Extent to Which Material Properties Control Fatigue Failure at Elevated Temperatures

2009 ◽  
pp. 123-123-16
Author(s):  
J Wareing ◽  
B Tomkins ◽  
G Sumner
Keyword(s):  
Fatigue Failure ◽  
Material Properties ◽  
Elevated Temperatures

Creep-Fatigue Interaction Effects On Pressure-Reducing Valve Under Cyclic Thermo-Mechanical Loadings Using Direct Cyclic Method

2021 ◽  
Author(s):  
Nak-Kyun Cho ◽  
Youngjae Choi ◽  
Haofeng Chen
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Fatigue Failure ◽  
Material Properties ◽  
Structural Integrity ◽  
Direct Method ◽  
Element Model ◽  
Critical Loading ◽  
Creep Fatigue ◽  
Pressure Reducing Valve

Abstract Supercritical boiler system has been widely used to increase efficiency of electricity generation in power plant industries. However, the supercritical operating condition can seriously affect structural integrity of power plant components due to high temperature that causes degradation of material properties. Pressure reducing valve is an important component being employed within a main steam line of the supercritical boiler, which occasionally thermal-fatigue failure being reported. This research has investigated creep-cyclic plastic behaviour of the pressure reducing valve under combined thermo-mechanical loading using a numerical direct method known as extended Direct Steady Cyclic Analysis of the Linear Matching Method Framework (LMM eDSCA). Finite element model of the pressure-reducing valve is created based on a practical valve dimension and temperature-dependent material properties are applied for the numerical analysis. The simulation results demonstrate a critical loading component that attributes creep-fatigue failure of the valve. Parametric studies confirm the effects of magnitude of the critical loading component on creep deformation and total deformation per loading cycle. With these comprehensive numerical results, this research provides engineer with an insight into the failure mechanism of the pressure-reducing valve at high temperature.

PREDICTION OF PEEK RESIN PROPERTIES FOR PROCESSING MODELING USING MOLECULAR DYNAMICS

2021 ◽  
Author(s):  
KHATEREH KASHMARI ◽  
PRATHAMESH DESHPANDE ◽  
SAGAR PATIL ◽  
SAGAR SHAH ◽  
MARIANNA MAIARU ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Residual Stresses ◽  
Crystallization Kinetics ◽  
Material Properties ◽  
Elevated Temperatures ◽  
Processing Parameters ◽  
Thermomechanical Properties ◽  
Volumetric Shrinkage ◽  
Processing Temperature ◽  
Wide Range

Polymer Matrix Composites (PMCs) have been the subject of many recent studies due to their outstanding characteristics. For the processing of PMCs, a wide range of elevated temperatures is typically applied to the material, leading to the development of internal residual stresses during the final cool-down step. These residual stresses may lead to net shape deformations or internal damage. Also, volumetric shrinkage, and thus additional residual stresses, could be created during crystallization of the semi-crystalline thermoplastic matrix. Furthermore, the thermomechanical properties of semi-crystalline polymers are susceptible to the crystallinity content, which is tightly controlled by the processing parameters (processing temperature, temperature holding time) and material properties (melting and crystallization temperatures). Hence, it is vital to have a precise understanding of crystallization kinetics and its impact on the final component's performance to accurately predict induced residual stresses during the processing of these materials. To enable multi-scale process modeling of thermoplastic composites, molecular-level material properties must be determined for a wide range of crystallinity levels. In this study, the thermomechanical properties and volumetric shrinkage of the thermoplastic Poly Ether Ether Ketone (PEEK) resin are predicted as a function of crystallinity content and temperature using molecular dynamics (MD) modeling. Using crystallization-kinetics models, the thermo-mechanical properties are directly related to processing time and temperature. This research can ultimately predict the residual stress evolution in PEEK composites as a function of processing parameters.

The Elastic Characterization of Composite Based on Ultrasonic Waves

2021 ◽  
Author(s):  
Y. H. Park ◽  
J. Dana
Keyword(s):  
Composite Materials ◽  
Fatigue Failure ◽  
Elastic Constants ◽  
Material Properties ◽  
Weight Ratio ◽  
Transversely Isotropic ◽  
Ultrasonic Waves ◽  
Material Strength ◽  
Isotropic Composite

