Repair Welding Effects on the Bending Fatigue Strength of AISI 4130 Aeronautical Steel used in a Critical to the Flight-Safety Structure

The aim of this study was to analyze the effect of successive TIG (tungsten inert gas) welding repairs on the reverse bending fatigue strength of AISI 4130 steel, which is widely used in components critical to the flight-safety. In order to simulate the abrupt maneuvers, wind bursts, motor vibration and helixes efforts, which generate cyclic bending loadings at the welded joints of a specific aircraft component called motor cradle, experimental reverse bending fatigue tests were carried out on specimens made from hot-rolled steel plate, 1.10 mm (0.043 in) thick, by mean of a SCHENK PWS equipment, with load ratio R = -1, under constant amplitude, at 30 Hz frequency and room temperature. It was observed that the bending fatigue strength decreases after the TIG (Tungsten Inert Gas) welding process application on AISI 4130 steel, with subsequent decrease due to re-welding sequence as well. Microstructural analyses and microhardness measurements on the base material, heat-affected zone (HAZ) and weld metal, as well as the effects of the weld bead geometry on the obtained results, have complemented this study.

Caracterização microestrutural do metal de solda depositado por arco submerso em chapas de aço-carbono estrutural

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência da potência de laser Nd: YAG na soldagem do aço inoxidável duplex UNS S32205

Pós-graduação em Engenharia Mecânica - FEIS

Effects of several TIG weld repairs on the axial fatigue strength of AISI 4130 aeronautical steel-welded joints

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fatigue strength of tungsten inert gas-repaired weld joints in airplane critical structures

In this work the effect of Gas Tungsten Arc Welding (GTAW) repairs on the axial fatigue strength of an AISI 4130 steel welded joint used in airframe critical to the flight-safety was investigated. Fatigue tests were performed at room temperature on 0.89 mm thick hot-rolled plates with constant amplitude and load ratio of R = 0.1, at 20 Hz frequency. Monotonic tensile tests, optical metallography and microhardness, residual stress and weld geometric factors measurements were also performed. The fatigue strength decreased with the number of GTAW repairs, and was related to microstructural and microhardness changes, as well as residual stress field and weld profile geometry factors, which gave origin to high stress concentration at the weld toe. (C) 2011 Elsevier B.V. All rights reserved.

Influência do tipo de chanfro, tecimento e sentido de laminação na distorção angular em soldagem GMAW-P robotizada de alumínio

The industry's interest in having a greater control of the deformations caused by welding is due to the geometric and dimensional tolerances been more and more precise in the project specifications, motivating the manufacturing engineering to develop stable processes and to ensure routine production. Aiming at it, the main goal of this present work is to analyze how much routine situations used in automatic aluminum welding can influence on the angular deformations of this material. Using the alloy AA 5052 H34, and the automatic welding in pulsed GMAW process, three types of weaving were applied throughout the length of the weld, in butt joints assembled without groove and with 60 degrees single-V-groove, arranged transversely as well as longitudinally to the rolling direction of the plate. The measurement of the deformations was made by a three-dimensional equipment, before and after the welding, in three distinct regions in the specimens. The profile of the weld bead was the main factor for the different types of deformations found, as revealed by macrographical analysis. The 60 degrees single-V-groove had higher amplitudes of deformations as the joint without groove. The torch oscillation wasn't a variable of statistically significant influence on this amplitudes.

Estudo Comparativo de Juntas Soldadas a TIG e Laser Empregando-se Ti com Pureza Comercial Utilizado em Prótese sobre Implantes

Welding in the dentistry has been used for great part of the specialized dentist-surgeons in the implants area to solve prosthesis supported by implant adaptation problems. The development of new equipments Laser and TIG allowed a larger use of these processes in the prosthesis production. In this work, it was studied welded joints made by Laser and TIG, using commercial purity titanium, cpTi, applied in prosthesis supported by implants. The weld characterizations were carried out by light microscopy, EDS_elementary mapping, microhardness and tensile test. Through metallographic characterization, the weld bead presented a martensitic microstructure in the Laser welding process, originated from shear provoked by deformations in the lattice. This caused structural changes of the transformed area, which determines a fine plate-like morphology. In the weld bead from TIG, besides presenting higher hardness, was observed formation of Widmansttaten structure, which is characteristic of a geometric model, resulted of new phase formation along of the crystallographic plans. The martensitic structure is more refined than Widmansttaten structure, due to the high-speed cooling (10(3)degrees C/s) imposed by the Laser process.

