Surface Plastic Deformation Process Research Articles

Methodology and technological equipment development for treatment processes metal plastic flow research. Part 2. Special equipment and methodology development for experiment research by digital image correlation method

The metal plastic flow regularities experimental estimation, as well as the residual stresses (RS) values in the treatment processes is an important task to correctness justification of obtained finite element modeling solutions. However, the currently known and used plastic flow regularities and RS experimental determination methods in most cases have a significant disadvantages: labor intensity, low accuracy, sample preparation necessity and difficult to apply on real parts. This work purpose is to develop special equipment and methods for researches by the digital image correlation method for conducting experimental metal plastic flow and RS researches during free orthogonal cutting and surface plastic deformation (SPD) under the technological treatment factors variation. The paper substantiates orthogonal loading schemes in the metal plastic flow research in the cutting and SPD processes, research accessories and equipment is developed. The machine movement errors were determined, the sample sizes and loading routines were determined and justified. Using the digital image correlation method, the metal plastic flow experimental researches in the deformation zone during free orthogonal cutting and surface plastic deformation processes were performed. For experimental samples RS determinination after free orthogonal cutting and surface plastic deformation, the digital image correlation and probing hole drilling methods combination was used for the first time, which idea is to determine the material particles movements on the sample top from two images: the sample surface having residual stresses and the same surface after high-speed probing hole.

Pendulum surface plastic deformation of cylindrical blanks

The article discusses the features of kinematics of the working tool in form of circular sector during hardening by pendulum surface plastic deformation (SPD), which is carried out due to two successive processes – rolling and sliding in the contact zone of the deforming element with the blank. Forecasting of the possibility of its application for finishing and hardening processing of cylindrical parts such as shafts and axles is presented; the kinematic parameters of the pendulum SPD process in a rectangular coordinate system are described. Based on analysis of the components of motion types (rotational, translational, oscillatory) of the blank and tool, functions of the trajectory length, magnitude of the resulting velocity and acceleration were determined, which make it possible to control the technological parameters and modes of the pendulum SPD process. Reliability of the kinematic analysis is confirmed by the results of simulation with ANSYS 19.1 computer program. The results of dynamic modeling showed that under the same hardening conditions with a stationary position of the working tool and its opposite rotation with the blank, the intensity of temporary stresses increases by 10 % and 17 %, respectively, compared to the rolling scheme. With pendulum SPD, the intensity of temporary stresses increases sharply and reaches a maximum value (485 MPa), the distribution of which is uniform in comparison with other methods. In addition, regularity of the intensity distribution of temporary stresses over the cylinder depth is shown, where it is clear that in the case of SPD by sliding, the depth of plastic deformation h has a higher value compared to the SPD by rolling (by 1.5 – 2.3 times). Under the same hardening conditions, the highest value of the depth of the hardened zones is obtained with pendulum SPD (h = 2.8 mm), which leads to changes in the physical, mechanical and operational properties of the blank deeper surface layer.

Study on the Effects of Hydrostatic Pressure on the Structural State of Pure-Iron during Hardening Treatment with a Multiradius Roller

The study looks at features the formation of the structure of the surface layer of pure-iron after hardening treatment with surface plastic deformation (SPD) by a multiradius roller (MP-roller). Earlier authors with the help of the method of finite-element modelling (FEM) of the MP-roller SPD process proved the possibility of creating high hydrostatic pressure in the deformation center of the part being processed. The methods of optical (OM) and atomic-force microscopy (AFM) and X-ray structural analysis have determined that the MR-roller SPD results in the formation of an intensively deformed surface layer of the component with characteristic ferrite grains, stretched in the direction of the current of the metal and an average size of 20-30 μm. Analysis of the results of the X-ray structural analysis showed that the processing of the SPD by the MP-roller results in a significant increase in the microdistortion of the crystal lattice, which is characteristic of the nanodimensional structure. The data obtained are well consistent with the results of the finite element modelling previously obtained.

