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The influence of fabrication and assembly errors on the surface distortion due to gravity of a 2 m primary mirror and its correction method are presented. The effect of fabrication errors on the surface distortion is verified by Monte Carlo analysis. The results show that, within the 46.3% confidence interval, the surface accuracy root mean square (RMS) caused by fabrication errors is more than 5.0 nm (indicator requirement). The sensitivity of mirror surface accuracy to the matching relationship between the flexible support axial assembly position and the inherent properties (neutral surface and center of gravity) of the mirror were analyzed. Then, the correction principle of the RMS was proposed based on the analysis result. The surface accuracy RMS of surface gravity distortion is sensitive to fabrication and assembly errors, which can be effectively corrected using a flexible support mounting technique. This new flexible support mounting technique replaces the conventional method with flexible supports having shims so that adjustments can be made during testing to counteract the gravitational distortion of the mirror surface. Astigmatic aberration due to gravitational changes is effectively reduced by selecting a suitable thickness of shim, and the relationship between the astigmatism and the thickness of shim was investigated using the finite element analysis method. Finally, the finite element analysis results showed that the optimal surface gravity accuracy of the mirror assembly could be obtained by adjusting the shim, while the other performance of the assembly was not affected. [ABSTRACT FROM AUTHOR]

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The influence of fabrication and assembly errors on the surface distortion due to gravity of a 2 m primary mirror and its correction method are presented. The effect of fabrication errors on the surface distortion is verified by Monte Carlo analysis. The results show that, within the 46.3% confidence interval, the surface accuracy root mean square (RMS) caused by fabrication errors is more than 5.0 nm (indicator requirement). The sensitivity of mirror surface accuracy to the matching relationship between the flexible support axial assembly position and the inherent properties (neutral surface and center of gravity) of the mirror were analyzed. Then, the correction principle of the RMS was proposed based on the analysis result. The surface accuracy RMS of surface gravity distortion is sensitive to fabrication and assembly errors, which can be effectively corrected using a flexible support mounting technique. This new flexible support mounting technique replaces the conventional method with flexible supports having shims so that adjustments can be made during testing to counteract the gravitational distortion of the mirror surface. Astigmatic aberration due to gravitational changes is effectively reduced by selecting a suitable thickness of shim, and the relationship between the astigmatism and the thickness of shim was investigated using the finite element analysis method. Finally, the finite element analysis results showed that the optimal surface gravity accuracy of the mirror assembly could be obtained by adjusting the shim, while the other performance of the assembly was not affected.

This article introduces the study of peripheral clamping for large-aperture laser mirrors in high power laser facilities. Some multi-point clamping schemes were experimentally tested, the results of the experiments show that these schemes cannot meet the technical requirements, and in the simulation analysis, we explain the reason for this phenomenon. It is concluded that the additional bending moment caused by the non-ideal process factors in the multi-point clamping is the main cause for the surface distortion. Based on the above conclusions, we carried out research on minor-point clamping. Experimental verification of the minor-point clamping were done, the results show that the minor-point clamping can meet the requirements of technical indicators in whole process. This work can provide a reference for the design of the large-aperture transport mirror clamping structure, which may be used in huge laser devices and telescopes. [ABSTRACT FROM AUTHOR]

Assembling two-dimensional (2D) sheets into macroscopic three-dimensional (3D) forms has created a promising material family with rich functionalities. Multiscale wrinkles are intrinsic features of 2D sheets in their 3D assembles. Therefore, the precise wrinkling modulation optimizes the transition of outstanding properties of 2D sheets to expected performances of assembled materials and dominates their fabrication process. The wrinkling evolution of 2D sheets assembling onto flat surfaces has been extensively understood, however, the wrinkling behaviors on the more generally curved surface still remain unclear. Here, we investigate the wrinkling behaviors of graphene oxide sheets assembled onto curved surfaces and reveal the selection rule of wrinkling modes that determined by the curvature mismatch between 2D sheets and target surfaces. We uncover that three wrinkling modes including isotropic cracked land, labyrinth, and anisotropic curtain phases, respectively emerge on flat, spherical, and cylindrical surfaces. A favorable description paradigm is offered to quantitatively measure the complex wrinkling patterns and assess the curvature mismatch constraint underlying the wrinkling mode selection. This research provides a general and quantitative description framework of wrinkling modulation of 2D materials such as high performance graphene fibers, and guides the precise fabrication of particles and functional coatings. [ABSTRACT FROM AUTHOR]

