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This article deals with the development of design rules for structural adhesive bonded joints. In daily practice engineers are confronted with the problem to verify the reliability of their designs. This can be done with use of an experimental programme, but for the marine, transport, building and civil engineering sectors this will not be an option, because it is too expensive and time consuming. The use of design rules might be an alternative, but current guidelines for structural adhesive bonded joints do not guarantee the reliability. To develop design rules that meet the required level of reliability, new approaches have to be used. Such a systematic approach is presented in this article. It is based on the current structural adhesive bonding technology and on structural reliability methods. Partial factors are used to take the required reliability level into account. Additional conversion factors are introduced to cover the effects of ageing. Methods are discussed how to calibrate these factors. To illustrate the developed approach, examples of calibrating design rules for metal overlap joints with epoxy and polyurethane adhesives are presented.

Load and depth sensing indentation has been used to characterize the elastic modulus and hardness of various polycarbonate films. This analytical technique is shown to be extremely suitable for the determination of gradients in these mechanical properties. Furthermore, it is demonstrated that such a gradient exists over a length of micrometers in chemically aged polycarbonate, but it is virtually absent in physically aged polycarbonate. From these results, it is concluded that, although the first 100 nm cannot be probed, physical aging occurs homogeneously throughout the bulk of the sample. However, chemical aging starts at the surface and moves progressively into the bulk of the material. From the study of these films, it appears that for the interpretation of these measurements, knowledge about the amount of creep occurring during the measurements and about the mechanical properties of the substrate on which these films are applied is needed. Creep can be measured with the same indenter through the application of a constant load for a period of time. Load and depth sensing indentation appears to be a powerful method for studying the physical and chemical aging of polymers. It is especially valuable for coatings and films for which conventional tensile testing is problematic. © 2004 Wiley Periodicals, Inc.

The various properties of an SB and a DB gun propellant were investigated before and after artificial ageing. It was found that the decrease of nitrocellulose (NC) molecular weight, due to ageing of gun propellants, leads to a decrease of the mechanical integrity of the propellant grains. The effect of grain fracture on the peak pressure was found to be strongly related to the loading intensity. It was suggested that a relation exists between grain fracture and NC molecular weight, which describes that propellants become more brittle when the NC chain length decreases.

Thermal analysis is an interesting technique to determine kinetic parameters of separate components, and also of a complete system to receive adequate information on the ageing process of pyrotechnic compositions. The investigated tracer is a tracking tracer of a Swiss missile. It is attached to a missile and produces during burning a red flame. The missile system is already in use for 15 years. Periodic inspections of the system take place every three years. These inspections, however only give information on the actual state of the tracer and not on the future state. The aim of this investigation is to predict the ageing behaviour of the tracer system to give additional information about the future use of the missile system. After two ageing profiles the tracer systems were tested on the test range at Armasuisse in Thun. The results of the testing show that an ageing period of 4 weeks at 60°C gives no changes in performance (light output and burning time). On the other side also a quite heavy ageing period of 4 weeks at 150°C was applied on tracer systems, which gives a dramatically change in burning time. The light output was even higher after this ageing profile, although the intensity changes a lot. © 2005 Akadémiai Kiadó, Budapest.

