Successive Passes Research Articles

Feasibility Study of Solid-State Recycling through Direct Hot Rolling of AA5754 Aluminum Chips for Automotive Applications

Recently, researchers have done a lot of efforts to develop new solid-state recycling processes, both experimentally and developing numerical models. This kind of process is energy-saving and environmentally friendly compared to the conventional aluminum recycling process because avoided the melting step. The purpose of this work is to evaluate the feasibility of an innovative solid-state recycling process through direct hot rolling in a non heat-treatable aluminum alloy for automotive applications. AA5754 chips have been produced by turning a bar without the usage of lubricants and compacted with a 150 kN load; the compacted billets were treated at 400 °C and directly hot rolled in several successive passes. Rolled samples are then analyzed in terms of Vickers microhardness and microstructure in both as-rolled and heat treatment conditions, this last was performed at 185°C simulating the process of paint-bake. The produced samples show an excellent bonding between chips.

Experimental study and finite element modelling of pure copper tube fabrication via the Parallel Tubular Channel Angular Pressing (PTCAP) Process

The Parallel Tubular Channel Angular Pressing Process (PTCAP) has emerged as a promising method for refining the grain structure and enhancing the mechanical properties of metallic materials through severe plastic deformation. This study focuses on a comprehensive investigation of the PTCAP process, combining experimental and numerical analysis to gain insights into its underlying mechanisms. Experimental investigations involve processing a commercially pure copper tube using PTCAP under controlled conditions. In parallel, an explicit numerical analysis is developed using ABAQUS software to simulate the deformation behavior during PTCAP. The model incorporates material constitutive equations and accounts to describe the material response under high strain rates and large deformations. The research aims to investigate how multi-pass PTCAP affects hardness, strain homogeneity, and stress distribution. A comparison between the load punch from the experimental and FEM is conducted to validate the FEM results, and there is a good correlation between both. Hardness measurements are conducted at various stages to quantify the changes in material hardness resulting from the successive PTCAP passes. The hardness of the Cu tube increased by 63.45, 94.51, 103.98, and 105.64% after 1 to 4 passes, respectively.

Restoration of continuous casting machine mold copper plates made of Cr–Zr bronze using multi-pass friction stir lap welding

An innovative technology has been developed and implemented for the restoration and manufacturing of new mold copper plates for continuous casting machines (CCMs) using wear-resistant composite coatings. These copper plates significantly surpass the service life of imported copper plates featuring galvanic coatings, sometimes by up to 20 times. However, the pressing challenge of restoring the copper plates of molds once they have reached the minimum permissible thickness remains unresolved. This study aimed to explore the feasibility of restoring a plate composed of precipitation-hardening Cr–Zr bronze with the same material by employing friction stir lap welding (FSLW). The objectives were to examine the structure, quality, and hardness of the welded joint, alongside investigating the impact of heat treatment (quenching and aging). By utilizing multi-pass FSLW method with a rotating tool crafted from a heat-resistant alloy and overlapping (partially overlapping) successive passes, a welded joint with a thickness of ~5 mm was achieved, devoid of critical continuity flaws (cracks or voids). Within the bronze layer restored through FSW, a softening effect ranging from 85–105 HV1 was observed compared to the initial hardness of the bronze in its hardened and aged state while in service (116–126 HV1). This is attributed to recrystallization and overaging, specifically the coarsening of chromium particles within the Cr–Zr bronze due to the heating of the weld nugget (stir zone) to 600–700 °C. The observed softening effect during FSW can be effectively rectified through heat treatment involving dissolution of the hardening phases followed by aging, resulting in a hardness increase to approximately 120–150 HV1. The process of restoring copper plates to their original thickness via the progressive and environmentally friendly FSW method, followed be the subsequent application of wear-resistant composite coatings, presents the opportunity for an almost infinite operational cycle of molds. This advancement could potentially eradicate the necessity for Russia to rely on importing such molds copper plates.

