This study aims to explore the influence of distinct forging parameters on microstructure and mechanical properties of TC21 forgings. The trimodal microstructure, which includes equiaxial α (αeq), ...lath α (αlath), and fine α (αfine) phases, was achieved via quasi-β forging and dual heat treatment. Subsequently, mechanical properties were evaluated through tensile, impact toughness (ak), and fracture toughness (KIC) tests. Results indicate that the content of αeq is higher at lower forging heating temperature, whereas the content of αlath is diminished and the size of αfine remains relatively small. This tendency reverses at higher forging heating temperature due to the increased driving force of the phase transition. The rise in αlath content implies more pronounced interface strengthening and plastic deformation, which significantly contributes to strength compared to αfine and αeq but exerts a weaker influence on plasticity. Moreover, the combined deformation and fracture of αlath and αfine exert a significant influence on the initiation and propagation of cracks in ak and KIC specimens. The limited coordination of deformations exhibited by αlath leads to preferential stacking dislocations and shear fractures at interfaces, which are further influenced by its higher aspect ratio affecting crack propagation paths. This not only increases the required energy for initiating cracks but also raises energy consumption during their propagation. Crucially, the presence of αfine significantly enhances the dislocation accumulation and the plastic deformation zone at the crack tip, thereby playing a pivotal role in determining local deformation capacity and crack deflection frequency.
Forgings are produced in several process steps, the so-called forging sequence. The design of efficient forging sequences is a very complex and iterative development process. In order to automate ...this process and to reduce the development time, a method is presented here, which automatically generates multi-stage forging sequences for different forging geometries on the basis of the component geometry (STL file). The method was developed for closed die forging. The individual modules of this forging sequence design method (FSD method) as well as the functioning of the algorithm for the generation of the intermediate forms are presented. The method is applied to different forgings with different geometrical characteristics. The generated forging sequences are checked with FE simulations for the quality criteria form filling and freedom from folds. The simulation results show that the developed FSD method provides good approximate solutions for an initial design of forging sequences for closed die forging in a short time.
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•An useful method to allow fast control of the stability of the forging process.•An original method for reliable wear analysis of forging tools and forging defects.•A practical ...solution not require interruption of production process.•Research in area of scanner applications and validation in industrial process.
This article refers to the application of the 3D reverse scanning method for the purpose of analyzing the progressing wear of forging tools as well as detecting forging defects in selected hot die forging processes. By using the POLYWORKS software, the authors developed a numerical algorithm making it possible to determine the volume changes in selected areas of forgings periodically collected from the forging process, in comparison to a reference model. As a consequence of this, two parameters are determined: the positive volume – defining tool wear, and the negative volume – indicating a forging defect, e.g. underfill. Both of these parameters (positive and negative volume) are independent of one another. They can be used to determine the following characteristics: the tool wear curve and the curve indicating the possibility of a defect in forgings as well as disruptions of the production process. The presented approach may be a useful and effective tool which allows a quick assessment of the current tool status and forging quality (without the need for a significant interference in the production process). It may also serve as an instrument for the analysis of the stability and correctness of the production process.
In mandrel forging, anvil shape and process parameters affect the quality of large cylindrical forgings. In this paper, five different anvil shapes are introduced involving a long flat anvil, a short ...flat anvil, a double-sided bevel anvil, a single-sided bevel anvil, and a short-shaped anvil. The effects of process parameters are studied including tool speed, reduction, mandrel rotation angle, feed rate, and forging sequence. The research is carried out by a combination of numerical simulations and experiments to find out reasonable process parameters that can obtain high-quality large cylindrical forgings. The results show that the use of a long flat anvil is the most efficient, but the core of the ingot may be insufficiently forged, the forming force is uneven and the required forming force is the largest; the efficiency of using a short flat anvil is the lowest, but it can improve the quality of the forgings compared to using a long flat anvil; using a short-shaped anvil is relatively efficient, and the forged ingot is best and the forging force is relatively lower. Especially, when the short-shaped anvil works under unequal feed rates with a forging sequence from both ends to middle, it can obtain high-quality forgings and the forming force is uniform and lowest. The research has certain guidance and contribution to the mandrel forging of large cylindrical forgings.
