Medium Thickness Plates Research Articles

Differential Analysis and Prediction of Planar Shape at the Head and Tail Ends of Medium-Thickness Plate Rolling

This paper aims to improve planar shape prediction accuracy in the rolling process of medium and thick plates. We present a model based on the strip method that addresses limitations in predicting planar shape variations at the head and tail ends of rolled pieces. By analysing the rolling process, we introduce the concept of an imaginary strip longitudinal length difference to represent planar shape characteristics effectively. By analysing the change in metal shape in the rolling deformation zone, the calculation formula for metal volume in the deformation zone is derived. This establishes a relationship between the longitudinal length difference at the rolled piece ends and the metal volume in the deformation zone. The prediction of plane shape difference between the end and the head of medium and medium-thickness plate is realized. The experimental results confirm the feasibility and effectiveness of the proposed method.

Penetration enhanced behaviour of reactive fragment impacting medium-thickness plate

The medium-thickness plate penetration enhanced behavior of coupled kinetic energy and chemical energy of reactive fragment was investigated. A series of penetration experiments were conducted. After the experiments, the High-speed photography images and blackening at front plate were compared. The results show that the enhancement behavior of reactive fragment penetrating is related to the intensity of deflagration at front plate. Division of deflagration zones of reactive fragment impacting at front plate is proposed, combine dynamic model of reactive fragment penetrating medium-thickness plate, reveal the enhancement mechanism of reactive fragment penetrating medium-thickness plate below ballistic limit velocity.

Effects of Oscillation Width on Arc Characteristics and Droplet Transfer in Vertical Oscillation Arc Narrow-Gap P-GMAW of X80 Steel

In fields, such as oil and gas pipelines and nuclear power, narrow-gap welding has often been used for the connection of thick and medium-thick plates. During the welding process, a lack of fusion was prone to occur due to groove size limitations, seriously affecting the service safety of large structures. The vertical oscillation arc pulsed gas metal arc welding (P-GMAW) method was adopted for narrow-gap welding in this study. The influence of the oscillation width on arc morphology, droplet transfer behavior and weld formation during narrow-gap welding was studied. Oscillation widths from 0 to 4 mm were used to weld narrow-gap grooves with a bottom width of 6 mm. The results show that, in non-oscillation arc welding, the arc always presented a bell cover shape, and the droplet transfer was in the form of one droplet per pulse, while the sidewall penetration of the weld was relatively small, making it prone to a lack of fusion. With an increase in the oscillation width, the arc gradually shifted to the sidewall. The droplet transfer mode was a mixed transfer of large and small droplets, and the sidewall penetration continued to increase, which was conducive to the fusion of the sidewall. However, when the oscillation width was wider than 3 mm, it led to the phenomenon of the arc climbing to the sidewall, and the weld was prone to porosity, undercutting and other welding defects. The oscillation width has a major impact on the stability of the welding process in vertical oscillation arc narrow-gap welding.

A novel seam extraction and path planning method for robotic welding of medium-thickness plate structural parts based on 3D vision

Currently, the robotic welding of medium-thickness plate structural parts has become a common welding application. With the rapid development of automation technology and robotics, the traditional teaching-playback mode and the off-line programming mode cannot meet the automation demand of welding robots. To realize automatic seam extraction and path planning for robotic welding of medium-thickness plate structural parts without programming and teaching, we use three models of medium-thickness plate structural parts as the research objects to propose a novel seam extraction and path planning method for robotic welding of medium-thickness plate structural parts based on 3D vision. Firstly, a set of improved RANSAC multiplanes fitting algorithms is proposed to accurately obtain the position of the intersection lines between the intersecting planes of the point cloud model. On this basis, we combine the geometric features of three models to propose the specific welding seam extraction methods respectively. Then, according to the spatial structure of the welding seams and the welding process, we carry out the welding path planning. Finally, a welding pose planning method based on the dihedral structure is proposed. Experiment results show that the proposed method can well realize the welding seam extraction, welding path and posture planning of medium-thickness plate structural parts without programming and teaching. • We propose specific welding seam extraction methods for different models. • We propose a welding path planning method according to the spatial structure of the welding seams and the welding process. • A welding posture planning method based on the dihedral structure is proposed to realize the automatic planning of welding torch posture. • We use real experimental data to evaluate the performance of the proposed method and compare it with the existing method to illustrate its effectiveness.