Thermo-physical phase field model of laser powder melting additive manufacturing of 2D layered stainless steel structures

Additive manufacturing (AM) techniques based on laser melting of metal powders are experiencing tremendous growth and are rapidly becoming the preferred processing approach for metal parts. However, the effect of the different processing variables on microstructural and mechanical property outcomes is not yet fully understood. Modeling and simulation can provide an inexpensive and expedient way to probe the large parameter space and identify the most important correlations between processing degrees of freedom and output products. In this work, we develop a two dimensional thermo-physical phase model of laser melting additive manufacturing that captures solidification and melting, heterogeneous nucleation, and oriented grain growth to simulate layered microstructures grown by melting a metal layer connected to the underlying substrate by a set of orientation relations. The model solves the Allen-Cahn and heat diffusion system of equations on structured meshes, and simulates the motion of a laser spot across the specimen through a sequence of successive passes. The simulations best replicate the formation of columnar structures, as under high-power laser conditions or under rapid solidification kinetics, in good qualitative agreement with experimental observations. Our approach connects processing variables with the microstructural outcomes, thus capturing the effect of important inputs such as laser spot size, laser scan speed, and cross hatch fraction on grain size and structure.

Modeling the Vibratory Compaction Process for Roads

This paper presents results obtained for the vibratory compaction process of road structures, in which the natural soil is used for the foundation infrastructure. The experiments and the optimization of the compaction process were carried out on five road lanes in Transilvania, Romania. A self-propelled single-drum roller compactor, BOMAG BW 213 S-5, was used for the compaction, layer by layer, with six successive passes over each layer. For each layer, the initial degree of compaction was measured, and after the fifth pass, it achieved the value prescribed in the road construction project. After each pass over the same layer, its settlement increased due to the plastic deformation and the soil’s rigidity receiving discrete higher values. This is how five different discrete values for rigidity were obtained. Modeling the compaction process is carried out using the Kelvin–Voigt model, with discrete variable experimental values for soil rigidity and assumed constant viscous damping values. Based on the two-degree-of-freedom linear elastic model, graphs were plotted for vibration amplitude variation and for the force transmitted to the soil when the excitation pulsation varies continuously and the soil rigidity varies discretely. There is a relationship between the initial and final degree of compaction values in the ratio that was proven to be dependent on the ratio of amplitude values corresponding to the final and initial roller passes cycle. The result is a useful relationship for the “in-situ” estimation of the compaction process effect. The novelty of this research is that it demonstrates the change in soil rigidity values after each pass of the vibratory roller and, thus, the increase of its settlement (plastic deformation) and the “slipping” for the amplitude resonance peak by discrete increasing values. Calibration of the resonance vibrations regime in accordance with the degree of compaction determined by geotechnical methods for “in-situ” sample prelevation stands as a fast and efficient method for the evaluation of the final degree of compaction value. This is, implicitly, the method for estimating the number of vibratory roller passes in the road construction project. In conclusion, the novelty of the research consists in the fact that, through using the resonance response of the vibratory roller, a correlation was made with the degree of compaction achieved after each pass.

Colocation in Time and Space of High-Precision Two-Way Optical and Microwave Observations for Calibration of a Microwave Ranging Link—The ACES Mission Case

The ACES mission of the European Space Agency combines optical and microwave-based geodetic observation techniques with highly accurate atomic clocks to achieve a new level of accuracy for geodesy and fundamental physics applications. In addition, the combination of two high-precision measurement techniques provides an even more exciting insight into their errors. Fundamental physics is particularly interested in experiments that require high precision between the results of the successive passes of a satellite. An example of such an experiment is the determination of gravitational redshift. Geodesy applications, in contrast, require both high accuracy and precision. Especially for applications like precise ranging or time synchronization, all possible error influences must be characterized and determined with high precision. Therefore, electronic delays of microwave link terminals pose a challenge to achieving high accuracy. They must, therefore, be calibrated, and the stability of the electronic delays must be monitored. While optical observation techniques can be calibrated sufficiently on the ground, the calibration of microwave measurements before a launch is not precise enough, and continuous monitoring is also not possible. In this study, four calibration methods were tested, all based on colocating optical and microwave measurements onboard a satellite and on the ground. The results of two methods achieved the required accuracy of 100 ps for time synchronization, with a mean error and standard deviation of better than 4 ps and 55 picoseconds, respectively. Correlations between the measured parameters were identified, and the impact of the different approaches on accuracy was investigated. It will be shown that the satellite-based colocation of two different geodetic observation techniques has clear advantages, and the calibration results achieved the required accuracy for geodetic applications in this simulation study.

