Penetration Shape Research Articles

Solidification cracking susceptibility of alloy 718 during additive manufacturing and evaluating method

Although hot cracks frequently occur during metal additive manufacturing (AM), there are very few fundamental studies on the cracking behaviour and susceptibility. In this study, a horizontal tensile-type hot cracking test was investigated for evaluating the solidification cracking susceptibility of alloy 718 quantitatively during AM, particularly in laser powder bed fusion. The factors influencing the cracking susceptibility were also examined. The solidification cracking was reproduced by the melting of the AMed specimen with a tensile load under conditions of heat source simulating the AM process. The critical initial tensile stress for solidification crack initiation could apply as an evaluation index for cracking susceptibility. The critical initial stress decreased with increasing the laser power. A similar tendency was observed during the melting of the powders set on tiny groove for simulating AM process. The critical strain rate for solidification cracking (CST) was derived by a thermal elastic–plastic analysis using the critical initial stress measured experimentally. The CST at the laser power of 1125 W was higher than that of 1000 W for no crack condition. Therefore, high CST corresponding to penetration shape with high laser power induce to deteriorate the solidification cracking susceptibility.

Cement slurry penetration behavior of swirl grouting technology

Traditional pressure grouting technology operates under steady pressure conditions, causing the grout to easily flow along preferential pathways. This results in uneven grout penetration and increased economic costs. This study proposes swirl grouting technology, which effectively improves this problem. To verify the effectiveness of swirl grouting, a fan-shaped blade tool was also proposed. The grout penetration performance was investigated through experimental studies. The length, width, height, weight, and uniformity of the grouted bodies produced by the swirl grouting method were compared with those produced by the steady pressure grouting method. Then, the mechanisms of swirl grouting were analyzed through transparent disc visualization experiments. The results demonstrated that, at different water–cement ratios, the swirl device increased the penetration length in the X, Y, and Z directions by 43.3%, 27.8%, and 45.8%, respectively, compared to the conventional straight device, and by 57.3%, 39.4%, and 55.6%, respectively, compared to the fan blade device. Moreover, the swirl device increased the weight of the grouted stone body by 54.9% compared to the conventional straight device and by 91.0% compared to the fan blade device, significantly enhancing filling efficiency. The uniformity coefficient of the swirl device permeation decreased by 56.6% and 51.0%, respectively, compared to the conventional straight device and the fan blade device, resulting in a more uniform grout distribution. The transparent disc visualization experiment further revealed the advantage of the swirl device in promoting the migration of fine particles, with a significant increase in average penetration distance and a penetration shape closer to a regular circle. The rotating flow path of the swirl device imparts additional rotational momentum and multidirectional penetration capabilities. The resulting turbulence accelerates the mixing of grout with the soil matrix, facilitating the migration of fine particles, expanding flow channels, and reducing flow resistance. This combination of effects enhances penetration efficiency and reduces energy loss. This study offers significant practical application value for improving engineering quality, construction efficiency, and reducing costs.

Effect of penetrant-polymer interactions and shape on the motion of molecular penetrants in dense polymer networks.

The diffusion of dilute molecular penetrants within polymers plays a crucial role in the advancement of material engineering for applications such as coatings and membrane separations. The potential of highly cross-linked polymer networks in these applications stems from their capacity to adjust the size and shape selectivity through subtle changes in network structures. In this paper, we use molecular dynamics simulation to understand the role of penetrant shape (aspect ratios) and its interaction with polymer networks on its diffusivity. We characterize both local penetrant hopping and the long-time diffusive motion for penetrants and consider different aspect ratios and penetrant-network interaction strengths at a variety of cross-link densities and temperatures. The shape affects the coupling of penetrant motion to the cross-link density- and temperature-dependent structural relaxation of networks and also affects the way a penetrant experiences the confinement from the network meshes. The attractive interaction between the penetrant and network primarily affects the former since only the system of dilute limit is of present interest. These results offer fundamental insights into the intricate interplay between penetrant characteristics and polymer network properties and also suggest future directions for manipulating polymer design to enhance the separation efficiency.

Experimental and Numerical Study on the Perforation Behavior of an Aluminum 6061-T6 Cylindrical Shell.