The TDICCD aerial camera was developed to study the relationship between the structure and optical system. Based on the camera outputs, integrated analysis and experimental methods were proposed. The proposed method was then used to both study and verify the influence of thermal disturbance on the optical performance and optimal aerial camera design. The nodal displacement of the optical surface under thermal disturbance was calculated via the finite element method. The resulting data were fitted to Zernike polynomial coefficients using the Zernike polynomial. Additionally, a method of calculating rigid body displacement was also proposed to determine the effects of rigid optical system displacement. The method calculates the RMS and PV parameters by fitting the surface distortion data. The fitted Zernike polynomial coefficients were input to ZEMAX software to obtain the optical system response. The influence of thermal disturbance on the optical performance of the aerial camera was analyzed. The analysis results have shown that the low-temperature conditions have a more prominent impact on the optical performance of aerial cameras. The radial and axial lens steady-state temperature range was 2.06 °C in conduction temperature of − 40 °C. At the same time, the aerial camera surface was frosted at − 40 °C to carry out the low-temperature experiment, which verified the results obtained for a large temperature difference environment. Finally, results were verified experimentally. [ABSTRACT FROM AUTHOR]

For a dual reflector antenna whose subreflector is also equivalent to a large reflector antenna, its structure will inevitably be deformed due to the effect of gravity, wind, temperature, and so on. This article is inspired by the homologous idea applied to main reflectors and extends this idea to subreflectors to eliminate the harmless error of the distorted subsurface by using the best fit surface of the same type. This article proposes seven parameters to determine the best fit subreflector (BFS): five rigid parameters (three translation and two rotation parameters) and two parameters related to the change of the subreflector shape. These seven homology parameters are calculated by the least square method (LSM). The subreflector of the QiTai radio telescope (QTT) is used in two examples. The first example shows that the proposed method can effectively calculate the BFS surface and obtain the accuracy that has eliminated the harmless error of the distorted subreflector. In the second example, the accuracy without harmless error is used in the classical design so that the homologous design of the subreflector structure is realized. The excellent results show the validity of the proposed method and provide an important reference for the structure design of large subreflectors. [ABSTRACT FROM AUTHOR]

At the stage of structural optimization, the subreflector structure should be designed such that it compensates for the residual error or relaxes the accuracy requirement of the main reflector to a certain extent. However, there is no fast and effective means to shape the subreflector during the structural optimization process. This communication is based on the application of geometrical optics (GO)/physical optics (PO) analysis to shape a subreflector for antenna distortion compensation. Thus, a method performing an iterative approximation to the GO/PO analysis is proposed. Unlike GO shaping or optimization, the proposed method is not formulated by simultaneous nonlinear ordinary differential equations. Therefore, the main contribution of this communication is that the method does not entail computationally intensive calculation and optimization, and thus, it does not require a large amount of time to complete the calculation. The proposed method is very suitable for a large reflector antenna with a small-amplitude deformation and smoothly varying errors such that the shaped subreflector does not have a significant effect on the amplitude of the main reflector’s electric field. An example with regard to the symmetric system is presented. The obtained results demonstrate that the proposed method is effective. [ABSTRACT FROM AUTHOR]

Nanoscale inhomogeneities, such as defects and wrinkles, in atomic layers of transition-metal dichalcogenide (TMDC) semiconductor materials deteriorate the remarkable physical and optoelectronic properties of these materials, precluding their use in optoelectronic devices. Such inhomogeneities can be investigated using vibrational spectroscopic analysis methods, such as Raman spectroscopy, because the deformations in a sample could be identified by the changes in the Raman vibrational energies of the sample. However, it has been challenging to characterize structures localized on the nanoscale in TMDC layers, because such characterization requires a nanoscale high spatial resolution. Here, we present tip-enhanced Raman spectroscopy (TERS) of molybdenum disulfide (MoS2) in the form of monolayers and a few layers to investigate nanoscale inhomogeneities. TERS enables Raman analysis with the nanoscale spatial resolution, using the near-field light generated at a metallic nano-tip through plasmon resonance. TERS imaging, which demonstrates spatially varying Raman spectral features on the nanoscale, allows one to elucidate the existence of nanoscale inhomogeneities. Using this method, defects and wrinkles within MoS2 layers were characterized with a spatial resolution better than 20 nm. This study provides important insights into unique optical and electronic properties of TMDCs for the development of future optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract In order to clarify the alloying effect on the band engineering in two-dimensional transition metal dichalcogenides (2D-TMDs) at the atomic level, we present a quantitative study to address a deeper insight on the relationship between the bond identities and band shift based on the bond relaxation mechanism and valance-force-field approach. We find the interaction parameter in 2D-TMDs alloys could be obtained from the lattice distortion energy and further reveal the bowing mechanism of composition tunable bandgap in 2D-TMDs. Our results show that the composition-dependent band shift is in good agreement with the available evidence, which suggest the tunable electronic properties of 2D-TMD alloys that realized by modulating the chemical composition could be helpful for nanoelectronic applications. Highlights • Propose a quantitative method to investigate the distortion energy for the 2D-TMD alloys with the composition. • Obtain the interaction parameter from the distortion energy and clarify the bowing mechanism of composition tunable bandgap. • Establish the relationship between the band shift and the composition for 2D-TMD alloys. • Reveal the physical mechanism on the band engineering of 2D-TMD alloys at the atomic level. [ABSTRACT FROM AUTHOR]

