A.B. Pereira

Mode I interlaminar fracture of carbon/epoxy multidirectional laminates

An experimental study was conducted on the mode I interlaminar fracture of carbon/epoxy multidirectional specimens with starter delaminations in 0/0 and 0/θ interfaces. The specimens selected for Double Cantilever Beam (DCB) tests had [(02/90)6/02//(02/90)6/02] and [(02/90)6/02//θ/(02/90)6/02] stacking sequences, where // denotes the position of the starter delamination and θ = 22.5 to 90 degrees. The incorporation of the thick symmetric [(02/90)6/02] block of 20 plies aimed at minimising elastic couplings related problems, such as non-uniform width-wise distributions of the strain energy release rate GI, spurious modes and effects of residual stresses. This was verified in preliminary three-dimensional (3D) Finite Element (FE) analyses, which also showed the applicability of the Corrected Beam Theory data reduction scheme. The DCB specimens were tested according to the procedures defined in the ISO 15024:2001 standard for unidirectionally reinforced specimens. In the tests, intraply damage occurred in the θ-oriented ply soon after initiation from the starter crack, as it is commonly observed in multidirectional specimens. For θ = 22.5 and 45 degrees, a second crack propagated close to a neighbouring interface, while for θ = 67.5 and 90 degrees the starter crack ran inside the θ-oriented ply and proceeded in a wavy propagation trajectory. This resulted in extensive fibre bridging and pronounced R-curves with artificially high final values of the critical strain energy release rate, GIc. Therefore, only GIc values of initiation could be considered true interlaminar properties. Moreover, it was found that they were fairly independent of the ply angle θ. An additional FE analysis of the interlaminar stresses ahead of the crack tip was performed to interpret the delaminating interface effect on GIc values. The results indicated the existence of an interface independent fracture toughness, KIc, probably resin controlled, thus reinforcing the idea that the measured initiation GIc were pure interlaminar properties.

Strength of adhesively bonded stainless steel joints

An experimental study was conducted on the strength of adhesively bonded stainless steel joints, prepared with two epoxy and one acrylic adhesives. The mode I critical strain energy release rate, GIc, was measured in double cantilever beam (DCB) tests. Lap-shear tests were performed on various types of single-lap and double-lap joints. Finite element analyses were used to explain joint strength results. It was found that the strengths of epoxy adhesive joints depended mostly on the level of peel stresses near the bondline edges. When expressed in terms of effective overlaps, joint strengths were generally insensitive to the presence of defects created at the overlap ends.

Using the eServices platform for detecting behavior patterns deviation in the elderly assisted living: a case study.

Worlds aging population is rising and the elderly are increasingly isolated socially and geographically. As a consequence, in many situations, they need assistance that is not granted in time. In this paper, we present a solution that follows the CRISP-DM methodology to detect the elderlys behavior pattern deviations that may indicate possible risk situations. To obtain these patterns, many variables are aggregated to ensure the alert system reliability and minimize eventual false positive alert situations. These variables comprehend information provided by body area network (BAN), by environment sensors, and also by the elderlys interaction in a service provider platform, called eServices—Elderly Support Service Platform. eServices is a scalable platform aggregating a service ecosystem developed specially for elderly people. This pattern recognition will further activate the adequate response. With the system evolution, it will learn to predict potential danger situations for a specified user, acting preventively and ensuring the elderlys safety and well-being. As the eServices platform is still in development, synthetic data, based on real data sample and empiric knowledge, is being used to populate the initial dataset. The presented work is a proof of concept of knowledge extraction using the eServices platform information. Regardless of not using real data, this work proves to be an asset, achieving a good performance in preventing alert situations.

Removing barriers to promote social computing among senior population

Smartphones and tablets proliferation enabled by accessible prices and also by the inclusion of sensing abilities promotes their use in several areas, such as healthcare. It opens new horizons in the field of continuous and noninvasive monitoring and support to population, namely, to seniors. Despite the great benefits that mobile sensing and social computing could provide to increase elderlys quality of life, many studies have shown that elderlies deal with difficulty with Information and Communication Technology (ICT). In this paper we present a solution to overcome barriers between elderlies and their ICT usage in order to potentiate all the benefits provided from mobile sensing and social computing. A survey on guidelines, standards, and advice regarding usability and accessibility issues when developing solutions for elderly people was carried out. This survey was made having in mind that senior population have singular requirements due to age related changes and also frequently technological illiteracy. We have identified and applied the most important guidelines to our solution. A prototype was made using responsive design in order to be adaptable to any type of devices. Regarding evaluation, usability tests and semistructured interviews were conducted in real scenario.