Uncertainty quantification of satellite InSAR‐monitoring of bridges: a case study

AbstractTraditional structural health monitoring (SHM) systems provide accurate and objective information to assess the condition state of bridges; however, they are expensive and typically installed only on strategic bridges. Innovative technologies offer a potential solution. Interferometric Synthetic Aperture Radar (InSAR) takes multiple satellite radar images of a given area over time and extracts displacement time series of reflective point targets on the ground. The literature on InSAR‐based SHM of bridges lacks systematic studies aiming at quantifying the metrological uncertainty of the displacements measured. Furthermore, the topographic context and the magnitude of displacements of these structures between successive satellite passes significantly impact the uncertainty of results. This paper aims to evaluate the effectiveness of InSAR‐based SHM of bridges by comparing displacement time series obtained from InSAR with those from an on‐site topographic system. Displacements are measured from a prestressed concrete bridge in the Alpine region. Moreover, this study models the deformed shape of the bridge based on satellite and on‐site measurements and compares the results to determine whether bridge distortions can be reconstructed using satellite data alone.

Force estimation in flow forming of Al6101 T6 stepped cylinder-experimental analysis and mathematical modelling

Flow forming is a cold-forming process that is widely used for fabricating axisymmetric products. The present paper tries to propose a mathematical formulation for the flow forming of a stepped cylinder. An analytical model based on the upper bound method has been proposed. The mathematical formulation was then validated with the experimental trial on Al6101 T6 material. Forward flow forming operation was employed with a single roller assembly. The present investigation showed that the flow-forming forces depend significantly on axial forces while the circumferential forces were found to be less significant. The circumferential force was found to be much lesser than the axial force. The measured radial force was found to be within 20% of the measured axial force. The experimental trial showed the force variation in the process increased with thickness reduction per pass but the trend was not uniform. The increase in force in successive passes was found to be less than the previous pass for similar thickness reduction. The differences between the predicted force and experimental force were within 11%.

Numerical Investigation of Step Size Effect on Formability of 2024-T3 Aluminum in Incremental Forming

Incremental forming (IF) is an advanced manufacturing process in which a forming tool locally deforms sheet material into a desired geometry through successive passes at incremental depths. An inherent benefit to the IF process is its formability improvement over conventional stamping; however, further enhancements will enable the forming of increasingly complex geometries. To progress the IF process towards heavy industrial use, the modeling of such processes must be further developed. Single point incremental forming (SPIF) of AA2024-T3 was modeled herein utilizing explicit formulations. The model geometry featured a nominally rectangular-shaped clamping region. A friction factor was experimentally determined and utilized within the model, which is a novel addition to this work. Formability was determined and forming limit diagrams were composed. It was found that the present model shows greater formability and underestimates plastic strain compared to experimental testing. The generation of forming limit diagrams for this material processed by IF is also a novel addition to this field.

Fluctuations in local shear-fault energy produce unique and dominating strengthening in metastable complex concentrated alloys

Local chemical short-range ordering (SRO) and spatial fluctuations of planar fault energy are important features of multi-element and metastable complex concentrated alloys (CCAs). Arising from them, dislocations in such alloys are distinctively wavy in both static and migrating conditions; yet, such effects on strength have remained unknown. In this work, molecular dynamics simulations are used to show that the wavy configurations of dislocations and their jumpy motion in a prototypic CCA of NiCoCr are due to the local fluctuations of the energy of SRO shear-faulting that accompanies dislocation motion, with the dislocation getting pinned at sites of hard atomic motifs (HAMs) associated with high local shear-fault energies. Unlike the global averaged shear-fault energy which in general will subdue on successive dislocation passes, the local fluctuations in the fault energy always remain in a CCA, thus offering a strength contribution that is unique in such alloys. Analysis of the magnitude of this form of dislocation resistance shows that this is dominating over contributions due to elastic misfit of alloying elements and is in good agreement with strengths predicted from molecular dynamics simulations and experiments. This work has unfolded the physical basis of strength in CCAs, which is important for the development of these alloys into useful structural materials.

