A generic hybrid model for bulk elastodynamics, with application to ultrasonic nondestructive evaluation

Practical ultrasonic inspection requires modeling tools that enable rapid and accurate visualization; because of the increasing sophistication of practical inspection, it is becoming increasingly difficult to use a single modeling method to represent an entire inspection process. Hybrid models that utilize different or interacting numerical schemes in different regions, to use their relative advantages to maximal effect, are attractive in this context, but are usually custom-made for specific applications or sets of modeling methods. The limitation of hybrid schemes to particular modeling techniques is shown here to be related to their fundamental formulation. As a result, it becomes clear that a formalism to generalize hybrid schemes can be developed: an example of the construction of a generic hybrid modeling interface is given for the abstraction of bulk ultrasonic wave phenomena, common in practical inspection problems. This interface is then adapted to work within a prototype hybrid model consisting of two smaller finite element model-domains, and explicitly demonstrated for bulk ultrasonic wave propagation and scattering examples. Sources of error and ways to improve the accuracy of the interface are also discussed.     

A discrete-time Bayesian network reliability modeling and analysis framework

Dependability tools are becoming an indispensable tool for modeling and analyzing (critical) systems. However the growing complexity of such systems calls for increasing sophistication of these tools. Dependability tools need to not only capture the complex dynamic behavior of the system components, but they must be also easy to use, intuitive, and computationally efficient. In general, current tools have a number of shortcomings including lack of modeling power, incapacity to efficiently handle general component failure distributions, and ineffectiveness in solving large models that exhibit complex dependencies between their components. We propose a novel reliability modeling and analysis framework based on the Bayesian network (BN) formalism. The overall approach is to investigate timed Bayesian networks and to find a suitable reliability framework for dynamic systems. We have applied our methodology to two example systems and preliminary results are promising. We have defined a discrete-time BN reliability formalism and demonstrated its capabilities from a modeling and analysis point of view. This research shows that a BN based reliability formalism is a powerful potential solution to modeling and analyzing various kinds of system components behaviors and interactions. Moreover, being based on the BN formalism, the framework is easy to use and intuitive for non-experts, and provides a basis for more advanced and useful analyses such as system diagnosis.     

Optical modeling of Fresnel zoneplate microscopes

Defect free masks remain one of the most significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. Progress on this front requires high-performance wavelength-specific metrology of EUV masks, including high-resolution and aerial-image microscopy performed near the 13.5?nm wavelength. Arguably the most cost-effective and rapid path to proliferating this capability is through the development of Fresnel zoneplate-based microscopes. Given the relative obscurity of such systems, however, modeling tools are not necessarily optimized to deal with them and their imaging properties are poorly understood. Here we present a modeling methodology to analyze zoneplate microscopes based on commercially available optical modeling software and use the technique to investigate the imaging performance of an off-axis EUV microscope design. The modeling predicts that superior performance can be achieved by tilting the zoneplate, making it perpendicular to the chief ray at the center of the field, while designing the zoneplate to explicitly work in that tilted plane. Although the examples presented here are in the realm of EUV mask inspection, the methods described and analysis results are broadly applicable to zoneplate microscopes in general, including full-field soft-x-ray microscopes routinely used in the synchrotron community.     

Development of Fibre Metal Laminates: concurrent multi-scale modeling and testing

Fibre Metal Laminates (FML) represent a family of hybrid materials, consisting of alternating layers of thin metal sheets and fibre reinforced epoxies. The concept, invented in the late 1970s, has resulted in laminates like ARALL and GLARE. The first material is made of aluminum alloys, aramid fibres and an epoxy resin, GLARE laminates use similar constituents except for the aramid fibres, which are replaced by glass fibres. Besides, a specific laminate is determined by its layer thickness, fibre orientation, number of layers, etc., parameters, which can be regarded as variables. The first large scale application of the GLARE laminates is the fuselage of the Airbus A-380 aircraft. Large sections of the fuselage, both in the front and aft section will have a GLARE skin and some local GLARE doublers. Before this material could be applied to the A-380, it took more than 20 years of research and development, and the R&D is still continuing. The research that is performed is a mixture between testing and modeling: testing is necessary for the optimization of the laminates, and a lot of test evidence is required for certification and qualification purposes. In addition also analytical and numerical tools have been developed to limit the number of tests, to determine design allowables, and to predict the material behavior in a multitude of structural applications and details. Current and future research on FML has at least two objectives. On one hand the research is focused on generating new laminates based on the same concept, on the other hand the modeling is advancing in order to improve existing models and to develop new ones (tools for the analysis of structures). The tendency for the modeling is from macro-scale towards meso- and even micro-scale modeling. From the modeling and experimental point of view these hybrid materials, mixtures of metal and composite layers, offer specific challenges. Since fibres are embedded in the matrix and the materials have a layered structure, typical composite characteristics and failure modes are involved like anisotropy, fibre–matrix interfaces, matrix cracking, and delamination. On the other hand due to the metal constituents the laminates show plastic behavior and have discrete interfaces between the metal and the resin. In this paper an overview is presented of the research and development of FML, in particular the development of GLARE. The emphasis in this overview will be on the understanding and analysis of these laminates, and the development of appropriate tools (models). Over the years the development was a concurrent one: both testing and modeling were performed simultaneously. Special attention will be paid on the current and future research that is planned for a further understanding of this structural material. This research is dominated by numerical calculations and simulations and is aiming for topics like the prediction of the fracture energy, the crack bridging effect, and the blunt notch behavior of laminates.     