Investigation of the metal/porcelain interface in LASER-welded Ni-Cr-Mo alloy

The interface formed between the metal and the porcelain of laser-welded Ni-Cr-Mo alloy was studied on a metallurgical basis. The characterization was carried out by using optical microscope, electron scan microscopy and X-ray dispersive spectroscopy techniques and mechanical three-point flexion tests, in the laser-welded region, with and without porcelain. The union of the porcelain with the alloy is possible only after the oxidation of the metallic surface and the subsequent application of a bonding agent known as opaque. The porcelain applied to the base metal and weld bead showed different behaviours - after the flexion test, the base metal showed cracks, while that in the weld bead broke away completely. It was noted that the region subjected to laser welding had lower adherence to the porcelain than the base metal region, due to microstructural refinement of the weld bead. These results can be shown by the X-ray dispersive spectroscopy carried out on the regions studied. The flexion tests demonstrated that the Ni-Cr-Mo alloy subject to laser welding had significant alterations in its mechanical properties after application of the porcelain.

Soldagem GMAW-P robotizada de alumínio: influência do tipo de chanfro, tecimento e sentido de laminação na distorção

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Soldagem TIG-AC onda retangular: efeitos da velocidade de soldagem sobre as propriedades mecânicas da Liga AA 6063-T6

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de uma EPS especificação de procedimento de soldagem para união de chapas de aço ASTM A131 com processo FCAW

In any welding process is of utmost importance by welders and responsible qualities of the area understand the process and the variables involved in it, in order to have maximum efficiency in welding both in terms of quality as the final cost , never forgetting, of course, the process conditions which the welder or welding operator shall be submitted. Therefore, we sought to understand the variables relevant to the welding process and develop an EPS (Welding Procedure Specification) as ASME IX for cored wire welding process (FCAW Specification AWS) with shielding gas and automated process for base material ASTM a 131, with 5/16 thick, using a single pass weld, for conditions with pre-and post-heating and the destructive testing for verification and analysis of the resulting weld bead

Caracterização microestrutural de uma estrutura tubular aeronáutica submetida a sucessivos reparos de solda TIG

This work examines the possible effects of successive repair procedures on the microstructure of welded steel SAE 4130 by TIG welding process. Discussions and results were made about the metallographic analysis , non-metallic inclusions and microhardness tests , which were conducted on samples taken from the cradle engine component after the end of its life , a model airplane T-27 Tucano , made by EMBRAER and belonging were performed FAB . The choice of such component is due to the fact that this is critical to flight safety since it provides support for the aircraft engine . Thus regions of the weld metal , base metal and heat affected , with samples of the original weld bead , free of weld bead and also with four rework procedures for TIG welding zone were analyzed . It was found that after the fourth rework there is an increase in the amount of martensite , which may weaken the material with respect to resistance to fatigue. It was also found that the regions of the heat affected zone and weld metal have higher microhardness values when compared to those found in the base metal due to favoring the formation of ferritic and tempered martensite microstructures . Moreover, a welding process promotes a region with less non-metallic inclusions than metal base , which also explains the difference in the results obtained

Análise metalográfica do titânio puro submetido à soldagem laser Nd: YAG e TIG

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influência do desbalanceamento da onda retangular na liga de alumínio 6063-T6 soldada pelo processo TIG-CA

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Investigation of Plasma Immersion Ion Implantation Process in Magnetic Mirror Geometry

Plasma immersion ion implantation (PIII) with low external magnetic field has been investigated both numerically and experimentally. The static magnetic field considered is essentially nonuniform and is generated by two magnetic coils installed outside the vacuum chamber. Experiments have been conducted to investigate the effect of two of the most important PIII parameters: target voltage and gas pressure. In that context, it was found that the current density increased when the external parameters were varied. Later, the PIII process was analyzed numerically using the 2.5-D computer code KARAT. The numerical results show that the system of crossed E x B fields enhances the PIII process. The simulation showed an increase of the plasma density around the target under the operating and design conditions considered. Consequently, an increase of the ion current density on the target was observed. All these results are explained through the mechanism of gas ionization by collisions with electrons drifting in crossed E x B fields.