An assessment of the kernel‐distance‐based multivariate control chart through an industrial application

Traditional multivariate quality control charts assume that quality characteristics follow a multivariate normal distribution. However, in many industrial applications the process distribution is not known, implying the need to construct a flexible control chart appropriate for real applications. A promising approach is to use support vector machines in statistical process control. This paper focuses on the application of the ‘kernel‐distance‐based multivariate control chart’, also known as the ‘k‐chart’, to a real industrial process, and its assessment by comparing it to Hotelling's T² control chart, based on the number of out‐of‐control observations and on the Average Run Length. The industrial application showed that the k‐chart is sensitive to small shifts in mean vector and outperforms the T² control chart in terms of Average Run Length. Copyright © 2010 John Wiley & Sons, Ltd.     

Fracture toughness and growth of short and long fatigue cracks in ductile cast iron EN‐GJS‐400‐18‐LT

Heavy components of ductile cast iron frequently exhibit metallurgical defects that behave like cracks under cyclic loading. Thus, in order to decide whether a given defect is permissible, it is important to establish the fatigue crack growth properties of the material. In this paper, results from a comprehensive study of ductile cast iron EN‐GJS‐400‐18‐LT have been reported. Growth rates of fatigue cracks ranging from a few tenths of a millimetre (‘short’ cracks) to several millimetres (‘long’ cracks) have been measured for load ratios R=?1, R= 0 and R= 0.5 using a highly sensitive potential‐drop technique. Short cracks were observed to grow faster than long cracks. The threshold stress intensity range, ΔK_th, as a function of the load ratio was fitted to a simple crack closure model. Fatigue crack growth data were compared with data from other laboratories. Single plain fatigue tests at R=?1 and R= 0 were also carried out. Fracture toughness was measured at temperatures ranging from ?40 °C to room temperature.     

A low-cycle fatigue life prediction model of ultrafine-grained metals

A (high strain) low‐cycle fatigue (LCF) life prediction model of ultrafine‐grained (UFG) metals has been proposed. The microstructure of a UFG metal is treated as a two‐phase ‘composite’ consisting of the ‘soft’ matrix (all the grain interiors) and the ‘hard’ reinforcement (all the grain boundaries). The dislocation strengthening of the grain interiors is considered as the major strengthening mechanism in the case of UFG metals. The proposed model is based upon the assumption that there is a fatigue‐damaged zone ahead of the crack tip within which the actual degradation of the UFG metal takes place. In high‐strain LCF conditions, the fatigue‐damaged zone is described as the region in which the local cyclic stress level approaches the ultimate tensile strength of the UFG metal, with the plastic strain localization caused by a dislocation sliding‐off process within it. The fatigue crack growth rate is directly correlated to the range of the crack‐tip opening displacement. The empirical Coffin–Manson and Basquin relationships are derived theoretically and compared with experimental fatigue data obtained on UFG copper (99.99%) at room temperature under both strain and stress control. Good agreement is found between the model and the experimental data. It is remarkable that, although the model is essentially formulated for high strains (LCF), it is also found to be applicable at low strains in the high‐cycle fatigue (HCF) regime.     

A two-scale system to identify environmental risk of chemical industry clusters

Recent reform policies in China have spurred rapid industrial development. This has led to a large increase in chemical accidents, which may have catastrophic impacts on the local population and environment. As industrial facilities become more complex, it becomes more difficult to control and mitigate the risks associated with chemical accidents. In this study, we propose a two-scale system for assessing the environmental risk level of chemical industry clusters. A series of risk early warning indices for both the plant-specific level and regional clusters level are used in this system. Firstly, at the enterprise scale, a risk early warning index is constructed using inputs such as the presence of hazardous materials, the operation of critical plant equipment and the efficiency of extant management techniques. Secondly, an index for quantifying risks on regional scales depends on environmental, economic, and social conditions as well as the specific enterprises' components. As an illustration, the system is applied to a case study involving a five-plant chemical industry cluster in Jiangsu province, China. A geographical information system-based methodology is used to obtain a composite index score for each mesh of the five plants. The results prove that the proposed two-scale early warning system can efficiently identify environmental risk and help guide emergency responses at both the enterprise and cluster level.     