Integrated analysis of the performance of TQM tools and techniques: a case study in the Taiwanese motor industry

Most studies of total quality management (TQM) have focused on the managerial aspects and associated success factors of TQM programmes, whereas relatively few studies have examined the appropriateness and performance of the large number of available tools and techniques that actually implement TQM practices. To assist in determining the best strategy for improving the performance of TQM tools and techniques, the present study integrates a modified importance–performance matrix with elements of failure mode and effects analysis (FMEA) to provide a comprehensive methodology for assessing and improving the performance of TQM tools and techniques in the Taiwanese motor industry. The methodology presented here can be applied in a variety of industries, including the Taiwanese motor industry, to enable efficient utilisation of TQM tools and techniques and thus improve quality, reduce costs and shorten cycle times.     

Heat-sealing integrity assessment through nondestructive evaluation techniques

Sealing is a critical step in different packaging industries. In heat sealing as one of the major types of sealing processes, two layers of materials (typically thermoplastics) are joined together through the application of heat and pressure load for a certain sealing time. Due to the capabilities of the heat-sealing process to seal different kinds and sizes of packages, it has a wide range of applications in many different industries such as the packaging of food and medical products. The quality and integrity of sealings produced by these techniques are crucial for the quality and safety of the contained materials. In this paper, different types and processes of sealing are discussed. Due to the variations in shape, size, and complexity of the sealing region, quality testing and inspection of these products is a challenging task. Nondestructive testing and evaluation (NDTE) techniques can be promising tools to overcome these challenges. Furthermore, a detailed study of various types of potential defects and their generation mechanism in heat sealing is presented. Then, various types of NDTE techniques that can be potentially used for the inspection of heat-sealing regions and their working principles, as well as their strength and weakness in sealing inspection, are debated. Finally, several cases of sealing inspection and relevant NDTE techniques that are developed as standard procedures are presented. The discussions in this study provide useful information for the selection and implementation of appropriate quality inspection and inline quality monitoring of sealing parts and processes.     

Sparse Representations to Replace TOFD Images in Non-destructive Testing of Materials

This paper describes a proposed method for the selection of relevant samples of ultrasonic signals during automatic material inspection. Instead of the well-known time of flight diffraction (TOFD) images, data are stored as a sparse matrix in which the elements only indicate whether a defect has been detected. This technique avoids storage of useless signals received during probe displacement in cases of low and high signal-to-noise ratios that correspond to coarse-grained and fine-grained materials, respectively. The approach is based on comparing the positions of maximum amplitudes, which are randomly located when signals only consist of noise but are in the same signal range when a defect is detected. The matrix elements are then applied as inputs to a self organizing map by neural networks to produce a normalized sparse matrix as the output, with a constant number of elements. This approach will be beneficial to enable the use of selected data in intelligent systems requiring a fixed number of inputs to characterize defects.     

Iterative scenario based reduction technique for stochastic optimization using conditional value-at-risk

In the last decades, several tools for managing risks in competitive markets, such as the conditional value-at-risk, have been developed. These techniques are applied in stochastic programming models primarily based on scenarios and/or finite sampling, which in case of large-scale models increase considerably their size according to the number of scenarios, sometimes resulting in intractable problems. This shortcoming is solved in the literature using (i) scenario reduction methods, and/or (ii) speeding up optimization techniques. However, when reducing the number of scenarios, part of the stochastic information is lost. In this paper, an iterative scheme is proposed to get the solution of a stochastic problem representing the stochastic processes via a set of scenarios and/or finite sampling, and modeling risk via conditional value-at-risk. This iterative approach relies on the fact that the solution of a stochastic programming problem optimizing the conditional value-at risk only depends on the scenarios on the upper tail of the loss distribution. Thus, the solution of the stochastic problem is obtained by solving, within an iterative scheme, problems with a reduced number of scenarios (subproblems). This strategy results in an important reduction in the computational burden for large-scale problems, while keeping all the stochastic information embedded in the original set of scenarios. In addition, each subproblem can be solved using speeding-up optimization techniques. The proposed method is very easy to implement and, as numerical results show, the reduction in computing time can be dramatic, and more pronounced as the number of initial scenarios or samples increases.     

