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Laser cutting of carbon fibre reinforced plastics (CFRP) has shown promising potential as an alternative to conventional manufacturing processes. Laser cutting has major benefits of contactless and therefore wear-free machining and high automation potential. The main challenge is to reduce the heat input into the material during the process. Excessive temperatures cause damage within the surrounding matrix material and could locally modify the structural properties of the CFRP. For industrial use it is necessary to be able to predict the resulting temperature fields. To gain knowledge of the temperature distribution during the process, a three-dimensional macroscopic finite element model is developed using ANSYS simulation software. Transient-thermal analyses are performed and the material removal process is implemented via the element-death technique. Simulations are run for a unidirectional composite structure and different cutting speeds. The resulting temperatures are compared to experimental data. [ABSTRACT FROM AUTHOR]

The heat generated during welding induces a large temperature gradient in and around the welded area. In the arc welding process, three main different zones have been recorded in the welded joint: the fusion zone, the heat affected zone and the base metal. The objective of this article is to present the thermal cycle simulation technique and its usefulness for the study of the heat-affected zone. Rapid heating and cooling treatment was applied in specific simulation equipment. The most published research on using thermal cycle simulation to understand the heat affected zone is presented. A case study is also presented. An X70 steel was chosen to undergo thermal treatment cycles using the simulation equipment. It has been shown the importance of this technique for the study of HAZ. It was found that the microstructure of HAZ depends on the heating temperature. [ABSTRACT FROM AUTHOR]

Residual stresses and strains, distortions, heat-affected zone (HAZ), grain size changes and hardness variation during gas metal arc welding (GMAW), are fundamental aspects to study and control during welding processes. For this reason, numerical simulations of the welding processes represent the more frequently used tool to better analyse the several aspects characterizing this joining process with the aim to reduce lead time and production costs. In the present study, an uncoupled 3D thermo-mechanical analysis was carried out by two commercial finite element method (FEM) software to model an experimental single bead GMAW of AISI 441 at different processes set-up. The experimental HAZ and measured temperatures were used to calibrate the heat source of both the used numerical codes, then a validation phase was done to test the robustness of the two developed analytical procedures. One software was used to predict the residual stresses and strains and the distortions of the welded components, while in the second software, a user routine was implemented, including a physical based model and the Hall-Petch (H-P) equation, to predict grain size change and hardness evolution, respectively. The results demonstrate that the predicted mechanical and microstructural aspects agree with those experimentally found showing the reliability of the two codes in predicting the thermal phenomena characterizing the HAZ during the analysed welding process. [ABSTRACT FROM AUTHOR]

Maraging steels are ultra-high strength iron nickel-based alloys which are used in military applications like rocket motor casings, missiles, and ship hulls. In the current work, maraging steels of 250 grade butt joints with 2 mm thickness are welded by using Nd:YAG laser. The experiments were designed and conducted using the L16 orthogonal array. Various welding parameters selected for the current work are laser power, welding speed, and focal position, whereas tensile strength, hardness and depth of penetration were considered as the output responses. The influence of process variables on weld bead morphology was analysed experimentally. The microstructure, mechanical characteristics and numerical analysis of the optimum joint were also investigated. Analysis of variance (ANOVA) was used to determine the effect of different variables on tensile strength and depth of penetration. According to the results, laser power and welding speed are essential factors for tensile strength. The depth of penetration is strongly influenced by welding speed, focal position, and laser power. In order to predict the weld bead, finite element analysis was performed on ABAQUS 3D finite element software. The results reveal that finite element simulation and experimental observations are matched. [ABSTRACT FROM AUTHOR]

This paper reports an experimental investigation on continuous CO2 laser cutting of polymethylmethacrylate (PMMA) sheet. The influence of four process factors (laser power, cutting speed, assisting gas pressure and sheet thickness) on five process responses (kerf deviation, top heat affected zone, bottom heat affected zone, maximum surface roughness and rough area) has been investigated. The experimental plan was established based on Taguchi L18 mixed design. The kerf geometry and heat affected zones have been measured using polarising light microscopy technique, while the surface roughness was evaluated using 3D laser scanning confocal microscope. Regression models have been derived to correlate different process responses with different process factors. The cut surface could be classified into three zones: rough zone, moderate zone and soft zone. The rough area is increased by increasing gas pressure and laser power and by decreasing the sheet thickness and cutting speed. Increased kerf deviation has been observed at high cutting speed, laser power and gas pressure. High laser power and low cutting speed produced worst surface roughness and wide heat affected zone. Therefore, it is recommended to use low laser power and high cutting speed to minimize the heat affected zone and the surface roughness. However, increasing the cutting speed may result in high kerf deviation.

