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Electrical, microstructural, and mechanical behavior of HSLA X70 pipeline welded by GMAW and FCAW processes

Abstract

This study proposed the dynamic modeling and control strategy for GMAW and FCAW processes using two parallel-connected inverters in the power supply to weld an HSLA X70 steel pipeline using short-circuiting and spray transfer modes. The obtained results showed a great similarity between the welding current and voltage of the simulation model and the experimental process. A novel technique, the single-sided enveloped spectrum (SSES), proved highly efficient in estimating droplet detachment frequency (DDF). Mesh area calculations confirmed the high arc stability due to optimized welding parameters. The microstructure of a GMAW pass consisted primarily of coarse acicular ferrite, Widmanst & auml;tten ferrite, and polygonal ferrite, with minor traces of bainite. In contrast, the FCAW passes exhibited a wider variety of ferrite morphologies. Grain boundary ferrite (GBF) morphology was prevalent, while the capping passes showed a distinct feature: very fine grains of bainite and acicular ferrite. Vickers micro-hardness measurements revealed a significant reduction in hardness within the Heat Affected Zone and Weld Zone of the GMAW process, down to approximately 180 +/- 5 HV. Conversely, the capping pass exhibited the highest micro-hardness, reaching around 230 HV. This increase is attributed to the presence of a fine, columnar microstructure composed of Widmanst & auml;tten and polygonal ferrite.

article Article

date_range 2024

language English

link Link of the paper

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Benaouda Omar

Kellai Ahmed

Elbar Mohamed

Benlamnouar Mohamed

Benmessaoud Tahar

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Featured Keywords

GMAW

FCAW

Short-circuiting

Spray

HSLA X70 pipeline

SSES

DDF

Arc stability

Microstructure

Micro-hardness

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Assessment of reinforced concrete building damages following the Kahramanmaraş earthquakes in Malatya, Turkey (February 6, 2023)

Abstract

Earthquakes of magnitude Mw = 7.7 and Mw = 7.6 hit the city of Kahramanmaraş (Turkey) on 6 February 2023. These earthquakes caused serious damage in 11 provinces in Turkey resulting in over 50,000 deaths and huge economic losses with the collapse of thousands of buildings. Two consecutive devastating earthquakes have severely damaged the reinforced concrete building stock located in Malatya. There are many reasons reinforced concrete structures suffer damage under the influence of seismic loads. These reasons can be listed as material and section properties that do not comply with earthquake codes, workmanship defects, ground parameters that are not considered and design errors, as seen in field investigations after earthquakes in Turkey in the past. In this research, a field study was conducted on reinforced concrete buildings damaged after the earthquakes in Malatya province. The causes of structural damages in reinforced concrete buildings between 6–26 years of age were assessed in terms of design and material defects. The structural damages were mainly caused due to insufficient stirrups in structural members, short column, strong beam–weak column, failures of infill walls, soft story type collapse, poor concrete quality, and reinforcement corrosion. In addition to the field investigation, the spectrum relationships created using raw acceleration data obtained from DEMP (Disaster and Emergency Management Presidency) stations in Malatya province were compared with the design response spectra.

article Article

date_range 2024

language English

link Link of the paper

Collapsed buildings

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