Workpiece Thickness Research Articles

Hybrid approach for parametric optimization of wire-electrochemical spark micromachining of borosilicate glass

This work intends to implement a hybrid strategy for the multiobjective optimization of a wire-electrochemical spark micromachining (WECSMM) process, integrating the Taguchi technique and response surface approach. Initially, the optimum level of process variables, such as, thickness of workpiece, feed velocity of wire, concentration of electrolyte, and applied voltage, are evaluated using the characteristic loss function of Taguchi. After the process variables are optimized, the response surface model is built and refined using the central values that represent the best values. An experimental plan for borosilicate glass slicing was carried out during WECSMM, utilizing the L9 Taguchi design process. For simultaneous optimization, the two attribute criteria like surface roughness ( Ra) and material removal rate (MRR) have been chosen. When comparing the outcomes of a single strategy with the hybrid approach, the results demonstrate a significant increase in both quality aspects. As contrasted to Taguchi Methodology (TM), the couple approach was shown to increase MRR by 192% and lower Ra by 10%, respectively.

Automatic Defects Recognition of Lap Joint of Unequal Thickness Based on X-Ray Image Processing.

It is difficult to automatically recognize defects using digital image processing methods in X-ray radiographs of lap joints made from plates of unequal thickness. The continuous change in the wall thickness of the lap joint workpiece causes very different gray levels in an X-ray background image. Furthermore, due to the shape and fixturing of the workpiece, the distribution of the weld seam in the radiograph is not vertical which results in an angle between the weld seam and the vertical direction. This makes automatic defect detection and localization difficult. In this paper, a method of X-ray image correction based on invariant moments is presented to solve the problem. In addition, a novel background removal method based on image processing is introduced to reduce the difficulty of defect recognition caused by variations in grayscale. At the same time, an automatic defect detection method combining image noise suppression, image segmentation, and mathematical morphology is adopted. The results show that the proposed method can effectively recognize the gas pores in an automatic welded lap joint of unequal thickness, making it suitable for automatic detection.

ANALYSIS OF THE THERMAL FRICTION DRILLING PROCESS FOR EFFECTIVE PARAMETRIC CHOICE ON THE DRILLING OF AISI 304 STAINLESS STEEL USING THE FUZZY AHP-MOORA METHOD

Attaining effective quality control of drilled samples in thermal friction drilling is a challenge considering the disproportionate allocation of drilling resources to parameters. Therefore, it is essential to select the appropriate parameters and allocate their scarce resources based on requirements. This paper chooses the effective and the best parameters of the drilling process during the processing of AISI 304 stainless steel using the fuzzy-AHP-MOORA method. The analytic hierarchy process is deployed by stating the criteria and alternatives. A pairwise comparison is made with the outcome introduced into a fuzzy framework which interpretes the obtained values from an input to an output vector via a rule (linguistic the terms) set. The result is expressed as responses to options compared to the objectives as ratios. The input parameters are the feed rate, friction angle, rotational speed, friction contact area proportion, tool cylindrical region diameter and workpiece thickness. In turn, the responses are the roundness error, radial force, dimensional error, axial force, bushing length and hole diameter. It was found that experimental trials 12, 14 and 8 with the respective differences between beneficial and non-beneficial values of 0.2133, 0.2076 and 0.1083 obtained the respective positions of 1st, 2nd and 3rd. The discretized fuzzy weights place the bushing length as the best while the second position is shared equally by all the other responses. The model was successful in reducing the imprecision in the parameters and the greatly improved response was the bushing length.

Stepwise double-sided friction stir welding: an alternative for root defect mitigation in aluminium plates with lower gauge numbers

