Obsolescence – A review of the literature

Technology progress and fierce competitiveness between manufacturers creates intense pressues to innovatively develop and sell new products. These products could be household or industrial items, such as telephones, computers, machines, robots, unmanned aerial vehicle (UAV), motors, industrial processes, electronic devices, tools, and spare parts in general. The technological progress implies the use of the word “obsolescence.” The new products have higher performance metrics compared to the older units, such as reliability, resilience, memory capacity, improved material, precision, artificial intelligence, lower energy consumption, ergonomics, and safety. Therefore, obsolescence became a paradox in our daily life and industry. This paper presents a literature review of the main published works on obsolescence (1976–2020). Its typologies, consequences and replacement strategies are illustrated.     

Mechanical alloying – the development of strong alloys

Abstract

Mechanical alloying is a solid-state process for making alloys by high-energy milling, under conditions such that constituent powders are repeatedly fractured and welded together and ever more intimately mixed. After subsequent consolidation at elevated temperature, the alloys can be shaped by rolling, forging, and machining. The process is used to incorporate a fine dispersion of ceramic particles. Mechanically alloyed nickel-base superalloys, combining a dispersion of yttria with conventional precipitation strengthening, have achieved higher strength at 900–1100°C than directionally solidified and single-crystal alloys, and are being used for gas-turbine vanes and blades. Mechanically alloyed ferritic stainless steel, with outstanding strength and corrosion resistance at temperatures as high as 1300°C, has been produced as sheet, tube, plate, rings, and forgings. Mechanically alloyed aluminium alloys also offer higher strength, e.g. in as-forged thick sections of Al–Mg–Li alloy.

MST/567     

Hours-per-vehicle controlling – the renaissance of staff productivity

In the global automobile industry, the Hours-Per-Vehicle factor (HPV) is turning more and more into a key indicator for personnel productivity analysis of a production plant. HPV rankings are compiled and personnel goals are derived from comparison of HPV benchmarks. Besides program units and the budget, HPV is advancing to be one of the dominant controlling indicators. Against this background, there is an increasing demand for effective HPV controlling. The major task of such controlling is to ensure the required transparency for the influencing variables as well as to recommend measures to improve personnel productivity. In this context, HPV controlling is not just to be incorporated in the existing target and controlling landscape, but also into existing personnel productivity improvement processes. This article takes up these requirements and demonstrates approaches to a solution. Moreover, it describes the potential and also the limits of HPV applications.     

Pentaerythritol crystallization – Influence of the process conditions on the granulometric properties of crystals

The quality of crystals depends on many factors that determine their granulometric properties. In order to obtain crystals of desired size distribution, proper selection of the operating conditions is of a great importance. Commonly, the unseeded cooling crystallization is controlled by selecting the appropriate cooling profile. The crystallization process can also be controlled by adding a certain number of seed crystals of a uniform size in the crystallizer at the saturation temperature. This paper investigates the influence of the process conditions (mixing intensity, cooling profile, batch time, saturation temperature and seeding) on the granulometric properties of pentaerythritol obtained by batch cooling crystallization. All investigated process conditions influence the crystal size distribution (seeded and unseeded experiments). On the other hand, the shape of crystals was the same for all experimental conditions. Optimal cooling profile, lower retention time, higher mixing rate, and smaller initial seed surface area improves the final crystal size distribution.     

Adhesion of thermal barrier coatings – the development of metastable alumina

Abstract

The adhesion of thermal barrier coatings (TBCs) is dependent upon the characteristics of the thermally grown oxide (TGO) that forms between the TBC and the corrosion resistant bond coat. Work has been carried out to investigate the properties of the TGO as a function of ageing treatments using piezospectroscopy. Residual stress maps were generated for an electron beam physical vapour deposited (EB-PVD) TBC which showed a large variation in residual stress over the surface of a coated sample. The two peaks generally associated with a alumina (R1 and R2) frequently appear as doublets with a high and low stress component. In addition, the presence of a metastable θ alumina was detected in aged samples. It is believed that these observations can be related to incipient spallation of the TBC. The development of residual stress and the metastable oxide have been studied and correlated with the spallation behaviour of the TBC.     

