Stress Relaxation Testing of Service Exposed IN738 for Creep Strength Evaluation

2000 ◽  
Vol 122 (3) ◽  
pp. 451-456 ◽  
Author(s):  
David A. Woodford
Keyword(s):  
Stress Relaxation ◽  
Creep Strength ◽  
Standard Size ◽  
Strength Evaluation ◽  
Management Procedure ◽  
Section Size ◽  
Long Time ◽  
Evaluation Measurement ◽  
Miniature Specimens ◽  
Base Data

Standard size and miniature specimens of IN738 were taken from a service exposed turbine blade and vane for comparative stress relaxation testing at 800C, 850C, and 900C. Base data taken from root section material were used to construct stress versus creep rate parametric curves which could be used directly in design. Up to five decades in creep rates were obtained at each temperature from tests lasting less than one day. The data were also presented in the form of stress versus predicted times to 0.5 percent creep which compared well with available long time creep data. Differences were noted in specimens taken from different locations in the airfoil regions which probably resulted from differences in grain size or orientation. Based on these measurements it was concluded that there was no significant effect of section size on creep strength as defined by this test, and that the alloy was quite insensitive to prior deformation and thermal exposures. A life management procedure, using a combination of creep strength evaluation based on the stress relaxation test and a separate fracture evaluation measurement, is outlined in which end of useful life is defined in terms of minimum acceptable performance levels. [S0742-4795(00)01803-2]

scholarly journals Stress Relaxation Testing of Service Exposed IN738 for Creep Strength Evaluation

1999 ◽  
Author(s):  
David A. Woodford
Keyword(s):  
Stress Relaxation ◽  
Creep Strength ◽  
Standard Size ◽  
Strength Evaluation ◽  
Management Procedure ◽  
Section Size ◽  
Long Time ◽  
Evaluation Measurement ◽  
Miniature Specimens ◽  
Base Data

Standard size and miniature specimens of IN738 were taken from a service exposed turbine blade and vane for comparative stress relaxation testing at 800C, 850C and 900C. Base data taken from root section material were used to construct stress vs. creep rate parametric curves which could be used directly in design. Up to five decades in creep rates were obtained at each temperature from tests lasting less than one day. The data were also presented in the form of stress vs. predicted times to 0.5% creep which compared well with available long time creep data. Differences were noted in specimens taken from different locations in the airfoil regions which probably resulted from differences in grain size or orientation. Based on these measurements it was concluded that there was no significant effect of section size on creep strength as defined by this test, and that the alloy was quite insensitive to prior deformation and thermal exposures. A life management procedure, using a combination or creep strength evaluation based on the stress relaxation test and a separate fracture evaluation measurement, is outlined in which end of useful life is defined in terms of minimum acceptable performance levels.

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.

The Effect of Aging Conditions on the Stress Relaxation Behavior of 17-7PH Stainless Steel

2021 ◽  
Vol 1016 ◽  
pp. 1664-1669
Author(s):  
Shota Yamasaki ◽  
K. Takano
Keyword(s):  
Stainless Steel ◽  
Stress Relaxation ◽  
Dislocation Density ◽  
Cold Working ◽  
Relaxation Behavior ◽  
Age Hardening ◽  
Stress Relaxation Behavior ◽  
Long Time ◽  
Aging Conditions ◽  
High Age

17-7PH stainless steel is high age-hardening property due to precipitate NiAl intermetallics by aging heat treatment after the deformation induced martensitic transformation by cold working. In this study, the effect of aging conditions on stress relaxation behavior of 17-7PH stainless steel was investigated, and the mechanism of the stress relaxation was discussed. The 0.2% proof stress after aging at 753K for 180s-18ks is about 450MPa, and then decreases after 18ks. On the other hand, the stress relaxation ratio decreases by long time aging at 753K. The dislocation density of 17-7PH decreases by long time aging at 753K. The formation of NiAl clusters around 5nm by 3D-AP analysis is observed in 17-7PH aged at 753K for 1.8ks. It is suggested that the reduction of the stress relaxation ratio after long time aging at 753K is caused by NiAl clusters and decreasing mobile dislocation density.

Evaluation on Stress Relaxation Properties of Geomembrane

2010 ◽  
Vol 168-170 ◽  
pp. 1572-1576
Author(s):  
Si Fa Xu ◽  
Yong Zhang ◽  
Zhe Wang
Keyword(s):  
Stress Relaxation ◽  
Tensile Force ◽  
High Stress ◽  
Elastic Model ◽  
Design Strength ◽  
Elapsed Time ◽  
Side Slope ◽  
Design Life ◽  
Liner System ◽  
Long Time

Geomembrane installed on the bottom and the side slope of a waste landfill as liner system is made of high density polyethylene or thermo plastic elastmer polyplopylene. Stress in the geotextile is caused by friction between the waste and the geotextile which is a result of the compression of the disposed waste, and the tensile force is transferred into the liner system by friction. With elapsed time, the stress relaxation will occur under certain strain conditions. If the stress of geomembrane is at high stress for a long period of time, the long time design strength of the geomembrane may be controlled by the creep at the end of the design life. So it is very important for design to determine the stress induced in the geomembrane. In this paper, the authors present a formula based three element visco-elastic model to evaluate the relation between the stress and elapsed time. Then the authors present some results of modeled tests conducted, it is shown that the relation between the material characteristic and temperature by indoor experiment.

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