Analysis and Design of a Small, Two-Bar Creep Test Specimen

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Tom H. Hyde ◽  
Balhassn S. M. Ali ◽  
Wei Sun
Keyword(s):  
Finite Element ◽  
Creep Strain ◽  
Creep Test ◽  
Test Specimen ◽  
Test Method ◽  
Finite Element Analyses ◽  
Analysis And Design ◽  
Specimen Type ◽  
Reference Stress ◽  
Uniaxial Creep

In this paper, a new small-sized (two-bar) specimen type, which is suitable for use in obtaining both uniaxial creep strain and creep rupture life data, is described. The specimen has a simple geometry and can be conveniently machined and loaded (through pin-connections) for testing. Conversion relationships between the applied load and the corresponding uniaxial stress, and between the measured load-line deformations and the corresponding uniaxial minimum creep strain rate, have been obtained, based on the reference stress method (RSM), in conjunction with finite element analyses. Using finite element analyses the effects of the specimen dimensions on reference stress parameters have been investigated. On this basis, specimen dimension ratio ranges are recommended. The effects of friction, between the loading pins and the specimen surfaces, on the specimen failure time, are also investigated. Test results obtained from two-bar specimen tests and from corresponding uniaxial specimen tests, for a P91 steel at 600 °C, are used to validate the test method. These results demonstrated that the specimen type is capable of producing full uniaxial creep strain curves. The advantages of this new, small, creep test specimen, for determining uniaxial creep data, are discussed and recommendations for future research are given.

scholarly journals Additive Manufacturing and Mechanical Performance of Trifurcated Steel Joints for Architecturally Exposed Steel Structures

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1901
Author(s):  
Pengfei He ◽  
Wenfeng Du ◽  
Longxuan Wang ◽  
Ravi Kiran ◽  
Mijia Yang
Keyword(s):  
Finite Element ◽  
Additive Manufacturing ◽  
Process Parameters ◽  
Mechanical Performance ◽  
Steel Structures ◽  
Mechanical Tests ◽  
Test Method ◽  
Finite Element Analyses ◽  
Steel Joint ◽  
Steel Joints

Additive Manufacturing (AM) technology has unique advantages in producing complex joints in architecturally exposed steel structures. This article focuses on the process of manufacturing and investigating the mechanical properties of a reduced scale model of a trifurcated joint using Selective Laser Melting (SLM) method and mechanical tests, respectively. The orthogonal test method was used to optimize the main AM process parameters. Then the trifurcated steel joint was printed using the optimal process parameters and treated by solid solution and aging treatment. To investigate the mechanical performance of the printed joint, an axial compression test and complimentary finite element analyses were carried out. Failure processes and failure mechanisms of the trifurcated steel joint were discussed in detail. The research results show that the preferred process parameters for printing 316L stainless steel powder are: scanning power 150 W, scanning speed 700 mm/s, and scanning pitch 0.09 mm. Using these AM parameters, trifurcated steel joints with good surface quality, geometrical accuracy and tensile strength are obtained after heat treatment. Our mechanical tests and Finite element analyses results indicate that the failure mechanism in the AM trifurcated joint are similar to those of cast steel joints. Based on these results, we conclude that the AM technology serves as a promising new way for the fabrication of joints with complex geometries.

scholarly journals Small Two-Bar Specimen Creep Testing of Grade P91 Steel at 650°C

2016 ◽  
Vol 35 (3) ◽  
pp. 243-252
Author(s):  
Balhassn S. M. Ali ◽  
Tom H. Hyde ◽  
Wei Sun
Keyword(s):  
Strain Rate ◽  
Creep Strain ◽  
Test Data ◽  
Creep Test ◽  
Uniaxial Stress ◽  
Creep Rupture ◽  
Creep Strain Rate ◽  
P91 Steel ◽  
Uniaxial Creep ◽  
Rupture Data

AbstractCommonly used small creep specimen types, such as ring and impression creep specimens, are capable of providing minimum creep strain rate data from small volumes of material. However, these test types are unable to provide the creep rupture data. In this paper the recently developed two-bar specimen type, which can be used to obtain minimum creep strain rate and creep rupture creep data from small volumes of material, is described. Conversion relationships are used to convert (i) the applied load to the equivalent uniaxial stress, and (ii) the load line deformation rate to the equivalent uniaxial creep strain rate. The effects of the specimen dimension ratios on the conversion factors are also discussed in this paper. This paper also shows comparisons between two-bar specimen creep test data and the corresponding uniaxial creep test data, for grade P91 steel at 650°C.