Predicting the service-life of concrete structures – Limitations of simplified models

North American civil infrastructure systems are deteriorating. Roads, bridges, overpasses, marine and airport facilities are all impacted. The primary causes of premature concrete deterioration are harsh climatic conditions and chemical attacks, particularly exposure to winter de-icing salts and seawater. Given the growing concern for concrete degradation, numerous computer-assisted tools have been developed to assist engineers in the prediction of the service-life of structures. Many of these models are based on simplified equations that significantly restrict the scope of their application. The limitations of these approaches for the design of new construction and rehabilitation of existing structures are discussed. The theoretical assumptions at the basis of these models are first reviewed. Special attention is paid to the consequences of these simplifying assumptions on the reliability of the models. The difficulties of using these simplified models for the treatment of actual structures exposed to natural conditions are then discussed.     

Great differences in the ways of implementing the new EIA Directive – the offerings of the EIALAW 2018 conference

On the 23 March 2018, the most recent developments of the environmental impact assessment (EIA) law were examined by experts in Helsinki. The main theme of the conference was the comparison of the implementation experiences of various countries concerning the reformed EU EIA Directive. The European EIA debate was reflected against experiences in Canada. This paper examines the key points of the conference presentations and the lessons of the event.     

Mechanical and leakage behaviour of the dentin – adhesive interface

Dentine bonding systems (DBS) have been developed in order to bond restorative materials (i.e. composite) to the inner walls of the tissues when function and integrity as to be restored. Adhesion to dentine results from the penetration of DBS into the demineralised substrate constituted by a swollen collagen network. The short-term stability of a restored tooth is mainly affected by the presence of defects which act as stress raiser, while the long-term stability of a restored tooth is mainly affected by the seal of the restorative material on the dental structures. In order to determine the properties of the material interface, bonding to dentine is analysed using micro-tensile static and dynamic tests, assisted by the finite element modelling (FEM) and by the X-ray computed microtomography (micro-CT). The effect of voids and porosity in the composite layer of the DBS on the stress distribution has been investigated. Tensile adhesive strength for a particular DBS was measured on cylindrical specimens. The dual energy absorption technique, with the synchrotron beam light, has been developed to investigate, in a non-destructive manner, the leakage at the dentine-DBS interface of a silver nitrate staining solution as a function of mechanical cycling. The results indicate that leakage occurs radially through the dentine-adhesive interface and is influenced by the porosity in the adhesive and composite layers.     

Hardness of model dental composites – the effect of filler volume fraction and silanation

The relationship between structure and mechanical properties for dental composites has often proved difficult to determine due to the use of commercially available materials having a number of differences in composition i.e. different type of resin, different type of filler, etc. This makes a scientific study of any one variable such as filler content difficult if not impossible. In the current study it was the aim to test the hypothesis that hardness measurements of dental composites could be used to monitor the status of the resin–filler interface and to determine the efficacy of any particle silanation process. Ten model composites formulated from a single batch of resin and containing a common type of glass filler were formulated to contain varying amounts of filler. Some materials contained silanated filler, others contained unsilanated filler. Specimens were prepared and stored in water and hardness (Vickers') was determined at 24 h using loads of 50, 100, 200 and 300 g. Composites containing silanated fillers were significantly harder than materials containing unsilanated fillers. For unsilanated products hardness was independent of applied load and in this respect they behaved like homogeneous materials. For composites containing silanated fillers there was a marked increase in measured hardness as applied load was increased. This suggests that the hardness–load profile could be used to monitor the status of the resin–filler interface. ©1999 Kluwer Academic Publishers     

Effect of the Crystallographic Orientation of GaAs Substrates on the Composition of Ga x In1 – x P Layers

The effect of the crystallographic orientation of GaAs substrates on the composition of Ga _x In_{1 – x} P solid solutions grown by liquid-phase heteroepitaxy is studied. It is shown that GaAs-lattice-matched Ga _x In_{1 – x} P solid solutions can be grown, under identical conditions, on (100), (111), and (111) GaAs substrates using different melt compositions. The results are interpreted in terms of the contribution from the energy of the crystal–melt interface to the total energy of mixing of the solid solution.     

