Study of Stress Relaxation for 5056 Alloy in Vacuum Conditions

2016 ◽  
Vol 684 ◽  
pp. 335-345
Author(s):  
Valentin Dmitrievich Yushin ◽  
Valery Ivanovich Tregub ◽  
Sergey V. Voronin
Keyword(s):  
Stress Relaxation ◽  
Flexural Strength ◽  
Relaxation Process ◽  
Initial Stress ◽  
Measurement Accuracy ◽  
Manufacturing Technology ◽  
Dislocation Mechanism ◽  
Main Method ◽  
Stress Levels ◽  
Relationship Of

The aim of the presented work is to establish relationship of behavior of stress relaxation process in 5056 alloy in vacuum conditions for stress levels of 116 MPa, 83 MPa and 50 MPa and temperatures of 293 K and 353 K. Method of circular specimens with equal flexural strength was used as the main method for stress relaxation testing. Results of the studies allowed to develop the advanced methodology for evaluation of stress relaxation, which increases measurement accuracy up to 0.04 MPa. Increase of accuracy was achieved using the proposed new shape of a specimen of equal flexural strength, its manufacturing technology and developed design of accessories for precision marking. It was established that for studied temperatures stress relaxation in vacuum is occurring more intensively independently from level of initial stress. That fact can be explained by increase of influence of dislocation mechanism on stress relaxation. The results of the presented studies serve as a basis for increase of reliability and consistency of dimensions of elements of aircraft's structure and their parts and components, which are operating in vacuum conditions.

scholarly journals Stress Relaxation Aging Behavior and Constitutive Modelling of AA7150-T7751 under Different Temperatures, Initial Stress Levels and Pre-Strains

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1215 ◽  
Author(s):  
Yixian Cai ◽  
Lihua Zhan ◽  
Yongqian Xu ◽  
Chunhui Liu ◽  
Jianguang Wang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Stress Relaxation ◽  
Initial Stress ◽  
Stress Level ◽  
Relaxation Behavior ◽  
Average Error ◽  
Aging Behavior ◽  
Stress Relaxation Behavior ◽  
Stress Levels ◽  
Different Temperatures

Age forming is an advanced manufacture technology for forming large aluminum panels. Temperature, initial stress level and pre-strains have a great effect on the formability and performance. The stress relaxation aging behavior of AA7150-T7751 under different temperatures, initial stress levels and pre-strains was studied through stress relaxation tests, tensile tests and TEM observations. The results show that the formability can be improved with the increase of temperature, initial stress levels and pre-strains. Deformation mechanisms during stress relaxation of the material were analyzed on the basis of creep stress exponent and apparent activation energy. The aging precipitates of the studied alloy were not sensitive to the age forming conditions, but drastically coarsened at over aging temperature, which decreased the mechanical properties. In addition, the relationship between stress relaxation behavior and aging strengthening is discussed. Based on the dislocation theory and the modified Arrhenius equation, a stress relaxation constitutive equation considering the initial mobile dislocation density and temperature dependent activation energy was established. This model can predict very well the stress relaxation behavior under various temperature, stress level and pre-strain conditions, with an average error of 2%.

Stress relaxation from initial stress levels below yield

1971 ◽  
Vol 6 (6) ◽  
pp. 451-459 ◽  
Author(s):  
Peter P. Gillis ◽  
Gordon A. Sargent
Keyword(s):  
Stress Relaxation ◽  
Initial Stress ◽  
Stress Levels

Correlation of fatigue behavior and dynamic mechanical properties of hybrid composites of polypropylene/short glass fibers/hollow glass beads

2021 ◽  
pp. 089270572199319
Author(s):  
Gustavo B Carvalho
Keyword(s):  
Stress Relaxation ◽  
Flexural Strength ◽  
Relaxation Rate ◽  
Hybrid Composites ◽  
Fatigue Behavior ◽  
Glass Fibers ◽  
Glass Beads ◽  
Hollow Glass ◽  
Dynamic Mechanical ◽  
Short Glass

Ternary hybrid composites of Polypropylene (PP)/Short Glass Fibers (GF)/Hollow Glass Beads (HGB) were prepared using untreated and aminosilane-treated HGB, compatibilized with maleated-PP, and with varying total and relative GF/HGB contents. Static/short-term flexural strength properties data revealed, through lower flexural strength values, that the presence of untreated HGB particles induces to fiber-polymer interfacial decoupling at much higher extent than in the presence of aminosilane-treated HGB particles. This phenomenon is also evident when evaluating the data from displacement-controlled three-point bending fatigue tests. Monitored up to 106 cycles, the analyzed hybrid composites presented distinct performance relative to their fatigue stress relaxation rate: the lower the matrix-reinforcements’ interfacial adhesion, more pronounced the stress relaxation rate as a function of the number of fatigue cycles. Dynamic Mechanical Thermal Analysis (DMTA) results could successfully reveal the hybrid composites behavior at the microstructural level when they were submitted to both static flexural test and fatigue, depending on the degree of interfacial interactions between the polymer matrix of PP and the hybrid reinforcements of GF and HGB (with and without aminosilane surface treatment).

scholarly journals Preparation and properties of hybrid materials for high-rise constructions

2018 ◽  
Vol 33 ◽  
pp. 02075 ◽  
Author(s):  
Tatyana Matseevich
Keyword(s):  
Stress Relaxation ◽  
Epoxy Resin ◽  
Relaxation Process ◽  
Hybrid Materials ◽  
Mechanical Performance ◽  
Mechanical Relaxation ◽  
Physical Parameters ◽  
Quasi Equilibrium ◽  
High Rise ◽  
Long Time