Modeling of the Contact Interaction of the Tool Indenter with the Part Surface when Processing by Surface Plastic Deformation Methods

There are results of studying the parameters of the indenter contact interaction with the surface when processing cylindrical parts made of 45 steel of different hardness by surface plastic deformation (SPD) methods with single-indenter elastic tools (diamond burnishing, ball burnishing). There were considered such characteristics as the resistance force when the indenter starts and in the steady state of SDP, the range of force fluctuations during processing, friction factor when the indenter starts and in the steady state, as well as some derivative coefficients. Adequate physical-statistical models for the quantitative estimation of the contact interaction parameters from SPD processing factors are obtained.

Numerical Study of Stress-Strain State of Workpiece in Contact Problem of Surface Mandrel Drilling

In recent years, the economic factor has played an increasingly important role in the selection of technologies for manufacturing machine parts with specified values of normalized parameters of geometric accuracy and quality of working surfaces. As applied to surface plastic deformation processes, this is noticeably manifested in the search for effective friction control methods in the “tool – workpiece” pair, which ultimately determines the distribution pattern and the magnitude of stresses and strains in the workpiece and the tool. It is not possible to obtain a rigorous analytical solution to the problem of establishing a connection between surface conditions, friction, and the stress-strain state of the contacted bodies. In this regard, the construction of mathematical models comes to the fore, the solution of which is possible by numerical methods. The paper presents the results of a numerical study (computational experiment) of a finite-element model of workpiece deformation under various conditions of contact interaction and friction by one of the methods of surface plastic deformation – surface mandrel drilling. The friction coefficient has been chosen as the criterion for assessing the conditions of contact interaction and friction. It is shown that a change in the friction coefficient in the process of surface mandrel has no noticeable effect on the formation of a stress field in the deformable workpiece both in the axial, and in the radial and circumferential directions. At the same time, with an increase in the value of the friction coefficient in the “tool – workpiece” pair and with the associated increase in the force of mechanical resistance to deformation of the workpiece, their growth is observed. A computational experiment has confirmed the presence of non-contact deformations of the workpiece and tool during surface mandrel drilling, as well as as a decrease in the value of residual deformations in the workpiece with a decrease in the coefficient of friction. Balance assessment of contact surface displacements in the workpiece (the inner surface of the hole to be machined) and the tool (mandrel) has shown that the deformations of the tool in the elastic region can lead to a significant decrease in the real tightness of surface mandrel drilling.

Optical properties of component surfaces processed by surface plastic deformation methods

It is suggested in this paper that parameters characterizing the reflectivity of machine component surfaces are used as indicators of surface quality. The research results of influencing technological factors of surface plastic deformation processing on these parameters are presented.

Improvement of Calibrated Steel Quality by Surface Deformation. Part 1: Determination of the Stress State of Cylindrical Parts during Orbital Surface Deformation

Cold-drawn calibrated steel is an effective workpiece for the manufacturing of low-stiff cylindrical parts such as shafts and axles. A high accuracy of the diametric size along the workpiece length, low surface roughness, and increased hardness and strength of the surface layer compared to hot rolled products allow the production of a variety of parts with high metal utilization and high machining performance. The main disadvantage of calibrated metal is the residual stresses that occur during pressure processing. To reduce or change the nature of the distribution over the cross section, we propose to use small plastic deformations in the product’s surface layer. Surface plastic deformation (SPD) methods known in practice usually lead to the curvature of non-rigid workpieces. To intensify the stress-strain state in the deformation zone, a method of orbital surface deformation is proposed. The orbital deformation scheme is a rod indenter (tool), one end of which is equipped with a ball tip that is in contact with the surface to be treated. The second end of the rod indenter rotates about the vertical axis, forming a conical surface in space with a certain angle at the apex. A deforming force acts along the rod axis. Based on the finite element modeling, we consider the effect of the main parameters of orbital surface deformation on the stress state in the deformation zone and residual stresses in the finished products. Compared with the traditional SPD process, the stress intensity during orbital surface deformation will increase by 10–15%. The residual compressive stresses formed in the surface layers reach 70–85% of the material tensile strength. The relative radius of the orbital rotation and the radius of the operating tool, at which the formation of maximal temporary and residual stresses is ensured, were established. At an increase in the frequency of the orbital rotation of the operating tool, the temporary and residual compressive stresses increase. In the second part of the paper, we provide information on a more effective method of surface deformation and on the change in initial residual stresses that are formed during the calibration of cylindrical rods.

