The formation of a stable and adherent oxide layer on the Ti-6Al-4V alloy can improve the mechanical and corrosion resistance of this material. This work studied the creep behavior of Ti-6Al-4V alloy after two different thermal oxidation conditions: at 650 °C for 12 h and at 800 °C for 2 h. In the XRD analysis of the oxidized samples, it was possible to observe the formation of rutile (TiO2) and a displacement of the peaks of α and β phases caused by the dissolution of oxygen. In the creep test at 550 °C, the material oxidized at 800 °C for 2 h showed a greater creep life at 125 MPa, the crack took longer to brake probably due to the greater thickness of the layer. At 550°C and 187.5 MPa the material oxidized at 650 °C for 12h has a better creep life, probably due to the layer more adhered.

This work deals with different stress shot peening conditions’ effects on the compressive residual stress intensity and distribution. The tests were conducted on 15 mm x 70 mm x 1500 mm bars made of quenched and tempered EN 47 spring steel (DIN 51CrV4). Tensile tests and microstructure analysis were applied to guarantee the specification regarding resistance and microstructure. The stress shot peening process was conducted in an unloaded sample and two points bending loading with support distances of 150 and 1000 mm. The maximum flexural tension stresses were 750 and 1500 MPa for the two support distances. The residual stresses were measured by X-ray diffraction in five positions: measurements of samples with deflections were made without deflection, and a total of 95 residual stress measurements were performed before blasting. The compressive residual stresses increased as the calculated loading increased for all test conditions. Otherwise, for the 1000 mm support distance for the higher loading condition, the pre-tension calculated by the ANSYS™ showed higher flexural tension stress in the support position, while the residual stresses were constant between the supports.

The welding of metallic materials by the Friction Stir Welding (FSW) method is a very attractive process for preserving their characteristics, especially for copper and its alloys that require high heat input and present many distortions by traditional methods. However, it is a great challenge to produce welds free of defects and maintain or improve their mechanical properties. In the current literature data on FSW parameters for copper and its alloys are scarce. In this study, tests were performed with a combination of four tool rotations (750, 850, 950, 1050 rev.min-1) and two welding speeds (20 and 60 mm.min-1), maintaining the tool inclination angle in 3° and waiting time of 5 seconds. The objective of this work is to analyze the microstructure and mechanical performance of lap joints of the UNS C19400 alloy joined by FSW. The process temperature was monitored to trace the heating profile of the process, in addition to microhardness and shear strength tests, in addition to optical microscopy for analysis. The joints welded by the parameters Ω 950 rev.mm-1 �� 20mm.min-1 obtained a mechanical performance of 73% compared to the characteristics of the base metal and despite the appearance of volumetric defects at the microstructural level, the metallurgical transformations of recovery and recrystallization of the grains observed in the microstructure played a key role in the result.

OBJETIVO: O objetivo deste estudo é avaliar a resistência mecânica de três montagens de fixador externo linear utilizando pinos de 4,5 mm e de 5,5 mm com alma 3,2mm, e de 5,5 mm com alma de 4,5 mm no setor rosqueado dos pinos. MATERIAL E MÉTODOS: Foram montados fixadores externos lineares em tubos de polipropileno de 500 mm, com um corte obliquo a 45º no seu centro, com dois pinos de Schanz em cada segmento. Foram estudados 18 corpos de prova, divididos em três grupos de seis peças cada. No grupo 1 foram utilizados pinos de Schanz de 4,5 mm, no grupo 2 pinos de 5,5 mm ambos com alma de 3,2 mm e no grupo 3 pinos de 5,5 mm com alma de 4,5 mm de diâmetro. Os testes mecânicos foram realizadas em máquina de torção MT-100, e as medidas de resistência realizadas com 4,5º, 9,0º, 13,5º e 18,0º de torção. RESULTADOS: Os pinos de Schanz de 4,5 mm e alma de 3,2 mm mostraram como média de resistência para as torções de 4,5º, 9,0º, 13,5º e 18,0º, respectivamente: 12,0 N/mm, 21,0 N/mm, 33,0 N/mm e 46,0 N/mm. Os pinos de 5,5 com alma de 3,2 mm mostraram como resistência média: 13,2 N/mm, 25,3 N/mm, 40,0 N/mm e 51,2 N/mm, respectivamente. Os testes com os pinos de Schanz de 5,5 mm com alma de 4,5 mm mostraram resistência média de: 15,2 N/mm, 33,5 N/mm, 53,0 N/mm e 70,0 N/mm. Estudo estatístico com o teste da Análise de Variância e o teste de Bonferroni mostraram ausência de diferença estatisticamente significante entre os grupos com pinos com diâmetro da alma da parte roscada de 3,2mm (de 4,5 mm e 5,5 mm). Houve diferença estatisticamente significante (alfa <0,05) entre o grupo com pinos de 5,5 mm com alma 4,5 mm e os outros dois. CONCLUSÕES: 1- Não houve diferença estatisticamente significante entre as montagens de fixador externo linear com pinos de Schanz de 4,5 mm e 5,5 mm com alma de 3,2 mm, aos esforços de torção. 2- A montagem do fixador externo linear com pinos de Schanz de 5,5 mm com alma de 4,5 mm mostrou resistência mecânica maior à torção, estatisticamente significante, em relação aos outros dois grupos.

OBJECTIVE: The objective of this study was to evaluate the mechanical force of three different assemblies of a linear external fixator using 4.5 mm and 5.5 mm Schanz screws with a 3.2 mm-diameter root, and another screw with 5.5 mm diameter with a 4,5mm root. MATERIAL AND METHODS: The linear external fixator was assembled in a 500 mm-long polypropylene tube, with a 45-degree oblique angle cut in the center of the cylinder, with two Schanz screws in each segment. Eighteen assemblies were studied, divided into three groups of six pieces each. In the group 1, 4.5mm-diameter Schanz screws were used, in the group 2, 5.5mm-diameter Schanz screws, both with 3,2mm root were used. In the group 3, 5.5mm-diameter Schanz screws with a diameter root of 4.5mm were used. The mechanical tests were performed in a MT-100 torsion machine, and the resistance measurements were performed at 4.5º, 9.0º, 13.5º, and 18º of torsion. RESULTS: The 4.5mm Schanz screws with 3,2 mm root showed an average torsion resistance at 4.5o, 9.0 o, 13.5 o and 18.0 o, respectively of: 12.0 N/mm, 21.0 N/mm, 33.0 N/mm, and 46.0 N/mm. The 5.5mm Schanz screw with 3.2 mm root, showed as average resistance: 13.2 N/mm, 25.3 N/mm, 40.0 N/mm, and 51.2 N/mm, respectively. The tests with 5.5 mm Schanz screws with 4.5 mm root showed an average resistance of: 15.2 N/mm, 33.5 N/mm, 53.0 N/mm, and 70.0 N/mm. Statistical analysis with the Variance Analysis test and the Bonferroni's test showed the absence of statistically significant differences among groups with root diameter of 3.2mm (4.5 mm and 5.5 mm). There was a statistically significant difference between the group with the 5.5mm Schanz screws with 4.5 mm root and the other two groups. CONCLUSIONS: 1- There was no statistically significant difference among assemblies of linear external fixator using 4.5mm and 5.5mm Schanz screws with 3.2mm root. 2- The linear external fixator with 5.5mm Schanz screws with 4.5mm root, showed a stronger mechanical resistance to the torsion, statistically significant, regarding the other two groups.