Primary Structural Parameters Research Articles

The Role of the Primary Structure in the Formation of the Mechanical Properties of Steel Castings

The paper considers the total effect of primary structure parameters on steel mechanical properties depending on the wall thickness of castings. It is shown that during the formation of mechanical properties with an increase in the thickness of the work-piece, the role of the sizes of primary grains decreases and the role of reducing the dispersion of dendritic crystals increases, due to the process of dendritic branches coarsening.

Study on the Design Method of a New Hydro-Mechanical Continuously Variable Transmission System

A design method for a new power-cycling hydro-mechanical continuously variable transmission (PCHMCVT) system is proposed in this study. The transmission efficiency in this method is defined to be the design standard. The design target ensures the maintenance of the transmission efficiency at more than 80% in different driving modes. In this study, the primary structural parameters are first calculated with respect to the PCHMCVT for the Dongfanghong 1302R tractor, based on the tractor’s required traction. Moreover, the original transmission structure is improved for the purpose of improving transmission efficiency in the reverse gear mode through the simulation analysis. Thereafter, according to the speed requirement of the tractor and the speed ratio continuous condition of PCHMCVT, two gears and five working modes (four forward modes and one reverse mode) are designed to maintain the tractor to operate high efficiency at different driving modes. Finally, PCHMCVT has more powerful low-speed torque-increasing characteristics and vehicle power commutation characteristics based on the simulation analysis of the tractor’s basic characteristics and then proved the feasibility of PCHMCVT design method.

Study on the Stability of a Transition Section from Soft to Hard Surrounding Rock Based on the Solid‐Fluid Coupling Effect

To study the stability of a transition section of a tunnel from soft to hard surrounding rock under seepage conditions, FLAC3D software was used to numerically simulate the transition section of the Laomushan Tunnel from the Shiqian to Yuping (Dalong) Expressways in Guizhou Province, China, and to explore different working conditions. The characterization of the tunnel seepage field, stress field, and displacement field and the analysis of the force of the primary lining support structure describe the influence of the seepage field on the stress field distribution and displacement field changes. The reliability of the calculation results is verified by comparison with displacement measurements collected during field monitoring. The design values of the primary support structure parameters of the transition section from soft to hard surrounding rock of the Laomushan Tunnel basically met the strength requirements. The research results provide references for the design and construction of similar projects.

Further investigation of the relationship between polymer structure and HDPE post yield properties

Using typical characterization methods (hyphenated chromatography and calorimetry), the effects of molecular weight and short chain branching (SCB) on relative rates of crystallization and the resulting effects on the post yield tensile properties were quantified for a robust set of high-density polyethylene samples. A semi-empirical chain folding equation coupled with the new structure parameters PSP4 (tie molecule content) and the average number of lamella segments per chain (ALSC) were proposed. These parameters are based on a random polymer walk, including passes through the crystalline lamella, the number of times a chain folds in each lamella and the subsequent effects on the end to end distance of the polymer chain, <R>. Intuitively, the current approach is expected to yield enhanced correlations to mechanical performance since, in addition to maintaining the improvements in lamella size calculation, persistence length dependence on SCB content, and multi-ties per chain, it also accounts for polymer chain folding and lamella orientation. Results showed that homopolymers had a significantly higher level of chain folding compared to copolymers. Moreover, as the length of the SCB increased from ethyl to butyl, less folding was predicted thereby leaving more of the polymer chain to form tie molecules. The quantity PSP43/ALSC, exhibited a linear relationship with strain hardening modulus (SHM) with excellent correlation for a diverse set of unimodal and bimodal resins made using different catalyst systems, which included homopolymers, copolymers, and blends of different catalyst type and modality. Given the simplicity of calculation, use of actual polymer data, and the good predictability offered for SHM for a diverse set of resins, these primary structure parameters (PSP4 and ALSC) have high potential to contribute to the in-depth understanding of polymer structure-property relationships.