Effective Safety Management: a Case Study in the Chemical Industry

A major non‐trivial problem within the area of industrial safety management today is to analyse, next to the safety impact of the technical equipment, the safety impact of a ‘business process’ as currently required by regulation and safety standards. This paper describes a case study of a pesticide company struggling with the question of how to improve the safety of their operational process further and at the same time also improve the reliability of their operational process. According to the literature ‘control of the business process’ is the keyword to improve the safety and reliability ‘performance’ of a company. A formal control model is proposed together with a classification system (using maturity levels) to analyse and qualify business processes with respect to their impact on process safety. This method has been applied in a case study where it resulted in a model of a business process. Using the model it was possible to classify the business process control system used and to identify related improvement opportunities. The proposed method showed that, in contrast to the company's perception, it was not the production department that was responsible for most of the problems but the peripheral processes relating to the production department. The interaction between departments caused not only potential safety problems, but also caused system reliability problems. For the company it was demonstrated that the interdependency of the (different activities in the‐) operational process is an essential element preventing further improvement if not addressed properly. Copyright © 2004 John Wiley & Sons, Ltd.     

Robust kernel distance multivariate control chart using support vector principles

It is important to monitor manufacturing processes in order to improve product quality and reduce production cost. Statistical Process Control (SPC) is the most commonly used method for process monitoring, in particular making distinctions between variations attributed to normal process variability to those caused by ‘special causes’. Most SPC and multivariate SPC (MSPC) methods are parametric in that they make assumptions about the distributional properties and autocorrelation structure of in-control process parameters, and, if satisfied, are effective in managing false alarms/-positives and false-negatives. However, when processes do not satisfy these assumptions, the effectiveness of SPC methods is compromised. Several non-parametric control charts based on sequential ranks of data depth measures have been proposed in the literature, but their development and implementation have been rather slow in industrial process control. Several non-parametric control charts based on machine learning principles have also been proposed in the literature to overcome some of these limitations. However, unlike conventional SPC methods, these non-parametric methods require event data from each out-of-control process state for effective model building. The paper presents a new non-parametric multivariate control chart based on kernel distance that overcomes these limitations by employing the notion of one-class classification based on support vector principles. The chart is non-parametric in that it makes no assumptions regarding the data probability density and only requires ‘normal’ or in-control data for effective representation of an in-control process. It does, however, make an explicit provision to incorporate any available data from out-of-control process states. Experimental evaluation on a variety of benchmarking datasets suggests that the proposed chart is effective for process monitoring.     

Using scanning electron,confocal and optical microscopes to measure microscopic holes in trays

Package integrity is of paramount importance to the medical device industry. As healthcare costs soar and integrity testers become more and more sensitive, concern with the question ‘what hole size allows microbial penetration into device packages?’ is re‐ignited. However, producing a consistent and measurable defect in the microcosm presents challenges. Varying techniques are currently employed to produce these defects. Use of an excimer laser is one of the most precise and accurate techniques, and holes ‘certified’ to be a given size can be purchased at a significant cost. To verify the accuracy and precision of holes drilled with an excimer laser, researchers measured laser‐drilled ‘exit’ and ‘entry’ holes in glycol‐modified polyetheylene terephthalate (PETG) trays using scanning electron microscopy (SEM) and confocal microscopy. This data and the certification data provided by the laser driller were analysed using a mixed‐model analysis of variance (ANOVA). Both the effect of measuring technique and hole side (entry vs. exit) were found to be significant. These significant differences have the potential to impact the question that the industry faces with regard to penetration threshold. This suggests that a shift in thinking is needed. Perhaps it would be better if the industry stops thinking about hole size and begins to think in terms of what researchers have referred to as the ‘effective hole’, which is defined as the volume of gas that will flow through a hole of defined size per unit time. Copyright © 2005 John Wiley & Sons, Ltd.     

Diffusional control of the near‐surface microstructure in functional gradient hardmetals

The efforts of the last several years of a research cooperation on diffusional near‐surface microstructure modification of hardmetals are summarised. This modification was performed with a reactive gas supplied within the sintering cycle so that functional gradient hardmetals, FGHMs, were obtained, which show a graded distribution of phases. They were optimised for increased wear resistance in metal cutting operations. The thermochemical and diffusional basics of the preparation of two principally different FGHMs, one with an increased surface hardness and a decreased toughness (with ‘regular gradient’) and one with a decreased surface hardness but an increased toughness (‘inverse gradient’) are described in detail. Some of the developed grades were successfully tested and scaled up into industrial production. The FGHMs were found to outperform conventional hardmetals in certain machining tests (continuous turning as well as milling).     

