title: Mechanical behaviour of Titanium, Ti-6Al-4V (wt %) alloy and Ti-47Al-2Cr (at %) alloy produced using powder compact forging

authors: Nadakuduru, Vijay Navaratna

subjects: mechanical behaviour

abstract: Powder compact forging was used to produce bulk consolidated titanium and Ti-6Al-4V (wt %) and Ti-47Al-2Cr (at%) alloy disks from hydrogenated and dehydrogenated (HDH) and gas atomised powders (GA) powders (in the case of titanium and Ti-6Al-4V) and a mechanically milled powder (in the case of Ti-47Al-2Cr alloy). The bulk titanium and Ti-6Al-4V (wt %) alloy have been produced by forging of the powder compacts. The Ti-47Al-2Cr (at %) alloy was produced using canned powder compact forging of a Ti/Al/Cr composite powder. The purpose of the present study is to investigate the deformation and fracture behaviour of the bulk consolidated as-forged materials, by conducting tensile testing at room temperature (RT) and examination of the fractured specimens which had near-α, α + β and γ phase structures, respectively. It was found that as-forged bulk titanium disk produced using HDH powder showed a yield point with a yield strength of ~700 MPa and with a considerable amount of ductility. While the as-forged Ti-6Al-4V (wt %) alloy produced using HDH powder, fractured prematurely without any yielding. On the other hand yielding was observed in the as-forged Ti-6Al-4V (wt %) alloy produced using GA powder, showing a yield strength of ~970 MPa and a considerable amount of plastic strain to fracture. The bulk consolidated Ti-47Al-2Cr (at %) alloy also fractured prematurely with fracture strength of ~125 MPa. The mechanical behaviour of the as-forged bulk materials was found to be dependent on several factors such as initial powders used, green density of the powder compact, forging parameters used during forging. It was expected that the entrapped gas in green compacts, absorbed oxygen, porosity and inter-particle bonding play an important role on the quality of the as-forged material, which in turn affected the mechanical behaviour of the bulk material.

text: Mechanical behaviour of Titanium, Ti-6Al-4V (wt %) alloy and Ti-47Al-2Cr (at %) alloy produced using powder compact forging Powder compact forging was used to produce bulk consolidated titanium and Ti-6Al-4V (wt %) and Ti-47Al-2Cr (at%) alloy disks from hydrogenated and dehydrogenated (HDH) and gas atomised powders (GA) powders (in the case of titanium and Ti-6Al-4V) and a mechanically milled powder (in the case of Ti-47Al-2Cr alloy). The bulk titanium and Ti-6Al-4V (wt %) alloy have been produced by forging of the powder compacts. The Ti-47Al-2Cr (at %) alloy was produced using canned powder compact forging of a Ti/Al/Cr composite powder. The purpose of the present study is to investigate the deformation and fracture behaviour of the bulk consolidated as-forged materials, by conducting tensile testing at room temperature (RT) and examination of the fractured specimens which had near-α, α + β and γ phase structures, respectively. It was found that as-forged bulk titanium disk produced using HDH powder showed a yield point with a yield strength of ~700 MPa and with a considerable amount of ductility. While the as-forged Ti-6Al-4V (wt %) alloy produced using HDH powder, fractured prematurely without any yielding. On the other hand yielding was observed in the as-forged Ti-6Al-4V (wt %) alloy produced using GA powder, showing a yield strength of ~970 MPa and a considerable amount of plastic strain to fracture. The bulk consolidated Ti-47Al-2Cr (at %) alloy also fractured prematurely with fracture strength of ~125 MPa. The mechanical behaviour of the as-forged bulk materials was found to be dependent on several factors such as initial powders used, green density of the powder compact, forging parameters used during forging. It was expected that the entrapped gas in green compacts, absorbed oxygen, porosity and inter-particle bonding play an important role on the quality of the as-forged material, which in turn affected the mechanical behaviour of the bulk material.