INCREASING THE DURABILITY OF DETAILS TO WORK UNDER REPEATABLE LOADS

The article presents the results of the development of processes to improve the performance of parts operating under repeated variable loads, taking into account the reasonable parameters of surface plastic deformation (SPD) and cold gas-dynamic spraying of coatings. The influence on the parameters of the working surface layer, the nature of the distribution of the stress-strain state of the surface layer of material and residual compressive stresses, as well as the values of the used resource of plasticity of the surface layer of the workpiece, the parameters of the SPD process. The article shows that the main factor in the formation of residual compressive stresses during SPD is the decrease in the density of the surface layer of the workpiece, which is associated with the use of the plasticity resource. The model of calculation of the used resource of plasticity of material of preparation at SPD which allows to provide the improved quality of a surface layer of details is offered. A method of moving the workpiece layers with maximum hardening and residual compression stresses to the surface of the part by applying a deforming tool of reduced size in the following passes with coating the surface of the part with gas-dynamic spraying before SPD. Cold gas-dynamic coating by spraying, in contrast to most known gas-thermal coating methods that take place under significant temperature effects on the surface of the part, which is unacceptable for surfaces treated by SPD methods, provides a permissible temperature regime for creating special auxiliary coatings while preserving surface properties SPD. The technology of gas-dynamic coating by spraying includes heating the compressed gas (air), directing it into the nozzle and forming in this nozzle supersonic air-powder flow, sprayed material (copper, aluminum), acceleration of this powder material to supersonic speeds and directing it to the surface of the processed product. As a result, a special auxiliary coating (copper or aluminum) is formed on the surface of the product, which improves the parameters of the SPD process.

Application of the method of current functions in stationary plastic deformation processes

A method of determining the components of the strain rate tensor based on the method of current functions is developed. It is assumed that, with an axisymmetric plastic deformation of the metal in a channel with curvilinear borders, the kinematics of the process are similar to a flat flow. Using the incompressibility equation and the differential equation of the current lines, it is established that the current function maintains a constant value along the current lines. Two infinitely close current lines are considered in the flow plane to explain the kinematic content of the current function. The expression for flow through the finite transverse-sized tube was obtained. In the absence of radial velocity components at the boundaries, we obtain the restrictions imposed on derivatives of the current functions at these boundaries. The method of calculation of kinematic deformation characteristics for established axisymmetric processes will allow to simplify the mathematical processing of the obtained results. Real processes of metal processing are always accompanied by uneven plastic molding, which affects the power and kinematic parameters, the quality of finished products. The main technological factors affecting the appearance of the inhomogeneity and the nature of its distribution are the form factor (geometric parameters of the original workpiece) and the coefficient of contact friction. The study of technological parameters affecting the distribution of non-uniformity of plastic molding will allow to create practical recommendations for reducing the influence of the above mentioned parameters to ensure more uniform plastic deformation. Due to elastic-plastic deformation and local heating, which occur during surface-plastic deformation processing, the stress-strain and physical state of the surface layer is formed. This changes the microgeometry of the surface, the physical and mechanical properties of the surface layer of the workpiece. The surface treated by methods of surface-plastic deformation, has high hardness, residual compression stresses in the surface layer, smoothed out the micro-roughness. Accordingly, increases wear resistance, fatigue strength, resistance to corrosion and more.