A Tubular Staggered-Teeth Transverse-Flux PMLM With Circumferentially Distributed Three-Phase Windings

This paper investigates a special tubular staggered-teeth transverse-flux permanent-magnet linear machine (TST-TFPMLM) for a free-piston Stirling power generating system. With the complicated flux leakage characteristic of the TST-TFPMLM considered, the general forms and evaluation method of the flux leakage are investigated by finite-element analysis, and the distribution law and reduction method of the flux leakage are obtained. To help the initial design of the TST-TFPMLM, both back electromotive force (EMF) and thrust are taken as the main concerned aims, and the influence of some primary structural parameters on both back EMF and thrust is studied. To improve the key performances of the TST-TFPMLM, the power factor is investigated with respect to the dimensions of permanent magnets (PMs), winding turns, armature current, internal power factor angle, and tooth tip dimensions. Furthermore, the methods of improving both efficiency and thrust density are explored. A prototype machine is manufactured and tested, and satisfactory experimental results are obtained, showing the feasibility of the TST-TFPMLM for the free-piston Stirling power generating system. This investigation provides a new idea to solve the drawbacks of conventional transverse-flux PM linear machines, which include complicated structure, poor manufacturability, high flux leakage, and low power factor.

Experimental Evaluation of Vibration Response of External Post-Tensioned Tendons with Corrosion

This study investigates the vibration responses of external post-tensioned (PT) tendons based on experimental data. The vibration signals measured from four large-scale external post-tensioned tendon specimens subjected to localized corrosion until severe level of damage were accumulated. A series of impact tests was conducted to measure lateral vibration signals and the variation in the tension was continuously monitored using a load cell. The acquired vibration signals were evaluated using an axially-tensioned beam model in which the properties were varied to reflect the loss of tension and the reduction in the bending stiffness caused by corrosion damage. A comparison between the experimental data and the analytical results indicates that the natural frequencies were shifted as the residual tension decreased but were influenced by corresponding grout damage in a limited range. As a result, the frequency response was not appreciably affected by the damage level and the tension remained as the primary structural parameter of the external PT tendon with damage.

Global sensitivity analysis of offshore wind turbine foundation fatigue loads

The design and analysis of offshore wind turbine foundations are traditionally based on deterministic time-domain simulations of a numerical model. The wind turbine, support structure and environmental conditions are represented by a large number of input parameters, whose uncertainties are accounted by applying partial safety factors. In this paper, the sensitivity of fatigue loads with respect to primary structural, geotechnical and metocean parameters are investigated for a 5 MW offshore wind turbine installed on a gravity based foundation. Linear regression of Monte Carlo simulations and Morris screening are performed for three design load cases. Results show that parameter significance rankings vary according to which design load case is considered. In general, uncertainties in the fatigue loads are highly influenced by turbulence intensity and wave load uncertainties, while uncertainties in soil property suggest significant nonlinear or interactive effects. This work provides insights to foundation designers and wind turbine manufacturers on which parameters must be assessed in more detail in order to reduce uncertainties in load prediction.

Seismic responses of postyield hardening single–degree‐of‐freedom systems incorporating high‐strength elastic material

SummaryIt is widely accepted that ductility design improves the seismic capacity of structures worldwide. Nevertheless, inelastic deformation allows serious damage to occur in structures. Previous studies have shown that a certain level of postyield stiffness may reduce both the peak displacement and residual deformation of a structure. In recent years, several high‐strength elastic materials, such as fiber‐reinforced polymer (FRP) and high‐strength steel bars, have been developed. Application of these materials can easily provide a structure with a much higher and more stable postyield stiffness. Many materials, members, and structures that incorporate both high‐strength elastic materials and conventional materials show significant postyield hardening (PYH) behaviors. The significant postyield stiffness of PYH structures can help effectively reduce both peak and residual deformations, providing a choice when designing resilient structures. However, the findings of previous studies of structures with elastic‐perfectly plastic (EPP) behavior or small postyield stiffness may not be accurate for PYH structures. The postyield stiffness of a structure must be considered an important primary structural parameter, in addition to initial stiffness, yielding strength, and ductility. In this paper, extensive time history and statistical analyses are carried out for PYH single–degree‐of‐freedom (SDOF) systems. The mean values and coefficients of variation of the peak displacement and residual deformation are obtained and discussed. A new R‐μp‐T‐α relationship and damage index for PYH structures are proposed. A theoretical model for the calculation of residual deformation is also established. These models provide a basis for developing the appropriate seismic design and performance evaluation procedures for PYH structures.

