The effect of the lower stress level on the cyclic creep behavior of an ods superalloy

1987 ◽  
Vol 18 (6) ◽  
pp. 1029-1033 ◽  
Author(s):  
William L. Kimmerle ◽  
Vincent C. Nardone ◽  
John K. Tien
Keyword(s):  
Stress Level ◽  
Creep Behavior ◽  
Cyclic Creep ◽  
Lower Stress ◽  
Lower Stress Level

The effect of the lower stress level on the cyclic creep behavior of an ods superalloy

1991 ◽  
Vol 18 (6) ◽  
pp. 1029-1033
Author(s):  
William L. Kimmerle ◽  
Vincent C. Nardone ◽  
John K. Tien
Keyword(s):  
Stress Level ◽  
Creep Behavior ◽  
Cyclic Creep ◽  
Lower Stress ◽  
Lower Stress Level

scholarly journals A STUDY ON EFFECTS OF YOGA AND ACADEMIC ACHIEVEMENT OF HIGH SCHOOL STUDENTS

2018 ◽  
Vol 6 (7) ◽  
pp. 23-27
Author(s):  
Christal Jeba N
Keyword(s):  
High School ◽  
Academic Achievement ◽  
Academic Performance ◽  
High School Students ◽  
Stress Level ◽  
The Other ◽  
Competitive Performance ◽  
Lower Stress ◽  
School Students ◽  
Lower Stress Level

The article focuses on assessing facts of a study on effects of yoga and academic achievement of high school students’. Transcendental meditation reduces stress and improves academic performance mentally causes increased alertness, and the practice of yoga brings improvement in competitive performance. It is inferred from the present investigation that all the high school students have average level of effect of yoga with respect to all the background variables under study. It was proved that students under consideration scored higher grades and had lower stress level as compared to the other students who do not practice yoga.

scholarly journals The study of the relationship between life limiting factor and stress level for FGH96

2018 ◽  
Vol 165 ◽  
pp. 22031 ◽  
Author(s):  
Didi. Yang ◽  
Yi. Shi ◽  
Guolei. Miao ◽  
Xiaoguang. Yang ◽  
Duoqi. Shi
Keyword(s):  
Fatigue Life ◽  
Stress Level ◽  
Fatigue Tests ◽  
Limiting Factors ◽  
Limiting Factor ◽  
Lower Stress ◽  
Surface Residual Stress ◽  
Nickel Based Superalloy ◽  
Loading Ratio ◽  
Lower Stress Level

FGH96 is a Chinese made powder metallurgy nickel based superalloy. This reserach aims to investigate the effect of stress on the microstructure of the worst fatigue life at 600°C. The specimens were first polished by abrasive paper and then electropolished to elimate the effect of surface residual stress. The fatigue tests were conducted at 600°C, and the loading ratio was 0.05 at the frequency of 5Hz. Tests were conducted at 900, 1000, 1100, 1200MPa respectively. The fatigue life under the same condition were compared and the fractography of specimens were examined under SEM to further identify the life-limiting factors of the material. The initiation mode transferred from facet initiated to inclusion initiated from lower stress level to higher stress level. Meanwhile, the initiation position transferred from internal to surface with the increase of stress level. This means at higher stress level, fatigue life is mainly limited by inclusion at surface while at lower stress level the limit is controlled by internal facet.

scholarly journals Optimasi Bentuk Struktur Elemen Cangkang Pada Pondasi Terapung Menggunakan Metode Algoritma Genetik

2018 ◽  
Vol 18 (2) ◽  
pp. 1-11
Author(s):  
Augusta Adha ◽  
Mahadi Kurniawan
Keyword(s):  
Finite Element ◽  
Stress Level ◽  
Contact Area ◽  
Shell Structure ◽  
External Load ◽  
Plate Theory ◽  
Mindlin Plate ◽  
Lower Stress ◽  
Floating Foundation ◽  
Lower Stress Level