year: 2011

title: Analysis of circuit conditions for optimum intermodulation and gain in bipolar cascomp amplifiers with non-ideal error correction

authors: Balsom, Toby

abstract: The cascoded-compensation or ‘Cascomp’ amplifier offers excellent distortion reduction and thermal distortion rejection, but has not seen widespread use because of a limited gain and increased complexity compared with other topologies. The original theory showed that with the addition of an ideal error amplifier the circuit will completely compensate distortion for suitably chosen degeneration and bias values. This research presents a new, rigorous mathematical proof for conditions of compensation. The authors further develop the proof to include the non-idealities of the error amplifier. It is shown that there exists a second bias point, not exposed by the original analysis that offers improved gain while maintaining distortion cancellation. By reducing the error amplifier degeneration resistance, one can increase a Cascomp circuit's overall gain by several dB while maintaining theoretically perfect distortion compensation. A robust bias point is proposed, which takes the advantage of this new theory by optimising circuit values resulting in a comparatively broader and deeper third-order distortion null. The proposed theory is confirmed with simulation and measurement that show agreement within the bounds of process and component error limits.

text: Analysis of circuit conditions for optimum intermodulation and gain in bipolar cascomp amplifiers with non-ideal error correction The cascoded-compensation or ‘Cascomp’ amplifier offers excellent distortion reduction and thermal distortion rejection, but has not seen widespread use because of a limited gain and increased complexity compared with other topologies. The original theory showed that with the addition of an ideal error amplifier the circuit will completely compensate distortion for suitably chosen degeneration and bias values. This research presents a new, rigorous mathematical proof for conditions of compensation. The authors further develop the proof to include the non-idealities of the error amplifier. It is shown that there exists a second bias point, not exposed by the original analysis that offers improved gain while maintaining distortion cancellation. By reducing the error amplifier degeneration resistance, one can increase a Cascomp circuit's overall gain by several dB while maintaining theoretically perfect distortion compensation. A robust bias point is proposed, which takes the advantage of this new theory by optimising circuit values resulting in a comparatively broader and deeper third-order distortion null. The proposed theory is confirmed with simulation and measurement that show agreement within the bounds of process and component error limits.

year: 2014-11-20

title: A community psychology-based evaluation of the you good? You Good! program delivered by Jade speaks up educational trust in Aotearoa. Empowering tamariki emotional literacy, supporting mental health and encouraging well-being.

authors: Webbon, Abigail

abstract: This evaluation was completed for Jade Speaks Up (JSU) Educational Trust to provide feedback from school teachers and whānau who were involved in the You Good? You Good! (YG?YG!) program, delivered by JSU Educational Trust to schools across Aotearoa. The evaluation goal was to collate the narratives of participating school staff, whānau, and JSU Educational Trust trainers, contrasting experiences and perspectives to determine program effectiveness.
This program is for schools, management, and teachers who work with tamariki, to help teachers and students understand anxiety and develop skills and strategies to have self-agency. JSU Educational Trust developed YG?YG! in 2021, and in 2022 the YG?YG! pilot program was implemented.
This evaluation had three research objectives: 1) Identify and collate the experiences of school staff and other key stakeholders when implementing the YG?YG!, 2) Identify the strengths and barriers to inclusion for tamariki in schools where the program was delivered, and 3) Draw on the stakeholder narratives to assess the program's ability to achieve its goal: enable tamariki to be more agentic in responding to early signs of anxiety in themselves and others.
Information for this evaluation was collected from four sources: 1) Focus groups with JSU trainers, 2) Interviews with school staff, 3) Online surveys with school staff, 4) Archival supervision, and 5) Literature review. Data collected was interpreted through the use of thematic analysis, informed by Community Psychology principles, and the “Six C” framework, guided by He Awa Whiria.
Thematic analysis was completed by coding themes and categories from data sources. The findings from this empirical research engagement informed the analysis and discussion on program effectiveness. 
The findings and analysis found that forming a program design and approach informed with respect for the community’s needs and world-views can enable recognition, awareness and inclusion. A way for the program to begin to do so is to collaborate with communities.
Including researchers from a local community can enable empowerment, build social power, and create responses that promote the needs of the involved communities. The program can champion the field and those they work with by being accountable and enabling transparency.
The program can take an inclusive approach to sustaining its relationships, content relevance, and development for tamariki emotional well-being. The program can work on cultivating and empowering participants to be active partners, enabling the program to be shaped with equity in mind.
Key to program efficacy is acknowledging change and encompassing adaptation. The way to do this is to consider local health issues driven by who experience them, elevating the voice of the community.
Change and need cannot be determined without considering the voice of involved communities. By taking participants feedback, the program can create change for tamariki mental health, whilst acknowledging system and structural barriers, striving for community competence.
Importance lies within the work the program does to enable and support those affected by external factors. The program can acknowledge these challenges, and provide hope that community competence can be achieved.
To conclude, recommendations are presented for JSU Educational Trust to consider.

