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Residual Stress Heterogeneity Induced By Powder Metallurgy Gear Manufacturing Chains

Abstract

Powder metallurgy represents an alternative to increase sustainability in the manufacturing of automotive gears, but its potential is hindered by a certain lack of knowledge on surface integrity properties that can impair the gear performance. This study explores the effects of the microstructural differences induced by this chain on the residual stress heterogeneity state of gears. X-ray diffraction methods of macro residual stress mapping and line profile analysis were applied for measurements of gear teeth after subsequent steps of the powder metallurgy and the conventional wrought steel chains. The powder metallurgy chain induced more pronounced heterogeneities than the conventional manufacturing, characterized by non-uniform residual stress distributions along the lead and the involute profiles of gear flanks. These non-uniformities observed after carburizing were traced back to the previous steps, surface densification, sintering and compaction. The residual stress distribution patterns of these steps were compatible with the plasticity dynamics of each manufacturing process. Such surface integrity heterogeneities result in a residual stress gradient along the gears functional surface, exposing particular regions to be more susceptible to fatigue effects.

article Article

date_range 2022

language English

link Link of the paper

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Robatto Lucas

Rego Ronnie

Righetti Victor

Thim Gilmar

Borille Anderson

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Featured Keywords

Powder metallurgy

Gears

Residual stresses

Heterogeneity

Evolution

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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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