Joseph D. McColskey

Tensile strength and ductility of indium

Abstract The tensile properties of indium were measured at temperatures ranging from 4 to 295 K. Indium recrystallizes during deformation at room temperature and twins during deformation at low temperatures. Strain-hardening characteristics were assessed, using true stress-strain curves, and were found to be similar to soft f.c.c. metals. The logarithm of the flow strength was dependent on temperature. Photomicrographs depicting deformation twinning and slip of indium at 76 and 295 K are discussed.

Low temperature properties of a unidirectionally reinforced epoxy fibreglass composite

The tension, compression and in-plane shear properties of a unidirectionally reinforced fibre/epoxy composite were measured at 295, 76 and 4 K. The composite plate material was produced by the wet-filament winding method. The orthotropic material properties are dominated by the glass fibre properties when measured parallel to the direction of reinforcement, and they are dominated by the epoxy resin matrix properties when measured transverse to the reinforcement. All the values of strength and elastic moduli increased as the test temperature decreased.

Recommended Changes in ASTM Test Methods D2512-82 and G86-84 for Oxygen-Compatibility Mechanical Impact Tests on Metals

A cooperative test program to assess the oxygen compatibility of aluminum-lithium alloys with NASA White Sands Test Facility (WSTF), NASA Marshall Space Flight Center (MSFC), and the National Institute of Standards and Technology (NIST) led to the assessment of the mechanical impact test by NIST. There were substantially different variations in test parameters between the test laboratories; some of these led to significant variability in the actual energy absorbed by the specimens. Therefore, test results varied widely. To reduce the large disparities in interlaboratory test results, a number of changes are recommended in the current ASTM test standards.

REAL‐TIME LOW FREQUENCY IMPEDANCE MEASUREMENTS FOR DETERMINATION OF HYDROGEN CONTENT IN PIPELINE STEEL

The assessment of hydrogen content in pipeline steel is an essential requirement to monitor loss of pipe integrity with time and to prevent failures. The use of pipeline steels of increasing strength significantly reduces the threshold hydrogen concentration for hydrogen cracking. Cathodic protection and corrosion processes both contribute to accumulation of hydrogen as a function of time, which may eventually meet the cracking criteria. New and unique methodologies based on electronic property measurements offer the pipeline industry advanced non‐destructive tools to provide quantified in‐situ hydrogen content measurements in real‐time. The use of low frequency impedance measurements as a non‐contact sensor has been demonstrated for real‐time determination of hydrogen content in coated pipeline steel specimens in the laboratory. Scale‐up to field measurements is in progress, and the development and use of a field sensor are discussed.

Microwave Detection of Stress-Induced Fatigue Cracks in Steel and Potential of Crack Opening Determination Using a New Phase Sensitive Approach Based on a Waveguide Magic Tee

Detection and evaluation of surface cracks in metals is an important facet of nondestructive testing and evaluation (NDTE namely, dominant mode, higher-order mode and open-ended coaxial lines [1–4]. Evaluation of crack properties (crack width, depth, load estimation or other useful information) is the next step in fully determining the threat that a crack may pose to a structure. Surface crack detection, using open-ended rectangular waveguides is primarily based on changes in the phase of the reflection coefficient at the waveguide aperture when a crack is scanned. Therefore, a phase sensitive system may be used for this purpose. The use of a magic tee based approach has the advantage of quick and interactive phase adjustments-adjustments are made immediately by the turn of a knob. In this way optimization is an easy and effective process.

ITER CENTRAL SOLENOID COIL INSULATION QUALIFICATION

An insulation system for ITER Central Solenoid must have sufficiently high electrical and structural strength. Design efforts to bring stresses in the turn and layer insulation within allowables failed. It turned out to be impossible to eliminate high local tensile stresses in the winding pack. When high local stresses can not be designed out, the qualification procedure requires verification of the acceptable structural and electrical strength by testing. We built two 4×4 arrays of the conductor jacket with two options of the CS insulation and subjected the arrays to 1.2 million compressive cycles at 60 MPa and at 76 K. Such conditions simulated stresses in the CS insulation. We performed voltage withstand tests and after end of cycling we measured the breakdown voltages between in the arrays. After that we dissectioned the arrays and studied micro cracks in the insulation. We report details of the specimens’ preparation, test procedures and test results.

Fatigue Crack Growth Rates in Pipeline Steels Using Curved M(T) Specimens

This study presents fatigue data for two different ferrite-pearlite pipeline steels. A fatigue crack growth test for full-thickness curved pipeline samples was developed using a middle tension (M(T)) specimen. Also, finite element analyses (FEAs) were carried out to show the M(T) curvature effects on the fatigue crack growth results. The two steels showed similar fatigue crack growth rate (da/dN) behavior. However, the ferrite-pearlite steel without banding had slightly better fatigue properties than the ferrite-pearlite banded steel. Uncertainty in the fatigue crack growth rates was analyzed by attributing all the fatigue scatter to the Paris law parameter C. The FEA based simulations, based on curved geometries, of the compliance relationship more accurately predicted both fatigue crack growth data and true crack lengths. Nevertheless, the ASTM E647-05 compliance relationship accurately predicted the crack length for the M(T) geometry, although its use leads to slightly conservative fatigue crack growth trends and a slight overestimation of the true final crack length.

Measurement of residual stress in bent pipelines

Buried gas and oil pipelines can be subjected to unexpected bending loads caused by such earth movements as earthquakes, wash-outs, road building, or mining subsidence as well as by denting from unintentional digging. In order to make a fitness-for-service assessment, it is necessary to measure any residual stresses that are left in the pipe wall as well as the degree of plastic flow within regions of severe damage. A portable instrument that uses EMATs to rapidly measure ultrasonic shear wave birefringence in the wall of a pipe has been developed and applied to a 5 m (15 ft) long section of 0.56 m (22 in) diameter linepipe loaded in three point bending by a 22 MN (five million pound) load frame. The results showed that: (1) a large correction for shear wave anisotropy caused by texture in the steel had to be introduced and (2) the degree of plastic flow could be deduced from changes in the texture contribution alone. An attempt to separate the stress and texture effects by using SH wave modes in the pipe...

Deformation and Fracture of Al-Li Alloys in Mechanical-Impact Tests

Mechanical-impact tests in liquid and gaseous oxygen atmospheres aid in the assessment of Al-Li alloys for their use in cryogenic tankage for Advanced Launch Systems. In these tests, a falling plummet-striker pin assembly impacts a small disc specimen. Compressive, radial shear, and tensile (hoop) stresses are imparted to the disc specimens. The combination of these stresses and the high strain rate results in unique deformation and fracture characteristics. These characteristics include adiabatic shear bands, micro-cracking, specimen splitting, specimen heating (local melting), radial deformation in preferred orientations, and shear lips at the specimen-striker pin interface. These deformation and fracture modes are described and compared for various tempers of Al-Li alloys 8090, 2090, 2095, and alloy 2219. Distinctions between the Al-Li alloys and alloy 2219 are discussed.

Large Scale Tests of Composite Support Struts for Superconducting Magnetic Energy Storage Rings

Cold-to-warm struts will be used in superconducting magnet energy storage plants to support the superconducting magnet ring. A prototype design of the structural support struts was tested by simulating the in-service, thermal and mechanical, conditions. The maximum strength measured, with the simulated in-service conditions, was 519 MPa (75 ksi). Problems with the design of the end fittings for the struts prohibited determination of the material’s ultimate strength.