To consider the effects of random surface errors on the radiation pattern of cylindrical reflector antennas, a second-order expansion computation method is proposed to calculate the boresight gain loss and average power pattern. The additional phase error caused by random surface distortion is expanded into a second-order Taylor series expansion in radiation integral. Based on the probabilistic Gaussian distribution of phase errors, the boresight gain loss and average power pattern can be simplified into a second-order expression of a root-mean-square (rms) value of random surface errors. Simulation results on a Ku/Ka-bands parabolic cylindrical reflector illustrate that the second-order expansion can account for the boresight gain loss within a computational accuracy of 0.1 dB when the rms value of random surface errors is below $\lambda /22$ for the Ku-band, as well as $\lambda /24$ for the Ka-band. When the rms value of random surface errors is below $\lambda /50$ for the Ku-band, or $\lambda /100$ for the Ka-band, the second-order expansion can also account for the first sidelobe in an average power pattern. [ABSTRACT FROM AUTHOR]

Abstract: 2D nonlayered materials that possess appealing properties are entering the researchers' vision. However, direct access to the 2D level of these materials is still a great challenge due to the instrinsic isotropic chemical bond. This work presents the initially self‐limited epitaxial growth of ultrathin nonlayered CdS flakes (as thin as 6 nm) on mica substrate with a large domain size (>40 µm) by employing In2S3 as the passivation agent. Besides, the thickness and sizes of the products could be tunable by the addition level of In2S3 amount. The growth mechanism is evidenced via experiments and theoretical calculations, which is attributed to the surface distortion effect of In–S motif and the preference of local environments for In on the CdS (0001) surface. The photodetector designed on CdS flake demonstrates a high photoswitching ratio (up to 103), a high detectivity (D* ≈ 2.71 × 109 Jones), and fast photoresponse speed (τR = 14 ms, τD = 8 ms). The as‐proposed self‐limited epitaxial growth method opens a new avenue to synthetize 2D nonlayered materials and will promote their further applications in novel optoelectronic devices. [ABSTRACT FROM AUTHOR]

Thin zinc-coated steel sheets are brazed together using a copper-silicon filler alloy and employing a gas metal arc process with dynamic control of current and voltage transients. The actual heat inputs for different wire feed rates during brazing were estimated from the recorded current and voltage transients. Lowering of heat input was aimed at to reduce the thermal distortion and the thickness of the interface layer with intermetallic compounds while ensuring a sound, continuous bead profile. The influence of overall heat input on the thermal distortion, joint strength and interface layer thickness is examined using Fourier number that depicts a ratio of the rate of heat dissipation to accumulation. An increase in brazing speed and a decrease in the wire feed rate resulted in reduced heat input, higher Fourier number, thinner interfacial layer and improved joint strength. The brazing induced thermal distortion reduced with increase in Fourier number. Irrespective of the sheet thickness, a range of Fourier number in between 0.22–0.26 provided brazed joint strength up to 96 % of that of the base metals with minimum interface layer thickness and thermal distortion. [ABSTRACT FROM AUTHOR]

An investigation on fast pattern calculation of rib reflectors is presented in this paper with varying surface distortions. In the beginning, a combined finite element meshing procedure is proposed by best-fit paraboloid and weighting feed primary pattern. An approximation formula for fast pattern calculation is derived on the basis of rib surface with a refocused feed and authors’ previous work. To show the effectiveness of the proposed method, a 0.5 m axis-symmetrical rib reflector at Ka-band for CubeSat application is employed. To further illustrate the benefits of fast pattern calculation, a time-varying distortion is introduced. By employing the proposed formula, less pattern computation time is obtained with an acceptable accuracy. Furthermore, incorporating structural parameters into this rib reflector, the structural dynamic deformation is demonstrated and its influence on radiation pattern is revealed. The results show that the proposed method can handle the varying distortions, which are in closed form or obtained from structural finite element analysis with a good accuracy by less computation time. [ABSTRACT FROM PUBLISHER]