Structure and Mechanical Properties of Titanium Processed by Twist Extrusion and Subsequent Rolling

The article considers one of the combined methods of severe plastic deformation (SPD), which includes twist extrusion (TE) and subsequent rolling. The use of combined forming methods is promising for industrial use. Titanium grade 1 was used as a material in the experiments. Rolling was carried out in three stages with a decrease in temperature from 350°C to 180°C for a number of passes with one heating. The accumulated strain degree was e = 4.6 at twist extrusion and e = 3 in rolling. Increasing the reduction per pass decreases the number of heatings and increases the efficiency of the rolling process in whole. At the same time, it is necessary to set the maximum processing modes at which recrystallization processes do not occur in the billet. When rolling, the deformation degree in one pass was taken in the range of 5–20% with an increase in successive passes. The use of such deformation degrees allowed reducing the grain size in titanium grade 1 significantly. Twist extrusion reduces the grain size to 300–500 nm. Subsequent rolling allowed reducing the size of structural elements to 50–100 nm and provided a significant increase in the mechanical characteristics of the billet material (up to 869 MPa) while maintaining satisfactory ductility (up to 11.6%). It was found that increasing the deformation degree in one pass up to 40% at cross-rolling and simultaneously increasing the temperature to 385°C led to a decrease in the UFG structure quality and reduced strength of the deformable material by starting the dynamic recrystallization process.

Applying the Virtual Fields Method to Measure During Milling the Through-Thickness Residual Stress Distribution in Aluminum-Alloy Sheet Material

Residual stresses often cause distortion to occur when machining slender workpieces like those used in aeronautics. This distortion is undesirable and may even cause the workpiece to be scrapped. Identifying these residual stresses during machining is therefore crucial to limit their effect on the final geometry of the part. The aim of this work is to identify the through-thickness residual stress distribution by processing displacement/strain fields measured on the workpiece during machining. Digital Image Correlation is employed to measure, between successive milling passes, the displacement and strain fields on the lateral surface of the workpiece. These fields are then processed with the Virtual Fields Method to identify the through-thickness residual stress distribution. Compared to previous studies on this topic, no assumption is made concerning the real through-thickness displacement field. Simulations performed with synthetic data provided by a finite element model show the feasibility of this approach and quantifies its robustness when displacements are affected by measurement noise. Results obtained with this approach in a real case are then compared with their counterparts obtained with another identification technique, which assumes that the workpiece behaves as a beam. This study shows that it is possible to measure the through-thickness distribution of residual stress in slender workpieces during machining by using a classic subset-based DIC software and the Virtual Fields Method to process the displacement/strain maps. This opens the way for future developments aimed for instance at updating in live machining sequences in order to obtain machined parts immune from distortions caused by residual stresses.

The effect of laser-texturing configurations on the interfacial resistance of carbon reinforced aluminium laminate

ABSTRACT Laser ablation can be incorporated for surface treatment of carbon-reinforced aluminium laminate (CARALL) with environmental benefit as compared to chemical treatments. In the present research, laser surface structuring with different patterns was implemented on the aluminium substrates. The effect of laser-texturing pattern on the performance of CFRP/Al (carbon fiber reinforced polymer/aluminium) interface was investigated by undertaking lap shear, modes I and II interlaminar fracture tests. The laser surface structuring developed micro topography on the metal adherent and enhanced the interfacial area, mechanical interlocks, fiber bridging and cohesive failure in the CFRP/Al interface. The X-pattern with six successive passes of laser ablation offered the highest laser surface coverage (85.6%), leading to the improvement of lap shear strength, mode I and II critical interlaminar fracture toughness as high as 40, 110 and 52%, respectively, as compared to the chemical treated samples.

Assessment of the compaction effect and operational characteristics of a crawler tractor based on a rheological approach