The modified Johnson-Cook (MJC) material model is widely used in simulation under high-velocity impact. There was a need to estimate a strain rate parameter for the application to the impact analysis, where the method typically used is the Split Hopkinson bar. However, this method had a limit to the experiment of strain rate. This study proposed to estimate the strain rate parameter of the MJC model based on the impact energy and obtained a parameter. The proposed method of strain rate parameter calculation uses strain parameters to estimate from the drop weight impact and high-velocity impact experiments. Then, the ballistic experiment and analysis were carried out with the target of the plate and cylindrical shape. These analysis results were then compared with those obtained from the experiment. The penetration velocities of plates could be predicted with an error of a maximum of approximately 3.7%. The penetration shape of the cylindrical target has a similar result shape according to impact velocity and had an error of approximately 6%.

Characterisation of weld bead and microhardness of SS316L weld overlays on S355J2+N steel using GTAW under E-type magnet

In this study, a three-pole (E-type) electromagnet with magnetic configurations north-south-north (NSN) and south-north-south (SNS) was installed in the GTAW process to generate a combination of two symmetrically transverse external magnetic fields around the weld arc and the molten pool. The effects of magnetic fields obtained by these two types of magnetic configurations (NSN and SNS) on the weld bead characteristics and microhardness in GTAW were analysed. In these experiments, high-strength low alloy (HSLA) S355J2+N grade with a thickness of 10 mm was selected as the substrate material and S316L as the filler wire. Using magnetic fields during the welding process successfully enhanced the weld bead appearance and shape and improved the mechanical characteristics of weld overlays. It was also observed that for different values of excitation current, magnetic fields generated with both configurations ( i.e., NSN and SNS) provide greater bead width, a higher penetration shape factor, and higher microhardness values in comparison to specimens welded with conventional GTAW. The NSN and SNS configurations of the E-type magnet improve the penetration shape factor by 58% and 46%, respectively. These configurations were more suitable for weld overlays (cladding) and hardfacing. However, the observations indicated an enhancement in microhardness for all excitation current values by employing the NSN and SNS magnetic configurations.

A Numerical Study on the Cement Slurry Penetration Performance of the Cyclic Grouting Method with High-Frequency Pulsating Pressure

The performance of traditional steady grouting is sometimes limited; therefore, a new high-frequency pulsed grouting method is proposed. Through the CFD method, this paper studies the cement slurry penetration performance of cyclic grouting under the influence of pulsating pressure and steady pressure. Firstly, the penetration shape and flow fields of the two grouting methods are investigated. Secondly, the effects of pulsation parameters on penetration performance are studied. Finally, the influence of various working conditions, such as soil properties, grout parameters, grouting pipe length, and back pressure, on penetration distance is also investigated. The results show that pulsating grouting achieves better penetration performance compared with steady pressure grouting. With the increase in frequency, pulsating grouting exhibits superior performance, while with the increase in pulsation amplitude, the penetration distance initially increases and then decreases. This is because part of the pulsating pressure is lower than the back pressure, which weakens the pulsating effect. As viscosity and back pressure increase and as porosity and particle size decrease, the proportion of lateral diffusion in pulsating grouting relative to steady pressure grouting increases. This indicates that lateral penetration performance achieves optimal results under high-flow-resistance conditions. However, when the flow resistance becomes excessively high, the vertical penetration distance may be affected. This study is expected to improve the grouting efficiency and provide a better understanding of pulsating grouting design and operation.

Analysis of Zn diffusion in various crystallographic directions of GaN grown by HVPE

This work presents the diffusion mechanism of zinc in gallium nitride. Halide vapor phase epitaxy layers were deposited on native ammonothermal seeds of three crystallographic orientations: c - (0001), m - (10-10), and a - (11–20). The surfaces were prepared to an epi-ready state by mechanical and chemical-mechanical polishing. Zinc ions were then implanted with energy of 230 keV and fluence 1016 cm−2 to create an infinite-like source of zinc atoms near the surface. The implanted samples were annealed by ultra-high-pressure method in the temperature range 1250–1450 °C at nitrogen pressure of 1 GPa for 4.5 h to remove the post-implantation structural damage and trigger the diffusion of zinc into the depth of the gallium nitride layers. X-ray diffraction measurements were performed for samples at every stage of the process: as-grown, as-implanted and annealed in order to investigate the evolution of the structural quality. Secondary ion mass spectrometry was employed to analyze depth profiles of zinc and concentrations of impurities. Positron annihilation spectroscopy and low-temperature photoluminescence were employed to assess the defect evolution in the samples. The results showed a strong dependence of zinc diffusion on the crystallographic direction of gallium nitride crystal growth. The depth profiles measured for the analyzed crystallographic directions differed in shape and range of zinc penetration. Diffusion coefficients were calculated for all the analyzed temperatures. The pre-exponential diffusion factor and activation energy were determined.