A lifetime prediction study is carried out on four triple base propellant compositions by artificial ageing. The ageing effects are studied with High Performance Liquid Chromatography (HPLC) and Heat Flow Calorimetry (HFC) in order to find the most effective stabilizer and to evaluate the advantages and disadvantages of both methods. It is observed that the Ethyl Centralite (EC) and Akardite II stabilized compositions are less affected by the artificial ageing than the Diphenylamine (DPA) and N-Methyl-p-Nitroaniline (MNA) stabilized compositions. The DPA- and the MNA-stabilized propellants are not considered to be safe for the next 10 years based on the HPLC results. Based on the HFC results the DPA-stabilized propellant will also be expected to be safe for a period of ten years. HFC is considered as the best way to determine the propellants lifetime, because the method measures the most important effect of ageing, i.e. the heat generation rate of all chemical processes which occur. The heat generation rate gives an indication of the decrease in calorific value as well as the self-heating potential. HPLC measures the stabilizer and stabilizer derivative content. This only gives an indication of the time that the stabilizer will be present in the composition, but does not provide data of the consumed energy or information on the self-heating potential during the evaluation period. Stabilizing effects of stabilizer derivatives may be neglected in HPLC analysis resulting in an underestimation of the safe lifetime. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The present investigation assessed the putative benefits of reducing instructions for older adults' learning of an assembly task. Young and older adults had to build a product by assembling six components. Two groups practiced following instruction methods that differed in the degree of explicit information they conveyed about the correct assembly order. After practice, retention, consolidation of performance (tested immediately after practice and on a separate day, respectively) and stability of performance (tested by introducing a concurrent second task) were assessed. Younger adults showed similar performance levels for both instruction methods. Older adults, however, showed similar retention but clearly weaker consolidation and stability of performance following less encompassing instructions. Contrary to expectations, enhancing the involvement of explicit processes allowed older adults to gain a more permanent and stable performance improvements. The findings are discussed relative to the characteristics of the assembly task. Practitioner Summary: We addressed how performance and learning of older adults in an assembly task can be optimised through different types of instruction. The findings suggest that increasing awareness of task characteristics enhance not only long-term performance, but also resilience against distraction. Future work must evaluate if these findings generalise to more complex tasks. © 2014 Taylor & Francis.

Nutrition of articular cartilage relies mainly on diffusion and convection of solutes through the interstitial fluid due to the lack of blood vessels. The diffusion is controlled by two factors: steric hindrance and electrostatic interactions between the solutes and the matrix components. Aging comes with changes in the cartilage structure and composition, which can influence the diffusion. In this study, we treated fibrocartilage of mandibular condyle with ribose to induce an aging-like effect by accumulating collagen crosslinks. The effect of steric hindrance or electrostatic forces on the diffusion was analyzed using either charged (Hexabrix) or uncharged (Visipaque) contrast agents. Osteochondral plugs from young equine mandibular condyles were treated with 500 mM ribose for 7 days. The effect of crosslinking on mechanical properties was then evaluated via dynamic indentation. Thereafter, the samples were exposed to contrast agents and imaged using contrast-enhanced computed tomography (CECT) at 18 different time points up to 48 h to measure their diffusion. Normalized concentration of contrast agents in the cartilage and contrast agent diffusion flux, as well as the content of crosslink level (pentosidine), water, collagen, and glycosaminoglycan (GAG) were determined. Ribose treatment significantly increased the pentosidine level (from 0.01 to 7.6 mmol/mol collagen), which resulted in an increase in tissue stiffness (~1.5 fold). Interestingly, the normalized concentration and diffusion flux did not change after the induction of an increased level of pentosidine either for Hexabrix or Visipaque. The results of this study strongly suggest that sugar-induced collagen crosslinking in TMJ condylar cartilage does not affect the diffusion properties.Nutrition of articular cartilage relies mainly on diffusion and convection of solutes through the interstitial fluid due to the lack of blood vessels. The diffusion is controlled by two factors: steric hindrance and electrostatic interactions between the solutes and the matrix components. Aging comes with changes in the cartilage structure and composition, which can influence the diffusion. In this study, we treated fibrocartilage of mandibular condyle with ribose to induce an aging-like effect by accumulating collagen crosslinks. The effect of steric hindrance or electrostatic forces on the diffusion was analyzed using either charged (Hexabrix) or uncharged (Visipaque) contrast agents. Osteochondral plugs from young equine mandibular condyles were treated with 500 mM ribose for 7 days. The effect of crosslinking on mechanical properties was then evaluated via dynamic indentation. Thereafter, the samples were exposed to contrast agents and imaged using contrast-enhanced computed tomography (CECT) at 18 different time points up to 48 h to measure their diffusion. Normalized concentration of contrast agents in the cartilage and contrast agent diffusion flux, as well as the content of crosslink level (pentosidine), water, collagen, and glycosaminoglycan (GAG) were determined. Ribose treatment significantly increased the pentosidine level (from 0.01 to 7.6 mmol/mol collagen), which resulted in an increase in tissue stiffness (~1.5 fold). Interestingly, the normalized concentration and diffusion flux did not change after the induction of an increased level of pentosidine either for Hexabrix or Visipaque. The results of this study strongly suggest that sugar-induced collagen crosslinking in TMJ condylar cartilage does not affect the diffusion properties.