This study investigated the creep and creep crack growth (CCG) behavior of the base metal (BM), weld metal (WM), and heat affected zone (HAZ) in a Gr. 91 weldment, which was made by a shield metal arc weld process. A series of tensile, creep, and CCG tests were performed for the BM, WM, and HAZ at 550 °C. Creep behavior of the BM, WM, and HAZ was analyzed in terms of various creep laws; Norton’s power-law, Monkman-Grant relation and damage tolerance factor (λ), and their constants were determined. In addition, each CCGR law for the BM, WM, and HAZ was proposed and compared in terms of a C∗-fracture parameter. The WM and HAZ revealed faster creep rate, lower rupture ductility, and faster CCGRs than the BM, but they showed a similar behavior in the creep and CCG. The CCGRs obtained in the present study exhibited a marginal difference when compared with those of RCC-MRx of currently elevated design code in France. A creep crack path in the HAZ plane progressed towards a weak fine-grained HAZ adjacent to the BM.

In this research, the effect of the shielded metal arc welding (SMAW) process heat input upon the microstructure and development of the heat-affected zone in the dissimilar joint of API 5L X80/DS5 2205 steels was investigated by recording the thermal cycles with thermocouple implantation in the perpendicular direction of the weld line. The filler metal used (electrode) is DSS 2209. The microstructure of the base and weld metals and their interfaces at different heat inputs were investigated using the scanning electron microscopy/energy-dispersive spectroscopy analysis technique (SEM/EDS) and optical microscopy (OM). The results indicated that the interface between the base metals and the weld metal has excellent consistency and that there is no evidence of cracks at different heat inputs. By increasing the heat input, it was determined that the amount of secondary austenite in the weld metal and heat-affected zone of 2205 steel had been increased. There occurred an epitaxial growth at the interface of 2209/2205, and there were a fine transition zone and Type II boundaries at the interface of 2209/ API 5L X80. The areas containing coarse, fine, and partially fine grains were detected in the heat-affected zone of the X80 steel. The thermal cycle results determined that the temperature peak in the areas away from the fusion line had increased by increasing the heat input and that the heat-affected zone of the two base metals, particularly the X80 steel, had been extended further.

The objective of this study is to compare the performance for welded beam-column joints in aluminum structures using moment-rotation diagrams and to evaluate the influence of welding on joint rigidity. A nonlinear numerical calculation of welded beam–column joints is performed using the finite element method. Material and geometric nonlinearities were included in the model. The connection was analyzed for two cases: variants with and without welded stiffener plates. Two material models were used. The first was derived from the applicable standard for aluminum structures, while the other was based on the results of a previous material study and calibrated using a separate numerical calculation. From the results of the calculations, moment-rotation diagrams for different geometries and material properties of joints were constructed and compared. The obtained moment-rotation diagrams for the stiffened and unstiffened joints demonstrate that stiffening of the joints in aluminum structures improves the properties of the joint in terms of higher rigidity, resistance, and ductility, regardless of the existence of the heat affected zone.

In order to conceive command systems for welding equipment based on intelligence techniques similar to human thinking; it is better to use artificial intelligence methods, for example: Genetic algorithms and particle swarm optimization. Freshly, this latter has received increased attention in many research fields. This paper discuss the application of particle swarm optimization algorithm to optimize the welding process parameters and obtain a better Width of Head Affected Zone (WHAZ) in the welding machine which is gas metal arc welding. The effect of four main welding variables in the gas metal arc welding process, namely welding speed, welding voltage, nozzle-to-plate distance and wire feed speed on the WHAZ are studied. A source code is developed in MATLAB 8.3 to perform the optimization. [ABSTRACT FROM AUTHOR]

