Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by John Hainsworth. / B.S.

Orientador: Manoel Cleber de Sampaio Alves / Banca: Marcos Tadeu Tiburcio Gonçalves / Banca: Ivaldo de Domenico Valarelli / Resumo: A utilização de processos de usinagem para dar forma e acabamento é madeira tem sido ampliada muito nos últimos anos, levada pela necessidade de peças que contenham um melhor acabamento superficial atrelado à boa produtividade que é conseguida pelo aperfeiçoamento contínuo de equipamentos e de ferramentas para processar a madeira. Este trabalho utilizou um sistema experimental de torneamento com um novo cabeçote porta-ferramenta, contendo sensores de potência, vibração e emissão acústica acoplados em um torno EMCO Compact 5, muito comum para procedimentos didáticos, adaptados para o processamento de madeiras de pinus spp, a fim de demonstrar pela utilização da instrumentaçãodo processo, pode influenciar positivamente na análise de algum parâmetros como a rugosidade média (Ra) e rugosidade total (Rt), além dos valores de emissão acústica, potência de corte e vibração. A coleta dos dados se mostrou eficiente e precisa para os parâmetros principais de velocidade de avanço em 40 mm/min, 70 mm/min e 100 mm/min e variações de profundidade de corte em 0,5mm; 1,0 mm; e 1,5 mm; com velocidade de corte constante, e o uso de duas ferramentas de metal duro, uma constituída por metal duro polido e sem revestimento e outra ferramenta revestida com diaboreto de titânio. Entre os principais resultados obtidos, nota-se que a ferramenta com revestimento não influenciou na rugosidade média, e proporcionou menor rugosidade total e potência consumida, mas apresentou maiores valores para a vibração e emissão acústica captada durante os experimentos. Com relação ao tipo de madeira, os dados aquisitados estão coerentes, exceto pelos valores de potência consumida, que podem estar ligados a características próprias das peças de madeira usadas / Abstract: The use of machining processes to shape and finish will wood has been greatly expanded in recent years, driven by the need for parts that contain a better surface finish tied will good productivity is achieved by continuous improvement of equipment and tools to process wood. This study used an experimental turning system with a new tool holder head, containing power sensors, vibration and acoustic emission engaged in a lathe EMCO Compact 5, very common for teaching procedures, adapted for the processing of wood pinus spp and eucalyptus spp, to demonstrate the use of the process instrumentation, can positively influence the analysis of some parameters such as the average roughness (Ra), total toughness (Rt), plus the acoustic emission values, cutting performance and vibration. Data collection was efficient and accurate for the main parameters of forward speeds at 40 mm/min, 70 mm/min and 100 mm/min and variations of the cutting depth of 0.5 mm; 1.0 mm; and 1.5 mm; with constant surface speed, and the use of two carbide tools, consisting of a polished carbide and uncoated and coated other tool with titanium diboride. The main results obtained, it is noted that the coating tool did not influence the average roughness, and provided lower total roughness and consumed power, but showed higher values for vibration and acoustic emission captured during the experiments. Regarding the type of wood, obtained data are consistent, except for the consumed power values, which may be linked to characteristics of used pieces of wood / Mestre

<p>Abstract: The process of inspecting welds done in production at Volvo Aero in Trollhättan is timeconsuming and a lot of this time goes into examining faulty objects. The aim of this thesis is to startdevelopment of a system that analyses acoustic emission from cooling welds to determine the qualityof the weld. Our aim is to be able to detect cracks in the material and to give information on thecracks using the data gathered by our sensors. To do this we will use methods to locate sound sourcesand then rate our findings and do some simplifications on the result of our calculations. We willanalyze our calculated data to find crack signatures and classify our findings and give alarms if wefind cracks that are considered too big for comfort. We will also give insight in to future aspects of ourwork and look at ways to improve on our proposed methods. We will discuss our systems pros, consand what things have been taken into consideration during design, and what strategies we proposeto handle the results from the system.</p>

Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xiv, 204 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 190-195).

