scholarly journals THE INFLUENCE OF HYDRO BLASTING ON THE EN-DURANCE LIMIT OF SPECIMENS WITH A CUT UNDER BENDING AND STRETCHING-COMPRESSION

2020 ◽  
Vol 6 (1) ◽  
pp. 25-34
Author(s):  
Valentin Fyodorovich Pavlov ◽  
Viktor Alekseevich Kirpichyov ◽  
Vladimir Stepanovich Vakulyuk ◽  
Vyacheslav Petrovich Sazanov ◽  
Pavel Anatol'evich Shlyapnikov
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Surface Hardening ◽  
Endurance Limit ◽  
Fatigue Tests ◽  
Critical Depth ◽  
Section Surface ◽  
Compressive Residual Stresses ◽  
Surface Layer Thickness ◽  
Dangerous Section

The hydro blasting influence on an endurance limit of cylindrical specimens with circular cuts of a semicircular  profile of 0,3 mm radius under bending and stretching-compression in a case of symmetric cycle has been examined. Specimens of 10 mm diameter for fatigue tests were made of steels 30ХГСА, 12Х18Н10Т, ЭИ961,45 and aluminum alloys В93, Д16Т.The influence of surface hardening on an endurance limit of specimens with cuts was valuated by two criteria: residual stresses on the concentrator surface and the average integral residual stresses calculated through the part’s dangerous section surface layer thickness equal the critical depth of a non-propagating fatigue crack. On results of residual stresses and specimens with cuts endurance limits determination it’s been stated that coefficients of surface hardening influence on an endurance limit increase under bending and stretching-compression by two criteria are approximately equal. Besides, the coefficient of the influence by the average integral residual stresses criterion changes within essentially lesser limits than the coefficient of the influence by the residual stresses on the concentrator surface criterion. So the average integral residual stresses criterion should be used for the evaluation of a surface hardening influence on an endurance limit of parts with concentrators.On an example of specimens within and without peening in a dangerous section it’s been shown that peening doesn’t influence the endurance limit of a surface hardened part. The compressive residual stresses only influence the endurance limit of these parts.

THE ESTIMATION OF ROLLER STRENGTHENING INFLUENCE ON THE ENDURANCE LIMIT OF SHAFTS WITH PRESSURIZED HUB

2020 ◽  
Vol 5 (4) ◽  
pp. 29-35
Author(s):  
Valentin Fyodorovich Pavlov ◽  
Vladimir Stepanovich Vakulyuk ◽  
Vyacheslav Petrovich Sazanov ◽  
Arsenij Vital'evich Efrosinin
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Endurance Limit ◽  
A Value ◽  
Surface Residual Stresses ◽  
Section Surface ◽  
Steel 20 ◽  
Compressive Residual Stresses ◽  
Surface Layer Thickness ◽  
Dangerous Section

The influence of roller strengthening on endurance limit under bending of the 25 mm and 50 mm diameter shafts made of steel 20 and 25 mm diameter shafts made of steel 40X with a pressurized hub has been examined. It’s been stated that the endurance limit of roller strengthened shafts with a pressurized hub depends not only on a value of compressive residual stresses in their dangerous section but on the character of its distribution. The valuation of a surface hardening influence on the endurance limit of shafts by the surface residual stresses criterion and the average integral residual stresses criterion has been shown that the average integral residual stresses criterion calculated through the part’s dangerous section surface layer thickness equal the critical depth of the non-propagating fatigue crack can be recommended for the hardened shafts with a pressurized hub endurance limit increase prediction. It’s been shown that on a diameter of a shaft with a pressurized hub raising it is necessary to increase a thickness of a hardened surface layer with compressive residual stresses.

scholarly journals Dependence of the limit endurance of specimens with notches from the depth of hardened surface layer

2018 ◽  
Vol 84 (8) ◽  
pp. 44-49
Author(s):  
V. S. Vakulyuk ◽  
V. K. Shadrin ◽  
N. A. Surgutanov
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Endurance Limit ◽  
Surface Plastic Deformation ◽  
Fatigue Tests ◽  
Surface Plastic ◽  
Outer Diameter ◽  
Notched Specimens ◽  
Compressive Residual Stresses ◽  
Dangerous Section

It is shown that, growth of the layer with compressive residual stresses at advanced surface plastic deformation of smooth samples leads to an increase in the endurance limit of the notched specimens due to an increase in the compressive residual stresses in their dangerous section. The study was conducted on the specimens with outer diameterDequal to 10 and 25 mm and on a 25 mm specimen with inner diameterd= 15 mm which were subjected to air shot blasting and roll-in. Residual stresses in smooth specimens were determined by the mechanical method. Circular incisions (R= 0.3 and 0.5 mm) were applied on hardened smooth samples with a shaped cutter. Residual stresses in notched specimens were determined by a numerical method calculating the redistribution of the residual stresses upon the incision. As the diameter of the samples increases with the same strengthening surface treatment,the depth of the layer with the compressive residual stresses increases due to an increase in the rigidity of the samples. The effect of surface hardening on the endurance limit of notched specimens was evaluated according to the criterion of the average integral residual stresses, which takes into account both the magnitude and completeness of the residual stresses. This criterion was calculated from the depth of the non-propagating fatigue crack that occurs in the surface layer in the dangerous section of the specimen during the fatigue test at the limit endurance. Fatigue tests are carried out in symmetrical cycle, the test base being 3 × 106cycles of loading. Estimation of the increment of the limit endurance of surface-hardened cylindrical specimens with semicircular notches gave the results acceptable for practice. The use of the proposed method can significantly reduce long-term and expensive fatigue tests.

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.

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.

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 Influence of Vibration and Heat Treatment on Residual Stress of a Machined 12%Cr-Steel

2014 ◽  
Vol 996 ◽  
pp. 609-614 ◽  
Author(s):  
Lin Peng Ru ◽  
Johan Moverare ◽  
Pajazit Avdovic ◽  
Annethe Billenius ◽  
Zhe Chen
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Surface Layer ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Thin Surface Layer ◽  
Microstructural Changes ◽  
Low Level ◽  
Stress Relieving ◽  
Compressive Residual Stresses

In this paper we investigated the influence of vibratory stress relieving technique, which is widely used for stress relaxation of weld and casting components/structure, on machining residual stresses in a ring-component of 12%Cr-steel. It was shown that the employed vibratory treatment, without significantly altering the microstructure, turned the surface layer from tension into compression but retained the compressive residual stresses in the subsurface. In comparison, a stress relieving heat treatment, included as a reference in the study, removed completely the surface tensile residual stresses and reduced the subsurface compressive residual stresses to a low level. Significant microstructural changes in the form of recrystallization also occurred in a thin surface layer of the machining affected zone after the heat treatment.

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