Failure analysis of composite plate under ballistic impact

Numerical models were used to evaluate the ballistic impact of common armour steel plates of medium thickness by give-nosed bullets travelling at explosive velocity. To understand the behaviour and breakdown of the material under impact situations, Johnson-Cook material and failure models have been employed. The model constants were derived using data from the authors' prior experimental work done. ANSYS 2019 R3 was used to simulate the situation. The penetration phases have been anticipated. The simulation findings were used to establish residual velocities, ballistic limit velocity, and perforation timings, which matched experimental data.

Investigation of microstructure evolution, mechanical and corrosion properties of SAF 2507 super duplex stainless steel joints by keyhole plasma arc welding

Keyhole plasma arc welding (PAW) of the super duplex stainless steel (SDSS) is expected to achieve full-penetration joints of medium-thickness plates in a single pass with higher efficiency. However, the unique key-holing processes due to the special constricted arc behaviors cause much different thermal cycles of the liquid metals as well as changed microstructures. SDSS 2507 with a thickness of 10 mm was joined by PAW to investigate the joints' microstructure and properties. Microstructure characterization reveals substantial differences in the content of austenite, ranging from 68.9% in weld metal (WM) to 32.1% in the heat-affected zone (HAZ). The oxide inclusions in the WM enhance the hardness of the welded joints, but provide the path for crack propagation to decrease its impact toughness. While complicated microstructure is found in HAZ forming ferrite and diverse austenite, such as grain boundary austenite (GBA), intragrain austenite (IGA), and Widmanstätten austenites (WA). A small amount of secondary austenite (γ2) and chromium nitride are also found in HAZ, and they significantly deteriorate its corrosion resistance. The grain boundary misorientation angle distribution of the austenite in WM is found to be dominated by the low angle boundaries (LABs). However, its content decreases from the WM to base metal (BM). Selective corrosion occurs in all samples, where ferrite is preferentially dissolved when the extrinsic voltage is low (<0.5 V) and austenite is preferentially dissolved when the extrinsic voltage is high (>0.5 V), indicating the different electrochemical activity of the two phases.

Development of novel double-side friction stir Z shape butt-lap welding process for dissimilar joining of 12 mm medium-thick Al/Cu plates

Medium-thick Al and Cu plates are commonly used in the power industry. However, it is difficult to achieve high-quality medium-thick Al/Cu dissimilar joints due to the formation of intermetallic compounds (IMCs) layer, which are typical Al2Cu, AlCu and Al4Cu9 phases. Although friction stir welding (FSW) is a suitable welding technique for joining dissimilar metals, the higher heat generation from a large tool shoulder when FSW of medium-thick plates significantly reduces the joint properties. Therefore, a novel double-side friction stir Z shape butt-lap welding (DS-FSZW) is proposed to join medium-thick Al/Cu dissimilar plates. The results indicated that the DS-FSZW reduces the thickness of the IMCs layer compared with conventional double-side FSW (DS-FSW). The maximum tensile strength and elongation of the DS-FSZW joint are 174.17 MPa and 7.32 %, respectively. While the maximum tensile strength and elongation of DS-FSW are 140.98 MPa and 6.2 %, respectively. It indicates the novel DS-FSZW can effectively increase the mechanical properties of the medium-thick Al/Cu dissimilar joints compared to DS-FSW.