Penetrant shape effects on activated dynamics and selectivity in polymer melts and networks based on self-consistent cooperative hopping theory.

We generalize and apply the microscopic self-consistent cooperative hopping theory for activated penetrant dynamics in polymer melts and crosslinked networks to address the role of highly variable non-spherical molecular shape. The focus is on vastly different shaped penetrants that have identical space filling volume in order to isolate how non-spherical shape explicitly modifies dynamics over a wide range of temperature down to the kinetic glass transition temperature. The theory relates intramolecular and intermolecular structure and kinetic constraints, and reveals how different solvation packing of polymer monomers around variable shaped penetrants impact penetrant hopping. A highly shape-dependent penetrant activated relaxation, including alpha time decoupling and trajectory level cooperativity of the hopping process, is predicted in the deeply supercooled regime for relatively larger penetrants which is sensitive to whether the polymer matrix is a melt or heavily crosslinked network. In contrast, for smaller size penetrants or at high/medium temperatures the effect of isochoric penetrant shape is relatively weak. We propose an aspect ratio variable that organizes how penetrant shape influences the activated relaxation times, leading to a (near) collapse or master curve. The relative absolute values of the penetrant relaxation time (inverse hopping rate) in polymer melts versus in crosslinked networks are found to be opposite when compared at a common absolute temperature versus when they are compared at a fixed value of distance from the glass transition based on the variable Tg/T with Tg the glass transition temperature. Quantitative comparison with recent diffusion experiments on chemically complex molecular penetrants of variable shape but fixed volume in crosslinked networks reveals good agreement, and testable new predictions are made. Extension of the theoretical approach to more complex systems of high experimental interest are discussed, including applications to realize selective transport in membrane separation applications.

Penetration shape control with correction of the state variables evaluation during electron-beam welding by the level of active disturbances

Penetration shape during electron-beam welding is determined in the first approximation by the vapour plasma crater shape formed by the energy source. The inability to measure the parameters of penetration shape during electron-beam welding leads to their estimation by regression equations that establish a relationship with mode parameters. However, when welding mode parameters are stabilized, the instability of penetration shape remains due to the action of uncontrolled disturbances, which in some cases lead to unacceptable deviations. A possibility of the state variables evaluation correction during electron-beam welding, namely the depth penetration and the weld shape factor, by determining the “noise component”, is considered. Such correction is carried out by the discrepancy of any measured output variable, as the difference between its estimate according to a similar mathematical model and the measured value. As such output variable, the vapour plasma torch light intensity can be used. A control algorithm and a structural diagram of the automatic control system for weld penetration shape with correction of model assessment of the process state by the measured output have been developed.

Non-destructive testing of physical and mechanical properties of local zones in welded joints

The influence of the “saw-tooth” type electron beam sweep on the penetration shape during electron-beam welding of 30KhGSA high-strength steel with different welding modes was investigated. Using the instrumented indentation method, the distribution of Young’s modulus, as well as the characteristics of strength and plasticity in the welded joints cross-sections, was obtained. It has been found that in the weld metal there is a sharp increase in strength characteristics, while the plasticity ones are significantly reduced. The values of the Young’s modulus also varied over the cross-sections. The considerable decrease in this characteristic (up to 20%) was registered in the weld metal in comparison with the parent metal results.

Statistical Modelling and Optimization of TIG Welding Process Parameters Using Taguchi’s Method

This current research focuses on optimizing the welding process parameters and penetration of 5052 alloys using a TIG welding process based on the Taguchi methods. Process parameters such as current, voltage, and speed with three different levels were taken to form the L27 orthogonal array using the design of experiments. Analysis of variance, signal-to-noise ratio analysis, and regression analysis were performed. The regression analysis indicated that the developed model has greater adequacy in predicting the reinforcement form factor (RFF), penetration shape factor (PSF) and hardness of the weld specimens. In addition, the optimized parametric condition for the welded specimen was found to be current, voltage, and speed of 140 A, 18 V, and 300 mm/min, respectively.

Experimental investigation and optimization of weld bead shape factor and form factor using recycled steel slag as a flux in submerged arc welding process

The quality and productivity of welds produced depend upon the weld bead profile which is represented by weld penetration shape factor (WPSF) and weld reinforcement form factor (WRFF). The weld profile is further dependent upon welding parameters used hence optimization of welding parameters is essential. In this research work, the steel slag has been recycled to act as a flux in submerged arc welding. The effect of process parameters on WPSF and WRFF using recycled slag has been evaluated. The mathematical models have been developed from the data created. It was found that the weld deposited with recycled steel slag performs well as the WPSF and WRFF are comparable with that deposited with fresh flux. The welding parameters have been optimized using the desirability approach and genetic algorithm. The genetic algorithm yielded more accurate results as compared to the desirability approach.

