Rafael Menezes Nunes

Analysis by design of experiments of distortion potentials in drawn and induction hardened wire

In this investigation a DoE (Design of Experiments) analysis of distortion for a typical manufacturing process of pre-straightened, cold drawn and induction hardened AISI 1045 cylindrical steel bars was carried out. A careful characterization of the material, including residual stress states and geometrical changes, was done for the different manufacturing steps. In order to identify effects and correlations on distortion behavior, the investigated variables included the drawing process itself with two different drawing angles, a stress relief treatment, which was applied to one part of the samples, and, finally, induction hardening with two different case depths. Main and statistically significant effects on the distortion of the induction hardened samples were found to be in this order, the drawing angle, the stress relief treatment and the induction hardening depth. It was also found that the distortion potentials are transmitted from the drawing process to further manufacturing steps and, consequently, from one production site to the next.

Experimental characterization and simulation of a wire drawing process and related distortion potentials

Abstract In this investigation a DoE (Design of Experiments) analysis of distortion for a typical manufacturing process of pre-straightened, cold drawn and induction hardened AISI 1045 cylindrical steel bars was carried out. A careful characterization of the material, including residual stresses and geometrical changes was done for the different manufacturing steps. The variables included the drawing process itself with two different drawing angles, a stress relief treatment which was applied to one part of the samples and finally an induction heat treatment with two different case depths applied to identify effects and correlations on distortion. Simulation of the drawing process was also used as tool to clarify possibilities and limits of this kind of analysis, depending on the available input data. Different influences on the distortion of the induction hardened samples were found and discussed, as for example the marked dependence of the distortion on drawing angle.

Comparação entre difração de raios X e "método do furo cego" para medição de tensões residuais em barras cilíndricas

The residual stresses in the surface and subsurface of mechanical components during the manufacturing process can affect the behavior and represent a significant potential for deviations in shape and size. These residual stresses also represent one of the main potentials for the distortion (which are bending and dimensional changes) in mechanical components during the manufacture. Therefore, the determination of the distribution and the control of these residual stresses in each stage of the manufacturing process is of great importance. In this work, analysis of the variation of the residual stresses were accomplished in cold-drawed bars of AISI 1045 steel due to the manufacturing process. The bars were analyzed by X-ray diffraction (XRD) and hole-drilling (H.D) to characterize the residual stresses. Starting from the values of strains obtained, the longitudinal residual stresses were calculated for each tested point. With this work, a detailed view of the development of stress in the surface to a depth of 1mm of bars after the process steps was obtained.

Investigation of the Influence Factors on Distortion in Induction-Hardened Steel Shafts Manufactured from Cold-Drawn Rod

In this study, the distortion of steel shafts was investigated before and after induction hardening. Several essential influencing factors in the manufacturing process chain regarding cold drawing, cutting method, notches on the shafts, and induction hardening were analyzed by design of experiment (DoE). Further necessary examinations of microstructures, hardness profile, segregation of chemical composition, and residual stress state were conducted for understanding the distortion behavior. The results of the statistical analysis of the DoE showed that the drawing process is the most important factor influencing distortion. The surface hardening depth of induction hardening is the second main factor. The relationship between inhomogeneities in the work pieces and the distortion was finally discussed.

Distortion Analysis in the Manufacturing of Cold-Drawn and Induction-Hardened Components

In this investigation, a design of experiments analysis of distortion for a typical manufacturing process involving pre-straightening, cold drawing, and induction hardening of AISI 1045 cylindrical steel bars was carried out. A careful characterization of the material, including residual stress states and geometrical changes, was done for the different manufacturing steps. In order to identify effects and correlations on distortion behavior, the investigated variables included the batch influence, the combined drawing process itself with two different drawing angles and two different polishing and straightening (P.S.) angles, a stress relief treatment which was applied to a part of the samples, and finally induction hardening with two different surface hardening depths. Main and statistically significant effects on the distortion of the induction-hardened samples were found to be in this order: first, the interaction between the drawing angle and batch, then the interaction between drawing angles, and finally drawing angle and induction hardened layer. It was also found that the distortion potentials are transmitted from the drawing process to further manufacturing steps and, consequently, from one production site to the next.

Residual stress analysis of drive shafts after induction hardening

Typically, for automotive shafts, shape distortion manifests itself in most cases after the induction hardening by an effect known as bending. The distortion results in a boost of costs, especially due to machining parts in the hardened state to fabricate its final tolerances. In the present study, residual stress measurements were carried out on automotive drive shafts made of DIN 38B3 steel. The samples were selected in consequence of their different distortion properties by an industrial manufacturing line. One tested shaft was straightened, because of the considerable dimensional variation and the other one not. Firstly, the residual stress measurements were carried out by using a portable difractometer, in order to avoid cutting the shafts and evaluate the original state of the stresses, and afterwards a more detailed analysis was realized by a conventional stationary diffractometer. The obtained results presented an overview of the surface residual stress profiles after induction hardening and displayed the influence of the straightening process on the redistribution of residual stresses. They also indicated that the effects of the straightening in the residual stresses cannot be neglected.