Laser dimple texturing has been a surge in the surface to surface contact applications like the cutting tool/workpiece interaction, piston-cylinder assembly, bearings, prosthetic hip & knee joints, blanking punch- die assembly, etc. to control the friction and wear between the interactions. In this article, the first part presented about a broad literature review on an effect of dimple texture in various industrial applications like bio-implant components and cutting tools. In the second part, detailed information has discussed on a process of laser dimple texturing and influence of laser process parameters such as laser wavelength, laser energy, number of pulses, pulse duration and focal distance on dimple geometry. The third part describes a comprehensive literature review on challenges/limitations of laser dimple texturing process like heat affected zone, tensile residual stresses, bulges around the dimple, etc. Finally, in the fourth part, proper attention has given on recent developments like laser shock peen texturing, laser texturing under water and post-processing techniques to overcome the limitations of laser surface texturing process. [ABSTRACT FROM AUTHOR]

Grain growth and hardness variation occurring in high-temperature heat affected zone (HAZ) during the welding processes are two thermal dependant aspects of great interest for both academic and industrial research activities. This paper presents an innovative finite element (FE) model capable to describe the grain growth and the hardness decrease that occur during the gas metal arc welding (GMAW) of commercial AISI 441 steel. The commercial FE software SFTC DEFORM-3D™ was used to simulate the GMAW process, and a user subroutine was developed including a physical based model and the Hall–Petch (H-P) equation to predict grain size variation and hardness change. The model was validated by comparison with the experimental results showing its reliability in predicting important welding characteristics temperature dependant. The study provides an accurate numerical model (i.e. user subroutine, heat source fitting, geometry) able to successfully predict the thermal phenomena (i.e. coarsening of the grains and hardening decrease) that occur in the HAZ during welding process of ferritic stainless steel. [ABSTRACT FROM AUTHOR]

Dual phase (DP) steels have high strength, while maintaining outstanding elongation capacities. This is possible using a well-controlled thermomechanical process that produces a perfect phase combination in the DP microstructures. However, automotive makers are required to weld the DP steels, which generates a soft zone in the microstructure. In this work, 1.6 mm-thick DP980 steel sheets were welded by gas metal arc welding process to analyze the response of the welded soft zone to cyclic loading conditions. Conducted macrographic and metallography analyses revealed good quality in the appearance of the welded joints, with a complete fusion of the DP980 joint and without the presence of discontinuities. Low cycle fatigue tests of the DP welded joints were conducted under a constant amplitude strain control mode. The welded joints experienced a fatigue life reduction with respect to the DP980 steel of ~16% at strain amplitudes of 0.2, 0.3, and 0.4%. For strain amplitudes larger than 0.6%, the fatigue life of the welded joint was reduced by 39%. Weld thermal cycles combined with metallography analysis indicated that a tempered process of the martensite during the welding was responsible for the soft-zone formation and the poor fatigue response. [ABSTRACT FROM AUTHOR]

Creep resistant 9% Cr steels are frequently used in civil engineering projects of supercritical coal‐fired power plants operating at temperatures of superheated steam around 610 °C. This work focus on analysis of microstructure degradation and degradation of mechanical properties of orbital narrow‐gap welding of P91 and P92 steels. Nowadays welding technology of orbital narrow‐gap using tungsten inert gas is not limited to welding of high‐pressure steam pipelines. This method is highly productive and efficient and leads to an increase in productivity, quality, and repeatability of welding process. It replaces the original method of manual welding with coated electrode into a standard bevel, which is a time‐consuming process that costs a high amount of weld metal. Welds are degraded at 650 °C/30 000 h without applied stress and the effect of degradation is evaluated across the weld based on the observed changes in microstructure and hardness. Attention is focused mainly on precipitation and coarsening of Laves phase in the main areas of heat affected zone (HAZ): coarse grain HAZ, fine grain HAZ, and intercritical HAZ. The results show that frequency and rate of Laves phase coarsening in the fine grain and coarse grain HAZ are higher than in the base material. [ABSTRACT FROM AUTHOR]

The aim of the study is to improvise mechanical properties-tensile strength and microstructure behaviour of the material when the Resistance Spot Welding (RSW) is used to combine two metal-stainless steel (SUS316L). Constant nugget diameter needs to be maintained; thus, the constant parameter is needed by setting up 2.5 kN load with 5 kA 25 cycle as an optimum parameter. However, RSW the material absorbs high volumes of energy; hence it causes the material properties retarded. Therefore, post heat treatment (annealing) is used to treat the heat-affected zone of the welded diameter by manipulating the temperature of heat-treated, holding time and the heat rate. Tensile and microstructure tests are conducted to investigate the effectiveness of treatment analysis. It is found that annealing heat treatment improves the ductility of the material.

