Rumman Ul Ahsan | International University Of Business Agriculture and Technology(IUBAT) (original) (raw)

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Papers by Rumman Ul Ahsan

Research paper thumbnail of Fabrication of bimetallic additively manufactured structure (BAMS) of low carbon steel and 316L austenitic stainless steel with wire + arc additive manufacturing

Rapid Prototyping Journal, 2019

Purpose Wire + arc additive manufacturing (WAAM) uses existing welding technology to make a part ... more Purpose Wire + arc additive manufacturing (WAAM) uses existing welding technology to make a part from metal deposited in an almost net shape. WAAM is flexible in that it can use multiple materials successively or simultaneously during the manufacturing of a single component. Design/methodology/approach In this work, a gas metal arc welding (GMAW) based wire + arc additive manufacturing (WAAM) system has been developed to use two material successively and fabricate bimetallic additively manufactured structure (BAMS) of low carbon steel and AISI 316L stainless steel (SS). Findings The interface shows two distinctive zones of LCS and SS deposits without any weld defects. The hardness profile shows a sudden increase of hardness at the interface, which is attributed to the migration of chromium from the SS. The tensile test results show that the bimetallic specimens failed at the LCS side, as LCS has lower strength of the materials used. Originality/value The microstructural features and...

Research paper thumbnail of Role of coatings in the formation of defects in advanced high strength steel welds

Materials Today: Proceedings, 2020

Abstract Infrared thermography technique (IRT) uses longer wavelength electromagnetic radiations ... more Abstract Infrared thermography technique (IRT) uses longer wavelength electromagnetic radiations emitted by a hot body to compute its temperature. The radiant energy absorbed by the thermographic system is transformed into electronic signals by sensors and into visible signals known as a thermogram. Besides highly sophisticated military applications, the non-contact infrared thermography is extensively used in medical, electrical, mechanical and many other domains. This paper exploits the infrared thermography technique for precise measurement of temperature across the weld interfaces obtained with two different welding processes, viz. nut projection welding and cold metal transfer gas metal arc welding (CMT-GMAW). The recorded temperature was processed to obtain peak temperature, heat generated, heat affected zones, and to understand the effect of coating on the heat generation and defect formation. IRT results reveal that the weld quality and strength is significantly influenced by the weld pool temperature and region of heat generation in CMT and nut projection welding, respectively.

Research paper thumbnail of Porosity formation mechanisms in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steels

Science and Technology of Welding and Joining, 2016

ABSTRACT

Research paper thumbnail of Determination of effect of elliptic notches and grooves on stress concentration factors on notched bar in tension and grooved shaft under torsion

Journal of Naval Architecture and Marine Engineering, 2013

Research paper thumbnail of The effect of alloying elements of gas metal arc welding (GMAW) wire on weld pool flow and slag formation location in cold metal transfer (CMT

The surface tension driven flow or Marangoni flow in welding plays an important role in governing... more The surface tension driven flow or Marangoni flow in welding plays an important role in governing weld bead shape hence affecting the weld joint quality. The surface tension of molten metal usually has a negative temperature coefficient causing the weld pool to flow from the center towards the toe. This temperature coefficient of the surface tension can be altered to be a positive one in the presence of surface-active elements like sulfur (S), oxygen (O), selenium (Se) and tellurium (Te). The amount of deoxidizing elements present in the consumables governs the amount of oxygen present in the weld metal. The presence of a lower amount of deoxidizers results in higher concentration of oxygen in the weld metal. The presence of adequate amount of oxygen can result in a positive temperature coefficient of surface tension gradient in the weld pool. In such situation, the weld pool flows from the toe towards the direction of the center. As a result, of pyrometallurgical reactions in the arc and the weld pool various oxides of the alloying elements are former which are referred as slag. The slags float on the weld pool surface and accumulate following the weld pool flow pattern. As a result, slags form either along the center of the weld bead or the toe depending on the weld pool flow pattern. The slags need to be removed as they degrade the weld bead appearance and paint adhesiveness. Due to easy detachability, slag formation near the center of the weld bead is desired. From in-situ high-speed videography of weld pool, weld metal chemical composition analysis, the effect of consumables alloying elements on weld pool flow pattern and slag formation location are disclosed, which can facilitate the selection of the welding consumables for better productivity in CMT-GMAW.

