title: Simulation of the powder forging process for titanium components using a porous metal plasticity model

authors: Velluvakkandi, Navaneeth

subjects: powder forging

abstract: Powder forging is a technique that has been used to produce fully dense near-net parts from metal powders.  Due to a “low cost titanium” product manufacturing initiative, targeting a reduction in the cost of titanium components, a titanium powder forging technique has gained significant interest.  In titanium powder forging, powder consolidation is a key factor that influences successful component manufacture.  Consolidation during titanium powder forging is dependent on the densification and deformation mechanisms involved.
In this study, a finite element method is used to model the densification and deformation behaviour of titanium powder compacts during powder forging.  The research focuses on developing a simulation capability and identifying a suitable constitutive model to simulate the powder forging process that can predict the relative density distribution.  The simulation is carried out in Abaqus software and the results are compared with experimental results.  A gamma particle radiography technique is used to compare the experimental density results with the simulated results.
The Gurson and Gurson-Tvergaard models are used to predict the relative density of porous titanium powder compacts during upset-powder forging and are used to include the effect of hydrostatic stresses and the extent of densification.  Three different modes of densification, related to powder forging were studied i.e. upset forging, hot-repressing and closed die forging.
The simulation results indicate that both models can be used to determine the relative density during powder forging.  By comparing the simulated results with the experimental results, it is found that the density prediction given by the Gurson-Tvergaard model showed closer agreement with the calculated parameters.

text: Simulation of the powder forging process for titanium components using a porous metal plasticity model Powder forging is a technique that has been used to produce fully dense near-net parts from metal powders.  Due to a “low cost titanium” product manufacturing initiative, targeting a reduction in the cost of titanium components, a titanium powder forging technique has gained significant interest.  In titanium powder forging, powder consolidation is a key factor that influences successful component manufacture.  Consolidation during titanium powder forging is dependent on the densification and deformation mechanisms involved.
In this study, a finite element method is used to model the densification and deformation behaviour of titanium powder compacts during powder forging.  The research focuses on developing a simulation capability and identifying a suitable constitutive model to simulate the powder forging process that can predict the relative density distribution.  The simulation is carried out in Abaqus software and the results are compared with experimental results.  A gamma particle radiography technique is used to compare the experimental density results with the simulated results.
The Gurson and Gurson-Tvergaard models are used to predict the relative density of porous titanium powder compacts during upset-powder forging and are used to include the effect of hydrostatic stresses and the extent of densification.  Three different modes of densification, related to powder forging were studied i.e. upset forging, hot-repressing and closed die forging.
The simulation results indicate that both models can be used to determine the relative density during powder forging.  By comparing the simulated results with the experimental results, it is found that the density prediction given by the Gurson-Tvergaard model showed closer agreement with the calculated parameters.

year: 2014

title: Does haste make waste? The human factors of overtaking land design

authors: Charlton, Samuel G.

subjects: lane design

abstract: The aim of this research was to improve overtaking safety and efficiency through improvements in road signage, markings, geometry and speed control associated with the placement and layout of passing lanes. The approach of the research was to explore the effects of several types of overtaking lane treatments in the safety and controlled environment of a state-of-the-art driving simulator. It was found that under the most benign conditions there were no differential effects of the three treatments. With poorer visibility or more taxing road geometry, the drivers relied more heavily on the road markings and signage and the effects of the treatments become more pronounced. The sensitivity to the more "challenging" situations was borne out by the greater speed differential between merge area sections at these sites.

text: Does haste make waste? The human factors of overtaking land design The aim of this research was to improve overtaking safety and efficiency through improvements in road signage, markings, geometry and speed control associated with the placement and layout of passing lanes. The approach of the research was to explore the effects of several types of overtaking lane treatments in the safety and controlled environment of a state-of-the-art driving simulator. It was found that under the most benign conditions there were no differential effects of the three treatments. With poorer visibility or more taxing road geometry, the drivers relied more heavily on the road markings and signage and the effects of the treatments become more pronounced. The sensitivity to the more "challenging" situations was borne out by the greater speed differential between merge area sections at these sites.

year: 2001

title: Te whakahuatanga i te reo Māori: Kua ahatia e tātou i roto i ngā tau 100 kua hipa nei? (The pronunciation of Māori: What have we done to it in the last 100 Years?)

authors: Harlow, Ray

subjects: Te reo Māori

abstract: In the words of the proverb: 'The land remains, but humankind vanishes.' One should perhaps extend this to read: 'The land remains, humankind vanishes, and language changes.' For languages are old, handed down from one generation to another, but no matter what, they change. Present-day English is not Shakespeare's or Chaucer's language. The pronunciation has changed, new words have entered the language, some words have been lost, the grammar is now different. Māori is like that as well. Over the last two centuries, many aspects of the language have become different. Many words have been borrowed from English, and become part of the language. Many new words have been created in recent years to accommodate the new topics now being spoken about in Māori. Many words have changed their meaning, e.g., 'pūtea' originally a type of basket, but now a 'fund', source of money. In the grammar, there are now constructions being used which were not correct in earlier centuries.So far as the pronunciation is concerned, how is one to observe its development? That is the substance of a research project which has only just now begun, and it is the purpose of this paper to explain the nature of that research and show some of the preliminary findings. Hence the title: The pronunciation of Māori: What have we done to it in the last 100 years? The project is supported by the Marsden Research Fund.

text: Te whakahuatanga i te reo Māori: Kua ahatia e tātou i roto i ngā tau 100 kua hipa nei? (The pronunciation of Māori: What have we done to it in the last 100 Years?) In the words of the proverb: 'The land remains, but humankind vanishes.' One should perhaps extend this to read: 'The land remains, humankind vanishes, and language changes.' For languages are old, handed down from one generation to another, but no matter what, they change. Present-day English is not Shakespeare's or Chaucer's language. The pronunciation has changed, new words have entered the language, some words have been lost, the grammar is now different. Māori is like that as well. Over the last two centuries, many aspects of the language have become different. Many words have been borrowed from English, and become part of the language. Many new words have been created in recent years to accommodate the new topics now being spoken about in Māori. Many words have changed their meaning, e.g., 'pūtea' originally a type of basket, but now a 'fund', source of money. In the grammar, there are now constructions being used which were not correct in earlier centuries.So far as the pronunciation is concerned, how is one to observe its development? That is the substance of a research project which has only just now begun, and it is the purpose of this paper to explain the nature of that research and show some of the preliminary findings. Hence the title: The pronunciation of Māori: What have we done to it in the last 100 years? The project is supported by the Marsden Research Fund.

year: 2005-05