Experimental Study on Bead on Plate (BOP) Welding of 6 mm Thick 9% Nickel Steel by Fiber Laser Welding

Nine percent nickel steel has excellent properties in a cryogenic environment, so it has recently been used as a tank material for most LNG fuel-powered ships. However, 9% nickel steel causes arc deflection due to its tendency of magnetization during manual FCAW welding and the currently used filler metal is 10–25 times more expensive as a base metal compared to other materials, depending on manufacturers. Furthermore, the properties of its filler metal cause limitation in the welding position. To overcome these disadvantages, in this study, the tendency of penetration shape was analyzed through a fiber laser Bead on Plate (BOP) welding for 9% nickel steel with a thickness of 6 mm and a range of welding conditions for 1-pass laser butt welding of 6 mm thick 9% nickel steel with I-Groove were derived. Through this study, basic data capable of deriving optimal conditions for laser butt welding of 9% nickel steel with a thickness of 6 mm were obtained.

Experimental investigation on cladding with metal cored wire using GMAW process and parametric optimization

Cladding is widely used in manufacturing industries for the production of pressure vessel by depositing thick layer of filler material for providing corrosion resistant-surface. The use of metal cored wire in gas metal arc welding (GMAW) process is popular due to its higher deposition rate and productivity. This work investigates the effect of process parameters on the deposition of cladding layer with ER 309L metal core wire (as filler material) on a corrosion resistant material (IS 2062). The welding parameters viz., wire feed rate (WFR), voltage (V), welding speed (S) and nozzle to plate distance (NTD) are employed as process parameters while penetration (P), bead width (W), reinforcement (R), weld penetration shape factor (WPSF) and weld reinforcement form factor (WRFF) as welding responses. The predictive model developed for P, W, R, WPSF, and WRFF using the response surface methodology (RSM) approach is found adequate at 95% confidence interval. The validation results for the developed model results in a model accuracy (MA) of 92.82%, 96.34%, 91.47% 88.98% and 87.75% for model P, W, R, WPSF, and WRFF respectively and it shows higher predictability and accuracy. The process parameters are optimized simultaneously with integrated optimization approach using RSM with Jaya algorithm and obtain optimal solution in less than 20 number of iterations. The minimum fitness value obtained as 1.3008 at an optimal parameter setting of WFR = 12 m min−1, V = 26 V, S = 280 mm min−1, NTD = 10 mm. The validation result at the optimal parameter setting results in an improvement of 6.45%, 11.29%, 13.58%, 16.07%, 15.38% is noted for P, W, R, WPSF, and WRFF respectively.

EFFECT OF MIG WELDING PROCESS PARAMETERS ON EROSION AND CORROSION BEHAVIOR OF ASTM A106 GRADE-B PIPE WELDMENTS

Evaluating the integrity of the welded pipes used for fluid transportation in processing industries demands certain investigations on the erosion and corrosion behavior under various environmental conditions. ASTM A106 Grade-B pipes are butt welded using an automated MIG welding setup to obtain the optimum output response such as Reinforcement Form Factor (W1), Penetration Shape Factor (W2), and Tensile Strength (W3) in the weldments. The slurry erosion test is conducted on the weldment surface by varying the velocity and erodent concentration in acidic (0.1M H2SO[Formula: see text] and alkaline (3.5%[Formula: see text]wt. NaCl) conditions. Correspondingly, the samples are subjected to electrochemical corrosion test in 0.1[Formula: see text]M H2SO4 and 3.5% wt. NaCl solutions. The SEM investigations carried out on the eroded weldment surface show glimpses of erosion mechanisms such as shallow and deep ploughing, oxide cracks, ridges and valleys, scale formation at some areas attributing to sulphide deposition. The corrosion that occurred on the weldment surface tested under acidic conditions is relatively high compared to the alkaline conditions. The reinforcement form factor is the most preferable weld bead characteristic to obtain better erosion and corrosion resistant weldments in the investigated pipe material.

