Abdelbaset Midawi - Academia.edu (original) (raw)
Papers by Abdelbaset Midawi
Metals
Third-generation advanced high-strength steels (3G-AHSS) are typically galvanized to prevent corr... more Third-generation advanced high-strength steels (3G-AHSS) are typically galvanized to prevent corrosion of the outer body structure. However, the zinc coating on the surface, combined with the locally elevated temperatures generated during the resistance spot welding (RSW) process, can provide the prerequisites for liquid metal embrittlement (LME). This work uses two strategies to control LME crack formation: current pulsation and varying the electrode geometry. These two methods were compared to a baseline welding schedule for a 3G-980-GI coated AHSS. The effectiveness of each method was discussed in terms of the overall weld cracking index and local cracking index. The results showed that increasing the current pulses results in a slower energy input into the weld, which can help to reduce LME crack formation. Introducing more pulses (five to seven pulses) reduced LME crack formation while maintaining the same welding time. Regarding the electrode geometry, the results showed an in...
International Journal of Mechanical Sciences
International Journal of Pressure Vessels and Piping, 2018
Strain-based design (SBD) of pipelines allows stress owing to displacementcontrolled loads origin... more Strain-based design (SBD) of pipelines allows stress owing to displacementcontrolled loads originating from landslides, seismic motions, or frost heaves, to exceed yield stress. In such cases, the distribution of the strain over a large area (pipe) rather than local area (weld) is preferred. Accordingly, in SBD, yield strength of the circumferential girth weld is over matched when compared to the base metal. In this work, API-X80 pipeline steel sections were joined together using the robotic Gas-Metal Arc Welding (GMAW) process; filler metals and shielding gases were varied to achieve three different levels of strength (even, over and under match) between the weld and base metal. Weld metal and HAZ cross-section microstructures were investigated and correlated with micro-hardness maps to ensure that different mismatch levels were achieved. Yield strengths of the welds in the hoop direction were measured using both instrumented indentation and conventional tensile testing. The instrumented indentation technique used a 100-µm diameter nearly-flat indenter to estimate yield strengths for the welds and heat-affected zones from the load-displacement response for each zone. The measured yield strengths were compared with 0.2% offset tensile yield strength obtained through conventional tensile testing of allweld and base metal specimens. Strength measurements, in the hoop direction, for weld metal from both of the techniques agreed to within 4.6%. The results showed that the nearly-flat tip indentation method can be used as a tool to directly estimate strength mismatch of pipeline girth welds. Measurements of yield strength for narrow coarse and fine grained heat-affected zones, which cannot be measured through any other method, can also be assessed using the techniques described herein.
Journal of Manufacturing Processes
Journal of Manufacturing Science and Engineering
To accurately model the resistance spot welding (RSW) joint in finite element analysis (FEA), the... more To accurately model the resistance spot welding (RSW) joint in finite element analysis (FEA), the constitutive behavior of materials in various weld regions such as heat-affected zone (HAZ) should be measured. Due to the sharp temperature gradient through RSW specimens, microstructural and corresponding mechanical properties of weld regions are different. Additionally, the size of RSW is small; hence, it is challenging to directly measure the stress–strain curve of materials. In this regard, hardness-scaling and ball-indentation techniques are among the popular methods to in-directly measure the stress–strain curve of these materials. However, the effectiveness of these two techniques on predicting the stress/strain distribution and failure behavior of resistance spot welded advanced high strength steels (AHSS) is not clear. In the present work, the stress–strain curves obtained through hardness-scaling and ball-indentation techniques have been compared. The stress/strain distributi...
Materials & Design, 2022
Welding Journal, 2021
Advanced high-strength steels (AHSS) such as complexphase (CP) and high-formability (HF) steel of... more Advanced high-strength steels (AHSS) such as complexphase (CP) and high-formability (HF) steel offer weightsaving advantages for automotive applications such as chassis and frame applications. To prevent material oxidation, materials are often galvanized to protect the substrate from corrosion. However, the weldability of coated AHSS becomes challenging due to the trapping of zinc in the weld molten pool, which could lead to weld defects such as porosity and liquid metal embrittlement cracks. This work focused on the weldability of AHSS (CP800 and 980HF) using the gas metal arc welding process. The roles of both galvanized iron coating and filler material on weld strength were investigated. The welds were performed using two different filler materials: a low-strength filler (ER70S-6) and a high-strength filler (ER100S-6) material. In addition, two different joint configurations were studied: lap joints and butt joints. The results showed that the butt joint had a higher strength com...
