title: Analysis of fracture, fatigue, and metallurgical properties of dissimilar TIG & RFW Welds: S355J2/SS316L and Ti-64/Ti-1023

authors: Das, Rajkumar

abstract: Weld joints comprising dissimilar metals with varying compositions are widely utilized across numerous contemporary industrial sectors such as aerospace, automotive manufacturing, shipbuilding, oil and gas, power generation, and medical device production. They offer cost efficiency, performance enhancement, weight reduction, design flexibility, and functionality. However, welding dissimilar metals with varying compositions poses complexity due to compositional gradient and differences in microstructure, leading to variations in properties across the joint. Gaining insight into the influence of parameters in welding on material properties for manufacturing defect-free welded joints is crucial. Nonetheless, there is a considerable gap in knowledge in understanding the relationship between welding parameters, microstructure, fracture toughness, and fatigue in dissimilar material joints.
This study focuses on investigating how parameters in welding influence the microstructure and fracture toughness of welds between two dissimilar materials i.e. structural steel (S355J2) and stainless steel (SS) (316L) using Rotary Friction Welding (RFW) and Tungsten Inert Gas (TIG) welding. Additionally, the study explores how parameters in welding affect the microstructure and fatigue characteristics of welds between two dissimilar titanium alloys i.e. Ti-6Al-4V (Ti-64) and Ti-10V-2Fe-3Al (Ti-1023) using RFW. To achieve the project objectives, dissimilar welding preforms of S355J2 and SS316L are meticulously prepared using corresponding pipe pup pieces and welded via RFW and TIG processes. A comprehensive series of tests are conducted, including microstructural analysis, tensile, hardness, and fracture toughness characteristics are accomplished using compact tension (CT) specimens extracted from various zones of both dissimilar weld joints. For titanium, dissimilar weld joints are fabricated using a round bar of Ti-64 and Ti-1023 via RFW, and tests, including microstructural analysis, tensile, hardness, and stress-controlled high cycle fatigue (HCF), are performed.
Results reveal significant microstructural variations in both dissimilar welding processes for the S355J2 and SS316L as well as the Ti-64 and Ti-1023 alloys. RFW joint between S355J2 and SS316L shows less instability in hardness across the weld with the highest hardness of 208 HV1 in the thermo-mechanically affected zone (TMAZ) of S355J2. Noticeable changes in hardness are observed across the TIG weld with 419 HV1 at the weld centre line (WCL) due to chromium carbide precipitation and 284 HV1 at the TIG heat affected zone (HAZ) of S355J2 is attributed to martensite formation. Both welds exhibit superior tensile characteristics, with the RFW weld displaying ultimate tensile strength (UTS) of 540 MPa and yield strength (YS) of 367 MPa, while the TIG weld shows UTS of 526 MPa and YS of 300 MPa. Tensile failures predominantly occur on the S355J2 side, exhibiting ductile features. Both welds show nearly identical fracture toughness (KQ) values, closely matching those of the parent metal, whereas, in terms of crack tip opening displacement (CTOD), RFW-WCL shows superior performance with 0.35 mm compared to TIG-WCL's 0.32 mm. Notably, the HAZ of S355J2 in the TIG weld exhibits the lowest CTOD of 0.31 mm. Fractography exhibits ductile failure, except for the TIG WCL, which displays cleavage fracture.
In the RFW joint between Ti-64 and Ti-1023, the highest hardness of 342 HV1 occurs at the WCL, gradually diminishing on either side of the weld, attributed to formation of hard microstructural phases and the growth of secondary alpha (αs) phases. The weld exhibits remarkable tensile properties, comparable with those of the parent metal, with a UTS of 826 MPa and an YS of 792 MPa. Tensile failures primarily manifest on the Ti-1023 side, demonstrating ductile characteristics. The HCF test, conducted at a frequency of 40 Hz with a R value of 0.1, reveals a fatigue strength of the weld at 550 MPa, surpassing that of the Ti-64 parent metal. In all HCF specimens, crack initiates at the surface, with those under higher stress exhibiting a narrow crack propagation area characterized by coarse fatigue striation marks indicative of dominant tensile overloading, while specimens under lower stress reveal a wider crack propagation area with quasi-cleavage facets and very fine fatigue striations.
Overall, the study findings establish that the RFW process yields a robust dissimilar weld joint between different materials S355J2 / SS316l and Ti-64 / Ti-1023.

