Metrological characterization of the thermomechanical influence of the cross-section of the undeformed chip on the surface properties in turning of the aluminum alloy EN AW-2017

2020 ◽  
Vol 87 (12) ◽  
pp. 777-786
Author(s):  
Thomas Junge ◽  
Thomas Mehner ◽  
Andreas Nestler ◽  
Andreas Schubert ◽  
Thomas Lampke
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Cross Section ◽  
Surface Integrity ◽  
Resultant Force ◽  
Mechanical Loads ◽  
Process Measurement ◽  
The Cross ◽  
Compressive Residual Stresses

AbstractThe surface integrity strongly affects the performance properties of parts. Therefore, it is of great importance to be able to measure and adjust the surface-layer properties during the manufacturing process. In particular, cutting operations are characterized by high mechanical loads and temperature gradients in the area of chip formation. To enable a targeted control of the surface-layer properties, a fundamental comprehension of the interrelationships between the thermomechanical impact and the thereby induced material modification is required. Hence, the subject of this study is to measure the thermomechanical changes during turning of the aluminium alloy EN AW-2017 and find correlations thereof to the surface integrity. In order to achieve a large variation of the thermal and mechanical loads, the feed f (0.04 mm to 0.2 mm) and the depth of cut {a_{\mathrm{p}}} (0.4 mm to 2 mm) are varied over a wide range. The cutting speed {v_{\mathrm{c}}} is kept constant (300 m/min). For the in-process measurement of the temperatures and contact conditions at the interface of the tool and the specimen, a tool-workpiece thermocouple is used. Additionally, the components of the resultant force are measured by a dynamometer. The characterization of the surface layer is performed by the measurement of the residual stresses using X-ray diffraction and supplemented by the determination of the geometrical properties of the machined surface using a stylus measurement instrument. The results show an increase in temperature and the components of the resultant force with the enlargement of the cross-section of the undeformed chip. Due to the temperature gradient, tensile residual stresses are introduced in the tangential direction of the surface layer. Compressive residual stresses occur only in the axial direction and can be correlated with the in-process measurement data by introducing the C-value. Consequently, the calculation of the presence of compressive residual stresses allows for a targeted control of the surface-layer properties during machining.

scholarly journals Thermal Effects on Surface and Subsurface Modifications in Laser-Combined Deep Rolling

2021 ◽  
Vol 5 (2) ◽  
pp. 55
Author(s):  
Robert Zmich ◽  
Daniel Meyer
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Thermal Loads ◽  
Deep Rolling ◽  
Mechanical Loads ◽  
Thermomechanical Process ◽  
Compressive Stresses ◽  
New Process ◽  
Negative Effect ◽  
Compressive Residual Stresses

Knowledge of the relationships between thermomechanical process loads and the resulting modifications in the surface layer enables targeted adjustments of the required surface integrity independent of the manufacturing process. In various processes with thermomechanical impact, thermal and mechanical loads act simultaneously and affect each other. Thus, the effects on the modifications are interdependent. To gain a better understanding of the interactions of the two loads, it is necessary to vary thermal and mechanical loads independently. A new process of laser-combined deep rolling can fulfil exactly this requirement. The presented findings demonstrate that thermal loads can support the generation of residual compressive stresses to a certain extent. If the thermal loads are increased further, this has a negative effect on the surface layer and the residual stresses are shifted in the direction of tension. The results show the optimum range of thermal loads to further increase the compressive residual stresses in the surface layer and allow to gain a better understanding of the interactions between thermal and mechanical loads.

scholarly journals Validation of Welding Simulations Using Thermal Strains Measured with DIC

2011 ◽  
Vol 70 ◽  
pp. 129-134 ◽  
Author(s):  
Maarten De Strycker ◽  
Pascal Lava ◽  
Wim Van Paepegem ◽  
Luc Schueremans ◽  
Dimitri Debruyne
Keyword(s):  
Residual Stresses ◽  
Cross Section ◽  
Circular Cross Section ◽  
Welding Process ◽  
Weld Bead ◽  
Image Correlation ◽  
Steel Tubes ◽  
Element Analysis ◽  
Strain Evolution ◽  
The Cross

Residual stresses can affect the performance of steel tubes in many ways and as a result their magnitude and distribution is of particular interest to many applications. Residual stresses in cold-rolled steel tubes mainly originate from the rolling of a flat plate into a circular cross section (involving plastic deformations) and the weld bead that closes the cross section (involving non-uniform heating and cooling). Focus in this contribution is on the longitudinal weld bead that closes the cross section. To reveal the residual stresses in the tubes under consideration, a finite element analysis (FEA) of the welding step in the production process is made. The FEA of the welding process is validated with the temperature evolution of the thermal simulation and the strain evolution for the mechanical part of the analysis. Several methods for measuring the strain evolution are available and in this contribution it is investigated if the Digital Image Correlation (DIC) technique can record the strain evolution during welding. It is shown that the strain evolution obtained with DIC is in agreement with that found by electrical resistance strain gauges. The results of these experimental measuring methods are compared with numerical results from a FEA of the welding process.