Underwater Friction Stir Welding (UFSW) is a solid-state joining technique which uses a non-consumable tool to weld metals. The objective of this investigation is to evaluate the mechanical properties of the AA5052 Aluminium alloy joints prepared by UFSW. The effect of different type of welding tools and welding parameters on the weld joint properties are studied. Square, tapered cylindrical and taper threaded cylindrical type of welding tools have been used to produce the joints with the tool rotational speed varying from 500 rpm to 2000 rpm while the welding speed varying from 50 mm/min to 150 mm/min. Tensile strength, micro-hardness distribution, fracture features, micro-and macrostructure of the fabricated weld joints have been evaluated. The effect of welding process parameters that influences the mechanical properties and fracture characterization of the joints are explained in detail. A maximum Ultimate Tensile Strength (UTS) value of 222.07 MPa is attained with a gauge elongation of 14.78%. Microstructural evaluation revealed that most of the fracture are found on the thermal mechanically affected zone (TMAZ)adjacent to the weld nugget zone (WNZ) due to bigger grain sizes. It is found that most of the joints exhibit ductile characteristics in failure. Fractography analysis has been used to find the behavior of weld joints in failure.

Additive manufacturing of continuous carbon fibre-reinforced polymer (CCFRP) parts enables the production of high-strength parts for aerospace, engineering and other industries. Continuous fibres allow for parts to be reinforced along the load path, multiplying their mechanical properties. However, current additive manufacturing processes for producing CCFRP parts do not optimally meet the requirements of the matrix. With resin- and extrusion-based processes, the time-consuming and costly post-processing required to remove support structures severely limits design freedom, and producing small batches requires increased effort. In contrast, laser sintering has proven to be a promising alternative in an industrial environment, allowing the production of robust parts without support structures in a time-efficient and economical manner for single and small-batch production. Based on a novel laser-sintering machine with the automated integration of continuous fibres, a combination of the advantages of the laser-sintering process and the advantages of continuous fibres is to be achieved. This paper describes an experimental analysis and optimisation of this laser-sintering machine using design of experiments. The processing time for fibre integration could be reduced by a factor of three compared to the initial state.

The quality and integrity of welded joints is highly influenced by the optimal combination of the welding input parameters. Due to the rapidly changing scenario in the manufacturing industry, optimization of process parameters is essential for a manufacturing unit to respond effectively to the severe competitiveness and increasing demand for quality products in the market. An attempt is made to study the effect of heat input parameters properties of Tungsten Inert Gas (TIG) welding process. The application of the surface plot in the investigation of the combined effect of input parameters on heat input and heat affected zone was pursued in this study. The central composite design matrix was used to obtain data from sets of experiments. Mild steel coupons measuring 60mm x 40mm x 10mm were welded with tungsten inert gas welding process. This study developed a model using expert systems, such as Response Surface Methodology and Artificial Neural Network to optimize and predict weld heat input and heat affected zone from input parameter such as current, voltage and welding speed. With the data collected from twenty experimental runs in this study, the result from one Response Surface Methodology analysis shows that a current of 130.00Amps, voltage of 20.94V, speed of 0.48m/min will produce heat input of 0.64277Kj/mm and heat affected zone of 5.42078mm with a desirability of 0.962. [ABSTRACT FROM AUTHOR]

The work presents the results of research on the structure of welded joints in the area of heat affected zone (HAZ). Based on precisely performed metallographic tests, the contribution of individual structural components in the area of welds of pipes welded with the induction method was assessed. The volume fraction of individual structural components in various areas of the heat affected zone, the size of the grain formed in the welding process, as well as its shape coefficients were determined. On the basis of metallographic observations, an attempt was made to describe the course of the pressure induction welding process, taking into account the structural changes, phase changes and the recovering and recrystallization processes taking place in this process. [ABSTRACT FROM AUTHOR]