text: Analysis of fracture, fatigue, and metallurgical properties of dissimilar TIG & RFW Welds: S355J2/SS316L and Ti-64/Ti-1023 Weld joints comprising dissimilar metals with varying compositions are widely utilized across numerous contemporary industrial sectors such as aerospace, automotive manufacturing, shipbuilding, oil and gas, power generation, and medical device production. They offer cost efficiency, performance enhancement, weight reduction, design flexibility, and functionality. However, welding dissimilar metals with varying compositions poses complexity due to compositional gradient and differences in microstructure, leading to variations in properties across the joint. Gaining insight into the influence of parameters in welding on material properties for manufacturing defect-free welded joints is crucial. Nonetheless, there is a considerable gap in knowledge in understanding the relationship between welding parameters, microstructure, fracture toughness, and fatigue in dissimilar material joints.
This study focuses on investigating how parameters in welding influence the microstructure and fracture toughness of welds between two dissimilar materials i.e. structural steel (S355J2) and stainless steel (SS) (316L) using Rotary Friction Welding (RFW) and Tungsten Inert Gas (TIG) welding. Additionally, the study explores how parameters in welding affect the microstructure and fatigue characteristics of welds between two dissimilar titanium alloys i.e. Ti-6Al-4V (Ti-64) and Ti-10V-2Fe-3Al (Ti-1023) using RFW. To achieve the project objectives, dissimilar welding preforms of S355J2 and SS316L are meticulously prepared using corresponding pipe pup pieces and welded via RFW and TIG processes. A comprehensive series of tests are conducted, including microstructural analysis, tensile, hardness, and fracture toughness characteristics are accomplished using compact tension (CT) specimens extracted from various zones of both dissimilar weld joints. For titanium, dissimilar weld joints are fabricated using a round bar of Ti-64 and Ti-1023 via RFW, and tests, including microstructural analysis, tensile, hardness, and stress-controlled high cycle fatigue (HCF), are performed.
Results reveal significant microstructural variations in both dissimilar welding processes for the S355J2 and SS316L as well as the Ti-64 and Ti-1023 alloys. RFW joint between S355J2 and SS316L shows less instability in hardness across the weld with the highest hardness of 208 HV1 in the thermo-mechanically affected zone (TMAZ) of S355J2. Noticeable changes in hardness are observed across the TIG weld with 419 HV1 at the weld centre line (WCL) due to chromium carbide precipitation and 284 HV1 at the TIG heat affected zone (HAZ) of S355J2 is attributed to martensite formation. Both welds exhibit superior tensile characteristics, with the RFW weld displaying ultimate tensile strength (UTS) of 540 MPa and yield strength (YS) of 367 MPa, while the TIG weld shows UTS of 526 MPa and YS of 300 MPa. Tensile failures predominantly occur on the S355J2 side, exhibiting ductile features. Both welds show nearly identical fracture toughness (KQ) values, closely matching those of the parent metal, whereas, in terms of crack tip opening displacement (CTOD), RFW-WCL shows superior performance with 0.35 mm compared to TIG-WCL's 0.32 mm. Notably, the HAZ of S355J2 in the TIG weld exhibits the lowest CTOD of 0.31 mm. Fractography exhibits ductile failure, except for the TIG WCL, which displays cleavage fracture.
In the RFW joint between Ti-64 and Ti-1023, the highest hardness of 342 HV1 occurs at the WCL, gradually diminishing on either side of the weld, attributed to formation of hard microstructural phases and the growth of secondary alpha (αs) phases. The weld exhibits remarkable tensile properties, comparable with those of the parent metal, with a UTS of 826 MPa and an YS of 792 MPa. Tensile failures primarily manifest on the Ti-1023 side, demonstrating ductile characteristics. The HCF test, conducted at a frequency of 40 Hz with a R value of 0.1, reveals a fatigue strength of the weld at 550 MPa, surpassing that of the Ti-64 parent metal. In all HCF specimens, crack initiates at the surface, with those under higher stress exhibiting a narrow crack propagation area characterized by coarse fatigue striation marks indicative of dominant tensile overloading, while specimens under lower stress reveal a wider crack propagation area with quasi-cleavage facets and very fine fatigue striations.
Overall, the study findings establish that the RFW process yields a robust dissimilar weld joint between different materials S355J2 / SS316l and Ti-64 / Ti-1023.

