Evaluating Identification and Sorting Technologies for Improved Ferrous and Non-Ferrous Recycling

Metals recycling is one of the oldest industries in the United States that now employs over 530,000 individuals. It has always played a significant role in the economy, contributing $109.78 billion to the US economy in 2018. Furthermore, recycling supplies extensive goods and services, the Institute of Scrap Recycling Industries (ISRI) reported that every year greater than 900M Mt of scrap (~2 billion pounds) are consumed by manufactures globally, equating to 40% of the raw material demand. Additionally, as climate change becomes a greater threat, we must seek practices to lessen our carbon footprint, and recycling helps to reduce the environmental impact of metal production. Relying on this industry as an alternative to make-take-waste habits means understanding how the industry’s efficiency is being challenged by growing feed volumes of diverse, complex product designs. This work details the internal and external factors that impact the development of ferrous and nonferrous recycling operations. This knowledge is then applied to design and perform an extensive “true to yard” analysis with technologies that have potential for addressing inbound inspection and material identification challenges. These results allowed us to understand the limitations that would arise when attempting their deployment at material handling facilities, and then use these factors to build a model capable of quantifying and comparing these techniques, which is not available in previous literature. Inbound inspection and material identification are critical; they are the first opportunity once material is received to prevent comingling, downcycling, and contamination. Scrap yards identify and sort specific alloys from large quantities of mixed metals by means of visual and cognitive recognition with the aid of a few standard tools (a magnet, file, acids, and/or grinding wheel). This work tested handheld analyzers (HHs) that utilize x-ray fluorescence (XRF) and laser induced breakdown spectroscopy (LIBS) technology to determine the level of technological assistance they can provide to improving identification during the inspection process. Beforehand, we had a good indication of how HHs perform on material that has clean, smooth, uncoated surfaces (prompt scrap) but, what we aim to find is their response when used on “unprepared materials,” like those coming out of stock that are old, used, weathered, and/or warped (obsolete scrap). For these instruments to be deemed useful for inbound inspection/ identification purposes, it is crucial to understand and evaluate their limitations on scrap that is not altered and thus, true to a yard setting. Results indicate that in their current state, HHs can inform and verify content for a significant range of materials. They also show grade matching (identification of an alloy by name) is possible but less likely on unprepared scrap. However, the ability to register and share elemental composition percentages at rapid speeds, allows a trained user to know immediately what contaminants are present, often being high levels of Si and Fe. In addition to understanding how these technologies perform under real world conditions, it is also important to quantify whether their benefits outweigh their costs. This work examined five different scenarios for sorting and identification, each scenario offering different levels of alloy-specific sorting capabilities. The model that was created allowed for return on investment (ROI) comparisons, and evaluated the impacts of different market conditions, changes in volume, volume distribution, and uncertainty. This technoeconomic assessment showed that even a high amount of comingled material can be profitable at high volumes under certain market conditions. Although, comingling led to diminished profits, where segregating proved beneficial even at lower volumes. As we continue to invest, educate, and execute sustainable practices, we must understand that recycling should only come as an attempt after we have exhausted our efforts to reduce and reuse. Moreover, we can work to obtain a better balance along the supply chain by encouraging and creating more practices like design for recycling (DfR) and extended producer responsibility. Being that these behaviors will require a lot of societal reform, we need to ensure that we work to reduce landfill feed by providing the recycling industry with the tools and practices that are effective and efficient at getting materials identified and sorted

Parameters affecting inductive displacement sensors

An investigation of the limitations of inductive displacement sensors (IDSs) was conducted with the use of electromagnetic finite element analysis (FEA). A comparison of displacement sensing technologies highlighted the advantages of EDSs in harsh industrial environments, but an understanding of the operation of IDSs showed that they are limited by the influence of target material, width and offset. It was proposed that studying the electromagnetic field around IDSs could reveal more information than was available from the simple impedance measurements employed by a commercially available IDS.A test coil sensor and signal processing system was designed and the result was a reliable system for measuring the magnetic field around the IDS. Experiments showed that the 1 MHz field had an amplitude of 5 x 10(^-6) T at the base of the IDS and two- and three-dimensional FEA models were constructed that gave closely matching central field values. The unreliability of the IDS for different target materials was demonstrated experimentally. FEA simulations showed that changing target permeability and varying target displacement both altered the whole field amplitude uniformly. This showed that it was not possible to counteract the target dependence by monitoring the field with the test coil system in this way. Further FEA simulations revealed field patterns that changed with target offset. An experiment with the test coil system confirmed that it was possible to use the change in lobe amplitude to measure the offset of the target; for example when target displacement d, = 25 mm and offset = 1.2 times the IDS coil diameter, the distance error was 3.6 %, which corresponded to a normalised test coil output of 0.54. A similar effect was found from target width FEA simulations. Hence it was possible to correct the output signal from the IDS coil to counteract the effect of an offset small target

