Accurate preform design in forging processes is critical for improving part quality, conserving material, reducing manufacturing costs, and eliminating secondary operations. This paper presents a finite element (FE) simulation-based methodology for preform design aimed at achieving flashless and near-flashless forging. The approach leverages material point backtracking within FE models to generate physics-informed preform geometries that capture complex material flow, die geometry interactions, and thermal gradients. An iterative scheme combining backtracking, surface reconstruction, and point-cloud solid modeling was developed and applied to several three-dimensional forging case studies, including a cross-joint and a three-lobe drive hub. The methodology demonstrated significant reductions in flash formation, particularly in parts that traditionally exhibit severe flash under conventional forging. Beyond supporting the development of new flashless forging sequences, the method also offers a framework for modifying preforms during production to minimize waste and for diagnosing preform defects linked to variability in frictional conditions, die temperatures, or material properties. Future integration of the proposed method with design of experiments (DOE) and surrogate modeling techniques could further enhance its applicability by optimizing preform designs within a localized design space. The findings suggest that this approach provides a practical and powerful tool for advancing both new and existing forging production lines toward higher efficiency and sustainability.

Hydrodynamic cavitation (HC) shows promise for surface modification and strengthening. While previous research has explored its potential for surface hardening and polishing, the application of cavitation for surface texturing remains relatively unexplored. This paper aims to investigate the feasibility of using hydrodynamic cavitation for surface texturing and hardening, as well as identify the key process parameters that influence the outcomes. Computational fluid dynamics (CFD) simulations are utilized to analyze the behavior of cavitation under various conditions, and experimental validation is conducted. The study examines the influence of different chamber insert geometries on cavitation intensity and energy release. It also investigates the effect of process parameters on surface morphology and hardness. The results demonstrate that hydrodynamic cavitation can effectively strengthen specific regions of interest when the cavitation intensity is controlled. However, the formation of surface texture through plastic deformation may be limited to ductile materials or those with low yield strength. The study highlights the significance of utilizing suitable cavitation generators capable of continuously generating cavitation for consistent and controlled intensity. Preliminary results suggest that innovative vortex-based devices have the potential to deliver controlled cavitation intensity to desired areas.

Dual-pressure tube hydroforming (THF) is a tube-forming process that involves applying fluid pressure to a tube’s inner and outer surfaces to achieve deformation. This study investigates the effect of dual-pressure loading paths on material formability and tribological conditions. Specifically, pear-shaped and triangular cross-sectional parts were formed using dual-pressure modes where fluid pressure on the inside of the tubular blank was alternated with pressure on the outside surface of the tubular blank, causing the tube to expand/stretch and contract. During expansion, the tube conformed to the die’s cavity, while during contraction, the contact area between the die and the workpiece reduced, leading to decreased friction stress at the tube–die interface. Additionally, the reversal of pressure loadings caused the tubular blank to buckle, altering the stress state and potentially increasing local shear stress, improving material formability. Dual-pressure THF has demonstrated that the pressure loading paths chosen can substantially influence material formability. Comparing the geometries of parts formed by dual-pressure THF and conventional THF shows a significant increase in the protrusion height of both the pear-shaped and triangular specimens using dual-pressure THF.

Although the full form of the Rayleigh–Plesset (RP) equation more accurately depicts the bubble behavior in a cavitating flow than its reduced form, it finds much less application than the latter in the computational fluid dynamic (CFD) simulation due to its high stiffness. The traditional variable time-step scheme for the full form RP equation is difficult to be integrated with the CFD program since it requires a tiny time step at the singularity point for convergence and this step size may be incompatible with time marching of conservation equations. This paper presents two stable and efficient numerical solution schemes based on the finite difference method and Euler method so that the full-form RP equation can be better accepted by the CFD program. By employing a truncation bubble radius to approximate the minimum bubble size in the collapse stage, the proposed schemes solve for the bubble radius and wall velocity in an explicit way. The proposed solution schemes are more robust for a wide range of ambient pressure profiles than the traditional schemes and avoid excessive refinement on the time step at the singularity point. Since the proposed solution scheme can calculate the effects of the second-order term, liquid viscosity, and surface tension on the bubble evolution, it provides a more accurate estimation of the wall velocity for the vaporization or condensation rate, which is widely used in the cavitation model in the CFD simulation. The legitimacy of the solution schemes is manifested by the agreement between the results from these schemes and established ones from the literature. The proposed solution schemes are more robust in face of a wide range of ambient pressure profiles.

