Papers by Keyword: Deep Rolling

Abstract: This paper analyzes the possibility to induce residual compressive stresses utilizing deep rolling in a long, slim steel workpiece that is profile ground and that resembles a linear guide rail. These intentionally caused residual compressive stresses at the side surfaces of the workpiece are intended to counteract the distortion due to residual stresses in the V-groove of the guide rail induced by grinding. A finite element model was prepared based on the initial state of the workpiece. The amount of respective stresses depended on the load intensity and duration of the process. The experimental data regarding the residual stress profiles due to the deep rolling process and the resulting workpiece distortion were used to validate the simulation, so that an adjustment or a calibration of the thermometallurgical and thermomechanical material data was possible. The key findings are the numerical design of appropriate strategies for the distortion potential induction, the experimental distortion results, knowledge on the mechanical treatment by deep rolling, and the successful modeling of the mechanical treatment and the process strategy.

Abstract: Because of the general problem of the welding workpiece such as fatigue fracture caused by tensile residual stress lead to initial and propagation crack in the fusion zone. Thus, the mechanical surface treatment of deep rolling on Gas Tungsten Arc Welded (GTAW) surfaces of AISI 316L was studied. Deep rolling (DR) is a cold working process to induce compressive residual stress in the surface layer of the workpiece resulting in hardening deformation which increased surface hardness, and smooth surface that inhibit crack growth and improve fracture strength of materials. The present study focuses on compressive residual stress at the surface of stainless steel AISI 316L butt welded joint of GTAW. The three parameters of DR process were used; pressure 150 bar, rolling speed 400 mm/min, and step over 1.0 mm. The residual stresses analysis by X-ray diffraction with sin²Ψ method at 0, 5, 10, and 20 mm from the center of the welded bead. The results showed that the DR process on the welded of GTAW induce the minimum compressive residual stress-408.6 MPa and maximum-498.1 MPa in longitudinal direction. The results of transverse residual stress in minimum and maximum are 43.7 MPa and-34.8 MPa respectively. The FWHM of DR both longitudinal and transverse direction were increased in the same trend. Furthermore, the microhardness after DR treatment on workpiece surface layer higher than GTAW average 0.4 times.

Abstract: The aim of the present work was the assessment of the impact of deep-rolling and shot-peening performed in the underhead and in the unthreaded shank of two high strength screws (36 NiCrMo and 42 CrMoV) for fatigue life enhancement. The experimental campaign consisted of six combinations, including the non-treated state. The aforementioned treatments were evaluated alone or with shot-peening performed after deep-rolling in the underhead fillet of the screws. Deep rolling was carried out at the optimal rolling force, whereas two shot diameters were considered for shot-peening (Z100 and UFS70). The results have been evaluated in terms of fatigue limits and factor effects have been assessed by marginal mean plots.

Abstract: Metal Inert Gas (MIG) welding process is a common welding process for carbon steels. During the cooling after welding, non-uniform cooling cause tensile residual stress on the surface of welded joint and, in most cases, in Heat Affected Zone (HAZ) also. The tensile residual stress is undesirable because it affects the strength and shorten the workpiece fatigue life. In order to convert the tensile residual stresses to desirable compressive residual stresses, the mechanical surface treatment like deep rolling process was used in this research. The surface residual stresses were measured by XRD machine with the sin2ψ method. For statistical analysis of significant factors used in deep rolling process, there are three factors each factor has two levels: rolling pressure, rolling speed and number of passes. Taguchi experimental design was used in conjunction with a deep rolling process to determine factors affected the surface residual stresses and surface microhardness. The results of the research showed that the most significant factors that affect the surface residual stress and surface microhardness were the number of passes, followed by the rolling pressure and the rolling speed, respectively. The maximum compressive residual stress measured at the welded joint was -521.5 MPa. The highest measured surface microhardness was 266.2 HV at the welded joint. The appropriated factors of deep rolling process for JIS SS400 MIG welding were rolling pressure 270 MPa, rolling speed 1,500 mm/min and number of passes 3 times.