year: 2024-05-23

title: Supportive interactions with primary care doctors are associated with better mental health among transgender people: results of a nationwide survey in Aotearoa/New Zealand.

authors: Treharne, Gareth J.

subjects: LGBTQ

abstract: BACKGROUND: Past research has established that transgender people experience significant disparities in mental health outcomes and healthcare dissatisfaction compared with cisgender people, but more research is needed on how supportive healthcare interactions relate to the mental health of transgender people. OBJECTIVES: The 2 main aims of our analyses were: (i) to establish the most common negative experiences in healthcare and the most common supportive experiences specifically with primary care doctors for transgender people; and (ii) to examine the association of supportive experiences with mental health variables after controlling for demographic factors. METHODS: Data from the 2018 Counting Ourselves nationwide survey of transgender people were analysed using regression modelling. The 948 participants with a primary care doctor or general practitioner were included in analyses. Participants were aged 14-83 years old (mean 30.20). RESULTS: The most common supportive experiences involved primary care doctors treating transgender people equitably, with competence, and with respect. Participants with more negative healthcare experiences had higher psychological distress as well as higher likelihood of reporting nonsuicidal self-injury and suicidality. Conversely, participants with more experiences of supportive primary care doctors had lower psychological distress and were less likely to have attempted suicide in the past 12 months. CONCLUSION: When transgender people receive supportive care from their primary care providers they experience better mental health, despite ongoing negative healthcare experiences. Future research is needed to confirm ways of supporting positive trajectories of mental health for transgender people but these findings demonstrate the importance of positive aspects of care.

text: Supportive interactions with primary care doctors are associated with better mental health among transgender people: results of a nationwide survey in Aotearoa/New Zealand. BACKGROUND: Past research has established that transgender people experience significant disparities in mental health outcomes and healthcare dissatisfaction compared with cisgender people, but more research is needed on how supportive healthcare interactions relate to the mental health of transgender people. OBJECTIVES: The 2 main aims of our analyses were: (i) to establish the most common negative experiences in healthcare and the most common supportive experiences specifically with primary care doctors for transgender people; and (ii) to examine the association of supportive experiences with mental health variables after controlling for demographic factors. METHODS: Data from the 2018 Counting Ourselves nationwide survey of transgender people were analysed using regression modelling. The 948 participants with a primary care doctor or general practitioner were included in analyses. Participants were aged 14-83 years old (mean 30.20). RESULTS: The most common supportive experiences involved primary care doctors treating transgender people equitably, with competence, and with respect. Participants with more negative healthcare experiences had higher psychological distress as well as higher likelihood of reporting nonsuicidal self-injury and suicidality. Conversely, participants with more experiences of supportive primary care doctors had lower psychological distress and were less likely to have attempted suicide in the past 12 months. CONCLUSION: When transgender people receive supportive care from their primary care providers they experience better mental health, despite ongoing negative healthcare experiences. Future research is needed to confirm ways of supporting positive trajectories of mental health for transgender people but these findings demonstrate the importance of positive aspects of care.

year: 2022

title: Review: Memoirs of Active Service

authors: Cheesman, Sue

subjects: Maaka Pepene

abstract: Ka maumahara tonu tatou ki a ratou - we will remember them…poignant last words…   bidding farewell to a generation of veterans moving on...leaving fragments  of memories and diaries for children/grandchildren to honour, celebrate and remember …black costumes billow, fold, swirl and wrap the dancers bodies…wide sweeping arm movements…jumps and turns…slides on all fours - provides the vehicle for five accomplished dancers to fill the space with fluidity and lyricism in this very moving finale, a lament set to Albinoni’s adagio - maybe old soldiers never die.

text: Review: Memoirs of Active Service Ka maumahara tonu tatou ki a ratou - we will remember them…poignant last words…   bidding farewell to a generation of veterans moving on...leaving fragments  of memories and diaries for children/grandchildren to honour, celebrate and remember …black costumes billow, fold, swirl and wrap the dancers bodies…wide sweeping arm movements…jumps and turns…slides on all fours - provides the vehicle for five accomplished dancers to fill the space with fluidity and lyricism in this very moving finale, a lament set to Albinoni’s adagio - maybe old soldiers never die.

year: 2007