To meet the various and critical manufacturing requirements including high precision, low cost, good manufacturability, and more demanding from product service and performance aspects such as high performance, light-weight, less energy consumption and low carbon emissions in today's era of rapid product development with short product life circle, it is crucial to re-innovate and re-invigorate metal forming technologies and enable it to play an even more important role in manufacturing arena. Historically, introducing new kinds of energy fields into the forming process drives the innovative advance and rejuvenating of forming technologies due to the physically interactive mechanisms of energy field and certain material deformation behaviors such as thermal-mechanical coupling effects. In this paper, a classification of energy-aided metal forming processes is orchestrated and presented, and three kinds of energy-assisted metal forming technologies, viz., electrically-assisted forming, ultrasonic vibration assisted forming, and electromagnetic field supported forming, are reviewed and delineated as they are currently receiving a widespread attention with promising application potentials. In this paper, the physical essence and the effects of these introduced energy fields on deformation behavior, process performance, microstructure evolution are elucidated and analyzed. The constitutive modeling of these forming processes is recapitulated, and the newly established energy field assisted metal forming technologies are exemplified and discussed. Based on the advantages and limitations of these unique metal forming processes assisted by additional energy fields, the process capacity and application potentials are unraveled and examined. Finally, from the aspects of exploring physical mechanisms, establishing high-fidelity models, coupling the multiple energy fields, and developing intelligent equipment and realizing these forming processes, the current challenges and future prospects were discussed, summarized and articulated in such a way to present a panorama of the research, development and application of the energy-assisted forming technologies.

The use of accurate preform dies and billets in forging can improve quality, conserve material, reduce manufacturing costs, and eliminate rehabilitative processes. This paper presents a Finite Element (FE) simulation-based preform die design method that might require a few iterations to find an optimal preform shape. The preforms are iteratively searched by backward tracing of material points in the FE models. The proposed scheme for establishing preform geometries for flash-less forging exploits the ability of FE software packages to track material points at any given process time and location. In this methodology, "flash" is considered a defect—one that can easily be induced by using a slightly larger volume of a preform shape than the exact volume that results is flash-less forging. Since the materials under plastic deformation seek the path of least resistance, other defects are bound to occur. Several case studies on preform designs of 3D forgings are presented. The viability of the methodology is assessed based on strain distribution patterns and forging loads. The methodology was also used on a few example parts which are currently forged with flash. The preform designs with this methodology resulted in a substantial reduction in the flash. Besides aiding in the development of new progression sequences for flash-less die forging, the method could be used to modify preforms in a production line to minimize material waste due to flash. The method can also be used to probe preform shapes that occasionally result in defects caused by variability emanating from interface friction, die temperature fluctuation or other factors.

The printed circuit heat exchanger (PCHE) has small channels with high surface area, making them an efficient solution for next-generation nuclear plants (NGNPs). These PCHEs are fabricated through a diffusion bonding process. This fabrication step changes the microstructure of wrought metal plates. The current ASME design code does not support the PCHE design for NGNPs due to a lack of test data. Hence, there has been initiative towards elevated temperature mechanical property characterization of the diffusion bonded material. One of the most common channel shapes is a semicircular channel with sharp corners. These corners act as a stress riser at the diffusion bonding interface. Evaluating elevated temperature mechanical performance of diffusion bonded material in the presence of stress risers is an essential step towards the ASME code development of PCHE design. This study selected two specimen geometries: the first is a PCHE bar specimen for tensile loading with three rows and three columns of channels, and the second is a lab-scaled PCHE with six rows and eight columns of channels. A set of elevated temperature monotonic and cyclic tests were conducted on the PCHE bar specimen to evaluate the mechanical performance under axial tensile loadings to study the failure mechanism. The lab-scaled PCHE specimens were tested under overpressure loads at room temperature, and pressure creep and pressure creep-fatigue loadings to mimic the realistic loading conditions observed in typical NGNPs. The X-ray scans of channeled specimens show interesting observations. The test results and observations are presented in the paper.

