Adjacent Passes Research Articles

Numerical investigation on machining of additively manufactured CFRP composite with different build orientations and layer widths

Additive manufacturing (AM) is now a widely researched manufacturing technology in the past two decades to adopt in industry for its added advantage of customization and adopting complex geometries with comparatively low buy-to-fly ratio. Carbon fiber reinforced polymer (CFRP) composite has found applications in different high-performance industries for its greatest benefit of high strength-to-weight ratio. Additive manufacturing of CFRP composite (AM-CFRP) opens up the possibility of enhancing mechanical strength using different printing orientations and enables producing complex shapes maintaining sustainable manufacturing perspective. However, Limitation of AM parts of having surface irregularities and questionable dimensional accuracies. To use AM-CFRP parts in high precision assembly or industrial applications, post processing machining is often required to meet the customers’ specification of geometrical tolerances and acceptable surface finish. In this study, the influence of AM parameters on machinability of AM-CFRP composite has been evaluated using finite element analysis (FEA) based numerical simulation. The slot milling operation was simulated with a tungsten carbide end milling tool and AM-CFRP workpiece with four different printing directions, i.e., 0°-90°, 45°-135°, 0°-90°-45°-135°, two different layer widths, i.e., 50 µm and 100 µm, and two in-fill patterns, i.e., solid and perforated structures. The machinability of the 3D printed CFRP has been analyzed based on cutting forces, stress at first contact and maximum stress generation, and temperature increases at the interface during slot milling of AM-CFRP under different AM parameters. Evolution of failure mechanisms of AM-CFRPs under various machining conditions, such as, delamination, matrix rupture etc., have been discussed and chip and burr formation mechanisms have been analyzed. Finite Element analysis (FEA) package ABAQUS/Explicit was used to model 3D micro slot milling operation of AM-CFRP workpiece with appropriate damage and constitutive models, such as, damage initiation, progression and cohesion in adjacent passes and layers.

Topography prediction of high-aspect ratio features milled with overlapping abrasive slurry jet footprints considering fluid confinement effects

Overlapping adjacent passes of abrasive slurry jets can be used to fabricate micro-pockets or blind micro-slots. This study investigates the propagation of surfaces milled using overlapping passes of a high-pressure abrasive slurry jet on a ductile 6061-T6 target over a wide range of aspect ratios. Features such as shallow pockets with low aspect ratios to deep slots with aspect ratios ∼1.5 were fabricated to investigate the correlations between the aspect ratio, degree of pass overlap, and number of repeating passes with the machined surface evolution characteristics. A comprehensive model was presented that combined computational fluid dynamics (CFD) with surface evolution to predict the evolving machined feature topography after each of the overlapping and repeating passes, and to provide insights into experimental observations. The model explicitly considered the CFD-predicted local particle impact angles and velocities as well as effects due to secondary impacts, high sidewall slopes, and stagnation effects. For larger degrees of overlap, measurements revealed a more than linear rate of increase in depth after each repeat of two adjacent overlapped passes, as opposed to a linear depth increase for smaller overlaps and blind pockets. Large overlaps were found to result in asymmetric features. Up to a critical aspect ratio of ∼0.65, the model predicted the surface evolution of the features to within <8.6% of those measured. Beyond that, randomness in the machined feature shape and size made the process challenging to control and the surface evolution difficult to predict. Nevertheless, the model was able to elucidate the reasons for the randomness and other observed phenomena such as the more than linear growth in etch rate, and the occurrence of feature asymmetry. The findings emphasize that flow confinement, increases in the jet's turbulent kinetic energy, and the formation of vortices at the bottom of the machined features are critical factors influencing the machining process, and that in these cases explicit modeling approaches like the one presented in this study must be used.

