Mg , Si and die geometry effects on the formability and the machinability of recycled aluminium alloys
Mg, Si and die geometry effects on the formability and machinability were experimentally reported, concerning AA6xxx aluminium alloys which were produced by recycling raw material. The aluminium alloys formability characteristics were evaluated during extrusion and open die forging tests estimating the needed load; the machinability characteristics of the same aluminium alloys were conducted via cutting force measurements during simple turning process. Key-Words: formability, machinability, Mg ratio, Si ratio, extrusion test, cutting, recycling
Hot torsion tests to model the deformation behavior of aluminium alloys at hot working temperatures
Abstract Knowledge of the deformation behavior of aluminium alloys at hot working temperatures is very important for high temperature manufacturing processes such as hot extrusion. Hot torsion tests were adopted to model this property in this paper. Constitutive equations for stress and strain were developed based on the functional relationship between torque and twist, which enables the material constants to be identified directly from the hot torsion test data. Hot torsion tests were conducted with the material AA5252 over a range of twist rate from 0.015 to 14.9 rev s −1 and for each twist rate at an initial temperature range of 350–550°C, respectively, which produced data to validate the constitutive equations with the proposed linear regression and the non-linear iteration formats to identify the material constants. A good agreement between the experimental data and the predicted results has been achieved, which demonstrates that the proposed constitutive equations and the methods of determination of the material constants are suitable to model the high temperature deformation behavior of aluminium alloys, which also demonstrates that hot torsion tests can not only produce data to identify material constants but also serve as a basis for the development of constitutive equations.
The Categorical Stability of Gambling Motives Among Community-Recruited Gamblers: A Longitudinal Assessment
Over the past decade, several motivational models have been proposed to explain the role of motives in gambling disorder. In the model captured by the four-factor Gambling Motives Questionnaire Financial (GMQ-F), gamblers are described as being primarily motivated to gamble for ‘coping’, ‘enhancement’, ‘social’, and ‘financial’ reasons. Although this model has received significant empirical support; to date, research assessing the role of motives in gambling disorder has been primarily cross-sectional in nature. Thus, the extent to which gambling motives remain stable over time has yet to be explored. In the current study, the stability versus fluidity of self-assessed gambling motives was investigated using the Quinte Longitudinal Study, a longitudinal dataset of gambling behaviour collected over 5 years. Gambling motives of 2795 gamblers were examined over all five annual assessments. The total proportion of gamblers who stayed in the same primary motive category across each of the 5 consecutive assessments was 22%, indicating substantial fluidity in category membership. Substantial movement between categories was seen for each GMQ-F group, as well as an additional group of non-classified motives. Logistic regression analyses suggest that greater resistance to gambling fallacies significantly predicted stability between the baseline assessment and a follow-up 1 year later, but gambling severity did not. Potential limitations in the study design and opportunities for future research are discussed.