality loss and the fuzzy reliability of the assembly dimension chain is determined in combination with a processing cost function. The optimistic results of key dimensions of gear and shaft assembly are identified through through orthogonal experiments. This method can facilitate product quality control by enterprises and the realization of economic targets. The study findings can also serve as references for other similar studies.

Fatigue Test Analysis of Automotive Key Parts Based on Censored Data and Small Sample Setting

The study discusses how some challenges from a small sample fatigue test can be analysed statistically and resolved. In terms of data dispersion, fatigue data are initially processed by confidence, and then, the fatigue life curve is replaced by the parabolic reliability approximation. Fatigue data under various reliability levels are obtained. Instead of the traditional single S–N curve, the mean value curve and mean square deviation curve of the S–N curve are computed based on the processed fatigue data. The S–N curve with reliability is deduced by applying quantile theory. The S–N curve is improved by considering the effects of low-amplitude load strengthening. The benefits of the modification are visible in the comparison of the fatigue life before and after low-amplitude load strengthening. Copyright

Hidden quality cost function of a product based on the cubic approximation of the Taylor expansion

The-Nominal-The-Best (N-type) loss function is established based on the Taylor expansion. Results become more accurate as more Taylor expansion items are retained. N-type loss function neglects terms with powers higher than two, which inevitably leads to a certain deviation between the calculated result and the true value. In this paper, Taylor expansion is retained to the third-order, and the quality loss function is extended to three items. The quality loss coefficients of each item are determined, and the asymmetric piecewise cubic quality loss function is established. The deviation between the cubic and quadratic functions is evaluated. The formula for calculating the hidden quality cost of a product is derived by choosing an appropriate density distribution function and using process capability. Two cases are utilised to analyse and discuss the quality loss and hidden quality cost of a product using the cubic quality loss and quadratic quality loss functions. This paper provides a more accurate approach for the study of product quality management.

Parameter distribution characteristics of material fatigue life using improved bootstrap method

The bootstrap method is mostly used to estimate statistical characteristics of small sample data. However, the limitations of the bootstrap method itself lead to a reduction in the reliability of small-sample estimates. In this article, an improved bootstrap method is developed to address this problem. In the statistically significant error range (the sample average error and the limit error of sampling) of the original single sample data, expanding the virtual test data that obey two distributions to overcome the limitations of the bootstrap method itself. This article compares and analyses these two methods through the case; the result indicates that the improved bootstrap method can enhance the reliability of the estimation results without changing its probability distribution. We also discussed how to reduce the fluctuation of the improved bootstrap method. And the effectiveness and feasibility of this improved method are discussed in the analysis of fatigue life test data.

Investigation on acoustic energy harvesting based on quarter-wavelength resonator phononic crystals:

This article presents the development of an acoustic energy harvester using a quarter-wavelength resonator phononic crystals together with piezoelectric vibrators. The quarter-wavelength resonator phononic crystals consist of a main wave duct, several quarter-wavelength resonators, and equivalent piezoelectric vibrators. The acoustic energy is converted to mechanical energy when the sound incident in the quarter-wavelength resonator generates an oscillatory pressure as of localization efficiency, which in turns causes piezoelectric vibrators vibrating. Transfer matrix method is used to provide a physical insight into the structure band of the quarter-wavelength resonator phononic crystals, and finite element method is used to analyze the sound localization effect and evaluate the reclaimed energy of the quarter-wavelength resonator phononic crystals. Results indicate that the numerical analysis agrees well with experiments. When the frequencies of the incident sound are near both sides of the bandgap, the maximum output voltage always can be obtained.

Research on Load Spectrum Construction of Bench Test Based on Automotive Proving Ground

The fatigue failure of automobile structures has drawn much attention recently in reliability and endurance design. Therefore, in order to predict the fatigue life accurately, complex variable-amplitude loads must be compiled into the appropriate load spectrum. The rain-flow counting method is adopted to extract the load cycles from the random loads. A statistical method based on the mixture distribution model is proposed to analyze the multimodality of load cycles. Meanwhile, the collected random loads are extrapolated to the full life of vehicles based on the Peaks-Over-Threshold model. Finally, the one- and two-dimensional load spectrums are compiled according to the load cycles and joint probability density.

Research on Load-Spectrum Construction of Automobile Key Parts Based on Monte Carlo Sampling

Load spectrum is a decisive factor that is used to analyze fatigue, reliability, and durability of components. In this article, the typical load spectrum of proving ground is collected through load measurement equipment. Load-spectrum preprocessing, including spikes filter, signal denoising, and low-amplitude load elimination, are completed. According to parts correlation of automotive transmission systems, the load transmission route is established. The Monte Carlo sampling is applied to analyze interference of random factors in the process of load transfer route. Load spectrum of key parts of the automobile is determined and thus rain flow counting analysis is scheduled. A non-parametric method is used to complete load-spectrum extrapolation. Eventually, one-dimensional and two-dimensional programming load spectrums are built. The technical basis for fatigue life prediction and references for other similar researches are provided in this article.

Reliability analysis on the drive system of a gear-type oil pump with variable displacement

The service life of a gear-type oil pump with variable displacement is affected by the reliability of its drive system. To analyse the reliability of the drive system and improve the service life of the oil pump, a virtual prototype model was established based on real conditions and multi-body dynamic theory. The model was validated according to bench test results. And simulation results were in good agreement with test results. A numerical method was used to simulate the dynamics model and the dynamic meshing forces of gear pairs were obtained. A reliability evaluation model of the drive system was built. The reliability of each part and the entire drive system were calculated. And system reliability was analysed and discussed when 45 steel or 40Cr was utilised as the material for the drive system. The results provided a foundation for the reliability design and the dynamic optimisation of a gear-type oil pump with variable displacement.