[pt] O objetivo deste trabalho foi desenvolver uma metodologia para quantificação, por microscopia, do microconstituinte Austenita-Martensita (AM) em um aço de alta resistência e baixa liga (ABRL) da classe API5LX80. Foram obtidas imagens de Microscopia Ótica (MO) em campo claro e Eletrônica de Varredura (MEV), nos modos de elétrons secundários (SE) e retroespalhados (BSE). As imagens foram quantificadas por Processamento e Análise Digital de Imagens (PADI) e os resultados dos dois tipos de microscopia foram comparados. O principal desafio foi discriminar AM em meio a uma microestrutura multifásica complexa, com frações variadas de ferrita, bainita e do próprio AM. Para revelar a presença de AM foram testadas diferentes sequências de ataques químicos e eletrolíticos. Os resultados demostraram que o ataque químico misto, acrescentando um passo Lepera modificado gerou uma melhora acentuada do contraste em imagens de MO e de MEV no modo BSE. Imagens de MEV no modo SE apresentaram problemas de borda devido à posição do detector de elétrons, o que impediu a correta discriminação das regiões de AM. No modo BSE, a tensão de aceleração foi reduzida para 5 kV, para reduzir a penetração do feixe de elétrons e aumentar o contraste devido à fina camada de AM. Estas imagens foram filtradas para reduzir ruído e segmentadas por limiar simples para quantificar o AM. Nas imagens coloridas de MO, o AM foi segmentado por limiares nos espaços de cor RGB e HSB e em seguida foi quantificado. Utilizando Microscopia Co-Localizada (MCL) foram obtidas imagens de campos idênticos no MEV e no MO, permitindo comparar as técnicas. Mostrou-se que, no mesmo aumento, a microscopia ótica tende a subestimar a fração de AM quando comparada à microscopia eletrônica de varredura, no modo BSE. / [en] This dissertation proposed the development of a quantification method, by microscopy, of the microconstituent Martensite-Austenite (MA) in a High Strength Low Alloy (HSLA) steel of the API5LX80 class. Images were obtained by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), in secondary electron (SE) and backscattered electron (BSE) modes. Digital Image Processing and Analysis (IA) was employed to process and quantify the acquired images and compare the results of the two types of microscopy. The main challenge was to discriminate the MA amidst a complex multiphase microstructure with varying fractions of ferrite, bainite and MA itself. To reveal the MA different chemical and electrolytic etching sequences were tested. The results showed that a mixed combination with an extra step of modified LePera etchant issued the best contrast for both OM and BSE mode SEM. SEM images in SE mode showed edge problems due to the location of the electron detector, what prevented the correct discrimination of MA regions. The accelerating voltage in the BSE mode was reduced to 5 kV which in turn decreased beam penetration and increase contrast due to the thin MA layer. These images were filtered to reduce noise and segmented by a simple threshold to quantify MA. In the color OM images MA was segmented by thresholds in the RGB or HSB color spaces and subsequently quantified. Employing Co-Site Microscopy images of identical fields acquired by OM and SEM, a direct comparison of the techniques was allowed. It was show that, for the same magnification, optical microscopy tends to underestimate the MA fraction when compared to electron microscopy in BSE mode.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Aerospace Report No. TOR-0059(6110-01)-3, section 1.3.3 outlines the design and performance requirements of SGLS (Space Ground Link Subsystem) uplink services equipment. This modulation system finds application in the U.S. Air Force satellite uplink commanding system. The SGLS signal generator is specified as an FSK (Frequency Shift Keyed)/AM (Amplitude Modulation)/PM (Phase Modulation) sub-carrier modulator. GDP Space Systems has implemented, on a single 6U-VME card, a SGLS signal generator. The modulator accepts data from several possible sources and uses the data to key one of three FSK tone frequencies. This ternary FSK signal is amplitude modulated by a synchronized triangle wave running at one half the data rate. The FSK/AM signal is then used to phase modulate a tunable HF (High-Frequency) sub-carrier. A digital design approach and the availability of integrated circuits with a high level of functionality enabled the realization of a SGLS signal generator on a single VME card. An analog implementation would have required up to three rack-mounted units to generate the same signal. The digital design improve performance, economy and reliability over analog approaches. This paper describes the advantages of a digital FSK/AM/PM modulation method, as well as DDS (Direct Digital Synthesis) and digital phase-lock techniques.