The work concerns the application of non-contact measurement 3D scanning techniques in conjunction with a study of the microstructure of a forging die (made of W360 steel) for the production of an ...engine valve (made of NCF 3015 steel) in a hot die forging process in order to analyse the changes in the working surface of the tools and identify the destructive mechanisms. The detailed analysis presented in this paper examines the possibility of using 3D reverse engineering techniques for a direct quality control and examination of the changes in the surface layer geometry of the forging dies, based on the measurement of the geometry changes for cyclically collected forgings. The selected area of the valve forgings cyclically retrieved from the forging process was scanned with the use of an intermediate scanning method - reverse 3D scanning. On this basis, an analysis of the progressive material growth on the selected surface of the forgings was made, which also meant a loss of material on the tools. The performed analyses showed a good agreement of the geometrical properties of the surfaces (of the selected forgings representing the proceeding wear of the tool) and the geometrical defect of the working impression of the tool, based on the direct measurements during the production process. The reverse 3D scanning method developed by the authors has been repeatedly verified by them, which is confirmed by numerous studies and applications. The obtained results combined with SEM analyses and microhardness measurements enable a fast analysis of the forging tool life with respect to the quality and quantity (of material defect), which, in consequence, leads to significant economical savings.
•Measurement of tool wear on the basis of the use reverse method of scanning 3D.•Identification of the destructive mechanisms and phenomena in different areas of die.•Use the combine results of SEM and microhardness measurements as well as FE modelling for a more complete analysis.•Practical knowledge for forging-engineers about the improvement of durability forging tools.
Material fracture is a serious problem in cross wedge rolling (CWR). Finding new solutions for material fracture prevention in CWR processes presents a technological challenge for researchers these ...days. This paper presents a new approach to the problem of material fracture, which investigates a not previously undertaken aspect concerning the influence of the cross wedge rolling method on the development of internal cracks. CWR rolling methods in which two tools are used (two flat wedges, two roll wedges, roll wedge-concave segment, two concave wedges) were analysed. In addition, the effect of the number of moving tools on material fracture in CWR is investigated. Material fracture is predicted by a novel hybrid fracture criterion. In this paper, FE simulations were used to determine the value of the hybrid fracture criterion. Experimental studies were used to validate the built numerical model. The conducted research has shown that with the increase in the ovalization of the cross-section of the rolled forging, which depends on the rolling method and the number of moving tools, the degree of damage to the forging increases. The highest degree of damage occurs during the flat wedge rolling method, in which only one wedge is moving. The lowest degree of damage occurs when rolling with two moving concave wedges. The most important conclusion of the study is that changing the rolling scheme from the least favourable to the most favourable one allows to reduce the degree of forgings damage twice.
The article presents the results of a complex analysis referring to a periodical occurrence of forging defects in the form of twisting of pin-type elements (perpendicular to the main forging axis) as ...well as lack of total filling of these areas on the forgings in the process of hot precision forging on a hammer. The studies included: an analysis of the forging technology, advanced numerical simulations of the process and dynamic tests of the mutual shifting of the tools with the use of a high-speed measurement camera. The hot precision forging process was realized on a double operation hydraulic hammer with the maximal energy of 16 kJ, as a result of which, a so-called leaf is formed in the dies in two operations, which has 6 relatively small forgings (the mass of one is about 40 g), characterizing in a narrowed scope of dimension-shape tolerance (0.1–0.2 mm and 0.5–1°). The performed preliminary process analysis showed that, for this type of forgings made in a dynamic manner on a hammer, the key role is played by elastic deformations as well as the construction of the dies (application of guide locks) and the impression geometry. Additionally, during the forging process, in the case of pin-type elements (shape of a truncated cone with the convergence of 1°), their twisting was observed as well as small underfills caused by “closed volumes”, connected with the non-vaporized lubricant and the formation of air pockets. The mentioned problems relating to this process significantly affect the quality and precision of the forgings and cause defects. For this reason, based on the results of the conducted tests and analyses, a different approach to the design of dies was applied than in standard hammer forging technologies. It was introduced the necessary changes in the technology as well as modify the construction and geometry of the tools (in the lower die a negative slope was applied) in order to eliminate joggle and twisting of the forging elements, which disqualify such items.