INCREASING OF THE DURABILITY OF DETAILS WORKING UNDER REPEATABLE- LOADS

The article develops processes of increase the durability of parts operating under repeated loads, by justifying the parameters of surface plastic deformation (SPD) and cold gas-dynamic coating. The influence on the depth of the reinforced surface layer, the nature of the distribution of the stress-strain state of the material and residual compressive stresses, as well as the value of the used plasticity of the metal, the parameters of the SPD process. The hypothesis is substantiated that the main factor in the formation of residual compressive stresses during SPD is the decrease in metal density, which is associated with the use of the plasticity resource. The model of definition of the used resource of plasticity of metals at SPD is developed, that allows to provide qualitative characteristics of a surface layer of details. Methods for shifting the layer with maximum hardening and residual compressive stresses to the surface of the part by using a deformable tool of smaller dimensions in subsequent passes and gas-dynamic coating before SPD. The vast majority of traditional gas-thermal coating methods occur at significant temperature effects on the surface of the part, which is unacceptable for the surface treated by SPD methods. Cold gas-dynamic spraying provides an allowable temperature regime for the creation of special auxiliary coatings while maintaining the properties of the surface treated by SPD methods. The technology of gas-dynamic coating includes heating the compressed gas (air), feeding it into the nozzle and forming a supersonic air stream in this nozzle, introducing a powder material into this stream, accelerating this material in the nozzle by a supersonic air flow and directing it to the surface of the workpiece. As a result, a special auxiliary coating is formed on the surface of the product, which provides optimal parameters of the SPD process.

Development of design methodology of technological process of ball-rod hardening with account for formation of compressive residual stresses

Introduction . The study results on the multicontact shock-vibrating machining using a ball-rod hardener are presented. Methods of surface plastic deformation processing, their advantages are described. The tool circuit diagram is given. Features, technological advantages, and the application area of the ball-rod hardening are specified. Materials and Methods . When conducting theoretical studies on the processing, factors, which affect the quality of the surface layer of the machined parts, were established. Dependences are given for calculating the surface roughness, the hardened layer depth, and the deformation ratio under ball-rod hardening. While studying the generation of residual stresses, the dependence for calculating the residual stresses generated in the surface layer of the machined part was specified. Results . The experimental findings of the processing requisite for verification of the adequacy of the theoretical models, as well as the routine of the experiments, are presented. A table and graphs clearly confirming good convergence of the theoretical and experimental data are given (the difference does not exceed 20%). Residual stresses in the surface layer are compressive which enables to predict high performance properties of the machined parts. The value of residual stresses on the workpiece surface is in the range of 130÷200 MPa. The depth of compressive residual stresses is in the range of 0.9-1 mm. The fatigue characteristic variation, the ultimate stresses of the cycle in depth, which affects the endurance limit, is calculated. It has been established that the processing of workpieces by a ball-rod hardener provides increasing the ultimate cycle stress under repeated loading by 27-35%. Discussions and Conclusions . The design methodology of technological process of ball-rod hardening can be used under the development of production at the machine-building enterprises. In accordance with the recommendations, the limits of the required quality parameters of the workpiece surface layer are set; the parameters of the ball-rod hardener, the interference fit and the radius of rod sharpening are selected. Quality parameters of the surface layer are calculated. Correction of the selected modes and re-calculation of the parameters of the machined surface are carried out until all the specified characteristics are located within the required limits.

Study of Surface Layer Hardening after Treatment Complex Tool

The results of experimental studies of the thin surface layer of samples made of steel 45 after treatment with surface plastic deformation (SPD) multiradius roller (MR-roller) are presented. On the basis of the apparatus of the mechanics of technological inheritance, taking into account the effect of the solidified body, a model of the process according to the scheme of multiple loading-unloading of metal, taking into account the phenomenology of the SPD process and the properties of the material, is created. Distributions of parameters of the stress-strain state in the deformation centre are obtained, the parameters of roughness and microhardness of the surface layer are investigated.

