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DOE OSTI2025

Crack Identification and Characterization in Deformed Nb3Sn Rutherford Cable Stacks Using Machine Learning

An investigation of instance segmentation of cracks in Nb3Sn 4-stack 40-strand Rutherford cables using machine learning is presented. Three samples were uniaxially and biaxially loaded before metallographic inspections were performed. The Mask R-CNN model was used in the Detectron2 framework with pre-trained weights but fine-tuned to detect and segment cracks. The model detected cracks with bounding box and mask average precisions (AP) of 42.8 and 27.9, respectively, and was used for instance segmentation of all cracks in the three samples. More cracks were found in the sample pre-loaded along the z-axis (i.e., along the cable length). Pre-loading along the x-axis (i.e., on the cables edges) reduced the number of cracks and changed the crack orientation distribution, away from being highly aligned with the y-axis (i.e., normal to the cables broad faces), i.e., the direction with the highest applied load. Fine-tuning of the Segment Anything Model (SAM) was also studied but performed poorly without human-provided prompts. However, the zero-shot capability of SAM showed high promises to accelerate the image annotation process for applications beyond this study.

Croteau, Jean-Francois↗

DOE OSTI2019

Experimental Relationship Between Compressional Wave Attenuation and Surface Strains in Brittle Rock

Linear ultrasonic testing (LUT) has been extensively used as a tool for the evaluation of damage processes in various materials ranging from synthetic metals to natural geomaterials, such as rocks. A key limitation of LUT-based damage studies to date is the lack of explicit evidence used in associating material damage with the changes in measured LUT attributes (e.g., ultrasonic wave amplitude and velocity). In this study, the evolution of the full-field strains in brittle rock specimens (Lyons sandstone) subjected to failure are analyzed in real time and linked with the changes in the ultrasonic wave amplitude in localized areas illuminated by ultrasonic beams, termed as the ultrasonic image areas. The noncontact optical full-field displacement measurement method of 2-D digital image correlation is implemented in combination with the LUT procedure to continuously track changes in the ultrasonic wave amplitude with the evolution of strains across the surface of the uniaxially loaded intact rock specimens. The ultrasonic amplitude showed near-linear correlation with the intensity of inelastic tensile strain recorded in the rock specimens. The results from the study corroborate that the ultrasonic changes are in fact influenced by the regions of tensile cracking, which is the primary inelastic deformation mechanism in brittle rocks.

15 GEOTHERMAL ENERGY↗

NASA NTRS2001

Consideration of Moving Tooth Load in Gear Crack Propagation Predictions

Robust gear designs consider not only crack initiation, but crack propagation trajectories for a fail-safe design. In actual gear operation, the magnitude as well as the position of the force changes as the gear rotates through the mesh. A study to determine the effect of moving gear tooth load on crack propagation predictions was performed. Two-dimensional analysis of an involute spur gear and three-dimensional analysis of a spiral-bevel pinion gear using the finite element method and boundary element method were studied and compared to experiments. A modified theory for predicting gear crack propagation paths based on the criteria of Erdogan and Sih was investigated. Crack simulation based on calculated stress intensity factors and mixed mode crack angle prediction techniques using a simple static analysis in which the tooth load was located at the highest point of single tooth contact was validated. For three-dimensional analysis, however, the analysis was valid only as long as the crack did not approach the contact region on the tooth.

Lewicki, David G.↗

NASA NTRS1975

Design of structures for optimum geometry

A method is presented for configuration optimization of finite element structures, given a reasonable initial geometry. The objective is to minimize weight or cost. Design variables include geometric as well as member sizing parameters. The number of elements and joints, and the element-joint relationships are prescribed and are not changed during the optimization process. However, the joint locations are changed. The structure is assumed to be linearly elastic and may be statically indeterminate. Multiple loading conditions are allowed. Constraints include limits on stiffness as well as strength. The method is demonstrated with application to truss design, subject to minimum size, strength, buckling, and displacement constraints. Major design improvements are achieved through configurations changes.

