bluuebunny/crossref_metadata_2025 huggingface dataset:
Alternative Nozzle Reinforcement Rules for Gasketed Plate Heat Exchangers
Authors: Nikic Milan , Srnic Djordje
Published: October 2021

This paper aims to provide an alternative design approach to the current nozzle reinforcement rules for gasketed plate heat exchangers (GPHE) designed in accordance with Appendix 45 of ASME BPVC Section VIII, Div. 1. The current ASME BPVC Section VIII, Div. 1 nozzle reinforcement rules require the use of bending stress calculated at the center of the GPHE end plate where the bending stress has the highest value. Typical GPHE’s have inlet and outlet nozzles located near the top or bottom of the GPHE end plates where the bending stresses are lower as compared to the bending stresses at the center of the plates. For nozzle reinforcement analysis in GPHE end plates, this alternative design approach suggests utilizing the bending stress values calculated in vicinity of nozzles in lieu of bending stress value at center of the end plate. It also suggests utilizing the modified UG-39 rules for GPHE end plate nozzle reinforcement. In order to optimize the design thickness of the GPHE end plates, this paper will analyze the impact of nozzle size and location on bending stresses in the end plates, propose modification of UG-39 rules for GPHE end plates, and to define the limits of the design approach.
Coupling of Neutron Noise and Dynamic Finite Element Analyses to Perform Remote Condition Monitoring for Reactor Vessel Internals
Authors: Banyay Gregory A. , Palamara Matthew J. , Smith Stephen D.
Published: October 2021

During a Spring 2019 refueling outage, Plant A, a pressurized water reactor (PWR), experienced difficulty removing the reactor vessel upper internals because of degraded thermal shield (TS) support block bolts (TSSBBs), TS flexures, and baffle-former bolts (BFBs). None of the degradation was expected based on prior industry operating experience. Dynamic finite element analyses (FEA) and neutron noise monitoring were performed to diagnose the degraded condition. The FEA simulated the indications from the 2019 outage to assess the effect that degradation would have on the dynamic response of the lower reactor vessel internals. In parallel, neutron noise data was collected and evaluated to characterize the vibratory signature of the Plant A lower internals. The results of the FEA and neutron noise monitoring were coupled to compare degradation scenarios with the measured data, and it was thus predicted that multiple non-functional (fully failed) flexures existed at Plant A. Those predictions were subsequently validated during the Fall 2020 outage.

This use of neutron noise to detect and diagnose degradation represents the practice of proactive structural health monitoring (SHM) for reactor vessel internals. This remote condition monitoring and diagnostic computational framework is currently being enhanced by quantifying the sensitivity of the structural dynamics to different degradation scenarios. This methodology leverages benchmarked FEA models and machine learning methods to enhance interpretability of neutron noise results and proactively diagnose different degradation scenarios, thus enabling prognostic asset management for reactor structures.
Finite Element Analysis to Investigate the Effect of Geometries of DWTT Specimens on the CTOA - An Interim Report
Authors: Xue J. , Williams B. , Xu S. , Tyson W. R.
Published: October 2021

This work forms part of the research effort to investigate the transferability of CTOA from standard DWTT specimens to other geometries, notably pipes. The focus of this work is on the effect of ligament size and thickness of DWTT specimens under bending load on CTOA. The damage mechanics models used in this work, namely the modified Xue-Wierzbicki (XW) model and the Modified Mohr-Coulomb (MMC) model, utilize fracture criteria that depend on stress state, i.e., stress triaxiality and Lode angle. Both the XW model and the MMC model predict similar trends regarding the effect of ligament size and thickness on CTOA. For both the standard and large DWTT models with various thicknesses investigated in this research, steady-state crack growth was achieved at a small crack extension of about one specimen thickness. The CTOA values measured on the surface are larger than those measured in the interior, which is consistent with experimental observation. Increase of thickness has negligible effect on interior CTOA, but leads to higher surface CTOA. Increase of width (ligament) decreases CTOA slightly. However, further work is needed on the models because not all features are correctly predicted. In particular, the fracture mode is predicted by the models to show increasing slant fracture with increasing thickness, contrary to expectation. Also, the effect of ligament size on CTOA in tension-loaded specimens should be investigated to assess transferability to pipe in which the loading is tensile.
A Method for Investigating Multi-Axial Fatigue in a PWR Environment
Authors: Gill Peter , Onwuarolu Paul , Smith Russell , Coult Ben , Kirkham Mark , Sutcliffe Matt , Cooper Karen , Schofield Tom , Madew Colin , McLennan Alec , Currie Chris
Published: October 2021

A significant amount of fatigue testing has taken place over the years to generate relationships between applied stress or strain range and cycles to failure. This has mainly been conducted on uniaxial test specimens in an air environment. More recently, fatigue testing has been conducted in a PWR environment as it is now well known that this has a deleterious impact on life. The test method presented in this paper considers bi-axial loading on a specimen that is compatible with PWR fatigue testing rigs. In order to achieve this, a specimen was designed to convert a uniaxial load into a biaxial load with no internal mechanism. Finite Element Analysis (FEA) was conducted to develop and refine the design, which accounted for frictional contact and bolt up stresses.