This study aims to develop a new method to characterize mechanical properties using instrumented ... more This study aims to develop a new method to characterize mechanical properties using instrumented indentation. The indentation results were correlated with observed microstructure in weld metal of gas metal arc welding (GMAW) pipeline joints with their mechanical properties such as: hardness and yield strength. The focus of this work was on a representative API-X80 grade weldment using different commercial welding consumables. Microstructure analysis was conducted on the as-deposited and reheated regions of the weld in each pass. The microhardness distribution was mapped for the whole weld cross section and correlated with the observed microstructure. A nearly flat tip indenter was used to measure the load versus displacement response during micro-scale instrumented indentation test, in order to determine the yield strength for different areas in the weld region. This technique had previously been used as provided by the inventor to determine the apparent yield strength for a wide ra...
Journal of Mechanical Engineering and Sciences, 2021
Instrumented indentation technique gives the possibility to determine the mechanical properties f... more Instrumented indentation technique gives the possibility to determine the mechanical properties for small specimens and material in service. Several researchers have attempted to evaluate this approach experimentally and investigated the factors that affect it by using different indenter’s geometries for different engineering materials. In this work, the instrumented indentation technique was used to evaluate the mechanical properties experimentally and numerically using finite element simulation to understand the contact mechanics between the indenter surface and the substrate for two types of steel alloys namely ASTM516-G70 and AISI1010 steel. Two shapes of indenters, blunt (spherical) and sharp (Vickers) were used. The results were then compared with the experimental results extracted from the instrumented indentation test. The results have demonstrated a good agreement between the experimental and the finite element simulation results with error bound a ±5 % for young’s modulus ...
Materials Science and Engineering: A, 2021
Graded cemented carbides have been developed by pre-sintering carbon-deficient compacts and subse... more Graded cemented carbides have been developed by pre-sintering carbon-deficient compacts and subsequently carburizing in this work. The microstructures and the mechanical behaviors of the graded cemented carbides were studied. The formation mechanism of the graded structure can be attributed to the Ostwald ripening induced by the carbon diffusion. The difference of the Ostwald ripening rate in areas of different carbon contents leads to the variation in the WC grain-packing structure, hence driving the flow of the liquid Co from the surface to interior. Theoretical results based on the carbon diffusion in the liquid Co match well with the experimental measurements. The graded cemented carbides possess a good combination of high hardness and high toughness, and indicate an excellent performance in the engineering test. The results also show that a high carburizing temperature and a long soaking time lead to an excessive growth of WC grains in the outer layer, which will block the further diffusion of carbon into the alloy body, and will deteriorate the mechanical behaviors as well.
AL-MUKHTAR JOURNAL OF SCIENCES, 2019
Instrumented indentation technique at micro-scales has become more popular to determine mechanica... more Instrumented indentation technique at micro-scales has become more popular to determine mechanical properties of materials like hardness, modulus of elasticity, and yield strength. It is introduced as a method that finds the stress-strain curve, instead of the traditional tensile test. Furthermore, it gives a possibility to determine the mechanical properties for small specimens and material under operation in the field. Several researchers have attempted to evaluate this method experimentally and to investigate the factors affecting it by using a different shape of indenters, and different types of materials. In the same regard, this research work is conducted to evaluate this method experimentally and by finite element simulation methods. Two types of industrially significant steels were selected; they are namely ASTM516-G70, AISI1010 steel; and two shapes of indenters, blunt and sharp (Spherical, and Vickers) were used. The finite element simulation has been performed by ABAQUS s...
Materials Science and Engineering: A, 2021
Abstract In this study, a novel two-step method consisting of powder metallurgy (PM) and subseque... more Abstract In this study, a novel two-step method consisting of powder metallurgy (PM) and subsequent friction stir processing (FSP) was used for preparing SiC/Al-Mg-Sc-Zr nanocomposites integrating multiple beneficial microstructural factors, including high densification, uniform distribution of SiC nanoparticles, good SiC/Al interfacial bonding and recrystallized fine Al grains. These favorable microstructure factors enables the resultant AMCs to overshadow the classical ductility loss in the particle reinforced AMCs, and achieve good strength-ductility synergy. At room temperature, with increasing the SiC nanoparticle content, the strength of the FSPed samples increases, and the corresponding ductility decreases, but still maintains at a high level. The FSPed AMC with 10 wt% SiC nanoparticles has a highest YS and UTS of about 227 MPa and 329 MPa respectively while maintaining a uniform elongation of nearly 20%. At high temperature (523 K), the strength and ductility variation of the FSPed samples with SiC nanoparticle content is similar to that at room temperature. The YS and UTS of the FSPed AMC with 10 wt% SiC nanoparticles reach about 148 MPa and 166 MPa respectively while the fracture elongation approaches 0.3. The fracture of the FSPed samples shows ductile fracture characteristics at both room and elevated temperatures caused by the microvoid coalescence mechanism. The novel two-step preparation method will assist the development of particle reinforced AMCs with balanced strength and ductility.
