Distortion Analysis Method Research Articles

Distortion Analysis Method for Wire Arc Additive Manufacturing Component Using Thermomechanical Computation with Enhanced Separation and Deposition Algorithm.

This research is devoted to numerical and experimental analysis on deformation of completely removed component induced by wire arc additive manufacturing (WAAM). The component has the form of a hollow and rectangular thin wall made of deposition layer of stainless steel SS316L on top of substrate plate of mild steel S235. In this research, thermomechanical finite element analysis was applied with Goldak's double ellipsoid as heat-source model and isotropic hardening rule based on von-Mises yield criterion. A specialized numerical simulation software Simufact.Welding 2021 (SW) was utilized in developing the numerical model and the simulation of process enhanced with separation and deposition algorithm to predict the component deformation after removal of substrate. On determining the best possible mesh size, a sensitivity analysis was conducted before the advanced stage of model development. An advanced material modeling, the data of which were obtained based on the chemical composition of the evolved SS316L sample, was developed using an advanced material modeling software JMATPRO. For verification purpose, a series of WAAM experiments using robotic GMAW with synergic power source were conducted followed by the removal of substrate from component using machining process. Furthermore, component distortion was measured using industrial noncontact 3D scanner with structured blue light to fully capture the upper section deformation and compared with result of numerical computation. It can be concluded that this novel distortion analysis method using thermomechanical numerical computation with evolved material property and modified algorithms for substrate removal exhibits a surface deviation in vertical direction between 0.05 and 2.16 mm with acceptable pointwise and average error percentage of up to 3%.

Mains Current Distortion Analysis and Suppression Method for Third-Harmonic Injection Two-Stage Matrix Converter

Compared with the direct matrix converter and the two-stage matrix converter (TSMC), the third-harmonic injection TSMC (3TSMC) has significant advantages in the input reactive power control range and the maximum linear voltage transfer ratio. However, for nonunity input power factor operations and high-mains-frequency applications, there are input current distortions in the 3TSMC. Further analysis reveals that the actual injection current cannot track the reference without error in the conventional harmonic current injection circuit, resulting in the current distortions. Therefore, an improved circuit is proposed, which is based on the asymmetric H-bridge and does not need extra energy storage components or current sensors. The injection current in the improved circuit can follow the reference without error by injection current modulation, which means that the input current distortions are suppressed significantly. All theoretical considerations are verified by experimental results taken on a 3-kVA prototype.

Distortion Evaluation of EMP Sensors Using Associated-Hermite Functions

Electromagnetic pulse (EMP) is a kind of transient electromagnetic phenomenon with short rise time of the leading edge and wide spectrum, which usually disrupts communications and damages electronic equipment and system. It is challenging for an EMP sensor to measure a wideband electromagnetic pulse without distortion for the whole spectrum. Therefore, analyzing the distortion of EMP measurement is crucial to evaluating the sensor distortion characteristics and correcting the measurement results. Waveform fidelity is usually employed to evaluate the distortion of an antenna. However, this metric depends on specific signal waveforms, thus is unsuitable for evaluating and analyzing the distortion of EMP sensors. In this paper, an associated-hermite-function based distortion analysis method including system transfer matrices and distortion rates is proposed, which is general and independent from individual waveforms. The system transfer matrix and distortion rate can be straightforwardly calculated by the signal orthogonal transformation coefficients using associated-hermite functions. Distortion of a sensor vs. frequency is then visualized via the system transfer matrix, which is convenient in quantitative analysis of the distortion. Measurement of a current probe, a coaxial pulse voltage probe and a B-field sensor were performed, based on which the feasibility and effectiveness of the proposed distortion analysis method is successfully verified.