Initial testing was conducted on a 304L stainless steel specimen in a room temperature air environment. Digital Image Correlation (DIC) was used to validate the FEA and there was excellent agreement between predicted and observed strains. Once the strains were validated, a fatigue test was conducted to confirm that cracking was in the expected location, and that the number of cycles to failure was reasonable. Direct Current Potential Drop (DCPD) was used to indicate when a fatigue crack initiated, which was confirmed by visual inspection. The results showed that cracking occurred in the location of highest accumulated plastic strain and Von Mises Stress, and the number of cycles to failure was slightly lower than predicted but still within scatter.
Modeling of Plastic Zones and Fracture Paths in Representative Material Elements With Bulk Hydrides in Hydrided Irradiated Zr-2.5Nb Pressure Tube Materials Under Plane Strain Conditions
Authors: Wu Shengjia , Pan Jwo , Scarth Douglas A.
Published: October 2021

Plastic zones near bulk hydrides and fracture paths in representative volume elements (RVEs) with bulk hydrides in hydrided irradiated Zr-2.5Nb pressure tube materials are investigated by two-dimensional finite element analyses under plane strain conditions. Three RVEs with different distributions of bulk hydrides are selected from the micrographs of the radial-circumferential cross section of a hydrided irradiated Zr-2.5Nb pressure tube specimen. The bulk hydrides are assumed to be separated from the pressure tube material in the early stage of the loading and are assumed as cracks. The RVEs are subjected to high stress triaxiality loading conditions similar to those ahead of the front of an axial crack in a pressure tube specimen under internal pressure. The elastic-plastic stress-strain relation for the matrix materials in the RVEs follows that of a tensile test of a transverse tensile specimen cut from an irradiated Zr-2.5Nb pressure tube specimen. The computational results indicate that due to close proximity of bulk hydrides, narrow plastic zones emanating from the tips of bulk hydrides connect either to the tips of other neighboring bulk hydrides or to the neighboring fractured bulk hydride surfaces as the loading increases. Possible fracture paths are identified and presented by connecting the fractured bulk hydrides and the narrow plastic zones emanating from the tips of bulk hydrides. The features of the fracture surfaces of the RVEs based on these possible fracture paths are generally consistent with those ahead of the front of a crack in a curved compact tension specimen cut from a hydrided irradiated Zr-2.5Nb pressure tube specimen. The computational results also show that the macroscopic elastic modulus and maximum stress of the RVE increase as the net section percentage of the possible fracture path increases.
Self-Loosening Behavior of the Nut Due to Tension Change Considering the Inclination of Bearing Surface
Authors: Shoji Yasumasa
Published: October 2021

Self-loosening behavior is a topic which many researchers are tackling and the principle is coming clearer. Self-loosening occurs mainly when transverse load is applied to the bolt/nut system and the loosening also occurs when such other loads are applied as impact of the bolt (NAS3350 test type) or temperature difference between bolt and nut. The author reproduced the phenomena by using finite element analyses and found the self-loosening is caused by radial relative displacement between bolt and nut threads. On the other hand, some researchers say the self-loosening occur when the tension changes repeatedly while others say it doesn’t. This axial force phenomenon is not yet clear even in experiment. In this paper, the self-loosening phenomenon by the tension change is examined using Finite Element Analyses. The results show that the self-loosening depends on the inclination of the bearing surface. The loosening does not occur when the inclination of the bearing surface is small enough and it occurs when the inclination is large. As the inclination of the bolt head and nut is allowed within the engineering tolerance and flanges rotate when it fastened making the bolt head or nut bearing surface inclination, the self-loosening may happen for any bolts in nature if tension changes repeatedly.
Three-Dimensional Finite Element Analyses of Separation Work Rate For Crack Extension in a Thin Curved Compact Tension Specimen With Finite Step Nodal Release Method
Authors: Sung Shin-Jang , Wu Shengjia , Pan Jwo
Published: October 2021

Separation work rate as a function of the crack extension in a thin curved compact tension (CCT) specimen of Zr-2.5Nb pressure tube material is investigated by three-dimensional finite element analyses with the finite step nodal release method. The straight crack front for the crack extension is assumed. The crack extension is simulated by releasing the nodal points ahead of the initial straight fatigue crack front in the CCT specimen. The crack extension follows the available experimental crack extension-displacement data. The computational results show that the plastic zone size and shape change along the crack front as the crack extension increases. The computational results also show that the separation work rate is a function of the crack extension and is similar to the experimental J-R curve. The computational results suggest that in a two-dimensional finite element analysis of the crack extension in the thin CCT specimen with the cohesive energy approach, the cohesive energy can vary to account for the change of the constraint conditions along the crack front as the plastic zone size increases with the crack extension.
The Aeroacoustic Response of a Single Square Cylinder in Confined Cross Flow
Authors: Shaaban Mahmoud , Mohany Atef
Published: October 2021