Penetration-induced fractional unbonded defects and flow-induced root flaws are part of the discontinuities of the conventional friction stir welded (FSW’ed) aluminium alloys with limited impact assessment/clarification in literature. The novelty of this study lies in the attempt to eliminate penetration-aided root defect via a stepwise double-sided welding process as well as identify its impact on loadbearing. As a result, the stepwise double-sided FSW welding of a thick aluminium plate (6 mm) was carried out while the microstructure, strength, and fracture modes of the ensuing welds were compared with the conventional (single-sided) friction stir welded counterparts. The stepwise double-sided FSW-welded joint demonstrated better tensile strength relative to the single-sided FSW-welded counterparts owing to its material flow consolidation (two-side deformation) and elimination of penetration-induced fractional unbonded region/root defect. The welding processes do not have a noteworthy influence on the fracture location of the welds as failure ensued via the stir zones of the respective welds. Transient breaking/brittle appearance, and ductile fracture modes were noticed in the single-sided and stepwise double-sided FSW-welded samples respectively. The stepwise double-sided FSW process is recommended as a better choice for thick workpieces relative to conventional FSW to improve the weld’s loadbearing resistance.

Effects of Oxide Powders as Activating Flux on AMIG 304L Welds

Activating metal inert gas (AMIG) welding was designed to address difficulties with MIG welding, such as the limitation on workpiece thickness that may be welded in a single pass. This investigation was carried out on 304L stainless steel using ER 308L as a filler metal. Five oxides (SiO2, TiO2, Fe2O3, Mn2O3, and Cr2O3) have been investigated without edge preparation. The welded joints were evaluated for weld morphology, microstructure, mechanical properties, and corrosion, and the findings were compared. The depth of the AMIG weld was determined to be greater than that of the MIG weld. The microstructure is composed of austenitic and retained delta ferrite with 3.3% for MIG and up to 8% for AMIG weld carried out with Cr2O3 oxide flux, the tensile strength is up to 604 MPa when using Cr2O3 oxide against MIG weld (532 MPa), and the resistance to sudden load in AMIG welds (189 J/cm2) is higher than that of MIG weld (149 J/cm2). The corrosion resistance of the weld made with Fe2O3 oxide flux is greater than that of the other AMIG and MIG welds, as well as the parent metal. The AMIG welding technique variant enhances productivity and decreases the cost and energy consumption of the welding material compared to the traditional MIG process. This allows for joining the same thickness without affecting mechanical properties and corrosion resistance, meeting the industry’s requirements.

Improving the technology for restoring worn parts based on cold plastic deformation

Technological control scheme for forming worn parts during their restoration by deforming broaching is proposed. Particular attention is paid to the study of the stress-strain state, which provided the conditions for creating the necessary plastic flow of the product material towards the worn areas and made it possible to compensate the wear amount in these areas of the product and provide an allowance for subsequent machining. Taking into account the peculiarities of parts restoration technological process, the relationship between the required circumferential strain of the outer surface and the total tension on the hole is established. The influence of the number of deforming elements that perform the required deformation on the accumulated strain on the inner surface of the part was investigated. This made it possible to establish that the maximum accumulated strain of the inner surface is provided by the maximum number of elements with a minimum tension on the element. On the outer surface, the value of the accumulated strain does not depend on the number of deforming elements, but is determined only by the total tension and the workpiece thickness. Based on the simulation of deforming broaching in a wide range of changes in operating parameters, tool geometry and workpiece thickness, an analytical dependence was obtained to determine the angle that ensures the absence of axial strains when the workpiece is deformed. The necessary broaching modes and tool geometry were determined, which will ensure the required dimensions of the machined or restored part.

Machinability analysis of Albromet W130 copper alloy by WEDM

The unconventional wire electrical discharge machining (WEDM) technology represents a vital manufacturing technology in different industrial branches, such as aviation, military, automotive or energy industry. The WEDM energy demand is considerable and it is, therefore, desirable to reduce the machining time by optimising the machining parameters. In the study, the chosen parameters were Pulse off time, Gap voltage, Discharge current, Pulse on time, and Wire feed. Another factor we investigated in our Box-Behnken design of the experiment was the workpiece thickness. The cutting speed, topography, and surface morphology were analysed in the samples produced for the design of the experiment. This investigation was carried out using electron microscopy. The chemical composition of individual spots was analysed as well. The samples were found not to have significant differences in the appearance of craters on the edge and in the centre. Similarly, there was no significant difference observed between thicknesses and different parameter settings. The surfaces also show a large number of small bubbles. There were, however, no cracks or other defects found, even in the cross-sections of all samples.

