Search results for "technical"
showing 10 items of 955 documents
Vibration Control of a High-Speed Precision Servo Numerically Controlled Punching Press: Multidomain Simulation and Experiments
2017
A three-degree-of-freedom mathematical vibration model of a high-speed punching press was developed in order to explore the vibration modes of the punching press. A multidomain model of the punching press was established to predict the kinematic state during different conditions, as well as the effects of load fluctuation on the motor speed. Experimental measurements of the acceleration of the punching press were carried out. The results comparison reveals that the multidomain model is consistent with the vibration model and the experimental measurements. Modal analysis and structure modification of the punching press were conducted. The foundation at the base of the punching press was impr…
Energy harvesting using piezoelectric transducers for suspension systems
2020
Abstract Energy harvesting by using functional materials in suspension systems bear potential to win-back certain (even if low) amounts of vibrational energy, otherwise dissipated via the conventional (passive) dampers. Piezoelectric (PE) ceramics are functional materials that can be used for transforming mechanical energy into electrical and vice versa. In this paper, we study the capabilities and efficiency of energy harvesting (EH) with PE transducers under two different kinds of external excitation: i) Periodic and ii) stochastic. An appropriate nonlinear lumped parameter electromechanical model (LPEM) is brought into the two-port network notation. Laboratory experiments were conducted …
An energy efficiency analysis of Single Point Incremental Forming as an Approach for Sheet Metal Based Component Reuse
2020
Abstract Producing materials causes about 25% of all anthropogenic CO2 emissions. Metals play a significant role, steel and aluminum account for 24% and 3% of worldwide material related emissions respectively. Fostering resources efficiency strategies in the field of sheet components could lead to a significant environmental impact reduction. Reshaping could be one of the most efficient strategy to foster material reuse and lower the environmental impact due to material production. Specifically, for aluminum recycling, the overall energy efficiency of conventional route is very low and, more importantly, permanent material losses occur during re-melting because of oxidation. The present pap…
The shear strength of Opalinus Clay shale in the remoulded state
2020
Abstract The Opalinus Clay shale formation is considered as a potential host geomaterial for the Swiss deep geological repository for radioactive waste. It presents different facies and it is characterised by a multi-scale heterogeneous composition, by a typical fissile structure with well-defined bedding planes and by anisotropic hydro-mechanical behaviour. This peculiar complexity makes it difficult to assign a unique set of geomechanical parameters to the material. This paper presents an experimental study aimed at characterising the lowest values of the shear strength parameters. In this sense, the shear behaviour was investigated on remoulded samples where the fabric and the diagenetic…
The impact of the volumetric swelling behavior on the water uptake of gas shale
2018
Abstract Water uptake of gas shales is commonly considered one of the most important factors responsible for fluid loss during flowback operations after hydraulic fracturing. Imbibition experiments cover a key role in this context to analyze the impact of several factors (such as mineralogical composition, fluids composition, anisotropic structure, volumetric swelling) that contribute to the water uptake in these unconventional reservoirs. The aim of this study is the quantification of the impact of the volumetric response (swelling and shrinkage) of gas shales on the water uptake during imbibition and desiccation processes. An experimental methodology to quantify the volumetric response du…
The open metastable structure of a collapsible sand: fabric and bonding
2015
This paper deals with the compositional and textural characteristics determining open metastable structures in the pleistocenic sand outcropping in the Agrigento district (Sicily). The aim of the study was to individuate the bonding types occurring between grains that could generate matric suction phenomena. The composition and microfabric were characterised by means of granulometry, porosimetry, permeability, optical and ESEM-EDS microscopy, thermogravimetry and XR diffractometry, electric conductivity, and ionic chromatography. The data thus acquired show that the skeleton of the sand is constituted mostly by bioclasts and microfossils, calcite and quartz monocrystalline grains. Moreover,…
Comparison of fully non-stationary artificial accelerogram generation methods in reproducing seismicity at a given site
2020
Abstract Seismic input modelling is a crucial step when Non-Linear Time-History Analyses (NLTHAs) are performed, the seismic response of structures being highly responsive to the input employed. When natural accelerograms able to represent local seismicity are not available, the use of generated accelerograms is an efficient solution for input modelling. The aim of the present paper is to compare four methods for generating fully non-stationary artificial accelerograms on the basis of a target spectrum, identified using seven recorded accelerograms registered in the neighbourhood of the construction site during a single event, assumed as target accelerograms. For each method, seven accelero…
Resilience to flash floods in wetland communities of northeastern Bangladesh
2018
Globally, a number of catastrophic hydrometeorological hazards occurred in 2017 among which the monsoon floods in South Asia was particularly disastrous, killing nearly 1200 people in India, Nepal and Bangladesh. The wetland region (Haor) of northeastern (NE) Bangladesh was severely affected by flash floods early in 2017, affecting nearly 1 million households and damaging US $450 million worth of rice crops. This study investigates how the NE Bangladesh experienced the 2017 flash floods, and to what degree the wetland communities are vulnerable and resilience to flash floods. Focus group discussion, key informant interviews, and household questionnaire surveys (n = 80) were applied in the s…
A systematic review of human behaviour in and around floodwater
2020
Abstract Flooding can have a major impact on people's safety and livelihood. Understanding people's flood-related behaviours may assist in the development of more effective strategies aimed at lessening the impact of floods including mortality and morbidity. This systematic review examined peer-reviewed literature published from January-1989 to April-2019 on human behaviour in and around floodwater to identify behaviour patterns as well as protective and risk factors. We extracted three main themes from a thematic analysis of included studies (N = 54): activities and risk-taking behaviours (n = 24); loss reduction, knowledge, and warnings (n = 37); and diet and hygiene (n = 4). This review …
The impact on disaster governance of the intersection of environmental hazards, border conflict and disaster responses in Ladakh, India
2018
Abstract The Indian border region of Ladakh, in Jammu and Kashmir State, has a sensitive Himalayan ecosystem and has experienced natural hazards and disasters of varying scales over the decades. Ladakh is also situated on a fault-line of multiple tensions, including ongoing border disagreements and intermittent conflict with China and Pakistan. The Indian army has thus become a permanent fixture in the region. This paper examines the implications of the intersection of these environmental and security factors for disaster governance in the region. Using Social Domains theory, the paper argues first, that a hazard-centred paradigm of ‘universal’ disaster science emerges from the colonial per…