How big data and analytics reshape the wearable device market – the context of e-health

The wearable device can be a key link between health care and big data and analytics (BDA). The benefits of BDA in health care have been widely acknowledged, but the uncertainty of the implementation of BDA has led some firms to hesitate in adopting this technology. In this research, we are keen to answer the key questions of whether the wearable device firms would adopt the BDA strategy, and how much effort they would put into it. We propose a competition model between the wearable device firms with and without BDA strategies, and consider the consumer’s preference towards BDA and network effects. Our model demonstrates that the investment on BDA directly affects the firm’s equilibrium price, market share and profit and at the same time, this strategy also affects the rival’s performances. When the firm with BDA strategy adopts different competition strategy: conservative or expansive, the outcomes of market are different. We also find that different market structures, fully covered and partially covered, have different impacts on the firms’ competition when the consumers have heterogeneous preference on BDA strategy.     

Web Thermo Tables – an On-Line Version of the TRC Thermodynamic Tables

It has long been understood that availability of thermophysical and thermochemical property data is vital to scientific research and industrial design. For over 65 years, the Thermodynamics Research Center (TRC) has been publishing tables of critically evaluated data covering physical and thermodynamic properties of pure compounds, TRC Tables-Hydrocarbons and TRC Tables-Non-Hydrocarbons. Over their long history, the TRC Tables have always been valued as a reputable source of evaluated thermophysical and thermodynamic data. To facilitate more flexible, convenient, and up-to-date access to the data, here, we present the release of the on-line version of the TRC tables, Web Thermo Tables (WTT). Presently, WTT contains data for 7838 compounds and over 950,000 evaluated data points. The tabulated information includes critical properties, vapor pressures and boiling temperatures, phase transition properties, volumetric properties, heat capacities and derived properties, transport properties, reaction state-change properties, as well as index of refraction, surface tension, and speed of sound. Various search options and data plotting capabilities are provided via the Web interface. WTT are distributed through the NIST Standard Reference Data Program [1].     

Human health frames in EIA – the case of Swedish road planning

How human health is framed provides boundaries for choices in practice and bias for certain actions in health assessments in Environmental Impact Assessment (EIA). This study examines health frames in legislation and policies of importance for EIA in Swedish road planning and their implications for practice. The emphasis is on different approaches, such as promotion of health and prevention of ill-health. Indicators of the choices in practice for which the health frames exert bias are further analysed through a review of Environmental Impact Statements (EIS) for road planning and comparison with a similar study conducted about 10 years ago. The indicators studied are: health determinants included, health impacts assessed, and aspects of the affected population concerned in the EISs. There are fundamentally different health frames in Swedish legislation and policies, but this range is not yet reflected in EISs, which mainly focus on environmental health rather than on broader health determinants and health equity. The results indicate that this situation becomes a dilemma for EIA practitioners and a challenge for the field.     

Precipitation hardening of Cu – Ti – Zr alloys

Abstract

The influence of age hardening temperature and time on the hardness, tensile properties, electrical conductivity, and microstructure of Cu – 4Ti – 0.1Zr and Cu – 3Ti – 0.1Zr alloys has been investigated. The resulting microstructure of these alloys suggests that zirconium addition prohibited the formation of compositional modulations in the solution treated condition. These alloys exhibited maximum hardness and strength on peak aging at 450°C for 24 h by the formation of a coherent and metastable Cu₄Ti phase (β') in modulated structure while overaging occurred by the formation of equilibrium phase β-Cu₃Ti. The electrical conductivity of both the alloys increased moderately on aging. Unlike in an earlier study of binary Cu – Ti and some ternary Cu – Ti – X alloys, overaging did not cause any discontinuous precipitation in the Cu – Ti – Zr alloys investigated. Modulated structure formed on peak aging persisted on prolonged aging at 450°C for 80 h or at 500°C for 8 h.     

Fiber Reinforced Composites – Advanced Materials for the Renewal of Civil Infrastructure

Fiber reinforced polymer matrix composite materials hitherto used predominantly in aerospace and marine applications are increasingly being considered for use in the renewal of civil infrastructure ranging from the seismic retrofit of bridge columns and the strengthening of parking garage floor slabs to their use in replacement bridge decks and in new bridge structures. Their corrosion resistance, potentially high overall durability, light weight, tailorability and high specific performance attributes enable their use in areas in which the use of conventional materials might be constrained due to durability, weight or lack of design flexibility. This paper provides an overview of the use of composites in the renewal of civil structures with particular emphasis on bridges and pipelines. Examples of large scale testing for the validation of structural effectiveness are given and future design and research advances are presented.     