Validation of Hole-Drilling Residual Stress Measurements in Workpieces of Various Thickness

BackgroundA recent revision to the ASTM E837 standard for near-surface residual stress measurement by the hole-drilling method describes a new thickness-dependent stress calculation procedure applicable to “thin” and “intermediate” workpieces for which strain versus depth response depends on workpiece thickness. This new calculation procedure differs from that of the prior standard, which applies only to thick workpieces with strain versus depth response independent of thickness.ObjectiveHerein we assess the new calculation procedures by performing hole-drilling residual stress measurements in samples with a range of thickness.MethodsNear-surface residual stress is measured in a thick aluminum plate containing near-surface residual stress from a uniform shot peening treatment, and in samples of different thickness removed from the plate at the peened surface. A finite element (FE) model is used to assess consistency between measured residual stress across the range of sample thickness.ResultsMeasured residual stress varies with sample thickness, with thinner samples exhibiting smaller near-surface compressive stress and a larger gradient of subsurface stress. These trends are consistent with both observed bending (curvature) of the removed samples and the trend in FE-calculated expected residual stress. The measured and expected residual stresses are in good agreement for samples of intermediate thickness, but the agreement decreases with sample thickness. Measured residual stress is invariant with gage circle diameter.ConclusionThe new thickness-dependent stress calculation procedure for hole-drilling provides meaningful improvement compared to thick-workpiece calculations.

Symmetrical Martensite Distribution in Wire Using Cryogenic Cooling

This article presents the results of research on a new combined process involving multi-cycle wire-drawing and subsequent cryogenic cooling after each deformation stage. For theoretical research, modeling in the Deform software was performed. The analysis of temperature fields and the martensitic component in all models showed that for both considered thicknesses, the most effective option is a low deformation velocity and the conduct of a process without heating. The least effective option is to use an increased thickness of the workpiece at an increased deformation velocity and the conduct of a process without of heating to ambient temperature, which acts as a local cooling of the axial zone of the workpiece with an increase in the workpiece thickness. An analysis of laboratory studies on this combined process revealed that in the absence of intermediate heating of a wire between deformation cycles, 100% martensite is formed in the structure. However, if intermediate heating to 20 °C between deformation cycles is carried out, a gradient distribution of martensite can be obtained. And, since the wire has a circular cross-section, in all cases, martensite is distributed symmetrically about the center of the workpiece.

Experimental Investigation of Optimal Welding Parameters and Mechanical Properties of Shielded Metal Arc Welded Mild Steel Plates

This study focuses on achieving enhanced mechanical properties of the welded joints, which is critical for the applications of mild steel (MS) plates in various industries. In this regard, a systematic approach is used to adjust welding parameters such as welding current and workpiece thickness in shielded metal arc welding (SMAW), with the objective of identifying the optimal combination that maximizes weld quality. The experiments were planned with the help of Taguchi’s L9 orthogonal array method in order to reduce experimental cost and time. The weld quality is optimized by determining the signal-to-noise ratios of weld penetration, tensile strength, impact strength, and microhardness for each experimental sample. As a result, 110 A welding current is obtained as the optimal SMAW parameter for a 5 mm thick MS IS 2062 Grade B plate. This optimized result has also achieved 394.78 N/mm2 tensile strength and 53 J of impact resistance for the respective specimen. Besides, research not only enhances understanding of the SMAW process but also offers practical implications for industries requiring high-performance welded joints in MS structures. Additionally, this study can assist upcoming researchers in optimizing any existing welding procedures.

Modeling for plastic instability in multi-directional rotary forging of thin-walled components with three ribs