Metallography, Microstructure, and Analysis, 2020
In this work, an instrumented indentation technique with a nearly flat tip indenter was used to m... more In this work, an instrumented indentation technique with a nearly flat tip indenter was used to measure the yield strength of API-X80 line pipe weld. Using this technique, the yield strength can be estimated directly from the indentation load–displacement response. The yield strength of the weld metal was measured in the transverse (hoop) and longitudinal (long) directions of the weld, and the results indicated that the weld metal exhibits anisotropy in terms of the yield strength by as much as 100 MPa, which could lead to a non-conservative estimate when strength mismatch is considered. Conventional tensile testing obtained strength values to within 4.6% of the indentation measurements and confirmed the results. Hardness maps also show a 20 HV0.5 difference in the two directions of the weld, which supports anisotropy of yield strength. The microstructure analysis using SEM reveals a slight difference in the grain size, which partially explains the differences in properties.
Journal of Materials Processing Technology, 2022
Abstract The continuous galvanizing process (CGP) under high dew point temperature has been recog... more Abstract The continuous galvanizing process (CGP) under high dew point temperature has been recognized as a viable technique for improving the coating quality of advanced high-strength steels (AHSS). However, the effect of this surface modification technique on resistance spot welding (RSW) process is not clear. The aim of this study is to investigate the role of different surface conditions and initial microstructures obtained through CGP on mechanical properties and failure behavior of resistance spot welded AHSS. It has been shown that the formation of internal oxides during the annealing and subsequent coating process reduced the heat input during RSW, resulting in smaller nugget size and consequently, lower tensile-shear peak load values. Finite element modeling (FEM) and experimental results indicated that in the case of the as-received sample, higher fusion zone/base-metal (FZ/BM) hardness ratio leads to a failure location closer to heat-affected zone (HAZ). However, the lower FZ/BM hardness ratio in the case of annealed-bare and annealed-coated specimens leads to failure location more towards FZ. It was shown that nugget size will not control the failure location during lap-shear loading but does affect nugget load-carrying capability. However, failure behavior is controlled by microstructural characteristics of different weld regions.
Metals
Third-generation advanced high-strength steels (3G-AHSS) are typically galvanized to prevent corr... more Third-generation advanced high-strength steels (3G-AHSS) are typically galvanized to prevent corrosion of the outer body structure. However, the zinc coating on the surface, combined with the locally elevated temperatures generated during the resistance spot welding (RSW) process, can provide the prerequisites for liquid metal embrittlement (LME). This work uses two strategies to control LME crack formation: current pulsation and varying the electrode geometry. These two methods were compared to a baseline welding schedule for a 3G-980-GI coated AHSS. The effectiveness of each method was discussed in terms of the overall weld cracking index and local cracking index. The results showed that increasing the current pulses results in a slower energy input into the weld, which can help to reduce LME crack formation. Introducing more pulses (five to seven pulses) reduced LME crack formation while maintaining the same welding time. Regarding the electrode geometry, the results showed an in...
International Journal of Mechanical Sciences
International Journal of Pressure Vessels and Piping, 2018
Strain-based design (SBD) of pipelines allows stress owing to displacementcontrolled loads origin... more Strain-based design (SBD) of pipelines allows stress owing to displacementcontrolled loads originating from landslides, seismic motions, or frost heaves, to exceed yield stress. In such cases, the distribution of the strain over a large area (pipe) rather than local area (weld) is preferred. Accordingly, in SBD, yield strength of the circumferential girth weld is over matched when compared to the base metal. In this work, API-X80 pipeline steel sections were joined together using the robotic Gas-Metal Arc Welding (GMAW) process; filler metals and shielding gases were varied to achieve three different levels of strength (even, over and under match) between the weld and base metal. Weld metal and HAZ cross-section microstructures were investigated and correlated with micro-hardness maps to ensure that different mismatch levels were achieved. Yield strengths of the welds in the hoop direction were measured using both instrumented indentation and conventional tensile testing. The instrumented indentation technique used a 100-µm diameter nearly-flat indenter to estimate yield strengths for the welds and heat-affected zones from the load-displacement response for each zone. The measured yield strengths were compared with 0.2% offset tensile yield strength obtained through conventional tensile testing of allweld and base metal specimens. Strength measurements, in the hoop direction, for weld metal from both of the techniques agreed to within 4.6%. The results showed that the nearly-flat tip indentation method can be used as a tool to directly estimate strength mismatch of pipeline girth welds. Measurements of yield strength for narrow coarse and fine grained heat-affected zones, which cannot be measured through any other method, can also be assessed using the techniques described herein.