Insights into the excited state dynamical process for 3‐hydroxy‐2‐(5‐(5‐(5‐(3‐hydroxy‐4‐oxo‐4H‐chromen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)‐4H‐chromen‐4‐one

AbstractIn this present work, we theoretically investigate a novel system 3‐hydroxy‐2‐(5‐(5‐(5‐(3‐hydroxy‐4‐oxo‐4H‐chromen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)‐4H‐chromen‐4‐one (FT) based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. Via calculating the reduced density gradient (RDG) versus sign(λ2) ρ, we firstly verify the formation of the dual intramolecular hydrogen bonds (O1─H2···O3 and O4─H5···O6) for FT form in the S0 state. Then comparing the primary structural parameters and corresponding infrared (IR) vibrational spectra involved in hydrogen bonds between S0 and S1 state, we demonstrate that these two intramolecular hydrogen bonds should be strengthened in the S1 state. Insights into the vertical excitation process, our theoretical results reproduced experimental absorption nature, which confirms that the theoretical level (B3LYP/TZVP) is reasonable and effective in this work. And frontier molecular orbitals (MOs) depict the nature of electronically excited state and support the excited‐state intramolecular proton transfer (ESIPT) reaction. According to the calculated results of potential energy curves along stepwise and synergetic O1─H2 and O4─H5 coordinates, we verify that only the excited‐state single‐proton transfer could occur for FT molecule in the S1 state, although it possesses two intramolecular hydrogen bonds. We not only investigate the detail excited‐state behaviors for FT system and elaborate the ESIPT mechanism but also explain previous experimental results.

Charged domain walls in improper ferroelectric hexagonal manganites and gallates

Ferroelectric domain walls are attracting broad attention as atomic-scale switches, diodes and mobile wires for next-generation nanoelectronics. Charged domain walls in improper ferroelectrics are particularly interesting as they offer multifunctional properties and an inherent stability not found in proper ferroelectrics. Here we study the energetics and structure of charged walls in improper ferroelectric YMnO$_3$, InMnO$_3$ and YGaO$_3$ by first principles calculations and phenomenological modeling. Positively and negatively charged walls are asymmetric in terms of local structure and width, reflecting that polarization is not the driving force for domain formation. The wall width scales with the amplitude of the primary structural order parameter and the coupling strength to the polarization. We introduce general rules for how to engineer $n$- and $p$-type domain wall conductivity based on the domain size, polarization and electronic band gap. This opens the possibility of fine-tuning the local transport properties and design $p$-$n$-junctions for domain wall-based nano-circuitry.

Correlating polyethylene microstructure to stress cracking: Development of primary structure parameters

New primary structure parameters (PSP3 and PSP3*) were developed to help better understand the effects of polymer microstructure on polyethylene stress cracking as determined by post yield tensile tests. Previously, the structure parameter, PSP2, was obtained using only molecular weight distributions (MWD) and short chain branching distributions (SCBD) obtained from size exclusion chromatography coupled to a Fourier transform inferred detector (SEC-FTIR). By augmenting the MWD and SCBD with differential scanning colorimetry (DSC) analysis to better estimate crystalline lamella distributions, a more robust process was developed to estimate the critical lamella distance, L, that a molecule must span to form a tie molecule. Improvements were also made to estimate the end to end distance, R, by including SCB effects on persistence length, and consideration for the probability of more than one tie molecule per polymer chain was included in the calculation. By generating a three dimensional, digital, crystalline-lattice and using random walk statistics, PSP3 and PSP3* values were estimated for various monomodal and bimodal copolymers as well as homopolymer resin sets. Furthermore, a new parameter; the average number of crystalline lamella per polymer chain (ANCC) was developed. The entire method required low computational time, while allowing us to investigate very large molecular weights. These latter parameters (PSP3* and ANCC) capture for the first-time, ties formed between multiple lamella by a single polymer chain. Good correlations between the strain hardening modulus (ISO, 18488 test standard) and PSP3* were found as well between ANCC−1 values and the % natural draw ratio (NDR) at 80 °C.