Multi-directional rotary forging has the great potential to form thin-walled components with three ribs because of its incremental deformation characteristic and smaller forging load. However, for the components with thin-walled sterna and thick ribs, the plastic instability is easier to occur at the bottom of thick ribs in multi-directional rotary forging, resulting in the waste of components. Therefore, the aim of this paper is to establish the model for predicting plastic instability in multi-directional rotary forging of thin-walled components with three ribs. Firstly, the models for calculating actual and critical radial stresses on both sides of rib are established by analyzing complicated stress states caused by time-varying thinning deformation of sterna and thickening deformation of rib. It is found that the critical radial stress is mainly determined by ratio of deformation energy and external force work, while the actual radial stress is mainly determined by dissipated power and metal flow velocity. By combining actual and critical radial stresses, a unified model for simultaneously predicting plastic instability of ribs at different positions is proposed. Then, the influence laws of different technical parameters on critical conditions of plastic instability are revealed. It is found that the plastic instability is mainly determined by initial thickness of workpiece and width of rib, i.e., the critical deformation amount increases with increasing initial thickness of workpiece or decreasing width of rib, and vice versa. Finally, the experiments are conducted to verify that the proposed model for predicting plastic instability in multi-directional rotary forging of thin-walled components with three ribs is reliable. This paper provides a guideline to establish the model for predicting plastic instability under complicated stress states and metal flow modes.

Development and parametric study of reversible motion-wire electrochemical spark machining (RM-WECSM) setup for micro-width curve profile cutting on Al2O3 epoxy nanocomposites

The development of wire electrochemical spark machining setup is always challenging in the form of industrial viable for machining advanced engineering materials such as polymer nanocomposites, quartz, glass, ceramics, etc. Because of some drawbacks associated with it, like irregularity in kerf width, poor surface finish, no spark formed at high wire velocity, wire breaking at high voltage, etc. In the present work, a newly developed hybrid machining process that is reversible motion-wire electrochemical spark machining (RM-WECSM) has been developed for curve profile cutting, especially on non-conducting workpieces such as aluminum oxide epoxy nanocomposite of 3.5 mm thickness. The effect of NaOH concentration, applied voltage, reversible wire velocity, pulse on-and-off time, on material removal rate and average surface roughness have been studied using a one-parameter-at-a-time approach. Sparking occurred from the electrolyte surface to 10 mm above the electrolyte surface to cut the workpiece. The spark length is equal to the workpiece thickness. A continuous, stable spark has been formed at a high reversible wire velocity (19.8 m/min). Simultaneously, self-electrolyte flow has been generated, due to which melted materials have been washed out of the cut-surface and provided the smooth (1.987 µm) cut-surface of the workpiece. The maximum MRR is found as 1.63 mg/min. Thermal cracks, heat-affected zones and recast layers were not found on the curve cut-surface, and it was analyzed by a field emission scanning electron microscope.

Optimization of process parameters in plasma arc cutting of commercial-grade aluminium plate

Abstract Plasma arc cutting (PAC) has emerged as a versatile and efficient method for the precision cutting of various materials, including commercial-grade aluminium plates. The optimization of process parameters is crucial for achieving high-quality cuts, minimizing material wastage, and enhancing overall productivity. This study aims to systematically investigate and optimize the key process parameters in PAC of commercial-grade aluminium plates. The experimental design involves the manipulation of parameters such as arc current, gas pressure, and workpiece thickness. A Design of Experiments approach, specifically Taguchi’s orthogonal array, is employed to efficiently explore the parameter space and identify the optimal combination of settings. The response variables considered for optimization include minimum surface roughness, minimum burr height, and maximum material removal rate (MRR). Analysis of variance is performed to get the percentage influence of each process parameter on the performance characteristic. The results obtained from the optimization process are expected to provide valuable insights into enhancing the efficiency and precision of PAC for commercial-grade aluminium plates. Arc current is found to be the most significant parameter in altering the surface roughness. The thickness of the material is the most significant parameter in altering burr height. None of the parameters is found to be significant in altering the MRR from Analysis of Variance analysis. From signal-to-noise ratio analysis and average performance graph, the optimum combination of processes in altering the bur height and MRR are found as arc current at 50 amp, the gas pressure at 5.4 bar, and the thickness of the workpiece at 6 mm.