The Metal Surface Layer Mechanical Condition Transformation in Machining Processes

The metal surface layer mechanical condition transformation at the product life cycle stages key provisions are presented. The described approach feature is the hardened body effect consideration: the metal mechanical properties changing during it displacement through the deformation zone space. On the basis of the developed for surface plastic deformation process hardened elastic-plastic body model, the cumulative shear strain level, plasticity reserve exhaustion level and residual stress tensor components calculations are performed. It is established that the greatest residual compressive stresses are characteristic for the axial component, and the extremum can be located both on the workpiece surface and at some distance from it. The metal hardening influence on the residual stresses distribution is revealed. On the axial (largest) component example shown that the difference between the maximum values is almost 30%. The obtained result corresponds to the idea that the hardened metal having an increased yield strength allows a larger residual stresses presence.

The Surface Layer Mechanical Condition and Residual Stress Forming Model in Surface Plastic Deformation Process with the Hardened Body Effect Consideration

The mechanical condition and residual stresses (RS) research and computational algorithms creation in complex types of loading on the product lifecycle stages relevance is shown. The mechanical state and RS forming finite element model at surface plastic deformation strengthening machining, including technological inheritance effect, is presented. A model feature is the production previous stages obtained transformation properties consideration, as well as these properties evolution during metal particles displacement through the deformation space in the present loading step.

Finite Element Modeling of Strengthening Process by Means of Surface Plastic Deformation Using a Multiradius Tool

New designs of deforming tools with a complex working profile, based on the mechanics of technological inheritance, have been developed. The finite element method modeling of the surface plastic deformation process by a multiradius roller was performed and possibility to accumulate large values of deformation without destroying the metal of the surface layer was shown.

Research of Tool Durability in Surface Plastic Deformation by Wide Burnishing of Cast Iron without Metalworking Fluids

The hyper productive surface plastic deformation processing technology called as wide burnishing (WB) was developed in Russian Federation. The mechanics of new WB technology is different from the classic SPD technologies (rolling or burnishing). For example applied force during processing of burnishing is 150-300 N, of WB is 2500-5000 N due to condition of process implementation in mass production with limited processing time (3-4 turnovers of workpiece). WB also has a high degree of deformation due to a multiple deformation passes. The purpose of the study was to determine the durability of a burnishing tool with the working surface made of the hard alloy with different dispersion. During the durability tests were tested VK6 alloy with the chemical composition of WC-94%, Co-6%, grain size of 2.1...3.4 micron (hardness HRA 88.5) and similar in chemical composition fine-grained hard alloy H10F (WC-90%, Co-10%) produced by Sandvik-MKTS with grain size of 0.5...0.9 micron (hardness HRA 92.1). Processing was conducted without lubricoolants. The acquired data presents that the roughness exceeds the tolerance during the processing by tool made of H10F alloy later than by tool made of VK6 alloy. At the same time increase of durability is from 60% to 80%.

Testing of External Cylindrical Surfaces of Car Parts after Wide Burnishing Processing

The hyper productive surface plastic deformation processing technology called as wide burnishing (WB) was developed in Russian Federation. The mechanics of new WB technology is different from the classic SPD technologies (rolling or burnishing). For example applied force during processing of burnishing is 150-300 N, of WB is 2500-5000 N due to condition of process implementation in mass production with limited processing time (3-4 turnovers of workpiece). WB also has a high degree of deformation due to a multiple deformation passes. The requirement to develop the methodology for testing “Gland neck parts of the car LADA processed by various methods” was caused by the fact that the previously carried out bench tests do not reproduce the real surface of necks shafts working in pair with lip seals. As well there was no methodology for measuring the value of the gland neck wear and the maximum value of the wear grooves was defined of 1.0 mm. Specimens reproducing gland neck in two of the most critical parts were tested: flange of cardan shaft mounting to the drive shaft of the gear box made of steel 40 and crankshaft made of high-strength cast iron 75-50-03 of LADA car. Test results of specimens made of steel 40 presented the surface roughness parameter Ra = 0.06 microns after burnishing and Ra = 0.28 microns after polishing. The test results were measured on profilograph and were obtained the following data: the width of the grooves wear was 936 microns with burnishing and 1152 microns with polishing, depth was 2.16 and 4.94 microns respectively. Size of cross-sectional area of specimen’s groove wear with burnishing - 1090 um2, with polishing - 2848 um2.