Abstract Anisotropic composite materials have been extensively utilized in mechanical, automotive, aerospace and other engineering areas due to high strength-to-weight ratio, superb corrosion resistance, and exceptional thermal performance. As the use of composite materials increases, determination of material properties, mechanical analysis and failure of the structure become important for the design of composite structure. In particular, the fatigue failure is important to ensure that structures can survive in harsh environmental conditions. Despite technical advances, fatigue failure and the monitoring and prediction of component life remain major problems. In general, cyclic loadings cause the accumulation of micro-damage in the structure and material properties degrade as the number of loading cycles increases. Repeated subfailure loading cycles cause eventual fatigue failure as the material strength and stiffness fall below the applied stress level. Hence, the stiffness degradation measurement can be a good indication for damage evaluation. The elastic characterization of composite material using mechanical testing, however, is complex, destructive, and not all the elastic constants can be determined. In this work, an in-situ method to non-destructively determine the elastic constants will be studied based on the time of flight measurement of ultrasonic waves. This method will be validated on an isotropic metal sheet and a transversely isotropic composite plate.

Rational Design of Organic Electro-Optic Materials

2001 ◽  
Vol 708 ◽  
Author(s):  
Alex Jen ◽  
Robert Neilsen ◽  
Bruce Robinson ◽  
William H. Steier ◽  
Larry Dalton
Keyword(s):  
Wavelength Division Multiplexing ◽  
Material Properties ◽  
Electrostatic Interactions ◽  
Rational Design ◽  
Elevated Temperatures ◽  
Optical Loss ◽  
Quality Factors ◽  
Electro Optic ◽  
Lattice Hardening

ABSTRACTA number of material properties must be optimized before organic electro-optic materials can be used for practical device applications. These include electro-optic activity, optical transparency, and stability including both thermal and photochemical stability. Exploiting an improved understanding of the structure/function relationships, we have recently prepared materials exhibiting electro-optic coefficients of greater than 50 pm/V and optical loss values of less than 0.7 dB/cm at the telecommunication wavelengths of 1.3 and 1.55 microns. When oxygen is excluded to a reasonable extent, long-term photostability to optical power levels of 20 mW has been observed. Photostability is further improved by addition of scavengers and by lattice hardening. Long-term (greater than 1000 hours) thermal stability of poling-induced electro-optic activity is also observed at elevated temperatures (greater than 80°C) when appropriate lattice hardening is used. The successful improvement of organic electro-optic materials rests upon (1) attention to the design of chromophore structure including design to inhibit unwanted intermolecular electrostatic interactions and to improve chromophore instability and (2) attention to processing conditions including those involved in spin casting, electric field poling, and lattice hardening. A particularly attractive new direction has been the exploitation of dendrimer structures and particularly of multi-chromophore containing dendrimer structures. This approach has permitted the simultaneous improvement of all material properties. Development of new materials has facilitated the fabrication of a number of prototype devices and most recently has permitted investigation of the incorporation of electro-optic materials into photonic bandgap and microresonator structures. The latter are relevant to active wavelength division multiplexing (WDM). Significant quality factors (greater than 10,000) have been realized for such devices permitting wavelength discrimination at telecommunication wavelengths of 0.01 nm.

scholarly journals 3D Printed Chromophoric Sensors

Chemosensors ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 317
Author(s):  
Zachary Brounstein ◽  
Jarrod Ronquillo ◽  
Andrea Labouriau
Keyword(s):  
Thermal Stability ◽  
3D Printing ◽  
Material Properties ◽  
Chemical Structure ◽  
Elevated Temperatures ◽  
Advanced Manufacturing ◽  
Color Changes ◽  
Printed Sensors ◽  
3D Printed ◽  
Manufacturing Techniques

Eight chromophoric indicators are incorporated into Sylgard 184 to develop sensors that are fabricated either by traditional methods such as casting or by more advanced manufacturing techniques such as 3D printing. The sensors exhibit specific color changes when exposed to acidic species, basic species, or elevated temperatures. Additionally, material properties are investigated to assess the chemical structure, Shore A Hardness, and thermal stability. Comparisons between the casted and 3D printed sensors show that the sensing devices fabricated with the advanced manufacturing technique are more efficient because the color changes are more easily detected.

scholarly journals Mechanical Properties of Steels for Cold-Formed Steel Structures at Elevated Temperatures

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Zhen Nie ◽  
Yuanqi Li ◽  
Yehua Wang
Keyword(s):  
Mechanical Properties ◽  
Material Properties ◽  
Elevated Temperatures ◽  
Elasticity Modulus ◽  
Mechanical Performance ◽  
Strain Curve ◽  
Steel Structures ◽  
Test Method ◽  
Stress Relieving ◽  
Cold Formed Steel