Investigation of mechanical and corrosion behavior of multi-pass nickel-aluminum bronze fabricated through wire-arc directed energy deposition

In this study, a multi-pass nickel-aluminum bronze (NAB) layer was deposited on a steel surface by wire-arc directed energy deposition (DED). The study then comparatively analyzed the microstructural characterization, mechanical properties, and corrosion behaviors of the overlap region between adjacent passes and the substrate (NAB layer). The results revealed that the grain size of the previous deposited layer in the overlap region was smaller than that of the post deposited layer and that the precipitated phase was mainly a lamellar κIII phase. Based on the microstructural differences, the strength of the overlap region was approximately 100 MPa less than that of the substrate. However, following double-layer deposition, the strength of the overlap region increased significantly and was nearly equivalent to that of the substrate, reaching 730 MPa. The corrosion of the multi-pass wire-arc DED of the NAB alloy was divided into two stages. Initially, because of the small grain size and the presence of the eutectic organization κIII and α-Cu phases, the corrosion susceptibility in the overlap region was higher than that of the substrate. After the corrosion product film was formed, the strength and bonding force with the alloy of the corrosion product film on the overlap region were better than those on the substrate, and the corrosive resistance of the overlap region was greater than that of the substrate.

Corrosion behaviour of copper cladded steel produced using multi pass friction stir welding process

Thick cladding of copper on mild steel substrate has been produced using a novel multipass friction stir welding (FSW) process, executing several adjacent passes, covering the entire steel substrate. Metallography examination reveals proper bonding between clad copper and steel substrate, with grain refinement for the steel region near the interface, while the copper portion depicts grains coarsening due to multipass action during FSW. The clad copper plates and base copper were tested for their corrosion behaviour in 3.5% NaCl solution through the potentiodynamic polarisation method. The study suggests corrosion rate of cladded plates were nearly same as pure copper, and much lower than the steel substrate. SEM-EDS and XRD examination depicts oxide layer formation for the corroded clad top. Atomic force microscopy reveals the presence of pits and valleys in the corroded clad copper top. The experimental results suggest multipass cladding through FSW does not degrade the corrosion properties of copper to a greater extent, and are comparable to base copper results.

Tailoring the microstructure and mechanical properties of Cu–Fe alloy by varying the rolling path and rolling temperature

Cu–Fe alloys are expected to be extensively used in electronics, transportation and machinery industries due to the extraordinary mechanical properties and functional properties. To optimize rolling process and the final properties of Cu–Fe plates. The effect of rolling path, rolling temperature and thickness reduction on microstructure evolution, mechanical and electrical properties of Cu–Fe alloy are carefully investigated. The results shown that the thickness reduction has a significant effect on mechanical properties of Cu–Fe alloy. The yield strength of Cu–Fe plates with 20% thickness reduction is more than 2 times higher than that of homogenized ingot. While the yield strength increases gradually as further increasing the thickness reduction. Rolling temperature is an important parameter determining the strength-ductility balance. The strength of plate rolled with 80% thickness reduction at 400 °C is similar to that of the plates in cold-rolled state, and the ductility is higher than that for the plates in the cold-rolled state. Further investigation reveals that the formation of heterogeneous structure characterized with recrystallized-fine grains embedded in deformed-coarse grains is responsible for the observed extraordinary mechanical properties. Rolling path could also affect the microstructure evolution and formability of the plates. For plate rolled with route 1 (unidirectional rolling), a stronger Copper-type texture with two Brass-type textures are observed. For plate rolled with route 2, where the rolled plate is rotated to 90° with respect to previous rolling direction between adjacent rolling passes, only Brass-type texture is generated. A rolling-path dependent edge-crack behavior is observed during rolling. Edge cracks are generated during rolling with route 2, while the edge cracks are not observed for plates rolled with route 1. Factors affecting the edge-cracks behavior are also discussed.