A Multidisciplinary Analysis of Frequency Domain Metal Detectors for Humanitarian Demining

This thesis details an analysis of metal detectors (low frequency electromagnetic induction devices) with emphasis on Frequency Domain (FD) systems and the operational conditions of interest to humanitarian demining. After an initial look at humanitarian demining and a review of their basic principles we turn our attention to electromagnetic induction modelling and to analytical solutions to some basic FD direct (forward) problems. The second half of the thesis focuses then on the analysis of an extensive amount of experimental data. The possibility of target classification is first discussed on a qualitative basis, then quantitatively. Finally, we discuss shape and size determination via near field imaging

Modelling and experimental investigation of eddy current distribution for angular defect characterisation

Current industrial requirements for nondestructive testing demand defect quantification rather than simple defect detection. This is not a simple task as defects in components, such as cracks, rarely have a simple geometrical shape. Therefore, the influence of defect shape and orientation and its effect on the inspection results needs to be addressed to avoid misinterpretation of the response signals and for a quantitative characterisation of defects. Finite element method (FEM) numerical simulations for eddy current non-destructive evaluation (ECNDE) can provide information on how the induced eddy current interacts with defects and the effect of defect shape and geometry towards the results. Through the analysis of the simulation results, links can be established between the measurements and information relating to the defect, such as 3-D shape, size and location, which facilitates not only forward problem but also inverse modelling involving experimental system specification and configuration; and pattern recognition for 3-D defect information. This work provides a study of the characterisation of angular defects through the technique of visualisation and mapping of magnetic field distribution for pulsed eddy current (PEC) and temperature distribution for PEC thermography. 3-D FEM simulations are utilised to provide the guidelines for experimental designs and specifications; understanding of the underlying physics surrounding a particular defect; and means for features extraction from the acquired responses. Through the study, defect Quantitative Non-destructive Evaluation (QNDE) has been established using the features extracted from the mapping by taking into consideration the angular characteristic of defect in the inspection results. Experimental investigations are then performed to verify the simulation results and the feasibility of the proposed techniques and extracted features to be used in acquiring information about the angular defect. The work concludes that the technique of mapping the resultant distribution from the interaction of eddy currents and defects has provided the vital information needed for defect characterisation. Features extracted from the mapping via numerical investigations have provided the means for the QNDE of angular defects. The work shows that the technique and features introduced has provided an alternative way for defect characterisation and QNDE, which also can be extended its application to other industrial components and research field.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Characterisation of surface and sub-surface discontinuities in metals using pulsed eddy current sensors