Unstable flow patterns around arrangements of bluff bodies in different engineering applications can give rise to pressure oscillations, leading to excitation of strong acoustic resonance that can interrupt operation. In certain conditions, flow fluctuations arising from vortex shedding downstream of a circular cylinder are reported to excite severe acoustic resonance. On the other hand, cylinders of a square cross section are known to be particularly susceptible to mechanisms that involve coupling between the flow and a structural mode. It is not documented, however, if such coupling would occur between an acoustic mode and flow fluctuations downstream of a square cylinder. In this work, the possibility of excitation of acoustic resonance due to coupling between unsteady flow downstream of a single square cylinder with an acoustic cross mode of a rectangular duct is experimentally investigated. During the experiments, acoustic resonance was self-excited. Measurements of the acoustic pressure and the flow velocity are carried out for a single square cylinder of an edge length of 25.4 mm. Results show that aeroacoustic response characteristics for this configuration are not completely analogous to the case of a circular cylinder, with a number of features not reported before. A brief summary of the results is presented in this work.
Analysis of Test Method to Extract Material Properties From Candu Fuel Channel Spacers Made of Helical Springs
Authors: Metzger Donald , Gagnon Andre , Kashyap Tejasvi
Published: October 2021

In a particular nuclear application, separation between two concentric tubes is supported by helical springs installed in the annular space. Evaluation of material degradation due to the unique operating environment requires testing of ex-service spring material. Testing is done by compressing short segments of the spring material between two surfaces as per the loading mode in operation. Nominally, the specimen behaves like multiple rings loaded uniformly in parallel, but analysis of test results based on this approximation neglects significant end effects.

A detailed analysis addresses the transition from the free end boundary condition through to where the coils become confined by friction to behave like rings. The thin ring solution is compared with finite element results as well as test results. Trends from the detailed thin ring solution correspond closely to the finite element and test results. A more precise relationship between the total applied load and the maximum stress in the material is determined.
Comparison of Ni-Steel Dissimilar Joints for Coke Drum External Weld Repairs Based on Isothermal Low-Cycle Fatigue Tests
Authors: Zhang Shutong , Romo Sebastian , Giorjao Rafael Arthur , Penso Jorge , Guo Haixia , Yuen Simon , Ely Lisa , Ramirez Antonio J.
Published: October 2021

Low-cycle fatigue failure has been widely accepted as the key mechanism causing damages of coke drums during cyclic thermal-mechanical loadings. Common damages of coke drums known as bulging and cracking are associated with accumulative plasticity caused by thermal and mechanical strains. External repairs using temper-bead welding techniques are implemented to repair welds in the damaged areas of coke drums, which provide structural support to the vessels. Compared with matching filler metals, Ni-base fillers including alloy 625 and alloy 182 are compatible with both low-alloy steel base metal and internal clads in terms of weldability and thermal expansion. However, the differences of yield strengths and cyclic hardening behaviors of nickel-base alloys from base metals compromise the fatigue resistances of weld joints. In this study, alloy 182 and alloy 625 repair coupons were evaluated and compared based on isothermal low-cycle fatigue tests. Low-cycle fatigue behaviors of both weld metals and 1.25Cr-0.5Mo base metal were measured at 1.0%, 1.5% and 2.0% strain amplitudes. Test results indicate both nickel-base filler metals exhibit overmatching strength over the base metal due to cyclic hardening. Low-cycle fatigue tests of Heat Affected zone (HAZ) samples show the failures of alloy 625 weld joints occur in the base metal, while the failures of alloy 182 weld joints occur along the fusion boundary. The observations show strength mismatch and fatigue resistance are the key factors to determine failure locations of the joints. In addition, cyclic hardening coefficients based on kinematic hardening model were extracted from experimental data to simulate the cyclic behaviors of the weld joints. Finite element simulation results were shown to be consistent with experimental data at stabilized cycles. Cyclic behaviors of weld metal and base metal within a weld transition sample were calculated based on the numerical model.
Evaluation of Cracks Embedded in Zones With Large Scale Plasticity in Subsea HPHT Equipment – Comparing FAD and Driving Force Approaches
Authors: Kulkarni Mandar , Lopez Carlos , Kluk Daniel , Chappell John
Published: October 2021

Fracture mechanics assessments for pressure vessels are performed to determine critical flaw sizes and/or estimate the fatigue life of a growing crack as a means of establishing inspection intervals for the equipment. In most cases the evaluation is performed based on methods described in API 579-1/ASME FFS-1 and BS7910. The approaches described in these standards are mostly based on a linear elastic fracture mechanics approach. Even though plasticity can be accounted for by using a failure assessment diagram (FAD); however, even with this approach the effect of plastic strain around the crack is not explicitly considered.

This paper presents an approach as per API 579, Annex 9G.5 which recommends utilizing a driving force method whereby the J-integral is directly evaluated from an elastic-plastic finite element model. The main goal is to study differences between the FAD approach against the elastic-plastic J-integral approach wherein the crack is modeled explicitly. Simplified representative geometries are considered for this study. Two scenarios for the plastic zone are considered a) crack present during initial loading with no residual plastic strain and b) crack in a residual stress zone. Different crack sizes are considered for this comparison study ranging from small cracks completely embedded within the plastic region and larger cracks with partial embedment.