Influence of backfilling rate on the stability of the “backfilling body-immediate roof” cooperative bearing structure

To reduce the cost of backfilling coal mining and utilize the underground space of coal mines, a new backfilling mining method with low backfilling rate called constructional backfilling coal mining (CBCM) is proposed. The “backfilling body-immediate roof” cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation. The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment. The control effect of CBCM is verified by a physic similar simulation test. The economic benefit of CBCM is analyzed. The conclusions are: the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory. Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata. The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%. The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%, with a decrease rate of 56.63% than the full-filling. The research results can provide theoretical support for the application of CBCM in coal mining.

Effect of Temperature and Material Flow Gradients on Mechanical Performances of Friction Stir Welded AA6082-T6 Joints.

The temperature and material flow gradients along the thick section of the weld seriously affect the welding efficiency of friction stir welding in medium-thick plates. Here, the effects of different gradients obtained by the two pins on the weld formation, microstructure, and mechanical properties were compared. The results indicated that the large-tip pin increases heat input and material flow at the bottom, reducing the gradient along the thickness. The large-tip pin increases the welding speed of defect-free joints from 100 mm/min to 500 mm/min compared to the small-tip pin. The ultimate tensile strength and elongation of the joint reached 247 MPa and 8.7%, equal to 80% and 65% of the base metal, respectively. Therefore, reducing the temperature and material flow gradients along the thickness by designing the pin structure is proved to be the key to improving the welding efficiency for thick plates.

Achieving high property medium-thick Ti/Al dissimilar joints by double side friction stir welding

Double side friction stir welding (DS-FSW) was used to join TC4 titanium alloy and 2024-T4 aluminium alloy having dissimilar medium-thick plates with a thickness of 8 mm. The microstructure and mechanical properties in medium-thick Ti/Al dissimilar DS-FSW joints were systematically studied. It revealed that the diffusion-type Ti/Al interface was mainly formed when the rotating speed is low. While intermetallic compounds layers were formed at the Ti/Al interface due to the high welding temperature and intense mechanical mixing at a relatively high rotating speed. The maximum tensile strength of medium-thick Ti/Al dissimilar DS-FSW joint is 265 MPa achieved at the rotation speed of 300 rev min–1, which is 58.9% of the base material of 2024-T4 aluminium alloy.

Research status of deep penetration welding of medium-thick plate aluminum alloy

Research status of deep penetration welding of medium-thick plate aluminum alloy

Stress and distortion of the 10 mm thick plate EH40 and 316L different butt joints in 10 kW laser welding

Residual stress has a negative influence on the service life of different welded joints between high-strength steel and stainless steel, especially in corrosive environment, it is very easy to cause fracture failure of welded joints. In this study, three types of medium-thick plate butt joints in single-pass full penetration laser welding, including EH40 & 316L, EH40 & EH40 and 316L & 316L butt joints, were deeply studied and verified by thermo-elastoplastic finite element method and experiments. The peak exponentially increasing double cone heat source model was used to calculate the transient temperature field. The relevant data of longitudinal, transverse residual stresses and angular distortion in three cases were extracted for comparative analysis. At the same time, the influence of the same material and different materials on the evolution mechanism of nodes stress in the weld was also discussed. It had been found that the geometric profile average error between the simulation and experiment in three cases was less than 0.5%. The stress state changes of the weld and its vicinity nodes in EH40 & 316L butt joint were faster than EH40 & EH40 and 316L & 316L butt joints. Compared with the welded joints of the same material, the welded joints of EH40 and 316L in the weld and its vicinity were remarkable differences in transverse residual stress, equivalent residual stress and angular distortion. The transverse residual stress gradient value of the EH40 side in EH40 & 316L was almost twice that of EH40 & EH40. The mismatch material properties of EH40 & 316L aggravated the generation of transverse tensile residual stress on the EH40 side. The results obtained in the current study were beneficial to the assessment of the integrity in the butt joints and the control of potential risks.