Research paper thumbnail of Cold Metal Transfer (CMT) GMAW of Zinc-Coated Steel

This paper investigates the feasibility of cold metal transfer (CMT) GMA welding of zinc-coated s... more This paper investigates the feasibility of cold metal transfer (CMT) GMA welding of zinc-coated steel in a gap-free lap joint configuration over a wide range of heat input from 150 to 550 J/mm in terms of porosity formation and mechanical performance. The quantitative analysis of porosity by X-ray radiographic testing shows that the heat input conditions below 250 J/mm and above 350 J/mm cause least amount of porosity. The temperature dependent properties of the weld pool viscosity and vapor pressure of zinc determine the porosity formation, growth and escape mechanisms at different heat inputs. These factors are characterized by using high speed imaging analysis and infrared (IR) thermography of the weld pool. Secondly, to ensure joint integrity, samples welded at different heat input conditions are mechanically tested to identify theminimum required penetration depth leading to base metal failure. It was found that, a minimum heat input of 200 J/mm is required for ensuring that minimum penetration. Finally, the heat input criteria achieved from the porosity analysis and mechanical testing are combined and two sets of optimized welding conditions, one set is in the low heat inputs ranging from 200 to 250 J/mm and another set in the high heat inputs ranging from 350 to 550 J/mm, are derived. The guideline proposed by this work can be used for selecting suitable welding conditions based on requirement, which can ensure low porosity in the weldments and adequate mechanical strength of the joints.

Research paper thumbnail of Porosity formation mechanisms in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steels

The porosity formation in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated s... more The porosity formation in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steel is studied over a wide range of the heat inputs (160–250 J /mm), which shows low porosity in weld bead (2% of bead area) in low (250 J /mm) and high (350 J/mm) heat inputs and maximum at medium (250–350 J/mm) heat inputs. The high speed imaging of weld pool shows that the highest frequency of zinc vapour escapes at high heat inputs compared to other conditions. Numerous experiments show that size and location of pores along with escaping of zinc vapour are the results of competition of viscosity of weld pool against buoyancy and vapour pressure within the time required to reach solidification temperature. Based on this concept, mechanisms involved in porosity formation, growth and escape phenomena are disclosed, which can help select the optimised welding conditions to obtain porosity free welds in CMT-GMAW of zinc coated steels.

Research paper thumbnail of DETERMINATION OF EFFECT OF ELLIPTIC NOTCHES AND GROOVES ON STRESS CONCENTRATION FACTORS ON NOTCHED BAR IN TENSION AND GROOVED SHAFT UNDER TORSION

Research paper thumbnail of Fabrication of bimetallic additively manufactured structure (BAMS) of low carbon steel and 316L austenitic stainless steel with wire + arc additive manufacturing

Rapid Prototyping Journal, 2019

Purpose Wire + arc additive manufacturing (WAAM) uses existing welding technology to make a part ... more Purpose Wire + arc additive manufacturing (WAAM) uses existing welding technology to make a part from metal deposited in an almost net shape. WAAM is flexible in that it can use multiple materials successively or simultaneously during the manufacturing of a single component. Design/methodology/approach In this work, a gas metal arc welding (GMAW) based wire + arc additive manufacturing (WAAM) system has been developed to use two material successively and fabricate bimetallic additively manufactured structure (BAMS) of low carbon steel and AISI 316L stainless steel (SS). Findings The interface shows two distinctive zones of LCS and SS deposits without any weld defects. The hardness profile shows a sudden increase of hardness at the interface, which is attributed to the migration of chromium from the SS. The tensile test results show that the bimetallic specimens failed at the LCS side, as LCS has lower strength of the materials used. Originality/value The microstructural features and...

Research paper thumbnail of Role of coatings in the formation of defects in advanced high strength steel welds

Materials Today: Proceedings, 2020

Abstract Infrared thermography technique (IRT) uses longer wavelength electromagnetic radiations ... more Abstract Infrared thermography technique (IRT) uses longer wavelength electromagnetic radiations emitted by a hot body to compute its temperature. The radiant energy absorbed by the thermographic system is transformed into electronic signals by sensors and into visible signals known as a thermogram. Besides highly sophisticated military applications, the non-contact infrared thermography is extensively used in medical, electrical, mechanical and many other domains. This paper exploits the infrared thermography technique for precise measurement of temperature across the weld interfaces obtained with two different welding processes, viz. nut projection welding and cold metal transfer gas metal arc welding (CMT-GMAW). The recorded temperature was processed to obtain peak temperature, heat generated, heat affected zones, and to understand the effect of coating on the heat generation and defect formation. IRT results reveal that the weld quality and strength is significantly influenced by the weld pool temperature and region of heat generation in CMT and nut projection welding, respectively.