This article investigates the macroscopic behavior of uniaxially pre-strained large-scale DP780 and CHSP45R sheet specimens. A novel grip system was designed for the pre-straining of the large tensile specimens. After this first loading, the uniformly strained gauge-section of the large-scale specimen was machined to smaller standard specimens. After pre-strain, further uniaxial tension tests at 45° and 90° from the pre-tensile direction, compression test and in-plane biaxial tension tests at 1:1, 2:1 and 1:2 force ratios were conducted. The flow curves and the instantaneous r-values of the pre-strained steel in the aforementioned uniaxial loading directions were compared with their monotonic response. In addition, the pre-strained compression test was incorporated to the π-plane at several incremental offset strains. The yield function- and isotropic hardening-based homogeneous anisotropic hardening (HAH) model (Barlat et al., 2014) was selected to predict the material response after non-linear strain path change. The Swift law characterized the isotropic hardening, while the Yld2000-2d anisotropic yield function (Barlat et al., 2003a) represented the yield locus. All the coefficients of the distortional plasticity model were manually determined and validated with an optimization algorithm. The HAH-predictions of the pre-strained flow curves and yield loci at several offset strains were in reasonable agreement with the experimental data, while the instantaneous r-value evolution was qualitatively well captured. [ABSTRACT FROM AUTHOR]

The surface distortion due to gravity can be minimized when the flexure is located at the mirror's neutral surface. When the mirror has relatively small surface curvature and simple lightweight structure, the location of neutral surface can be calculated by empirical formula or can approximately coincide with the mirror's center of gravity. Otherwise, it is insufficient to determine the exact location of neutral surface. In addition, when the torque stiffness of flexure cannot be neglected, the optimum mount location may deviate from neutral surface and should be determined by more sophisticated analysis. The RMS surface distortions will degenerate significantly when the flexure has deviations from the optimum axial mount location due to fabrication and assembly errors. The distortion sensitivity to support axial location is critical to achieving low surface distortions in practice. We demonstrate a method of calculating the exact location of neutral surface and optimum mount location. The sensitivity of surface distortion to support axial location is theoretically calculated and compared with the results obtained from finite element analysis. [ABSTRACT FROM AUTHOR]

The effectiveness of a simplified method for estimating an envelope curve of wrinkled-membrane-surface distortion, which was recently proposed by the author, was experimentally assessed. The equation is formulated using three physical quantities regarding wrinkles: the length of the wrinkle line, the major principal strain in wrinkled regions, and the in-plane shrinkage strain appearing in the orthogonal direction of the wrinkle line. Since these three physical quantities are attributed to two-dimensional problems, the formula makes it possible to simply estimate wrinkle amplitude without a cumbersome bifurcation analysis. Applying a wrinkle strain in tension-field theory instead of the in-plane shrinkage strain in the formula, a simplified method to estimate an envelope curve of a wrinkled membrane with a low computational cost was developed using the wrinkling analysis with tension-field theory. Wrinkling phenomena appearing on two membrane models subjected to an in-plane shear and a corner-tension load were experimentally measured by photogrammetry using the direct linear-transformation method and a laser-displacement sensor. The experiment model was then subjected to a finite element analysis using tension-field theory, and an envelope curve of the wrinkled membrane was estimated using the method. The estimated envelope curves appropriately captured the actual wrinkle amplitude appearing on the membrane surface regardless of the formation process of wrinkles. From the result, the validity of the proposed estimation method was confirmed. This paper offers an effective method to predict the magnitude of the wrinkled-membrane-surface distortion with a low computational cost, and will assist the development of future gossamer space structures incorporating membranes. [ABSTRACT FROM AUTHOR]

In high-power laser system, the surface wavefront of large optics has a close link with its structure design and mounting method. The back-support transport mirror design is presently being investigated as a means in China's high-power laser system to hold the optical component firmly while minimizing the distortion of its reflecting surface. We have proposed a comprehensive analytical framework integrated numerical modeling and precise metrology for the mirror's mounting performance evaluation while treating the surface distortion as a key decision variable. The combination of numerical simulation and field tests demonstrates that the comprehensive analytical framework provides a detailed and accurate approach to evaluate the performance of the transport mirror. It is also verified that the back-support transport mirror is effectively compatible with state-of-theart optical quality specifications. This study will pave the way for future research to solidify the design of backsupport large laser optics in China's next generation inertial confinement fusion facility. [ABSTRACT FROM AUTHOR]

Surface diagnosis methods based on phase retrieval algorithm have been successfully applied to many large reflector antennas. In the phase retrieval algorithm, surface distortion is retrieved by multiple far field patterns. The different far field patterns are connected to each other by an important element called 'phase factor'. This study investigates the effect of the phase factor on the phase retrieval algorithm. Generally, the phase factor is simple for the phase retrieval algorithm. In this study, a new method based on the active surface system is proposed to produce more flexible and diverse phase factors. Through digital simulations, the effect of different kinds of phase factors on the phase retrieval algorithm is discussed. In addition, the inaccuracy of the phase factor caused by the mechanism error is considered.. [ABSTRACT FROM AUTHOR]