Robotic spray painting path planning for complex surface: boundary fitting approach

AbstractCurrently, most of the robot path planning methods for spray painting are based on slicing the Computer-Aided Design model of the target surface to generate a series of path points. They usually neglect the geometric boundary of the model and the smoothness of the generated path, leading to a non-uniform coating thickness. To ameliorate it, an improved “boundary fitting approach” is proposed. In this method, the upper and lower boundaries of the target surface are firstly detected based on the topology of the stereolithography model. For each pass, several sample points are extracted with a uniform length interval from the intersection points generated by the basic slicing method. The path pass is then described by a fourth-order polynomial curve. It fits the boundary points and sample points for the $z$ - $t$ and $y$ - $t$ relationships, respectively. Based on the spray gun’s motion direction and spray direction, the orientation of each path point is also defined. The parameters of the path pass are optimized by particle swarm optimization to get the optimal uniformity of the resulting coating thickness. Both of the global uniformity and the local uniformity between two adjacent passes are considered. The strength of the proposed approach is validated by comparing the simulation with the basic and other typical algorithms. The results denote that boundary fitting approach could improve the uniformity of coating thickness. It brings about a better performance for the painted workpiece.

Numerical modeling and simulation of machining of 3D printed CFRP composite

Carbon Fiber Reinforced Polymer (CFRP) composites are gaining popularity in recent years for their high specific strength and superior performance under extreme conditions. Additive manufacturing (AM) or 3D printing of CFRP composites has added a new dimension to the existing research of CFRP composites. However, one of the caveats of 3D printed CFRP composites is that the dimensional accuracy and the surface finish achieved fail to meet the standard tolerance requirement. To achieve the desired accuracy further post-process machining is required. However, machining an anisotropic material such as 3D printed CFRP composites impose challenges. This study aims at investigating the machining behavior and post-processing capability of 3D printed CFRP using numerical modeling and simulation using ABAQUS/Explicit, a commercially available powerful finite element analysis (FEA) software package. Influence of machining parameters, such as feed and depth of cut (DOC) and 3D printing parameter, such as percentage of overlap between adjacent passes have been studied. The post-processing capability or machining behavior of 3D printed CFRP has been evaluated by dependent parameters, such as, cutting forces, strain, chip and burr formation, and the resultant surface topology. With the use of proper damage parameters, such as, ductile and shear damage and Johnson-Cook criterion for plasticity, a 3D model was developed in the FEA. Eight layers were stacked with the orientation of 45°-135°-45°-135°. The layers were joined using cohesive properties. Damage in the cohesive bonds was also defined using the quadratic damage criterion to model delamination. To capture the changes in elemental level, linear tetrahedral elements C3D4T, were used. A reference point on the bottom layer was used to capture the history of cutting forces. The cutting and thrust forces increased with the increase of DOC and feed. The rigidity, shape of the flutes and print direction influenced chip formation. Finally, the proposed model was used to observe the quality of surface finish.

On the microstructure and texture evolution in 17-4 PH stainless steel during laser powder bed fusion: Towards textural design

Additive Manufacturing (AM) of metals allows the production of parts with complex designs, offering advanced properties if the evolution of the texture can be controlled. 17-4 precipitation hardening (PH) stainless steel is a high strength, high corrosion resistance alloy used in a range of industries suitable for AM, such as aerospace and marine. Despite 17-4 PH being one of the most common steels for AM, there are still gaps in the understanding of its AM processing–structure relationships. These include the nature of the matrix phase, as well as the development of texture through AM builds under different processing conditions. We have investigated how changing the laser power and scanning strategy affects the microstructure of 17-4 PH during laser powder bed fusion. It is revealed that the matrix phase is δ-ferrite with a limited austenite presence, mainly in regions of the microstructure immediately below melt pools. Austenite fraction is independent of the printing pattern and laser power. However, reducing the time between adjacent laser passes during printing results in an increase in the austenite volume fraction. Another effect of the higher laser power, as well as additional remelting within the printing strategy, is an increase in the average grain size by epitaxial ferrite grain growth across multiple build layers and the development of a mosaic type microstructure. Changes to the scanning strategy have significant impacts on the textures observed along the build direction, while 〈100〉 texture along the scanning direction is observed consistently. Mechanisms for texture formation and the mosaic structure are proposed that presents a pathway to the design of texture via AM process control.