Laser-based pre-heating of laser beam welding with a 3D scanning optics, applied to AISI 1045 steel, is studied. Laser beam welding of heat-treatable steel is challenging due to martensitic hardening in combination with defects. Pre-tempering aims the reduction of the cooling rates and martensitic microstructure within the weld seam. An oscillating defocused laser beam was guided over the surface for pre-heating by means of a 3D scanner optics. During pre-heating, the laser power, the scanning speed and the number of cycles were varied. Welding with 4000 W and 2 m/min with a focused laser beam was executed. Thus the resulting temperature profile behind the ongoing laser beam and cooling time T8/5 between 800 °C-500 °C was significantly extended. Two parameter combinations (15 cycles j600 Wj50 mm/s(²) and 10 cycles j800 Wj50 mm/s²) succeeded in a microstructure of bainite and martensite. By extending the cooling time T8/5 to 3.11 s(²) and 4.17 s². Thus, average hardness for laser based pre-tempering of 487 HV 0.5(2) and 455 HV 0.52 was achieved. As a reference, global pre-heating at 400 °C using a heating plate can reduce the average hardness of the weld zone from 729 HV 0.5 at room temperature to 304 HV 0.5 at a cooling time T8/5 of 5.63 s. [ABSTRACT FROM AUTHOR]

Abstract In order to explore the effect of different the welding heat input on microstructure and impact properties in coarse grain zone in heat affected zone (CGHAZ) of ultra-low carbon bainitic steel welded joint. In this paper, Gleeble-3500 thermal simulation testing machine was used to simulate different heat input, to study the effect of linear energy on the microstructure and impact toughness of the CGHAZ of Q420qEN steel joint. The scanning electron microscope (SEM), oscillographic impact microscope and transmission electron microscope (TEM) were used. The results show that the microstructure of CGHAZ is mainly the lath bainite and granular bainite. When the welding heat input is 30kJ•cm-1, the CGHAZ grains have obvious growth phenomenon. With the increase of the welding heat input, the grain size also grows. Meanwhile, as the welding heat input increases from 18kJ•cm-1 to 30kJ•cm-1, the impact toughness of the CGHAZ of joint increases first and then decreases at -20°C.

Carbon fiber-reinforced composites are widely used in automobile, aerospace and military lightweight manufacturing due to their excellent mechanical properties such as light weight, excellent fracture resistance, corrosion resistance and wear resistance, etc. However, because of their high hardness, anisotropy and low interlayer strength characteristics, there are many problems with machine carbon fiber-reinforced composites with traditional methods. As a non-contact processing technology, laser machining technology has lots of advantages in carbon fiber-reinforced composites processing. However, there are also some defects produced in laser machining process such the heat affected zone, delamination and fiber extraction due to the great difference of physical properties between the carbon fibers and the resin matrix. To improve the quality of carbon fiber-reinforced composites laser machining, lots of works have been carried out. In this paper, the research progress of carbon fiber-reinforced composites laser machining parameters optimization and numerical simulation was summarized, the characteristics of laser cutting carbon fiber-reinforced composites and cutting quality influence factors were discussed, and the developing trend of the carbon fiber-reinforced composites laser cutting was prospected.

Nowadays, additive manufacturing (AM) is a powerful way to make complex-shaped components for airspace engineering from nickel-based superalloys. So, while nickel-based superalloys could easily be we L-DED in sheet-metal thicknesses, they suffered from strain-age cracking and solidification during AM or in the post-weld aging treatment. This is attributed to the fact that besides the limitation of γ′- phase forming elements (Al and Ti), as they form by AM very rapidly and reduce ductility, the majority of the superalloys contain carbide-forming elements such as Cr, Mo, and W. The precipitation of carbides, which is very effective in strengthening, develops cracks in the heat-affected zone (HAZ) during AM. The difference in isochoric heat capacities and the thermal expansion coefficient (TEC) at the phase boundary leads to the appearance of dangerous local destruction energy. If the area of the interfacial interface is sufficiently extended, then the accumulation of this energy reaches a level sufficient for a crack formation. We have proposed a crack initiation criterion (CIC) for assessing the dangerous level of fracture energy. The CIC was derived from an estimate of the local energy balance from the heat transfer equation for the two-phase area. Practical approbation of the criterion was carried out after L-DED of samples from Ni50Cr33W4.5Mo2.8TiAlNb (EP648) alloy powder with an increased carbon content based on the study of the chemical composition near the crack formed during solidification. Using the proposed criterion provides an opportunity to give the rank to carbide-forming elements according to the degree of their influence on the fracture energy. Thus, the release of aluminum carbide turned out to be 5.48 times more dangerous than the release of titanium carbide and more than 5 times more dangerous than the release of tungsten carbide and molybdenum.

