Creep behaviors of ASTM A36 welded joints

This research work aimed to observe the creep behaviors of the ASTM A36 welded joints. The microstructure and hardness of the base zone (BZ), heat affected zone (HAZ), and weld fusion zone (WFZ) were measured. Afterward, the residual stresses on the welded plate were observed to determine any lead to fatigue failure. The hot tensile tests were then performed to investigate the welded specimens' creep behaviors at varied strain rates and temperatures. The power-law model was applied to describe the creep behaviors at each testing condition. Finally, the scanning electron microscopic (SEM) images of the tested specimens were observed to identify breakage causes. The creep results showed that the weakest locations were found in the base (A36) zones. The areas prone to ductile fracture was the base zones close to HAZ

Closed-loop control of product properties in metal forming

Metal forming processes operate in conditions of uncertainty due to parameter variation and imperfect understanding. This uncertainty leads to a degradation of product properties from customer specifications, which can be reduced by the use of closed-loop control. A framework of analysis is presented for understanding closed-loop control in metal forming, allowing an assessment of current and future developments in actuators, sensors and models. This leads to a survey of current and emerging applications across a broad spectrum of metal forming processes, and a discussion of likely developments.Engineering and Physical Sciences Research Council (Grant ID: EP/K018108/1)This is the final version of the article. It first appeared from Elsevier via https://doi.org/10.1016/j.cirp.2016.06.00

Effects of Tool Coatings on Energy Consumption in Micro-Extrusion of Aluminum Alloy 6063

The tool wear rate and energy consumption were typically unknown in micro-extrusion, which made it difficult to optimize the tool design for both the final part quality and production cost. This study investigated the effects of tool coatings on energy consumption in the micro-extrusion of aluminum alloy 6063. Three main factors were considered in this study: (1) tool coating types, (2) bearing length, and (3) extrusion ratio. The micro-extrusion finite element simulation model was developed and validated with the micro-extrusion experiment. The results showed that increasing bearing lengths led to the increase in tool wear rate and energy consumption for all the coating types. The decreasing coefficient of friction values of the tool-billet interface led to a decrease in energy consumption. High hardness values of the tool surface and low bearing lengths helped increase tool life. Low values of coefficient of friction and bearing lengths helped decrease energy consumption

Formability Effects of Variable Blank Holder Force on Deep Drawing of Stainless Steel

This paper investigates the formability effects of variable blank holder force on deep drawing of AISI 304 rectangular cup. Various sets of blank holder forces were set to observe the formability, which was indicated by the percentage of sheet thinning in this study. The results showed that the blank holder forces at the locations of the sheet edges surrounding the cavity areas were considered dominant to reduce sheet thinning and enhance the formability

Formability Effects of Variable Blank Holder Force on Deep Drawing of Stainless Steel

This paper investigates the formability effects of variable blank holder force on deep drawing of AISI 304 rectangular cup. Various sets of blank holder forces were set to observe the formability, which was indicated by the percentage of sheet thinning in this study. The results showed that the blank holder forces at the locations of the sheet edges surrounding the cavity areas were considered dominant to reduce sheet thinning and enhance the formability

Tribology in metal forming at elevated temperatures

International audienceThe tribo-characteristics of metal forming at high temperatures have not yet been well understood due to the complex nature of thermal, microstructural, interaction, and process parameters. This is a review paper on the effects of temperature, coating, and lubrication to the tribological characteristics in hot forming as well as the tribometers for different metal forming processes at elevated temperatures mainly based on the experimental work. The tribological behaviors of oxides in hot forming, such as rolling and stamping, were reviewed and presented. Some commonly used surface coatings and lubricants in hot forming were given. Many types of tribometer were selected and presented and some of them provided a great potential to characterize friction and wear at elevated temperatures. Nevertheless, more testing conditions should be further investigated by developing new tribometers. Eventually, experimental results obtained from reliable tribometers could be used in theory and model developments for different forming processes and materials at high temperatures. The review also showed the great potential in further investigations and innovation in tribology

Finite Element Analysis of Grain Size Effects on Curvature in Micro-Extrusion

The precision and accuracy of the final geometry in micro-parts is crucial, particularly for high-value-added metallic products. Micro-extrusion is one of the most promising processes for delivering high-precision micro-parts. The curving tendency observed in micro-extrusion parts is a major concern, significantly affecting the final part geometry. The purpose of this paper was to investigate the driving mechanism behind the curvature in micro-extrusion at room temperature. A finite element (FE) simulation was carried out to observe the influential primary factors: (1) grain size, (2) grain boundary, (3) grain orientation, and (4) bearing length of a 6063 aluminum alloy. The Extrusion Curvature Index (ECI) was also established to indicate the level of curvature in micro-extruded parts. The results showed that the grain boundary at the high strain and die opening area was the dominant factor for single-grain conditions. The interactive effects of the grain boundary and grain orientation also affected the curvature under single-grain conditions. If the number of grains across the specimen increased up to 2.7 (poly-grains), the curvature effect was dramatically reduced (the pins were straightened). For all conditions, the curvature in micro-extrusion could be eliminated by extending the bearing length up to the exit diameter length

Mechanical Investigations of ASTM A36 Welded Steels with Stainless Steel Cladding

The in-service life of ASTM A36 welded steel pipes in power plants is often shortened by ash corrosion. During the heating condition, the ash deposition on the welded steel pipes gradually reduces the thickness of the pipes, thus, reducing the lifetime. Instead of replacing the pipes with new ones, the cost could be significantly reduced if the lifetime could be further extended. Weld cladding was the method selected in this study to temporarily extend the service life of welded pipes. This paper performed the mechanical investigations of A36—A36 welded steel plates after coating the surfaces with 309L stainless steel with a cladding method. The residual stress was also tested to observe the internal stresses developed during the welding processes of A36—A36 specimens. The comparison between the coated and non-coated surfaces of welded steels was performed by using the tensile tests (at room and elevated temperatures), corrosion (pitting corrosion, intergranular corrosion, and weight-loss corrosion) tests, and wear (shot blasting) tests. The life-extension of both coatings was evaluated based on the tensile tests and the corrosion and wear tests provided the qualitative evaluations of the coating performance. The results showed that surfaces coated by cladding could be used to temporarily extend the life of ASTM A36 welded steel under the studied conditions