Microstructure and mechanical properties of ultrafine grained 5052 Al alloy fabricated by multi-pass differential speed rolling

This study examined the microstructural evolution and mechanical properties of an ultrafine grained (UFG) Al alloy processed by multi-pass differential speed rolling (DSR). For DSR operations with a thickness reduction of 30% in each pass and a roll speed ratio of 1:4 for the lower and upper rolls, respectively, plastic strain was imparted to the samples that were rotated 180° along the longitudinal axis between the adjacent passes. As the number of operations increased, the deformed microstructure developed gradually from a band-like structure, which was observed after a single pass, to one consisting of nearly equiaxed ultrafine grains (≈0.7 μm) divided by high angle grain boundaries (GB) after four-pass DSR. A close microstructural observation using high resolution transmission electron microscopy showed that the GBs of the UFG Al sample were curved and wavy. Based on microstructural observations, the grain refinement mechanism occurring in the Al sample during multi-pass DSR was found to be governed by geometric dynamic recrystallization and continuous dynamic recrystallization. In addition, the deformation texture of the DSR-treated samples developed into the ideal shear texture consisting of a rotated Cube {001}<110> orientation and γ-fiber (<111>//ND) with increasing number of operations. The tensile test results showed that the strength of the deformed samples increased with decreasing grain size while its tensile ductility was sacrificed. Moreover, the contribution of the strengthening mechanisms, such as solid solution, precipitation, grain size and dislocation strengthening, were discussed.

Precise and efficient surface flattening of polycrystalline diamond by normal-irradiated trochoidal femtosecond laser machining

The widely used polycrystalline diamond generally requires high smoothness and high efficiency in surface flattening. However, conventional machining methods, such as grinding and polishing, are not capable of processing the polycrystalline diamond with the desired high material removal rate owing to its high hardness, wear resistance and thermal stability. Femtosecond laser is considered an effective machining approach with high precision, but the machining efficiency is not satisfactory in terms of large-scale surface flattening. To further improve the processing efficiency with good surface smoothness, a strategy of normal-irradiated trochoidal femtosecond laser machining (NTFM) was developed in this study to process the polycrystalline diamond with Co binder. The theoretical analysis model, including the accumulated laser pulse number and the distribution of laser energy density, was first deduced for NTFM. The key influent factors were found to be the amplitude of galvanometer and the space between two adjacent laser scanning passes. Then, through machining microgrooves, it is proved that the material removal rate of NTFM was almost twice as high as the conventional non-trochoidal femtosecond laser milling (CFM). Besides, short pulse delay in the NTFM strategy can reduce the heat penetration and inhibit the falling-off of diamond grains. Thus, NTFM strategy is more favorable for generating smooth surface when compared to CFM. It is also found that improving the heat accumulation in NTFM is beneficial to decrease the graphitization level on the machined surface. Finally, a mirror-like large-scale surface of the polycrystalline diamond was successfully processed, with an average roughness of Ra 63 nm and PV value of 0.741 μm by NTFM, taking 30 min or only one-sixth of the time required by CFM. The results indicate that the proposed NTFM strategy is more practical to precise and highly efficient surface flattening of diamond compared to CFM.

Pass-by-Pass Ambiguity Resolution in Single GPS Receiver PPP Using Observations for Two Sequential Days: An Exploratory Study