Vanderplaats, G. N.↗

DOE OSTI2026

Commercial and Residential Hourly Load Profiles for All Typical Meteorological Year 3 (TMY3) Locations in the United States

One way to achieve grid flexibility is to shed or shift demand to align with changing grid needs. To facilitate this, it is critical to understand how and when energy is used. High-quality end-use load profiles (EULPs) provide this information and can help cities, states, and utilities understand the time-sensitive value of energy efficiency, demand response, and distributed energy resources. Publicly available EULPs have traditionally had limited application because of age and incomplete geographic representation. To help fill this gap, the U.S. Department of Energy funded a 3-year project, End-Use Load Profiles for the U.S. Building Stock, that culminated in this publicly available dataset of calibrated and validated 15-minute-resolution load profiles for all major residential and commercial building types and end uses across all climate regions in the United States. These EULPs were created by calibrating the ResStock and ComStock physics-based building stock models using many different measured datasets, as described in the "Technical Report Documenting Methodology" linked in the submission.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Litter removal impacts on soil biodiversity and eucalypt plantation development in the seasonal tropics

The little layer of tree plantations provides primary nutrients for uptake, buffers changes in soil moisture, and provides habitat and substrate to soil epigeic fauna. However, this layer in eucalypt plantations is often removed to reduce fuel load during the fire season in the Brazilian savanna (Cerrado). Therefore, it is necessary to quantify the effects of changes in litter dynamics on the function of these plantations, on key nutrient cycling processes and on epigeic fauna diversity and abundance. In two adjacent stands (one juvenile and one mature), the consequences of two years of litter removal were quantified as monthly litterfall, leaf and fine wood litter decomposition, epigeic fauna abundance and diversity, soil biogeochemical variables, and tree diameter and basal area increments. Monthly litterfall rates in juvenile and mature stands did not change with litter removal over the study period. Annual litterfall ranged from 4.1 to 4.9 Mg ha -1 a -1 in litter removal plots and from 3.9 to 4.8 Mg ha -1 a -1 in control plots. Fine wood litter decomposition was slower in litter removal plots compared to controls, while leaf decomposition rates were similar in both. Two years of litter removal in the juvenile stand did not affect topsoil biogeochemical parameters but decreased available phosphorus at 20–40 cm depth relative to controls. In the mature stand, total cation exchange capacity (0–20 cm) was higher in controls (6.4 cmol c dm -3 ) relative to litter removal plots (6.3 cmol c dm -3 ), while soil moisture (0–40 cm depth) was lower in litter removal (25.45 m 3 m -3 ) compared to control plots (26 m 3 m -3 ) in the dry season. A non-metric multidimensional scaling ordination revealed an increased homogeneity in epigeic fauna where litter was removed. Litterfall, decomposition, diameter increment, four soil physical parameters and fourteen chemical parameters at 0–20 and 20–40 cm depth explained the differences in soil epigeic fauna composition between litter removal and control plots. Diameter increment decreased with litter removal only in the juvenile stand, which had reached its growth peak. The results indicate that removing excess litter to decrease fuel volume can alter soil biodiversity and edaphic conditions that negatively affect nutrient cycling and tree growth.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2012

Addressing Energy Demand through Demand Response. International Experiences and Practices

Demand response (DR) is a load management tool which provides a cost-effective alternative to traditional supply-side solutions to address the growing demand during times of peak electrical load. According to the US Department of Energy (DOE), demand response reflects “changes in electric usage by end-use customers from their normal consumption patterns in response to changes in the price of electricity over time, or to incentive payments designed to induce lower electricity use at times of high wholesale market prices or when system reliability is jeopardized.” 1 The California Energy Commission (CEC) defines DR as “a reduction in customers’ electricity consumption over a given time interval relative to what would otherwise occur in response to a price signal, other financial incentives, or a reliability signal.” 2 This latter definition is perhaps most reflective of how DR is understood and implemented today in countries such as the US, Canada, and Australia where DR is primarily a dispatchable resource responding to signals from utilities, grid operators, and/or load aggregators (or DR providers).

