Fatigue life assessment under a complex multiaxial load history: an approach based on damage mechanics

In order to assess the fatigue behaviour of structural components under a complex (cyclic or random) multiaxial stress history, methods based on damage mechanics concepts can be employed. In this paper, a model for fatigue damage evaluation in the case of an arbitrary multiaxial loading history is proposed by using an endurance function which allows us to determine the damage accumulation up to the final failure of the material. By introducing an evolution equation for the endurance function, the final collapse can be assumed to occur when the damage D is complete, that is when D reaches the unity. The parameters of this model, which adopts the stress invariants and the deviatoric stress invariants to quantify the damage phenomenon, are determined through a Genetic Algorithm once experimental data on the fatigue behaviour of the material being examined are known for some complex stress histories. With respect to traditional approaches to multiaxial fatigue assessment, the proposed model presents the following advantages: (1) the evaluation of a critical plane is not necessary; (2) no cycle counting algorithm to determine the fatigue life is required, because it considers the progressive damage process during the fatigue load history; (3) the model can be applied to any kind of stress history (uniaxial cyclic loading, multiaxial in‐phase or out‐of‐phase cyclic loading, uniaxial or multiaxial random loading).     

A Review of Critical Plane Orientations in Multiaxial Fatigue Failure Criteria of Metallic Materials

The paper presents a review of multiaxial fatigue failure criteria based on the critical plane concept. The criteria have been divided into three groups, according to the fatigue damage parameter used in the criterion, i.e. (i) stress, (ii) strain and (iii) strain energy density criteria. Each criterion was described mainly by the critical plane orientation. Multiaxial fatigue criteria based on the critical plane concept usually apply different loading parameters in the critical plane whose orientation is determined by (a) only shear loading parameters (crack Mode II or III), (b) only normal loading parameters (crack Mode I) or sometimes (c) mixed loading parameters (mixed crack Mode). There are also criteria based on few critical plane orientations and criteria based on critical plane orientations determined by a weighted averaging process of rotating principal stress axes.     

A fracture plane approach in multiaxial high-cycle fatigue of metals

The high-cycle fatigue behaviour of metals under multiaxial loading is examined. By employing the weight function method, the authors propose to correlate the fatigue fracture plane orientation with the averaged principal stress directions. The results derived by applying such an approach are compared with the experimental data collected from the relevant literature, concerning different types of metals under in-phase or out-of-phase sinusoidal biaxial normal and shear stress states. Theoretical results determined by McDiarmid are also reported.     

Application of a systematic design methodology: an engineering case study

The basic steps of a design process have been reviewed and applied to seek an optimum solution for an industrial design problem. The problem was about a mechanical swivel-joint in a sea-current-metering system for underwater marine use. It was expensive ($200) and not functioning properly because of rattling and high friction between parts. The objective was to design another joint of better performance and lower cost, if possible. Ten steps were defined and carefully followed to solve the problem. This led to the design and production of a good quality swivel-joint as far as performance, appearance and other aspects were concerned and the cost reduced by 40%. This design method, in addition to yielding good results, is suitable for the organization of the activities of new designers and design students.     

Conceptual robustness in simultaneous engineering: An extension of Taguchi's parameter design

Simultaneous engineering processes involve multifunctional teams; team members simultaneously make decisions about many parts of the product-production system and aspects of the product life cycle. This paper argues that such simultaneous distributed decisions should be based on communications about sets of possibilities rather than single solutions. By extending Taguchi's parameter design concepts, we develop a robust and distributed decision-making procedure based on such communications. The procedure shows how a member of a design team can make appropriate decisions based on incomplete information from the other members of the team. More specifically, it (1) treats variations among the designs considered by other members of the design team asconceptual noise; (2) shows how to incorporate such noises into decisions that are robust against these variations; (3) describes a method for using the same data to provide preference information back to the other team members; and (4) provides a procedure for determining whether to release theconceptually robust design or to wait for further decisions by others. The method is demonstrated by part of a distributed design process for a rotary CNC milling machine. While Taguchi's approach is used as a starting point because it is widely known, these results can be generalized to use other robust decision techniques.     