The cavitation peening (CP) and cavitation abrasive jet polishing (CAJP) processes employ a cavitating jet to harden the surface or remove surface irregularities. However, a zero incidence angle between the jet and the surface limits the efficiency of these two processes. This limitation can be improved by introducing a secondary jet. The secondary jet interacts with the main jet, carrying bubbles to the proximity of the workpiece surface and aligning the disordered bubble collapse events. Through characterizing the treated surface of AL6061 in terms of the hardness distribution and surface roughness, it was found out that the secondary jet can increase the hardening intensity by 10%, whereas the material removal rate within a localized region increased by 66%. In addition, employing multiple secondary jets can create a patched pattern of hardness distribution. Another finding is that the hardening effect of the cavitation increases with the processing time at first and is then saturated.

Component failures very often occur due to high temperature and multiaxial stress states arising at critical component locations. To imitate such loading conditions, a multiaxial miniature testing system (MMTS) with axial, torsional, and internal pressurization capabilities for high-temperature testing of miniature tubular specimens has been developed. Among many challenges of developing the MMTS, uniform heating, temperature measurement and control, and surface strain measurement on a miniature tubular specimen at high temperatures have significant difficulties. This paper addresses two significant challenges: first, the development of a non-contact temperature control system using infrared thermography to uniformly heat a miniature specimen of 1 mm outer diameter (OD), and second, the development of a stereo digital image correlation (stereo-DIC) setup for strain measurement on the miniature specimen subjected to high temperature. The developed control system maintains the test temperature through a closed feedback loop and employs a fail-safe mechanism to protect the MMTS load frame components against unanticipated temperature rises. The thermocouple wire-size effect on the measured temperature was examined for three different wire sizes: 0.05, 0.25, and 0.5 mm for accurate emissivity determination required for infrared thermography. Emissivities of the specimen surface at different high temperatures were experimentally determined. Inherent error analysis of the developed high-temperature stereo-DIC setup showed acceptable strain measurement uncertainty. The effectiveness of the developed non-contact temperature control system and high-temperature stereo-DIC setup has been verified by performing tensile testing of a 1 mm OD specimen at 500 °C.

For the advancement of micro- and nano-technologies, multiaxial material testing at a small length scale is imperative. A novel multiaxial miniature testing system (MMTS) is under development for testing a tubular specimen of outer diameter (OD) as small as 1 mm. Because of the small specimen size of MMTS, stereo-Digital Image Correlation (DIC) is the preferred strain measurement technique. Although theoretically, stereo-DIC is length-scale independent, the implementation of stereo-DIC, particularly for miniature testing, faces experimental setup related challenges. For this reason, although stereo-DIC is strongly recommended over 2D DIC, researchers are sometimes compelled to use the latter. It is shown in the present study that the experimental setup related difficulties, particularly for miniature round specimen testing, can be overcome by a systematic development of a mathematical framework for stereo-DIC implementation. This framework addresses all setup decisions concerning stereo-DIC implementation, such as selections of stereo angle, speckle size, camera position, camera sensor size, lens focal length, dimensions of camera and lens bodies, calibration grid size, etc., as well as stereo-DIC analysis parameters, such as subset and step size. Besides serving the need of building a stereo-DIC setup for MMTS, since the developed mathematical framework treats all stereo-DIC setup decisions as variables, it can be used to develop an optimized stereo-DIC setup for any application. Examples of two general cases are reported. Since this general framework serves as a tool to solve the stereo-DIC experimental setup related challenges, the developed framework will contribute to the wider adoption of stereo-DIC over 2D DIC.

A die design architecture for axisymmetric forgings which minimizes the residual contact pressure at the die–workpiece interface during the ejection stroke is proposed. The underlying principle of this die design is that during the forging stroke a tapered die can move in the direction of the forging load thus inducing negative radial elastic strain on the die. When the forging load is removed, the elastic strain energy stored in the die is released thus reposition the die to its initial state. With this design architecture the workpiece can be ejected at no load. Finite element (FE) warm forging simulations for constant velocity joint and pinion gear blank were successfully carried out to evaluate the viability of the process. In addition to reducing residual contact pressure which enhances tribological conditions, the FE simulations conducted have shown that a total energy saving of up to 15% can be achieved with the proposed die designs.