Due primarily to today's rigorous safety standards the focus of non-destructive testing (NDT) has shifted from flaw detection to quantitative NIDT, where characterisation of flaws is the objective. This means information such as the type of flaw and its size is desired. The Pulsed Eddy Current (PEC) technique has been acknowledged as one of the potential contenders for providing this additional functionality, due to the potential richness of the information that it provides. The parameters mainly used to obtain information about the detected flaws are the signal's peak height and arrival time. However, it has been recognised that these features are not sufficient for defect classification. In this research, based on a comprehensive literature survey, the design of PEC systems and the interpretation of PEC signals, mainly for flaw classification, are studied. A PEC system consisting of both hardware and software components has been designed and constructed to facilitate the research work on PEC signal interpretation. After a comparative study of several magnetic sensing devices, probes using Hall device magnetic sensors have also been constructed. Some aspects related to probe design, such as coil dimensions and the use of ferrite core and shielding have also been studied. A new interpretation technique that uses the whole part of PEC responses and is able to produce more features has been proposed. The technique uses Principal Component Analysis (PCA) and Wavelet Transforms, and attempts to find the best features for discrimination from extracted time and frequency domain data. The simultaneous use of both temporal and spectral data is a logically promising extension to the use of time domain only with the signal-peak-based technique. Experiments show that the new 1 technique is promising as it performs significantly better than the conventional technique using peak value and peak time of PEC signals in the classification of flaws. A hierarchical structure for defect classification and quantification has been presented. Experiments in the project have also shown that the signal-peak-based technique cannot be used for flaw detection and characterisation in steels, both with and without magnetisation. The new proposed technique has shown to have potential for this purpose when magnetisation is used. The new technique proposed in the report has been successfully used for ferromagnetic and non-ferromagnetic materials. It has also been demonstrated that the new proposed technique performs better in dynamic behaviour tests, which shows its better potential for on-line dynamic NDT inspection which is required in many industrial applications. In addition to testing calibrated samples with different discontinuities, a study case using an aircraft lap joint sample from industry has further supported the statement regarding the potential of the new technique.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Design and fabrication of precision carbon nanotube-based flexural transducers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 179-197).As mechanical devices move towards the nanoscale, smaller and more sensitive force and displacement sensors need to be developed. Currently, many biological, materials science, and nanomanufacturing applications could benefit from multi-axis micro- and nanoscale sensors with fine force and displacement resolutions. Unfortunately, such systems do not yet exist due to the limitations of traditional sensing techniques and fabrication procedures. Carbon nanotube-based (CNT) piezoresistive transducers offer the potential to overcome many of these limitations. Previous research has shown the potential for the use of CNTs in high resolution micro- and nanoscale sensing devices due to the high gauge factor and inherent size of CNTs. However, a better understanding of CNT-based piezoresistive sensors is needed in order to be able to design and engineer CNT-based sensor systems to take advantage of this potential. The purpose of this thesis is to take CNT-based strain sensors from the single element test structures that have been fabricated and turn them into precision sensor systems that can be used in micro- and nanoscale force and displacement transducers. In order to achieve this purpose and engineer high resolution CNT-based sensor systems, the design and manufacturing methods used to create CNT-based piezoresistive sensors were investigated. At the system level, a noise model was developed in order to be able to optimize the design of the sensor system. At the element level, a link was established between the structure of the CNT and its gauge factor using a theoretical model developed from quantum mechanics. This model was confirmed experimentally using CNT-based piezoresistive sensors integrated into a microfabricated test structure. At the device level, noise mitigation techniques including annealing and the use of a protective ceramic coating were investigated in order to reduce the noise in the sensor. From these investigations, best practices for the design and manufacturing of CNT-based piezoresistive sensors were established. Using these best practices, it is possible to increase the performance of CNT-based piezoresistive sensor systems by more than three orders of magnitude. These best practices were implemented in the design and fabrication of a multi-axis force sensor used to measure the adhesion force of an array of cells to the different material's surfaces for the development of biomedical implants. This force sensor is capable of measuring forces in the z-axis as well as torques in the [theta]x and [theta]y axis. The range and resolution of the force sensor were determined to be 84 [mu]N and 5.6 nN, respectively. This corresponds to a dynamic range of 83 dB, which closely matches the dynamic range predicted by the system noise model used to design the sensor. The accuracy of the force sensor is better than 1% over the device's full range.by Michael A. Cullinan.Ph.D

Modeling of integrated inductors for RF circuit design

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnic

Finite Element Modelling and Investigation of High Speed, Large Force and Long Lifetime Electromagnetic Actuators

The prime topic of research presented in this report is the development and use of computer-based modelling methodologies for design and performance modelling of an industrial component in the food sorting industry, exemplified in actuators used in bulk food sorting machines. Electromagnetic (EM) solenoid actuators are widely used in many applications such as the automobile, aerospace, printing and food industries where repetitive, often high-speed linear or rotating motions are required. In some of these applications they are used as high-speed 'switching' valves for switching pneumatic channels. The complex nature of electromagnetic, motional and thermal problems is discussed. The methodologies for FE modelling of such high-performance actuators are developed and discussed. These are used for modelling, design, performance evaluation and prediction of the above high-speed actuators. Modelling results showing some of the key design features of the actuators are presented in terms of force produced as a function of various design parameters. Optimization calculations for the dynamic behaviour are executed at the design process of electromagnetic actuators. Finite element method used for modelling the electromagnetic actuator model. The models are implemented in the design software Opera-2d/3d and were tested at different tasks. The capability is shown at a magnetic actuator. Magnetically controlled shape memory materials are a new way to produce motion and force. The material changes shape in a magnetic field. Usual applications of the material are actuators that produce linear motion. MSM actuator type is designed and initial investigation presented in this thesis. Finite element modelling methodologies have been developed for the design and investigation of electromagnetic and thermal behaviours of high-speed, large-force and long-lifetime solenoid actuators used as pneumatic ejector valves in optical sorting machines for bulk food sorting. Operating at frequencies between 150-300 Hz, these actuators are unique in terms of the large force they produced (8-19 N) with very long lifetime (2-5 billion cycles)