The paper presents comparison studies which highlight the key differences between different analysis approaches with the aim of identifying the most conservative assessment method for different crack geometries.
Numerical Prediction of the Phase Difference in Tube Bundles Experiencing Streamwise Fluidelastic Instability
Authors: Rehman Sameer A. , Hassan Marwan , El Bouzidi Salim , Weaver David , Elbanhawy Osama
Published: October 2021

Recent experimental investigations have shown that tube arrays can become unstable in the streamwise direction. This is contrary to the long-held notion that fluidelastic instability is only a concern in the direction transverse to the flow. The possibility of streamwise fluidelastic instability (FEI) as a potential threat to the integrity of tube bundles was confirmed by the recent failures of newly installed replacement steam generators. A number of investigations were conducted to uncover the nature of this mechanism. A theoretical framework was developed by Hassan and Weaver [1] to model streamwise fluidelastic instability in a bundle of flexible tubes. The model utilized a simple time lag expression for the flow channel area perturbation. The current work aims at developing a numerical model to precisely predict the flow perturbation characteristics in a tube bundle due to streamwise tube motion. Flow simulations were carried out for single phase fluid flow in a parallel triangle tube bundle array with 1.2, 1.5 and 1.7 pitch to diameter ratios. The numerical model was benchmarked against numerical and experimental results available in the FEI literature. Simulations were carried out for a range of reduced flow velocities. The model results showed that the upstream flow perturbation magnitude and phase are different from those obtained in the downstream of the moving tube. The obtained flow perturbation characteristics were implemented in the Hassan and Weaver [1] model and the streamwise FEI threshold was predicted.
Comparison of Candidate Steady Loading Elevated Temperature Design-by-Analysis Methods
Authors: Dewees David , Mann J. Adin , Nadarajah Chithranjan , Messner Mark , Hantz Ben , Andersen David
Published: October 2021

Design-by-Analysis is distinguished from Design-by-Formula or Design-by-Rule in that specific failure modes are identified, and detailed analysis of each failure mode is compared to criteria specific to each failure mode. Several ASME Boiler and Pressure Vessel code committees continue to work on design-by-analysis methods in the elevated temperature range, where creep rupture is a failure mode with steady loading. The Subgroup on Elevated Temperature Design, which reports to Section I and Section VIII and collaborates with Section III, has been evaluating eight different analysis methods for six example problems. The two Design-by-Formula methods are from Section I and Section VIII Division 1 and the Design-by-Analysis methods are (1) Linear Elastic Analysis with revised stress limits, (2) Isochronous Curve Limit Load, (3) STP-PT-070 Limit Load Analysis, (4) Detailed Inelastic Methods using the MPC Omega creep models, (5) ASME CC2843 (simplified NH method),and (6) Section III Division 5 Draft Code Case for Limit Load Analysis. The test cases include (1) Grade 11 Steam Outlet Header, (2) Grade 91 Header Endplate, (3) Grade 91 Steam Outlet Header, (4) Grade 91 Steam outlet Header 2, (5) Grade 91 Steam Piping Lateral and (6) Type 304 Stainless Spherical Vessel/Nozzle. To ensure a common comparison, a common material definition was used based on the ASME FFS-1/API579 material models. Each of the analysis methods and examples will be described along with a comparison of the maximum pressure predicted by each method for each problem.
A Comparative Study of Radial Nozzle Criteria; Section VIII, Division 2, Part 4.5.5 to Part 5.2.2
Authors: Boyak Craig
Published: October 2021

A study is presented which compares nozzle thickness requirements based ASME Section VIII, Division 2, Parts 4 and 5[1]. Specifically, the simplified geometry of a set-in, radial nozzle without inward projection or repad is considered. The comparative technique considers a design pressure at the capacity of the shell and identifies the minimum nozzle thickness that satisfies applicable stress limits. For Part 4, the methodology of 4.5.5 is used. For Part 5, the elastic method in 5.2.2 is used. The study employs these techniques for R/t geometries of 20 to 180 and d/D ratios of 0.01 to 0.3. The comparison indicates elastic analysis Part 5 methods can improve the design from that of Part 4 over some, but not all, configurations within the study’s scope. The bounds of where the elastic analysis Part 5 methods benefit are identified. In the process of the study’s effort, numerous responses are identified and compared between design methodologies. The comparison is one of needed nozzle thickness for similar geometries. Behavior responses are shown from the range of configurations in the large simulation set created by the Part 5 method. For the Part 4 response, charts are shown that identify the required nozzle thickness based on the varying reinforcing limit logic employed in that method.
Comparison of Valve Failure Rates Estimated From Field Failure Data to Those Predicted by Calibrated FMEDA
Authors: Bukowski Julia V. , Goble William M. , Harris Stephen P.
Published: October 2021

This paper presents the results of three comparative studies. In each study the failure rate of one specific valve at one specific facility is estimated from field failure data (FFD). Each estimate is compared to the failure rate predicted for that valve by the Calibrated FMEDA™ technique. The predicted failure rates consider the failure rate variations due to valve application, to fluid service, and to each specific facility’s Site Safety Index (SSI) which accounts for various aspects of safety culture. The results show that the predictions are quite good, i.e., all predictions lie within a 70% confidence interval constructed from each valve’s FFD and near the estimated mean failure rate for each valve.
Development and Characterization of Shape Memory Polymers for Non-Invasive Biomedical Applications
Authors: Jeewantha Janitha , Emmanuel Chris , Herath Madhubhashitha , Islam Mainul , Epaarachchi Jayantha
Published: October 2021

