The dynamic stress-strain characteristics of magnesium alloys have not been clarified sufficiently. Thus, the study investigated both the compressive and tensile dynamic stress-strain characteristics of representative magnesium alloys: AZ61A-F, ZK60A-T5 and AZ31B-F at wide strain rate and temperature ranges. About the strain rate dependency, the dynamic stresses are higher than the static ones under both compressive and tensile loads at elevated temperatures; however the dynamic stress-strain relations change slightly in the dynamic strain rate range. Thus, the magnesium alloys has little strain rate dependence. However, the elongation of the dynamic stress-strain relations under tensile load tends to be larger than that of static one. About the temperature dependency, the yield and flow stresses of the investigated magnesium alloys under compressive load decrease abruptly at temperatures higher than about 600 K in the wide strain rate range. Meanwhile, the ones under tensile load decrease with the temperature more gently. Totally, the magnesium alloys exhibit low temperature dependence. Furthermore, as well known, the yield stresses caused under the tensile load exhibit about twice as high as those under compressive load. This study verified that such a characteristic can be observed over a wide strain rate and temperature ranges.
This paper presents a stochastic method to approximate the thermal deformation of a machine tool, by using the temperature changes of the body. The method examines the relationship between the thermal deformations and temperature changes of plural positions on a machine tool, and determines the appropriate temperature measuring points. In addition, the approximate equation of the thermal deformation is drawn by t-test, which uses those influential temperature changes as parameters. This study shows that the approximation equation of the thermal deformations can be expressed in a simple form with few parameters, and remarkably improve cutting processing.
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