Application of plasma cutting in mock-up experiments for decommissioning of internals in heavy water research reactor

The dismantling of internal components within the reactor is one of the primary technical activities in the reactor decommissioning project. Currently, the first nuclear reactor in China, heavy water research reactor (HWRR), is in the phase of decommissioning. By integrating the characteristics of the HWRR with both domestic and international cutting technology experience, plasma cutting has been identified as a suitable and commonly used technique for cutting the reactor internals. Considering that the decommissioning process of nuclear facilities is irreversible, it is essential to conduct mock-up experiments to acquire cutting performance parameters for the cutter prior to decommissioning of the reactor internals, which not only helps optimize the decommissioning plan but also provides data support for decommissioning practices. Based on the characteristics of the outer shell, within the HWRR, parameters such as cutting current, workpiece thickness, cutting speed, working angle, and nozzle standoff were selected for the plasma cutting experiments. Through orthogonal experiments, cutting current, workpiece thickness, and cutting speed were identified as key factors influencing the performance of plasma cutting. Based on the previous research, the maximum cutting speed and workpiece quality loss under various cutting conditions were determined through special experiments. Finally, using the outer shell mock-up of the HWRR as the experimental object and combining it with the decommissioning path provided by simulation, it was demonstrated that the optimal operating parameters obtained from the previous experiments can be successfully applied to practical outer shell cutting.

A Study on Welding of Porous Metals and Metallic Foams

Metal foams are lightweight materials with exceptional impact energy absorption and unique thermal properties. Integrating these novel materials into large structural components requires developing appropriate welding techniques that preserve their bulk performance. Traditional fusion welding methods are ill‐suited for metal foams due to their porous structure, which tends to be filled during welding, compromising performance. This study focuses on solid‐state welding techniques, including friction stir welding (FSW) and induction welding, to join metal foams without adversely affecting their cellular structure. The results reveal challenges with FSW; it generates excessive heat during welding, filling the foam's porosities and disrupting its cellular structure. In contrast, induction welding is an effective method for joining composite metal foam (CMF) panels without compromising their structural integrity. The matrix between the porosities in CMF facilitates the penetration of eddy current, promoting the induction welding process. The mechanical properties of the weldments are studied through uniaxial tensile tests, while microstructural characterization of the weldment is evaluated using scanning electron microscopy. The results provide insight into the effect of various welding parameters (e.g., welding temperature, workpiece thickness, and welding environment) as well as the suitability and restrictions of such welding methods in joining CMFs.

Probing the impact of process variables in laser-welded aluminum alloys: A machine learning study

This paper presents a pioneering approach, Bayesian machine learning (ML), for the estimation and characterization of critical laser welding features in Aluminum alloys, encompassing peak temperature, heat-affected zone width, and bead aspect ratio. The methodology involved constructing a laser welding database utilizing finite element simulations (FEM). The distinctive advantage of the Bayesian ML model lies in its capability to address challenges associated with excessive approximation and to account for uncertainties in parameters. This results in precise and resilient predictions of laser weld parameters across a spectrum of aluminum alloys. The findings underscored the model's efficacy in forecasting output targets, although regression analysis unveiled unique characteristics in data distribution and outliers specific to aluminum alloys. These outliers were primarily linked with the melting range of aluminum alloys, leading to the Al7075 alloy having the lowest prediction, and the Al1100 alloy the highest within the ML model. Additionally, the normalized average weight functions of input parameters were illustrated, clarifying their differing importance concerning diverse types of Al alloys in precisely forecasting output objectives. In light of these explanations, it remains consistent that laser power (LP) and welding speed (WS) inputs hold substantial sway across all alloys, while workpiece thickness (WT), beam diameter (BD), and initial temperature (IT) played comparatively lesser roles. Ultimately, this work contributes to a more profound comprehension of the relationships between input features and the geometrical and thermal behavior of laser-welded Al joints.

Study of Wire-Cut Electro-Discharge Machining of Heat-Resistant Nickel Alloys.

This paper presents an analysis and theoretical model for assessing the quality and accuracy of wire-cut electro-discharge machining (WEDM) of products made from novel heat-resistant nickel alloys such as CrNi56KVMTYB. It is observed that WEDM processing of Ni alloy led to high surface roughness for the thick specimens, and electrical parameters such as pulse duration for the selected range depict an insignificant role in the value of surface roughness. On the other hand, the cut width of the machined surface decreases as the pulse duration increases, while the cut width is elevated for thick workpieces. Secondary discharges developed in WEDM have negative effects that cause sludge adhering and deterioration in the quality and productivity of processing. The regression model is developed to predict the surface roughness and cut width of machined surfaces, which holds significant importance in modern engineering. The workpiece is examined for surface integrity and material deposition. It is observed that an increase in the height of the specimen leads to the occurrence of secondary discharges, which in turn results in the formation of cracks on the surfaces of high-temperature nickel alloys. These cracks have a detrimental effect on the performance of critical products made from next-generation heat-resistant nickel alloys.

