Softening-precipitation interaction in a Nb-and N-bearing austenitic stainless steel under stress relaxation

Sá, Elivaldo Ribeiro; Rodrigues, Samuel Filgueiras; Aranas, Clodualdo; Siciliano, Fulvio; Reis, Gedeon Silva; Cabrera, J.M.; Silva, Eden Santos

doi:10.1016/j.jmrt.2020.05.066

Cited by 9 publications

(4 citation statements)

References 27 publications

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“…Based on the previous experiments, it has been shown that when the initial stress of the prestressed steel wire was less than 0.5 times the value of the ultimate tensile strength Ry, the influence of the relaxation of the steel wire could be ignored [37][38][39][40][41][42]. The maximum initial prestress applied to the steel wire in this test was 0.3Ry (0.3Ry < 0.5Ry).…”

Section: Stress Variation Law Of Prestressed Steel Wirementioning

confidence: 83%

Experimental Study on Long-Term Mechanical Properties of Prestressed Glulam Continuous Beams

et al. 2022

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To study the effect of wood creep on the long-term performance of prestressed glulam continuous beams, a 180-day test was carried out on beams configured with different numbers of steel wires (2, 4, 6) and with different prestress values (0, 7, 14 kN). By investigating the stress loss of the steel wires in the beam and the change in the mid-span deflection over time, the factors influencing the creep of the continuous beam were analyzed. Three models were selected to fit the creep process of the test beams. Moreover, the creep deformation coefficient θ was introduced to reflect the influence of glulam creep on the deflection change in the test beams and to predict the total deflection of the beam within 50 years. The results showed that with increasing the number of steel wires and the prestress value on the beams, the total stress of the steel wires declined more and faster. Increasing the number of steel wires or decreasing the prestress force value could effectively restrain the change speed of the mid-span long-term deflection of the beam. Three models were compared, and the power-law equation was the most accurate. At familiar steel wire quantities and force levels, the θ value of the test beams within the design service life of 50 years was determined to be 1.28–2.29.

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Section: Stress Variation Law Of Prestressed Steel Wirementioning

confidence: 83%

Experimental Study on Long-Term Mechanical Properties of Prestressed Glulam Continuous Beams

et al. 2022

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“…In this test, the stress variation of the steel bars was caused by two factors, one was the relaxation of the steel bars, and the other was the creep characteristic of the glulam. Previous studies showed that the relaxation of the steel bars was not significant anymore when the initial stress of the prestressed steel bars was less than 0.5 times value of the ultimate tensile strength R y [26][27][28][29][30][31][32][33]. Since the maximum prestress applied in this study was 60 MPa < 0.5fu = 270 MPa, the stress variation caused by the relaxation of the steel bars was ignored, and it was considered that the stress variation of the steel bars was mainly caused by the creep of the glulam.…”

Section: Stress Variation Of Steel Barsmentioning

confidence: 99%

Long-Term Loading Test of Reinforced Glulam Beam

Guo¹,

Ren²,

Li³

et al. 2022

Journal of Renewable Materials

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Due to creep characteristics of wood, long-term loading can cause a significant stress loss of steel bars in reinforced glulam beams and high long-term deflection of the beam midspan. In this study, 15 glulam beams were subjected to a 90-day long-term loading test, and the effects of long-term loading value, reinforcement ratio and prestress level on the stress of steel bars, midspan long-term deflection, and other parameters were compared and analyzed. The main conclusions drawn from this study were that the long-term deflection of the reinforced glulam beams accounted for 22.5%, 20.6%, and 18.2% of the total deflection respectively when the loading value was 20%, 30%, and 40% of the estimated ultimate load under the long-term loading. The higher the loading level was, the smaller the proportion of the long-term deflection in the total deflection was. Compared with ordinary glulam beams, the long-term deflection of the reinforced glulam beam was even smaller. Under the condition of the constant loading level, the total stress value of the steel bars decreased by 17.5%, 13.6%, and 9.1%, and the proportion of the long-term deflection of the beam midspan in the total deflection was 26.9%, 24.2%, and 20.6% respectively when the reinforcement ratio was 2.05%, 2.68 %, and 3.39%. With the increase of the reinforcement ratio, the stress loss of the steel bars decreased, and the proportion of the long-term deflection decreased as well. When other conditions remained constant and the prestress level of the steel bars was 0 MPa, 30 MPa, and 60 MPa, the total stress value of the steel bars decreased by 9.1%, 9.4%, and 10.2%, respectively, and the proportion of the long-term deflection in the total deflection was 20.6%, 26.1%, and 64.9%, respectively. With the increase of the prestress value, the stress loss of the steel bars increased, and the proportion of the long-term deflection increased as well.