Research paper thumbnail of Porosity formation mechanisms in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steels

Science and Technology of Welding and Joining, 2016

ABSTRACT

Research paper thumbnail of Determination of effect of elliptic notches and grooves on stress concentration factors on notched bar in tension and grooved shaft under torsion

Journal of Naval Architecture and Marine Engineering, 2013

Research paper thumbnail of The effect of alloying elements of gas metal arc welding (GMAW) wire on weld pool flow and slag formation location in cold metal transfer (CMT

The surface tension driven flow or Marangoni flow in welding plays an important role in governing... more The surface tension driven flow or Marangoni flow in welding plays an important role in governing weld bead shape hence affecting the weld joint quality. The surface tension of molten metal usually has a negative temperature coefficient causing the weld pool to flow from the center towards the toe. This temperature coefficient of the surface tension can be altered to be a positive one in the presence of surface-active elements like sulfur (S), oxygen (O), selenium (Se) and tellurium (Te). The amount of deoxidizing elements present in the consumables governs the amount of oxygen present in the weld metal. The presence of a lower amount of deoxidizers results in higher concentration of oxygen in the weld metal. The presence of adequate amount of oxygen can result in a positive temperature coefficient of surface tension gradient in the weld pool. In such situation, the weld pool flows from the toe towards the direction of the center. As a result, of pyrometallurgical reactions in the arc and the weld pool various oxides of the alloying elements are former which are referred as slag. The slags float on the weld pool surface and accumulate following the weld pool flow pattern. As a result, slags form either along the center of the weld bead or the toe depending on the weld pool flow pattern. The slags need to be removed as they degrade the weld bead appearance and paint adhesiveness. Due to easy detachability, slag formation near the center of the weld bead is desired. From in-situ high-speed videography of weld pool, weld metal chemical composition analysis, the effect of consumables alloying elements on weld pool flow pattern and slag formation location are disclosed, which can facilitate the selection of the welding consumables for better productivity in CMT-GMAW.

Research paper thumbnail of Cold Metal Transfer (CMT) GMAW of Zinc-Coated Steel

This paper investigates the feasibility of cold metal transfer (CMT) GMA welding of zinc-coated s... more This paper investigates the feasibility of cold metal transfer (CMT) GMA welding of zinc-coated steel in a gap-free lap joint configuration over a wide range of heat input from 150 to 550 J/mm in terms of porosity formation and mechanical performance. The quantitative analysis of porosity by X-ray radiographic testing shows that the heat input conditions below 250 J/mm and above 350 J/mm cause least amount of porosity. The temperature dependent properties of the weld pool viscosity and vapor pressure of zinc determine the porosity formation, growth and escape mechanisms at different heat inputs. These factors are characterized by using high speed imaging analysis and infrared (IR) thermography of the weld pool. Secondly, to ensure joint integrity, samples welded at different heat input conditions are mechanically tested to identify theminimum required penetration depth leading to base metal failure. It was found that, a minimum heat input of 200 J/mm is required for ensuring that minimum penetration. Finally, the heat input criteria achieved from the porosity analysis and mechanical testing are combined and two sets of optimized welding conditions, one set is in the low heat inputs ranging from 200 to 250 J/mm and another set in the high heat inputs ranging from 350 to 550 J/mm, are derived. The guideline proposed by this work can be used for selecting suitable welding conditions based on requirement, which can ensure low porosity in the weldments and adequate mechanical strength of the joints.

Research paper thumbnail of Porosity formation mechanisms in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steels

The porosity formation in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated s... more The porosity formation in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steel is studied over a wide range of the heat inputs (160–250 J /mm), which shows low porosity in weld bead (2% of bead area) in low (250 J /mm) and high (350 J/mm) heat inputs and maximum at medium (250–350 J/mm) heat inputs. The high speed imaging of weld pool shows that the highest frequency of zinc vapour escapes at high heat inputs compared to other conditions. Numerous experiments show that size and location of pores along with escaping of zinc vapour are the results of competition of viscosity of weld pool against buoyancy and vapour pressure within the time required to reach solidification temperature. Based on this concept, mechanisms involved in porosity formation, growth and escape phenomena are disclosed, which can help select the optimised welding conditions to obtain porosity free welds in CMT-GMAW of zinc coated steels.

Research paper thumbnail of DETERMINATION OF EFFECT OF ELLIPTIC NOTCHES AND GROOVES ON STRESS CONCENTRATION FACTORS ON NOTCHED BAR IN TENSION AND GROOVED SHAFT UNDER TORSION