BACKGROUND: At considering the issues of crawler tractors interaction with soil the determining factor is the time-varying impact of loads on the soil layer, its stressed and strained state, which, in turn, directly depends on its stress-strain properties. The properties assessment should be carried out with a rheological approach, which allows to explain many phenomena and processes and to develop new high technologies in terms of the criterion of minimizing the impact on the soil.
 AIMS: Studying the compacting ability of a crawler tractor in a configuration in various machine-tractor units, obtaining a curve for the effect of the traction load on the tractor hook, tractor speed and tractor mass redistribution over the lower track wheels on changes in soil compaction due to developing deformations, the coefficient of running resistance and skidding of the crawler-mounted mover.
 METHODS: The evoluation method for compaction impact of crawler-mounted mover on the soil layer was developed on the base of the previously constructed a general mathematical model for determining ways of reducing the compacting impact of crawler-mounted movers on the bearing surface, computer calculation programmes and the carried out assessment for the deformation development and changes of soil compaction under the crawler track.
 RESULTS: There are presented the simulation results of the process with an assessment of the developing dependences of the crawler tractor rut depth and its sliding on the travelling speed and on the displacement of the center of pressure at different loads on the hook, that obtained with the developed metod of analysis and the well-known theory of hereditary creep of elastic-visco-plastic materials. At the same time, the development of vertical and shear deformations of the soil layer in the area of lower track wheels impact is separately analyzed.
 The analysis of the constructed dependencies allows to identify a number of patterns for changes of compacting effect indicators of a crawler tractor on the soil with an assessment of the influence of the main design and technological parameters on them. It is established that taking into account the rheological characteristics of the soil layer and its state parameters permit significantly improve the accuracy of calculations for vertical and shear deformations of the soil layer and its final compaction after successive passes of the crawler lower track wheels. At the same time, the desired indicators behavior is ambiguously at passes of various lower track wheels.
 CONCLUSION: The conducted studies contribute to the optimal selection of parts for various machine-tractor units based on a specific crawler tractor, which perform the appropriate technological operations in certain conditions of work at specific parameters of the soil state.

Optimization of Mechanical Properties and Manufacturing Time through Experimental and Statistical Analysis of Process Parameters in Selective Laser Sintering

A statistical analysis of the response of the parameters has been led by a design of experiments to extract the most influential parameters in the selective laser sintering process. The parametric study was carried out by varying five parameters on the SLS machine and by looking at their influence on five groups of responses relating to the physical, mechanical, and thermal properties as well as to the printing duration. The mathematical models of the response surfaces were established by linking the responses to factors and their interactions. The model of regression uses not only the interaction between regressors but also nonlinear logical functions. These statistical models were used to define an optimal set of parameters. The geometry and density of specimens made of polyamide 12 confirm that increasing the distance between successive laser beam passes allows a significant manufacturing time reduction. The mechanical properties depend mostly on laser power and scan count. We conclude that a low laser power applied twice can improve the properties of the printed part. By optimizing the laser parameters, the targeted mechanical properties are obtained with over 33% of production time savings.

The effect of laser surface structuring patterns on the interfacial resistance of aluminum joints bonded with epoxy adhesive

Laser ablation can be incorporated for surface treatment of adhesively bonded joints with environment benefit as compared to chemical treatments. In the present research, laser surface structuring with different patterns were implemented on the aluminum substrates. The effect of laser texturing pattern on the bond performance of aluminum/epoxy adhesive joint was investigated by undertaking lap shear, modes I and II interlaminar fracture tests. The laser surface structuring developed micro-nano topography on the metal adherent and enhanced the interfacial area, mechanical interlocks and cohesive failure in the interface of bonded joint. The X-pattern with six successive passes of laser ablation offered the highest fraction of cohesive failure, lap shear strength, modes I and II strain energy release rates. In addition, the results of laser surface treatment were compared with those of an alkali-acid chemical treatment on the Al adherent. The laser treatment as compared to the chemical treatment presented superior bond performance in the aluminum/epoxy adhesive joints.

Process design and microstructure-property evolution during shear spinning of Ti2AlNb-based alloy

