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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The effect of electrical current on premature failures and microstructural degradation in bearing steel
Premature failures associated with microstructural degradation, i.e. white etching cracks (WECS), are becoming commonplace as applications are requiring tribological components to operate under extreme conditions. Although the specific drivers of WECs are still debated, the failures are often found in applications where cyclic loading is combined with added energy from stressors such as slip, impacts, or stray current. The aim of the current work is to elucidate effect that variable current has on premature failure. Numerous commercially available lubricants were tested, and both lubricant base oil type and additive package were found to have an effect on WEC failure time.
Explosive welding of aluminium to stainless steel using carbon steel and niobium interlayers
Not Available
Fatigue crack growth resistance of the austenitic stainless steel Alloy 709 at elevated temperatures
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Multimodal Imaging of the Evolving Interface of Irradiated Aluminide-coated Stainless-steel Cladding
Here, we will present recently peer-reviewed results to showcase the advanced multimodal imaging capabilities developed to study irradiated materials at the Pacific Northwest National Laboratory. Irradiated cladding samples selected to support the tritium science and technology program will be used as an example to demonstrate the multimodal imaging capabilities.
Measuring Fatigue Crack Growth Behavior of Ferritic Steels Near Threshold in High Pressure Hydrogen Gas.
Abstract not provided.
Effect of Variables in Welding Technique on the Strength of Direct-current Metal-arc-welded Joints in Aircraft Steel II : Repeated-stress Tests of Joints in SAE 4130 Seamless Steel Tubing
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Effect of Variables in Welding Technique on the Strength of Direct-current Metal-arc-welded Joints in Aircraft Steel I : Static Tension and Bending Fatigue Tests of Joints in SAE 4130 Steel Sheet
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Axial-load fatigue tests on notched and unnotched sheet specimens of 61S-T6 aluminum alloy, annealed 347 stainless steel, and heat-treated 403 stainless steel
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Heat Transfer Tests of a Steel Cylinder Barrel with Aluminum Fins with Improved Bonding Between Steel Barrel and Aluminum Base
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An Electron and X-ray Diffraction Investigation of Surface Changes on Nitrided-steel Piston Rings During Engine Operation in Nitrided-steel Cylinders Barrels
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Increase of the Specific Load Under Tension, Compression, and Buckling of Welded Steel Tubes in Airplane Construction by Suitable Treatment of Structural Steel and by Proper Design
The new construction method indicated, which makes possible a considerably better material utilization and hence a saving in weight, has been tested in a number of Focke-Wulf types also in series production and has fully justified itself.
Linking constituent phase properties to ductility and edge stretchability of two DP 980 steels
Two DP 980 steels were characterized with multiple methods to determine its microstructure characteristics, tensile properties and edge stretchability. The first (DP980-B) is a commercial grade DP980 steel produced by AK Steel, while the second (DP980-T) is a modification of the first one by a tempering process. Both contain two individual phases: ferrite and martensite with body centered cubic (BCC) and tetragonal (BCT) crystal structure respectively. ASTM standard tensile tests were performed for both materials, revealing that DP980-B has higher work hardening and larger total elongation than DP980-T. Standard hole piercing and subsequent hole expansion and extrusion tests were also performed. The critical hole expansion ratio (HER) of hole pierced sheet at different nominal clearances, on the other hand, show an opposite trend: the HER of DP980-T almost doubles that of DP980-B. This indicates the tensile ductility and edge stretchability are determined by different mechanisms due to different deformation modes. The ductility of sheet metal during uniaxial tension is determined by deformation instability, i.e. necking, due to less constraint at the region of deformation and fracture will occur quickly after necking. The contribution of post-necking deformation to the total elongation is insignificant for the high strength grades such as DP980 steels. The ductility during hole-expansion, however, is mainly determined by material fracture behavior that is dependent on phase property disparity and material intrinsic fracture parameters. With the individual phase properties for both DP steels determined by in situ tensile tests under high energy X-ray diffraction, the results show that DP980-T steel has lower property disparities between the two phases than DP980-B steel, due to the tempering process. This explains why the DP980-T steel has higher HER than DP980-B steel: lower phase disparity will lead to less local deformation during loading. The higher work hardening rate for DP980-B steel contributes to its higher uniform elongation compared with DP980-T steel based on the maximum load condition of deformation instability. An integrated finite element simulation framework for studying hole expansion is also presented here, based on the calculated individual phase properties from the combined high energy x-ray diffraction (HEXRD) and elastic plastic self-consistent modeling. The simulation results correlate well with the experimental results on the HER difference between the two materials.