Electrical resistance and acoustic emission (AE) measurement are jointly used to monitor the degradation in CFRP laminates subjected to tensile tests. The objective of this thesis is to perform a synergertic analysis between a passive and an active methods to better access how these perform when used for Structural Health Moni- toring (SHM). Laminates with three different stacking sequences: [0]4, [02/902]s and [+45/ − 45]2s are subjected to monotonic and cyclic tensile tests. In each laminate, we carefully investigate which mechanisms of degradation can or cannot be detect- ed by each technique. It is shown that most often, that acoustic emission signals start before any electrical detection is possible. This is is explained based on the redundance of the electrical network that makes it less sensitive to localized damages. Based on in depth study of AE signals clustering, a new classification is proposed to recognize the different damage mechanims based on only two parameters: the RA (rise time/amplitude) and the duration of the signal.

No description available.

Slug velocity measurement and flow regime recognition using acoustic emission technology are presented. Two non-intrusive and three intrusive methods were employed to detect the slug regime and measure its velocity using AE sensors. For the non-intrusive methods, AE sensors were placed directly on the exterior of the steel pipe section of the test rig with and without clamps. The intrusive method involved using different waveguide configurations with the AE sensors flush with the inner wall of the pipe. The experimental study presented investigated the application of Acoustic Emission (AE) technology for detecting slug velocity in addition to differentiating flow regime in two-phase (gas/liquid) flow in horizontal pipes. It is concluded that the slug velocity can be determined with acoustic emission (AE) sensors. The results were compared to slug velocities measured using high speed camera (HSC) and Ultrasound Transit Time (UST) techniques with good agreement between the three techniques at low gas void fraction (GVF). However, at high GVF (up to 95%) where the UST technique has limitations in application, the AE and HSC offered a good agreement. Flow regimes were also differentiated by using a combination of AE technology and Kolmogorov–Smirnov test technique. Stratified, slug and bubble regimes were recognised differentiated.

This thesis proposes a bearing condition monitoring system using acceleration and acoustic emission (AE) signals. Bearings are perhaps the most omnipresent machine elements and their condition is often critical to the success of an operation or process. Consequently, there is a great need for a timely knowledge of the health status of bearings. Generally, bearing monitoring is the prediction of the component's health or status based on signal detection, processing and classification in order to identify the causes of the problem. As the monitoring system uses both acceleration and acoustic emission signals, it is considered a multi-sensor system. This has the advantage that not only do the two sensors provide increased reliability they also permit a larger range of rotating speeds to be monitored successfully. When more than one sensor is used, if one fails to work properly the other is still able to provide adequate monitoring. Vibration techniques are suitable for higher rotating speeds whilst acoustic emission techniques for low rotating speeds. Vibration techniques investigated in this research concern the use of the continuous wavelet transform (CWT), a joint time- and frequency domain method, This gives a more accurate representation of the vibration phenomenon than either time-domain analysis or frequency- domain analysis. The image processing technique, called binarising, is performed to produce binary image from the CWT transformed image in order to reduce computational time for classification. The back-propagation neural network (BPNN) is used for classification. The AE monitoring techniques investigated can be categorised, based on the features used, into: 1) the traditional AE parameters of energy, event duration and peak amplitude and 2) the statistical parameters estimated from the Weibull distribution of the inter-arrival times of AE events in what is called the STL method. Traditional AE parameters of peak amplitude, energy and event duration are extracted from individual AE events. These events are then ordered, selected and normalised before the selected events are displayed in a three-dimensional Cartesian feature space in terms of the three AE parameters as axes. The fuzzy C-mean clustering technique is used to establish the cluster centres as signatures for different machine conditions. A minimum distance classifier is then used to classify incoming AE events into the different machine conditions. The novel STL method is based on the detection of inter-arrival times of successive AE events. These inter-arrival times follow a Weibull distribution. The method provides two parameters: STL and L63 that are derived from the estimated Weibull parameters of the distribution's shape (y), characteristic life (0) and guaranteed life (to). It is found that STL and 43 are related hyperbolically. In addition, the STL value is found to be sensitive to bearing wear, the load applied to the bearing and the bearing rotating speed. Of the three influencing factors, bearing wear has the strongest influence on STL and L63. For the proposed bearing condition monitoring system to work, the effects of load and speed on STL need to be compensated. These issues are resolved satisfactorily in the project.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 81-83).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 107-112). Also available in electronic version.