连续纤维增强陶瓷基复合材料微观力学研究进展

微观力学参数是构建连续纤维增强陶瓷基复合材料(CFRCMCs)组分、微观结构和宏观力学性能的桥梁, 但受限于CFRCMCs的脆性和微观力学参数测试水平, 微观力学研究工作进展缓慢。随着基于纳米压痕的微观力学测试技术和基于聚焦离子束微观测试样品制备技术的飞速发展, 近年来CFRCMCs的微观力学研究工作取得显著进步。本文结合国防科技大学刘海韬课题组的研究工作, 重点对CFRCMCs组分的原位模量、断裂韧性以及界面结合强度的测试方法和典型应用进行了讨论, 最后举例说明了基于微观力学参数的CFRCMCs宏观力学行为的预判方法。     

Business improvement tools and techniques: a comparison across sectors and industries

The purpose of this study was to investigate the awareness, usage, perceived effectiveness and potential future use of improvement tools and techniques via two sets of comparisons: between public and private sector organisations, and between manufacturers and service organisations. The need for the study was driven by the current lack of understanding of the extent of improvement tools and techniques adoption on a global scale. A questionnaire survey of 453 respondents from over 20 countries was conducted and the quantitative data were analysed through use of the IBM SPSS software package. The study’s findings indicated that there are no significant differences between both sets of organisations for the majority of improvement tools and techniques. However, this study has shown that public sector organisations are more likely to adopt some improvement tools and techniques in comparison to their private sector counterparts. Similarly, service organisations are also more likely to adopt some improvement tools and techniques than their manufacturing counterparts. These results contradict the conventional perception that improvement tools and techniques are used more often by the private sector and manufacturing organisations.     

Strategies for planning experiments using orthogonal arrays and confounding tables

Genichi Taguchi has popularized a robust design method which employs experimental design techniques to help identify the levels of design factors to improve the quality of products and manufacturing processes. Experimental design techniques are extremely effective for identifying improved factor levels in problems that involve a large number of factors. Taguchi's success in getting engineers to use experimental design techniques is due, at least in large part, to his use of tools and techniques that simplify the experiment planning process. Recognizing the advantages of this approach, this paper proposes a new set of tools, confounding tables, which offer more guidance to experimenters. Confounding tables provide a clear and systematic representation of confounding relationships. They are simple and useful tools for constructing experiment plans, and they enable users easily to evaluate the confounding patterns of a completed plan. We show how confounding tables provide more information than Taguchi's linear graphs, and are useful for a large class of experiment plans.     

Micromechanical modeling approaches for the stiffness and strength of knitted fabric composites: a review and comparative study

Knitted fabric reinforced composites have been investigated widely in recent years. A number of different micromechanical modeling schemes have been proposed in the published literature for various types of knitted fabric composites. However, to date, no comparative study has been made to evaluate the suitability of different modeling schemes to predict the stiffness and strength properties of knitted fabric composites. This paper presents a review of currently developed micromechanical modeling techniques for predicting the stiffness and strength of knitted fabric composites. Further, a comparative study of the predictive capabilities of various techniques is carried out based on a plain weft knitted glass fiber fabric reinforced epoxy matrix composite. Useful conclusions are drawn based on the comparative study.     

On the characterisation of grown-in defects in Czochralski-grown Si and Ge

High yield processing of advanced integrated devices poses stringent demands on substrate and active device layer quality. Wafers have to be free of electrically active defects and should therefore be free of so called large pit defects and Crystal Originated Particles (COP’s) which can be formed during Czochralski (Cz) crystal growth. These COP’s are surface pits formed by large vacancy clusters and are observed by surface inspection tools based on light scattering as “particles”. They are formed by vacancy clustering during crystal growth. In Cz Si these defects can also be observed inside the bulk of the material by using infra red light scattering tomography and transmission electron microscopy. Recently similar defects were observed on polished Cz Ge wafers using optical and scanning electron microscopy and the same surface inspection tools as used for silicon wafers. In the present paper the characterisation of grown-in voids in Si and Ge using these various techniques is discussed. The observed void size-density distributions are compared with results of the simulation of vacancy incorporation and clustering during the Czochralski growth process.     

Manufacturing‐integrated product solutions: Design support between product function and manufacturing processes

With the help of new design tools, manufacturing‐integrated solutions can be generated that concurrently consider function and process. Based on the design pattern matrix, solution elements can be developed that realize the product function by systematically utilizing manufacturing‐induced properties. The developed manufacturing‐integrated product solutions are refined using computer‐aided methods (feature‐based modeling and information modeling). A product embodiment is generated that is specifically tailored to the chosen manufacturing technology. An integrated information model allows the introduced tools to be used throughout the entire development process. The example of a linear flow split snap‐fit fastening illustrates how the tools beneficially interact and realize manufacturing potential, resulting in an innovative product design.     