This paper details a shape memory polymer (SMP) synthesis and characterization process has been undertaken to develop a bio-medical material for fabricating non-invasive custom prosthetic components and orthosis devices. The glass transition temperature of a one-way SMP epoxy is tailored for external biomedical applications since human skin is sensitive to high temperature (> 45°C). The key shape memory properties of shape fixity ratio, shape recovery ratio and shape retention properties were comprehensively analyzed, and thermomechanical properties were verified. SMPs can be customized for the purpose; thus, SMP prosthetic and orthosis devices will be ideal for first aid and emergency treatments until proper medical attention is received. Finally, brief details of an SMP bone immobilization casting method are provided to explain the application further.
Voltage-Dependent Medium-Term Synaptic Plasticity in Biomolecular Synapses
Authors: Maraj Joshua J. , Ringley Jessie D. , Sarles Stephen A.
Published: October 2021

Biomolecular assemblies of phospholipids and the pore forming species monazomycin were constructed using the droplet interface bilayer technique to mimic synaptic properties. Electrical characterization of the interface confirms the existence of multiple forms of short-term synaptic plasticity in response to constant stimuli. Memory of prior stimulation can last up to 20 minutes suggesting an unaccounted mechanism of longer term memory retention, termed “medium-term synaptic plasticity.” Monazomycin doped biomembranes were stimulated by a series of step voltage inputs with varying off-times ranging from one to twenty minutes. Percentage of peak current obtained inactivation percentage, and change in inactivation percentage were compared. Peak current is reduced in subsequent stimulations and gradually restores back to 100% after 20 minutes. Inactivation percentage is also reduced but recovers at 20 minutes. Initial current right after application increases and remains elevated up to 20 minutes. Multiple sinusoidal voltage inputs were performed with −80 mV step inputs in between. I-V hysteresis for these inputs were compared. The peak negative current of the hysteresis decreased while the positive peak increased after each cycle. Medium term synaptic plasticity is believed to be the result of lingering concentration differences at the interfaces and lingering presence of nonconducting monazomycin in the bilayer.
Characterization of Nanoporous Polyvinylidene Fluoride (PVDF) Sensors Under Tensile Loading
Authors: Gao Zhaolin , Danley Matthew J. , Kloster Jack T. , Lai Victor K. , Zhao Ping
Published: October 2021

A Polyvinylidene Fluoride (PVDF) sensor with integrating nanoporous structures was developed and fabricated to improve its piezoelectric effect. The sensor samples with different porosities ranging from 3.3% to 42.0% were made. The porosity effect on the piezoelectric coefficient d31 of the sensors was studied under tensile loading. The results showed that the d31 value increased from ∼21.3 pC/N to ∼51.3 pC/N as the porosity increased from 3.3% to 23.7%. With a further increase in porosity, the d31 value had a considerable declining trend. The optimal porosity value was determined to be 23.7% as the sensor exhibited the strongest piezoelectric effect at this point. Meanwhile, a cyclic load was applied to the sensors to investigate their sensing effect and the results indicated that the sensors can properly detect a dynamic load ranging from 0 to 10 N. It was also found that the voltage output produced from the sensors significantly changed with the porosity and the sensor with 23.7% porosity showed the best sensing performance, which was in an agreement with the piezoelectric coefficient d31.
Feature Generation and Selection for Identification of Damage in Thin-Walled Structures Based on a Statistical Approach
Authors: Sattarifar Afshin , Nestorović Tamara
Published: October 2021

Ultrasonic guided waves are recognized as one of the promising approaches to detect damage in the structures. Furthermore, machine learning algorithms with their distinguished capability in recognizing and classifying the patterns in a dataset can be employed as an extension to conventional damage detection techniques. In the current study, a damage detection framework is proposed, which is based on the result of the numerical simulation of wave propagation in an aluminum plate. The feature vector required for the training of the classifiers is generated by employing statistical analysis of the time domain signals as well as their Hilbert transform. This study shows the importance of the selection of the right combination of the features for the classification of the state of the structure. The result of this study contributes to devising a more automated and generalized process for damages detection in metallic structures.
Design of a Bio-Inspired Soft Robot for Break Bulk Manipulation in Transport Engineering
Authors: Bui Duc Trung Tin , Jovanova Jovana
Published: October 2021

This research explores the possibility of upscaling bio-inspired designed soft robots in transport engineering application with the focus on grabbing and manipulating break bulk such as windmill blades or rolls of steel. Upscaling current state soft robotic systems includes challenges regarding the structural strength of the robot. Also certain actuation methods could be affected by upscaling the actuators as well. The design of the proposed bio-inspired soft robot is determined by analysing the functions and constraints of the design as well as evaluating different types of gripping solutions based on the different types of shapes of the object. In this research the claw gripping is selected to be applied in break bulk manipulation. This gripping solution could potentially be combined with the vacuum gripping solution to be able to manipulate more types of objects. The three fingers of the claw are designed based on the trunk of an elephant as the trunk of an elephant can lift heavy loads and can therefore be seen as a good starting point to design a high load capacity gripper.
A Translation-to-Rotation Converter for Scavenging Energy From Human Walking
Authors: Pan Qiqi , Wang Biao , Zhang Lingling , Yang Zhengbao
Published: October 2021