Analysis and parametric optimization of a novel sandwich panel with double-V auxetic structure core under air blast loading

Blast shock wave is a big threat to the military vehicle and may cause vehicle damages and passenger casualties. It is a big issue to balance the protective performance and lightweight property of military vehicle. In these days, many types of sandwich panels with different cores were applied as protective plates in military vehicles. In view of the excellent energy absorption capability of auxetic structure, applying auxetic structure as sandwich panel core for blast protection purpose is a promising field. However, existing in-plane configuration of two-dimensional auxetic honeycomb core always represent anisotropic behaviour. In this paper, a novel sandwich panel with three-dimensional double-V Auxetic (DVA) structure core, which can produce isotropic mechanical behavior, was proposed for air blast protection purpose. Its primary structural parameters and their relations were discussed, and a parametric numerical model was established. In order to reduce both the dynamic response under air blast loading and mass, the design variables and objective function of the DVA core optimization problem were confirmed, then parametric optimization was conducted based on Latin Hypercube Sampling (LHD) method, Gaussian process metamodel (GPM) and multi-objective particle swarm optimization algorithm (MOPSO). Finally, it is proved that the applied optimization process is efficient and can obtain accurate optimum points. The proposed DAV core sandwich panel performed much better both in lightweight and protection than solid plate and has an apparent merit in lightweight aspect compared with square honeycomb core sandwich panel.

Mapping the Structure–Property Space of Bimodal Polyethylenes Using Response Surface Methods. Part 1: Digital Data Investigation

AbstractA new method is proposed to study the multidimensional structure–property space of bimodal ethylene/1‐olefin copolymers using fundamental polymerization models and response surface methods. The fundamental polymerization models describe how the polymer microstructure depends on polymerization conditions, in particular how the short chain branching frequency varies across the molecular weight distribution. Statistical design of experiment techniques combined with response surface methods generates the minimum number of digital experiments needed to estimate the parameters for a forward model. The polymer microstructural data are combined with empirical equations to calculate polymer density and the primary structural parameter to quantify the presence of tie molecules in the polymer. This procedure links polymerization conditions to polymer microstructure and properties using the forward model. More importantly, the forward model can be reversed to determine which polymerization conditions are needed to make polymers with a given set of properties.

Polyolefins Made with Dual Metallocene Catalysts: How Microstructure Affects Polymer Properties

AbstractSlow crack growth resistance correlates with the lifetime of polyethylene pipes. Since this measurement may take considerable time, alternative ways to estimate it help expedite the development of new polyethylene resins. The primary structural parameter (PSP2), calculated from the distribution of molecular weight and short chain branching of polyethylenes, can predict the stress crack growth resistance of polyethylene resins without needing to measure it over long periods of time. In this investigation, a model is developed to calculate PSP2 of ethylene homopolymers and ethylene/1‐hexene copolymers made with two metallocene catalysts. For each metallocene, the effect of the following parameters on PSP2 is investigated: (1) polymer mass fraction, (2) polymer average molecular weight, and (3) average comonomer fraction. The simulation trends agree with previously published experimental results. The generated 3D surface response plots are useful guides for the design of polyethylenes having optimized slow crack growth resistance.

The effect of benzo‐annelation on intermolecular hydrogen bond and proton transfer of 2‐methyl‐3‐hydroxy‐4(1H)‐quinolone in methanol: A TD‐DFT study

AbstractExcited‐state intermolecular or intramolecular proton transfer (ESIPT) reaction has important potential applications in biological probes. In this paper, the effect of benzo‐annelation on intermolecular hydrogen bond and proton transfer reaction of the 2‐methyl‐3‐hydroxy‐4(1H)‐quinolone (MQ) dye in methanol solvent is investigated by the density functional theory and time‐dependent density functional theory approaches. Both the primary structure parameters and infrared vibrational spectra analysis of MQ and its benzo‐analogue 2‐methyl‐3‐hydroxy‐4(1H)‐benzo‐quinolone (MBQ) show that the intermolecular hydrogen bond O1―H2⋯O3 significantly strengthens in the excited state, whereas another intermolecular hydrogen bond O3―H4⋯O5 weakens slightly. Simulated electron absorption and fluorescence spectra are agreement with the experimental data. The noncovalent interaction analysis displays that the intermolecular hydrogen bonds of MQ are obviously stronger than that of MBQ. Additionally, the energy profile analysis via the proton transfer reaction pathway illustrates that the ESIPT reaction of MBQ is relatively harder than that of MQ. Therefore, the effect of benzo‐annelation of the MQ dye weakens the intermolecular hydrogen bond and relatively inhibits the proton transfer reaction.