In addition to traditional chip methods, performance lasers are often used in the field of wood processing. When cutting wood with CO2 lasers, it is primarily the area of optimization of parameters that is important, which include mainly laser performance and cutting speed. They have a significant impact on the production efficiency and cut quality. The article deals with the use of an artificial neural network (ANN) to predict spruce wood cut characteristics using CO2 lasers under several conditions. The mutual impact of the laser performance (P) and the number of annual circles (AR) for prediction of the characteristics of the cutting kerf and the heat affected zone (HAZ) were examined. For this purpose, the artificial neural network in Statistica 12 software was used. The predicted parameters can be used to qualitatively characterize the cutting kerf properties of the spruce wood cut by CO2 lasers. All the predictions are in good agreement with the results from the available literary sources. The laser power P = 200 W provides a good cutting quality in terms of cutting kerf widths ratio defined as the ratio of cutting kerf width at the lower board to the cutting kerf width at upper board and, therefore, they are optimal for cutting spruce wood at 1.210−2 ms−1.

Bimetallic structures processed via laser-based additive manufacturing (AM) efficiently combine multiple materials in single components, which are difficult to achieve using traditional methods. However, limited understanding exists on how processing parameters influence the resulting microstructures and thermal profiles of base material during processing, affecting component performance. To this end, we present a combined numerical and experimental study on the effects of input laser power and scanning speed on the heat-affected-zone (HAZ) and fusion-zone (FZ) of a tantalum-titanium bimetallic structure, two compatible materials that are challenging to process traditionally and are desirable in a bimetallic system. We demonstrate that a wide array of track characteristics can be achieved by varying the laser power and scanning speed. The HAZ and FZ microstructures' width and depth within the underlying Ti6Al4V substrate can be estimated within 6–19% of the experimentally determined values using a 3D transient-thermal finite element analysis (FEA) model, with the most significant errors occurring at low scanning speeds. Adjusting the absorptivity input to the model improves prediction to within 1–11% difference of the HAZ/FZ dimensions and corresponding temperatures relative to the experimental dimensions across a broad range of laser power and scanning speeds. Our results indicate that the underlying temperatures achieved in bimetallic components can be predicted accurately using a detailed FEA approach, aiding larger-scale approaches towards improved process modeling and manufacturing of bimetallic structures using laser-based AM.

Laser Beam cutting is a type of non-conventional machining process in which the removal of materials takes place due to the melting and vaporization of material when the laser beam comes in contact with it. This work examines the impact of the cut quality characteristics of the SS347 material and to find reduced surface roughness, machining time and heat affected zone by laser beam cutting. The cutting process was assisted by CO2 gas pressure. Power, standoff distance, speed and CO2 gas pressure are the cutting parameters considered for this study and the output parameters measured are machining time, heat affected zone and surface roughness. In accordance with L-9 orthogonal arrays, the experiments were planned. Analysis of Variance has been used to study how input functions influence output functions which revealed that speed (59.75% and 89.75%) is the significant factor for machining time and surface roughness while power (91.27%) was the dominant factor for heat affected zone. Gas pressure did not have much influence in the output parameters. The mathematical expressions of the output are used as input for the multi-objective function of the genetic algorithm. Optimal solutions are compared to hybrid and without-hybrid functions. It is found that the hybrid function shows a higher performance compared to the without hybrid function. [ABSTRACT FROM AUTHOR]

Fiber reinforced composites, also referred as fiber reinforced plastics (FRPs) have gained considerable importance in engineering applications due to their unique qualities like high strength and stiffness at lesser weight, chemical inertness, thermal resistance, corrosion resistance, and electrical resistance. Though the machining of FRPs is not recommended, many times it is inevitable and the primary machining process like drilling is essential. This can cause delamination of the fibers thereby adversely affecting the mechanical properties of the composite and requires additional secondary finishing operation. The present investigation explores electrochemical discharge machining (ECDM) as a one of the novel technique to remove the delaminated fibers from such composites. Using ECDM the protruded delaminated fibers from a drilled hole in FRP have been precisely eliminated. Two different approaches viz. top machining and inside machining were followed for this purpose. Process evaluation was done in terms of its ability to remove the delaminated fibers and the extent of thermal damage (heat affected zone and hole overcut) to the workpiece. Both approaches have shown considerable potential of removal of delaminated fibers precisely. [ABSTRACT FROM AUTHOR]