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“…Another factor to keep in mind is the influence of solute supersaturation, since the steel was kept at the soaking temperature of 1250 • C for 300 s, and Nb and N supersaturation in the austenite increases with decreasing temperature. Strain-induced precipitation is known to occur due to such supersaturation, which increases the nucleation rate and accelerates precipitation kinetics, and the higher this precipitation the greater its influence on SRX [45]. The supersaturation of Nb in the austenite of this steel at T ≤ 1050 • C is higher than at T ≤ 1100 • C. Thus, precipitation at higher temperatures may be too slow, t p > 400 s, to inhibit SRX, which is not the case at lower temperatures.…”

Section: Microstructural Featuresmentioning

confidence: 99%

Optimization of Thermomechanical Processing under Double-Pass Hot Compression Tests of a High Nb and N-Bearing Austenitic Stainless-Steel Biomaterial Using Artificial Neural Networks

Sulzbach

Rodrigues

et al. 2022

Metals

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Physical simulation is a useful tool for examining the events that occur during the multiple stages of thermomechanical processing, since it requires no industrial equipment. Instead, it involves hot deformation testing in the laboratory, similar to industrial-scale processes, such as controlled hot rolling and forging, but under different conditions of friction and heat transfer. Our purpose in this work was to develop an artificial neural network (ANN) to optimize the thermomechanical behavior of stainless-steel biomaterial in a double-pass hot compression test, adapted to the Arrhenius–Avrami constitutive model. The method consists of calculating the static softening fraction (Xs) and mean recrystallized grain size (ds), implementing an ANN based on data obtained from hot compression tests, using a vacuum chamber in a DIL 805A/D quenching dilatometer at temperatures of 1000, 1050, 1100 and 1200 °C, in passes (ε1 = ε2) of 0.15 and 0.30, a strain rate of 1.0 s−1 and time between passes (tp) of 1, 10, 100, 400, 800 and 1000 s. The constitutive analysis and the experimental and ANN-simulated results were in good agreement, indicating that ASTM F-1586 austenitic stainless steel used as a biomaterial undergoes up to Xs = 40% of softening due solely to static recovery (SRV) in less than 1.0 s interval between passes (tp), followed by metadynamic recrystallization (MDRX) at strains greater than 0.30. At T > 1050 °C, the behavior of the softening curves Xs vs. tp showed the formation of plateaus for long times between passes (tp), delaying the softening kinetics and modifying the profile of the curves produced by the moderate stacking fault energy, γsfe = 69 mJ/m2 and the strain-induced interaction between recrystallization and precipitation (Z-phase). Thus, the use of this ANN allows one to optimize the ideal thermomechanical parameters for distribution and refinement of grains with better mechanical properties.

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Softening-precipitation interaction in a Nb-and N-bearing austenitic stainless steel under stress relaxation

Cited by 9 publications

References 27 publications

Experimental Study on Long-Term Mechanical Properties of Prestressed Glulam Continuous Beams

Experimental Study on Long-Term Mechanical Properties of Prestressed Glulam Continuous Beams

Long-Term Loading Test of Reinforced Glulam Beam

Optimization of Thermomechanical Processing under Double-Pass Hot Compression Tests of a High Nb and N-Bearing Austenitic Stainless-Steel Biomaterial Using Artificial Neural Networks

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