Relation between the Hardness and the Strength of Gray Cast Iron with Allowance for the Structural Parameters

The factors that affect the relation between ultimate tensile strength σu and hardness HB of gray cast iron with flaked graphite are studied. The scatter of the ultimate tensile strengths at a given hardness is shown to be caused by one of the primary structure parameters, namely, the volume fraction of primary austenite dendritic crystals. The dependences derived in this work can be used to increase the accuracy of a rapid estimation of the quality of cast iron ingots.

Optical design of wide-angle multi-wavelength f-theta lens

The f-theta lens is an important essential component in laser scanning systems that plays a decisive role in working surface, measuring speed and measurement accuracy, etc. A wide-angle f-theta lens operating at 486 nm ~ 656 nm is designed to change the range of small f-theta lens scanning range and single operating wavelength.Through the primary aberration analysis, the primary structure parameters of the system are determined, and the chromatic aberration correction is carried out by using the optical power distribution with different dispersion properties. The final design result shows that the lateral color is less than 3 μm, the calibrated f-Theta distortions are all less than 0.015% and the energy utilization rate is nearly 90%, which means that the focusing performances are close to the diffraction-limited. The system meets the requirements of high-precision laser marking systems with different waves.

ChemInform Abstract: Self‐Assembled Structures from Amphiphilic Peptides

Nanotechnology and its applications are strongly influenced by structures self-assembled from a variety of different materials. This review covers nanostructures, including micelles, rod-like micelles, fibers and peptide beads, self-assembled from de novo designed amphiphilic peptides. The latter are promising candidates for the development of nanoscale carrier systems because they are completely composed of amino acids. In addition to designing primary sequences, secondary structure and external parameters are also discussed with respect to their impact on self-assembly. Moreover, the assembly process itself is examined. Potential applications range from gene and drug delivery devices to diagnostics, thereby highlighting the versatility of the system.

Design and characterization of thick InxGa1-xAs metamorphic buffer layers grown by hydride vapor phase epitaxy

Thick InxGa1-xAs metamorphic buffer layers (MBLs) grown by hydride vapor phase epitaxy (HVPE) were studied. Relationships between MBL properties and growth parameters such as grading rate, cap layer thickness, final xInAs, and deposition temperature (TD) were explored. The MBLs were characterized by measurement of in-plane residual strain (妦), surface etch pit density (EPD), and surface roughness. Capping layer thickness had a strong effect on strain relaxation, with thickly capped samples exhibiting the lowest 妦. EPD was higher in samples with thicker caps, reflecting their increased relaxation through dislocation generation. 妦 and EPD were weakly affected by the grading rate, making capping layer thickness the primary structural parameter which controls these properties. MBLs graded in discrete steps had similar properties to MBLs with continuous grading. In samples with identical thickness and 10-step grading style, 妦 increased almost linearly with final xInAs, while total relaxation stayed relatively constant. Relaxation as a function of xInAs could be described by an equilibrium model in which dislocation nucleation is impeded by the energy of the existing dislocation array. EPD was constant from xInAs = 0 to 0.24 then increased exponentially, which is related to the increased dislocation interaction and blocking seen at higher dislocation densities. RMS roughness increased with xInAs above a certain strain rate (0.15%/µm); samples grown below this level possessed large surface hillocks and high roughness values. The elimination of hillocks at higher values of xInAs is attributed to increased density of surface steps and is related to the out-of-plane component of the burgers vector of the dominant type of 60° dislocation. TD did not affect 妦 for samples with a given xInAs. EPD tended to increase with TD, indicating dislocation glide likely is impeded at higher temperatures.

Erratum: Domain walls in a perovskite oxide with two primary structural order parameters: First-principles study ofBiFeO3[Phys. Rev. B87, 024102 (2013)

Received 22 January 2014DOI:https://doi.org/10.1103/PhysRevB.89.059901©2014 American Physical Society