[ID] Prinsip dasar pondasi terapung adalah keseimbangan antara berat struktur atas dan total berat tanah (termasuk didalamnya air tanah) yang dipindahkan oleh konstruksi pondasi tersebut sehingga tidak menghasilkan penurunan struktur. Pondasi terapung sangat baik digunakan pada daerah dengan daya dukung tanah yang rendah atau pada daerah yang memiliki tanah dengan derajat pemadatan yang bervariasi. Hal ini dikarenakan karakteristik pondasi terapung yang membagi gaya ke area kontak yang sangat besar sehingga seluruh area kontak tersebut hanya mengalami tegangan yang relatif kecil. Namun demikian, karena kapasitas dukung pondasi terapung sangat tergantung pada luasan area, maka pondasi terapung menjadi tidak efektif untuk diterapkan pada daerah yang kecil. Salah satu solusi yang dapat digunakan untuk mengatasi permasalahan ini adalah dengan penerapan struktur pelat cangkang (shell structure) pada pondasi terapung untuk meningkatkan luas area bidang kontak pondasi terapung dan tanah. Paper ini membahas optimasi bentuk pelat cangkang yang digunakan pada pondasi terapung agar memiliki daya dukung yang cukup untuk menahan gaya yang ditransferkan oleh struktur atas. Metode algoritma genetik digunakan dalam proses optimasi dimana koordinat dari titik yang menyusun bentuk (shape) struktur cangkang (cn) dipakai sebagai desain variabel. Pada penelitian ini, proses optimasi menggunakan pemodelan dengan 11, 13 dan 15 variabel desain untuk melihat sensitivitas desain variable tersebut terhadap hasil optimasi. Tegangan yang terjadi pada struktur cangkang tersebut di evaluasi dengan Analisa Elemen Hingga dengan perilaku element cangkang seperti model teory pelat Reissner-Midlin. Fungsi tujuan pada penelitian ini adalah meminimalkan penggunaan material untuk membentuk sebuah pondasi terapung dengan fungsi penalti tegangan pada elemen cangkang. [EN] The basic principle of floating foundation is counterforce balancing between the weight of the structure and thetotal weight of the soil (including groundwater) which is displaced by the structure. Floating foundation is effective in areas with low soil bearing capacity because the external load is widely spread that resulting lower stress level in contact area; Hence, it is necessary to design the shape of floating structure that provide adequate uplift whilst also create lower stress level by spreading the external load to wider contact area. This paper discusses the shape optimization of the floating foundations to have sufficient capacity to resist the force transferred by the upper structure whilst also minimize the use of material without resulting element overstress. Genetic algorithm method is used in the optimization process where the coordinates of the points that shape the shell structure (cn) are used as variable designs. In this study, the multivariable optimization using finite element model is investigated . The stress that occurs in the shell structure is evaluated by Finite Element Analysis with the behavior of shell elements based on Reissner-Mindlin plate theory.

scholarly journals Experimental Observation on the Pure Torsional Ratchetting of Polycarbonate Polymer at Room Temperature

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Fucong Lu ◽  
Bencheng Zhang ◽  
Bo Wu ◽  
Zhiwen Wu ◽  
Xiao Suo
Keyword(s):  
Cyclic Loading ◽  
Stress Level ◽  
Room Temperature ◽  
Stress Amplitude ◽  
Peak Stress ◽  
Stress Rate ◽  
Mean Stress ◽  
Loading History ◽  
Lower Stress ◽  
Lower Stress Level

The stress-controlled pure torsional cyclic tests are carried out to investigate the torsional ratchetting of polycarbonate (PC) polymer at room temperature. The effects of applied shear mean stress, stress amplitude, stress rate, peak stress hold, and stress history on the torsional ratchetting are discussed. The shear strain of tubular specimen is measured by a noncontact digital image correlation (DIC) apparatus. The results show that the torsional ratchetting of the polymer obviously depends on the applied shear stress level, stress rate, and peak stress hold; the shear ratchetting strain and its rate increase with the increasing mean stress, stress amplitude, and peak stress hold time and with the decreasing stress rate. Moreover, the torsional ratchetting depends on the stress history. A higher stress level cyclic loading history restrains the evolution of torsional ratchetting in the subsequent lower stress level cyclic loading, while the lower stress level cyclic loading history promotes the torsional ratchetting of the subsequent higher level cyclic loading.