Genome and proteome annotation: organization, interpretation and integration

Recent years have seen a huge increase in the generation of genomic and proteomic data. This has been due to improvements in current biological methodologies, the development of new experimental techniques and the use of computers as support tools. All these raw data are useless if they cannot be properly analysed, annotated, stored and displayed. Consequently, a vast number of resources have been created to present the data to the wider community. Annotation tools and databases provide the means to disseminate these data and to comprehend their biological importance. This review examines the various aspects of annotation: type, methodology and availability. Moreover, it puts a special interest on novel annotation fields, such as that of phenotypes, and highlights the recent efforts focused on the integrating annotations.     

半导体晶圆制造中组合设备运行和控制综述

作为半导体制造中单晶圆加工技术的可重构集成设备,组合设备在半导体产业得到越来越广泛的应用。使用组合设备使得半导体制造产出更高、生产周期更短、空间利用率更高以及生产成本更低。由于组合设备的运行受限于诸多约束条件,有效运行一台组合设备相当困难。目前已有大量的有关组合设备建模、性能分析及调度等相关研究工作。本文回顾了这些研究工作的进展及其使用的研究方法,探讨了现有的方法的优缺点。基于这些分析,指出了进一步的研究方向。     

Modeling without categorical variables: a mixed-integer nonlinear program for the optimization of thermal insulation systems

Optimal design applications are often modeled by using categorical variables to express discrete design decisions, such as material types. A disadvantage of using categorical variables is the lack of continuous relaxations, which precludes the use of modern integer programming techniques. We show how to express categorical variables with standard integer modeling techniques, and we illustrate this approach on a load-bearing thermal insulation system. The system consists of a number of insulators of different materials and intercepts that minimize the heat flow from a hot surface to a cold surface. Our new model allows us to employ black-box modeling languages and solvers and illustrates the interplay between integer and nonlinear modeling techniques. We present numerical experience that illustrates the advantage of the standard integer model.     

The Use of Ultrasonic Arrays to Characterize Crack-Like Defects

The use of ultrasonic arrays to image and size crack-like defects is an important area in non-destructive evaluation. In this paper, two approaches are considered for extracting the key parameters of crack length and orientation angle. The parameters for small cracks are inferred from the scattering matrix. For larger cracks, the parameters are extracted directly from a high resolution image. The performance of both techniques is first assessed using a hybrid model to generate the full matrix of array data for a specified inspection configuration. The model combines a ray-based propagation model with scattering matrices to describe wave interaction with a defect. Good agreement is achieved between simulated and experimental results, hence validating this model-based approach. This model is then used to assess the impact of time-domain noise on the characterisation of crack-like defects. For the low-noise case, the scattering matrix approach shows good performance if the crack length is greater than 0.2 wavelengths and the image-based approach is good for crack lengths greater than 0.5 wavelengths. The scattering-matrix-based approach is found to be more sensitive to the addition of noise than the image-based approach. Finally, both techniques are demonstrated experimentally on samples containing more realistic defects.     

Evaluation of pipeline girth welds using low-frequency horizontally polarized waves

The practical implementation of alternative acceptance criteria for pipeline girth welds requires the use of inspection tools capable of determining the principal dimensions and positions of planar flaws. A new ultrasonic inspection method is described that permits complete volumetric inspection of the girth welds. The new system uses noncontacting electromagnetic-acoustic transducers (EMATs) that operate at low ultrasonic frequencies (454 kHz). Theoretical models of the measurements are developed and verified experimentally. In addition, practical performance limits of the new system are established in terms of minimum flaw sizes that can be detected. The results are related to accept-reject curves based on a model of the failure processes. An inspection protocol for field applications is also described.     

Optimal maintenance decisions under imperfect inspection

The process industry is increasingly making use of Risk Based Inspection (RBI) techniques to develop cost and/or safety optimal inspection plans. This paper proposes an adaptive Bayesian decision model to determine these optimal inspection plans under uncertain deterioration. It uses the gamma stochastic process to model the corrosion damage mechanism and Bayes’ theorem to update prior knowledge over the corrosion rate with imperfect wall thickness measurements. This is very important in the process industry as current non-destructive inspection techniques are not capable of measuring the exact material thickness, nor can these inspections cover the total surface area of the component. The decision model finds a periodic inspection and replacement policy, which minimizes the expected average costs per year. The failure condition is assumed to be random and depends on uncertain operation conditions and material properties. The combined deterioration and decision model is illustrated by an example using actual plant data of a pressurized steel vessel.