Chan Qiu

Quantification for the importance degree of engineering characteristics with a multi-level hierarchical structure in QFD

Quantification for the importance degree of engineering characteristics (ECs) is an essential problem in quality function deployment. In real-world scenario, it is sometimes difficult to directly evaluate the correlation degree between ECs and customer requirements (CRs) as ECs are too abstract. Thus, the target ECs have to be further decomposed into several more detailed basic ECs and organised by a multi-level hierarchical structure. The paper investigates the quantification problem for the importance degree of such target ECs and tackles two critical issues. The first issue is how to deal with the uncertainties including fuzziness and incompleteness involved during the evaluation process. A fuzzy evidential reasoning algorithm-based approach is proposed to tackle this issue and derive the correlation degree between each of the basic ECs and the whole CRs. The second issue is how to deal with the interactions among the basic ECs decomposed from the same target EC during the aggregation process. A λ-fuzzy measure and fuzzy discrete Choquet integral-based approach is proposed to tackle this issue and aggregate these basic ECs. Final importance degree of the target ECs can then be obtained. At the end of this paper, a case study is presented to verify the feasibility and effectiveness of the method we propose.

Simulation-based robust design of complex product considering uncertainties of metamodel, design variables, and noise parameters

The uncertainties of design variables, noise parameters, and metamodel are important factors in simulation-based robust design optimization. Most conventional metamodel construction methods only consider one or two uncertainties. In this paper, a new surrogate modeling method simultaneously measuring all the uncertainties is proposed for simulation-based robust design optimization of complex product. The effect of metamodel uncertainty on product performance uncertainty is quantified through uncertainty propagation analysis among design variables uncertainty, noise parameters uncertainty, metamodel uncertainty, and performance uncertainty. Then, the sampling points are selected and the metamodel is constructed based on the predictive interval of product performance and mean square error of the Kriging metamodel. The constructed metamodel is applied to robust design optimization considering multiple uncertainties. Results of two mathematical examples show that the proposed metamodel considering multiple uncertainties increases the result accuracy of robust design optimization. Finally, the proposed algorithm is applied to robust design optimization of a heat exchanger, and the total heat transfer rate is enhanced under uncertainties of fin structural parameters, operation conditions parameters and simulation metamodel.

Hybrid reliability analysis with uncertain statistical variables, sparse variables and interval variables

ABSTRACT There are differences among sampling data and representation types of uncertain statistical variables, sparse variables and interval variables, which increase the complexity of structure reliability analysis. Therefore, a hybrid first order reliability analysis method considering the three types of uncertain variables is demonstrated in this article. First, distribution types and distribution parameters of sparse variables are identified and probabilistically estimated. Secondly, interval variables are transformed into probabilistic types using a uniformity approach. Thirdly, a unified hybrid reliability calculation method considering these uncertain variables simultaneously is demonstrated. The most probable point (MPP) is searched for using the first order reliability method, and then a linear approximation function of performance function is constructed in the neighbourhood of the MPP. Finally, the belief and plausibility measures of the reliability index are efficiently calculated using the theoretical analytical method. Three examples are investigated to demonstrate the effectiveness of the proposed method.

Assembly variation analysis of flexible curved surfaces based on Bézier curves

Assembly variation analysis of parts that have flexible curved surfaces is much more difficult than that of solid bodies, because of structural deformations in the assembly process. Most of the current variation analysis methods either neglect the relationships among feature points on part surfaces or regard the distribution of all feature points as the same. In this study, the problem of flexible curved surface assembly is simplified to the matching of side lines. A methodology based on Bézier curves is proposed to represent the side lines of surfaces. It solves the variation analysis problem of flexible curved surface assembly when considering surface continuity through the relations between control points and data points. The deviations of feature points on side lines are obtained through control point distribution and are then regarded as inputs in commercial finite element analysis software to calculate the final product deformations. Finally, the proposed method is illustrated in two cases of antenna surface assembly.

A real-time interactive system of surface reconstruction and dynamic projection mapping with RGB-depth sensor and projector:

Reconstruction and projection mapping enable us to bring virtual worlds into real spaces, which can give spectators an immersive augmented reality experience. Based on an interactive system with RGB-depth sensor and projector, we present a combined hardware and software solution for surface reconstruction and dynamic projection mapping in real time. In this article, a novel and adaptable calibration scheme is proposed, which is used to estimate approximate models to correct and transform raw depth data. Besides, our system allows for smooth real-time performance using an optimization framework, including denoising and stabilizing. In the entire pipeline, markers are only used in the calibration procedure, and any priors are not needed. Our approach enables us to interact with the target surface in real time, while maintaining correct illumination. It is easy and fast to develop different applications for our system, and some interesting cases are demonstrated at last.