Journal of Manufacturing Processes
Journal of Manufacturing Science and Engineering
To accurately model the resistance spot welding (RSW) joint in finite element analysis (FEA), the... more To accurately model the resistance spot welding (RSW) joint in finite element analysis (FEA), the constitutive behavior of materials in various weld regions such as heat-affected zone (HAZ) should be measured. Due to the sharp temperature gradient through RSW specimens, microstructural and corresponding mechanical properties of weld regions are different. Additionally, the size of RSW is small; hence, it is challenging to directly measure the stress–strain curve of materials. In this regard, hardness-scaling and ball-indentation techniques are among the popular methods to in-directly measure the stress–strain curve of these materials. However, the effectiveness of these two techniques on predicting the stress/strain distribution and failure behavior of resistance spot welded advanced high strength steels (AHSS) is not clear. In the present work, the stress–strain curves obtained through hardness-scaling and ball-indentation techniques have been compared. The stress/strain distributi...
Materials & Design, 2022
Welding Journal, 2021
Advanced high-strength steels (AHSS) such as complexphase (CP) and high-formability (HF) steel of... more Advanced high-strength steels (AHSS) such as complexphase (CP) and high-formability (HF) steel offer weightsaving advantages for automotive applications such as chassis and frame applications. To prevent material oxidation, materials are often galvanized to protect the substrate from corrosion. However, the weldability of coated AHSS becomes challenging due to the trapping of zinc in the weld molten pool, which could lead to weld defects such as porosity and liquid metal embrittlement cracks. This work focused on the weldability of AHSS (CP800 and 980HF) using the gas metal arc welding process. The roles of both galvanized iron coating and filler material on weld strength were investigated. The welds were performed using two different filler materials: a low-strength filler (ER70S-6) and a high-strength filler (ER100S-6) material. In addition, two different joint configurations were studied: lap joints and butt joints. The results showed that the butt joint had a higher strength com...
This study aims to develop a new method to characterize mechanical properties using instrumented ... more This study aims to develop a new method to characterize mechanical properties using instrumented indentation. The indentation results were correlated with observed microstructure in weld metal of gas metal arc welding (GMAW) pipeline joints with their mechanical properties such as: hardness and yield strength. The focus of this work was on a representative API-X80 grade weldment using different commercial welding consumables. Microstructure analysis was conducted on the as-deposited and reheated regions of the weld in each pass. The microhardness distribution was mapped for the whole weld cross section and correlated with the observed microstructure. A nearly flat tip indenter was used to measure the load versus displacement response during micro-scale instrumented indentation test, in order to determine the yield strength for different areas in the weld region. This technique had previously been used as provided by the inventor to determine the apparent yield strength for a wide ra...
Journal of Mechanical Engineering and Sciences, 2021
Instrumented indentation technique gives the possibility to determine the mechanical properties f... more Instrumented indentation technique gives the possibility to determine the mechanical properties for small specimens and material in service. Several researchers have attempted to evaluate this approach experimentally and investigated the factors that affect it by using different indenter’s geometries for different engineering materials. In this work, the instrumented indentation technique was used to evaluate the mechanical properties experimentally and numerically using finite element simulation to understand the contact mechanics between the indenter surface and the substrate for two types of steel alloys namely ASTM516-G70 and AISI1010 steel. Two shapes of indenters, blunt (spherical) and sharp (Vickers) were used. The results were then compared with the experimental results extracted from the instrumented indentation test. The results have demonstrated a good agreement between the experimental and the finite element simulation results with error bound a ±5 % for young’s modulus ...
Materials Science and Engineering: A, 2021
Graded cemented carbides have been developed by pre-sintering carbon-deficient compacts and subse... more Graded cemented carbides have been developed by pre-sintering carbon-deficient compacts and subsequently carburizing in this work. The microstructures and the mechanical behaviors of the graded cemented carbides were studied. The formation mechanism of the graded structure can be attributed to the Ostwald ripening induced by the carbon diffusion. The difference of the Ostwald ripening rate in areas of different carbon contents leads to the variation in the WC grain-packing structure, hence driving the flow of the liquid Co from the surface to interior. Theoretical results based on the carbon diffusion in the liquid Co match well with the experimental measurements. The graded cemented carbides possess a good combination of high hardness and high toughness, and indicate an excellent performance in the engineering test. The results also show that a high carburizing temperature and a long soaking time lead to an excessive growth of WC grains in the outer layer, which will block the further diffusion of carbon into the alloy body, and will deteriorate the mechanical behaviors as well.