“Pass-by-pass” or “track-to-track” ambiguity resolution removes Global Navigation Satellite System (GNSS) satellite hardware delays between adjacent undifferenced (UD) ambiguities, which is often applied in precise orbit determination (POD) for Low Earth Orbit (LEO) satellites to improve the accuracy of orbits. In this study, we carried out an exploratory study to use the “pass-by-pass” ambiguity resolution by differencing the undifferenced ambiguity candidates for two adjacent passes in sidereal days for a single Global Positioning System (GPS) receiver static Precise Point Positioning (PPP). Using the GPS observations from 132 globally distributed reference stations of International GPS Service (IGS), we find that 99.08% wide-lane (WL) and 97.83% narrow-lane (NL) double-difference ambiguities formed by the “pass-by-pass” method for all stations can be fixed to their nearest integers within absolute fractional residuals of 0.2 cycles. These proportions are higher than the corresponding values of network solution with multiple receivers with 97.39% and 91.20%, respectively. About 97% to 98% of ambiguities can be fixed finally on average. The comparison of the estimated station coordinates with the IGS weekly solutions reveals that the Root Mean Square (RMS) in East and North directions are 2-4 mm and is about 6 mm in the Up direction. For hourly data, it is found that the mean positioning accuracy improvement can achieve to about 10% after ambiguity resolution. From a dam deformation monitoring application, it shows that the fixing rate of WL and NL ambiguity can be closed to 100% and higher than 90%, respectively. The time series generated by PPP are also in agreement with the short baseline solutions.

Measurement of the molecular dipole moment and the hyperfine and Λ -doublet splittings of the BΠ13 state of thallium fluoride

We report high-precision measurements on the thallium fluoride $\tilde{J} = 1$ hyperfine manifold of the $B^3\Pi_1$ ($\nu = 0$) state. This state is of special interest because it is central to an optical cycling scheme that is envisioned to play an important role in enhancing the sensitivity of the CeNTREX nuclear Schiff-moment experiment presently under construction. The measurements are made by monitoring the fluorescence induced by narrow-band laser excitation of a cryogenic molecular beam. We use a multipass arrangement of the laser beam to enhance fluorescence. When viewed with a camera, we can spatially resolve images from adjacent passes that approach the molecules from opposing directions. These images yield a sensitive visual method to identify the central frequency of a transition. Coupling these line-center determinations with frequency calibration from an acousto-optic modulator has allowed a more precise determination of the $\tilde{J} = 1$ manifold of hyperfine level splittings. We observe Stark shifts of the $\tilde{J} = 1$ levels and infer a permanent electric dipole moment of 2.28(7) D and $\Lambda$-doublet splittings for the $F_1' = 1/2$ and $F_1' = 3/2$ manifolds of 14.4(9) MHz and 17.4(11) MHz, respectively.

Analysis of the uniformity of the distribution of herbicides in the intercustal zone with a bar with a deviating section

It is known that a large share of the costs in perennial plantings of fruit and berry crops is associated with weed control. In the ranks of plants, chemical methods of weed control using herbicidal rods are used. In recent years, requirements for uniform distribution of herbicides on the treated surface have increased. The article analyzes the accuracy of the dosage of herbicides in the intercustal zone with a bar with a deviating section. The movement of the rod in the horizontal plane and the spill of liquid along its length is considered. The volume of the poured liquid, the area of the wetted surface, the amount of liquid per unit area are determined. It was established that the dose of application of herbicides over the area depends on the speed of the bar, the angle of its inclination to the direction of movement and the specific spill of the liquid along the length. It is shown that the more the rod deviates from its initial position and the closer it is to the row line, the greater the spout of the solution per unit area with respect to a given one. Dependencies are obtained that allow one to compare the doses of the application of the working solution of the herbicide on the treated surface before the bar meets the cultivated plant and when it is bypassed. The paper shows the data of calculation of the spill of the working fluid at a specific point of the rod. It was revealed that during the processing of the inter-brush strip in one pass with the half-line deviating section of the row line overlapping, the excess of the given outflow dose can reach 20 times. To process the inter-bush zones of perennial plantations, it is recommended to stack the herbicidal booms with short deflecting sections up to the row axis, providing compensation for inaccuracies in driving and planting trees in a row, and processing the row in two adjacent passes.

Effects of Process Parameters on the Thickness Uniformity in Two-Point Incremental Forming (TPIF) with a Positive Die for an Irregular Stepped Part.