Human motion is a rich source of energy. However, the ultra-low frequency and the irregular feature of the motion make the above prospects still far from being effective. In this work, we present a translation-to-rotation converter for energy harvesting during human walking. We here propose the harvester that enables conversion of low-frequency translational vibration to high-speed rotations and further generates electricity via the electromagnetic effect. The transducer is composed of an internal thread sleeve, an external thread driving shaft, a spring, a gearbox, and a limit frame. Our design features low cost, low fabrication difficulty, and high power density. Experiments conducted under pseudo-walking conditions confirmed that the stiffness of the spring and the pitch of the sleeve are the two key parameters for the performance of the harvester. The harvester mounts in a shoe heel and engages power generation in the whole gait cycle. Test subjects walking with one device with optimal spring stiffness on each shoe produce a peak power of 3.7 watts at a pace frequency of 1 Hz, which is about one magnitude higher than that of shoe-mounted devices under pseudo-walking excitation. Moreover, the proposed device could open an alternative pathway for powering smart wearable or portable electronics.
The Effect of Sensitivity Matrix Formulation on Damage Detection in Carbon Fiber Composites With Surface-Mounted Electrodes via Electrical Impedance Tomography
Authors: Sannamani M. , Tallman T. N.
Published: October 2021

Carbon fiber reinforced polymers (CFRPs) are valued in aerospace and other weight-conscious applications for their high strength-to-weight ratio. However, with the adoption of these lightweight materials emerges challenges not seen in traditional monolithic materials such as complex internal (i.e. outwardly invisible) damages like delamination or fiber failure in the structure. Robust methods of damage detection and health monitoring are therefore important. It is also desirable to utilize an intrinsic property of these materials, such as electrical conductivity, as an indicator of damage to render the material as self-sensing. Electrical impedance tomography (EIT) has been widely explored for damage detection and health monitoring in self-sensing materials. To date, however, studies involving EIT have been largely limited to materials with less electrical anisotropy than is seen in CFRPs and using only edge-placed electrodes (e.g. electrodes placed on the edges of a plate). These limitations are important because the inability to handle highly electrically anisotropic materials precludes EIT from a great number of existent CFRP structures. Furthermore, many real structures lack well-defined edges on which electrodes can be placed. In this paper, we tackle these challenges by presenting a preliminary study into the role of EIT sensitivity matrix formulation and surface-mounted electrodes on damage detection and localization in CFRPs. In our approach, the conductivity is modeled as being anisotropic, and the sensitivity matrix is formed using three methods — with respect to a scalar multiple of the conductivity tensor, the out-of-plane conductivity, and the in-plane conductivity. It was found that through-hole damage can be adeptly identified using the combination of surface-mounted electrodes and a sensitivity matrix formed with respect to either a scalar multiple of the conductivity tensor or the in-plane conductivity. The findings presented in this work take an important step towards translating EIT out of the laboratory and into real applications on CFRPs.
A Novel Design of Broadband Piezoelectric Vibration Energy Harvester With Cross-Coupled L-Shaped Structure
Authors: Sun Shilong , Zheng Yulong , Zhang Xiao
Published: October 2021

The piezoelectric vibration energy harvester can collect energy from the ambient vibration. The vibrations from the environment are usually random and also from various directions. The current energy harvester cannot efficiently collect the energy from vibration and also the energy transfer efficiency is very low, and the bandwidth is limited. Therefore, this paper proposed a novel cross-coupled L-shaped piezoelectric vibration energy harvester (CL-PVEH) to solve the low efficiency and narrow bandwidth. This structure consists of a vertical beam and a horizontal beam joint crosswise to complete a multi-directional energy harvester. The finite element analysis (FEA) and analytical study are performed in comparison that the ability of energy conversion efficiency for the cross-coupled and traditional L-shaped structures. The results demonstrate that the CL-PVEH can harness energy effectively under excitations from three perpendicular directions while the TL-PVEH can harness energy under excitation from only two directions effectively. Meanwhile, the CL-PVEH can generate three output peaks under a frequency range of 10Hz–100Hz, which are 18.8Hz, 24.8Hz, and 91.5Hz under multi-directional excitations. The multiple natural resonance frequencies under different direction excitations display that the CL-PVEH has a great ability of broadband energy harvesting and can be more flexible in mechanical structure health and human health status monitoring, especially in complex and multi-directional vibrational environment.
A Nonlinear Piezoelectric Energy Harvester With Auxetic Structures
Authors: Chen Keyu , Gao Qiang , Fang Shitong , Zou Donglin , Yang Zhengbao , Liao Wei-Hsin
Published: October 2021