•Problems with defects - unfilling and warping of precision forgings•High deformation rates during forging on a hydraulic hammer•Elastic deformation of dies and rapid cooling of forgings (thermal skinning)•Using of CMM and 3d scanning as well as numerical modelling and dynamic measurements•Changes in the tools construction (stiffening of the system) and geometry of patterns (die bevels at 0°)
•A new section line extraction method of ring forgings is proposed.•An optimization algorithm based on normal vector and L1-median is established.•The optimization algorithm is immune to noise and ...can preserve details.•The optimization algorithm is suitable for a variety of point cloud models.
Ring forgings are widely used in industrial fields. It is an important way that the key dimensions of ring forgings are obtained by laser scanning to ensure the processing quality. It is difficult to extract high-precision section line of ring forgings from laser point clouds with a lot of noise. This paper presents a new method for extracting section line from raw point cloud of ring forging. An optimization algorithm is created based on the normal vector and L1-median, which is used to iteratively shrink the sampling points for obtaining the section line of ring forgings. L1-median has the characteristics of noise immunity, adding normal vector can get more detailed features. The extraction of high-precision section line of ring forgings is realized. Taking the second-order ring forging and the third-order ring forging as the experimental object, experiments are carried out to verify the effectiveness of the model.
•A new method of processing laser scanning data for ring forgings is proposed.•The information space sets of laser scanning data are established.•The uniform continuity between the various areas of ...information space is verified.•The undetermined coefficients are solved by gradient descent and uniform isomorphism factor.
Ring forgings are widely used in petrochemical, power generation, aerospace, nuclear industry and other industrial fields. In the forging process, the radial section size data greatly affect the forging accuracy of ring forgings. Therefore, a new method of processing laser scanning data of radial section dimensions for ring forgings is proposed. Firstly, the information space set of laser scanning data is established. This information space is divided by continuous concentric circles. Secondly, according to the information relationship between the various areas in the information space, the uniform isomorphism factor is defined. By combining the gradient descent method with the uniform isomorphic factor, the undetermined coefficients are solved. Thirdly, the reduction ratio is set according to the density of scanning data points. By combining the reduction ratio with the undetermined coefficients, the number of points needed to be reserved in each area of a concentric circle is determined. The remaining points and the repetitive points in the intersection of two concentric circles are deleted. Finally, the method is repeated until the last point of the laser scanning data. In this way, the laser scanning data of radial section for ring forging is processed. When the method is applied in the experiment, the size data of radial section is extracted from the processing data of laser scanning radial section line. Two groups of dimension data measurement experiment for standard and non-standard ring forgings are carried out respectively. The dimensions measured from the unprocessed and processed data points are compared with true values. The dimensions measured from the processed data have higher accuracy and smaller error. The feasibility of this method is proved.
The boundary dimension of ring forgings is an important factor to ensure the machining quality. However, point cloud models of ring forgings obtained by three-dimensional laser scanner have a large ...amount of data and many redundant points, resulting in dimensional errors in the simplification processing of three-dimensional point cloud models of ring forgings. Therefore, this paper proposes an improved point cloud data simplification method of single median error metric based on firefly algorithm. Firstly, the point cloud data are preliminarily simplified by the improved farthest sampling method to improve the efficiency of the subsequent simplification process. Secondly, the triangle collapse algorithm is improved by using the proposed single median error metric. The single median error of the triangle is regarded as the objective function by the firefly algorithm, and the optimal solution of the single median error function is solved by using the mutual attraction relationship between fireflies. Finally, through the simplification experiment of the point cloud model of ring forging, it is verified that the algorithm can reduce the amount of point cloud data of annular forging and the dimensional error between the forging and the original model. The simplification method proposed is feasible according to the experimental results.