Evaluating and Analyzing the Potential of the Gaofen-3 SAR Satellite for Landslide Monitoring

Gaofen-3 is the first Chinese spaceborne C-band SAR satellite with multiple polarizations. The Gaofen-3 satellite’s data has few applications for monitoring landslides at present, and its potential for use requires further investigation. Consequently, we must evaluate and analyze the landslide interference quality and displacement monitoring derived from the Gaofen-3 SAR satellite’s data, particularly in high and steep, mountainous regions. Based on the nine Gaofen-3 SAR datasets gathered in 2020–2021, this study used DInSAR technology to track landslide displacement in Mao County, Sichuan Province, utilizing data from Gaofen-3. Our findings were compared to SENTINEL-1 and ALOS-2 data for the same region. This study revealed that due to its large spatial baseline, Gaofen-3’s SAR data have a smaller interference effect and weaker coherence than the SENTINEL-1 and ALOS-2 SAR data. In addition, the displacement sensitivity of the Gaofen-3 and SENTINEL-1 data (C-band) is higher than that of the ALOS-2 data (L-band). Further, we conducted a study of observation applicability based on the geometric distortion distribution of the three forms of SAR data. Gaofen-3’s SAR data are very simple to make layover and have fewer shadow areas in hilly regions, and it theoretically has more suitable observation areas (71.3%). For its practical application in mountainous areas, we introduced the passive geometric distortion analysis method. Due to its short incidence angle (i.e., 25.8°), which is less than the other two satellites’ SAR data, only 39.6% of the Gaofen-3 SAR data in the study area is acceptable for suitable observation areas. This study evaluated and analyzed the ability of using Gaofen-3’s data to monitor landslides in mountainous regions based on the interference effect and observation applicability analysis, thereby providing a significant reference for the future use and design of Gaofen-3’s data for landslide monitoring.

Analysis of potential distortions corresponding to the hologram printed by a holographic wave-front printer.

In this paper, potential distortions corresponding to the hologram printed by a holographic wave-front printer are analyzed. Potential distortions are classified as the magnification(demagnification) distortion, barrel distortion, pincushion distortion, SLM mounting distortion, and translation distortion, respectively. These distortions are grouped as the optics distortion, SLM mounting distortion and the translation distortion depending on the process of recording the hologram in the holographic wave-front printer. In order to evaluate each distortion, a distortion analysis method based on a local spatial frequency is proposed. Through the proposed method, a diffracted wavefield reconstructed from a quantitatively distorted hologram is theoretically analyzed, and the validity of this analysis is verified by applying the numerical reconstruction method. In the numerical reconstruction, a propagation of a distorted wavefield reconstructed from the quantitatively distorted hologram is confirmed and contributed to generate the distorted reconstruction plane, such as a focal cloud plane and a convergence plane, depending on the types of distortion.

Novel welding distortion analysis method for large welded structures using orthotropic thermal expansion coefficients

Abstract This paper proposes an effective numerical method to predict welding distortion for large welded structures. To predict welding distortions, inherent strain-based methods are computationally efficient and widely used in engineering fields. However, there are some drawbacks such as the generation of undesirable longitudinal forces and the use of vector-type input variables. Equivalent loads are derived through finite element formulation considering orthotropic thermal expansion conditions. Unlike previous methods, the proposed method predicts transverse shrinkage and angular distortion accurately, removing the undesirable longitudinal forces. In addition, scalar-type input variables are employed, which results in a convenient design procedure. The performance of the proposed method is verified through various examples including complex and large welded structures.

An analytical gm/ID‐based harmonic distortion prediction method for multistage operational amplifiers

SummaryAn analytical stage‐based harmonic distortion (HD) analysis method for multistage operational amplifiers (Op Amps) is developed in this work. This work contributes two fundamental methods that make the analytical HD prediction possible at the circuit level. Firstly, we propose that the traditionally used first order small‐signal transistor quantities gm (transconductance) and go (output conductance) in the gm/ID design methodology for bulk complementary metal‐oxide‐semiconductor (CMOS) technology can be extended to the higher order quantities gm(k) and go(k) ( ). With proper normalization, these quantities become neutral to the device dimensions and operation currents, hence can be precharacterized by sweeping simulations and used as lookup tables. Secondly, we further develop analytical nonlinearity expressions for a set of commonly used amplifier stages, represented as the functions of the nonlinearity parameters gm(k) and go(k) of the transistors that form a stage circuit. A combination of these two fundamental methods on hierarchical nonlinearity modeling enables us to apply the existing analytical HD estimation methods for the stage‐form macromodels to predict the circuit‐level HD behavior, overcoming the need of running repeated simulations under device resizing and rebiasing. The proposed harmonic distortion analysis method has been validated by application to real multistage amplifiers, achieving HD prediction results in excellent agreement to fully transistor‐level circuit simulation results but with substantial speedup.