Abstract: Friction stir welding is most commonly used for joining aluminum alloy parts. After welding, residual stresses occurred in the welded joint caused by non-uniform cooling rate. Friction stir welding usually generates tensile residual stress inside the workpiece which affects the strength in addition to the fatigue life of materials. Compressive residual stress usually is beneficial and it can be introduced by mechanical surface treatment methods such as deep rolling, shot peening, laser shock peening, etc. In this research, deep rolling was used for inducing compressive residual stress on surface of friction stir welded joint. The residual stresses values were obtained from X-ray diffraction machine. Influence of three deep rolling process parameters: rolling pressure, rolling speed and rolling offset on surface residual stresses at the welded joint were investigated. Each factor had 2 levels (2³ full factorial design). The statistical analysis result showed that the rolling pressure, rolling speed, rolling offset, interaction between rolling pressure and rolling speed, interaction between rolling speed and rolling offset were statistically significant factors, with the most compressive residual stress value approximately -391.6 MPa. The appropriated deep rolling process parameters on surface residual stress of AA7075-T651 aluminum alloy friction stir welded joint were 1) rolling pressure about 150 bar 2) rolling speed about 1,400 mm/min 3) rolling offset about 0.1 mm.

Abstract: Deep rolling is an established mechanical surface treatment technology based on local plastic deformation of the surface layer. By these means, residual stresses, and strain hardening are induced into the surface layer as well as its surface structure is smoothed. Vibrorolling is a derivate technology of deep rolling characterized by sinusoidal rolling lanes. Due to process kinematics of vibrorolling the surface layer is incrementally deformed multiple times in different directions. As a result, a more intensive plastic deformation of the surface layer is achieved and potentially tribologically active surface structures are produced. To investigate and compare the effects of both surface treatment technologies on the tribological behavior of a processed component, a friction and wear analysis under lubricated conditions was conducted in this work. Friction and wear behavior of untreated, deep rolled, and vibrorolled specimens using a pin-on-cylinder tribometer was conducted. Hardness, roughness, and geometrical measurements of the wear traces were used to characterize the specimens. Additionally, qualitative assessments of the wear traces using scanning electron microscopy imaging were made. The measurements were performed before, during, and after the friction and wear analysis. Furthermore, contact forces between a tribometer pin and the workpiece were determined to analyze the development of contact shear stresses. Based on the conducted investigations, the effects of deep rolling and vibrorolling on the friction and wear behavior of the treated specimens are discussed and explanations for the observed phenomena are formulated in this work.

Abstract: For better mechanical properties and lifetime of sintered products, it is suggested that an improvement can be made by a combination of mechanical-and chemical-surface treatments. In this study, the effect of deep-rolling on surface properties and microstructure is investigated. It is found that both compactness and hardness is improved by deep-rolling process where high force is applied. The outer surface hardness can be doubled when the deep-rolling is applied prior to carburizing. Nonetheless, a reduction in the thickness of the martensite-transformed layer due to an increment of applied force is observed.

Abstract: Deep rolling process is a mechanical surface treatment that provides several advantages, such as low friction on the interface between the tool and workpiece in the process, controlled profile of induced compressive residual stress to enhance the HCF and LCF strength, enhancement of the stability of the near-surface structure at high temperature, and improvement of surface finish after the process. This paper investigates the deep rolling process under lubricated condition for a complex deep rolling path. A three-dimensional finite element model incorporating the strain hardening and strain rate effects on the material responses is developed to sequentially simulate the continuous multi-axis roller motion in the process. This model can capture the horizontal and normal forces acting on the roller so that a time-varying apparent coefficient of friction can be obtained. In addition, due to the complex roller path, the model also predicts a complex residual stress distribution in the near-surface material.

Abstract: The life time of roller bearings can be increased by inducing compressive residual stresses in the subsurface region of the raceway. These stresses can be induced by overloading in the first numbers of revolution. It would be much more useful to create the surface integrity within the manufacturing process. In this paper a method is presented to improve the process chain from grinding and honing to hard turning and deep rolling. As a result the surface finish is comparable to ground bearings. Due to the deep rolling process the maximum compressive stresses can be induced to higher values and depth. For the evaluation of the surface roughness in hard turning process and the maximum compressive stresses in deep rolling empirical models based on D-optimal experimental design are used.

Abstract: Hot-working tools are frequently exposed to high cyclic temperature and mechanical loads, usually resulting in thermal fatigue cracking, which is observed as a network of fine cracks on the surface. The crack network degrades the performance of the tool and even invalidates it. Deep rolling is a surface strengthening treatment generally applied to improve the fatigue performance of metal components. But few attentions are paid on its influence on thermal fatigue cracking of the components, considering the relaxation of residual stresses and work hardening, which are deemed to mainly account for the improvement of fatigue performance. In this paper experiments were carried out to investigate the influence of deep rolling on thermal fatigue behavior of hot-work tool steel AISI H13. The experiment results show that deep rolling can improve the thermal fatigue behavior of AISI H13. To explore the mechanism of the effect, the changes of the residual stresses, the microhardness of the samples are also presented.