Weldability of powder bed fusion fabricated stainless steel 316L sheets to cold rolled sheet metal

Weldability of powder bed fusion (PBF) fabricated components has come to discussion in past two years due to resent developments in the PBF technology and limited size of the machines used in the fabrication process. This study concentrated on effects of energy input of welding on mechanical properties and microstructural features of welds between PBF fabricated stainless steel 316L sheets and cold rolled sheet metal of same composition by the means of destructive testing and microscopic analysis. Optical fiber diameter, laser power and welding speed were varied during the experiments that were executed following one variable at a time (OVAT) method. One of the problems of welded PBF fabricated components has been lower elongations at break comparing to conventionally manufactured components. Decreasing energy input of the laser keyhole welding decreased elongations at break of the welded specimens. Ultimate tensile strengths were not affected significantly by the energy input of the welding, but fracturing of the specimens welded using high energy input occurred from the weld metal. Fracturing of the lower energy input welds occurred from the PBF fabricated base metal. Energy input was found to be critical factor for mechanical properties of the welds. Multioriented grain growth and formation of neck at fusion zone boundary on the cold rolled side of the weld was detected and suspected to be result from weld pool flows caused by differences in molten weld pool behaviour between the PBF fabricated and cold rolled sides of the welds.

Fusion of Data from Quadcopter’s Inertial Measurement Unit Using Complementary Filter

A quadcopter is a helicopter with four rotors, which is mechanically simple device, but requires complex electrical control for each motor. Control system needs accurate information about quadcopter’s attitude in order to achieve stable flight. The goal of this bachelor’s thesis was to research how this information could be obtained. Literature review revealed that most of the quadcopters, whose source-code is available, use a complementary filter or some derivative of it to fuse data from a gyroscope, an accelerometer and often also a magnetometer. These sensors combined are called an Inertial Measurement Unit. This thesis focuses on calculating angles from each sensor’s data and fusing these with a complementary filter. On the basis of literature review and measurements using a quadcopter, the proposed filter provides sufficiently accurate attitude data for flight control system. However, a simple complementary filter has one significant drawback – it works reliably only when the quadcopter is hovering or moving at a constant speed. The reason is that an accelerometer can’t be used to measure angles accurately if linear acceleration is present. This problem can be fixed using some derivative of a complementary filter like an adaptive complementary filter or a Kalman filter, which are not covered in this thesis.

Traité de l'orthographe franc̜oise, en forme de dictionaire. Tome 1 / , enrichi de notes critiques et de remarques sur l'étymologie et la prononciation des mots, le genre des noms, la conjugaison des verbes irréguliers et les variations, avec une préface grammaticale, un Traité de versification franc̜oise et un Dictionnaire géographique. Par P. Restaut. Nouvelle édition revue, corrigée, augmentée et prosodiée d'après les principes d'Olivet... Par Claude-Félix Roger... Tome I. A-K [-II. L-Z]

Comprend : Abrégé du traité de l'orthographe géographique ; Abrégé des regles de la versification franc̜oise

Traité de l'orthographe franc̜oise, en forme de dictionaire. Tome 2 / , enrichi de notes critiques et de remarques sur l'étymologie et la prononciation des mots, le genre des noms, la conjugaison des verbes irréguliers et les variations, avec une préface grammaticale, un Traité de versification franc̜oise et un Dictionnaire géographique. Par P. Restaut. Nouvelle édition revue, corrigée, augmentée et prosodiée d'après les principes d'Olivet... Par Claude-Félix Roger... Tome I. A-K [-II. L-Z]

Comprend : Abrégé du traité de l'orthographe géographique ; Abrégé des regles de la versification franc̜oise