New Arc Stability Index for Industrial AC Three-Phase Electric Arc Furnaces Based on Acoustic Signals.

This research proposes a new index to evaluate the stability of the melting process, in three-phase electric arc furnaces (EAFs), based on the acoustic signals generated during the different stages of the casting. The proposed stability index is obtained by characterizing the time and frequency domain of the acoustic signals. During EAF monitoring, acoustic signals were acquired using a microphone coupled to an NI USB-9234 acquisition system. To validate the results, the voltage and current signals were measured with the aid of a Circutor AR6 power analyzer for three-phase electrical networks. The results showed that the acoustic signal energy in the frequency range of 1 to 12 kHz can be used as an indicator of the process stability in the EAF. Finally, the validity of the proposed stability index is evaluated from the process characterization using the harmonic distortion analysis methods and the dynamic U-I characteristics of the arc voltage and current signals. The results obtained demonstrated the effectiveness of the proposal and constitute a starting point for advances in the automatic control of the process in the EAF, from the acoustic signals.

Using the Method of Harmonic Distortion Analysis in Partial Discharge Assessment in Mineral Oil in a Non-Uniform Electric Field

In high-voltage equipment, it is vital to detect any failure in advance. To do this, a determination of the partial discharges occurring at different voltage types as well as at different electrode configurations is essential for observing the oil condition. In this study, an experimental setup consisting of a needle–semi-sphere electrode configuration immersed in mineral oil is prepared for laboratory experiment. In such a way, a non-uniform electric field is created and the leakage currents are monitored from the grounded electrode. A total of six different electrode configurations are analyzed during the tests by the use of hemispheres of different diameters as grounded electrodes and copper and steel pointed (medical) needle high-voltage electrodes. In the experiments, the partial discharges occurring at four different voltage levels between 5.4 and 10.8 kV are measured and recorded. The effect of the different electrode configurations and voltage levels on the harmonic distortion are noted and discussed. It is experimentally confirmed that it is possible to measure the leakage current caused by the partial discharges of the corona type in oil at the different metal points, creating high-voltage electrodes and different electric field distributions based on the proposed non-invasive measurement technique. The studies showed that there is a significant rise of even harmonic components in the leakage current during the increase in the partial discharge intensity with the 5th harmonic as dominant.

Appraisal of magnetotelluric galvanic electric distortion by optimizing amplitude and phase tensor relations

The introduction of the phase tensor marked a major breakthrough in the analysis and treatment of electric field galvanic distortion in the magnetotellurics method. Recently, the phase tensor formulation has been extended to a complete impedance tensor decomposition by introducing the complementary amplitude tensor, and both tensors can be further parameterized to represent geometric properties such as dimensionality, strike angle, and macroscopic anisotropy. Both tensors are characteristic for the electromagnetic induction phenomenon in the conductive subsurface with its specific geometric structure. The central hypothesis is that this coupling should result in similarities in both tensor’s geometric parameters, skew, strike, and anisotropy. A synthetic example illustrates that the undistorted amplitude tensor parameters are more similar to the phase tensor than increasingly distorted ones and provides empiric evidence for the predictability of the proposed hypothesis. Conclusions drawn are reverse engineered to produce an objective function that minimizes when amplitude and phase tensor parameter dissimilarity is, along with any present distortion, minimal. A genetic algorithm with such an objective function is used to systematically seek the distortion parameters necessary to correct any affected amplitude tensor and, thus, impedance data. The successful correction of a large synthetic impedance data set with random distortion further supports the central hypothesis and serves as comparison to the state-of-the-art. The classic BC87 data set sites lit007/ lit008 and lit901/ lit902 have been noted by various authors to contain significant distortion and a 3D regional response, thus invalidating current distortion analysis methods and eluding geologic interpretation. Correction of the BC87 responses based on the present hypothesis conforms to the regional geology.