In this work, we investigate the numerical convergence of a set of plasticity models with different kinematic and directional distortional hardening rules under cyclic plastic loading. In particular, we revisit the results presented in Feigenbaum et al. (2012) in order to more robustly check for convergence during the numerical integration procedure, and show that the results presented in the previous work do not converge. We investigate the role of the step-size and numerical scheme on the convergence of these models when predicting ratcheting. By reducing step-sizes and using a forward Euler scheme during numerical integration, converged solutions are obtained. The new converged results lead to new conclusions. Results still suggest that directional distortional hardening can improve ratcheting predictions, however the addition of directional distortional hardening yields less improvements compared to kinematic hardening alone than previously thought. This new conclusion, strongly suggests the need for additional modeling developments in order accurately predict ratcheting strains under a wide variety of cyclic plastic loadings. [ABSTRACT FROM AUTHOR]

The mechanic of TKA prosthesis in relation to prosthesis design remains unclear despite of previous extensive research. This study attempts to observe the stress states and contact mechanics of polyethylene (PE) insert of knee prosthesis during common daily activities and their relation with condylar and post-cam design. Knee joint loadings during walking, stair climbing, chair sitting and deep squatting were applied to Scorpio Superflex and Scorpio Non-Restricted Geometry (NRG) knee implants using 6-degree-of-freedom (DOF) displacement-force driven model. Finite element models were developed in FEMAP using tetrahedron elements while motions of knee joint were modelled in LS-DYNA. Design of Superflex serves relatively good conformity but more rotational resistance that leads to surface distortion. NRG, however, has more relaxed geometry without compromising the needs of appropriate conforming articular surfaces. This research demonstrated that PE tibial insert stress conditions are closely associated with condylar and post-cam geometry. Conforming interfaces serve good wear resistance, however provide surface constraint towards motion, which leads to surface distortion. [ABSTRACT FROM AUTHOR]

As an emerging type of optically active material, semiconductor nanocrystals (NCs) stabilized by chiral molecules have attracted much attention. Owing to the wide range of potential applications of chiral perovskite NCs, the development of these materials is of great importance, but there has been a lack of relevant studies. Here, we describe an investigation of the properties of chiral perovskite NCs obtained using post-synthetic ligand exchange (achiral ligand/chiral ligand). These are found to exhibit mirror-image circular dichroism spectra. It is the chirality of the ligand (enantiomeric 1,2-diaminocyclohexane, DACH) that is most likely responsible for the induction of chiroptical activity in these NCs. Furthermore, their chiroptical properties and the corresponding mechanisms are found to depend strongly on the amount of capping ligand. When excess DACH is used to cap the surface of the NCs, their chiroptical properties are induced mainly by aggregation of DACH on the surface in a chiral pattern. In contrast, when small amounts of DACH are used for the capping, it is mainly surface distortion (or defects) and electronic interaction mechanisms that contribute to the chiroptical behavior of the NCs. In both cases, the anisotropy factors of the NCs are of the order of 10-3, which is comparable to or larger than the values reported for other chiral semiconductor and metal NCs. This work opens the door toward further understanding of chiroptical perovskite NCs and their potential applications. [ABSTRACT FROM AUTHOR]

The incremental sheet forming processes (ISF) are attracting lots of attentions due to their advantages on rapid prototyping, without special dies and short lead time. The numerical simulation can be a valid method to investigate the forming process and predict the defects. In this study, an extended fully coupled ductile damage model with mixed nonlinear hardening was used to simulate the ISF process. At the same time, the yield surface distortion was also considered in this model, which can enhance the capability of modeling metallic material behavior under complex loading paths. Afterwards, some simulations were conducted with the proposed model. Additionally, one tension-shear orthogonal loading test was assigned on the one representative element in order to investigate the loading path effect during ISF process. By comparing the equivalent plastic strain and ductile damage evolution of the blank, the influence of the yield surface distortion on the ISF process was proved. [ABSTRACT FROM AUTHOR]

This paper deals with the numerical simulation of sheet metal blanking process based on fully coupled elastoplastic model accounting for the induced anisotropies due to the kinematic hardening and the yield surface distortion. The yield surface distortion is assumed to be controlled by the kinematic hardening leading additional extra hardening which enhances the predictive capabilities of the model. Series of finite element-based numerical simulations of blanking process with four kinds of assumed distortional hardening parameters have been conducted. Through the comparison between the experimentally observed responses and the numerically predicted ones with and without the yield surface distortion effect, the significance of the yield surface distortion-induced anisotropy on the estimation of the blanking edge quality has been investigated. [ABSTRACT FROM AUTHOR]

The method of determining the accuracy of polymer molds in plaster forms has been discussed. Distortion of the surface of molds and plaster molds has been assessed. It has been found that the presence of monolithic and porous structure in the samples does not change the accuracy of the surfaces when forms are prepared for removing the material of the model. It has been found that in case of full-mold casting it is more expedient to form the mold cavity with cellular adjustable structures of molding prototypes. [ABSTRACT FROM AUTHOR]

