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At least 127 records · Page 7

Report on FY 2020 creep, fatigue and creep fatigue testing of Alloy 709 base metal at ORNL

The testing activities and research in support of ASME Code qualification of Alloy 709, an advanced austenitic steel, are being carried out at Oak Ridge National Laboratory (ORNL), Argonne National Laboratory, and Idaho National Laboratory. This report summarizes the status and results of FY 2020 planned testing at ORNL. Uniaxial tensile tests on the electroslag remelt (ESR) solution-annealed plate (heat number 58776-3RBC) with additional heat treatment were performed for the baseline mechanical properties evaluation for ASME code qualification of Alloy 709. The tensile properties were found to meet ASME SA-213 specifications and were comparable to the Nippon Steel NF709 data generated for an ASME Section I Code Case for seamless tubing. ORNL was tasked to carry out a subset of the Code Case testing for creep rupture. Creep rupture data from 18 tests were generated on a solution-annealed ESR plate with a solution annealing temperature of 1100°C. There are total of 19 intermediate and long-term creep rupture tests of Alloy 709 ongoing at ORNL. A preliminary fatigue design curve at 760°C was developed for Alloy 709, and the results show that the fatigue design curve of Alloy 709 is comparable to that of Alloy 800H at 760°C.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Elevated temperature fatigue testing of metals

Material characterization and evaluation conducted for the purpose of calculating fatigue crack initiation lives of components operating at elevated temperatures are discussed. The major technology areas needed to perform a life prediction of an aircraft turbine engine hot section component and the steps required for life prediction are outlined. These include: the determination of the operating environment, the calculation of the thermal and mechanical loading of the component, the cyclic stress strain and creep behavior of the material required for structural analysis, the structural analysis to determine the local stress strain temperature time response of the material at the critical location in the component, and from a knowledge of the fatigue, creep, and failure resistance of the material, a prediction of the life of the component.

Hirschberg, M. H.↗

A miniature fatigue test machine

The objective is to enable the student to generate statistically sound fatigue data sets on wire specimens of varying diameter, microstructure, or material. The student can then assess the effect of these parameters of fatigue resistance. The student can also be exposed to ASTM techniques for fatigue data reduction and presentation. Experiments involving variable amplitude block loading are also easily conducted.

Tipton, Steven M.↗

Sister Rod Destructive Examinations (FY2021) Appendix F: Cyclic Integrated Reversible-Bending Fatigue Tests

As a part of DOE NE High Burnup Spent Fuel Data Project, Oak Ridge National Laboratory (ORNL) is performing destructive examinations (DEs) of high burnup (HBU) (>45 GWd/MTU) spent nuclear fuel (SNF) rods from the North Anna Nuclear Power Station operated by Dominion Energy. The SNF rods, called sister rods or sibling rods, are all HBU and include four different kinds of fuel rod cladding: standard Zircaloy-4 (Zirc-4), low-tin (LT) Zirc-4, ZIRLO, and M5. This appendix documents the status of the ORNL Phase 1 DE activities related to tests of the sister rods using the Cyclic Integrated Reversible-Bending Fatigue Tester (CIRFT) in Phase 1 of the sister rod test program.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Sister Rod Destructive Examinations (FY22) Appendix F: Cyclic Integrated Reversible-Bending Fatigue Tests

This report documents work performed under the Spent Fuel and Waste Disposition’s Spent Fuel and Waste Science and Technology program for the US Department of Energy (DOE) Office of Nuclear Energy (NE). This work was performed to fulfill Level 3 Milestone M3SF-22OR010201046, “Draft FY2022 ORNL Report on High Burnup Sibling Pin Testing Results,” within work package SF-22OR01020104 and is an update to the work reported in M2SF-22OR010201047, M2SF-21OR010201032, M2SF-19ORO010201026 and M2SF-19OR010201028. As a part of DOE NE High Burnup Spent Fuel Data Project, Oak Ridge National Laboratory (ORNL) is performing destructive examinations (DEs) of high burnup (HBU) (>45 GWd/MTU) spent nuclear fuel (SNF) rods from the North Anna Nuclear Power Station operated by Dominion Energy. The SNF rods, called sister rods or sibling rods, are all HBU and include four different kinds of fuel rod cladding: standard Zircaloy-4 (Zirc-4), low-tin (LT) Zirc-4, ZIRLO, and M5. The DEs are being conducted to obtain a baseline of the HBU rods’ condition before dry storage and are focused on understanding overall SNF rod strength and durability. Composite fuel and defueled cladding will be tested to derive material properties. Although the data generated can be used for multiple purposes, one primary goal for obtaining the post-irradiation examination data and the associated measured mechanical properties is to support SNF dry storage licensing and relicensing activities by (1) addressing identified knowledge gaps and (2) enhancing the technical basis for post-storage transportation, handling, and subsequent disposition. This appendix documents the status of the ORNL Phase 1 DE activities related to tests of the sister rods using the Cyclic Integrated Reversible-Bending Fatigue Tester (CIRFT) in Phase 1 of the sister rod test program.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Simplification of Fatigue Test Requirements for Damage Tolerance of Composite Interstage Launch Vehicle Hardware