AL-MUKHTAR JOURNAL OF SCIENCES, 2019
Instrumented indentation technique at micro-scales has become more popular to determine mechanica... more Instrumented indentation technique at micro-scales has become more popular to determine mechanical properties of materials like hardness, modulus of elasticity, and yield strength. It is introduced as a method that finds the stress-strain curve, instead of the traditional tensile test. Furthermore, it gives a possibility to determine the mechanical properties for small specimens and material under operation in the field. Several researchers have attempted to evaluate this method experimentally and to investigate the factors affecting it by using a different shape of indenters, and different types of materials. In the same regard, this research work is conducted to evaluate this method experimentally and by finite element simulation methods. Two types of industrially significant steels were selected; they are namely ASTM516-G70, AISI1010 steel; and two shapes of indenters, blunt and sharp (Spherical, and Vickers) were used. The finite element simulation has been performed by ABAQUS s...
Materials Science and Engineering: A, 2021
Abstract In this study, a novel two-step method consisting of powder metallurgy (PM) and subseque... more Abstract In this study, a novel two-step method consisting of powder metallurgy (PM) and subsequent friction stir processing (FSP) was used for preparing SiC/Al-Mg-Sc-Zr nanocomposites integrating multiple beneficial microstructural factors, including high densification, uniform distribution of SiC nanoparticles, good SiC/Al interfacial bonding and recrystallized fine Al grains. These favorable microstructure factors enables the resultant AMCs to overshadow the classical ductility loss in the particle reinforced AMCs, and achieve good strength-ductility synergy. At room temperature, with increasing the SiC nanoparticle content, the strength of the FSPed samples increases, and the corresponding ductility decreases, but still maintains at a high level. The FSPed AMC with 10 wt% SiC nanoparticles has a highest YS and UTS of about 227 MPa and 329 MPa respectively while maintaining a uniform elongation of nearly 20%. At high temperature (523 K), the strength and ductility variation of the FSPed samples with SiC nanoparticle content is similar to that at room temperature. The YS and UTS of the FSPed AMC with 10 wt% SiC nanoparticles reach about 148 MPa and 166 MPa respectively while the fracture elongation approaches 0.3. The fracture of the FSPed samples shows ductile fracture characteristics at both room and elevated temperatures caused by the microvoid coalescence mechanism. The novel two-step preparation method will assist the development of particle reinforced AMCs with balanced strength and ductility.
Metallography, Microstructure, and Analysis, 2020
In this work, an instrumented indentation technique with a nearly flat tip indenter was used to m... more In this work, an instrumented indentation technique with a nearly flat tip indenter was used to measure the yield strength of API-X80 line pipe weld. Using this technique, the yield strength can be estimated directly from the indentation load–displacement response. The yield strength of the weld metal was measured in the transverse (hoop) and longitudinal (long) directions of the weld, and the results indicated that the weld metal exhibits anisotropy in terms of the yield strength by as much as 100 MPa, which could lead to a non-conservative estimate when strength mismatch is considered. Conventional tensile testing obtained strength values to within 4.6% of the indentation measurements and confirmed the results. Hardness maps also show a 20 HV0.5 difference in the two directions of the weld, which supports anisotropy of yield strength. The microstructure analysis using SEM reveals a slight difference in the grain size, which partially explains the differences in properties.
Journal of Materials Processing Technology, 2022
Abstract The continuous galvanizing process (CGP) under high dew point temperature has been recog... more Abstract The continuous galvanizing process (CGP) under high dew point temperature has been recognized as a viable technique for improving the coating quality of advanced high-strength steels (AHSS). However, the effect of this surface modification technique on resistance spot welding (RSW) process is not clear. The aim of this study is to investigate the role of different surface conditions and initial microstructures obtained through CGP on mechanical properties and failure behavior of resistance spot welded AHSS. It has been shown that the formation of internal oxides during the annealing and subsequent coating process reduced the heat input during RSW, resulting in smaller nugget size and consequently, lower tensile-shear peak load values. Finite element modeling (FEM) and experimental results indicated that in the case of the as-received sample, higher fusion zone/base-metal (FZ/BM) hardness ratio leads to a failure location closer to heat-affected zone (HAZ). However, the lower FZ/BM hardness ratio in the case of annealed-bare and annealed-coated specimens leads to failure location more towards FZ. It was shown that nugget size will not control the failure location during lap-shear loading but does affect nugget load-carrying capability. However, failure behavior is controlled by microstructural characteristics of different weld regions.