Control of corner arc radius in wire electrochemical micromachining

Wire electrochemical micromachining (WECMM) technology is commonly used to process micro parts. Some thick parts contain many sharp structures, and have high machining accuracy requirements for the arc radius at the corner, such as jet sheet, micro gear, etc. However, when machining thick workpiece, it is easy to form a large arc radius at the corner due to stray corrosion and difficult discharge of electrolytic products. In order to solve this problem, this paper proposes a corner path optimization method, which reduces the arc radius of the sharp structure by adjusting the processing path of the wire electrode, thereby improving the machining accuracy of the sharp structures. The model of the relationship between the inclination of the machining path and the angle of the sharp structure is established. The inclination and offset distance of the processing path are obtained through theoretical calculation, and further optimized through experiments to avoid overcut or undercut at the corner. In the experiment, tungsten wires with different diameters were used as wire electrodes to process acute angle, right angle and obtuse angle structures on 510 μm thick 9Cr18Mo stainless steel. The influence of wire electrode processing path on the corner arc radius of different angle sharp structures was explored. The experimental results show that compared with the original path, the arc radius of the sharp structure could be reduced from tens of microns to <5 μm by using the optimized processing path.

Optimization of silica sand abrasive parameters on machining of glass plate in AJM using Taguchi method

Fine abrasive blasting of glass materials is widely used in the micro-electromechanical systems and biomedical industries. Creating high-quality holes in these materials requires precise control of the input parameters. In this study, experimental and optimization study was performed to assess the impact of various parameters during abrasive jet machining (AJM) on material removal rate (MRR), where SiC is used as the abrasive particle. Experiments were performed in line with the Taguchi experimental design where L9 orthogonal array was selected to understand the influence of nozzle diameter, standoff distance (SOD), and work piece (glass) thickness on MRR. It was observed that the material removal rate was proportional to the abrasive particles’ kinetic energy. Among the considered parameters viz. nozzle diameter, standoff distance, and work piece thickness, nozzle diameter exerted most significant effect on MRR followed by SOD and work piece thickness. Highest MRR, 0.0143 g/sec, was observed at SOD of 2.05 mm, nozzle diameter of 3 mm and work piece thickness of 4 mm. The researchers can follow the same methodology and determine the efficiency of industrial wastes possessing high hardness as abrasive particles, thereby, contributing additionally towards ecology protection.

Effects of Variated Final Temperature and Workpiece Thickness for Hot Rolling of Aluminum Alloy EN AW-8011

Hot rolling in the process chain of aluminum-rolled products presents the critical element of material quality and influences productivity. To increase the letter demand modifications of hot rolling, the consequential changes of microstructure, crystallographic texture, and mechanical and formability properties must be acknowledged and consistently considered when planning the rolling process and rolled product. Achieving lower thicknesses of the hot-rolled band would enable fewer passes with cold rolling; consequently, hot rolling with the same number of passes can be completed with lower temperatures. Microstructural and texture characterizations conducted using the light microscope and scanning electron microscope, respectively, of the 3.25 mm hot-rolled band revealed that the smaller grains appeared in the center of the cross-section, unlike for the 6 mm hot-rolled band, where smaller grains were detected on the top and bottom positions of the cross-section. Furthermore, the comparison also shows that the 6 mm hot-rolled band had 64% of random texture components and 83% of recrystallized grains, whereas the proportional adjustment for the 3.25 mm hot-rolled band had 42% of random texture components and 55% of recrystallized grains. For the mechanical testing results, the elongation values in rolling and transverse directions significantly differ only in the case of a hot-rolled band of 3.25 mm. Consequently, the earing results are more than 1.5% higher for the 3.25 mm hot-rolled band, than the 6 mm hot-rolled band.