The issue of fatigue loading of structures composed of composite materials is considered in a requirements document that is currently in place for manned launch vehicles. By taking into account the short life of these parts, coupled with design considerations, it is demonstrated that the necessary coupon level fatigue data collapse to a static case. Data from a literature review of past studies that examined compressive fatigue loading after impact and data generated from this experimental study are presented to support this finding. Damage growth, in the form of infrared thermography, was difficult to detect due to rapid degradation of compressive properties once damage growth initiated. Unrealistically high fatigue amplitudes were needed to fail 5 of 15 specimens before 10,000 cycles were reached. Since a typical vehicle structure, such as the Ares I interstage, only experiences a few cycles near limit load, it is concluded that static compression after impact (CAI) strength data will suffice for most launch vehicle structures.

Nettles, A. T.↗

Thermoacoustic fatigue testing facility for space shuttle thermal protection system

The development of a reusable space shuttle by NASA in the next decade depends in part on the design of a satisfactory thermal protection system (TPS). The booster and orbiter parts of the shuttle require TPS panels which will withstand thermoacoustic fatigue. The Langley Research Center has begun tests on early panel designs in a new acoustic fatigue facility which is capable of simulating the combined elevated temperature and acoustic environments which these panels are expected to experience. The capabilities of the facility and computer system are outlined, and problems encountered in establishing the test methods are discussed. Tests of a Haynes 25 TPS panel are described, and representative data from tests of the panel at 650 C are included.

Rucker, C. E.↗

A data acquisition and control program for axial-torsional fatigue testing

A computer program was developed for data acquisition and control of axial-torsional fatigue experiments. The multitasked, interrupt-driven program was written in Pascal and Assembly. This program is capable of dual-channel control and six-channel data acquisition. It can be utilized to perform inphase and out-of-phase axial-torsional isothermal fatigue or deformation experiments. The program was successfully used to conduct inphase axial-torsional fatigue experiments on 304 stainless steel at room temperature and on Hastelloy X at 800 C. The details of the software and some of the results generated to date are presented.

Kalluri, Sreeramesh↗

A data acquisition and control program for axial-torsional fatigue testing

A computer program was developed for data acquisition and control of axial-torsional fatigue experiments. The multitasked, interrupt-driven program was written in Pascal and Assembly. This program is capable of dual-channel control and six-channel data acquisition. It can be utilized to perform inphase and out-of-phase axial-torsional isothermal fatigue or deformation experiments. The program was successfully used to conduct inphase axial-torsional fatigue experiments on 304 stainless steel at room temperature and on Hastelloy X at 800 C. The details of the software and some of the results generated to date are presented.

Kalluri, Sreeramesh↗

Acquisition and Processing of Passive Thermography Fatigue Test Data

Passive thermography is a large area inspection technique and is commonly used during fatigue loading of composite structures. Passive thermography allows for real time tracking of damage. This provides an accurate assessment of the damage progression as a function of load cycles and determines when the loading is stopped for ultrasonic or X-ray CT evaluations for detail damage assessment through-the-thickness. In addition, if new areas of damage growth are detected, with passive thermography, then those areas are additionally inspected with ultrasound or X-ray CT. A custom developed passive thermography inspection system for fatigue loading is presented. Passive thermography of damage progression is compared to ultrasound inspections as a function of the fatigue cycles. Discussion is made on processing of the thermal data for periodic and non-periodic thermal responses.