The geometric configuration of a valve-type homogenizer can have a significant influence on the performance of the emulsification process. Three new variants of low-pressure valve-type homogenizers which differ from one another by how the valve nose profiles and the upstream fluid chamber geometries are constructed were used to study fluid flow characteristics. All the three variants were conceived such that hydrodynamic cavitation can be induced as the oil-in-water emulsion passes through the valve. The computational fluid dynamic (CFD) simulations showed that by changing the valve nose shape from smooth profile to serrated nose profile, a substantially higher strain rate in the gap can be achieved, leading to higher stress on the droplet thus increasing the emulsification efficiency. The CFD simulations have also demonstrated that, incorporating a stagnation bluff in the upstream chamber results in a violence collapse of cavitating bubbles. This in turn promotes turbulence inertial and viscous effects which are essential parameters for enhancing emulsification efficiency. Droplet size analysis of oil-in-water emulsions from the physical experiments found that the serrated nose valve profile and the bluff in the chamber resulted in a mean droplet size of about 95 nm.

Forging and extrusion tools are often subjected to a combination of cyclic thermo-mechanical, chemical, and tribological loads. Strategies for minimizing these loads are critical for preventing premature tool failure and increasing productivity. A die design architecture for extrusion that minimizes the residual contact pressure at the die-workpiece interface during the ejection stroke is proposed. The underlying principle of this die design is that during the extrusion stroke, a tapered die can move in the direction of the extrusion load, thus inducing negative radial elastic strain on the die. When the extrusion load is removed, the elastic strain energy stored in the die is released, thus repositioning the die to its initial state. With this design architecture, the workpiece can be ejected at no load. The process was validated using finite element (FE) warm forging/extrusion simulations for a constant velocity (CV) joint and pinion gear shaft. These simulations showed that in addition to reducing residual contact pressure, which enhances tribological conditions, the new die design can easily lower die stresses, thus increasing die fatigue life. The FE simulations for CV joint and pinion gear shaft demonstrated residual pressure in certain locations of the die ranging from 30% to 100% of the pressure induced during the extrusion stroke. The case studies simulated showed that a total energy saving of up to 15% can be achieved with the proposed die setup.

The success of a microtube hydroforming (μTHF) process heavily depends on the material properties of microtubes, which can reveal the material response under multiaxial stress and influence the formability of hydroformed products. However, these material properties are not well understood because of the limited availability of material testing apparatus that would permit control of axial force and internal pressure simultaneously to mimic realistic μTHF loading. The main purpose of this study is to develop a set of grippers that can transfer required testing loads under fully coupled combinations of axial force and internal pressure. The grippers are designed so that they may be kept at the safe working temperature even when tests are carried out at higher temperatures. The grippers are also designed to fit in a load frame that is integrated in a scanning electron microscope for in situ material testing. The capabilities of the grippers are demonstrated by performing uniaxial and multiaxial material tests on SS304 microtubes with 1 mm outside diameter and 0.15 mm nominal tube wall thickness. The finite element simulations and experimental results show that the designed grippers can firmly hold the specimen and thus enable tensile, compression, torsion, and microtube bulge material tests to be accurately performed.

A novel hydrodynamic cavitation–based dispensing process was developed to disperse SiO2 nanoparticles into the base oil, and the effects of process parameters on dispersity and tribological properties of SiO2/oil nanolubricants were studied using the dynamic laser scattering and ring compression tests. With this process, nanolubricants with fine nanoparticles (139–1240 nm) were formulated. A mean particle size reduction of 78% was achieved in 60 min. This process can be scaled up for mass production with relative ease. The formulated SiO2/oil nanolubricants exhibited better tribological performance over that of base oil. Lubrication mechanisms of the SiO2/oil nanolubricant in metal forming were ascertained through analysis of the dispersity of nanolubricants and characterization of dents appearing on the surface of the deforming material. The study revealed the importance of formulating nanolubricants with specific particle size distribution that relate to the surface morphology of the deforming material. In this study, a nanolubricant with particle size of 3.6 μm exhibited better lubrication on ring samples with dent depth of 4.7 μm, implying that most nanoparticles were encapsulated in the dents facilitating hydrostatic lubrication.