In roll forming a wide flat channel, problems were experienced with wrinkling, or 'oil canning' in the web. This is a common shape problem in roll forming wide panels that have flat regions in the profile. Coils from four different suppliers were used in production; with three of these, wrinkling could be controlled, but one coil had to be discarded. Tensile tests performed on all materials did not identify major differences in the coils although one material showed a slight indication of ageing. Free bending tests were performed with a new stand-alone bend tester specifically developed for material characterisation on the shop floor. The bending tests performed on strips cut in the longitudinal direction showed a greater difference between coils; the material giving unacceptable wrinkling had a significantly higher moment curvature characteristic indicating substantial ageing. All materials showed some coil set and the bending properties depended on the direction in which the specimen was bent, i.e. in the same or opposite direction to the coil set. A finite element analysis was performed on the process which indicated significant plastic deformation in the flange, but very little in the web. Possible links between the unusual bending behaviour and oil canning in the web are suggested and the work indicates the desirability of performing free bending tests in addition to the customary tensile testing in roll forming applications. [ABSTRACT FROM AUTHOR]

A GPU-based DEM modeling methodology with rolling resistance is employed to study comprehensively dip-slip faulting through granular soils from both engineering and fundamental viewpoints. From engineering viewpoints, the results of engineering significances, including the ruptures path, the fault outcropping location, the ground surface distortion zone, the near surface stress path within the rupture and the fault outcropping strain are studied. From fundamental viewpoints, the orientation of the ruptures (shear bands) is discussed using the Roscoe theory. The analyses show that the fault ruptures deviate from the fault projection surfaces as propagating up toward the ground surface; the deviation depends on the faulting type, faulting angle and soil density. The reverse ruptures may deviate from the fault projection surfaces toward the hanging wall or foot wall, depending on the fault dip angle; however, both primary and secondary normal ruptures refract at the soil-bedrock interface, deviating toward the hanging wall. In addition, the analyses show that by increasing the fault dip angle, the slopes of the near surface stress paths within the reverse ruptures increase from about the slope of the biaxial compression stress path to about that of the p-constant stress path (compressional regime); conversely, these slopes within the normal ruptures decrease from about the slope of the biaxial extension stress path to about that of the p-constant stress path (extensional regime). Moreover, the analyses show that the fault outcropping strains of reverse faulting are comparatively higher than those of normal faulting. In addition, the fault outcropping strains are proportional to the soil ductility. From fundamental viewpoints, the analyses show that all of the reverse and normal fault ruptures through the denser and looser sands do propagate in parallel with zero-extension lines of the localized areas located along the ruptures paths, provided that the variations of the maximum principal strain directions and dilatancy rates along the ruptures are taken into account; this is in accord with the Roscoe theory. [ABSTRACT FROM AUTHOR]

In metal forming, material points are often subject to complex loading paths even if the applied loading imposed by the forming tools is simple monotonic loading paths. Including the yield surface distortion effect in constitutive equations is expected to highly enhance the capability of the model in simulating the material forming behavior under complex loading paths. In the present work, fully coupled anisotropic constitutive equations with mixed isotropic and kinematic nonlinear hardening strongly coupled with isotropic ductile damage are improved, considering the subsequent yield surfaces distortion. A model based on the framework of non-associative plasticity theory has been developed recently. In this model, a distortion stress tensor S ̲ d replaces the usual deviator stress tensor S ̲ in the yield criterion and dissipation potential. Three parameters X l 1 c , X l 1 p , and X l 2 are introduced in the coupled constitutive equations, to be used to control the subsequent yield surfaces distortion. This model is applied and compared with the experiments specifically performed for that purpose. Series of experiments are conducted using the material AL7020 to identify and validate the proposed model. Through the combined loading tests performed on Twente biaxial testing machine, the results of non-proportional loading paths demonstrate that the proposed model can fully represent the forming behavior when complex loading paths. The influence of the yield surface distortion on the plastic flow and on the ductile damage evolution is also discussed in this study. [ABSTRACT FROM AUTHOR]

Correct determination of ratcheting strain is very important in cyclic loading. A new simple yield surface distortion model is presented and its effect on cyclic loading and ratcheting prediction is investigated in this research. Model of Baltov and Sawczuk was modified in order to be able to consider directional distortion of the yield surface. Movement of the yield surface center is modeled by Chaboche's nonlinear kinematic hardening model. Isotropic hardening was also considered. A triangular function is used and necessary cyclic plasticity relations are developed. Convexity of the proposed model is discussed and verified. Performance of the proposed model in ratcheting strain prediction is investigated in multiaxial non proportional loadings under different paths. Experimental results with stress, strain and combined stress-strain control paths are compared with the proposed model results. Incorporation of the yield surface distortion of this new model, predicts better ratcheting strain for different stress, strain and stress-strain paths. [ABSTRACT FROM AUTHOR]