Prediction and analysis of key parameters of head deformation of hot-rolled plates based on artificial neural networks

In plate hot rolling, the prediction of head deformation of steel plates is crucial to improve the yield. In this paper, a novel prediction model based on neural networks for head deformation of medium-thick plates is proposed. The dataset of parameters of head deformation of medium-thick plates was established based on machine vision, and the artificial neural networks optimized by improved sparrow search algorithm (ISSA-ANN) was proposed to predict the irregular length and area of the head of finished medium-thick plates. During model parameters setting, mean error (MAE), root mean square error (RMSE), mean absolute percentage error (MAPE), and correlation coefficient (R) are used as the evaluation indexes. Results show that ISSA-ANN performs better than other models in this paper in predicting the head deformation of medium-thick plates. Meanwhile, the effect of key variables on head deformation is investigated and suggestions for improving the head shape of medium-thick plates are given according to the influence of key variables of the model.

Optimization of beam oscillation on macro/micro formation and mechanical property in low-expansion superalloy laser-welded joint

Low-expansion superalloys have been widely used in aerospace, ships, nuclear power fields due to the high strength and low expansion coefficient. Generally, laser beam oscillation was adopted to solve the defects including poor bead formation, inner pores, and solidification cracks in the weldment of GH909 low-expansion superalloys medium-thick plates. Therefore, the molten pool flow, joint formation, microstructure, and mechanical properties were systematically studied in this paper. Results showed that beam oscillation effectively stabilized the molten pool and keyhole inside, thus forming a well-formed joint without obvious pores. In tensile tests, the strength and elongation of the joint at 300 Hz were measured as 859.5 MPa and 38.6 %, significantly higher than those of laser joint (731.1 MPa and 17.9 %) with plenty of pores and cracks. The average microhardness of the fusion zone (FZ) using laser oscillating welding (LOW) was about 16 HV larger than that of single laser welding (SLW). In FZ, γ/Laves eutectic precipitated phase was distributed discretely without obvious solidification cracks. There existed coherent and incoherent interfaces between eutectic γ and Laves phases. Moreover, coherent interfaces were detected to account for 73.9 %, presenting a major fraction. The improvement of the mechanical properties of LOW joint was mainly caused by solid solution strengthening and precipitation strengthening. This research has a guiding reference for well-formed and high-quality low-expansion superalloy welding and relevant industrial application.

Numerical Model Developed for Thermo-Mecahnical Analysis in AlCrFeMnNiHf0.05–Armox 500 Steel Welded Joint

High entropy alloys are a new category of materials that contain at least four main chemical elements. One of the main advantages over the traditional alloys is the ability to maintain their properties at low or high temperatures. Researchers have investigated the possibility of welding these alloys so that they can be used in industrial applications. Good results have been obtained by welding butt joints of thin sheets, without the use of filler materials. In this paper it is investigated the possibility of welding overlap joints, with applications in the military field, of medium-thickness plates of AlCrFeMnNiHf0.05 high entropy alloy on an Armox 500 steel support plate, using filler materials available on the market. The research focuses on the numerical simulation of three welding processes commonly used in on-site repair operations, namely manual metal arc, metal inert gas, and tungsten inert gas.

INVESTIGATION OF LAYERED ORTHOTROPIC STRUCTURES BASED ON ONE MODIFIED REFINED BENDING THEORY

In the article, constructions made of orthotropic multilayer composite material, in particular, layered orthotropic plates are considered. Numerical modeling and analysis of the stress-strain state for the plates are carried out on the basis of one version for the refined theory of layered plates. The bending problems for plates of medium thickness and thin multilayer plates of symmetric and asymmetric structures are investigated. All studies are conducted taking into account the properties of orthotropy and multilayering for the composite material from which the plates are made. The general algorithm for the numerical calculation of the stress-strain state for layered plates with orthotropic layers is developed on the basis of the finite difference method. This algorithm is implemented on a PC by a software package.