Efficient welding distortion analysis method for large welded structures

An efficient approach to predicting the welding angular distortion of large structures by using scalar input variables with no restriction on the mesh size near the welding region is proposed. To transform the input variables according to the mesh size, the explicit form of the force matrix is derived based on finite element theory. The proposed method is easily applied and requires only the measured distortion rate of a unit welded specimen and a user-designed mesh system to conduct the welding distortion analysis. The proposed method was applied to various case studies for verification, and the results show that the proposed method can effectively predict the welding angular distortion.

Ellipsoidal analysis of coordination polyhedra

The idea of the coordination polyhedron is essential to understanding chemical structure. Simple polyhedra in crystalline compounds are often deformed due to structural complexity or electronic instabilities so distortion analysis methods are useful. Here we demonstrate that analysis of the minimum bounding ellipsoid of a coordination polyhedron provides a general method for studying distortion, yielding parameters that are sensitive to various orders in metal oxide examples. Ellipsoidal analysis leads to discovery of a general switching of polyhedral distortions at symmetry-disallowed transitions in perovskites that may evidence underlying coordination bistability, and reveals a weak off-centre ‘d5 effect’ for Fe3+ ions that could be exploited in multiferroics. Separating electronic distortions from intrinsic deformations within the low temperature superstructure of magnetite provides new insights into the charge and trimeron orders. Ellipsoidal analysis can be useful for exploring local structure in many materials such as coordination complexes and frameworks, organometallics and organic molecules.

Computation and visualisation of the accuracy of old maps using differential distortion analysis

ABSTRACTThe accuracy of old maps can hold interesting historical information, and is therefore studied using distortion analysis methods. These methods start from a set of ground control points that are identified both on the old map and on a modern reference map or globe, and conclude with techniques that compute and visualise distortion. Such techniques have advanced over the years, but leave room for improvement, as the current ones result in approximate values and a coarse spatial resolution. We propose a more elegant and more accurate way to compute distortion of old maps by translating the technique of differential distortion analysis, used in map projection theory, to the setting where an old map and a reference map are directly compared. This enables the application of various useful distortion metrics to the study of old maps, such as the area scale factor, the maximum angular distortion and the Tissot indicatrices. As such a technique is always embedded in a full distortion analysis method we start by putting forward an optimal analysis method for a general-purpose study, which then serves as the foundation for the development of our technique. Thereto, we discuss the structure of distortion analysis methods and the various options available for every step of the process, including the different settings in which the old map can be compared to its modern counterpart, the techniques that can be used to interpolate between both, and the techniques available to compute and visualise the distortion. We conclude by applying our general-purpose method, including the differential distortion analysis technique, to an example map also used in other literature.

Simplified welding distortion analysis for fillet welding using composite shell elements

This paper presents the simplified welding distortion analysis method to predict the welding deformation of both plate and stiffener in fillet welds. Currently, the methods based on equivalent thermal strain like Strain as Direct Boundary (SDB) has been widely used due to effective prediction of welding deformation. Regarding the fillet welding, however, those methods cannot represent deformation of both members at once since the temperature degree of freedom is shared at the intersection nodes in both members. In this paper, we propose new approach to simulate deformation of both members. The method can simulate fillet weld deformations by employing composite shell element and using different thermal expansion coefficients according to thickness direction with fixed temperature at intersection nodes. For verification purpose, we compare of result from experiments, 3D thermo elastic plastic analysis, SDB method and proposed method. Compared of experiments results, the proposed method can effectively predict welding deformation for fillet welds.

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N2atmosphere

A rhombohedral analysis method for analysing the lattice distortion in a (111)-textured face-centred cubic film under rotationally symmetric stress is proposed. Because no material constants, such as diffraction elastic constants, are required, the expressions of the distortion, namely the angle and the lattice parameter, are universal and can be readily used to compare different films. Using this rhombohedral distortion analysis method, (111)-textured Pt films deposited under argon–nitrogen atmosphere are systematically investigated, and the thickness-dependent lattice deformation in as-deposited and annealed films is described by the two geometrical parameters of the rhombohedral cell.