It is highly important to clarify the high-temperature mechanical properties in the design of cold-formed steel (CFS) structures under fire conditions due to the unique deterioration feature in material properties under fire environment and associated reduction to the mechanical performance of members. This paper presents the mechanical properties of widely used steels for cold-formed steel structures at elevated temperatures. The coupons were extracted from original coils of proposed full annealed steels (S350 and S420, with nominal yielding strengths 280 MPa and 350 MPa) and proposed stress relieving annealed steels (G500, with nominal yielding strength 500 MPa) for CFS structures with thickness of 1.0 mm and 1.2 mm, and a total of nearly 50 tensile tests were carried out by steady-state test method for temperatures ranging from 20 to 700°C. Based on the tests, material properties including the yield strengths, ultimate strengths, the elasticity modulus, and the stress-strain curve were obtained. Meanwhile, the ductility of steels for CFS structures was discussed. Then, the temperature-dependent retention factors of yield strengths and elasticity modulus were compared to those provided by design codes and former researchers. Finally, a set of prediction equations of the mechanical properties for steels for CFS structures at elevated temperatures was proposed depending on existing tests data.

scholarly journals Monotonic and Fatigue Properties of Steel Material Manufactured by Wire Arc Additive Manufacturing

2020 ◽  
Vol 10 (15) ◽  
pp. 5238 ◽  
Author(s):  
Michael Wächter ◽  
Marcel Leicher ◽  
Moritz Hupka ◽  
Chris Leistner ◽  
Lukas Masendorf ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Material Properties ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Fatigue Properties ◽  
Practical Applications ◽  
Steel Material ◽  
Characteristic Values ◽  
The One ◽  
Wire Arc Additive Manufacturing

In this study, the monotonic and cyclic material properties of steel material of medium static strength produced additively in the wire arc additive manufacturing (WAAM) process were investigated. This investigated material is expected to be particularly applicable to the field of mechanical engineering, for which practical applications of the WAAM process are still pending and for which hardly any characteristic values can be found in the literature so far. The focus of the investigation was, on the one hand, to determine how the material characteristics are influenced by the load direction in relation to the layered structure and, on the other hand, how they are affected by different interlayer temperatures. For this purpose, monotonic tensile tests were carried out at room temperature as well as at elevated temperatures, and the cyclic material properties were determined. In addition, the hardness of the material and the residual stresses induced during production were measured and compared. In addition to the provision of characteristic properties for the investigated material, it was aimed to determine the extent to which the interlayer temperature influences the strength characteristics, since this can have a considerable influence on the production times and, thus, the economic efficiency of the process.

Novel Concept of Experimental Setup for Characterisation of Plastic Yielding of Sheet Metal at Elevated Temperatures

2005 ◽  
Vol 6-8 ◽  
pp. 657-664 ◽  
Author(s):  
Manfred Geiger ◽  
G. van der Heyd ◽  
Marion Merklein ◽  
Wolfgang Hussnätter
Keyword(s):  
Sheet Metal ◽  
Material Properties ◽  
Room Temperature ◽  
Stress Condition ◽  
Elevated Temperatures ◽  
Biaxial Stress ◽  
Experimental Setup ◽  
Special Importance ◽  
Plastic Yielding ◽  
Novel Concept

In times of highest significance of process modelling and numerical simulation characterisation of material properties is of special importance for tools’ and components’ dimensioning. But in general material properties depend on many different influencing variables, e.g. temperature, humidity and many others. Especially in fields of sheet metal forming the mechanical behaviour of components highly differs according to real stress condition. In particular yield loci combine the information of beginning of yielding with a biaxial stress condition, but nevertheless for many materials they have not been determined yet. For all others the existing values are available only at room temperature. In this paper a novel concept of the experimental setup is shown, with which plastic yielding of sheet metal can be examined also at elevated temperatures. In usual biaxial tension tests cruciform specimen are drawn in plane. The new machine-concept, which is presented in this paper, is based on a punch-load moving perpendicular to the sheet. By clamping the specimen restoring forces are induced, which cause in dependence of special developed tool and work piece geometries defined stress conditions. Using an optical measurement system for determination of strains with CCDcameras of very high frame rate allows exact identification of starting plastification by offline analysis. Experiments at elevated temperatures are realised by local heating with a diode laser and a special optical system to reach a homogenous distribution of temperatures in the forming zone. On the one hand these investigations are necessary for many materials to achieve further information on characteristic properties in warm forming, because their data are only known at room temperature. On the other hand some materials, e.g. magnesium wrought alloys, are mostly formed at elevated temperatures (here in the range of 200°C to 250°C), because of its significant higher formability. Thus, material behaviour must be characterised at these temperatures.

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