Knowledge of deformation and failure mechanisms at micro- to nano-length scales is important for the prediction of material behavior as well as the development of new materials with desired properties. In situ multiaxial testing with scanning electron microscopes (SEM) can reveal physical deformation mechanisms under realistic multiaxial loading conditions. Although in situ SEM testing has gained traction in recent years, there is currently no multiaxial in situ SEM testing stage available with axial-torsional loading capabilities which can generally be used in any SEM. In this study, we report the development of a multiaxial miniature testing system (MMTS) with a unique capability for performing axial-torsional testing of a tubular specimen with a 1-2mm outer diameter, inside most SEMs. The different challenges of developing a multiaxial in situ SEM testing stage, such as small load frame size, appropriate specimen position, high vacuum compatibility of MMTS load frame components, as well as the development of installation accessories, were addressed. A custom SEM stage door was developed for the MMTS load frame. Verification tests have confirmed the successful development of the MMTS for in situ SEM testing. In addition, digital image correlation was used with recorded SEM images during the test to determine the surface strain.

Increasing injection pressure can increase combustion efficiency in direct injection (DI) diesel engines attributing to enhanced atomization. In this paper, a high pressure experimental setup was built to generate ultra-high fuel pressure. An intensification unit was used to magnify the pressure by about 10 times. Preliminary testing of the high pressure system produced a peak pressure of about 8700 bar. Due to the pressure limitation of the commercially available diesel fuel system, the maximum pressure tested in a practical piezoelectric fuel injector was 2500 bar. A high-speed imaging technique was used to visualize the fuel injection events and spray images were taken by a high speed camera for quantitative analysis. A Schlieren technique was used to visualize the shock waves generated during spray penetration. The near nozzle early stage spray development was also studied using a long distance microscope and an intensified charge coupled device (ICCD) camera. Results show that the spray penetration velocity increases with the increase of the injection pressure, while a higher injection pressure leads to a later opening of the piezoelectric injector. The spray angle first has a large value, then remains relatively steady throughout the injection process. Schlieren results clearly demonstrate detached shock waves during the spray penetration. The near nozzle results show that during the very early stage the spray penetration is quite linear for different injection pressures and the spray angle also appears to be very large at the beginning, which is consistent with the high-speed imaging results. Both high-speed imaging and near nozzle results were compared with published empirical equations. The high-speed imaging result shows a good match with the linear stage of empirical equation, while near nozzle result shows lower penetration velocity, indicating that there exists a very short "acceleration stage" for spray development at the starting moment of fuel injection.

Handbook of Manufacturing, pp. 277-382 (2019) No AccessChapter 5: Deformation ProcessesBrad L. Kinsey, Ken-ichiro Mori, and Gracious NgaileBrad L. KinseyDepartment of Mechanical Engineering, University of New Hampshire, 33 Academic Way, Durham, NH, USA, Ken-ichiro MoriDepartment of Mechanical Engineering, Toyohashi University of Technology, Hibarigaoka 1-1, Tempaku-cho, Toyohashi, Japan, and Gracious NgaileDepartment of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh, NC, USAhttps://doi.org/10.1142/9789813271029_0005Cited by:1 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: The following sections are included: Introduction to Deformation Processes Material Behavior during Deformation Rolling Processes Forging Extrusion Processes Flat Sheet Metal Processes Hydroforming Processes Friction and Lubrication in Metal Forming Numerical Simulations for Deformation Processes References FiguresReferencesRelatedDetailsCited By 1Indentation Modulus, Indentation Work and Creep of Metals and Alloys at the Macro-Scale Level: Experimental Insights into the Use of a Primary Vickers Hardness Standard MachineAlessandro Schiavi, Claudio Origlia, Alessandro Germak, Andrea Prato and Gianfranco Genta28 May 2021 | Materials, Vol. 14, No. 11 Handbook of ManufacturingMetrics History PDF download