Technological Parameters Forming the Surface Texture in Hyper Productive Surface Plastic Deformation Processing

The hyper productive surface plastic deformation processing technology called as wide burnishing (WB) was developed in Russian Federation. The mechanics of new WB technology is different from the classic SPD technologies (rolling or burnishing). For example applied force during processing of burnishing is 150-300 N, of WB is 2500-5000 N due to condition of process implementation in mass production with limited processing time (3-4 turnovers of workpiece). WB also has a high degree of deformation due to a multiple deformation passes. To determine the optimal WB processing parameters single and double instrumental devices were implemented and tested. Specimens made of steel 40 and high-strength cast iron 75-50-03 were tested. Initial roughness of steel 40 specimen’s surface was Ra = 0.5 microns and high-strength cast iron was Ra = 0.85 microns. Results of surface texture parameters of processed parts such as surface roughness Ra of steel 40 and high-strength cast iron 75-50-03 under varying load values P and number of cycles (the number of workpieces revolutions during the period of burnishing) were acquired. It was established that the minimum Ra value of the processed surface correspond with values of P = 210 N/mm2 for steel 40 and P = 410 N/mm2 for high-strength cast iron 75-50-03 regardless of number of burnishing cycles. Plastic deformation mechanism (processing time and pressure on the surface) influences on the processed surface roughness formation. It is possible to assume that straining state forms at the optimal values of P in terms of achieving a minimum value of Ra in which the reached degree of hardening allows to minimize the height of the microscopic irregularities of the previous grinding processing. In this case there is no plastic flow of the metal surface layer.

Research of Tool Durability in Surface Plastic Deformation Processing by Burnishing of Steel Without Metalworking Fluids

Modern vector of development of machining technologies aimed at the transition to environmentally safe technologies - “green” technologies. The concept of “green technology” includes a set of signs of knowledge intended for practical use (“technology”). One of the ways to improve the quality of production is the use of surface plastic deformation (SPD) processing methods. The advantage of the SPD is a capability to combine effects of finishing and strengthening treatment. The SPD processing can replace operations: fine turning, grinding or polishing. The SPD is a forceful contact impact of indentor on workpiece’s surface in condition of their relative motion. It is difficult to implement the core technology of the SPD (burnishing, roller burnishing, etc.) while maintaining core technological advantages without the use of lubricating and cooling technology (metalworking fluids, MWF). The “green” SPD technology was developed by the authors for dry processing and has not such shortcomings. When processing with SPD without use of MWF requirements for tool’s durability is most significant, especially in the conditions of mass production. It is important to determine the period of durability of tool at the design stage of the technological process with the purpose of wastage preventing. This paper represents the results of durability research of natural and synthetic diamonds (polycrystalline diamond - ASPK) as well as precision of polycrystalline superabrasive tools made of dense boron nitride (DBN) during SPD processing without application of MWF.

Controlling Surface Chemistry to Deconvolute Corrosion Benefits Derived from SMAT Processing

Grain refinement through surface plastic deformation processes such as surface mechanical attrition treatment has shown measureable benefits for mechanical properties, but the impact on corrosion behavior has been inconsistent. Many factors obfuscate the particular corrosion mechanisms at work, including grain size, but also texture, processing contamination, and surface roughness. Many studies attempting to link corrosion and grain size have not been able to decouple these effects. Here we introduce a preprocessing step to mitigate the surface contamination effects that have been a concern in previous corrosion studies on plastically deformed surfaces; this allows comparison of corrosion behavior across grain sizes while controlling for texture and surface roughness. Potentiodynamic polarization in aqueous NaCl solution suggests that different corrosion mechanisms are responsible for samples prepared with the preprocessing step.