Distribution‐free Lepage Type Circular‐grid Charts for Joint Monitoring of Location and Scale Parameters of a Process

In the last 5 years, research works on distribution‐free (nonparametric) process monitoring have registered a phenomenal growth. A Google Scholar database search on early September 2015 reveals 246 articles on distribution‐free control charts during 2000–2009 and 466 articles in the following years. These figures are about 1400 and 2860 respectively if the word ‘nonparametric’ is used in place of ‘distribution‐free’. Distribution‐free charts do not require any prior knowledge about the process parameters. Consequently, they are very effective in monitoring various non‐normal and complex processes. Traditional process monitoring schemes use two separate charts, one for monitoring process location and the other for process scale. Recently, various schemes have been introduced to monitor the process location and process scale simultaneously using a single chart. Performance advantages of such charts have been clearly established. In this paper, we introduce a new graphical device, namely, circular‐grid charts, for simultaneous monitoring of process location and process scale based on Lepage‐type statistics. We also discuss general form of Lepage statistics and show that a new modified Lepage statistic is often better than the traditional of Lepage statistic. We offer a new and attractive post‐signal follow‐up analysis. A detailed numerical study based on Monte‐Carlo simulations is performed, and some illustrations are provided. A clear guideline for practitioners is offered to facilitate the best selection of charts among various alternatives for simultaneous monitoring of location‐scale. The practical application of the charts is illustrated. Copyright © 2016 John Wiley & Sons, Ltd.     

Measurement and analysis of ‘small’ packages in next‐day air shipments

Packaged goods are shipped globally using various means of transportation. Over the past two decades, there has been a continuous increase in studies that measure and analyse dynamic events that occur to packages during transportation and handling. These data offer useful information to design and test packages, and provide protection from potential hazards like drops and impacts. However, none of the past studies are directed towards single packages regarded as ‘smalls’. ‘Smalls’ or small‐package product systems are defined as those with volume of less than 0.013 m³, a longest dimension of 0.356 m and a weight of 4.54 kg or less. Packages that qualify for these specifications are often mixed together in a large carrying bag and handled with other single parcel shipments. This study measured and analysed the effect of moving this category of single packages through expedited shipments in the USA. The results showed that these packages experienced as many as 27 events comprising of drops or tosses in a one‐way shipment, and a maximum of 5.01 m of near‐zero G travel distance representing long ‘tosses’. Copyright © 2009 John Wiley & Sons, Ltd.     

The prediction of crack growth rates from total endurances in high strain fatigue—thirty years on

McClintock 1 , 2 was one of the first to model continuous‐cycling fatigue crack growth by assuming a succession of miniature low‐cycle‐fatigue (LCF) specimens at the crack tip. Elements ahead of the crack amass damage until the arrival of the tip itself. Such models had been summarized by Majumdar and Morrow, 3 but the author was unaware of these papers at the time. The ideas were pursued further by Chakrabortty 4 whose paper, again unknown to the author, was published in the same issue (1979, Vol. 2) of FEMS. In the original paper 5 crack propagation is represented by successive regeneration at the crack tip, the process becoming progressively easier as the crack grows owing to an increase in strain concentration. These ‘initiation’ cycles were related to the ‘Coffin’ expression for crack initiation, thereby introducing two empirical constants k and α. The paper is of the class ‘ρ/N’ where ρ is the assumed size of a crack‐tip process zone and N is the cycles required to traverse that zone. Expressions had been previously derived linking LCF with linear‐elastic fracture‐mechanics (LEFM) crack growth, using the parameter ΔJ. 6 (It was later shown that this was identical to using an equivalent stress intensity parameter. 7 ) It has been shown that the approach does not apply for crack depths < 180 μm. 6 At elevated temperature the ΔJ approach was successful for describing crack growth in the range 0.2–1.2 mm for the cobalt‐based alloy MAR‐M509 at 600 °C. 8 Other studies have in fact shown 9 that crack growth rates are approximately constant below a depth of 200 μm. Even to this day short crack growth relations in LCF and their practical use are not as familiar as those in LEFM. It may justifiably be argued that for every paper published on LCF short crack growth, several hundred have appeared dealing with LEFM crack growth in terms of the ‘Paris’ law. One of the original referees' comments was that the paper 5 should have been presented in terms of LEFM. The author nevertheless defended his approach because for small cracks it was thought useful to retain the crack depth explicitly. It will be shown that LCF crack growth data have a definite part to play in the assessment of components and structures.     