Thermal nondestructive evaluation↗

High frequency fatigue testing of Udimet 700 at 1400 F

An investigation pertaining to the development of life prediction methods for materials subjected to high temperature creep/fatigue conditions is presented. High frequency (13.4 kHz) fatigue data were measured at 1400 F on specimens of the nickel-based alloy Udimet 700. Tests were conducted on the virgin material, as well as on specimens which had received prior exposures to high temperature, fatigue, and creep.

Conn, A. F.↗

Flexure fatigue testing of 90 deg graphite/epoxy composites

A great deal of research has been performed characterizing the in-plane fiber-dominated properties, under both static and fatigue loading, of advanced composite materials. To the author's knowledge, no study has been performed to date investigating fatigue characteristics in the transverse direction. This information is important in the design of bonded composite airframe structure where repeated, cyclic out-of-plane bending may occur. Recent tests characterizing skin/stringer debond failures in reinforced composite panels where the dominant loading in the skin is flexure along the edge of the frame indicate failure initiated either in the skin or else the flange, near the flange tip. When failure initiated in the skin, transverse matrix cracks formed in the surface skin ply closest to the flange and either initiated delaminations or created matrix cracks in the next lower ply, which in turn initiated delaminations. When failure initiated in the flanges, transverse cracks formed in the flange angle ply closest to the skin and initiated delamination. In no configuration did failure propagate through the adhesive bond layer. For the examined skin/flange configurations, the maximum transverse tension stress at failure correlates very well with the transverse tension strength of the composites. Transverse tension strength (static) data of graphite epoxy composites have been shown to vary with the volume of material stressed. As the volume of material stressed increased, the strength decreased. A volumetric scaling law based on Weibull statistics can be used to predict the transverse strength measurements. The volume dependence reflects the presence of inherent flaws in the microstructure of the lamina. A similar approach may be taken to determine a volume scale effect on the transverse tension fatigue behavior of graphite/epoxy composites. The objective of this work is to generate transverse tension strength and fatigue S-N characteristics for composite materials using 3-point flexure tests of 90 deg graphite/epoxy specimens. Investigations will include the volume scale effect as well as frequency and span-to-thickness ratio effects. Prior to the start of the experimental study, an analytical study using finite element modeling will be performed to investigate the span-to-thickness effect. The ratio of transverse flexure stress to shear stress will be monitored and its values predicted by the FEM analysis compared with the value obtained using a 'strength of materials' based approach.

Peck, Ann Nancy W.↗

Development and Fatigue Testing of Ceramic Thermal Barrier Coatings

Ceramic thermal barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating thermal fatigue behavior and temperature limit, in order to potentially take full advantage of the current coating capability. In this study, thermal conductivity and cyclic fatigue behaviors of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack initiation and propagation driving forces and failure modes under the cyclic thermal loads will be discussed in light of the high temperature mechanical fatigue and fracture testing results.

Zhu, Dong-Ming↗

Method of measuring elastic strain distribution in specimens used for high frequency fatigue testing

A technique using a point contact piezoelectric detector has been developed which permits the displacement amplitude distributions over the entire length of high frequency fatigue specimens to be measured. Elastic strain distributions can be derived with a computer analysis that uses curve smoothing and numerical derivative methods. The equipment and techniques for measuring and processing the data are described, and displacement amplitudes, strain distributions, and magnification factors for straight rods and dumbbell-shaped specimens are obtained and shown to agree with theoretically predicted values. It is shown that the technique presented here can be used to design specimens with unusual displacement amplitudes and strain distributions.

Sirian, C. R.↗

Multiaxial fatigue low cycle fatigue testing

Multiaxial testing methods are reviewed. Advantages and disadvantages of each type test is discussed. Significant multiaxial data available in the literature is analyzed. The yield theories are compared for multiaxial fatigue analysis.

Zamrik, S. Y.↗

Life prediction of expulsion bladders through fatigue test and fold strain analysis

Cycle life data are presented in terms of true maximum strain for four metals, two plastics, and two elastomers. The Coffin-Manson fatigue theory was applied for metals and plastics, and cut-growth fatigue theory for elastomers. The data are based on measurements made at room and elevated temperatures. It was found that double folds give rise to far severer folding strains than do simple folds. It was also found that, except for the elastomers, all the bladder materials develop surface cracks due to double folds after only one cycle. The findings indicate that metals, which are bets for premeation resistance, are worst for fatigue resistance, and vice versa for elastomers. The intermediate plastics were found to be unsatisfactory for both permeation and fatigue resistance for missions of extended duration.

Chu, H. N.↗