Incremental sheet forming (ISF) is a novel flexible forming technology with advantages, such as a low forming force, low-energy-consuming equipment, and good forming performance. The lack of available information about the formability of the two-point incremental forming (TPIF) process makes it limited for practical applications. Taking an irregular stepped part as the target part, the effects of process parameters on the thickness uniformity when using TPIF with a positive die for AA1060 aluminum alloy sheets were investigated. First, the set of optimal parameters regarding the diameter of the tool head, feed rate, and the step size were obtained through orthogonal experiments. Furthermore, the optimal parameter set of the number of forming passes, the direction of movement of the forming tool, and the forming angle was determined and the optimal forming result was numerically and experimentally verified. This demonstrated that the parameters affecting the thickness uniformity of the irregular stepped parts were, in descending order, the diameter of the forming tool, the feed rate, and the step size, with corresponding optimal values of 12 mm, 15,000 mm/min, and 0.4 mm, respectively. With an increase of the number of passes and a decrease of the forming angle between adjacent passes, and adopting an alternating clockwise and counterclockwise toolpath, the thickness uniformity of the formed parts was effectively improved.

Fabrication of super-hydrophobic and highly oleophobic Ti-6Al-4 V surfaces by a hybrid method

In this study, the super-hydrophobic and highly oleophobic surfaces were fabricated on Ti-6Al-4V substrate by a hybrid method, which combined laser texturing followed by silanization treatment. To fabricate super-hydrophobic and oleophobic surfaces more accurately and effectively, three series of experiments have been carried out to determine the laser parameters for the fabrication of surfaces with the best wettability. Surface wettability was assessed by water contact angle, glycerin contact angle and the n-hexadecane contact angle. To investigate the laser texturing microstructure features and effects thereof on wettability, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and white light confocal scanning microscopy measurements were utilized to characterize the modifications of morphologic, chemical compositions and 3D profiles. The surface with best wettability presented a water contact angle of 153.3°, glycerin contact angle of 149.7°, and n-hexadecane contact angle of 136.6° was successfully achieved by setting the laser parameters to: distance between adjacent laser passes at 60 μm, output power at 12 W and scanning speed at 300 mm/s. The effect of corrosion and abrasion on wettability was also evaluated. Stability tests prove that the super-hydrophobic and oleophobic surfaces possess corrosion/abrasion resistance and good chemical and mechanical stability.

Automatic Detection of Internal Waves on Satellite Images and Estimates of the Mixed Layer Density

This work presents an automatic algorithm for detecting internal waves (IWs) using the visible channel images of the MODIS radiometer. The algorithm is based on the local Hough transform. The sources of detection errors and the possibility of excluding false detections are considered. If a train of IWs is detected, it is possible to estimate the wavenumber. The wavelength in the images used in our experiments is within the range 1300–2200 m. The speed of IWs is estimated using two adjacent passes of the Aqua and Terra satellites. The speed and wavenumber are used for estimating the density characteristics of the mixed layer in a two-layer model with constant density. The estimated density difference between the layers based on satellite data is in a good agreement with the in situ data.

A double raster laser scanning strategy for rapid die-less bending of 3D shape

Double raster scanning approach to 3D laser forming was investigated to obtain a large deformation with one-step laser irradiation, avoiding repetitive scanning. The magnitude of the deformation during raster scanning was found to be strongly dependent on the overlapping between adjacent passes, which can be controlled by changing their spacing and the beam diameter. Therefore, 3D deformation during raster scanning has been analyzed at various overlap ratios, whose effect on the temperature and strain distribution were discussed. As the heat transfer mode significantly influences the uniformity of the bending process, the variations in bending angles with negative and positive overlapping ratios have also been investigated. The ratio of the longitudinal and lateral curvatures decreased with the increasing overlap ratio. Therefore, the effect of the lateral side is more important for specifying the final symmetry of the part, playing a critical role in bending with higher overlap ratios. In a rectangular part, deformation of the lateral side was found to be more difficult, showing strong dependence on the length of the scanning track, compared with the space of the adjacent passes. Through process characterization, the double raster scanning process has been well understood and proved to be a feasible approach to 3D laser forming of rectangular parts.