Management Model for Wireless Broadband Networks

Currently, due to questions of financial order, the Internet Service Providers do not invest in rural areas, because the investment does not pay. This fact originates, more and more, the appearance of the so called WBN (Wireless Broadband Networks), that are going to supply Internet access to the populations, discriminated by this circumstance. The aspects related to the management of these networks are normally forgotten and today there is a lack of economically and technical viable solutions, that can efficiently help with this function, without use an enterprise solution. After an intensive research of commercial and opensource solutions of wireless networks management, it was checked an absence of an economically viable solution as well as an absence of a model of management for the WBN. This article contributes to the definition of a management model of these networks, using opensource tools. The proposal model is based on a centralized solution that congregates several modules of opensource tools, which can be able to respond to a wide range of features identified in the model. The simulation shows how the model presented, can be practicable and able to cover several functions in WBN management.

Measuring Torque and Temperature in a Rotating Shaft Using Commercial SAW Sensors

Real-time monitoring of torque in a rotating shaft is not easy to implement with technologies such as optic fiber sensors or strain gages. Surface acoustic wave (SAW) sensors are wireless and passive and can be used to monitor strain in moving parts. Commercial solutions (sensors, antennas and interrogation unit) can easily be purchased from some companies; however, they are not customized and may not meet the specificity of the measurements. In order to evaluate the adequacy of commercial off-the-shelf (COTS) solutions, temperature and strain sensors fabricated by SENSeOR (Besançon, France) were mounted on a load cell. The sensors were calibrated using a thermal chamber and a universal testing machine. The load cell was then assembled together with a steel shaft that rotated at different speeds inside an oven. The commercial antennas were replaced with an RF (radio frequency) coupler and the sensors were interrogated with the commercial interrogation unit. The influence of rotation in the accuracy on the measurements, as well as the adequacy of the sensors structure, was evaluated. It can be concluded that SAW sensors can be used to measure temperature or torque in a rotating environment; however, some customization of the components is required in order to overcome the limitations posed by COTS sensing solutions.

Active and Assisted Living Ecosystem for the Elderly

A novel ecosystem to promote the physical, emotional and psychic health and well-being of the elderly is presented. Our proposal was designed to add several services developed to meet the needs of the senior population, namely services to improve social inclusion and increase contribution to society. Moreover, the solution monitors the vital signs of elderly individuals, as well as environmental parameters and behavior patterns, in order to seek eminent danger situations and predict potential hazardous issues, acting in accordance with the various alert levels specified for each individual. The platform was tested by seniors in a real scenario. The experimental results demonstrated that the proposed ecosystem was well accepted and is easy to use by seniors.

Experimental validation of numerical model for asymmetric deep drawing of DP780 steel sheet using digital image correlation

A validated numerical model for in-plane stress/strain prediction is essential in understanding the deformation behaviour of sheet metal forming process, in particular, asymmetric deep drawing of advanced high strength steel sheet. In this work, the Yld2000-2d anisotropic yield criterion integrated with the initial homogeneous anisotropic hardening model was employed to describe the complex material behaviours of DP780 steel as well as the adoption of Yoshida chord model for elastic modulus degradation. Digital image correlation technique was utilized to measure the in-plane strain and shape deviation of the developed P- channel. The validity of the numerical model was assessed by comparing the predicted strain distribution and twist springback with the measured results. It indicates that the developed numerical model based on the selected constitutive models is acceptable for the deformation analysis, although the predicted discrepancies still exist.

Hardening behavior and texture evolution of TWIP steel during strain path change

Polycrystal materials exhibit large changes in the flow stress and hardening behavior during the strain path change. Such changes are related with the crystallographic texture anisotropy and the rearrangement of dislocation structure during the pre-loading. These effects have been captured by a dislocation hardening model embedded in the visco-plastic selfconsistent (VPSC) model. In this work, the texture evolution and mechanical behavior of TWIP steel during the strain path change are investigated. The experimental studies are carried out on rolled TWIP steel sheet. The mechanical responses are obtained under tensile tests along rolling direction, followed by tension along the directions with 0° and 90° from the pre-loading direction. The simulated results of strain-stress curves and the texture evolution are in good agreement with the experimental data.

Scheduling with sequence-dependent batch setup times: planning tests for a pharmaceutic industry

In this work, we propose an approach for a real sequence-dependent batch setup times scheduling problem arising in a pharmaceutical company. A legal obligation for the pharmaceutical industry is to monitor the quality of their products during its life cycle. The development of new pharmaceutical products (medicines) leads to a high number of batches to be tested in order to accomplish with certain regulatory obligations regarding maintaining safeguards on quality and safety. The time lines are critical in this process. The problem is how to manage and schedule a number of tests, that require setups and obey to certain precedence relations, to avoid delays in the answers.