Calculation of Reloading Stress Relaxation Behavior Based on Creep Equations for 1Cr-0.5Mo-0.25V Steel

In order to analyze the stress relaxation behavior under repeated loadings for 1Cr-0.5Mo-0.25V steel, a stress relaxation model based on creep equations has been developed. The model was implemented into the ANSYS finite element program in terms of user define material model. The calculated results were compared to the observed results of uniaxial reloading stress relaxation testing, which were performed by the National Research Institute for Metals of Japan (NRIM) for 1Cr-0.5Mo-0.25V stainless steel bolting material at 500°C. It was shown that the proposed model could be applied for the present data. The calculated residual stresses versus time curves were in good agreement with the observed for initial stress level of 297.1MPa at 500°C and for specific reloading time intervals of 24, 72, 240, and 720 hours.

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Reloading Stress Relaxation Behavior Analysis Based on a Creep Model for High Temperature Bolting Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.328.950 ◽

2013 ◽

Vol 328 ◽

pp. 950-954

Author(s):

Wei Wei Zhang ◽

Hong Xu ◽

Hong Yuan Li

Keyword(s):

High Temperature ◽

Stress Relaxation ◽

Steady State Creep ◽

Relaxation Behavior ◽

Creep Model ◽

National Research Institute ◽

Time Intervals ◽

Stress Relaxation Behavior ◽

Proposed Model ◽

Good Agreement

An analytical method based on a creep model is being developed to investigate the effect of retightening on stress relaxation behavior for high-temperature turbine and valve studs/bolts. In order to validate the approach, the calculated results are compared to the results of uniaxial reloading stress relaxation testing, which were performed by the National Research Institute for Metals of Japan (NRIM) for 12Cr-1Mo-1W-1/4V stainless steel bolting material at 550°C. It was shown that the proposed model based on Altenbach-Gorash-Naumenko creep model for the primary and steady state creep could be applied for the present data. The calculated residual stresses versus time curves were in good agreement with the measured for initial stress level of 273.6MPa at 550°C and for specific reloading time intervals of 24, 72, 240, and 720 hours.

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Investigation on Effect of Slide Motion Control on Stamping of High Strength Steel Sheets

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.554-557.1331 ◽

2013 ◽

Vol 554-557 ◽

pp. 1331-1337 ◽

Cited By ~ 1

Author(s):

Masato Takamura ◽

Shigeru Nishimura ◽

Hideyuki Sunaga

Keyword(s):

Stress Relaxation ◽

Motion Control ◽

High Strength Steel ◽

High Strength ◽

Material Model ◽

Relaxation Behavior ◽

Stress Relaxation Behavior ◽

Automotive Body ◽

Steel Sheets ◽

Servo Press

High strength steel sheets are increasingly used in automotive body parts with the aim of weight reduction, but their use urgently requires further improvement in sheet forming technology to overcome difficulties such as poor formability, dimensional inaccuracy, etc. On the other hand, servo press facilities are becoming increasingly used in industry and many attempts are being made to bring out their characteristic features for enhancing the formability of high strength steel sheets. Although some of these attempts have been successful in finding the advantages of servo presses for improving formability and dimensional accuracy, the mechanisms of such improvements have yet to be clarified in conjunction with the mechanical properties of the materials used. One of the most remarkable features of the servo press lies in its flexibility in slide motion control. It is thus effective to investigate the relevance of strain rate sensitivity of a material to the mechanism of improvement in formability enabled by the flexible slide motion of the servo press. However, very few studies have been carried out with material testing, material modeling, and numerical analyses combined with experimental verifications. In this study, Norton’s creep model was implemented in the FEM solver in order to take into account visco-elasto-plastic deformation including stress relaxation behavior. Parameters for the visco-elasto-plastic material model were identified through physical measurements and FEM simulations of uniaxial tension and crosshead displacement dwell tests, as shown in Fig. 1. The identified material model was applied to sheet forming simulations of an automotive body part and validity of the model was examined by comparing with stamping experiments using a servo press with a variety of slide motions. Numerical results with the identified material model showed the same tendency with respect to the slide motions as the experimental results. Stress relaxation behavior was found to be an important factor for improving formability enabled by modifying the slide motion.

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Change in intragranular misorientation during stress relaxation behavior in Cu-Ni-Si alloy subjected to continuous cyclic bending

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1121/1/012030 ◽

2021 ◽

Vol 1121 (1) ◽

pp. 012030

Author(s):

Tatsuya Fukutomi ◽

Narumi Komei ◽

Yoshimasa Takayama ◽

Hideo Watanabe

Keyword(s):

Stress Relaxation ◽

Relaxation Behavior ◽

Stress Relaxation Behavior ◽

Cyclic Bending

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Effects of accelerator type on stress relaxation behavior and network structure of aged natural rubber/chloroprene rubber vulcanizates

Journal of Elastomers & Plastics ◽

10.1177/0095244316663268 ◽

2016 ◽

Vol 49 (5) ◽

pp. 381-396 ◽

Cited By ~ 7

Author(s):

Farzad A Nobari Azar ◽

Murat Şen

Keyword(s):

Stress Relaxation ◽

Natural Rubber ◽

Network Structure ◽

Structural Changes ◽

Relaxation Behavior ◽

Stress Relaxation Behavior ◽

Rubber Blends ◽

Chloroprene Rubber ◽

Weather Changes ◽

Behavior Network

Natural rubber/chloroprene rubber (NR/CR) blends are among the commonly used rubber blends in industry and continuously are exposed to severe weather changes. To investigate the effects of accelerator type on the network structure and stress relaxation of unaged and aged NR/CE vulcanizates, tetramethyl thiuram disulfide, 2-mercaptobenzothiazole, and diphenyl guanidine accelerators have been chosen to represent fast, moderate, and slow accelerator groups, respectively. Three batches have been prepared with exactly the same components and mixing conditions differing only in accelerator type. Temperatures scanning stress relaxation and pulse nuclear magnetic resonance techniques have been used to reveal the structural changes of differently accelerated rubber blends before and after weathering. Nonoxidative thermal decomposition analyses have been carried out using a thermogravimetric analyzer. Results indicate that there is a strong interdependence between accelerator type and stress relaxation behavior, network structure, cross-linking density, and aging behavior of the blends. Accelerator type also affects decomposition energy of the blends.

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