Development of a variable rate applicator for uniform fertilizer spreading

Environmental impact and economic concerns have driven a variable rate technology (VRT). Spinner spreaders were mainly used for granular fertilizer application since they are simple in design, inexpensive, and can cover large areas. However, the spreader was not adequate for VRT because uniformity changes drastically while varying application rates. Thus, the purpose of this study was to develop a variable rate applicator with uniform spreading patterns. A commercial spreader was modified with a controller and electric actuators for controlling fertilizer discharge directions and amounts. Database was established to determine the optimum discharge direction according to the fertilizer application amount. The uniformity of spreading patterns in accordance with the spread amount per set unit area was evaluated by the statistical coefficient of variation (CV) lower than 15% is assumed to prevent damage to the crop. Test results showed that CVs were 8%, 9%, and 8%, respectively, for a tractor in race track mode (adjacent passes in same direction of travel) at 200 kg/hm2, 300 kg/hm2, and 400 kg/hm2. This indicates that the fertilizer was spread uniformly, while the coefficient of variation was 12% at 200 kg/hm2 in back and forth mode (adjacent passes in the opposite direction of travel). Overall, the results suggest that the race track mode is suitable for operation of a tractor to ensure uniform spreading of fertilizer when applying at variable rates. The future goal is to establish a system for automatic variable rate application according to location in connection with soil analysis and geographic information systems. Keywords: variable rate technology, fertilizer application, uniform spreading, spinner, granular applicator, fertilizer amount control DOI: 10.25165/j.ijabe.20191202.3242 Citation: Han C-W, Lee S-Y, Hong Y-K, Kweon G-Y. Development of a variable rate applicator for uniform fertilizer spreading. Int J Agric & Biol Eng, 2019; 12(2): 82–89.

Effect of deformation routes on the microstructures and mechanical properties of the asymmetrical rolled 7050 Aluminum alloy plates

Asymmetric rolling (ASR) with three different deformation routes and conventional symmetric rolling (CR) were carried out in 7050 Al alloy plates, so as to study the influence of deformation route on the strain distribution, microstructural evolution and mechanical properties. The results show that the ASR process introduces much more effective strain throughout the thickness, resulting in severe deformation or microstructural evolution and improving the alloy's ductility compared to CR deformed samples, irrespective of the deformation routes. Among the three ASR deformation routes, the ASR-R process can introduce highest strains to improve the through-thickness deformation homogeneity, subsequently amount of finer subgrains can be observed in the wider shear band zones due to the intersection of shearing patterns of adjacent rolling passes. Although the strengths of the ASR-processed plates are almost similar, their tensile elongations are obviously affected by the deformation routes, especially the ASR–R route contributes to ~ 23% elongation, which would be mainly responsible by the grain refinement, homogeneous distribution of microstructure and fragmentation of coarse constituent particles.

A Weld Position Recognition Method Based on Directional and Structured Light Information Fusion in Multi-Layer/Multi-Pass Welding.

Multi-layer/multi-pass welding (MLMPW) technology is widely used in the energy industry to join thick components. During automatic welding using robots or other actuators, it is very important to recognize the actual weld pass position using visual methods, which can then be used not only to perform reasonable path planning for actuators, but also to correct any deviations between the welding torch and the weld pass position in real time. However, due to the small geometrical differences between adjacent weld passes, existing weld position recognition technologies such as structured light methods are not suitable for weld position detection in MLMPW. This paper proposes a novel method for weld position detection, which fuses various kinds of information in MLMPW. First, a synchronous acquisition method is developed to obtain various kinds of visual information when directional light and structured light sources are on, respectively. Then, interferences are eliminated by fusing adjacent images. Finally, the information from directional and structured light images is fused to obtain the 3D positions of the weld passes. Experiment results show that each process can be done in 30 ms and the deviation is less than 0.6 mm. The proposed method can be used for automatic path planning and seam tracking in the robotic MLMPW process as well as electron beam freeform fabrication process.