An integrated architecture for implementing extended producer responsibility in the context of Industry 4.0

Extended producer responsibility (EPR) is a regulatory measure to enforce the life cycle management of electrical and electronic equipment, however, the implementation of EPR programmes is not as effective as expected. In the face of the fourth industrial revolution that commonly labelled as ‘Industry 4.0,’ this paper proposes an integrated architecture to achieve effective and efficient EPR from the manufacturer perspective, and attention is specifically paid on promoting information sharing. On the basis of the selected case study, a smart refrigerator plant of Haier, the architecture integrates information systems and facilitates life cycle management. Particularly, eco-design and end-of-life disposal, the two lasting problems in the current practises of implementing EPR, can be enforced based on product modularisation and high level of information availability that provided by the architecture. The outcomes of this study provide a valuable reference for other sectors that involve EPR or product life cycle management.     

Elektronenstrahlschweißen an Atmosphäre – von der Entwicklung bis zum industriellen Einsatz

Non vacuum electron beam welding – from development to industrial application Attributable to the increasing degree of standardisation in many fields of industrial manufacturing, the saving of resources and thus the demand for light weight constructions and also the rapid development on the material sector have made joining tasks increasingly complex. This involves the joining method which must meet the metallurgical demands of the base materials to be welded and also the method’s profitability. In this connection, electron beam welding in atmosphere – NV‐EBW ‐ as a joining method is getting more and more important and is, from the side of the industry, becoming increasingly popular. NV‐EBW combines the many, well‐known advantages of electron beam welding in vacuum with the possibility to work under normal ambient pressure. With an equipment efficiency of more than 50 % and very high, achievable welding speeds of up to 60 m/min for aluminium materials, the electron beam in atmosphere is an efficient and profitable tool for welding. Under the direction of Professor U. Dilthey, the ISF has for many years and in close contact with industrial partners carried out research work in the field of the NV‐EBW technology. At that, elementary contribution to the development of rotationally‐symmetrical orifice assemblies and also to the testing and optimization of the method with regard to respective welding tasks has been carried out.     

An Experimental Study of the Mechanical Behaviour of the ‘Conchyliates’ Shell‐Stone: Some Irregularities of the Size Effects

Abstract: A detailed experimental study of the size effect, i.e. of the dependence of the mechanical properties on the size of the (self‐similar) specimens used for the laboratory tests is presented in this paper for the case of a relatively soft natural building stone called ‘conchyliates’ (shell‐stone). ‘Conchyliates’ was used by ancient Greeks for the erection of the Zeus Temple at the Olympia archaeological site. The motive of the study was the need of the scientists working for a partial restoration of the monument for an in‐depth knowledge of the mechanical behaviour of both the original building material of the monument as well as of the material that could be used for the completion of damaged structural elements. During the study various classes of cylindrical ‘conchyliates’ specimens were subjected to uniaxial (unconfined) compression. It was concluded that the dependence of the peak stress of the material on the size of the specimen is not only very strong but it appears to be, also, non‐monotonous. In addition it was indicated that the size of the specimens also influences the elasticity modulus as well as the strain energy density in a more or less similar manner. On the contrary it is concluded that the slope of the strain energy density plotted versus strain is not seriously affected by the size of the specimen, at least for the working‐load portion of the stress‐strain graph.     

Fatigue properties of AA6060‐T6 butt welds made by hybrid metal extrusion & bonding

The present investigation is concerned with high‐cycle axial fatigue testing of a 2‐mm AA6060‐T6 hybrid metal extrusion & bonding (HYB) butt weld produced in the solid state using AA6082 filler metal addition. The results complement the three‐point bend testing and the tensile testing done in two previous studies. In this study, optical microscope and scanning electron microscope examinations have been carried out to reveal the joint macro/microstructure and document possible surface and root defects deemed to affect fatigue life. In the as‐welded condition, the HYB weld suffers from surface irregularities at the weld face and ‘kissing’ bond formation in the root region. Despite of this, the subsequent testing shows that the fatigue properties exceed those reported for comparable AA6082‐T6 gas metal arc butt welds and matching those reported for corresponding high‐strength laser beam and friction stir weldments.     