In this paper, we design and experimentally validate an auxetic nonlinear piezoelectric energy harvester. This harvester combines a clamp-clamp beam and auxetic structures, which can improve the efficiency and bandwidth of the energy harvesting based on a pure mechanical structure without outer magnets or stoppers. Finite element analysis is performed to analyse the effects of the auxetic structures on the efficiency and nonlinearity of the energy harvester. The lumped parameter model is utilized to predict the performance of the energy harvester, which well matches the experimental results. In the experimental validation, under 0.1g base excitation, the power output of the two types of auxetic energy harvesters is 173% and 94% higher than the conventional nonlinear energy harvester. Besides, the bandwidths of the two types of auxetic energy harvesters are broadened by 1556% and 2142% compared with the linear systems.
Unit Cell Optimization of Polymer Filled Honeycomb Composites
Authors: Squibb Carson , Philen Michael
Published: October 2021

Hexagonal honeycombs and their use in composite structures has become commonplace in aerospace design and other fields. Polymer-filled honeycomb structures, where the hexagonal cells are filled with an elastomer, are of interest for their ability to increase the stiffness of the composite over that of the elastomer or honeycomb individually. Previous research by the authors has demonstrated that the effective behavior of such composites is determined by both the honeycomb geometry as well as the material properties of the infill and cell wall. Infill stiffness amplifications of over three orders of magnitude have been predicted, which could be an attractive option for improving the performance of smart materials such as shape memory polymers. Considering the benefits of such composites, it is of interest to optimize the honeycomb cell geometry to maximize the stiffness increase observed in the infill material. To meet this objective, in this work a unit cell finite element model was created for a hexagonal, thin walled honeycomb. Six design variables describing the honeycomb geometry were selected, and parametric studies of these design variables in the objective have been generated. Informed by these studies, an estimation of the Pareto front has been completed, with chosen objectives of the maximum composite in-plane modulus and modulus ratio, in one material direction. Promising designs are identified, and the range of effective composite properties if discussed. While this problem considers fixed infill properties, the methods applied could readily be extended to smart material infills. The contour plots and performance estimation employed in this research provides an important step in the design of improved smart composites for use in morphing and variable stiffness structures.
Stochastic Signal Analysis and Processing of Non-Harmonic, Periodic Vibrational Energy Harvesters
Authors: Germer Maxim , Marschner Uwe , Richter Andreas
Published: October 2021

This study presents a novel signal description based on stochastic signal analysis, applicable to electromagnetic, piezomagnetic or other transducers without energy storage as a capacitor. At present the peak power and average power are used to characterize the energy transducer. As for non-harmonic signals the last-mentioned quantities compress the time in a way, that inhibits predicting the transferable energy for different charge based interface circuits to charge a storage capacitor.

The main objectives are first, to represent the data meaningfully, second, to incorporate the effect of lossy rectifiers on the raw data and third, to evaluate the performance of chosen energy harvesters together with the interface circuits efficiently. The foundation relies in considering the measured time signal as a realization of an ergodic process. The probability density function (PDF) and the cumulated density function (CDF) build the fundament and are used to link the signal magnitudes to their probability of occurrence. New distribution functions are introduced to determine both, the charges and the energy of an electromagnetic transducer above a specific signal amplitude, which can be imposed by a voltage drop of one or several components. The presented method is further applied on the well-known full wave rectifier and to calculate its momentary efficiency, being limited by 92% for a sinusoidal signal.

As a result, the paper applies the new stochastic signal representation to energy harvesters to extends the state-of-the-art time and frequency signal analysis. Different interface circuits with energy storage can be quickly calculated for different initial storage voltages, much faster than powerful network simulators.
Machine Learning-Assisted Modeling and Design Optimization of Hybrid Shape Memory Alloy Axial Actuators
Authors: Guan Weilin , Hewakuruppu Hasitha J. , Peraza Hernandez Edwin A.
Published: October 2021

Shape memory alloys (SMAs) are materials that can generate and recover moderate inelastic strains through temperature modulation. This characteristic enables SMAs to function as lightweight and compact thermomechanical actuators. The synthesis of SMA actuators for systems with specific requirements on their actuation path (displacement stroke vs. temperature) currently relies on complex and expensive material processing and characterization. This paper first presents a geometric approach for synthesizing novel SMA axial actuators, termed as hybrid SMA actuators, whose dimensions (length and cross-sectional area) and material distribution are modulated to approximate a target actuation path. Through the combination of multiple SMA wire sections in series, the hybrid SMA actuators can exhibit actuation paths not achievable by using single monolithic SMA wires. The paper then presents a machine learning-assisted framework for the surrogate modeling of hybrid SMA actuators. This approach allows for the prediction of their actuation path without the use of structural simulations leveraging numerical implementations of constitutive models, allowing for simplified and computationally efficient modeling and circumventing convergence issues. A surrogate model consisting of an ensemble of binary decision trees is trained using data obtained via a design of experiments performed using structural simulations. A validation test using 5000 design samples for hybrid SMA actuators with two sections demonstrates R2 values of 0.99983 and 0.99979 for the actuation displacement during heating and cooling, respectively. The evaluation time for the validation samples using the trained surrogate model is less than 8 minutes, while the evaluation time using structural simulations is 59 minutes. Finally, a surrogate-based optimization approach is demonstrated through the synthesis of hybrid SMA actuators capable of exhibiting prescribed displacement vs. temperature target actuation paths.
Characterization of sphere-plane contact loss nonlinearity inside a cylindrical container using nonlinear ultrasound resonance spectroscopy
Authors: Lin Kevin Yi-Wei , Prather Wayne E. , Mobley Joel
Published: October 2021