Surface Modification Analysis after Shot Peening of AA 7075 in Different States

2013 ◽  
Vol 768-769 ◽  
pp. 519-525 ◽  
Author(s):  
Sebastjan Žagar ◽  
Janez Grum
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Residual Stresses ◽  
Aluminium Alloy ◽  
Shot Peening ◽  
Fatigue Testing ◽  
Stress Profile ◽  
Treatment Conditions ◽  
Stress Profiles ◽  
Compressive Residual Stresses

The paper deals with the effect of different shot peening (SP) treatment conditions on the ENAW 7075-T651 aluminium alloy. Suitable residual stress profile increases the applicability and life cycle of mechanical parts, treated by shot peening. The objective of the research was to establish the optimal parameters of the shot peening treatment of the aluminium alloy in different precipitation hardened states with regard to residual stress profiles in dynamic loading. Main deformations and main residual stresses were calculated on the basis of electrical resistance. The resulting residual stress profiles reveal that stresses throughout the thin surface layer of all shot peened specimens are of compressive nature. The differences can be observed in the depth of shot peening and the profile of compressive residual stresses. Under all treatment conditions, the obtained maximum value of compressive residual stress ranges between -200 MPa and -300 MPa at a depth between 250 μm and 300 μm. Comparison of different temperature-hardened aluminium alloys shows that changes in the Almen intensity values have greater effect than coverage in the depth and profile of compressive residual stresses. Positive stress ratio of R=0.1 was selected. Wöhler curves were determined in the areas of maximum bending loads between 30 - 65 % of material's tensile strength, measured at thinner cross-sections of individual specimens. The results of material fatigue testing differ from the level of shot peening on the surface layer.

scholarly journals Selected Properties of the Surface Layer of C45 Steel Parts Subjected to Laser Cutting and Ball Burnishing

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3429 ◽  
Author(s):  
Agnieszka Skoczylas ◽  
Kazimierz Zaleski
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Laser Cutting ◽  
Experimental Studies ◽  
Hardened Layer ◽  
Ball Burnishing ◽  
Absolute Value ◽  
The Impact ◽  
Compressive Residual Stresses

In this article, we report the results of experimental studies on the impact of ball burnishing parameters on the roughness, microstructure and microhardness of the surface layer of laser-cut C45 steel parts. We also analysed the distribution of residual stresses generated in the surface layer of these parts. Laser-cut parts often require finishing to improve the quality of their surface. The tests performed in this study were aimed at assessing whether ball burnishing could be used as a finishing operation for parts of this type. Ball burnishing tests were performed on an FV-580a vertical machining centre using a mechanically controlled burnishing tool. The following parameters were varied during the ball burnishing tests: burnishing force Fn, path interval fw and the diameter of the burnishing ball dn. Ball burnishing of laser-cut C45 steel parts reduced the surface roughness parameters Sa and Sz by up to 60% in relation to the values obtained after laser cutting. Finish machining also led to the reorganization of the geometric structure of the surface, resulting in an increase in the absolute value of skewness Ssk. This was accompanied by an increment in microhardness (maximum microhardness increment was ΔHV = 95 HV0.05, and the thickness of the hardened layer was gh = 40 µm) and formation of compressive residual stresses in the surface layer.

Characterization of the Residual Stresses in Plastically Deformed Ferrite-Martensite Steels Using Barkhausen Noise Measurements

2005 ◽  
Vol 500-501 ◽  
pp. 655-662 ◽  
Author(s):  
Xavier Kleber ◽  
Aurélie Hug-Amalric ◽  
Jacques Merlin
Keyword(s):  
Plastic Deformation ◽  
Tensile Stress ◽  
Residual Stresses ◽  
Barkhausen Noise ◽  
Opposite Behavior ◽  
Noise Measurements ◽  
Two Phases ◽  
Noise Signature ◽  
Compressive Residual Stresses

In this work, we show that the measurement of the Barkhausen noise allows the residual stresses in each of the two phases of ferrite-martensite steels to be characterized. We have first studied the effect of a tensile and a compressive stress on the Barkhausen noise signature. We observed that for a ferrite-martensite steel, the application of a tensile stress increases the Barkhausen activity of the martensite and ferrite phases, whereas a compressive one reduces it. In a second time, we induced residual stresses by applying a plastic deformation to ferrite-martensite steels. After a tensile plastic deformation, we observed that (i) compressive residual stresses appear in ferrite, and (ii) tensile residual stresses appear in martensite. An opposite behavior is observed after a compressive plastic deformation. These results show that the Barkhausen noise measurement makes it possible to highlight in a nondestructive way the distribution of the stresses in each of the two phases of a ferrite-martensite steel. This result could be used to characterize industrial Dual- Phases steels that are plastically deformed during mechanical processes.