Zerstörungsfreie Eigenspannungsanalyse von Stahlwellen nach unterschiedlichen Prozessschritten vom Drahtziehen zum Induktionshärten

Kurzfassung Eine Prozesskette für die Herstellung von Maschinenbauteilen besteht im Allgemeinen aus mehreren Prozessschritten, wie z. B. Stranggießen, Warmwalzen, Glühen, Richten, Drahtziehen, Richten und Polieren, spanende Bearbeitung, Induktionshärten und Schleifen. Verzug wird häufig nach der finalen Wärmebehandlung beobachtet. Verantwortlich dafür ist nicht nur das Härten, sondern auch die Vorgeschichte der Prozesskette. In der vorliegenden Arbeit wurden einige wesentliche Schritte einer Prozesskette experimentell untersucht und die Eigenspannungsverteilungen als wesentliche Verzugspotenzialträger mit Neutronenstrahlung über den gesamten Querschnitt der Zylinder zerstörungsfrei analysiert. Die Ergebnisse zeigen, dass nach dem Richten der entrollten Drähte unsymmetrische Eigenspannungsverteilungen über den Querschnitt vorliegen. Das Kaltdrahtziehen führt zu hohen Zugeigenspannungen an der Oberfläche in radialer und tangentialer Richtung, während im Kern vor allem Druckeigenspannungen in axialer Richtung vorliegen. Der anschließende Schritt – Schrägwalzen-Richten (SWR) – führt zu einer Reduktion der Eigenspannungen. Das finale induktive Härten verändert die Eigenspannungszustände in Abhängigkeit der Prozessbedingungen wieder sehr stark. Die Einflüsse der untersuchten Prozessschritte auf die Eigenspannungszustände werden schließlich in Verbindung mit den auftretenden Verzügen diskutiert.

Comparison between Neutron Diffraction measurements and numerical simulation of residual stresses of a Wire-Drawing process

In this work, a drawing processed was simulated to calculate forces and the resulting residual stresses in the material. The calculated residual stresses were compared with experimentally measured residual stresses by the Neutron Diffraction Method. The modeled process was the Wire Drawing. The necessary parameters to model the process were taken from an industrial currently used process. Rods of an AISI 1045 steel with nominal diameters of 21.46 mm were reduced to 20.25 mm by drawing with an drawing angle of 15°. Compression tests were used to determinate flow curves of the real material an used in the simulation models. The possibility to estimate drawing forces by numerical simulation was evaluated by comparing simulated results with values from empirical equations given by the literature. The results have shown a sufficient accuracy for the calculation of forces, but the comparison of residual stresses has shown differences to the experimentally determined ones that can be minimized by the consideration of high strain rates in the compression tests, anisotropy of the material and kinematic hardening.

Residual stress and microstructural features of friction-stir-welded GL E36 shipbuilding steel

ABSTRACT The purpose of the present study was to fulfil the knowledge gap concerning residual stresses evaluation of friction stir welded GL E36 shipbuilding steel. Plates of 6 mm thickness were welded using two different welding speeds (1 and 3 mm s−1) at a constant rotational speed of 500 rev min−1. This led to different thermal cycles and the objective is to analyse the resulting microstructures and residual stress states. Therefore, in this work, residual stresses were evaluated by X-ray diffraction; metallography and microhardness testing were performed to support these measurements. Results showed that welds produced with different heat inputs have distinguishable residual stress distributions. Increases in the welding speed led to higher residual stress and microhardness in the stir zone.

Evaluation of the Residual Stress State of 42crmo4 Steel Sheets in a Production Line

The residual stress state of a mechanical component is an important factor in its production planning and in estimates of its lifecycle since it can be responsible for geometric distortions and degradation of fatigue properties. Therefore, the development of reliable methods for non-destructively quantifying these stresses remains in the interest of most manufacturing industries; Barkhausen magnetic noise measurements have been investigated in several applications and remains a viable option. However, its effective implementation has occurred mostly in components with simple geometries and insignificant microstructural gradients; even in these cases, successful industrial adoption of the method depends on previous calibration with samples that are often difficult and costly to prepare and validate. This work aims at investigating the capability of the method of characterizing the residual stress state in a simple but generally useful application: samples of hot-rolled steel sheets collected at two different stages of processing in an industrial mechanical conformation and heat treatment plant. In this analysis Barkhausen noise measurements were compared to X-ray diffraction results, and statistical analysis tools were used to correlate the results.