Modeling and Monitoring Ecological Systems—A Statistical Process Control Approach

Statistical process control monitoring of nonlinear relationships (profiles) has been the subject of much research recently. While attention is primarily given to the statistical aspects of the monitoring techniques, little effort has been devoted to developing a general modeling approach that would introduce ‘uniformity of practice’ in modeling nonlinear profiles (analogously with the three‐sigma limits of Shewhart control charts). In this article, we use response modeling methodology (RMM) to demonstrate implementation of this approach to statistical process control monitoring of ecological relationships. Using 10 ecological models that have appeared in the literature, it is first shown that RMM models can replace (approximate) current ecological models with negligible loss in accuracy. Computer simulation is then used to demonstrate that estimated RMM models and estimated data generating ecological models achieve goodness‐of‐fit that is practically indistinguishable from one another. A regression‐adjusted control scheme, based on control charts for the predicted median and for residuals variation, is developed and demonstrated for three types of ‘out of control’ scenarios. Copyright © 2013 John Wiley & Sons, Ltd.     

Solution strategies for the delamination analysis based on a combination of local‐control arc‐length and line searches

The paper describes a local‐control arc‐length method which can be combined with various forms of line‐search procedure. In particular, a new ‘double‐line‐search’ method is developed, which significantly improves the solution procedure and turns out to be efficient and robust. Although the potential range of applications is wide, the method is here limited to the finite element analysis of delamination in a laminated composite using a cohesive‐zone model combined with interface elements. Three problems have been analysed and comparisons have been made with experimental results. Copyright © 2003 John Wiley & Sons, Ltd.     

Continuous Taguchi—a model-based approach to Taguchi's ‘quality by design’ with arbitrary distributions

Statistical experimental design has been used in ‘off-line’ quality control to determine the optimal settings for a system even when the mathematical model is known. Taguchi demonstrated how signal-to-noise ratios could be used to improve the performance of a system through variance minimization. However, these statistical methods often do not use the full distribution information that may be available. Proposed in this paper is an extension and complement to Taguchi's use of experimental design and signal-to-noise ratios for known system models. The use of a probability transformation method with the mathematical system model will allow designers to perform parameter and tolerance design simultaneously using a method of ‘fast integration’. The result is a new method in the field of ‘quality by design’, which we call continuous Taguchi, that can handle both linear and non-linear systems, with components of any distribution type, with or without correlation of the variables. In addition, an interpretation of Taguchi's classification of factors is given in the context of our full distribution method. © 1998 John Wiley & Sons, Ltd.     

Instructional Module in Fourier Spectral Analysis,Based on Principles of “How People Learn”

This paper describes the design and evaluation of an instructional module for teaching/learning Fourier spectral analysis, with emphasis on biomedical applications. The module is based on the principles of “How People Learn” (HPL) as embodied in the Legacy cycle. This cycle is a particular instantiation of problem‐based learning and includes components explicitly aimed at providing context and motivation, facilitating exploration, developing in‐depth understanding, and incorporating opportunities for self‐assessment. In the spectral analysis module, traditional teaching methods are augmented with small group discussions, peer‐to‐peer learning, a Web‐based tutorial, and an interactive demonstration. Assessment included the development of rubrics for scoring student understanding of key concepts, revealing that students who used the module demonstrated better understanding relative to students who studied the material using traditional methods. Survey results and comments indicate that students generally liked the interactive tutorial and demonstration, as well as the structure provided by the HPL framework.     

Optimal control of vortex shedding using low‐order models. Part I—open‐loop model development

An approach to developing active control strategies for separated flows is presented. The methodology proposed is applied to the incompressible unsteady wake flow behind a circular cylinder at a Reynold's number of 100. Control action is achieved via cylinder rotation. Low‐order models which are amenable to control and which incorporate the full non‐linear dynamics are developed by applying the proper orthogonal decomposition technique to data provided by numerical simulation. This process involves extensions to the usual POD approach and the results are therefore assessed for two ‘open‐loop’ test cases. The predictions are found to be satisfactory for control purposes, assuming the model can be reset periodically. The use of these models for optimal control is discussed in a companion paper, Part II. Copyright © 1999 John Wiley & Sons, Ltd.