The theme of the research is important because it allows to use hybrid materials as finishing in the high-rise constructions. The aim of the study was the development of producing coloured hybrid materials based on liquid glass, a polyisocyanate, epoxy resin and 2.4-toluylenediisocyanate. The detailed study of the process of stress relaxation at different temperatures in the range of 20-100°C was provided. The study found that the obtained materials are subject to the simplified technology. The materials easy to turn different colors, and dyes (e.g. Sudan blue G) are the catalysts for the curing process of the polymeric precursors. The materials have improved mechanical relaxation properties, possess different color and presentable, can be easily combined with inorganic base (concrete, metal). The limit of compressive strength varies from 32 to 17.5 MPa at a temperature of 20 to 100°C. The values σ∞ are from 20.4 to 7.7 MPa within the temperature range from 20 to 100°C. The physical parameters of materials were evaluated basing on the data of stress relaxation: the initial stress σ0, which occurs at the end of the deformation to a predetermined value; quasi-equilibrium stress σ∞, which persists for a long time relaxation process. Obtained master curves provide prediction relaxation behavior for large durations of relaxation. The study obtained new results. So, the addition of epoxy resin in the composition of the precursor improves the properties of hybrid materials. By the method of IR spectroscopy identified chemical transformations in the course of obtaining the hybrid material. Evaluated mechanical performance of these materials is long-time. Applied modern physically-based memory functions, which perfectly describe the stress relaxation process.

Stress Relaxation Behavior of GH4169 Alloy

2020 ◽  
Vol 1013 ◽  
pp. 52-58
Author(s):  
Xu Dong Lu ◽  
Song Yi Shi ◽  
Bo Wen ◽  
Ya Wei Zhang ◽  
Jin Hui Du
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stress Relaxation ◽  
Initial Stress ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Transmission Electron ◽  
Microscopy Techniques ◽  
The Relationship ◽  
Gh4169 Alloy

The relaxation properties of GH4169 alloy were studied contrastively at temperatures ranging from 600 oC to 700 °C and initial stress ranging from 550 MPa to 850 MPa. The relationship between the microstructure and relaxation behavior was evaluated using transmission electron microscopy techniques. It was found that the relaxation limit and relaxation stability of the alloy decreased obviously with the increase of temperature. Further investigations show that the relaxation behavior is mainly depend on both precipitate characteristics and its interaction with dislocations. The alloy with higher strength lever has more excellent stress relaxation stability, because of the inhibition of a large number subgrains on dislocations motion.

“Ʌ”-shaped trend of stress relaxation stability of Inconel718 superalloy with initial stress increasing

Materialia ◽  
2020 ◽  
Vol 9 ◽  
pp. 100570
Author(s):  
Jing Yang ◽  
Jianxin Dong ◽  
He Jiang ◽  
Zhihao Yao
Keyword(s):  
Stress Relaxation ◽  
Initial Stress

scholarly journals Philosophy as a project: descriptors of self-knowledge

2019 ◽  
Vol 72 ◽  
pp. 04006
Author(s):  
Sergey Borisov
Keyword(s):  
Practical Experience ◽  
Educational Process ◽  
Self Awareness ◽  
Holistic View ◽  
Main Method ◽  
Basic Relationship ◽  
Self Knowledge ◽  
Philosophical Project ◽  
Relationship Of

Philosophy as a project is defined by us in practical terms, as a form of spiritual activity, spiritual practice aimed at posing, analyzing, and resolving various worldview issues related to the development of a holistic view of a person and his place in the world. The article presents the main characteristics of the philosophical project of self-knowledge, consisting in self-awareness in the present, in personal self-determination and self-transformation. These characteristics are also applicable to the educational process. The article summarizes the practical experience of building up the process of teaching philosophy based on scientific ignorance. The main factors of this process are personal interest, successful self-realization, the role of a mentor and a friendly environment. The main method is dialogue, clarifying the basic relationship of a person with being. In this context, philosophizing fulfills a therapeutic function, becoming a practice of “self-care”.

Level of Stress and Sleep Duration

1987 ◽  
Vol 64 (1) ◽  
pp. 44-46 ◽  
Author(s):  
Robert A. Hicks ◽  
Eliot R. Garcia
Keyword(s):  
Standard Deviation ◽  
Sleep Duration ◽  
High Stress ◽  
Daily Diaries ◽  
Stress Levels ◽  
Relationship Of ◽  
The Relationship

30 subjects kept daily diaries of sleep-duration and stress levels for 4 mo. From these data, it was determined that during periods of high stress, sleep was reduced by about one standard deviation while during periods of low stress, sleep increased by about one-half a standard deviation. The relationship of these results to the relevant sleep-stress literature was briefly discussed.

Effect of Focusing Status on Dimension Measurement Accuracy in Micro Measurement System Based on CCD

2008 ◽  
Vol 392-394 ◽  
pp. 435-438
Author(s):  
Hua Guo ◽  
L. Bai ◽  
J. Liu ◽  
Y. Shi
Keyword(s):  
Measurement System ◽  
Measurement Accuracy ◽  
Experimental Result ◽  
Evaluation Function ◽  
Dimension Measurement ◽  
Special Software ◽  
Institute Of Technology ◽  
Relationship Of ◽  
The Relationship ◽  
Automatic Focusing

This paper adopted the photoelectric micro measurement system based on CCD which was independently developed by Laboratory of Process Automatic and Detection Harbin Institute of Technology to detect dimension of the small precise parts. Under the various focusing status, it was discovered that articulation of focusing has huge effect on the measurement of measurand. According to the characteristics of measurand, we adopted the entropy function as the evaluation function of automatic focusing, developed a special software to process entropy value of the picked images, and obtained the relationship of focusing evaluation function and measurement error through a large number of experiments. The experimental result effectively verified the effect of articulation of focusing on dimension measurement.

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