The introduction of the kinematic hardening induced distortion of the yield surface is expected to enhance the capability of the model in simulating the material behavior under complex loading paths occurring during sheet metal forming processes.In this work non-associative elastoplastic anisotropic constitutive equations accounting for mixed nonlinear hardening and fully coupled with isotropic ductile damage, is improved by considering the distortion of the yield subsequent surfaces. A convenient “distortion” deviatoric stress tensor S ̲ d is used in both yield criterion and plastic potential instead of the usual classical deviatoric stress tensor S ̲ . Accordingly, the yield surface distortion is controlled by three adequate material parameters named X l 1 c , X l 1 p and X l 2 c . A parametric study is conducted under simple loading paths (tension and torsion) in order to explore the capabilities of the model in describing the yield surface distorsion. Comparisons with experimental results on aluminum alloy, taken from the literature, are also given. Moreover, the influence of the subsequent yield surfaces distortion under complex non-proportional loading paths on the evolution of the plastic flow with hardening and the ductile damage are also discussed and highlighted. [ABSTRACT FROM AUTHOR]

It is very important to measure fabric wrinkling objectively and accurately. However, the most commonly used measurements could not be employed to realistically evaluate and predict how fabric will resist wrinkle when worn on human body. In our previous study, an equipment of measuring fabric wrinkling that can simulate actual wear was proposed. In this paper, we conduct further investigation on the measurement for fabric wrinkle-simulating actual wear, including improving the equipment, validating its repeatability, and clarifying its more accurate relationship with the wrinkle recovery angle (WRA) method. Results show that the measuring repeatability of the method is much better than WRA method and fabric wrinkling in the warp and bias direction plays more important part than weft. Therefore, it is advisable that WRA of the bias should be increased, whose measurement stability is the best in the WRA method as well. Equations of Wrinkle Density (WD) with WRAs are established, which can be used to estimate wrinkling of clothes after actual wear only by several WRAs of fabrics, avoiding the tedious clothes making and trial work. [ABSTRACT FROM AUTHOR]

Since manually straightening the deformed parts which were disassembled from end of life product is less efficiency, the automatic straightening technology is required. But currently only a few type of parts with regular cross sections can be deal with analytic approach, while others with irregular or complex cross sections can not be deduced using analytic model by elastic-plastic mechanics approach. This paper proposes an equivalent modeling approach for changing the part with complex cross sections into a simplified model with rectangular cross sections, thus the model of reverse-bending parameter for straightening equipment is obtained. Finally, the freely supported uniform beam and non-uniform beam are studied for straightening parameter. [ABSTRACT FROM AUTHOR]

Runway surface distortions such as rutting allow water to accumulate on the runway surface which may cause aircraft operational risks related to hydroplaning and loss of friction. This may increase the runway excursion risk during wet weather conditions. Several standards relating to airfield pavement maintenance have documented that rutting can cause safety hazards to aircrafts due to hydroplaning risk. This paper proposes an analytical approach to evaluate the hydroplaning potential for aircrafts due to the flooded ruts of a runway pavement and evaluate the operational risk. A finite element model is developed to simulate aircraft tyre hydroplaning under given set of operating conditions. By performing this evaluation for different rut depths, an assessment of the relative severity levels of different rut depths with respect to hydroplaning can be made. A numerical example is presented to illustrate the application of the procedure to evaluate operational risks to aircraft from runway rutting. [ABSTRACT FROM AUTHOR]

Surface distortions change the radiation characteristics of reflector antennas. Using functional calculus, radiation integral is analyzed, and the first variational derivative (VD) of the radiation field with respect to surface profile is extracted. The VD can show the radiation pattern sensitivity to surface distortion. All formulations are based on the physical optics approximation. The final formula for VD depends only on the original undistorted antenna parameters, so it can be used for all types of distortions. It has been shown that the formulations are more general than those in previous works. Different polarization states of feed antenna are studied, and VD amplitudes are plotted to depict the regions that have greater effects on the main-lobe and the first few side-lobes levels. Some periodic, aperiodic, and local distortion profiles are considered, and the exact and approximated distorted patterns are compared to check the accuracy of the presented procedure. [ABSTRACT FROM PUBLISHER]

We dedicate this paper to the investigation of certain special types of geophysical water flows arising in the equatorial ocean which are driven by gravity and surface tension. To be more specific, we consider steady flows–written in cylindrical coordinates–which are moving in the azimuthal direction, with no variation in this direction, and which exhibit a vertical structure and allow for a surface distortion. Using a functional analytic approach we prove that any small deviation of the pressure function from the pressure required to maintain the free surface flat and undisturbed gives rise to a genuine wave solution. [ABSTRACT FROM AUTHOR]