Water medium harms the quality of welded joints and their mechanical properties. One of the effective ways for solving this problem is the application of the effect of external electromagnetic field on a liquid metal pool. The aim of carried investigations is the determination of the efficiency of use of external electromagnetic effect for the regulation of structural transformations in wet underwater welding with flux-cored wire. As determined, the width of crystalline particles can be reduced nearly two times and grains of the weld metal and heat affected zone close to a fusion line can be 1.3-1.4 time refined. As shown, the application of external electromagnetic effect prevents the appearance of gradients of grain size along the fusion line from face to weld root. [ABSTRACT FROM AUTHOR]

• A critical size for base metal grain size could be defined, above which grain growth does not occur outside the FL. • In spot laser welding, critical grain size is independent from laser power density. • In continuous laser welding processes, the heat input per unit length of the weld controls critical grain size. • As heat input per unit length of the weld decreases, critical grain size decreases. • The heating step is more crucial in the HAZ grain growth in both spot and continuous welding processes. One of the biggest challenges in the welding of strengthened alloys by grain refinement is the grain growth phenomenon in the heat-affected zone (HAZ), which would result in the degradation of mechanical properties. The goal of this study is to comprehend the HAZ evolution in the fine-grained aluminum alloy during laser welding as a low heat input process. Spot laser welding of fined grain 1050 aluminum alloy revealed that grain growth and HAZ formation occurred in samples with 4 µm grain size, but no grain growth occurred outside of the fusion line (FL) in larger grain samples. The microstructure of HAZ was simulated using the numerical phase-field technique. The numerical model's findings demonstrated that a critical grain size (D cr) for the base metal can be established, above which grain growth would not occur outside FL. To predict grain size distribution outside FL, an analytical model was also used. According to both models, as grain size increases, the HAZ width decreases, and above a critical grain size, no HAZ will form outside of FL. In spot welding, D cr was independent of power density but for continuous welding processes, D cr has a direct relationship with heat input per unit length of weld. Moreover, HAZ grain growth mainly occurred in heating step for both types of processes. [ABSTRACT FROM AUTHOR]

In this study, high-carbon, chromium alloy steel (100Cr6) having the initial spheroidized microstructure was welded using the rotary friction welding method. The effects of process parameters such as friction time and friction force were experimentally investigated. The friction welded joints were produced of two 100Cr6 steel rods. In order to examine the microstructure and mechanical properties of the friction welded 100cr6 steel joints, tensile and hardness tests were conducted. The microstructure of weld zone was examined by optical microscopy. It was found that after cooling, martensitic structure is obtained at the core and periphery of the weld joint. It was found that the tensile strength of friction welded samples is increased with increasing time and force of friction up to a certain level and then decreases again. Hardness measurements show a higher hardness at the centre of the weld joint in comparison with its periphery.

Plasma jet cutting process is a well-known nonconventional thermo-electrical manufacturing process that is widely used in metal and shipbuilding industry. It uses the energy of highly ionized gas to cut various types of metal materials. Cutting process is determined by technological parameters whose values define the final cut quality results. Cut quality can be defined considering different characteristics such as: kerf width, bevel angle, surface roughness, dross height and heat affected zone. In this paper, a research on the influence of variable process parameters on the heat affected zone (HAZ) was conducted. An investigated material was aluminium alloy EN AW 5083. HAZ analysis was done by measuring hardness changes on the specimen cross sections and by microscopic observation of the material structure.

In a creep damage analysis for a weld joint (WJ) using a damage model, it is important to select a damage model that properly reflects complex conditions of stress generated in the interface between the base metal and the heat-affected zone (HAZ). For 2 1/4Cr1Mo steel, we examined what type of scalar stress is appropriate to properly reflects the conditions of stress generated around the HAZ for accurately predicting creep rupture time, in the framework of the time exhaustion rule, which evaluates damage as a function of stress. For a specimen of a round rod WJ through which an HAZ penetrates obliquely, we compared actual tests and finite element method (FEM) analysis, in temperature-stress ranges from 120 to 160 MPa at 823 K, and from 80 to 100 MPa at 873 K. Using FEM calculations, we evaluated the rupture time based on the time exhaustion rule, considering three types of scalar stress: the maximum principal stress, the equivalent stress, and the Huddleston stress. Comparing with the tests, we found that the scalar stress that gives an appropriate rupture time is the Huddleston stress. In this stress, the damage accumulation due to the creep deformation in the base metal (BM)-HAZ interface and the cavity formation due to the hydrostatic pressure are taken into account. Analyses of the stress distribution inside and outside of the HAZ and in the BM-HAZ interface indicated that, for the 2 1/4Cr1Mo steel, the cavity formation due to the tensile hydrostatic pressure is also important when we evaluate damage. We optimized a parameter b, which regulates the balance in the Huddleston stress, so that the observed results are reproduced with the determination coefficient of R2 = 0.948, and we obtained the value of b as b = 0.34. [ABSTRACT FROM AUTHOR]