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

NASA NTRS1999

NASGRO 3.0: A Software for Analyzing Aging Aircraft

Structural integrity analysis of aging aircraft is a critical necessity in view of the increasing numbers of such aircraft in general aviation, the airlines and the military. Efforts are in progress by NASA, the FAA and the DoD to focus attention on aging aircraft safety. The present paper describes the NASGRO software which is well-suited for effectively analyzing the behavior of defects that may be found in aging aircraft. The newly revised Version 3.0 has many features specifically implemented to suit the needs of the aircraft community. The fatigue crack growth computer program NASA/FLAGRO 2.0 was originally developed to analyze space hardware such as the Space Shuttle, the International Space Station and the associated payloads. Due to popular demand, the software was enhanced to suit the needs of the aircraft industry. Major improvements in Version 3.0 are the incorporation of the ability to read aircraft spectra of unlimited size, generation of common aircraft fatigue load blocks, and the incorporation of crack-growth models which include load-interaction effects such as retardation due to overloads and acceleration due to underloads. Five new crack-growth models, viz., generalized Willenborg, modified generalized Willenborg, constant closure model, Walker-Chang model and the deKoning-Newman strip-yield model, have been implemented. To facilitate easier input of geometry, material properties and load spectra, a Windows-style graphical user interface has been developed. Features to quickly change the input and rerun the problem as well as examine the output are incorporated. NASGRO has been organized into three modules, the crack-growth module being the primary one. The other two modules are the boundary element module and the material properties module. The boundary-element module provides the ability to model and analyze complex two-dimensional problems to obtain stresses and stress-intensity factors. The material properties module allows users to store and curve-fit fatigue-crack growth data. On-line help and documentation are provided for each of the modules. In addition to the popular PC windows version, a unix-based X-windows version of NASGRO is also available. A portable C++ class library called WxWindows was used to facilitate cross-platform availability of the software.

Mettu, S. R.↗

NASA NTRS1984

Assessing the Subjective Workload of Directional Orientation Tasks

The impact of various flight-related tasks on the workload imposed by the requirement to compute new headings, course changes, and reciprocal headings was investigated. Eight pilots were presented with a series of heading-change tasks in a laboratory setting. Two levels of difficulty of each of three tasks were presented verbally and spatially. Performance was measured by evaluating the speed and accuracy of the responses. The subjective responses and objective measures of performance reflected a strong association between subjective experience and objective behavior. The reciprocal calculations were performed quickly and accurately throughout and were considered to be minimally loading. Subjective workload, percent correct and response times for the two course-change tasks varied significantly as a function of level of difficulty and display format, with no discernable speed/accuracy trade off.

Miller, R. C.↗

NASA NTRS2008

High-Voltage, Asymmetric-Waveform Generator

The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise leave the fundamental timing signal unchanged. The buffered timing signal would be fed as input to the level shifter. The output of the level shifter would serve as a timing and control signal for the high-voltage switch, causing the switch to alternately be (1) opened, allowing the capacitive load to be charged from a high-voltage DC power supply; then (2) closed to discharge the capacitive load to ground. Hence, the output waveform would closely approximate a series of exponential charging and discharging curves (see Figure 2).

Beegle, Luther W.↗

DOE OSTI2020

Climate Influences on Capacity Expansion Planning with Application to the Western U.S

Electric power system planners utilize a variety of planning tools to inform decisions concerning generation and transmission additions to the electric grid, the need for operational changes, and to evaluate potential stressors on the system. Numerous factors contribute to the planning process including projected fuel and technology costs, policy and load profiles. There is also a growing recognition of the interdependency of the electric grid with other natural and engineered systems. Here we explore how future climate change and hydropower operability might influence decisions related to electricity capacity expansion planning and operations. To do so we assemble a multi-model framework. Specifically, water resource modeling is used to simulate climate impacts on future water supply for thermoelectric and hydropower generation. Separately, temperature impacts on electricity load are evaluated. Together, these climate factors spatially constrain a capacity expansion model that projects generation and transmission additions to the grid. The projected new capacity-builds are then evaluated on their operations, reliability, and cost under average and extreme climate conditions using production cost modeling. This coupled framework is demonstrated on the electric grid in the Western U.S., supporting capacity expansion planning by WECC, the North American Electric Reliability Corporation (NERC) regional entity responsible for reliability assurance of the Western Interconnection. This region was selected in part because the West is unique in that it has high potential for renewable penetrations and is experiencing large retirements/displacements of baseload resources, primarily coal, leading to possible operational challenges in terms of changing resource mix and the need for resource flexibility. Toward this challenge, planning scenarios encompass a range of alternative energy, climate and drought futures. In this context we explore answers to two strategic questions: 1) How does changing climate influence electricity expansion planning (generation and transmission) and future operations, including type and capacity of new builds, system reliability, cost and environmental impacts? 2) How does the representation of hydropower in the modeling framework influence the evaluation of bulk power system operations? Results indicate that climate has a measurable influence on recommendations concerning the capacity, type and location of new generation and transmission additions, with up to 17 GW additional capacity needed by 2038 to meet peak loads (~6.6% increase over capacity-builds based on historical climate). The extent of additional infrastructure needs is strongly influenced by future water availability for hydropower and the potential deployment of demand response technologies. Systems designed for future climate conditions were found to maintain high system reliability under a range of electricity and water availability scenarios (including significant drought), with minimal system curtailments. Additional capacity needs due to higher load tend to increase cumulative 20-year investment and operating costs by $\$$5-$\$$17 billion and generation costs increase by 9 to 19%. Finally, changing the representation of hydropower flexibility has a relatively small influence on capacity expansion in the Western Interconnection through 2038, but hydropower flexibility impacts generation costs to a similar extent as climate.