Explicit expressions are derived for the matrices determining the mean translational and rotational swimming velocities and the mean rate of dissipation for Stokesian swimming at low Reynolds number of a distorting sphere in a viscous incompressible fluid. As an application, an efficient helical propeller-type stroke is found and its properties are calculated. [ABSTRACT FROM AUTHOR]

Ultrafast X-ray diffraction experiments require careful adjustment of the spatial overlap between the optical excitation and the X-ray probe pulse. This is especially challenging at high laser repetition rates. Sample distortions caused by the large heat load on the sample and the relatively low optical energy per pulse lead to only tiny signal changes. In consequence, this results in small footprints of the optical excitation on the sample, which turns the adjustment of the overlap difficult. Here a method for reliable overlap adjustment based on reciprocal space mapping of a laser excited thin film is presented. [ABSTRACT FROM AUTHOR]

In this study, a yield surface distortion model coupled with nonlinear kinematic hardening model is proposed. The new yield surface distortion model is used to simulate proportional and non-proportional cyclic loading paths. Distortion of the yield surface and its nonlinear effects on the plastic flow have been studied by researchers and various models. However, these models have been rarely applied to different non-proportional cyclic loading paths. The yield surface evolution is obtained by the new model in cyclic loading and its results are compared with the experimental results of Dannemeyer [30] . The new model with few constants predicts well the yield surface evolution under non-proportional loading paths which leads to well comparison of the numerical results with respect to the experimental results. [ABSTRACT FROM AUTHOR]

Detecting anomalies before an earthquake has become an important task in seismic hazard prevention. The purpose of this research is to use the intrinsic attenuative dispersion of the P-wave, Qp, to serve as an anomaly before an earthquake. On November 5, 2009, an earthquake ( M L = 6.2; depth = 24 km) occurred in Ming-Jen, Nantou county, Taiwan. The vertical-component of the first-cycle of P-wave data recorded from the Central Weather Bureau Seismic Network from 2009/01 to 2010/01 was calculated to obtain the Qp parameter. Meanwhile, this study also utilizes global positioning system stations to examine changes in surface displacements that occurred during the Mingjen earthquake. Analysis results indicate that 2-months before the mainshock occurred; the Qp began to decrease for all stations, which implies that the crustal area became more fractured owing to a high stress accumulation. Such a lead time of ∼2 months is equal to the average lead time of Seismic Electric Signals (SES) activities being also compatible with a physical model suggested long ago for the SES generation. With stress accumulating a few days before the earthquake, an impeded region can be clearly identified by relatively-large difference values when the mainshock is going to occur. We conclude that the analysis of the Qp parameter and GPS index are very sensitive to changes in the stress state and may serve as a useful index in early warning of earthquake. [ABSTRACT FROM AUTHOR]

[Display omitted] • We explore the limitations of LiMn 2 O 4 cathode material at high cut-off voltage. • Presents the key strategies to improve the performance under high cut-off voltage. • The developments of electrolyte for high voltage are also particularly reviewed. The growing demand for high energy and power density in lithium-ion batteries mandates the utilization of cathode material with improved capacity and output voltage. Among various cathode materials, spinel structured lithium manganese oxide stands out for its acceptable energy density, high working voltage, excellent safety, and cost-effectiveness. Extending the upper cut-off voltage of cathode materials is realized to be a convenient way of increasing the energy density of lithium-ion batteries. Nevertheless, as charging to a higher voltage (>4.3 V vs Li/Li+), several derogatory issues such as surface distortions, the interfacial reaction between cathode and electrolyte, and stress-induced cracking could emerge, leading to a rapid decline in capacity and cycle life. This review summarizes the failure mechanism of LiMn 2 O 4 , focusing on high voltage stability. Additionally, various modification strategies, such as doping and surface coating, are proposed to acquire high-voltage LiMn 2 O 4. We also discuss prominent modification approaches for structural or electrolytes, such as concentration-gradient design, electrolyte additives, and solid-state electrolytes. [ABSTRACT FROM AUTHOR]

The relation between stress and temperature in polymer composite materials was derived based on the energy conservation law. For the qualitative experiment, glass-fiber-reinforced plastic specimens were heat treated to produce surface strain, thereby completely releasing the stress in the material. The presence of surface distortion qualitatively confirmed the relation between stress and temperature, thereby confirming the underlying physical mechanism of the relation. A case study was undertaken to measure the surface strain for quantitative confirmation of the relation between temperature and stress. This study established the equation based on physical parameters for the quantitative measurement of the relation between the temperature and the stress and strain. Despite the experimental error, objective and meaningful experimental results can be obtained using our measurement approach for a variety of composite materials. [ABSTRACT FROM AUTHOR]