Laser beam percussion drilling (LBPD) can create high density holes in aerospace materials with the repeated application of laser pulses at a single spot. In this study, one-parameter-at-a-time approach has been used to investigate the individual effect of peak power, pulse width and pulse frequency on geometrical accuracy and metallurgical distortion during LBPD of 0.85 mm thick Ti–6Al–4V sheet using 200 W Yb:YAG fiber laser. It has been found that the output parameters behave differently at the higher and lower values of a particular input process. The increase of pulse width from 1 to 1.50 ms increases hole taper by 20% whereas the same corresponding change from 1.50 to 2.00 ms reduces the taper by 20%. The increase of pulse frequency from 10 to 50 Hz reduces hole circularity by 40% but the same proportionate change from 50 to 90 Hz reduces circularity by 79%. Increase of peak power from 1.70 to 2.0 kW increases hole taper by 8% but the corresponding increase from 2 to 2.30 kW is 143%. [ABSTRACT FROM AUTHOR]

The drilling of carbon fiber reinforced plastic (CFRP) components is a preliminary step within the assembly of airplanes or cars. The usage of CFRP brings along different challenges and opportunities due to the heterogeneous material characteristics. Laser cutting of thermoplastic composites can lead to distinctive heat affected zones (HAZs) if the process parameters are not optimized regarding the specific boundary conditions and material characteristics. During cutting, the matrix material gets molten and solidifies again. Further heat input beyond what is needed for cutting can lead to the deterioration of the matrix material. As a result, process strategies are normally developed to reduce the HAZ to a minimum. Such strategies can be used for adapting the process and generating a selective heat input in the interaction zone of two components during the drilling process. Adapting the process can also be used to weld components together. Unlike other more common efforts to reduce the HAZ, this study's goal was to adapt the process so that two thermoplastic CFRP plates lying upon another can be welded during the cutting process. The developed process shows potential for the preliminary fixation of components in assembly processes by finding an optimum between reachable tensile force and resulting HAZ. The investigations were performed with CFRP plates with a thickness of h = 2.4 mm and a drilled hole with a diameter of d = 5 mm. The results demonstrate the possibility of welding the laminates while reducing the HAZ width to values below b = 300 μm. Tensile tests were performed with the joined specimens to determine the resulting tensile load. Cutting the hole with parameters typically used to minimize the HAZ result either in no weld seam or in a weak weld seam, which breaks at minimum force before tensile testing. Cutting parameters resulting in a distinctive HAZ generate tensile forces of up to F = 5.82 kN within the observed process window. Furthermore, strategies were investigated allowing a defined heat input only within the transition between the two plates. With this adapted strategy, tensile forces in the range of F = 1 kN could be realized. For these samples, the major HAZ width was located in the welding area with decreasing HAZ width for the upper and lower plates. [ABSTRACT FROM AUTHOR]

The back-surface field (BSF) layer obtained through the laser fired contact (LFC) process is the key to increasing the efficiency of solar cells. In this paper, we studied the optimization of LFC process parameters—focusing on laser frequency, influence, and speed—to achieve good ohmic contacts, and to reduce the heat-affected zone (HAZ). As frequency increases, interactions between the laser and particles increase, with the particles becoming overly heated. This generates the thermal effect, in which heat is transferred to particles not directly affected by the laser—resulting in the HAZ becoming wider and deeper. Under different laser power conditions, depths of approximately 18 and 8.3 μm were observed at laser speeds of 10 and 100 mm/s, respectively. This analysis of performance variables allowed us to identify those best suited to forming an Al-BSF layer approximately 1.2 μm thick, which resulted in the best LFC procedure while minimizing the HAZ area. HAZ size was minimized at a frequency of 400 kHz, using 5 W laser power, and a laser speed of 100 mm/s, while the best cell characteristics were obtained using a laser pitch of 500 μm and a single laser process. [ABSTRACT FROM AUTHOR]