This paper describes the phenomena taking place on the surface of the dies used for hot forging. Because of this paper’s limited space only changes in the tool surface layer during the forging of a gear wheel, as most representative, are presented. Similar changes were observed in the case of the other two investigated closed die forging processes, i.e. the forging of a cover and a yoke, respectively. The research was aided by FEM, which supplied a lot of information about the forging conditions. The most intensive wear of the tools occurs in the place of their longest contact with the material being forged, regardless of the number of produced forgings. The research has shown that the one of the most adversely factor affecting the investigated forging process is thermomechanical fatigue which results in fine cracks quickly developing into a network of cracks extending over the entire tool/forged material contact surface. Also the abrasive wear of the investigated die is high due to the intensive flow of the material in the presence of abrasive oxide particles and tools bits created by thermomechanical fatigue. An attempt to model the abrasive wear using the Archard model is presented.

The failure mechanisms of hot forging dies

Analysis of forging defects for selected industrial die forging processes

A new method for manufacturing hollow valves via cross wedge rolling and forging: Numerical analysis and experiment validation

A change in the technical condition of mechanical components of internal combustion engines may not be detected by on-board diagnostic systems installed in vehicles. In similar cases, measurements and analyses of vibroacoustic signals being recorded prove useful. Since there are certain limitations to vibration measurements, including those related to the vibration transmission and the engine’s high temperature at measurement points, the authors of this paper have proposed that measurements and analyses of acoustic signals should be applied for the sake of assessment of the internal combustion engine technical condition. However, such an assessment requires new acoustic signal processing methods to be developed, and so this subject has been elaborated in the paper. The article provides a discussion on the option of applying a wavelet packet decomposition while filtering the internal combustion engine’s acoustic signal in order to diagnose an excessive valve clearance. The authors prepared an algorithm enabling selection of the chosen details and approximation of the wavelet analysis to low-frequency components, which constitute the noise, as well as high-frequency components comprising information on the possible enlarged engine valve clearance. Next, based on the selected high-frequency acoustic signal components, a method for automatic detection of enlarged clearance valves was developed, assuming that energy participations of the acoustic signal being emitted were to be determined while opening and closing individual valves. Under the study discussed, identification tests were conducted using two 4-cylinder internal combustion engines featuring valves of different clearances to consequently confirm the efficiency of the algorithm developed for the acoustic signal filtration and automatic detection of enlarged clearance valves.

Condition monitoring of engine timing system by using wavelet packet decomposition of a acoustic signal

Sheet metal forming (SMF) is one of the most popular technologies for obtaining finished products in almost every sector of industrial production, especially in the aircraft, automotive, food and home appliance industries. Parallel to the development of new forming techniques, numerical and empirical approaches are being developed to improve existing and develop new methods of sheet metal forming. Many innovative numerical algorithms, experimental methods and theoretical contributions have recently been proposed for SMF by researchers and business research centers. These methods are mainly focused on the improvement of the formability of materials, production of complex-shaped parts with good surface quality, speeding up of the production cycle, reduction in the number of operations and the environmental performance of manufacturing. This study is intended to summarize recent development trends in both the numerical and experimental fields of conventional deep-drawing, spinning, flexible-die forming, electromagnetic forming and computer-controlled forming methods like incremental sheet forming. The review is limited to the considerable changes that have occurred in the SMF sector in the last decade, with special attention given to the 2015–2020 period. The progress observed in the last decade in the area of SMF mainly concerns the development nonconventional methods of forming difficult-to-form lightweight materials for automotive and aircraft applications. In evaluating the ecological convenience of SMF processes, the tribological aspects have also become the subject of great attention.

/pdf/recent-developments-and-trends-in-sheet-metal-forming-29um1mszus.pdf

Recent Developments and Trends in Sheet Metal Forming

Recent development trends in metal forming

The study presents the effect of annealing process parameters on the microstructure, hardness, and strain-hardening coefficients, that is, the strength coefficient c and the strain-hardening exponent n, of 42CrMo4 steel. Seven selected annealing time–temperature schemes are examined for superior steel formability in cold metal forming conditions. The c and n coefficients are first determined in experimental upsetting of annealed samples and then used in FEM (finite element method) simulations of the upsetting process. The results demonstrate that the strain-hardening coefficients (c and n) depend on the employed annealing scheme. Compared with the as-received sample, the annealing process reduces the true stress and effectively decrease the hardness of 42CrMo4 steel; improves microstructural spheroidization; and, consequently, facilitates deformability of this material. The annealing schemes, relying on heating the material to 750 °C and its subsequent slow cooling, lead to the highest decrease in hardness ranging from 162 to 168 HV. The results obtained with the SEM-EDS (scanning electron microscopy-energy dispersive spectrometer), LOM (light optical microscopy), and XRD (X-ray diffraction) methods lead to the conclusion that the employed heat treatment schemes cause the initial ferritic-pearlitic microstructure to develop granular and semi-lamellar precipitation of cementite enriched with Mo and Cr in the ferrite matrix. In addition, the annealing process affects the growth of α-Fe grains. The highest cold hardening rate, and thus formability, is obtained for the annealing scheme producing the lowest hardness. The results of FEM simulations are positively validated by experimental results. The obtained results are crucial for further numerical simulations and experimental research connected with developing new cold metal forming methods for producing parts made of 42CrMo4 steel.

https://www.mdpi.com/1996-1944/13/9/2022/pdf

Effect of Annealing Time and Temperature Parameters on the Microstructure, Hardness, and Strain-Hardening Coefficients of 42CrMo4 Steel.

Numerical and Experimental Study of Producing Flanges on Hollow Parts by Extrusion with a Movable Sleeve

Flange formation in aluminium alloy EN AW 6060 tubes by radial extrusion with the use of a limit ring

This paper presents the results of a numerical analysis of a cold forging process for a hollow flanged part. The analysis was performed using Deform 2D/3D. 42CrMo4 steel tubes were used as the billet material, and their material model in the annealed state was described by a constitutive equation. The forming process was performed in six stages with the use of methods such as extrusion with a movable sleeve, open-die extrusion, and upsetting. The objective of the study was to determine whether the proposed forging technique could be used to produce hollow parts with flanges. The determination was made based on the analysis of product geometry quality and process parameters, including the Cockcroft-Latham ductile fracture criterion and forming forces.

/pdf/numerical-analysis-of-a-six-stage-forging-process-for-rhgsiruyit.pdf

Grzegorz Winiarski

Papers

Recent development trends in metal forming

Effect of Annealing Time and Temperature Parameters on the Microstructure, Hardness, and Strain-Hardening Coefficients of 42CrMo4 Steel.

Numerical and Experimental Study of Producing Flanges on Hollow Parts by Extrusion with a Movable Sleeve

Flange formation in aluminium alloy EN AW 6060 tubes by radial extrusion with the use of a limit ring

Numerical Analysis of a Six Stage Forging Process for Producing Hollow Flanged Parts from Tubular Blanks