Assessment of Overlapped Internal and External Volumetric Flaws in p-M Diagram

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Shinji Konosu ◽  
Hikaru Miyata
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Pressure Vessel ◽  
Effective Cross Section ◽  
Finite Element Analyses ◽  
Diagram Method ◽  
Reference Stress ◽  
Common Problems ◽  
Good Agreement

Assessment of overlapped internal and external volumetric flaws is one of the most common problems related to pressure vessel and piping components. Under the current fitness for service rules, such as those provided in ASME, BS, and so on, the procedures for the assessment of these flaws have not yet been defined. In this paper, a reference stress, incorporating the decrease in the effective cross section as a function of flaw depth and flaw angle in a cylinder, has been proposed in order to assess the flaws using the simple p-M (pressure-moment) diagram method. Numerous finite element analyses for a cylinder with overlapped internal and external flaws were conducted to verify the proposed procedure. There is good agreement among them.

Some Geometric Considerations for Rubber—Metal Bond Test Specimens

2006 ◽  
Vol 79 (2) ◽  
pp. 320-337 ◽  
Author(s):  
O. H. Yeoh
Keyword(s):  
Finite Element ◽  
Release Rate ◽  
Test Specimen ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Experimental Studies ◽  
Strain Energy Release ◽  
Finite Element Analyses ◽  
Metal Bond ◽  
Metal Bonds

Abstract Most methods for predicting fatigue lives of rubber components rely heavily on experimental studies that involve specimens subjected to essentially uniform states of deformation. But, in service, rubber components often fail at or near rubber-metal bonds where the state of deformation is far from uniform. Before experimental studies of fatigue failure in the vicinity of rubber-metal bonds, it is prudent to perform an analysis of the specimen geometry to make sure it has been optimized. This paper reports on finite element analyses of cylindrical rubber-metal bond test specimens recommended in ASTM D 429. The results suggest that taller specimens (height/radius ratio ≥ 2) have some advantages. Interpretation in terms of the strain energy release rate is recommended. A new asymmetric test specimen is proposed.

Research on the Conversion Relationship for Three-Point Bending Specimen With Fixed Constraints in the Large Deformation Stage

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Hai-Yang Yu ◽  
Guo-Yan Zhou ◽  
Fa-Kun Zhuang
Keyword(s):  
Large Deformation ◽  
Creep Test ◽  
Geometric Parameters ◽  
Test Method ◽  
Three Point Bending ◽  
Deformation Stage ◽  
Creep Stress ◽  
Uniaxial Creep ◽  
Conversion Coefficients ◽  
Beam Bending

Abstract In this study, based on the rod tensile model, a conversion relationship between three-point bending specimen with fixed constraints (TPBSF) and uniaxial creep data in the large deformation stage is defined by the reference stress method. Using finite element method, conversion coefficients are determined. Then it is verified by the creep test data of A7N01 at 350 °C (Zhuang, F. K., 2014, “Research on Creep Test Method of Small Specimen Based on Beam Bending Theory,” Ph.D. thesis, East China University of Science and Technology, Shanghai, China). The results show that creep stress exponent n is the same, but creep constant B obtained by rod tensile model is much closer to uniaxial creep than beam bending model. Finally, effects of geometric parameters and friction on conversion coefficients are investigated. On this basis, the specimen cross section aspect ratio greater than 1 and the indenter radius larger than 1 mm are recommended to minimize the influence of TPBSF geometric parameters on conversion coefficients. The influence of friction on conversion coefficients can be negligible.

On the Determination of Material Creep Constants Using Miniature Creep Test Specimens

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Tom H. Hyde ◽  
Balhassn S. M. Ali ◽  
Wei Sun
Keyword(s):  
Creep Test ◽  
Test Specimen ◽  
Creep Damage ◽  
Creep Model ◽  
P91 Steel ◽  
Notched Specimen ◽  
Material Constants ◽  
Damage Models ◽  
Uniaxial Creep ◽  
Material Creep

Full size creep test specimens, i.e., conventional uniaxial creep test specimen and Bridgman notch specimens are usually used to determine the full set of material constants for any creep model. However, in many situations, sufficient material is not available for theses specimens to be manufactured from it. Therefore, small creep test specimens have been introduced and used to determine (i) creep constants and (ii) the remaining life time for engineering components. Two commonly used small creep specimen types, i.e., the impression and the small ring creep tests, are used in this paper to determine the steady state creep constants. However, these specimen types are limited for use in determining the secondary creep properties, i.e., they are unable to determine the full set of material creep constants for creep damage models. In this paper the recently developed small two-bar creep test specimen and the newly developed small notched specimen test are described and used to determine a full set of material constants for Kachanov and Liu-Murakami creep damage models. The small notched specimen manufacturing, loading and testing procedures are described in this paper. P91 steel at 600 °C and (Bar-257) P91 steel at 650 °C have been used to compare the material constants obtained from the small two-bar and the small notched creep test specimens with those obtained from the conventional uniaxial creep test specimens and Bridgman notch specimens. The results show remarkably good agreement between the two sets of results.