Cylindrical containers, such as liquid tanks and pressure vessels, are ubiquitous in storage applications. Traditional lines of non-destructive evaluation (NDE) are mostly focused on the integrity of containers, but studies on solid contents within using external sensors are lacking. In previous work, metrics were developed to estimate the structural integrity of mock-up fuel assemblies inside a lab-scale nuclear dry storage cask. Linear acoustic resonance techniques were shown to be sensitive down to single assembly level. In this work, this problem is further examined by studying contact nonlinearity in a simplified system using Nonlinear Ultrasound Resonance Spectroscopy (NRUS). This system consists of a single layer of identical spheres with varying composition and size evenly distributed at the bottom of a cylindrical aluminum container. The resonance frequency shifts due to varying amplitudes were mostly affected by the total mass of spheres inside, while diameter and composition of spheres played minor roles. A phenomenological model was developed based on the resulting shifts and was studied numerically using finite element simulations. The agreement between simulations and experiments suggests that the contact nonlinearity is predominated by a contact loss mechanism. This NRUS technique may complement linear acoustic techniques for solid cargo NDE inside sealed vessels.
ACOUSTICAL STANDARDS NEWS
Authors: Blair-DeLeon Nancy A. , Struck Christopher J.
Published: October 2021

American National Standards (ANSI Standards) developed by Accredited Standards Committees S1, S2, S3, S3/SC 1, and S12 in the areas of acoustics, mechanical vibration and shock, bioacoustics, animal bioacoustics, and noise, respectively, are published by the Acoustical Society of America (ASA). In addition to these standards, ASA publishes a catalog of Acoustical American National Standards. To browse the latest copy of our catalog, visit our website at https://acousticalsociety.org/download-catalog/.

Comments are welcomed on all material in Acoustical Standards News.

This Acoustical Standards News section in JASA, as well as the National Catalog of Acoustical Standards and other information on the Standards Program of the Acoustical Society of America, are also available via the ASA Standards home page: https://acousticalsociety.org/acoustical-society-standards/.
Cytochrome OmcS Is Not Essential for Extracellular Electron Transport via Conductive Pili in Geobacter sulfurreducens Strain KN400
Authors: Liu Xinying , Holmes Dawn E. , Walker David J. F. , Li Yang , Meier David , Pinches Samantha , Woodard Trevor L. , Smith Jessica A.
Published: October 2021

OmcS has been widely studied and noted to be one of the key components for extracellular electron exchange by the
Geobacter sulfurreducens
strain DL-1. However, the true importance of OmcS warrants further investigation because it is well known that few bacteria, even within the
Geobacteraceae
family, contain OmcS homologs, and many bacteria that are capable of extracellular electron transfer lack an abundance of any type of outer surface
c
-type cytochrome.
Coprinopsis cinerea Uses Laccase Lcc9 as a Defense Strategy To Eliminate Oxidative Stress during Fungal‐Fungal Interactions
Authors: Liu Juanjuan , Peng Can , Han Qiqi , Wang Mengyao , Zhou Gang , Ye Bin , Xiao Yazhong , Fang Zemin , Kües Ursula
Published: October 2021

The overproduction of laccase during interspecific fungal interactions is well known. However, the exact role of the upregulated laccases remains underexplored.
Colibrimycins, Novel Halogenated Hybrid Polyketide Synthase-Nonribosomal Peptide Synthetase (PKS-NRPS) Compounds Produced by
Streptomyces
sp. Strain CS147
Authors: Prado-Alonso Laura , Pérez-Victoria Ignacio , Malmierca Mónica G. , Montero Ignacio , Rioja-Blanco Elisa , Martín Jesús , Reyes Fernando , Méndez Carmen , Salas José A. , Olano Carlos
Published: October 2021

Genome mining has proven its usefulness in the search for novel bioactive compounds produced by microorganisms, and halogenases comprise an interesting starting point. In this work, we have identified a new halogenase coding gene that led to the discovery of novel lipopetide nonribosomal peptide synthetase/polyketide synthase (NRPS/PKS)-derived natural products, the colibrimycins, produced by
Streptomyces
sp. strain CS147, isolated from the
Attini
ant niche.
β-1,3-
d
-Glucan and Galactomannan as Biomarkers for the Detection of Invasive
Geotrichum
and
Magnusiomyces
Infections: a Retrospective Evaluation
Authors: Forster Johannes , Koc Özlem , Koeppel Martin B. , Hamprecht Axel , Kurzai Oliver , Suerbaum Sebastian , Wagener Johannes , Dichtl Karl
Published: October 2021

Magnusiomyces
and
Geotrichum
species are ascomycetous yeasts that can cause potentially life-threatening invasive fungal infections commonly referred to as geotrichosis. In this study, we aimed to estimate the incidence and mortality of these infections in a German tertiary care center.