title: Effects of Gas Nitriding on Fatigue and Crack Initiation of Ti6Al4V produced by Selective Laser Melting

authors: Mukhtar, Aamir

subjects: Science & Technology

abstract: Selective laser melting (SLM) is an additive manufacturing technique which permits fabrication of three dimensional parts by selectively melting consecutive layers of metallic powder. This allows the production of parts with high geometrical complexity. Titanium alloy Ti-6Al-4V (Ti64) is widely used in industry due to its high strength-to-mass ratio, corrosion resistance and biocompatibility. SLM increases the application range of Ti64 because of its flexibility for prototyping any part and its low material waste. Nitriding is a diffusion-based thermo-chemical treatment for interstitial hardening of the surface of Ti64 alloy products. This study characterized the fatigue behaviour of SLM-produced Ti64 nitrided and annealed bars in as-built and machined surface conditions. The surface of the SLM-produced Ti64 parts after gas nitriding showed high values of micro-hardness up to 550 HV just below the surface. Fatigue testing was performed to assess the materials fatigue strength and fractographic imaging was used to examine fracture surface and nitride layer characteristics. Nitriding was found to reduce the fatigue strength of the samples to a similar level irrespective of being in the as-built or machined condition. The effect of nitriding on crack initiation and growth at various stress levels under fatigue loading was investigated.

text: Effects of Gas Nitriding on Fatigue and Crack Initiation of Ti6Al4V produced by Selective Laser Melting Selective laser melting (SLM) is an additive manufacturing technique which permits fabrication of three dimensional parts by selectively melting consecutive layers of metallic powder. This allows the production of parts with high geometrical complexity. Titanium alloy Ti-6Al-4V (Ti64) is widely used in industry due to its high strength-to-mass ratio, corrosion resistance and biocompatibility. SLM increases the application range of Ti64 because of its flexibility for prototyping any part and its low material waste. Nitriding is a diffusion-based thermo-chemical treatment for interstitial hardening of the surface of Ti64 alloy products. This study characterized the fatigue behaviour of SLM-produced Ti64 nitrided and annealed bars in as-built and machined surface conditions. The surface of the SLM-produced Ti64 parts after gas nitriding showed high values of micro-hardness up to 550 HV just below the surface. Fatigue testing was performed to assess the materials fatigue strength and fractographic imaging was used to examine fracture surface and nitride layer characteristics. Nitriding was found to reduce the fatigue strength of the samples to a similar level irrespective of being in the as-built or machined condition. The effect of nitriding on crack initiation and growth at various stress levels under fatigue loading was investigated.

year: 2019

title: Sustaining Management of Indigenous-Owned Resources: rationale for multi-dimensional training in a multi-million dollar mahogany industry in Fiji

authors: Nabalarua, Eci K

subjects: Fiji economy

abstract: This paper contributes to an emerging discourse relating to new pathways towards engaging in holistic development measures among grassroots communities in the Pacific Islands by using the notion of critical mass as a viable option for sustaining real growth in small rural economies. It is argued here that the multi-dimensional training techniques applied in the case of a project involving capacity building among indigenous women in Tailevu Province in Fiji could be applied with equal validity to the multi-million dollar mahogany industry in Fiji. This insight into mahogany suggests by implication that multi-dimensional training has great potential for sustaining effective management of indigenous-based and indigenous-owned resources.

text: Sustaining Management of Indigenous-Owned Resources: rationale for multi-dimensional training in a multi-million dollar mahogany industry in Fiji This paper contributes to an emerging discourse relating to new pathways towards engaging in holistic development measures among grassroots communities in the Pacific Islands by using the notion of critical mass as a viable option for sustaining real growth in small rural economies. It is argued here that the multi-dimensional training techniques applied in the case of a project involving capacity building among indigenous women in Tailevu Province in Fiji could be applied with equal validity to the multi-million dollar mahogany industry in Fiji. This insight into mahogany suggests by implication that multi-dimensional training has great potential for sustaining effective management of indigenous-based and indigenous-owned resources.

year: 2002-07-22

title: Verbs in Māori: The problem of definitional criteria

authors: Whaanga, Hēmi

subjects: te reo Māori

abstract: A range of different types of criteria has been applied at different points in the history of the classification of verbs in Māori. These have included syntactic and morphological criteria, semantic criteria and derivational criteria. Unfortunately, these criteria have not always been applied consistently and this has led to considerable disagreement about the classification of verbs in Māori. In this paper, different accounts of verb classification in Māori are critically examined and it is argued that some of the disagreements can be resolved by acknowledging (a) that words in Māori may be assigned to different word classes in different contexts, and (b) that word classes and sub-classes should be determined on the basis of morphological and syntactic criteria with semantic and derivational information playing a role only in so far as they have observable syntactic and/or morphological consequences.

text: Verbs in Māori: The problem of definitional criteria A range of different types of criteria has been applied at different points in the history of the classification of verbs in Māori. These have included syntactic and morphological criteria, semantic criteria and derivational criteria. Unfortunately, these criteria have not always been applied consistently and this has led to considerable disagreement about the classification of verbs in Māori. In this paper, different accounts of verb classification in Māori are critically examined and it is argued that some of the disagreements can be resolved by acknowledging (a) that words in Māori may be assigned to different word classes in different contexts, and (b) that word classes and sub-classes should be determined on the basis of morphological and syntactic criteria with semantic and derivational information playing a role only in so far as they have observable syntactic and/or morphological consequences.

year: 2000-10