Refrigerant distribution in the vertical header of the microchannel heat exchanger – Measurement and visualization of R410A flow

This paper presents the R410A adiabatic upward flow in three vertical headers of microchannel heat exchangers. All microchannel tubes are inserted into the half depth. The objectives are to explore what affects R410A distribution and attempt to predict the distribution. R410A is circulated into the header through the (5 or 10) tubes in the bottom pass and exits through the (5 or 10) tubes in the top pass. It represents the flow in the outdoor heat exchanger (usually used as the condenser) when it is used as the evaporator in the heat pump mode of reversible systems. The quality was typically varied from 0.2 to 0.8 and the mass flow rate from 1.5 to 4.5 kg h^?1 per tube. The best distribution was observed at high mass flux and low quality. The experiment and visualization reveals the flow pattern effects in terms of homogeneity and momentum. The churn flow had better distribution since the two-phase mixture was more homogenous and the distribution was better at high mass flux in the header because the higher momentum liquid was able to reach the top exit tube.     

Influence of the Functional Layer on the Operating Characteristics of Zr – 1% Nb Alloy at a Temperature of 380°С

Materials Science - We study the influence of thermal treatment of fuel cladding tubes in various gas media on the short-term and long-term strengths at an operating temperature (380°C). The...     

Fracture toughness of the + 45° / – 45° interface of a laminate composite

Experiments are carried out to determine the delamination toughness for a crack along the interface between two transversely isotropic materials. The material chosen for study consists of carbon fibers embedded within an epoxy matrix. A crack is introduced between two layers of this material, with fibers in the upper layer along the + 45°-direction and those in the lower layer along the − 45°-direction both with respect to the crack plane. The Brazilian disk specimen is employed in the testing. To calibrate the specimens, stress intensity factors are obtained which result from the applied load, as well as residual curing stresses. It may be noted that all three modes are coupled, leading to a three-dimensional problem. The finite element method and a mechanical M-integral are employed to determine the stress intensity factors arising from the applied load. For the residual stresses, a three-dimensional conservative thermal M-integral is presented for stress intensity factor determination. The stress intensity factors found for the applied load and residual stresses are superposed to obtain a local energy release rate, together with two phase angles. From the load at fracture, the critical interface energy release rate or interface toughness as a function of phase angles ψ and ϕ is determined. Results are compared to a fracture criterion.     

On the resistance to penetration of stiffened plates,Part I – Experiments

The paper deals with hull damage in ships which are subjected to grounding actions. A ship is assumed to settle vertically on a rock. It is further assumed that contact actions are local and restricted to one plate section. The scenario is analyzed by conducting a series of panel indentation experiments. Various configurations of stiffened panels are loaded laterally by a cone shaped indenter until fracture occurs. The specimen dimensions represent a 1:3 scale of the dimensions found in medium sized tankers. Naturally, because damaged hull and cargo tanks may have severe environmental consequences, e.g. as exemplified by high profiled grounding accidents such as the Exxon Valdez grounding which lead to the discharge of nearly 240,000 barrels of oil, focus is on the plastic deformation and fracture resistance of the panel.     

Engineering ceramics – the process problem

Abstract

The main problem to be solved before advanced engineering ceramics can become industrial reality is that components having reliable and consistent properties cannot be made, and rejection rates can be as high as 95%, in stark contrast to the situation with metals and polymers. This results from the small size of defect sufficient to cause failure in a ceramic and the variability in the population density of such defects. It is unlikely that sufficiently sensitive non-destructive testing and diagnostic techniques will become available, and so success will depend on the development of intrinsically reliable process technology. The nature and origin of defects in ceramics are discussed and related to raw material characteristics and process technology. The changes that are needed in raw materials and processes are outlined, and the various approaches to intrinsically reliable techniques (such as the colloidal processing of submicrometre powders, sol–gel methods, etc.) are critically assessed in the light of the need for industrially realistic processes. An attempt is made to assess likely future developments such as ceramic fibre reinforced ceramics.

MST/409