Numerical Simulation of Residual Stresses Induced from Shot Peening with Finite Element Method

2013 ◽  
Vol 433-435 ◽  
pp. 1898-1901
Author(s):  
Li Juan Cao ◽  
Shou Ju Li ◽  
Zi Chang Shangguan
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Residual Stress ◽  
Surface Layer ◽  
Residual Stresses ◽  
Shot Peening ◽  
Target Material ◽  
Residual Stress Field ◽  
State Of Stress ◽  
Compressive Residual Stresses

Shot peening is a manufacturing process intended to give components the final shape and to introduce a compressive residual state of stress inside the material in order to increase fatigue life. The modeling and simulation of the residual stress field resulting from the shot peening process are proposed. The behaviour of the peened target material is supposed to be elastic plastic with bilinear characteristics. The results demonstrated the surface layer affected by compressive residual stresses is very thin and the peak is located on the surface.

Analysis of Surface and Subsurface Layers after Shot Peening of Various Aluminium Alloys

2010 ◽  
Vol 89-91 ◽  
pp. 53-58
Author(s):  
Sebastjan Žagar ◽  
Janez Grum
Keyword(s):  
Surface Layer ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Surface Integrity ◽  
Shot Peening ◽  
Aluminium Alloys ◽  
Surface Hardening ◽  
Hardened Layer ◽  
Operating Pressure ◽  
Subsurface Layers

In the paper two aluminium alloys, i.e. 6082 and 7075, which were cold hardened by shot peening under different conditions, are treated. Surface hardening was carried out with S170 steel shot of the same diameter, particle hardness being 56 HRC. Other conditions were the operating pressure, mass flow, which provide different Almen intensities. The hardened layer was described by surface integrity. Macroscopic and microscopic analyses consisted in analyses of hardened profiles of hardness, and residual stresses in the thin surface layer. Research results indicated that there were significant differences among the characteristics chosen to describe surface integrity and that they had an important influence on the final condition of the surface layer. With too severe settings of the peening parameters, the surface properties got worse because of damages, which resulted in crack initiation and growth of the existing cracks.

scholarly journals ЩОДО ПИТАННЯ ПРО РАЦІОНАЛЬНУ ФОРМУ ПРЕСОВАНОГО БУЛЬБОКОСИНЦЯ

2020 ◽  
pp. 165-172
Author(s):  
А. Г. Дибир ◽  
А. А. Кирпикин ◽  
Н. И. Пекельный
Keyword(s):  
Service Life ◽  
Residual Stresses ◽  
Cross Section ◽  
Transverse Load ◽  
Shear Stresses ◽  
Cross Sectional ◽  
The Cross ◽  
Sectional Shape ◽  
Aircraft Panels ◽  
Better Than

In airplane building and helicopter engineering a bulb angle bar  an angle bar with a bulb at the end of a wall are widespread. They are better than a simple angle bar, since they have higher critical stresses under compression more than the proportionality limit. They are better than T bar, as T bar are fastened with two rows of rivets, which impairs tightness. Bulb angle bar are better than Z bar. The latter are higher, which reduces the structural height of the cross section and increases the load on the panel and usually have an excess cross-sectional area. Bulb angle bars are widely used in the structure of metal fuselages of airplanes and helicopters, in the tail boom of helicopters, in the wing and tail unit of light aircraft, in flaps, ailerons and rudders. However, modern the bulb angle bar have a significant drawback.When a bulb angle bar is loaded by a transverse load from the skin in the wing structure, tail unit, fuselage, except of normal stresses from bending of the stringer with attached skin, supported by ribs or frames, additional normal and shear torsional stresses arise. This torsion is caused by the fact that the lateral load is not applied at the center of the bend. Additional stresses reduce the service life and tightness of the structure in this place. An altered cross-sectional shape of the bulb is proposed for use in light aircraft panels to increase their strength and service life. The change in shape had a significant impact on the location of the center of the bend in the cross section. The determination of the position of the center of the bend in the balloncube was carried out using the Wagner model with walls not working for shear stresses. The modified cross-sectional shape of the bulbogon allowed to reduce the level of residual stresses after the panels were assembled, to rationally transfer the load from the casing to the stringer and to improve the technology of their assembly in the panels. It is recommended to drill holes for rivets in the stringer in the middle of the entire width of its shelf, taking into account the wall.A modified cross-sectional shape of a corner with bulb is proposed for use in light aircraft panels. The change in shape had a significant impact on the location of the center of the bend in the cross section. This made it possible to reduce the level of residual stresses after the assembly of the panels, to rationally transfer the load from the casing to the stringer and to improve the technology of their assembly.

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