Rotationally symmetric workpieces of Ti2AlNb-based alloys have great potential for high-temperature service condition in aviation industry, while the poor workability limits their application until now. In this study, shear spinning and heat treatment were first conducted to investigate the corresponding microstructure evolution and mechanical properties of Ti2AlNb conical workpieces. The microstructure of the 1st and 2nd pass spun workpieces (SP1 and SP2) mainly consisted of B2 + retained α2 phases. After two passes spinning, the B2 phase texture changed from <111>//ND of as-received alloy to be <001>//ND. The ultimate tensile stress (UTS) of SP1 and SP2 was increased to 1163 MPa and 932 MPa, respectively, compared with 782 MPa of as-received alloy at 650 °C. Also, the yield stress anomaly (YSA) occurred in SP1 and SP2 because {110}<111> and {112}<111> cross slip systems of B2 phase were difficult to slip at or below room temperature (RT), but they became active at 650 °C and above. As an essential step for increasing the spinnability of multi-pass spinning process of the Ti2AlNb alloy, the H3 heat treatment scheme, i.e. 960 °C/2 h+ 850 °C/12 h, was carried out between two successive passes to increase the hot workability, by which the ductility of the heat treated as-spun workpieces with the microstructure of B2 + primary O + acicular secondary O + high amount spheroidized α2 phases reached 72.1% at 900 °C. After being subject to the H1 heat treatment scheme, i.e. 960 °C-2 h, the spun workpieces with the microstructure of B2 + primary O + intergranular primary α2 phases achieved an optimized comprehensive mechanical properties both at room temperature and 650 °C, which should be chosen as the post-spinning heat treatment process for the service requirement.

Changes in the Properties in Bimodal Mg Alloy Bars Obtained for Various Deformation Patterns in the RSR Rolling Process.

The paper presents the theoretical and experimental research conducted to date regarding the possibility of obtaining round bars from AZ31 magnesium alloy with a bimodal structure rolled in the radial shear rolling process (RSR) technology. There is no analysis of the impact of the deformation path (distribution of deformation in individual passes) on the mechanical properties and the obtained bar structure. The feedstock, namely, AZ31 magnesium alloy round bars with a diameter of 30 mm, were rolled in RSR to the final diameter of 15 mm with different levels of deformation in successive passes, at a temperature of 400 °C. The bars obtained as a result of the RSR rolling process have different hardness on the cross-section as well as a characteristic gradient grain size distribution. Based on the conducted research, it can be concluded that the use of a larger number of passes with a smaller cross-section reduction will result in an improved formation of a bimodal structure consisting of a highly fragmented near-surface structure and in the half of the radius of the structure of fragmented grains at the boundaries of larger grains.

Influence of Friction Stir Process on the Physical, Microstructural, Corrosive, and Electrical Properties of an Al-Mg Alloy Modified with Ti-B Additives.

In this study, two successive methods were used to improve the grain structure and the mechanical and physical properties of Al 5052 aluminum alloy. The modifying elements, 0.99 wt.% of titanium (Ti) and 0.2 wt.% of boron (B), were added during the casting process. After solidification, single- and double-pass friction stir processing (FSP) were performed to achieve additional grain refinement and disperse the newly formed phases well. The addition of Ti–B modifiers significantly improved the mechanical and physical properties of the Al 5052 aluminum alloy. Nevertheless, only a 3% improvement in microhardness was achieved. The ultimate strength (US), yield strength (YS), and elastic modulus were investigated. In addition, the electrical conductivity was reduced by 56% compared to the base alloys. The effects of grain refinement on thermal expansion and corrosion rate were studied; the modified alloy with Ti–B in the as-cast state showed lower dimension stability than the samples treated with the FSP method. The grain refinement significantly affected the corrosion resistance; for example, single and double FSP passes reduced the corrosion rate by 11.4 times and 19.2 times, respectively. The successive FSP passes, resulting in a non-porous structure, increased the bulk density and formed precipitates with high bulk density.

Method for calculating the track depth after successive wheel runs on deformable soil

Wheeled vehicles (tractors, cars, earth-moving machines, trailers, etc.) used in the municipal service are designed to work both on hard and on deformable soil surfaces. When driving on the ground, the power consumption required to ensure the movement of a wheeled vehicle increases sharply. Questions arise related to the cross-country performance of vehicles, their controllability, loads in the transmission. In this regard, it becomes necessary to consider various aspects of the movement of these vehicles on deformable soil, in particular, determining the depth of the track left by the vehicle. This paper presents a method for replacing a deformable wheel with a pneumatic tire with an equivalent wheel of a larger radius, and also considers a method for determining the equivalent radii of the wheels, which makes it possible to determine the track depth with successive passes of pneumatic tires on various deformable soils. The required radii of equivalent wheels can be found by the described method using the results of experiments. The results of calculations using the derived formulas are in good agreement with the experimental data, which indicates the practical applicability of the obtained dependences.