Creep Properties Assessment of Materials by a Small Cantilever Beam Specimen

2018 ◽  
Author(s):  
Fakun Zhuang ◽  
Shantung Tu ◽  
Guoshan Xie ◽  
Shanshan Shao ◽  
Luowei Cao
Keyword(s):  
Cantilever Beam ◽  
Creep Test ◽  
Uniaxial Stress ◽  
Test Method ◽  
Creep Model ◽  
Beam Specimen ◽  
Secondary Creep ◽  
Creep Tests ◽  
Creep Properties ◽  
Uniaxial Creep

Small specimen creep test techniques have been widely applied in the creep properties assessment of materials for the equipment in-service. In order to acquire the creep data accurately and conveniently, the creep test method with small cantilever beam specimens is proposed. On the basis of Norton-Bailey creep law, analytical creep model for the cantilever beam specimen is derived. With this model, the load can be converted to equivalent uniaxial stress and the displacement rate can be converted to equivalent uniaxial strain rate. The creep properties of Cr-Mo steel are assessed by the cantilever beam specimens creep tests. And the creep parameters are evaluated, which are compared to the uniaxial creep parameters. The results show that parameters obtained from the cantilever beam tests correspond reasonably well with those from uniaxial tests. It proves that the primary and secondary creep properties can be assessed by the cantilever beam specimen tests.

scholarly journals A New Mode Iii Delamination Test for Composites

1992 ◽  
Vol 1 (5) ◽  
pp. 096369359200100 ◽  
Author(s):  
P Robinson ◽  
D Q Song
Keyword(s):  
Finite Element ◽  
Fracture Surface ◽  
Epoxy Composite ◽  
Test Method ◽  
Mode Ii ◽  
Test Results ◽  
Finite Element Analyses ◽  
Initial Test ◽  
Beam Test ◽  
Mode Iii

This letter reports a concept for a Mode III test method which eliminates the Mode II component experienced with the split cantilever beam test method. The success of the design is demonstrated by finite element analyses and by SEM fracture surface photographs. Initial test results are reported for a carbon fibre epoxy composite.

Elasto-Plastic and Creep Analysis of a First Stage Blade in a Land Based Gas Turbine Under Steady State Operating Conditions

2000 ◽  
Author(s):  
Takayuki Sakai ◽  
Takashi Ogata ◽  
Akiyoshi Nomoto ◽  
Kazunori Watanabe
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Gas Turbine ◽  
Creep Strain ◽  
Strain Distribution ◽  
Creep Damage ◽  
Finite Element Analyses ◽  
Combustion Gas ◽  
Cooling Air ◽  
Critical Portion

Because first stage rotor blades are used under severe temperature and stress conditions, damage evaluation procedure for the blades is one of key technology to reduce maintenance costs for land based gas turbine. To calculate damage of the blade, stress/strain distribution should be predicted based on temperature distribution. In this study, first stage blades were analyzed by a finite element method to discuss damage profile within the blade under steady state operating condition. At first, 2-D finite element analyses were carried out to study effect of variation of combustion gas and cooling air conditions on the stress/strain distribution of the blade mid height. As a result, change on cooling air condition did not show significant effect on creep strain distribution within the blade section, whereas increase of inlet temperature of combustion gas caused increase of thermal stress and creep strain. Then, 3-D finite element analyses were carried out to identify critical portion of the whole blade in terms of fatigue and creep damage. Consequently, it was found that the leading edge of the blade would be subjected to larger plastic strain that cause fatigue damage. On the other hand, it was suggested that one-third height of the blade at pressure side surface would be the critical portion in terms of creep damage.

A Basis for Selecting the Most Appropriate Small Specimen Creep Test Type

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
T. H. Hyde ◽  
C. J. Hyde ◽  
W. Sun
Keyword(s):  
Creep Test ◽  
Nuclear Power ◽  
Bulk Material ◽  
Operating Conditions ◽  
Test Method ◽  
Small Ring ◽  
Test Type ◽  
Advantages And Disadvantages ◽  
Uniaxial Creep ◽  
Aero Engines

Many components in conventional and nuclear power plant, aero-engines, chemical plant etc., operate at temperatures which are high enough for creep to occur. These include plain pipes, pipe bends, branched pipes etc., the manufacture of such components may also require welds to be inserted in them. In most cases, only nominal operating conditions (i.e., pressure, temperatures, system load, etc.) are known and hence precise life predictions are not possible. Also, the proportion of life consumed will vary from position to position within a component and the plant. Hence, nondestructive techniques are adopted to assist in making decisions on whether to repair, continue operating or scrap certain components. One such approach is to use scoop samples removed from the components to make small creep test specimens, i.e., sub-size uniaxial creep test specimens, impression creep test specimens, small punch creep test specimens, and small ring (circular or elliptical) creep test specimens. Each specimen type has its own unique advantages and disadvantages and it may not be obvious which one is the most appropriate test method to use. This paper gives a brief description of each specimen and associated test type and describes their practical limitations. The suitability of each of the methods for determining “bulk” material properties is described and it is shown that an appropriate test type can be chosen.

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