13 HYDRO ENERGY↗

DOE OSTI2019

Mitigation of flow-induced pressure fluctuations in a Francis turbine operating at the design and partial load regimes-LES simulations

High-fidelity large eddy simulations (LES) were conducted to characterize the spatial and temporal structure of turbulent flows in an industrial-sized Francis turbine while the unit operated at the design point and partial load. A pressure surge with an amplitude of 8% of the turbine head was observed at partial load while the amplitude was<1% at the design point. The vortex rope precession observed in the draft tube correlated to the amplitude and frequency of the pressure surge. Central and peripheral water injections at various volumetric rates were considered to control the flow-induced pressure fluctuations. Central injection at the 4% and 6% flow rates attenuated high amplitude pressure fluctuations by 40% and 75% respectively at partial load. At the same operating conditions, peripheral injections did not have the same desired effect. Although power generation was not changed with water injection at the design point, it was reduced by about 2.5% by central injection and 0.5% by peripheral injection at partial load, showing a water injection mitigation strategy could be applied without any penalty.

Design and partial load regime↗

NASA NTRS1991

Introduction of the M-85 high-speed rotorcraft concept

As a result of studying possible requirements for high-speed rotorcraft and studying many high-speed concepts, a new high-speed rotorcraft concept, designated as M-85, was derived. The M-85 is a helicopter that is reconfigured to a fixed-wing aircraft for high-speed cruise. The concept was derived as an approach to enable smooth, stable conversion between fixed-wing and rotary-wing while retaining hover and low-speed flight characteristics of a low disk loading helicopter. The name, M-85, reflects the high-speed goals of 0.85 Mach number at high altitude. For a high-speed rotorcraft, it is expected that a viable concept must be a cruise-efficient, fixed-wing aircraft so it may be attractive for a multiplicity of missions. It is also expected that a viable high-speed rotorcraft concept must be cruise efficient first and secondly, efficient in hover. What makes the M-85 unique is the large circular hub fairing that is large enough to support the aircraft during conversion between rotary-wind and fixed-wing modes. With the aircraft supported by this hub fairing, the rotor blades can be unloaded during the 100 percent change in rotor rpm. With the blades unloaded, the potential for vibratory loads would be lessened. In cruise, the large circular hub fairing would be part of the lifting system with additional lifting panels deployed for better cruise efficiency. In hover, the circular hub fairing would slightly reduce lift potential and/or decrease hover efficiency of the rotor system. The M-85 concept is described and estimated forward flight performance characteristics are presented in terms of thrust requirements and L/D with airspeed. The forward flight performance characteristics reflect recent completed wind tunnel tests of the wing concept. Also presented is a control system technique that is critical to achieving low oscillatory loads in rotary-wing mode. Hover characteristics, C(sub p) versus C(sub T) from test data, is discussed. Other techniques pertinent to the M-85 concept such as passively controlling inplane vibration during starting and stopping of the rotor system, aircraft control system, and rotor drive technologies are discussed.