Quasi-static puncture resistance behaviors of architectural coated fabric

This study investigates the puncture resistance behaviors of architectural coated fabric. The effects of boundary condition, penetrator shape, yarns angle, puncture rate, weight percentage of fiber and coating on puncture resistance behaviors of coated fabric are studied. A fast and effective method is introduced to model the nonlinear anisotropic mechanical behavior of coated fabric. Findings indicate that puncture resistance performance of coated fabric is the critical dependent of the magnitude of penetrator shapes. The essence of penetrator shapes influence is the number of yarns contacted with the bottom of penetrator. The yarn angle in the interest region affects the puncture resistance performance of the coated fabric, which is mainly related to the effective length of the yarn. Besides, the coating weakens the resistance performance when the shape of the penetrator is conical. The puncture resistance strength increases with the increase of weight percentage of fiber. The FE models provided a reasonable prediction of the puncture resistance behavior of the coated fabric.

A Study on Lap Joint Welding of Thin Plate ASTM F1684 Using Fiber Laser Welding

The International Maritime Organization (IMO) has developed stricter regulations on emission standards for sulfur oxides, etc., and the demand for Liquefied Natural Gas (LNG) is increasing as an alternative to satisfy these standards. This study relates to fiber laser welding, an approach which offers high-speed welding and low welding deformation for ASTM F1684, which has a low coefficient of thermal expansion (CTE) even in a cryogenic environment. In this study, through three preliminary experiments using 0.25 mm thick Invar, the conditions required to secure sufficient penetration depth and back bead were identified. Through the cross-sectional observation analysis, the welding conditions without defects were identified and the trend of penetration shape according to increasing welding speed was identified. Following a lap joint laser welding experiment under the secured conditions, the mechanical properties were evaluated through the shear strength test and the heat influence range of a fiber laser was identified through the temperature measurement of a welding part. As a result, it was confirmed that the shear strength of the lap joint laser welding part was 86.8% that of the base metal.

A Study on Fiber Laser Welding of High-Manganese Steel for Cryogenic Tanks

As the environmental regulations on ship emissions by the International Maritime Organization (IMO) become stricter, the demand for a ship powered by liquefied natural gas (LNG) is rapidly increasing worldwide. Compared to other materials, high-manganese steel has the advantages of superior impact toughness at cryogenic temperatures, a low thermal expansion coefficient, and a low-cost base material and welding rod. However, there is a limitation that the mechanical properties of a filler material are worse than those of a base material that has excellent mechanical properties. To solve these shortcomings, a basic study was performed to apply fiber laser welding with little welding deformation and no filler material to high-manganese steel. The relationship between laser welding parameters and penetration shapes was confirmed through cross-section observation and analysis by performing a bead on plate (BOP) test by changing laser power and welding speed, which are the main parameters of laser welding. In addition, the welding performance was evaluated through mechanical property tests (yield strength, tensile strength, hardness, cryogenic impact strength) of a welding part after performing the high-manganese steel laser butt welding experiment. As a result, it was confirmed that the yield strength of a high-manganese steel laser welding part was 97.5% of that of a base metal, and its tensile strength was 93.5% of that of a base metal.

Dependence of Weld Penetration Shape on Energy Efficiency in Electron Beam Welding Process

Investigation of relation between parameters of weld penetration shape and energy efficiency of electron beam welding process was performed in the paper. Analysis of welds cross sections of 316 L(N) steel weld joints obtained by the electron beam welding in the wide range of welding regimes is carried out. It is shown that the dependences of the thermal efficiency on the penetration area at different welding speeds are linear. According to the results, the thermal efficiency coefficient may exceed the ultimate theoretical value for linear heat source. Beam sweep does not affect essentially on the rate of thermal efficiency coefficient, since sweep application leads to an insignificant change in the area of the boundary of the weld pool with the base metal, and therefore, the amount of energy removed through this boundary also changes insignificantly and the penetration area remains almost constant.

Visualizing the vibration effect on the tandem-pulsed gas metal arc welding in the presence of surface tension active elements

In this study, a three-dimensional model of the tandem-pulsed gas metal arc welding process is simulated to investigate the heat transfer and material flow in the presence of vibration and the surface tension active elements. The simulation results are in agreement with optical microscopy images of weld cross-section obtained with different conditions, including with and without vibration-assisted welding. The material flow is visualized using 2D and 3D streamlines on the temperature contour maps. It is found that during the operation of pulsed welding, the heat follows a very stable pattern, although the fluid streams continuously change in the rear region of the weld pool, which is responsible for the final geometry of penetration. Consideration of the effect of surface tension active elements on the Marangoni force improves the simulation results noticeably. A novel approach addresses the effect of sulfur content that comes from both workpiece and filler material. Applying the vibration leads to lower heat input by affecting the free surface behavior and plays an important role in the penetration shape change.