Papers by Keyword: Stress Relaxation Test

Abstract: The novel research on organic polymer chemistry and physical organic chemistry involve poly(imide) siloxane on advanced and emerging technologies in radiation therapy. The poly(imide siloxane) block copolymers were synthesized at different production conditions for the use of biodegradable and biocompatible materials to use at biomedical products. These block copolymers were produced by using 4,4'-oxydianiline (ODA) and 3,3,4,4-Benzophenone-tetracarboxylic dianhydride (BTDA) to form polyimide hard block. APPS and BTDA formed the polysiloxane soft block. The polysiloxane soft blocks were increased by increasing the polyimide hard blocks. Copolymers are synthesized by adjusting the soft and hard segments. Copolymers can be obtained by holding constant hard block segments and by adjusting soft block segments. Hence, flexible poly(imide siloxane) block copolymers were derived. The samples were derived in a flexible rubber form. The prepared copolymers possess the properties of elastomers. Due to these properties, these materials have potential usage in microelectronics devices and medical devices. Poly(imide) siloxane, which can be produced with the desired form and conformed at different configurations, is important in such areas. In this research, the studies on poly(imide) siloxane have supported innovative and comprehensive radiation technology in polymer industries, experimental approaches for the innovative biomedical products. The samples were characterized as flexible rubber form and this property was detected and the creep test of poly (imide) siloxane was performed by Dynamic Mechanical Analyser (DMA).

Abstract: Inconel 718 is a nickel-chromium-iron superalloy which presents excellent mechanical properties at high temperatures, as well as good corrosion resistance and weldability. These characteristics can be optimized with an appropriate control of microstructural features such as grain size and precipitation. Precipitates of different nature can form in these alloys, i.e. γ’’ (a metastable metallic compound Ni₃Nb), γ’ (Ni₃(Ti, Al), carbides and/or δ phase (intermetallic Ni₃Nb). Aging treatments are usually designed to obtain the precipitation required in order to optimize mechanical properties. However, precipitation can also appear induced by deformation and therefore interfere with hot forming operations, such as forging. Under these conditions, precipitation may lead to an increase of the loads required to carry out the process. The aim of the work was the characterization of precipitation kinetics for Inconel 718. With this purpose, stress relaxation tests were carried out at temperatures ranging from 950°C to 800°C. Moreover, different amounts of deformation were applied to the samples, prior to stress relaxation, to evaluate the effect of this variable on inducing precipitation. Some samples were quenched at different relaxation times for metallographic evaluation. The results obtained through mechanical testing, together with a proper characterization of precipitation by Scanning Electron Microscopy, were the basis for obtaining precipitation-time-temperature (PTT) diagrams after different deformation conditions.

Abstract: The purpose of this paper is to investigate the effect of solid solution strengthening on the high temperature creep strength of STS310J1TB. To make clear the effect of solid solution strengthening, the stress abrupt change test was carried out to observe the instantaneous plastic strain and the stress relaxation test was carried out to investigate the ratio of solid solution strengthening to applied stress. The instantaneous plastic strain was observed in the stress abrupt change test of STS310S, while it was absent in STS310J1TB. This clearly indicates that the dislocations glide viscously in STS310J1TB, while they move in a free flight manner in STS310S. As a result of TEM observation, the dislocation structure of STS310J1TB is more uniform than that of STS310S. From the analysis of the stress relaxation curve, the effective stress to total applied stress was found to be about 16 %.