text: A community psychology-based evaluation of the you good? You Good! program delivered by Jade speaks up educational trust in Aotearoa. Empowering tamariki emotional literacy, supporting mental health and encouraging well-being. This evaluation was completed for Jade Speaks Up (JSU) Educational Trust to provide feedback from school teachers and whānau who were involved in the You Good? You Good! (YG?YG!) program, delivered by JSU Educational Trust to schools across Aotearoa. The evaluation goal was to collate the narratives of participating school staff, whānau, and JSU Educational Trust trainers, contrasting experiences and perspectives to determine program effectiveness.
This program is for schools, management, and teachers who work with tamariki, to help teachers and students understand anxiety and develop skills and strategies to have self-agency. JSU Educational Trust developed YG?YG! in 2021, and in 2022 the YG?YG! pilot program was implemented.
This evaluation had three research objectives: 1) Identify and collate the experiences of school staff and other key stakeholders when implementing the YG?YG!, 2) Identify the strengths and barriers to inclusion for tamariki in schools where the program was delivered, and 3) Draw on the stakeholder narratives to assess the program's ability to achieve its goal: enable tamariki to be more agentic in responding to early signs of anxiety in themselves and others.
Information for this evaluation was collected from four sources: 1) Focus groups with JSU trainers, 2) Interviews with school staff, 3) Online surveys with school staff, 4) Archival supervision, and 5) Literature review. Data collected was interpreted through the use of thematic analysis, informed by Community Psychology principles, and the “Six C” framework, guided by He Awa Whiria.
Thematic analysis was completed by coding themes and categories from data sources. The findings from this empirical research engagement informed the analysis and discussion on program effectiveness. 
The findings and analysis found that forming a program design and approach informed with respect for the community’s needs and world-views can enable recognition, awareness and inclusion. A way for the program to begin to do so is to collaborate with communities.
Including researchers from a local community can enable empowerment, build social power, and create responses that promote the needs of the involved communities. The program can champion the field and those they work with by being accountable and enabling transparency.
The program can take an inclusive approach to sustaining its relationships, content relevance, and development for tamariki emotional well-being. The program can work on cultivating and empowering participants to be active partners, enabling the program to be shaped with equity in mind.
Key to program efficacy is acknowledging change and encompassing adaptation. The way to do this is to consider local health issues driven by who experience them, elevating the voice of the community.
Change and need cannot be determined without considering the voice of involved communities. By taking participants feedback, the program can create change for tamariki mental health, whilst acknowledging system and structural barriers, striving for community competence.
Importance lies within the work the program does to enable and support those affected by external factors. The program can acknowledge these challenges, and provide hope that community competence can be achieved.
To conclude, recommendations are presented for JSU Educational Trust to consider.

year: 2024-11-14