Fatigue behavior of precipitation strengthened Cu–Ni–Si alloy modified by Cr and Zr addition

2020 ◽  
Vol 11 (6) ◽  
pp. 861-873
Author(s):  
Ş. Hakan Atapek ◽  
Spiros Pantelakis ◽  
Şeyda Polat ◽  
Apostolos Chamos ◽  
Gülşah Aktaş Çelik
Keyword(s):  
Design Methodology ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Lower Stress ◽  
Content Type ◽  
Hardened Alloy ◽  
Zr Addition ◽  
Nucleation Sites ◽  
The Matrix ◽  
Lower Stress Level

Purpose The purpose of this paper is to investigate the fatigue behavior of precipitation-strengthened Cu‒2.55Ni‒0.55Si alloy, modified by the addition of 0.25 Cr and 0.25 Zr (wt%), using mechanical and fractographical studies to reveal the effect of microstructural features on the fracture. Design/methodology/approach For strengthening, cast and hot forged alloy was subjected to solution annealing at 900°C for 60 min, followed by quenching in water and then aging at 490°C for 180 min. Precipitation-hardened alloy was exposed to fatigue tests at R=−1 and different stress levels. All fracture surfaces were examined within the frame of fractographical analysis. Findings Fine Ni-rich silicides responsible for the precipitation strengthening were observed within the matrix and their interactions with the dislocations at lower stress level resulted in localized shearing and fine striations. Although, by the addition of Cr and Zr, the matrix consisted of hard Ni, Zr-rich and Cr-rich silicides, these precipitates adversely affected the fatigue behavior acting as nucleation sites for cracks. Originality/value These findings contribute to the present knowledge by revealing the effect of microstructural features on the mechanical behavior of precipitation-hardened Cu‒Ni‒Si alloy modified by Cr and Zr addition.

Prediction of Bending Creep Behavior of Rice Hull Flour/Polypropylene Composite

2012 ◽  
Vol 200 ◽  
pp. 203-206
Author(s):  
Zhao Yang Xu ◽  
Da Gang Li ◽  
Yan Wu
Keyword(s):  
Stress Level ◽  
Creep Behavior ◽  
Equivalence Principle ◽  
Master Curve ◽  
Creep Compliance ◽  
Bending Test ◽  
Rice Hull ◽  
Polypropylene Composite ◽  
Stress Levels ◽  
Compliance Curve

The creep behaviors of rice hull flour/PP composite under different stress levels were studied through bending test. The results show that the bending creep behaviors of rice hull flour/PP composite have obviously correlation to the stress levels. Based on the time-temperature-stress equivalence principle and 15% stress level as a reference, the creep compliance master curve of 15% stress level was constructed by horizontally shift the creep compliance curve of other stress levels, which can predict the creep behavior of rice hull flour/PP composite at the 15% stress level.

scholarly journals Experimental Study on Freeze-Thaw Effects on Creep Characteristics of Rubber Concrete

2022 ◽  
Vol 2022 ◽  
pp. 1-14
Author(s):  
Qi Li ◽  
Fei Xu ◽  
Hemin Zheng ◽  
Junhao Shi ◽  
Jianyu Zhang
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Stress Level ◽  
Creep Behavior ◽  
Mass Loss Rate ◽  
Crumb Rubber ◽  
Dynamic Elastic Modulus ◽  
Freeze Thaw ◽  
Stress Levels ◽  
Rubber Concrete

Crumb Rubber Concrete (CRC) can exhibit high freeze-thaw resistance, but its long-term creep behavior under various freeze-thaw conditions remains unclear, which is essential for the safety of pavement engineering in the severe cold zone. In this study, the freeze-thaw effects on the creep behavior of CRC under different stress levels were systematically analyzed by testing the compressive strength, the uniaxial creep under different stress levels, and the dynamic elastic modulus. To simulate real conditions of the road environment in the cold area, the lowest temperature of −20°C, six freeze-thaw cycles of 0, 30, 60, 90, 120, and 150, and seven different stress levels of 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9 of the compressive strength were employed in this study. The test results showed that the mass loss rate was 6%–11.2% and the compressive strength decreased by 6.51%–47% after 30–150 freeze-thaw cycles. When the stress level reached its critical value, the relative dynamic elastic modulus decreased with the number of freeze-thaw cycles. After 150 freeze-thaw cycles, failure did not appear when the stress level was lower than 50%, above which the creep failure was determined by the stress level and the number of the freeze-thaw cycles. Meanwhile, it was found that the cracking and interfacial debonding between the matrix and the crumb rubber particle were the main reasons for the degradation of CRC creep performance. Finally, a Weibull distribution-based empirical creep damage model was established to predict the failure of CRC, which can enhance its application to related engineering.

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