Stroub, Robert H.↗

NASA NTRS1992

Introduction of the M-85 high-speed rotorcraft concept

Stroub, Robert H.↗

NASA NTRS1984

Effects of External Loads on Human Head Movement Control Systems

The central and reflexive control strategies underlying movements were elucidated by studying the effects of external loads on human head movement control systems. Some experimental results are presented on dynamic changes weigh the addition of aviation helmet (SPH4) and lead weights (6 kg). Intended time-optimal movements, their dynamics and electromyographic activity of neck muscles in normal movements, and also in movements made with external weights applied to the head were measured. It was observed that, when the external loads were added, the subject went through complex adapting processes and the head movement trajectory and its derivatives reached steady conditions only after transient adapting period. The steady adapted state was reached after 15 to 20 seconds (i.e., 5 to 6 movements).

Nam, M. H.↗

NASA NTRS1927

A load factor formula

The ultimate test of a load factor formula is experience. The chief advantages of a semi rational formula over arbitrary factors are that it fairs in between points of experience and it differentiates according to variables within a type. Structural failure of an airplane apparently safe according to the formula would call for a specific change in the formula. The best class of airplanes with which to check a load factor formula seems to be those which have experienced structural failure. Table I comprises a list of the airplanes which have experienced failure in flight traceable to the wing structure. The load factor by formula is observed to be greater than the designed strength in each case, without a single exception. Table II comprises the load factor by formula with the designed strength of a number of well-known service types. The formula indicates that by far the majority of these have ample structural strength. One case considered here in deriving a suitable formula is that of a heavy load carrier of large size and practically no reserve power.

Miller, Roy G↗

DOE OSTI2022

UAE6 - Wind Tunnel Tests Data - UAE6 - Sequence Q - Raw Data

Sequence Q: Dynamic Inflow (P) This sequence was designed to characterize the dynamic inflow variation using the five-hole probes that extend upwind of the leading edge of the blade. This test sequence used an upwind, rigid turbine with a 0° cone angle. The wind speeds ranged from 5 m/s to 15 m/s, and data were collected at a 0° yaw angle. The rotor rotated at 72 RPM. Blade and probe pressure measurements were collected. The teeter dampers were replaced with rigid links, and these two channels were flagged as not applicable by setting the measured values in the data file to -99999.99 Nm. The teeter link load cell was pretensioned to 40,000 N. The blade pitch angle was changed from the initial tip pitch angle to the final tip pitch angle at the maximum rate of 67°/s. This angle was maintained for the specified delay time duration. Then the blade was pitched back to the initial pitch angle and held for the specified hold time. This was repeated 20 times. The campaign at 15 m/s was aborted early due to excessive low-speed shaft torque loads. The file length varied depending on the time required to obtain 20 pitch cycles for the specified range of angles. The name convention was the standard format, except for the short campaigns collected to ascertain the functionality of the instrumentation. These points were collected at a 3° pitch angle and use the characters REF in the four digits that normally represent yaw angle.

17 WIND ENERGY↗

DOE OSTI2021

Deformation behavior of CP-titanium under strain path changes: Experiment and crystal plasticity modeling

The deformation behavior of commercially pure rolled titanium subjected to strain path changes is studied using experiments and a crystal plasticity model. Four different loading combinations are performed at room temperature to study the activation of slip, twinning, de-twinning and double-twinning in hexagonal closed packed titanium. The strain paths considered are: rolling direction compression (RDC) followed by normal direction compression (NDC), RDC followed by transverse direction compression (TDC), NDC followed by RDC, and NDC followed by TDC. An EBSD-based analysis of the distribution of boundary misorientation angles before and after reload was developed to analyze the evolution of {$10\bar{1}2$} tensile and {$11\bar{2}2$} compression twins. This analysis supports the model results concerning the treatment of twin reorientation. A de-twinning and double-twinning model accounting for back stress effects, an important feature of strain path changes, is implemented within the framework of the visco-plastic self-consistent (VPSC) model along with a dislocation density (DD) based hardening scheme. In the model, plasticity is accommodated by prismatic $\langle$a$\rangle$, basal $\langle$a$\rangle$ and pyramidal $\langle$c+a$\rangle$ slip modes, and {$10\bar{1}2$} tensile and {$11\bar{2}2$} compression twinning modes. The VPSC model predicts the evolution of twinning, de-twinning and double-twinning processes for both tensile and compression twinning modes under strain path change. The model predicts macroscopic stress-strain response, texture evolution, and twin volume fraction that are in agreement with experimental observations. The evolution of texture is investigated in detail by separately analyzing the twinned domains, rather than the evolution of the global texture.

36 MATERIALS SCIENCE↗