Thermal Compensation Effect of Passage Arrangement Design for Inlet Flow Maldistribution in Multiple-Stream Plate-Fin Heat Exchanger

ABSTRACT Passage arrangement design in fin channels is an efficient methodology for the reduction of the thermal deterioration influence of inlet flow maldistribution in multiple-stream plate-fin heat exchangers. In this work, the thermal compensation effects of passage arrangement design under different statistical parameters of inlet flow maldistribution are investigated. The inlet flow maldistribution in inlet header is analyzed and represented with distribution types, mean, and standard deviation of inlet mass flow rate entering the fin channels. A thermal calculation model based on integer–mean temperature difference method is established, and then, the passage arrangement under inlet flow maldistribution is optimized using a hybrid particle swarm algorithm. The thermal compensation effects for different inlet flow maldistributions and passage arrangements are calculated and compared. The results indicate that the compensation effect of optimization design of passage arrangement increases from 1.1% to 3.9% as the standard deviation of inlet mass flow rate increases from 0.06 kg/s to 0.12 kg/s. The results presented in this study can be used by other researchers to guide the passage arrangement design of actual heat exchanger with inlet flow maldistribution.

A Rapid Design Method of Anti-deformation Fixture Layout for Thin-Walled Structures

Minimizing workpiece deformation is significant to maintain accuracy in the machining and assembly processes of metal thin-walled parts, which can be achieved by anti-deformation fixture layout design. The state-of-the-art methods of fixture layout are almost based on iterative finite element analysis (FEA), which involve high time cost. A rapid design method of fixture layout based on hybrid particle swarm optimization (HPSO) algorithm is proposed in this paper to locate thin-walled structures efficiently. On the basis of elastic plate theory, the deformations of workpieces under gravity or concentrated forces are described by expressions. Flexible tooling system is applied in positioning process and constraints between fixture elements and workpieces are obtained according to design demands. Average deformation of all measurement nodes on the metal structure along normal direction is set as objective function. Then, an optimal fixture layout scheme is designed to minimize overall deformation of thin-walled workpiece based on hybrid particle swarm optimization algorithm. Finally, the proposed method is applied to fixture layout design of thin-walled structure with simply supported edges. Compared with results of current methods, time cost of the proposed method is obviously less while keeping accuracy.

Multi-scale Simulation Method with Coupled Finite/Discrete Element Model and Its Application

The existing research on continuous structure is usually analyzed with finite element method (FEM) and granular medium with discrete element method (DEM), but there are few researches on the coupling interaction between continuous structure and discrete medium. To the issue of this coupling interaction, a multi-scale simulation method with coupled finite/discrete element model is put forward, in their respective domains of discrete and finite elements, the nodes follow force law and motion law of their own method, and on the their interaction interface, the touch type between discrete and finite elements is distinguished as two types: full touch and partial touch, the interaction force between them is calculated with linear elastic model. For full touch, the contact force is proportional to the overlap distance between discrete element and finite element patch. For partial touch, first the finite element patch is extended on all sides indefinitely to be a complete plane, the full contact force can be obtained with the touch type between discrete element and plane being viewed as full touch, then the full overlap area between them and the actual overlap area between discrete element and finite element patch are computed, the actual contact force is obtained by scaling the full contact force with a factor η which is determined by the ratio of the actual overlap area to the full overlap area. The contact force is equivalent to the finite element nodes and the force and displacement on the nodes can be computed, so the ideal simulation results can be got. This method has been used to simulate the cutter disk of the earth pressure balance shield machine (EPBSM) made in North Heavy Industry (NHI) with its excavation diameter of 6.28 m cutting and digging the sandy clay layer. The simulation results show that as the gradual increase of excavating depth of the cutter head, the maximum stress occurs at the roots of cutters on the cutter head, while for the soil, the largest stress is distributed at the region which directly contacted with the cutters. The proposed research can provide good solutions for correct design and installation of cutters, and it is necessary to design mounting bracket to fix cutters on cutter head.