A novel high-efficient welding technology with rotating arc assisted by laser and its application for cryogenic steels

To obtain high efficiency and good weld quality for medium thick steel plates, a novel welding technology of hybrid arc laser welding was proposed through rotating arc assisted by laser. Rotating arc provides heat to melt feeding wire and groove for high deposition and good fusion. Laser is helpful not only to arc rotating, but also to molten pool mixing. The proposed welding technology was used in the application of 9% Ni steel with medium thickness in the field of LNG storage tanks. The 21 mm thick steel plates were successfully achieved with only 2 welding passes. The weld formation was well-qualified, and no defects can be observed. The droplet transfer, keyhole and molten pool flow were investigated with high-speed camera and electric signal analysis. Experimental results showed that the droplet transferred in periodic alternation pattern of rotating spray transfer mode and short-circuit transfer mode. The laser keyhole kept stable during the droplet transfer process. The molten pool was fully mixed under the coupling effect of the arc, droplet and laser beam. The weld metal was in homogenous composition. Low temperature (−196 °C) impact energy of weld metal center and fusion line were much higher than related requirements. Obvious dimples on the fracture surface indicated that the fracture mechanism was in ductile fracture mode. Research results provided a theoretical basis for efficient construction and safe service of LNG containers made by cryogenic Ni steel.

Closed-loop control of medium-thickness plate arc welding based on weld-face vision sensing

In one-side welding with full penetration, the use of backing strips helps support molten weld metals, but increases manufacturing cycle time and cost. The backing-free welding technology is under investigation for medium-thickness structural components in the aerospace industry. Its crucial challenge is ensuring complete joint penetration and maintaining a suitable and stable backside bead width. This paper presents an innovative method of controlling weld formation based on weld-face vision sensing in arc welding. A standard laser triangulation setup is used to obtain images of weld pool, and a new weld-face feature ‘depression degree of the weld pool’ is proposed. An image processing procedure is developed to extract the depression degree of the weld pool from images in real-time. The depression degree of the weld pool is found to correlate closely with the backside bead width, and is a better indicator of the backside bead width than the weld pool width, with a higher consistency and a smaller time lag. Employing the depression degree as a feedback signal, a backside bead width control method is developed and implemented. Welding experiments on 6-mm-thick aluminum alloy 2219 plates show that the presented method is remarkably effective in achieving full penetration and keeping backside bead width constant.

Modeling and Simulation Analysis of Rigid-flexible Coupling Dynamics of Ramming Mechanism Based on Reissner-Mindlin’s Medium-thick Plate Theory

In order to obtain the dynamic characteristics of a ramming mechanism, the multi-rigid-body and rigid-flexible coupling dynamic models were established in Recurdyn. Considering the structural characteristics of the link, the deformation motion of the link is described by using the Reissner-Mindlin plate theory, and the dynamic model of a bomb feeder is established considering the influence of non-ideal factors such as transmission clearance, friction and so on, the dynamic characteristics of a bullet-feeding machine are simulated and analyzed. Compared with the multi Rigid body dynamics model, the simulation results of the rigid flexible coupling model are more consistent with the experimental results, in addition to the polygon effect, other factors such as transmission gap and so on are also the causes of the fluctuation of the chain head speed of the ammunition conveyer. In addition, with the periodical movement of the Ammunition Conveyer, the wear between the pin holes of the connecting links will become more and more serious, and the closer you get to the end of the chain, the greater the trend

Natural frequencies of plates of medium thickness

A comparison is made of the frequencies obtained by the classical theory of thin plates and the refined theory of plates of medium thickness. Considered a rectangular plate with articulation along the contour. To determine the fundamental frequency, the Bubnov-Galerkin variational method is used. It is shown that with a relative plate thickness h/a = 0.2, the calculation refinement is approximately 15-20% for the values of the fundamental frequency of natural vibrations of a rectangular plate.