Generic research for design of made-to-order engineering products

The paper identifies those design research issues which, while being of particular interest to the made-to-order (MTO) sector, have a wide applicability. An overview of the Newcastle EDC research programme is provided and the research topics are set in the context of two themes— design strategies and design integrity. The process of adapting the results of research aimed at producing generic results in a form suitable for application to specific product types is illustrated by describing two projects in detail. Finally, the hetrogenous nature of the Newcastle EDC environment is described and particular references are made to industrial collaboration, technology transfer, training and education.     

Practical applications of design of experiments in the field of engineering: a bibliographical review

The design of experiments (DoE) methodology is a technique that has been applied for many years in industry to improve quality. In this study, a summary of 77 cases of practical DoE application in the field of engineering is presented. All of the cases were published in important scientific journals between 2001 and 2005. The type of design that is applied, the size of the experiment, the number of factors that influence the response variable, and the sector of application of the design are analyzed. In addition, the increasing use of these designs over time is demonstrated. Copyright © 2008 John Wiley & Sons, Ltd.     

A cross-disciplinary technology transfer for search-based evolutionary computing: from engineering design to software engineering design

Although object-oriented conceptual software design is difficult to learn and perform, computational tool support for the conceptual software designer is limited. In conceptual engineering design, however, computational tools exploiting interactive evolutionary computation (EC) have shown significant utility. This article investigates the cross-disciplinary technology transfer of search-based EC from engineering design to software engineering design in an attempt to provide support for the conceptual software designer. Firstly, genetic operators inspired by genetic algorithms (GAs) and evolutionary programming are evaluated for their effectiveness against a conceptual software design representation using structural cohesion as an objective fitness function. Building on this evaluation, a multi-objective GA inspired by a non-dominated Pareto sorting approach is investigated for an industrial-scale conceptual design problem. Results obtained reveal a mass of interesting and useful conceptual software design solution variants of equivalent optimality—a typical characteristic of successful multi-objective evolutionary search techniques employed in conceptual engineering design. The mass of software design solution variants produced suggests that transferring search-based technology across disciplines has significant potential to provide computationally intelligent tool support for the conceptual software designer.     

A methodological comparison of the structures of scientific research and engineering design: their similarities and differences

The misunderstanding that engineering is just a part of science (at the most applied science) and that engineering design is only a kind of scientific research (often considered rather trivial) is still widespread, especially among scientists. Yet it is a misunderstanding. In the present paper the structures of scientific research and of engineering design will be compared and, apart from a few very evident similarities, a large number of essential differences will be discussed. The conclusions are on the one hand that science and engineering are strongly interwoven and mutually dependent on each other, but on the other hand that there are fundamental differences between scientific research and engineering design. They consequently require specific methodologies.     

A chemical engineering design view of biotechnology

The possibilities of biotechnology are being widely discussed and promoted. Because of this there will be many studies directed at evaluating biotechnology projects. At some stage this will require the generation of potential process plant designs. The paper provides an introduction to those aspects of biotechnology which will be the concern of the chemical engineer, with an emphasis on design tasks. This is supported by a commentary on the similarities with and differences from mainline chemical engineering design. In addition the principal material relating to design has been drawn together from the available literature and summarized for engineers new to the area of biotechnology.     

GPS技术在公路工程测量中的分析及应用

以公路隧道施工GPS控制网的建立及测量数据为例,在GPS控制测量的理论基础上和相关技术规范条件下,论述隧道贯通新的测量方法.对该隧道GPS平面控制网进行测量研究,介绍GPS测量中基础环境控制网的建立与布网方法,在实施处理过程中通过对GPS定位、利用Ashtech Solutions进行GPS数据采集后数据精度处理,来分析该技术在隧道贯通平面控制测量方面的实际应用方法与过程,采用点观测模式时,不同点必须采用不同基线、同步环和异步环的数据检验,在算法上采用约束平差进行误差分析与计算.该法在使用便捷和测量精度上比传统测量方法功能更强大、更精确,为后期利用GPS技术进行进行隧道贯通平面控制测量提供帮助.     

并行工程在CAD／CAM中的应用

在CIMS中应用并行工程，可以加快新产品开发速度，本文主要介绍CAD／CAPP并行工程系统和实现它的关键技术。     

风冷热泵冷热水机组的选型与工程设计

本文阐述了风冷热泵冷热水机组选型中应注意的几个方面问题,并对其在工程设计中的几个应注意事项谈了作者自己的体会.