Distortion analysis of magnetic excitation—a novel approach for the non-destructive microstructural evaluation of ferromagnetic steel

The presence of a different ferromagnetic material, between the poles of a U-shaped iron-cored electromagnetic (EM) yoke, has been observed to introduce a distortion in the alternating excitation voltage (VE) across the coil around the EM yoke. The influence of four different microstructural conditions of a ferromagnetic 18CrNiMo5 gear steel on the distortion behaviour of the magnetic excitation voltage has been investigated. The time derivative of the excitation voltage (dVE/dt) plotted as a function of total applied voltage (VT) has been found to show a unique shape for each sample with different microstructural conditions. The systematic changes in the height and position of the peak and the trough on the voltage–time derivative profile reflect the difference in the magnetization process for each microstructural condition. This study reveals the good potential of this simple method of distortion analysis of magnetic excitation for a variety of applications related to material evaluation of ferromagnetic steel components.

An Improved Plasticity-Based Distortion Analysis Method for Large Welded Structures

The plasticity-based distortion prediction method was improved to address the computationally intensive nature of welding simulations. Plastic strains, which are typically first computed using either two-dimensional (2D) or three-dimensional (3D) thermo-elastic-plastic analysis (EPA) on finite element models of simple weld geometry, are mapped to the full structure finite element model to predict distortion by conducting a linear elastic analysis. To optimize welding sequence to control distortion, a new theory was developed to consider the effect of weld interactions on plastic strains. This improved method was validated with experimental work on a Tee joint and tested on two large-scale welded structures—a light fabrication and a heavy fabrication—by comparing against full-blown distortion predictions using thermo-EPA. 3D solid and shell models were used for the heavy and light fabrications, respectively, to compute plastic strains due to each weld. Quantitative comparisons between this method and thermo-EPA indicate that this method can predict distortions fairly accurately—even for different welding sequences—and is roughly 1-2 orders of magnitude faster. It was concluded from these findings that, with further technical development, this method can be an ideal solver for optimizing welding sequences.

The Volterra series of distortion analysis

The Volterra series method of distortion analysis is presented in the analysis of a common emitter circuit. There are presented the model of the integrated circuit and evaluated their non-linearity’s.According to the provided equivalent diagram and using the method of Volterra series, kernels of the respective linear, square and cube system have been figured out. Changes in an operation mode ofa IT within a frequency range influenced by an input signal have been defined taking into account IT parameters and outer elements.

WSN Data Distortion Analysis and Correlation Model Based on Spatial Locations

In wireless sensor networks (WSN), sensor nodes are densely deployed for environmental monitoring, the network runs under the cooperation between nodes . O ne of the most significant characteristics of WSN is the instability of wireless communication link and multi-hop transmission process, so that it is very tendentious to receive the distorted information of the source by the terminal node. To reconstruction the source of the original physical phenomenon is an important technical work. This paper proposed a method of WSN data distortion analysis based on spatial locations according to the most universal mode of omnidirectional Boolean sensing. Moreover, for extracting the data correlation in distortion function, a model of data correlation is also proposed. Both analysis and simulation results show the effectiveness of the the distortion function and correlation model, and by modifying the control parameter, the accuracy of the model is also be proved.

다층 맞대기용접의 쉘 요소 기반 변형해석법 개발

Ship Blocks are assembled by welding, and among them, welding between large blocks (Pre-erection stage) is used as feature of butt. In this process, local material has a experience of thermal cycle and become finally shrunk. As for inconsistency of shrunk weldments and adjacent regions, ship structure would be deformed locally and globally. Thermal distortion analyses are done for control of these processes, and methodologies capable of ship block size among them are using 2-D shell element in FEM. A shell element takes charge of plate, so it has its thickness which is important for angular distortion by welding. By the way, a butt-welding consists normally of several passes, and weldment thickness are different at each pass. If a calculated final one-time welding shrinkage is acting on the shell element whose thickness is same as it of plate, then deformation value must be underestimated. This research developed a methodology that total deformation after multi-pass welding can be analyzed by one time at shell element having original thickness of its plate. We use the SDB thermal distortion analysis method and verified by several experiment. The both experimental and analysis results showed good agreements.