CUMBRE DE Gran Canaria [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

A simplified design approach to prevent shrinkage cracking in patch repairs

This paper outlines two procedures for determining the interfacial shrinkage stresses in a repair patch. The first is an analytical approach based on the analogy of a bimetallic strip undergoing contraction (shrinkage). The second is a semi-empirical procedure based on strain monitoring of in situ repairs to in-service bridges. The procedures determine conversion factors to relate the specified properties of the repair materials to their in situ properties in a field repair patch. For example, the shrinkage of a repair patch is influenced by the volume–surface effect, site temperature and relative humidity which are not considered in repair material specification. Creep is initiated in situ by differential shrinkage stresses in the repair material and is determined by adopting an effective elastic modulus approach. Both procedures require the basic material properties (elastic modulus, shrinkage, creep) and geometrical details (width, depth) of the repair patch. The analytical approach incorporates the repair material creep coefficient to predict the interfacial tensile stresses. Alternatively, it uses a less rigorous, elastic approach that omits creep. The creep approach provides higher accuracy whereas the elastic approach overestimates stresses since relaxation by creep is neglected. The elastic approach is recommended for design due to its simplicity and the in-built factor of safety provided by the overestimation of tensile stress. The semi-empirical approach uses an expression derived from long-term field data to determine the strain (and consequently stresses) at the interface of the repair patch and the substrate concrete. The procedures predict the maximum interfacial tensile stress during the service life of a repair patch. They can be used to design crack-free repair patches and optimise repair material selection through a better understanding of the interaction between the repair patch and substrate concrete.</p

A design framework for the mass customisation of custom-fit bicycle helmet models

Mass customisation (MC) can provide significant benefits to the customers. For example, custom-fit design approaches can improve the users’ perceived comfort of products where the fit is an important feature. MC can also bring major value to the producers, where for instance, premium prices can be implemented to the products. Research show that MC can bring competitive advantages especially when the system is new. It is therefore surprising that MC of helmets has not been studied more extensively, especially given the advances in 3D scanning, computational analyses, parametric design, and additive manufacturing techniques. The purpose of this study was to present a novel MC framework for the design of custom-fit bicycle helmet models. In the proposed design framework, we first categorized a subset of the Australian population into four groups of individuals based on their similar head shapes. New customers were then classified inside one of these groups. The customisation took place inside these groups to ensure that only small variations of the helmet liner were implemented. During the design process, the inside surfaces of a generic helmet model was modified to match the customer's head shape. We demonstrated that all the customized models created complied with the relevant drop impact test standard if their liner thickness was between the worst and best case helmets of each group. Fit accuracy was verified using an objective evaluation method. Future work should include detailed description of the manufacturing methods engaged in our MC framework

VEGA, JOSÉ [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Effect of cooling methods on dimensional accuracy and surface finish of a turned titanium part

In metal cutting, the choice of cooling method influences the deformation mechanism, which is related to the dimensional accuracy and surface finish of the parts. The deformation mechanism of titanium alloys under machining conditions is known to be very different from that of commonly used industrial materials. Therefore, the effect of cooling methods on dimensional accuracy and surface finish in machining titanium is of particular interest. This paper investigates experimentally and analytically the influence of cooling method and cutting parameters on two major dimensional accuracy characteristics of a turned titanium part—diameter error and circularity, and surface finish. Data were analyzed via three methods: traditional analysis, Pareto ANOVA, and Taguchi method. The findings indicate that the cooling method has significant effect on circularity error (contribution ratio 76.75 %), moderate effect on diameter error (contribution ratio 25.00 %), and negligible effect on surface finish (contribution ratio 0.16 %)

Sequence stratigraphic interpretation of a Pennsylvanian (Upper Carboniferous) coal from the Central Appalachian Basin, USA

Peat mires retain a sensitive record of water-table (base-level) fluctuations throughout their accumulation. On this basis, coals provide one of the best opportunities to interpret high-resolution base-level change in ancient non-marine deposits. The petrographic composition of 275 samples collected from 11 localities along a 100km south-west to north-east transect across the regionally extensive (&gt;37000km2) Pennsylvanian (Upper Carboniferous) Fire Clay coal of the Central Appalachian Basin, USA was analysed to determine its internal stratigraphy. The coal is positioned within the late lowstand/early transgressive systems tract of a fourth-order depositional sequence. The results of the petrographic analyses reveal a cyclicity in the composition of the Fire Clay coal, which defines six units that are correlated over more than 100km. Each coal cycle is characterized by a gradual upward transition from vitrinite-dominated to inertinite-dominated coal, which represents a 'drying-up' succession. Increased concentrations of resistant peat components at the top of the drying-up successions indicate reduced peat accumulation rates associated with slowing rate of water-table rise, and may represent a residue of peat remaining from a phase of exposure and erosion resulting from a falling water table. These drying-up successions are bound by surfaces that display an abrupt coal facies shift from inertinite-rich to vitrinite-rich coal, representing a rapid water-table rise. Each cycle represents markedly different mire conditions with different aerial distributions, which supports the notion of temporal disconnection between each unit of coal, and suggests that considerable time may be 'locked-up' in unit bounding exposure surfaces. Recognition that the rate of peat accumulation in a mire may vary considerably through time, has important implications for studies which assume that peat and coal successions provide continuous and time-invariant records of base-level fluctuations or palaeoecological change.</p

Assessment of web crippling design provisions for application to proprietary soldier beams

Structures used for temporary works are lightweight so that they are easy to transport, erect and dismantle. Particular care should be taken in their design as local instabilities could arise due to their thin-walled nature. This article presents 12 tests on proprietary soldier beams subjected to two concentrate opposing loads applied simultaneously. The geometry of the proprietary beams feature cold-formed C-shaped sections with web holes connected back to back with internal spacers. In the absence of design rules for application to such members, the experimental results are used in the present investigation to assess the suitability of the provisions for the web crippling design of coldformed steel members as well as existing design methods from the literature, which account for the effect of perforations in the web. Experimental and predicted resistances are compared and design recommendations are provided.Leada Acro

Particulate Matter in the Hospital Environment

Investigations of particle concentration levels and size distribution were conducted in the complex hospital system of the Royal Children’s and the Royal Brisbane Hospitals. The aim of the measurements was to provide an indication of particulate sources in the hospital environment and relate particle characteristics to the operating parameters of the hospitals. The measurements were performed using the most advanced instrumentation for size classification in the submicrometer and supermicrometer levels. The conclusions from the investigation were (i) that indoor concentration levels of particle numbers are closely related to outdoor concentration levels, indicating that outdoor particulates were the main contributor to the indoor particulates in the hospitals under investigations and (ii) that the performance of filtration/ventilation systems is the most critical parameter in reducing general particulate concentration levels in those hospital units where medical procedures can result in generation of potentially hazardous organic aerosols